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How to cite this thesis
Surname, Initial(s). (2012) Title of the thesis or dissertation. PhD. (Chemistry)/ M.Sc. (Physics)/ M.A. (Philosophy)/M.Com. (Finance) etc. [Unpublished]: University of Johannesburg. Retrieved from: https://ujdigispace.uj.ac.za (Accessed: Date).
WASTE TYRE MANAGEMENT TRENDS AND BATCH PYROLYSIS
FEASIBILITY STUDIES IN GAUTENG, SOUTH AFRICA
by
Nhlanhla P Nkosi
DISSERTATION
Submitted in fulfilment of the requirements of the degree
MASTER OF TECHNOLOGY
in
CHEMICAL ENGINEERING
in the
FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT
at the
UNIVERSITY OF JOHANNESBURG
SUPERVISORS: Prof. E Muzenda and Dr J.N. Zvimba
2014
ii
DECLARATION
I hereby declare that this dissertation, which I herewith submit in fulfilment of the
qualification
MASTER DEGREE IN CHEMICAL ENGINEERING
to the Department of Chemical Engineering, Faculty of Engineering and Built Environment
at the University of Johannesburg, is, apart from the recognised assistance from my
supervisors, my own work and has not previously been submitted by me to another institution
to obtain a diploma or degree.
_______________________________on this_________ day of June 2014
(Candidate)
_______________________________on this _________ day of June 2014
(Supervisor)
_______________________________on this _________ day of June 2014
(Co-Supervisor)
iii
ACKNOWLEDGEMENTS
The author would like to express her deepest appreciation to the supervisors Prof E.
Muzenda and Dr J.N. Zvimba for their dedication, encouragement and continuous
motivation. A greater part of this work would not have been possible without their support
and commitment.
I would like to thank the following sponsors for financial backing; National Research
Foundation (NRF), the Council of Scientific and Industrial Research (CSIR), UJ-Supervisor
linked and the UJ-Merit bursaries.
I would like to give thanks to the Chemical Engineering Technology Department for the
opportunity to conduct this work and for providing the required facilities, as well as the
University of Johannesburg‟s Postgraduate Centre for excellent administrative support.
I would also like to thank Mr J. Pilusa for giving insight about the research topic as well as
useful advice and guidance.
A special thanks to my waste to energy group members, J. Diphare and L. Ntaka for their
valued contribution and constant motivation.
My family and friends, my mother and Mrs S. Botha in particular, for financial and moral
support.
iv
RESEARCH OUTPUTS
Nhlanhla Nkosi, Edison Muzenda and John Zvimba “The Development of a Waste Tyre
Pyrolysis Production Plant Model in the Gauteng Region, South Africa” South African
Journal of Chemical Engineering, manuscript ID is SAJChE-2014-0019 (Submitted 11
August 2014).
Nhlanhla Nkosi and Edison Muzenda “A Review and Discussion of Waste Tyre Pyrolysis
and Derived Products” The International Conference of Manufacturing Engineering and
Engineering Management, London, United Kingdom July 2- 4, 2014, World Congress on
Engineering 2014, ISBN: 978-988-19252-7-5.
Nhlanhla Nkosi, Edison Muzenda and John Zvimba, “An Analysis of the Waste Tyre
Management Plans in South Africa” International Conference on Innovations in Engineering
and Technology, Bangkok, Thailand Dec 25-26, 2013, International Institute of Engineers
International Conference Proceedings, pp. 108-114 ISBN 978-93-82242-60-4.
Nhlanhla Nkosi, Edison Muzenda and John Zvimba “Using Tyre Derived Fuel: An Analysis
of the Benefits” International Conference on Emerging Trends in Engineering and
Technology, Phuket, Thailand Dec 7-8, 2013, International Institute of Engineers
International Conference Proceedings, pp 165-171. ISBN: 978-93-82242-52-9.
Nhlanhla Nkosi, Edison Muzenda and John Zvimba “The Current Waste Generation and
Management Trends in South Africa: A Review”, Chemical Technology, pp 6-12, October
2013.
Nhlanhla Nkosi, Edison Muzenda, John Zvimba and Jefrey Pilusa “The Current Waste
Generation and Management Trends in South Africa: A Review” International Conference on
Chemical, Industrial, Environmental, Mining and Metallurgy, Johannesburg, South Africa
April 15-16, 2013, In International Conference Proceedings of the Planetary Scientific
Research Centre, pp. 303 – 308, 2013, ISBN: 978-93-82242-26-0.
Nhlanhla Nkosi, Edison Muzenda, John Zvimba and Jefrey Pilusa “The Waste Tyre Problem
in South Africa: An Analysis of the REDISA Plan” International Conference on Chemical,
Industrial, Environmental, Mining and Metallurgy ,Johannesburg, South Africa April 15-16,
v
2013, International Conference Proceedings of the Planetary Scientific Research Centre, pp.
42 – 46, 2013, ISBN: 978-93-82242-26-0.
Nhlanhla Nkosi and Edison Muzenda “Waste Management Key Participants in Developing
Countries: A Discussion” International Conference on Chemical, Industrial, Environmental,
Mining and Metallurgy, Johannesburg, South Africa April 15-16, 2013, International
Conference Proceedings of the Planetary Scientific Research Centre, pp. 335 – 338, 2013,
ISBN: 978-93-82242-26-0.
Nhlanhla Nkosi and Edison Muzenda “Waste Management Participant: A South African
Perspective” International Conference on Chemical, Industrial, Environmental, Mining and
Metallurgy, Johannesburg, South Africa April 15-16, 2013, International Conference
Proceedings of the Planetary Scientific Research Centre, pp. 335 – 338, 2013, ISBN: 978-93-
82242-26-0.
NP Nkosi, P Mokoena,, E Muzenda, M Belaid "Organics –Biodiesel Systems Phase
Equilibrium Computation: Part 1" International Conference on Chemical, Biological, and
Environmental Sciences, Bangkok, Thailand, December 23 – 24, 2011, In International
Conference Proceedings of the Planetary Scientific Research Centre, pp. 371 – 375, 2011,
ISBN: 978-81-922428-3-5.
vi
ABSTRACT
Solid waste management is a growing environmental concern in developing countries such as
South Africa. Waste tyres fall under the general solid waste category give rise to land filling,
health and environmental challenges. As a result, majority of these waste tyres accumulate in
large quantities at landfill sites or end up being illegally disposed in open fields. Thus,
sustainable remedial technologies such as pyrolysis which are environmentally friendly must
be developed. Pyrolysis offers a number of attractive advantages as a treatment option such
as the production of primary and secondary economic valuable products, namely pyrolysis
gas, oil, char and steel wires.
The objective of this work was the development of a business model which includes costing,
procurement, installation, commissioning and operating a batch pyrolysis plant in Gauteng,
South Africa. In addition this work assesses the environmental, socio-economic aspects for
waste tyre derived products. The study objectives were achieved through literature research,
site visits, telephonic and personal interviews as well as questionnaires.
An order of magnitude costing method was used for the construction of the pyrolysis business
model. The model showed that it is possible to operate and sustain a batch pyrolysis plant
with a constant supply of waste tyres in the Gauteng region. This research has also shown
that a batch plant with a 12 year life span and a projected payback period of approximately 5
years can be operated. However, an initial capital incentive of R 10 173 075.00 is required
which includes the cost of all major equipment, plant assessment costs, building and
structure, engineering and construction and other costs such as contingency fees and office
utilities.
Four major income streams are expected to be core revenues for the business; the waste tyre
gate fee, tyre derived pyrolysis oil, carbon black and steel wire. Project evaluation methods
such as the Return on Investment (ROI), Return of Assets (ROA) and the Rate of Return
(ROR) were in strong agreement with those obtained from literature. In addition, the positive
net present value shows that the project is viable. However, a stable and well regulated
market should exist for the pyrolysis products.
vii
LIST OF TABLES
Table 2.1 Sources and types of general waste ........................................................................................................ 9
Table 2.2 Hazardous waste sub classes ................................................................................................................ 11
Table 2.3 Provincial waste contribution in South Africa, 2011 ............................................................................ 21
Table 2.4 REDISA tyre categories ....................................................................................................................... 24
Table 2.5 SATRP tyre categories ......................................................................................................................... 29
Table 2.6 Various applications for whole, cut, or shredded tyres ........................................................................ 30
Table 2.7 Various applications for crumbed rubber ............................................................................................. 31
Table 2.8 RMIO tyre categories ........................................................................................................................... 34
Table 2.9 2010 Global waste tyre treatment situation .......................................................................................... 39
Table 2.10 Benefit analysis of incineration .......................................................................................................... 46
Table 2.11 Waste to energy technologies ............................................................................................................. 50
Table 2.12 Composition of whole tyres ................................................................................................................ 56
Table 2.13 Comparison of incineration, gasification and pyrolysis ...................................................................... 57
Table 2.14 Pyrolysis gas constituents ................................................................................................................... 58
Table 2.15 Characteristics of vacuum pyrolysis waste tyre derived oil ................................................................ 62
Table 2.16 Elemental composition of oils obtained by vacuum pyrolysis of used tyres (wt. %) ........................ 63
Table 2.17 Waste tyre-derived pyrolytic oil impurities (ppb) .............................................................................. 63
Table 2.18 Surface area and elemental composition of pyrolytic carbon black and activated carbon black (wt%)
.............................................................................................................................................................................. 65
Table 2.19 Summary of waste tyre applications .................................................................................................. 67
Table 2.20 Ultimate analysis of pyrolysis gas ...................................................................................................... 67
Table 3.1 Questionnaire: Pyrolysis plant .............................................................................................................. 76
Table 3. 2 Questionnaire: Public/Community ...................................................................................................... 76
Table 3. 3 Questionnaire: Landfill sites ................................................................................................................ 77
Table 3.4 Questionnaire: Government/Local municipalities ............................................................................... 77
Table 4.1 Role of the informal sector in waste tyre management ......................................................................... 81
Table 4. 2 Main players in the South African waste sector ................................................................................. 85
Table 4.3 Mogale City waste disposal rates.......................................................................................................... 87
Table 4.4 Calorific values of a number of common fuels ..................................................................................... 92
Table 4.5 Pyrolysis oil specifications ................................................................................................................... 96
Table 4.6 Proximate analysis of crude and distilled pyrolysis .............................................................................. 97
Table 4.7 Pyrolysis carbon black specifications ................................................................................................... 98
viii
Table 5. 1 Effect of temperature on yield ........................................................................................................... 100
Table 5.2 Total plant energy requirement ........................................................................................................... 101
Table 5.3 Pyrolysis plant operational assumptions ............................................................................................. 102
Table 5.4 Process Input assumptions .................................................................................................................. 102
Table 5. 5 Mass and energy balance ................................................................................................................... 103
Table 5.6 Waste tyre pyrolysis project capex ..................................................................................................... 107
Table 5.7 Plant evaluation calculations .............................................................................................................. 108
Table 5.8 Business model option 1 ................................................................................................................... 1108
Table 5.8 Business model option 1 ..................................................................................................................... 108
ix
LIST OF FIGURES
Fig. 2.1 General and hazardous waste disposal [20] ............................................................................................ 12
Fig. 2.2 Provincial municipal waste contribution in South Africa, 2011 [7]. ...................................................... 13
Fig. 2.3 General waste composition, 2011 [7]. .................................................................................................... 13
Fig. 2.4 Recycling rates in South Africa, 2007 [27]. ........................................................................................... 15
Fig. 2.5 Recycling rates in South Africa, 2009 [27]. ........................................................................................... 16
Fig. 2.6 The waste cycle [29]. .............................................................................................................................. 18
Fig. 2.7 Waste Hierarchy, NWMS 1999 [31]. ..................................................................................................... 19
Fig. 2.8 Waste Hierarchy, NWMS 2010 [31]. ..................................................................................................... 19
Fig. 2.9 Waste Hierarchy, 2010 [31]. ................................................................................................................... 20
Fig. 2.10 Municipal general waste data in South Africa[7]. ................................................................................ 21
Fig. 2.11 REDISA waste tyre hierarchy [35] ....................................................................................................... 24
Fig. 2.12 The REDISA Waste Tyre Hierarchy [35]. ............................................................................................ 26
Fig. 2.13 REDISA initial cost allocations ............................................................................................................ 28
Fig. 2.14 SATRP waste tyre hierarchy [38] ......................................................................................................... 29
Fig. 2.15 SATRP Initial cost estimates ................................................................................................................ 33
Fig. 2.16 RMIO waste tyre hierarchy [40] ........................................................................................................... 34
Fig. 2.17 Technologies for managing scrap tyres[60] ......................................................................................... 44
Fig. 2.18 The scrap tyre incineration process[60] ................................................................................................ 46
Fig. 2.19 Scrap tyre gasification process[60]....................................................................................................... 48
Fig. 2.20 Primary energy supply in South Africa 1998-2009 [66] ...................................................................... 49
Fig. 2.21 Energy usage by sector 2006-2009 [66] ............................................................................................... 49
Fig. 2.22 Scrap tyre pyrolysis process[60] .......................................................................................................... 52
Fig. 2.23 Effect of feed size on product yield[8] ................................................................................................. 53
Fig. 2.24 Effect of temperature on product yield[8] ............................................................................................ 54
Fig. 2.25 Effect of residence time on product yield[8] ........................................................................................ 55
Fig. 2.26 Compositions of the gases obtained in tyre pyrolysis at different temperatures[68] ............................ 61
Fig. 2.27 Tyre pyrolysis conversion and products applications[72] .................................................................... 61
Fig. 2.28 Formation of polycyclic aromatic hydrocarbons in scrap tyre [2] ........................................................ 63
Fig. 2.29 Percentage distribution of energy types used in the transport sector in South Africa, 2010[85] .......... 70
Fig. 3.1 Project route map................................................................................................................................... 75
Fig 4.1 Waste streams in different communities [95] ........................................................................................... 79
Fig 5.1 Projected plant life, costs and revenues. ................................................................................................. 105
Fig 5.2 Net present value and depreciation rate .................................................................................................. 106
x
TABLE OF CONTENTS
DECLARATION ....................................................................................................................... ii
ACKNOWLEDGEMENTS ..................................................................................................... iii
RESEARCH OUTPUTS ........................................................................................................... iv
ABSTRACT .............................................................................................................................. vi
LIST OF TABLES ................................................................................................................... vii
LIST OF FIGURES .................................................................................................................. ix
TABLE OF CONTENTS ........................................................................................................... x
INTRODUCTION ..................................................................................................................... 1
1.1 Background and Motivation ........................................................................................ 2
1.2 Problem Statement ...................................................................................................... 2
1.3 Study Justification ....................................................................................................... 4
1.4 Aims and Objectives ................................................................................................... 4
1.5 Dissertation Layout ..................................................................................................... 5
LITERATURE REVIEW .......................................................................................................... 6
2.1 Introduction ...................................................................................................................... 7
2.2 Definition of Waste .......................................................................................................... 8
2.2.1 Waste classes ............................................................................................................. 8
2.2.2 Waste generation ..................................................................................................... 12
2.2.3 Waste management .................................................................................................. 14
2.3 The General Waste Hierarchy ........................................................................................ 18
2.3.1 Waste avoidance and reduction ............................................................................... 20
2.3.2 Recovery, re-use and recycling ............................................................................... 22
2.3.3 Treatment and disposal ............................................................................................ 22
2.3.4 Remediation ............................................................................................................. 22
2.4 The Proposed Integrated Waste Tyre Management Plans ............................................. 22
2.4.1 The REDISA plan .................................................................................................... 23
2.4.2 The SATRP plan ...................................................................................................... 29
2.4.3 Integrated Industry Waste Tyre Management Plan of The Retail Motor Industry
Organisation (IIWTMP-RMIO) ....................................................................................... 33
2.4.4 Analysis of the plans................................................................................................ 36
xi
2.5 Waste Tyre Disposal Alternatives .................................................................................. 37
2.5.1 Rubber ..................................................................................................................... 37
2.5.2 Material recovery ..................................................................................................... 40
2.5.3 De-vulcanization technologies ................................................................................ 41
2.5.4 Energy and material recovery .................................................................................. 44
2.5.5 Pyrolysis, Gasification and Liquefaction (PGL) Processes ..................................... 46
2.6 Product Markets ............................................................................................................. 69
2.6.1 Oil ............................................................................................................................ 69
2.6.2 Char .................................................................................................................... 71
2.6.3 Gas ........................................................................................................................... 71
2.6.4 Steel ......................................................................................................................... 72
2.7 Successes and Failures of Waste Tyre Pyrolysis ........................................................... 72
METHODOLOGY .................................................................................................................. 74
3.1 Project objectives: .......................................................................................................... 75
3.2 Research Methods .......................................................................................................... 75
3.2.1 Interviews ................................................................................................................ 75
3.2.2 Site visits.................................................................................................................. 76
3.2.3 Questionnaires ......................................................................................................... 76
3.2.4 Literature Analysis .................................................................................................. 77
3.2.5 Model Construction ................................................................................................. 77
GENERAL DISCUSSIONS .................................................................................................... 78
4.1 Role Played by Informal and Formal Sector in Waste Tyre Management .................... 79
4.1.1 Municipal Governments .......................................................................................... 79
4.1.2 The Informal Private Sector .................................................................................... 80
4.1.3 The Formal Private Sector ....................................................................................... 82
4.1.4 Community Based Organizations (CBOs) .............................................................. 83
4.1.5 Non-Governmental Organizations (NGOs) ............................................................. 83
4.1.6 Key issues and constrains ........................................................................................ 84
4.1.7 Informal and Formal Sector Integration .................................................................. 84
4.2 Socio-Economic Impact of Using Tyre Derived Products ............................................. 86
4.2.1 Land filling ban of waste tyres ................................................................................ 86
4.2.2 The environmental impact ....................................................................................... 88
4.2.3 Social impact ........................................................................................................... 88
xii
4.2.4 Economic impact ..................................................................................................... 89
4.2.5 Tyre Derived Fuel (TDF) applications .................................................................... 91
4.2.6 Waste tyre pyrolysis markets ................................................................................... 93
WASTE TYRE PLANT PYROLYSIS MODEL .................................................................... 99
5.1 Pyrolysis ....................................................................................................................... 100
5.1.1 Pyrolysis end products ........................................................................................... 100
5.1.2 Utilities .................................................................................................................. 101
5.2 Discussions ................................................................................................................... 101
5.3 Environmental Impact Assessment .............................................................................. 109
5.3.1 Air Emissions ........................................................................................................ 109
5.3.2 Liquid Residues ..................................................................................................... 110
5.3.3 Solid Waste Residues ............................................................................................ 111
5.4.1 Production .............................................................................................................. 111
5.4.2 End products .......................................................................................................... 111
5.4.3 Financial Requirements ......................................................................................... 112
CONCLUSION AND RECOMMENDATIONS .................................................................. 114
REFERENCES ...................................................................................................................... 116
APPENDICES ....................................................................................................................... 125
Appendix A ........................................................................................................................ 125
Appendix B ........................................................................................................................ 132
2
1.1 Background and Motivation
The use of automobile vehicles has become a daily essential for many households and
businesses globally[1, 2]. As a result, the disposal of waste vehicle tyres presents a major
environmental concern that requires immediate attention. Globally more than 330 million
tyres are discarded annually and accumulated over the years[2]. In 2003, Germany alone
generated 600,000 tons of waste tyres[3]. South Africa requires a plan to deal with its
growing „tyre mountain‟ problem, which is escalating at a rate of about 200 000 tons per
year, or one million waste tyres generated of which only 10% - 15 % is recycled[4]. Currently
2% of waste tyre processing takes place in three shredding plants in the country and a small
percentage is used as fuel[5]. A few other plants convert some waste tyres into mats,
playground equipment and protection pads[6]. Thus, there is a need to find alternative waste
tyre disposal methods. This has resulted in the release of the “Minimum Requirements for
Waste Disposal to Landfill”, “Waste Minimisation, Recycling and Treatment” by the
Department of Water Affairs in 1998. The South African Government has identified this
issue as a major area of environmental concern, resulting in the approval of an integrated
industry waste tyre management plan entitled the Recycling and Economic Development
Initiative of South Africa (REDISA) in accordance to the National Environmental
Management: Waste Act, 2008 (Act No. 59 of 2008) as stated in the Government Gazette, 17
April 2012, No.35147. This work focuses on socio-economic sustainable utilisation of waste
tyres. The objectives of this work is in line with the core environmental, social and economic
objectives for South Africa and the Gauteng Province in particular, namely: National Green
Economy Strategy (2010), Gauteng Economic Strategy, Gauteng Integrated Energy Strategy
(GIES, 2010), West Rand Green IQ (2011), Green strategy program for Gauteng (ECODEV,
2011) and most recently the REDISA Plan (2012).
1.2 Problem Statement
Scrap tyre present a major disposal problem in many developing and developed countries.
The same properties that make them desirable for use as automobile tyres in particular
durability also make them difficult to dispose of. Tyres are almost immune to biodegradation,
thus resulting in them being stockpiled in landfills or illegally dumped throughout the
country.
There is alarming increase of waste tyres being disposed in landfills in South Africa, which
were recorded to contribute 1% of the overall general waste composition during 2010 and
3
increasing [7]. Disposal site operators are no longer considering land filling as a viable
solution to harbour waste tyres, thus leading to the illegal dumping or burning of tyres. The
disposal of tyres is also becoming more expensive, while this trend is likely to continue as
landfill space becomes limited[8]. In this regard, the effect of such activities contribute
significantly to environmental challenges, both land and air. Noxious gases are produced
because of tyre burning for heat generation in rural areas; this activity is most common in low
income residential areas and informal settlements. Moreover, the use of worn out tyres sold at
cheaper rates cause severe road accidents due to un-roadworthiness and tyre failure. Tyres
take up large amounts of valuable space and also provide breeding sites for mosquitoes and
rodents[9], causing diseases that threaten human health. Fire hazards in large stockpiles could
consequently cause uncontrollable burning and air pollution where large amounts of thick
black smoke containing carcinogens are emitted into the atmosphere[10]. Such fires are
difficult to control because of the high flammability of tyres and the presence of air available
in the piles.
Over the years, alternative waste management options for tyre recycling such as re-treading,
reclaiming, grinding and crumbing have been implemented to produce rubber for other
applications such as carpets, sports surfaces and children‟s playgrounds[7]. However, all
these have significant drawbacks and limitations[9]. The South African Government is in the
process of implementing new laws and legislation to protect the environment and to consider
greener techniques for the treatment and disposal of waste tyres.
In this regard, alternative waste management options such as tyre pyrolysis are currently
receiving renewed attention[1, 3, 9]. Pyrolysis is the thermal degradation of waste matter in
the absence of oxygen. Pyrolysis has a number of attractive advantages as a treatment option.
Tyre pyrolytic oils have been found to have a high calorific value of approximately 41–44 MJ
kg, which would encourage their use as replacements for conventional liquid fuels[2]. In
addition, tyre derived oil can be used directly as fuel or blended to petroleum refinery feed
stocks. The derived gases are also useful as fuel and the char may be used as carbon black or
activated carbon[2]. Moreover, previous studies on the combustion of oil derived from batch
pyrolysis of waste tyres found the oil to have similar properties to diesel[3].
Due to non-compliance with environmental legislation and the unregulated product market,
several pyrolysis plants have been shut down in South Africa[11]. To date none of the
4
operating plants are addressing the national concerns relating to environmental and socio-
economic sustainability. The pyrolysis processes currently used to treat waste tyres do not
generate high quality primary products that are ecologically friendly and the market for these
products is not regulated and monitored. Secondary products such as high-grade carbon black
and activated carbon may also be obtained by integrating a further purification stage into the
pyrolysis process[2]. The current plant design and operations are not addressing issues
around sustainable job creation, energy and poverty reduction while protecting the
environment and public health. There is need for a detailed investigation for the most cost
effective and environmentally sustainable waste tyre pyrolysis plant that will produce high
quality products with minimal environmental impacts. There is also need to develop and
support the sustainable management of waste tyres for use in recycling and for energy
generation.
1.3 Study Justification
Waste tyres become a burden to deal with after they have reached their life span, thus a
majority of developed countries, such as European Union countries, have put a ban on the
land filling of waste tyres. Currently implemented strategies have proven to be limited and
unsuccessful due to the lack of integration between the private sector tyre manufacturers and
the public sector national waste management departments. Developing countries, such as
South Africa, are faced with an increasing mountain of waste tyres which can be utilised as a
source of fuel. The country is currently experiencing energy shortages and supply, thus
initiatives such as the conversion of waste tyres to energy and material recovery are desired.
1.4 Aims and Objectives
This work covers the feasibility of construction and operating a batch waste tyres pyrolysis
pilot plant in Gauteng. It also demonstrates the possibility of producing high quality fuel from
automotive waste tyres via a process of thermal decomposition. A preliminary study on
quantitative analysis and transport logistics of waste tyres was carried out to evaluate its fit
into the pyrolysis model. Other waste tyres processing technologies such as gasification are
explored and compared to pyrolysis. The study mainly focused on:
Environmental and economic impact of using waste tyre derived oil and carbon black
as alternative green fuels.
Market analysis of waste tyre pyrolysis products.
5
Development of business model including costing, procurement, installation,
commissioning and the operation of a pyrolysis plant.
Analysing the role played by informal and formal sector in waste tyre collection and
recycling.
Assessment of the socio-economic and market opportunities associated with energy
recovery from pyrolysis of waste tyres.
1.5 Dissertation Layout
Chapter 1 outlines the motivation of the study, as well as aims and objectives of the study.
Chapter 2 reviews literature and discusses the various waste tyre management strategies.
Chapter 3 outlines the approaches and procedures followed to achieve the study objectives.
Chapter 4 gives general discussions.
Chapter 5 presents pyrolysis plant design, construction and operation.
Chapter 6 Conclusions and recommendations are presented.
7
2.1 Introduction
In generic terms, waste can be defined as “an unavoidable by-product of most human
activity”[12]. Economic development and rising living standards have increased the quantity
and complexity of generated waste. Moreover, industrial diversification and the provision of
expanded health-care facilities have added substantial quantities of industrial hazardous and
high risk health care waste into the waste stream with potentially severe environmental and
human health consequences. There are two fundamental waste classes, namely, general waste
(municipal waste) and hazardous waste (health care risk waste and certain industrial waste).
Waste tyres fall under the general waste category which gives rise to land filling, health and
environmental challenges.
Developing countries, including South Africa, are faced with major challenges concerning
waste tyre disposal, these include: (i) tyre stockpiles provide breeding ground for mosquitoes
and vermin, this in turn, causes serious diseases, thus affecting human health, (ii) fire hazards
in large stockpiles that could consequently cause uncontrollable burning and air pollution,
(iii) the current „„conservation of natural resource concept‟‟, namely the reuse (retread) first,
then reuse of rubber prior to disposal, does not accommodate the increased dumping of tyres,
(iv) due to the high cost of legal disposal for tyres, illegal dumping may increase, (v) disposal
of tyres is becoming more expensive and this trend is likely to continue as landfill space
becomes more scarce. Tyres, also classed as polymers, are non-biodegradable solid waste
because of their complex mixture of very different materials, which include several rubbers,
carbon black, steel cord and other organic and inorganic components. Land filling has been
one of the conventional methods used for waste tyre disposal, but it requires large quantities
of airspace as tyres cannot be compacted[6].
Alternatively, recycling of solid waste to a useful product can be a sustainable approach with
future prospects, particularly the pyrolysis process. Waste tyres can be thermally pyrolyzed to
produce oil, gas, and char. Despite the success of the process, there are still challenges or
drawbacks. Environmental protection is a significant factor that must be taken into account
when considering the pyrolysis process. The gases released during the process are not
environmentally friendly if released into the atmosphere. Thus, stringent atmospheric
protection standards must be adhered to in order to minimize the health and environmental
challenges pyrolytic gases pose. Lastly, the final products, either primary or secondary must
be uncontaminated and marketable and must prove to be viable and profitable.
8
2.2 Definition of Waste
According to the Government Gazette, 24 August 1990[13], waste is defined as an
undesirable or superfluous by-product, emission, residue or remainder of any process or
activity, any matter, gaseous, liquid or solid or any combination thereof, which
is discarded by any person,
is accumulated and stored by any person with the purpose of eventually discarding it
with or without prior treatment connected with the discarding thereof,
is stored by any person with the purpose of recycling, re-using or extracting a usable
product from such matter.
2.2.1 Waste classes
Waste classification systems are vastly documented in South Africa; these include waste
regulations and laws such as the minimum requirements for the handling, classification and
disposal of general and hazardous waste[14] as well as the waste classification and
management regulations, which is in accordance with the Waste Act (Act No. 59, 2008)[15].
Some of the laws that have been amended on this act include, Act No. 73 of 1989
(Environmental Conservation Act, 1989) whereby certain sections have been amended or
repealed as well as the repulsion of sections 8 and 9 of the environmental conservation
amendment Act, 1992 (Act No. 79 of 1992).
The waste classification system is based on the concept of risk[14]. It is accepted that there is
no waste that is truly "non-hazardous", since nothing is entirely safe or ideally non-
hazardous. No matter how remote the risk posed to man and the environment by a particular
waste, it nonetheless exists. However, it is possible to assess the severity of the risk, and to
make informed decisions on that basis. The classification system therefore distinguishes
between waste of extreme hazard, which requires the utmost precaution during disposal, and
waste of limited risk, requiring less attention during disposal. Thus waste is divided into two
main classes, namely general and hazardous waste, which are further sub classified into
smaller categories. General waste is sub classified into domestic, industrial and institutional
waste, while hazardous waste is further classified into explosives, flammable liquids and
solids as well as corrosives. The waste classification system is in accordance with the risk
waste poses; hence, general waste poses little risk to the environment while hazardous waste
poses significant risk. For waste to be properly managed, its properties and its risk potential
must be fully understood.
9
2.2.1.1 General Waste
General waste does not pose a significant threat to public health or the environment if
properly managed [14]. Examples would include domestic, commercial, certain industrial
wastes and builder's rubble. General waste may be disposed of at any duly authorized waste
disposal facility permitted in terms of the Environment Conservation Act (73 of 1989).
Domestic waste is classified as general waste even though it may contain hazardous
components. This is because the quantities and qualities of hazardous substances in domestic
waste are sufficiently minor to be a potential risk. In addition, the Minimum Requirements
for Waste Disposal by Landfill require leachate control at certain general waste disposal sites.
Table 2.1
Sources and types of general waste
Source Typical waste generator Types of solid wastes
Residential Single and multifamily dwellings Food wastes, paper, cardboard,
plastics, textiles, leather, yard wastes,
wood, glass, metals, ashes, special
wastes (e.g. bulky items, consumer
electronics, white goods, batteries,
oil, tyres) and household hazardous
wastes
Industrial Light and heavy manufacturing, Housekeeping wastes, packaging, food
fabrication, construction sites, wastes, construction and demolition
power and chemical plants materials, hazardous wastes, ashes and
special wastes
Commercial Stores, hotels, restaurants, markets, Paper, cardboard, plastics, wood, food
office buildings, etc. wastes, glass, metals, special wastes
hazardous wastes and tyres
Institutional Schools, hospitals, prisons, government Same as commercial
centres
Construction and demolition New construction sites, road repair, Wood, steel, concrete, dirt, etc.
renovation sites, demolition of buildings
2.2.1.2 Hazardous Waste
Hazardous waste is defined as waste that has the potential, even in low concentrations, to
have a significant adverse effect on public health and the environment because of its inherent
toxicological, chemical and physical characteristics[14]. Hazardous waste requires stringent
10
control and management, to prevent harm or damage and hence liabilities. It may only be
disposed of on hazardous waste landfills (Section 3, Minimum Requirements for Waste
Disposal by Landfill)[14]. Hazardous waste can further be classified by its hazardous rating
which simply differentiates between a hazardous waste that is moderately hazardous and one
that is extremely hazardous. The 9 sub classes of hazardous waste as listed in Table 2.2 are
classified and treated under the South African Bureau of Standards (SABS) Code 0228,
namely, the identification and classification of dangerous goods and substances. Applying the
precautionary principle, waste must always be regarded as hazardous where there is any
doubt about the potential danger of the waste stream to human beings or the environment.
Waste management in South Africa is regulated by legislation such as the National
Environmental Management Act, 1998 (Act 107 of 1998), Environment Conservation Act
(Act 73 of 1989) Section 20, National Water Act (Act 36 of 1998), Health Act (Act 63 of
1977), Air Quality Act (Act 39 of 2004), Hazardous Substances Act (Act 15 of 1973),
Nuclear Energy Act (Act 131 of 1993) Section 45 & 46 Authority, Medicines and Related
Substances Act, 1965 (Act 101 of 1965) Section 27, and the Occupational Health and Safety
Act (Act 85 of 1993).
The definition and regulation of waste has been redefined and amended over the past years in
South Africa. However, the Environmental Conservation Act (ECA) was the first piece of
legislation formally regulating waste management in South Africa. The ECA came into
operation on the 9th
of June 1989 and underwent many amendments, and it was later repealed
in its entirety, save for a few provisions by National Environmental Management Waste Act
(NEMWA)[16]. The significant changes that were made in the ECA which are now catered
for by the NEMWA, 1998 (Act No. 107 of 1998) where the redefining and addition of
important terms, the provision for temporary waste storage and other waste related aspects
that came into effect after 1997 are included. Many large industries in South Africa dispose
of industrial waste on-site, but since this hazardous waste does not enter the formal waste
stream, there is also often little reported data available[17].
11
Table 2.2
Hazardous waste sub classes
Class No. Class type
Class 1 Explosives
Class 2 Gases
Class 3 Flammable liquids
Class 4 Flammable solids
Class 5 Oxidising substances and organic peroxides
Class 6 Toxic and infectious substances
Class 7 Radioactive substances
Class 8 Corrosives
Class 9 Other miscellaneous substances.
This regulatory system includes:
The issuing of waste disposal site permits.
A manifest system for the transportation of hazardous waste.
The registration of hazardous waste generators and transporters.
The aim is to protect the environment (Environment is used in the holistic sense and includes
cultural, social, soil, biotic, atmospheric, surface and ground water aspect) and the public
from the harmful effects of unsafe waste disposal practices. Before a waste disposal site
permit is issued, minimum procedures, actions and information is required from the permit
applicant. These are termed "Minimum Requirements". The minimum requirements provide
the applicable waste management standards or specifications that must be met in the absence
of any valid motivation to the contrary. They also provide a point of departure against which
environmentally acceptable waste disposal practices can be distinguished from
environmentally unacceptable waste disposal practices.
The objectives of setting minimum requirements are to[14]:
Prevent water pollution and ensure sustained fitness for use of South Africa's water
resources.
Attain and maintain minimum waste management standards in South Africa, so as to
protect human health and the environment from possible harmful effects caused by
the handling, treatment, storage and disposal of waste.
12
Effectively administer and provide a systematic and nationally uniform approach to
the waste disposal process.
Endeavour to make South African waste management practices internationally
acceptable.
2.2.2 Waste generation
Over 42 million cubic metres of general waste is generated every year in South Africa, with
Gauteng Province contributing 42%[18]. In addition, more than 5 million cubic metres of
hazardous waste is produced yearly, mostly in Mpumalanga and KwaZulu-Natal. This is a
result of the concentration of mining activities and fertilizer production in the two provinces.
The average amount of waste generated per person per day in South Africa is 0.9 kg[7]. This
is closer to the average waste produced in developed countries (0.73 kg in the UK and 0.87
kg in Singapore), compared to the average in developing countries such as 0.3 kg in
Nepal[18]. By far the biggest contributor to the solid waste stream is mining waste (72.3%),
followed by pulverized fuel ash (6.7%), agricultural waste (6.1%), urban waste (4.5%) and
sewage sludge (3.6%) [19].
Fig. 2.1 General and hazardous waste disposal [20]
South Africa has been implementing the “end on pipe” approach in the management of solid
waste, including waste tyres. Disposal at landfills has been the most predominantly utilized
method; hence the main focus was on acquiring land space for landfilling. According to the
South African Waste Information Centre (SAWIC) data bank which was established in 2004,
waste disposal has been increasing since then due to the betterment of the living standards for
most South Africans, thus resulting in an increased number of disposal sites. Domestic
0,00E+00
2,00E+06
4,00E+06
6,00E+06
8,00E+06
1,00E+07
1,20E+07
2004 2005 2006 2007 2008 2009 2010 2011 2012
To
nn
es
Total General Hazardous
13
environmental laws of most countries, including South Africa, have been profoundly
influenced by international laws. Most environmental problems transcend political
boundaries and global trends as well as pressures have driven the development of national
laws. In South Africa, environmental assessment was practised on a voluntary basis since the
early 1980s, but become part of legislation because of the incorporation of an environmental
right in the Bill of Rights[21]. As a result countries such as South Africa adopted new waste
reduction management strategies and systems. Fig. 2.1 shows annual waste generation from
2004 to 2012 obtained from the SAWIC databank.
Fig. 2.2 Provincial municipal waste contribution in South Africa, 2011 [7].
Fig. 2.3 General waste composition, 2011 [7].
.
0%
10%
20%
30%
40%
50%
Wa
ste
gen
era
ted
as
%o
f to
tal
wa
ste
Province
Non-
recyclables
municipal waste; 34%
Contruction and
demolition
waste; 21%
Metal waste;
14%
Organic waste;
13%
Paper; 7%
Plastic;
6%
Glass; 4% Tyres; 1%
14
Fig. 2.2 shows the provincial waste contribution in 2011 and the general waste composition is
shown in Fig 2.3. Gauteng, the economic hub of South Africa with a population of 11.3 x 106
in 2011[22] contributes 42% to the waste stream. Fiehn & Ball (2005)[23] suggested a
current growth rate envelope of between 2-3% per annum from a starting tonnage of ±15m
t/a, while DEAT (2012) suggested a generation rate of 1.57%[17].
Waste tyres made up 1% of landfilled general waste in 2011[17], Fig 2.3. The disposal of
waste tyres at landfill sites is environmentally unfavourable compared relatively to their size
as well their health and environmental implications, accompanied by low recycling and
alternative treatment rates in South Africa. As a result they are often illegally dumped or
burnt to recover steel for recycling. In 2009, regulations were promulgated requiring tyre
producers and importers to develop an integrated industry waste plan for waste tyre
management and funding.
2.2.3 Waste management
This section centers on the current waste management practices in urban communities. Plans
such as the integrated waste management plan and the national waste management strategy
exist for the economical and safe management of waste produced by urban communities. If
left uncontrolled, not only will there be an aesthetic problem, but also pose health risks. This
can be aggravated by the presence of hazardous material in the waste stream. Thus waste
must be collected from all sources as efficiently as possible, and disposed of in controlled
disposal facilities[24]. Various options are available for the treatment of either whole general
waste or of materials separated from it for recovery/recycling or pre-treatment prior to
disposal. After waste prevention and re-use, the waste management hierarchy accords the
highest preference to recycling over energy recovery and other disposal options.
2.2.3.1 Mobilisation
A common feature among the waste management options is the need for collection, sorting,
processing and transportation from source to the waste treatment or disposal facilities and
markets for recovered materials. A formal waste collection system was first established
around 1786 though the utilization of animal-drawn carts until the use of mechanical
transportation took over in the1920‟s. This transition brought about significant cost savings
as well as the advantage of easier supervision[25]. Waste collection and transportation has
had to be critically thought out in South Africa to accommodate rapid urbanization,
population growth, improvements in community health demands as well as better service.
15
The best approach for South Africa is to be able to integrate existing and new technological
systems to maximize economic advantage[25]. The same approach is also required for waste
tyre management, a reliable and well managed collection and transportation system. For
simplicity and easy management, a single national plan is the preferred approach.
2.2.3.2 Recycling
Rapid economic growth in South Africa‟s developed commercial and industrial areas,
particularly in the larger cities, reflects an increasing demand on the individual‟s life style
and leisure preferences. These demands have changed consumption needs resulting in
increased discarded goods and packaging material. Recycling diverts components of the
waste stream for reuse. The success of recycling is largely dependent on the market
availability for both the raw and re-manufactured products. Economically, recycled products
should be priced at a rate that covers the cost of their recovery less any subsidies. The price
commanded by recycled materials is highly dependent on their quality. Clean, well-sorted
and contaminant-free secondary material attracts a higher price than mixed, low quality or
sordid material. Low quality recycled products have no market and must be disposed of at a
cost[26]. Figs. 2.4 and 2.5 show the recycling rates for common general waste in 2007 and
2009 respectively. Generally, there is an increase in recyclable material from 2007 to 2009,
with the exception of beverage cans. This can be attributed to environmental awareness and
recycling initiatives by both private and public sectors. On the contrary, the recycling of
beverage cans dropped slightly during that period, and this might have been attributed to the
recession that was experienced in South Africa during the first quarter of 2009. This resulted
in big cooperate companies not being able to properly fund and sustain their environmental
initiatives and projects.
Fig. 2.4 Recycling rates in South Africa, 2007 [27].
70%
54,50%
25%
22% Metal beverages cans
Paper
Glass
Plastic
16
Fig. 2.5 Recycling rates in South Africa, 2009 [27].
Numerous waste tyre processing plants are in operation across South Africa. The plants
which are currently in operation are involved in the shredding, granulation and pulverising of
waste tyres which found use in various applications. South Africa requires technologies
which can process waste tyres with job creation potential with also the ability to reduce the
health and environmental risks. Some of the waste tyre companies and initiatives in South
Africa are: (a) The East Rand-based Vredestein SA Recycling Company found in the 1950s
and was burnt down in 2008. The facility produced rubber-chip products sold to a leading
international manufacturer of artificial grass systems for pitches and sports fields. Waste steel
and nylon flock were also reclaimed and sold to other recyclers[28]. (b) Innovative Recycling
converted waste rubber and plastic to fuel. The products were steel wire, oil and carbon black
and these were sold to scrap metal traders, transport companies and the ink and paint
industry. The plant closed down due to its failure to meet environmental standards. (c) South
African (SA) Tyre Recyclers, formed in late 2005 in Atlantis, Cape Town, to steer South
Africa's newest and most advanced technology in tyre recycling. The company works closely
with local authorities and government in waste tyre recycling and other waste tyre
environmental related matters. Scrap tyres are processed into a range of rubber granules and
fine powders. Rubber products produced are shreds (used in matting, sport surfaces, turf and
playgrounds); granules and chips (used in athletic tracks, playgrounds, horse arenas and
asphalt); crumbs and powders (used in new tyres, brake pads, road sealing, adhesives and
paints); and large shred tyre chips (used in civil engineering and fuel derivatives).
69%
56%
32%
26% Metal beverage cans
Paper
Glass
Plastic
17
2.2.3.3 Land filling
Land filling involves the managed disposal of waste on engineered sites with little or no pre-
treatment. Thus, landfilling is different from dumping which is characterized by the absence
of design, construction, control of the disposal operations and management of dump sites.
Land filling is the most common, cheapest and cost-effective method of disposing
waste[29].Waste dumping still occurs in less-developed communities in South Africa but this
is gradually declining[26]. The volume and content of the waste to be disposed of will dictate
the size and classification of the landfill, and necessary requirements for licensing purposes.
Some of the major problems associated with landfilling include (i) wind dispersing debris (ii)
rodent, insect and bird infestation (sometimes disease-carrying) (iii) pollution of ground and
surface water (iv) spontaneous combustion hazard, and (v) foul odours. Nation-wide, there
are over 2 000 waste handling facilities, of which 530 are permitted, yet only four of the nine
provinces have hazardous waste facilities[30]. There is an undersupply of landfill airspace,
and the currently available airspace is being rapidly depleted. This is propelled by the low
levels of waste minimization and reuse, recovery and recycling[30].Landfill sites are not
allowed to accept waste tyres into their sites in line with the proposed REDISA plan.
2.2.3.4 Incineration
The demand for land and the need to protect the limited groundwater resources in South
Africa dictates that alternative solutions to landfilling need to be explored. Incineration as an
alternative has been considered as a waste management strategy with the potential to
minimize waste volumes. The purpose of thermal treatment of waste (which in the narrow
sense usually means combustion in incinerators) is to reduce waste bulkiness before disposal
as inert inorganic ash residue. Modern incinerators are designed to recover the energy from
waste combustion supplementing electricity and/or heat from other sources[26]. In this
regard, waste tyres can also be utilised in the same manner. Large-scale incineration, such as
waste tyre incineration, is capital-intensive, but has the advantage of; (i) reducing the volume
of waste requiring landfilling (ii) combating the spread of disease (iii) providing a potential
energy source.
2.2.3.5 Pyrolysis and gasification
Along with the combustion technology outlined in section 2.2.3.4, there is increasing interest
in the advanced thermal conversion technologies of pyrolysis and gasification. These
technologies differ from combustion in that the waste is first heated either in the absence of
air or with a very restricted quantity of air. Organic matter is thermally broken down to give a
18
mixture of gaseous and/or liquid products that are then used as secondary fuels. The
secondary fuels are used to provide heat input for the process, thus promoting process self-
sustainability. The pyrolysis processes also produce solid coke residues which may be used as
a coal substitute. Fig. 2.6 shows the schematic waste cycle. Pyrolysis and gasification are
possible waste tyre remedial methods, and can yield the same products but at varying ratios.
Fig. 2.6 The waste cycle [29].
2.3 The General Waste Hierarchy
The conceptual approach to waste management is underpinned in the waste hierarchy, which
was introduced into South African waste management policy through the White Paper on
Integrated Pollution and Waste Management[17]. It was a hallmark of the 1999 National
Waste Management Strategy (NWMS)[14], as represented in Fig. 2.7, with Fig. 2.8
representing the amended 2011 waste hierarchy. The essence of the approach is to group
waste management measures across the entire value chain in a series of steps, which are
applied in order of priority. The foundation of the hierarchy, and the first choice of the
measures in the management of waste, is waste avoidance and reduction. Where waste cannot
be avoided, it should be recovered, reused, recycled and treated. Waste should only be
disposed of as a last resort.
19
Fig. 2.7 Waste Hierarchy, NWMS 1999 [31].
Fig. 2.8 Waste Hierarchy, NWMS 2010 [31].
The Waste Act provides the legal mandate for the successful implementation of the waste
hierarchy, through the provision of additional measures for the remediation of contaminated
land to protect human health and secure the wellbeing of the environment. Implementation of
the waste hierarchy promotes extended producer responsibility with respect to the design,
composition or production of a product and packaging. These requirements include clean
product measures, the composition and volume of packaging to be restricted as well as the
responsibility of the producer to ensure that packaging be designed in such a way that it can
be reduced, re-used, recycled or recovered[15], thus giving effect to the concept of „cradle-to-
cradle‟ waste management. This is an important advance from the previous “cradle to grave”
approach, which mainly took into account producer responsibility for the entire lifecycle of a
product until its final disposal. Cradle to cradle management ensures that once a product
reaches the end of its life span, its component parts are recovered, reused or recycled, thereby
Disposal
Treatment
Recovery, Re-Use and Recycle
Waste avoidance and Reduction
Waste avoidance and Reduction
Re-Use
Recycle
Recovery
Treatment and Dosposal
20
becoming inputs for new products and materials and this cycle repeats itself until the least
possible portion of the original product is eventually disposed as shown in Fig. 2.9.
Fig. 2.9 Waste Hierarchy, 2010 [31].
2.3.1 Waste avoidance and reduction
Waste avoidance and reduction is the foundation of the waste hierarchy and is the most
preferred waste management option. The aim of waste avoidance and reduction is to achieve
waste minimization and thus reducing the amount of waste entering the waste stream. This is
particularly relevant for waste streams where recycling, recovery, treatment or disposal of the
waste is problematic. While waste minimization is difficult to quantify, available figures
indicate that waste generation across all provinces has been on the rise per kilogram per year,
as supported by the 2011 figures and prior, Fig. 2.10 and Table 2.3[16]. Waste minimisation
occurs largely as a result of competitive pressures, economic incentives, and through
producer responsibility initiatives implemented by industries. To date the most notable of the
national government initiatives with respect to waste minimization has been the plastic bag
levy initiative. The agreement came into effect on the 9th
of May 2003, accompanied by a
standardization of the following bag sizes 8-litres, 12-litres and 24-litres, with the 24-litres
dominating retail markets[30]. Knowler[32] reported that plastic bag consumption
significantly dropped from 90% to 70%, when the fee was first introduced at a rate of 46 cent
per bag in 2003. However, due to pressure from plastic bag manufacturing industries the rate
has decreased by 44% in 2005[33]. A survey carried out by one of the major retail
supermarkets reported that, due to the lower price of plastic bags, majority of people tend to
Remediation
Disposal
Treatment and processing
Recovery, Re-Use and Recycle
Waste avoidance and Reduction
21
not reuse the plastic bags for shopping purposes as was intended by the acts. Consumers
might also perceive the carrying of plastic bags for shopping as an inconvenience, leading to
the absorption of the price of plastic bags into consumer‟s grocery list because of their low
price. Nevertheless, the plastic bag levy has slightly decreased the consumption of plastic
bags in South Africa. This is a tax instrument being used to effect change in behavior at both
consumer and industry level. Furthermore, there is also a proposed levy for the management
of end of life tyres entering the waste stream.
Table 2.3
Provincial waste contribution in South Africa, 2011
Province Kg/capital/Annum Waste generated as % of total waste Waste tyre generation (tonnes)
Western Cape 675 20 47428,60
Eastern Cape 113 4 9485,72
Northern Cape 547 3 7114,29
Free State 199 3 7114,29
KwaZulu Natal 158 9 21342,87
North West 68 1 2371,73
Gauteng 761 45 106714,35
Mpumalanga 518 10 23714,30
Limpopo 103 3 7114,29
237143,00
Fig. 2.10 Municipal general waste data in South Africa[7].
22
2.3.2 Recovery, re-use and recycling
Recovery, re-use and recycling are the second step in the waste hierarchy. These are very
different physical processes, but have the same aim of reclaiming material from the waste
stream and reducing the volume of waste generated that moves up the waste hierarchy.
Recycling rates in South Africa are relatively well established, Figs 2.4 and 2.5. These are
primarily driven by industry-led, voluntary initiatives with funds managed independently of
government via non-profit organizations, which oversee the recovery or recycling processes
and facilities.
2.3.3 Treatment and disposal
Section 2 (a) (iv) of the Waste Act clearly indicates that the treatment and disposal of waste is
a “last resort” within the hierarchy of waste management measures. In terms of waste
treatment and processing, the Department of Environmental Affairs (DEA) supports the
development of alternatives to land filling such as incineration, gasification, and
pyrolysis[27] of general waste and waste tyres. While there are cost implications for the
adaptation of the incineration process as a waste processing technology, the option requires
attention considering the rising costs of landfilling. It is anticipated that appropriate
incineration, gasification and pyrolysis facilities as well as other alternative technologies will
increase over time and ultimately replacing landfills as the primary waste disposal
mechanism[27].
2.3.4 Remediation
Remediation is the final step in the waste hierarchy. There is a lack of data on the number and
extent of contaminated sites (which include un- managed waste dumps) in South Africa due
to the various mining activities in the country plus the historical under-regulation of such
areas.
2.4 The Proposed Integrated Waste Tyre Management Plans
South Africa is considered as one of the fastest growing economies and the economic growth
is realised through the bulk industrial production of goods to meet the socio-economic needs
of a growing population. Over 200 000 tonnes of tyres become waste tyres in South Africa
annually. About 11 million used tyres are dumped illegally or burnt to retrieve steel wire.
With this figure estimated to increase by around 9.5 % annually, clearly the country is facing
a serious waste tyre problem[34].
23
The Department of Environmental affairs is tasked with protecting the environment and
public health. The Waste Management Act[15] declares its objectives as being to protect
human health and well-being as well as the environment. This Act, in Section 28(1),
addresses waste management options for waste that occurs in more than one province. The
Act anticipate the need to address national issues with a holistic national plan, hence the plans
had to be drafted taking cognisance of this. The Department promulgated Waste Tyre
regulations that took effect on the 30th
of June 2009, compelling tyre producers to register
with the Minister of Water and Environmental Affairs, but only three plans passed the initial
screening stages, namely: The South African Tyre Recycling Programme (SATRP) which
initially submitted its first draft in June 2009, The Retail Motor Industry Association
(RMIA), 21 December 2011 and The Recycling and Economic Development Initiative of
South Africa (REDISA plan), 19 April 2010. The REDISA plan was later approved and
gazetted for implementation on the 30th
of November 2012.
2.4.1 The REDISA plan
The REDISA plan has been accepted in accordance with the National Environmental
Management Waste Act, 2008 (Act No. 59 of 2008) as stated in the Government Gazette, 17
April 2012, No.35147. REDISA, registered as REDISA NPC (2010/022733/08) is a non-
profit making organization representing various people and organizations in the tyre and
waste tyre industry.
All tyre assortments that are imported or manufactured, including locally retreaded tyres, will
reach the end of their useful life and become waste tyres need to be managed. According to
REDISA, the annual projection of the quantities and types of tyres that are manufactured or
imported will be managed through the Integrated Industry Waste Management Plan. For the
ease of waste tyre management, tyres will be divided into nine categories as listed in Table
2.4.
24
Table 2.4
REDISA tyre categories
Table Category Type of tyre
1 Passenger tyres
2 Light commercial tyres
3 Heavy commercial tyres
4 Agricultural tyres
5 Motorcycle tyres
6 Industrial tyres
7 Aircraft tyres
8 Earth moving tyres
9 Any other pneumatic tyres
2.4.1.1 Waste tyre hierarchy
Similar to the general waste hierarchy[27], waste reduction and avoidance form the
foundation of the REDISA waste tyre hierarchy. It is followed by recycling, re-use and
recovery as the last option, Fig. 2.11.
Waste Tyre Avoidance and Reduction: Priority will as required in terms of regulation 7 (1) of
the Waste Tyre Regulations of 2009 to be directed to re-treading plants[35].
Re-use: Retreading of high performance tyres is a common practice in Europe[35], but rarely
practised in South Africa, due to the lack of funding associated with the establishment of
suitable plants and also because of consumer and dealer preconceived ideas.
Fig. 2.11 REDISA waste tyre hierarchy [35]
Recycling: Many recycling processes require significant capital investment, which in turn
necessitates assured long-term supply of the raw material to enable them to recoup the
investment. As a result, one of the most vital roles of the REDISA Plan is to manage the flow
and supply of tyres to recycling operations to ensure sustainability of those facilities.
The plan will promote and support the establishment of recycling facilities nationwide. These
facilities create employment opportunities for the informal sector and previously
25
disadvantaged individuals in both urban and rural communities. The collection of waste tyres
to the depots and/or tyre processors will be the main source of job creation and the
establishment of small businesses[36].
Applications to produce industrial and consumer products include sport surfaces, indoor
safety flooring, playground surfaces, shipping container liners, conveyor belts, automobile
mats, footwear, carpet underlay, roof tiles, flooring and activated carbon[37].
27
2.4.1.2 The Plan in a nutshell
The basis of the REDISA Plan centres on the following fundamental aspects:
Job creation: Attaching a value per kilogram to waste tyres provides small entrepreneurs and
the previously disadvantaged with opportunities to earn income by delivering tyres to 150
depots throughout South Africa. REDISA aims to specifically identify micro operators,
provide the relevant training and create business opportunities by awarding specific
collection points, thereby ensuring sustainability.
Small Medium-Micro Enterprises (SMMEs) and Broad-Based Black Economic Empowerment
(BBBEE): One of the biggest hurdles faced by SMMEs is access to capital. Establishment of
depots requires funding that the SMMEs do not generally have access to. Under the REDISA
plan which addresses the entire industry, depots will initially be funded by REDISA and
leased to BBBEE entrepreneurs. This has the secondary advantage that should a depot fail
through mismanagement it becomes easier to re-start operation with new management.
Managers of these depots can over time, as they themselves become fully self-sustaining,
take over full ownership of their depots.
Need for informal participation: Tyre manufacturers and importers must shoulder the
primary responsibility for waste management. In practice, it is the tyre dealers who handle
waste tyres through their life cycle, hence the management approach must fit in with the
practicalities of the retail industry through the integration of both entities. The informal sector
deals with a large proportion of the waste tyre, estimated to be at least 75%[35]. Thus,
without informal sector participation no plan will succeed, hence the plan must be inclusive
of this sector.
Fairness: A single plan approach, with a simple and equitable system for apportioning the
waste tyre management fee will simplify administration and auditing. As a result, the plan
will be far less open to behind the scenes manipulation by the influential participants.
Finance and audit control: The management of waste tyres on a national scale is a massive
task involving very large sums of money, thus proper financial management is essential.
There are approximately 2300 tyre dealerships nationally[35], and hence the scale of
potential problems is huge, as would be the remedial cost.
28
Training and communication: The REDISA Plan will provide various training programmes
in order to equip all stakeholders with the relevant skills and competencies. Similarly, there
will be a need to market the concept of waste tyre recycling and encouraging participation. A
single plan with consolidated funding is not only more effective, but the message is simpler
and can easily be communicated.
Resilience and longevity: There are many other sources of environmental waste which can be
dealt with in the same manner, such as electric goods, small appliance batteries, compact
fluorescent lights and many other forms of waste. This can contribute towards a fund to cater
for safe recycling and disposal of these goods[35].
Fig. 2.13 REDISA initial cost allocations
The waste tyre management fee levied by REDISA on the subscribers will be calculated to
recover the cost of the waste tyre management process. The fee will be levied on both
produced and imported tyres. The Plan will raise funds from the levied fee of R2.30 per
kilogram (kg) and the fee will be reviewed annually to meet demands. The cost is calculated
taking into account the initial cost allocations, Fig. 2.13. From a research point of view, for
R2.30/ Kg
Transportation 38%=
88c/Kg Depots 19.5%=
43c/Kg
Admin
20%= 46c/Kg
Recyclers/ce-ment kilns
13.5%=
31c/Kg
Research & Development 2.5%=6c/Kg
Training 1%=3c/Kg
Marketing 2%=5c/Kg
Social upliftment
3.5%=
8c/Kg
29
the early implementation stages of the Plan, the 2.5% allocated should be sufficient. As the
plan develops and grows, unconventional primary and secondary products will be discovered
through research and development initiatives in the long run.
2.4.2 The SATRP plan
In response to the Waste Tyre Regulations, 2009, the South African Tyre Recycling Plan
(SATRP) Company (Company registration no: 2002/027503/08) prepared its Integrated
Industry Waste Tyre Management Plan, the “SATRP Company Industry Plan”. The plan was
aimed at solving the waste tyre problem in South Africa, creation of jobs for previously
disadvantaged individuals (PDIs) and the establishment of Small Micro Enterprises (SMEs).
Table 2.5
SATRP tyre categories
Category Type of tyre
1 Passenger car tyres
2 Commercial vehicle tyres
3 Agricultural equipment tyres
4 Motorcycle tyres
5 Industrial and lift truck tyres
6 Earthmoving equipment tyres
7 Aircraft tyres
8 Other pneumatic tyres
The SATRP plan addresses the waste tyre problem in the same manner as the REDISA plan
as shown in Table 2.5.
2.4.2.1 Waste Tyre Hierarchy
Fig. 2.14 SATRP waste tyre hierarchy [38].
30
Waste Tyre Avoidance and Reduction: Priority will be given to preventing and reducing
waste tyre generation through the launching of awareness campaigns on maintenance and
producers guidelines. Secondly, the SATRP plan will encourage investment in the retreading
industry and actively promote the use of retreaded tyres. Used tyres classified as retreadable
by tyre dealers as required in terms of regulation 7 (1) of the Waste Tyre Regulations of 2009
to be directed to retreading plants[15].
Re-use: The re-use of a product is defined in the Waste Act, 2008[39] as “utilising articles
from the waste stream again for a similar or different purpose without changing the form or
properties of the articles”. The re-use of waste tyres is defined as “the utilisation of waste
tyres, in whole or in part, without changing the composition of the waste tyre”. The
Guidelines list the applications for whole, cut or shredded tyres as well as crumble rubber,
Table 2.6 and 2.7 [38].
Table 2.6
Various applications for whole, cut, or shredded tyres
Application Material
Source Method
Whole tyre Cut tyre Shred Chip
Embankments x
x x PW, TW, MW M, A
Erosion control x x x x PW, TW M, A
Landfill engineering x
x x PW, TW M, A
Slope stabilization x
x x PW, TW M, A
Temporary roads x
x x PW, TW M, A
Thermal insulation x
x x PW, TW, MW M, A
Collision barriers x x x x All M, A
Light weight fill x
x x PW, TW, MW A
Noise barriers x x x x PW, TW, MW M, A
Train and tram train beds x PW,TW M, A, C
Key for Table 2.6
Sources Technology (size reduction)
PW Whole passenger tyres
M
Mechanical (cut, compress)
TW Whole truck tyres
C
Cryogenic size reduction
MW Mixed whole car/truck tyres A
Ambient size reduction
ALL All
Recycling: Table 2.7 shows some or the recycling technologies for crumbed rubber which are
considered in the SATRAP plan.
Recovery: currently, there are very few energy recovery initiatives from waste tyres in South
Africa, such as cement, lime or steel production and power stations. The authorization of the
31
use of waste tyres as a substitute for fossil fuel is done on a plant by plant basis according to
the existing provisions of the Waste Act, 2008 and the Department of Environmental Affairs
(DEA) National Policy on thermal treatment of general and hazardous Waste
Table 2.7
Various applications for crumbed rubber
Application Material Technology
G P B R
Concrete construction additives
P
Asphalt additives
x
P, D
Asphalt rubber x x
A, C
road furniture x x
x A, C, R, D
Keys to Table 2.7
Material Source Technology
G-Granulate PW-Whole passenger tyres C-Cyrogenic size reduction
P-Powder TW-Whole truck tyres A-Ambient size reduction
B-Buffings MW-Mixed whole car/truck tryes D-Devulcanization
R-Reclaim ALL All
R-Reclaim
D-Devulcanizates P-Pyrolysis
Y-Pyrolytic products
Z-Upgrade material
2.4.2.2 The plan in a nutshell
Job creation: The job creation potential of the SATRP Company Industry Plan, over the 5
year period of implementing the plan is forecast to be in: (i) new tyre dealers, (ii) waste tyre
transportation, (iii) waste tyre transfer sites, (iv) Waste tyre processing. The potential
contribution of the SATRP Company Industry Plan to the green economy is therefore
forecast at 5000 informal jobs transformed to formal jobs; 5060 PDIs new jobs created; 1500
SMMEs created; and 335 SMEs created[38].
Training and development: The SATRP Company will develop training programmes for
informal tyre dealers to enable them to provide an upgraded service to their customers.
Included is the provision of (i) fully equipped workshops; (ii) training in the use of the
equipment provided; (iii) training in general business management and finance (iv) support in
stock control and supply (v) business skills for SMEs.
32
Previously disadvantaged individuals (pdi’s): Individuals presently employed in the informal
second-hand tyre trade will be incorporated into the formal market by means of a training
programme and the provision of tools and equipment and the forming of SMMEs. The
SATRP Company will, together with professional organisations, launch a programme to train
the present roadside and township informal tyre dealers to become recognised as part of the
formal tyre industry.
Auditing: The SATRP Company will appoint external auditors for a period of three (3) years
through a tender process.
Research and development: The SATRP Company intends working closely with its
international partner in the area of research and development. Matters currently under
research are; road surface treatment, concrete composite and odours. Products presently being
developed are: fibres for reinforcing road coating materials, thermoplastic compounds,
acoustic screens and textile fibres used as fuel[38]. The SATRP Company plans to approach
the Council for Scientific and Industrial Research (CSIR) as well as the Department of
Science and Technology to specifically consider issues of the South African environment.
The rate to be charged to subscribers to the SATRP Company Plan will be R1.98/Kg,
resulting in a cost estimation of R487 million during the first year of operation[38]. It is
estimated that 30 transfer sites will be required to store and pre-process the waste tyres
collected from tyres dealers and the legacy stockpiles.
Based on Fig. 2.15, it is evident that the SATRP Company will prioritise its plan mainly on
instituting a well routed and reliable waste tyre transportation system as well as properly
established transfer sites. Only 1.3% of the total cost will be allocated for research and
development. This percentage might need to be revised in order to have a growing
technological plan. Research and development is essential for the integration of new and old
waste tyre treatment technologies.
33
Fig. 2.15 SATRP Initial cost estimates
2.4.3 Integrated Industry Waste Tyre Management Plan of The Retail Motor Industry
Organisation (IIWTMP-RMIO)
In accordance with the Waste Tyre Regulations, the purpose of this plan is to facilitate and
manage the disposal of waste tyres in accordance with the Waste Tyre Act of 2009. Research
done by the RMI show that, majority of fitment centres has entrepreneurs collecting their
scrap tyres. In some instances these tyre collectors have been involved in doing so for 3
generations[40]. The RMI further supports the implementation of a collaborative integrated
Waste Tyre Management Plan that includes all stakeholders within the tyre industry. This
level of involvement will ensure sustainability of a new industry, given their expert industry
experience. Tyres shown in Table 2.8 will become waste tyres and will be managed through
the integrated industry waste management plan:
R1.98/kg
Research & Development
= 1.3%
Transport contractors
= 44%
Transfer sites
= 24.5%
Waste tyre processors = 14.6%
Abatement of stockpiles
= 5%
Social &Training
= 4%
Marketing =3%
Administration
=3.5%
34
Table 2.8
RMIO tyre categories
Category Type of tyre
1 Passenger vehicle tyres
2 Commercial vehicle tyres
3 Agricultural equipment tyres
4 Motorcycle tyres
5 Construction and earthmoving equipment tyres
6 Pedal cycle tyres
7 Aircraft tyres
8 Other diverse tyres
2.4.3.1 Waste Tyre Hierarchy
The Parties to the Plan intend implementing the tyre hierarchy in the following manner as
presented in Fig. 2.16.
Fig. 2.16 RMIO waste tyre hierarchy [40]
Reuse: The Retail Motor Industry Organisation (RMIO) recognises reusing of waste tyres as
their main priority in the waste tyre hierarchy; this is fundamentally identified as retreading.
Recycle: Mechanical shredding and crumbing are the preferred methods of recycling as well
as reclaiming. Crumbing activities render tyre waste as suitable raw material for many
processes such as moulded rubber products, road surface and many others. Crumbing is also a
precursor for reclaimed rubber. The latter is exportable and used in small quantities in many
rubber formulations for a variety of moulded and extruded products. The Plan will also
actively promote and support the establishment of recycling facilities throughout the country.
35
Incineration: Incineration will be facilitated through processes such as pyrolysis as well as
energy recovery for power generation advocacy. The pyrolysis products obtained are fuel
oils, char/carbon black and steel from waste tyres. These value added products are saleable
and a source of sustainable income. Energy recovery from waste tyres can be beneficial to
South Africa in order to reduce the carbon footprint that coal currently imposes in South
Africa.
Export: Export is preferred to landfill, illegal dumping and burning disposal. It has the benefit
that waste tyre volumes in excess of recycling and other requirements are disposed of in a
more environmentally friendly manner. Furthermore the process of preparing waste for
export to be used for steam generation can create jobs.
Landfilling: Landfilling is the last resort in the waste tyre hierarchy; it is undesirable and
should be avoided.
2.4.3.2 The plan in a nutshell
The potential number of waste sites is estimated at about fifty countrywide. Sites may vary in
size depending on the geographical location and the consumer concentration as well as waste
generators.
National awareness: The RMI currently actively promotes awareness in relation to the
management of waste tyres in various advertising mediums, including national and regional
media, in their monthly magazines and monthly newsletters, and as well as at national and
regional meetings/road shows. Funding will also be made available for consumer awareness
programs.
Job creation: The plan provides for on-going monitoring of job creation in the various
processes. Preferences will be given to the lower income earners and previously
disadvantaged, whilst not excluding the existing industry.
Training and development: The fund will establish a full training committee to deal with
training and skills development matters throughout the value chain. The approach of the
parties to the plan is to develop their candidates into independent businessmen who will
compete in local markets and international export markets.
36
New opportunities: The parties to the plan believe these actions will spawn many profitable
downstream industries such as moulded rubber products, chemical, oil refinement and
servicing export markets with these derived products.
Independent auditors: To ensure transparency, all movement of waste tyres, from import
and/or manufacturers of new tyres and casings to final recycling or other disposal, will be
suitably documented, audited and reconciled on the National Centralized Computer System
(NCCS). The operations of all recyclers and processors will also, at their cost, be audited in
terms of the Companies Act and other applicable legislation.
Research and development: The Research and Development department, under the auspices
of the Fund, will also be active in providing other processes applicable to our environment.
All participants will be encouraged to do the same and the plan will not knowingly support
any illegal practices harmful to the environment.
2.4.4 Analysis of the plans
The proposed REDISA Plan has come at a time when South Africa needs to reinforce
stringent laws on their waste management strategies in particular the waste tyre problem.
Before the proposition of the plan no clear approach was used to tackle the accumulation of
waste tyres at landfill sites and illegal stockpiles. Beside, addressing the waste tyre problem
which includes the setting up and managing a national network for collecting and temporarily
storing waste tyres, delivery to recyclers, as well as supporting the development of a waste
tyre recycling industry, the plan also helps with job creation, capacity building, and creation
of small businesses as well as research development of new and innovative techniques on
waste tyre utilization. Despite the various challenges and criticism the plan has received from
competitors, it has been gazetted and only awaits implementation. However, the plan lacks
media coverage as majority of tyre dealers from disadvantaged communities, who account for
75% of waste tyre recycling[40], are not knowledgeable about the existence of the plan.
Lastly, the REDISA stockholders should compare the proposed SA levy to those in other
countries. The authors support the REDISA plan as a well thought solution to the waste tyre
problem. The Plan is seen as a viable approach to remedy the waste tyre problem through the
introduction of a proposed levy fee of R2.30.
The SATRP Plan is an all rounded and well detailed plan which took into account most of the
relevant key objections which are required for the IIWTMP. However, the Department of
Environmental Affairs has the following objections about the plan: The SATRP plan has
37
excluded some of the key issues, for examples, the inadequate consideration of the Waste
Hierarchy, which is the cornerstone of waste legislation in the country. In addition, the plan
failed to address the inclusion and development of previously disadvantaged communities,
which are currently involved in the informal tyre sector.
Lastly, although the RMIO has existed longer than both SATRP and REDISA, the plan
however lacked clear direction in its waste tyre strategy. The plan was not inclusive of future
projected costs as well as implementation strategies. This resulted in a poorly drafted plan
which lacked the inclusion of current waste tyre dealers in the plan. However, it is evident
that RMI supported the implementation of new technologies such as pyrolysis into their plan.
2.5 Waste Tyre Disposal Alternatives
While considering the disposal of used tyres, it is essential to be aware of the different
materials and substances used in the production of tyres. Tyres are a multifaceted mixture of
very different materials. Natural or synthetic rubber, mixed with several ingredients, upon
vulcanisation and coupling with the wire gauze, forms the tyre. Due to the vulcanised nature
of rubber, used tyres are not directly reusable in the production cycle. In fact, the
vulcanisation transforms the elastomer into a non- fusible and insoluble substance.
2.5.1 Rubber
Tyres are designed to be tough and hard-wearing, once they reach their end of life they are
difficult to dispose. The main component of tyres, rubber, is a chemically cross-linked
polymer; which is neither fusible nor soluble, consequently cannot be remoulded without
degradation[41]. In rubber manufacturing, vulcanisation thermally disintegrates rubber
creating a hard plastic rubber that retains its form for tyre application. Antioxidants are added
to tyres to counter zone effects and material fatigue. The addition of steel, rayon and nylon
plus the process of vulcanisation contribute to the non-recycling character of tyres. The
processes and facilities required to extract rubber, steel and fibre from tyres are costly, and
the resultant products are generally of low value[42]. Two major approaches to address this
problem are recycling and the reclaiming of raw rubber materials.
2.5.1.1 Reuse of used and waste rubber products
Polymers can be classified as thermoplastics or thermosetting materials. Thermoplastics
soften when heated, may be moulded and then cooled to obtain the desired geometry. This
process may be repeated either by direct reheating or preferably after grinding into granules.
38
Thermosetting (thermosets) materials, like rubbers, upon processing and moulding are cross-
linked and therefore cannot be softened or remoulded by heating again. Chemical additives
are generally incorporated into both thermoplastics and thermosets as stabilizers, flame-
retardants, colorants and plasticizers to optimize product properties and performance. As a
result, thermoplastics are more readily recyclable than thermoset polymers and rubbers.
Recycling of thermoplastics simply involves a reversible physical change by heating the resin
above its processing temperature for reshaping and then cooling to room temperature to
obtain the desired recycled product. Hence, recycling of thermoplastics is less troublesome
and the technology for its re-fabrication is well established and economical. However
recycling for thermosetting materials like rubber is difficult. The three dimensional network
of the thermoset polymer must be broken down either through the cleavage of crosslinks or
the carbon–carbon linkage of the chain backbone. This is a much more resilient process and
the fragmented products obtained by such cleavage are entirely different from the starting
thermoset or even its precursor thermoplastics material. Thus, a recycled thermoplastic
material competes directly with the virgin polymer. Its commercial viability depends upon
the performance or cost benefit of the finished product, in contrast to thermoplastics. The
technology for the recycling of thermoset polymers including rubbers is complex, costly and
less viable commercially[42]. Reclaimed thermoplastics are used along with virgin resins and
fresh additives to obtain desired properties in the formation of final products. Recycled
plastics undergo significant changes in physical properties in its recycle phase, but still it
retains an acceptable fraction of virgin resin properties[43]. This behaviour is also observed
in reclaimed rubber.
2.5.1.2 Reclaiming of rubber raw materials
The 2003 waste tyre situation in South African was as follows, 10% of waste tyres were
landfilled, 4% recycled and the remaining 86% illegally re-grooved or dumped in the veld
and burnt to recover steel or stockpiled [38]. The statistics for developed and developing
counties is also shown in Table 2.9 [38, 44].
39
Table 2.9
2010 Global waste tyre treatment situation
Method of treatment (%) France Germany Italy Cyprus Spain UK
South Africa (2003)
Reuse 9,18 1,63 0 0 0 9,65 -
Export 0 13,68 3,58 0 2,82 11,84 0
Retreading 10,98 7,33 12,84 0 10,09 7,02 -
Civil Engineering Application 9,69 0 5,97 0 4,69 16,45 -
Recycled 32,65 35,02 23,88 0 18,78 32,67 4
Energy 37,5 42,35 53,73 0 42,78 22,37 -
Landfill 0 0 0 100 21,36 1,97 10
Towards the end of the1950s, nearly one fifth of the rubber used in the United States and
Europe was reclaimed. By the middle of the 1980s less than 1% of the world polymer
consumption was in the form of reclaim[45]. In the beginning of the 20th
century half of the
rubber consumed was in the form of reclaim. It is expected that during the 21st century most
of the scrap rubber will be recycled in the form of reclaim due to increasing environmental
awareness.
Engineering and construction application:
The rubber reclaimed from waste tyres has several applications. In civil engineering and the
construction industry, they are used for play-ground surfaces, parking lots, bank stabilization,
under road surface filling and asphalt modifiers. Tyres have essential building properties such
as light weight, low earth pressure, good thermal insulation and good drainage properties.
Another important property is its improved damping property which is good for running
vehicles. However, recent fires have set back the use of ground scrap rubber for many of
these applications[42].
In most of these applications, scrap tyres replaces other construction materials. Rubber
modified asphalt has increased durability, reduced reflective cracking, thinner lift and
increase skid resistance[46]. Asphalt modified rubber is also used for water-proofing
membranes, crack and joint sealers, hot mix binders and roofing materials. The rubber
improves asphalt ductility, thus increasing the temperature at which asphalt softens. The
aggregate adhesive bond becomes stronger and increases asphalt shelf life.
40
Building environment application:
Rubber is used for retaining walls, erosion control, barricading of shoring embankments, road
embankment fill and thermal insulation in housing foundations.
Agricultural application:
Farmers may use waste tyres as erosion control barriers.
Application of shredded, crumbed and granulated tyres
Shredded tyres can be used as fillers in roads, railway and construction developments. Finely
shredded old tyres can also be used as mulch (protective cover) which is long lasting, and is
presumed to be non-leachable[45]. Rubber mulches (in a variety of colours) have been
awarded innovation awards, and are becoming widely used in gardens, parks, playgrounds
and equestrian arenas. Rubber mulches are said to be permanent and aesthetically pleasing
landscape materials. Waste tyre recycling is a promising environmentally-friendly solution to
the waste tyre challenge in South Africa.
2.5.2 Material recovery
Waste tyre can be milled to obtain powder or granules with a specific configuration using
various techniques such as mechanical milling, cryogenic milling and de-vulcanization
processes. However, de-vulcanization processes are rarely used because of their high
operating costs[46].
2.5.2.1 Tyre remoulding
Fatigued rubber is replaced with a new tread. The new tread rubber is fused to the old carcass
by vulcanisation thus, re-treading the old tyre.
2.5.2.2 Mechanical milling
Rubber is broken down by mechanical shredding at high temperatures with the purpose of
recovering steel wire. Milling plants are normally of low cost and produce minimum
emissions. However, the high power consumption and limited market for the products are the
main drawbacks and thus require further research[46].
2.5.2.3 Cryo-mechanical milling process
In the mid-1960s, the technique of grinding scrap rubber, particularly tyres, in cryo-
mechanical process was developed[47]. Cryogenically ground rubber is used in tyres; hoses;
belts and mechanical goods; wire and cables and various other applications. This is
41
particularly useful in tyre inner liners. In this process, the rubber is cooled using liquid
nitrogen at a temperature range of -60oC to -100
0C. The rubber becomes fragile and mills
easily into very fine particles using ball or hammer milling. The high consumption of both
energy and liquid nitrogen make the process very expensive.
2.5.2.4 Microwave method
This is used to cleave carbon–carbon bonds. Waste tyres and rubber material can be
reclaimed without de-polymerization to a material capable of being re-compounded and re-
vulcanized with physical properties equivalent to the original vulcanizate. This route provides
an economical and ecologically sound recycling method for waste tyres. Furthermore, this
process can produce products similar to virgin rubber. It has been found that the tensile
property of de-vulcanized rubber and virgin rubber blend is almost comparable[48]. The cost
of de-vulcanized hose and inner tube material by microwave method is only a fraction of the
cost of the original compound. The transformation from waste to refined stock ready for
remixing takes place in only about five minutes with usually 90–95% rubber recovery[47].
Therefore, the microwave technique is a unique reclaiming process with regards to product
properties and process swiftness.
2.5.3 De-vulcanization technologies
The following section deals with the types of de-vulcanization technologies; they are
identified and grouped into the following categories:
2.5.3.1 Chemical
Organic Solvents
This type of chemical method is based on the use of 2-butanol solvent as a de-vulcanizing
agent for sulphur-cured rubber under high temperature and pressure. Reference[49] reported
that the molecular weight of the rubber is retained and its microstructure is not significantly
altered during the process. However, the process is extremely slow and requires separation of
the de-vulcanized rubber from the solvent. The process is applicable to de-vulcanization of
finely ground tyre rubber, but so far it has been carried out only on a very small laboratory
scale. Another type of chemical technology uses a solvent to treat the surface of crumb rubber
particles of sizes within 20 to 325 mesh. This is similar to the proposal by Hunt and Kovalak.
The process is carried out at a temperature range between 150° to 300°C, at a pressure of at
least 3.4 Mega Pascals, in the presence of solvent selected from the group consisting of
alcohols and ketones[50], [51], [52].
42
Oils and chemicals
Diallyl disulphide is the major constituent in a simple process for reclaiming rubber using a
vegetable product that is a renewable resource material. Other constituents of this material are
different disulphides, monosulphides, polysulphides, and thiol compounds[53]. Sulphur
vulcanized natural rubber (NR) can be completely recycled at 200° to 225°C by using
diphenyl disulphide. A decrease on crosslink density by 90 % was found when ethylene
propylene diene monomer rubber (EPDM) sulphur vulcanizates and diphenyldisulphide were
heated to 275°C in a closed mold for two hours. At the same time, EPDM cured by peroxide
showed a decrease in crosslink density of about 40 % under the same conditions[54].
Inorganic compounds
Discarded waste tyres have been de-vulcanized by desulphurization of suspended rubber
vulcanizate crumb (10 to 30 mesh) in solvents such as toluene, naphtha, benzene,
cyclohexane, etc. in the presence of sodium[55]. The alkali metal cleaves mono-, di-, and
poly- sulphur crosslinks of the swollen and suspended vulcanized crumb rubber at around
300°C in the absence of oxygen. However, this process may not be economical because it
involves swelling of the vulcanized crumb rubber in an organic solvent. In this process, the
metallic sodium in a molten condition should reach the sulphur crosslink sites in the crumb
rubber. In addition, the solvents may cause pollution and become hazardous.
2.5.3.2 Ultrasonic
Rubber de-vulcanization by using ultrasonic energy was first discussed in Okuda and Hatano
(1987). It was a batch process in which a small piece of vulcanized rubber was de-vulcanized
using 50 kHz ultrasonic waves after treatment for 20 minutes. The process apparently could
break down C-S and S-S bonds, but not carbon-carbon (C-C) bonds. The properties of the
devulcanized rubber were found to be very similar to those of the original vulcanizates[56].
One continuous process is based on the use of high-power ultrasound electromagnetic
radiation. This is a suitable way to recycle waste tyres and waste rubbers. The ultrasonic
waves, at certain levels, in the presence of pressure and heat, can quickly break up the three-
dimensional network in cross-linked, vulcanized rubber. The process of ultrasonic de-
vulcanization is very fast, simple, efficient, and it is free of solvents and chemicals.
43
2.5.3.3 Microwave
Microwave technology has also been proposed to de-vulcanize waste rubber[57]. This
process applies the heat very quickly and uniformly on the waste rubber. The method
employs the application of a controlled amount of microwave energy to de-vulcanize a
sulphur-vulcanized elastomer (containing polar groups or components) to a state in which it
could be compounded and revulcanized into useful products such as hoses. The process
requires extraordinary or substantial physical properties. On the basis of the relative bond
energies of C-C, C-S, and S-S bonds, the scission of the S-S and carbon-sulphur crosslinks
appeared to take place. However, the material to be used in the microwave process must be
polar enough to accept energy at a rate sufficient to generate the heat necessary for de-
vulcanization. This method is a batch process and requires expensive equipment.
2.5.3.4 Biological
Biological processing of vulcanized rubber has been used in some cases, although vulcanized
materials are resistant to normal microbial attack[58]. Several researchers have reported using
different types of microorganisms to attack the sulphur bonds in vulcanized elastomers. One
process uses a chemolithiotrope bacterium in a liquid solution to depolymerize the surface of
powdered elastomers. The polymer chains are then available to bond again during the
vulcanization process. The same type of bacterium has been shown to de-vulcanize crumbed
scrap rubber when held in an aerated liquid suspension of micro-organisms[59]. Reportedly,
sulphur can be recovered in this process, as well as de-vulcanized rubber. The rate of de-
vulcanization was found to be a function of particle size, with best results secured for
particles in the range of 100 to 200 microns. However, only a small percentage of the sulphur
links were broken after 40 days of exposure.
2.5.3.5 Other
Mechanical
A mechanical or reclaim process has been used for the continuous reclaiming of whole tyre
scrap. Fine rubber crumb (typically, 30 mesh), is mixed with various reclaiming oils, is
subjected to high temperature with intense mechanical working in a modified extruder for
reclaiming the rubber scrap.
44
Steam With or Without Chemicals (Digester)
The digester process uses a steam vessel equipped with a paddle agitator for continuous
stirring of the crumb rubber while steam is being supplied. The wet process may use caustic
and water mixed with the crumb rubber, while the dry process uses steam only. If necessary,
various reclaiming oils may be added to the mixer in the vessel. The dry digester has the
advantage of less pollution being generated. Scrap rubber containing natural and synthetic
rubbers can be reclaimed by the digester process, with the use of reclaiming oil having
molecular weights between 200 and 1,000[56].
2.5.4 Energy and material recovery
In light of the overall environmental impact along with the drive towards energy and material
conservation, new waste tyre disposal options are being developed and implemented.
Material and energy recovery through process, such as pyrolysis, can significantly address the
waste tyre disposal problem. Fig 2.17 shows possible waste tyre treatment routes.
Fig. 2.17 Technologies for managing scrap tyres[60]
2.5.4.1 Thermal treatment
The thermal treatment processes encompass combustion, incineration, gasification and
pyrolysis of waste tyres, with the following advantages[61]:
The volume of waste can be reduced by more than 90%.
Net energy production with possible material recovery.
45
Destruction of organic substances which are harmful to human health.
The following difficulties are associated with the thermal treatment of waste tyres[61]:
Disposal of ash: Lead and cadmium salts used as stabilisers during tyre production
remain as ash causing disposal problems.
Toxic gases: Burning of tyres produce toxic gases such as SO2, H2S, HCl, HCN and
these require further treatment.
Soot: Incomplete burning of waste tyres produces soot. This has a much higher
heating value than municipal refuse, so requires further combustion and hence
requires higher flame temperatures.
Appropriate incinerators: To address the challenges such as higher temperatures,
minimal oxygen conditions and corrosive action of the gases, appropriate materials of
construction are required.
Incineration
The incineration of waste tyres may be defined as the reduction of combustible wastes to
inert residue by controlled high-temperature combustion. A typical waste tyre incineration
process is shown in Fig. 2.18. The combustion process is spontaneous above 400oC. It is a
highly exothermic process and once the process has stabilized it becomes self-supporting.
The thermal efficiency of this process is approximately 40% [62]. Waste tyres having a
calorific value of 7.5 - 8 MJ/kg are used as fuel in incinerators. The gas produced may be
used as heat for industrial processing or electricity production. Burning of refuse in steam-
generating incinerators and using it as a supplementary fuel is advanced and proven waste to
energy utilisation [61].
Furnace design and efficiency influences the general combustion performance. Incinerators
have to be designed for excellent burning and reduced soot production. Walls and furnace
beds must be able to withstand high temperatures of approximately 1150oC. Combustion
efficiency, the ratio of thermal energy output to global energy input, usually depends on
interdependent factors such as the fuel's physical characteristics, plant design, manufacturing
and operating conditions. The use of waste as a supplementary fuel in power plants offers
many advantages and drawbacks as shown in Table 2.10
46
Table 2.10
Benefit analysis of incineration
Advantages Disadvantages
Maximum heat-recovery Large capital-investment
Low air-pollution emissions Need for flue-gas cleaning
Environmentally-acceptable process Relatively high operating cost
Reduced power-production costs Skilled labour is required to operate the
system
Fig. 2.18 The scrap tyre incineration process[60]
2.5.5 Pyrolysis, Gasification and Liquefaction (PGL) Processes
PGL processes present alternatives for the disposal of scrap tyres. These technologies are
currently used for the conversion of carbonaceous materials to resource fuels and other
products, and these may become more significant as the supplies of natural fuels become
depleted.
2.5.5.1 Gasification
Gasification is a sub-stoichiometric oxidation of organic material and a typical process is
shown in Fig. 2.19. The thermochemical process for gasification is more reactive than
pyrolysis. It involves the use of air, oxygen (O2), hydrogen (H2), or steam/water as a reaction
agent. While gasification processes vary considerably, typical gasifiers operate at
temperatures between 700 and 800°C. The energy efficiency of the gasification process is
reported to be around 76% [63]. The initial step, de-volatilization, is similar to the initial step
in the pyrolysis reaction. Depending on the gasification process, the de-volatilization step can
take place in a separate reactor upstream of the gasification reaction, in the same reactor, or
simultaneously with the gasification reaction. The gasification process can include a number
47
of different chemical reactions, depending on the process conditions and the gasification
agent. Equations 2.1 to 2.8 show gasification reactions for carbonaceous char.
C + CO2 = 2CO ∆H° = +172 kJ ………………………………………… (2.1)
C + H2O (g) = CO + H2 ∆H° = +130 kJ ……………………………………. (2.2)
C + 2H2O (g) = CO2 + 2H2 ∆H° = + 88 kJ ……………………………… (2.3)
C + 2H2 = CH4 ∆H° = - 71 kJ ……………………………………….. (2.4)
CO + H2O (g) = CO2 + H2 ∆H° = - 42 kJ ……………………………….. (2.5)
CO + 3H2 = CH4 + H2O (g) ∆H° = -205 kJ ……………………………….. (2.6)
C + 1/2 O2 = CO ∆H° = -109 kJ ……………………………………….. (2.7)
C + O2 = CO2 ∆H° = -390 kJ ……………………………………….. (2.8)
The oxygen requirement for the partial oxidation process can be supplied by air, oxygen
enriched air, or pure oxygen at a range of pressures. The method of delivery of the oxygen is
an important factor in determining the expense and efficiency of the process. Energy is
required to compress the combustion air or to cause the cryogenic separation of oxygen from
the air. This additional energy use lowers the overall energy efficiency of the process.
However, due to the absence of nitrogen in the final gaseous product, its calorific value can
be improved from relatively low values of 4 to 10MJ/ m3 using low-cost, air-blown partial
oxidation driven gasifiers, to values of 10 to 15 MJ/m3 for oxygen-blown processes and 25 to
30 MJ/m3 for hydrogen-blown processes, which compares well with natural gas, 39MJ/m
3.
Indirect heating of the feedstock in the gasifier through circulation of inert solid particles
such as sand from an externally fired heater may improve thermal energy management of the
process[61].
48
Fig. 2.19 Scrap tyre gasification process[60]
2.5.5.2 Liquefaction
In the early 1980s, pilot studies focused on the liquefaction of wood wastes. For scrap tyres,
this will involve melting the rubber and mixing the melt with another liquid such as waste
engine oil for processing. Practical methods have been tried. Pilot studies used steam and
catalysts producing oil with a heating value of 34.89 MJ/kg and a specific gravity of 1.03.
The costs of commercial production were estimated to be higher than coal liquefaction[64].
Liquefaction is the thermochemical conversion of an organic solid into petroleum like liquid.
Liquefaction typically involves the production of a liquid composed of heavy molecular
compounds with properties similar, but not identical, to those of petroleum based fuels. The
mechanisms involved in waste tyre liquefaction process are: diffusion of solvent into the
rubber; rubber swelling; rubber degradation; rubber dissolution; product separation from
insolubles. The gases and condensates are regarded as important by-products of waste tyre
liquefaction. The gases start to evolve at around 200C, the rate of gas generation reach
maximum as the mixture reaches the reaction temperature, and then decrease to a low but
steady value. Condensate generation follows a similar pattern to gases and is composed of
hydrocarbons ranging from C6 to C20. Tyres could be liquefied singly, or in combination
with other waste materials and/or coal in co-processing schemes, in one or two stage
processes. The idea of including tyres into a coal liquefaction process has been proven to be
more advantageous on a development plant scale. Liquefaction provides an effective
approach for converting the organic content into oils.
2.5.5.3 Energy recovery
Waste tyres can be utilised as a fuel source. Tyres produce the same amount of energy per
unit mass as oil and slightly more than coal [65]. Hence, they can be used as an efficient fuel
for industrial processes such as power plants with minimum negative environmental impact
49
compared to coal. In most cases tyres are shredded but the use of whole tyres is also possible
with large machinery. The presence of steel belts hinders the use of whole tyres. The
shredding of whole tyres and removal of wires can be integrated as part of the process.
Energy from the direct combustion of waste tyres can be utilized in metal works, paper mills,
tyre factories and on a smaller scale, in farms, greenhouses and sewage treatment plants.
Population growth and increasing individual income result in increased energy demand
exerting pressure on both energy supply and price. Rising international oil prices as well as
local transport demands combined with escalating up stream processes (refining and
extraction) signals the end of cheap oil.
Fig. 2.20 Primary energy supply in South Africa 1998-2009 [66]
Fig. 2.21 Energy usage by sector 2006-2009 [66]
0,%
10,%
20,%
30,%
40,%
50,%
60,%
70,%
80,%
Coal Crude oil Gas Nuclear Hydro Renewables
1998 1999 2000 2001 2002 2003 2004 2005 2006 2009
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
1998 1999 2000 2001 2002 2003 2004 2005 2006 2009
50
In early 2008, South Africa experienced a shortfall in power generating capacity which
resulted in wide spread power shortages. General awareness and understanding of the value
of energy was lacking in the past mainly due to historical low energy costs in South
Africa[67]. The primary energy source in South Africa is coal as shown in Fig. 2.20. The
industrial and the transport sectors use a significant amount of energy compared to other
sectors. Fig. 2.20 also shows South Africa‟s slow transformation to alternative energy
sources, indicating a greater dependence on coal. As coal usage produces a lot of emissions
impacting negatively on the carbon footprint, there is significant need for the country to
invest in cleaner energy sources.
Government has promulgated regulations and published supporting documents, namely;
green papers; white papers; bills; acts and regulations; international agreements and
obligations; guidelines and policies and gazetted notices to aid in the protection of the
environment as well as the country‟s natural resources. For the past ten years extensive
research, development and demonstration has been done with the key focus being on research
with respect to new technologies as well as the adaptation or evaluation of existing
technologies for specific South African conditions such as high unemployment rate. Some of
these initiatory steps entail the conversion of waste into valuable and profitable products.
Waste to energy processes recover energy in the form of heat and fuel from waste sources.
The aim of these initiatives, besides job creation and generating income, is to reduce waste
volumes going to landfills. This approach can be adapted to address the waste tyre problem.
Thermal and no-thermal technologies may be used for material and energy recovery for waste
tyres, Table 2.11.
Table 2.11
Waste to energy technologies
Thermal technologies Non-thermal technologies
Gasification Anaerobic digestion
Plasma arc gasification Fermentation production
Pyrolysis Mechanical biological treatment(MBT)
Thermal depolymerisation a) MBT+ Anaerobic digestion
b) MBT to Refuse derived fuel
51
2.5.5.4 Pyrolysis
Pyrolysis has been applied in the past to carbonaceous materials such as coal or wood. The
ancient Egyptians practiced wood distillation by collecting tars and pyroligneous acid for use
in their embalming industry. Pyrolysis of wood to produce charcoal was a major industry in
the 1800s, supplying fuel for the industrial revolution. Charcoal was used for the smelting of
metals and it is still used today in metallurgy[64]. For thousands of years charcoal has been a
preferred heating fuel until it was replaced by coal. In the late 19th
century and early 20th
century wood distillation was still profitable for producing soluble tar, pitch, creosote oil,
chemicals, and non-condensable gasses often used to heat boilers. The wood distillation
industry declined in the 1930s due to the advent of the petrochemical industry and its lower
priced products. However, pyrolysis of wood to produce charcoal for the charcoal briquette
market and activated carbon for water purification is still practiced in the United States of
America (USA)[64]. Over the last 20–30 years, several laboratory, pilot-plant and even
commercial attempts have been made to establish economical units for pyrolysis of such
materials for example; Kobe Steel in Japan, Tosco in the USA, Tyrolysis in the United
Kingdom, Ebenhausen in Germany and many more[68].
Pyrolysis is an endothermic process that induces the thermal decomposition of feed materials
without the addition of any reactive gases, such as air or oxygen. The thermal efficiency of
this process is approximately 70%, and can increase to 90% with the use of pyrolysis
products as fuel[69]. The use of tyre chips instead of whole tyres may also increase the
efficiency of the process by 20-30%[4]. Some of the problems related to the process are the
high cost of the plant and residue treatment[4]. The thermal energy used to drive the pyrolysis
reaction is applied indirectly by thermal conduction through the walls of the containment
reactor. Pyrolysis generally occurs at temperatures between 400 and 800°C[6]. As the
temperature changes, the product distribution (or the phase of the product) are also altered.
Lower pyrolysis temperatures usually produce more liquid products while higher
temperatures favour the production of gases.
The speed of the process and rate of heat transfer also influences the product distribution.
Slow pyrolysis (carbonization) can be used to maximize the yield of solid char. This process
requires a slow pyrolytic decomposition at low temperatures. Rapid quenching is often used
to maximize the production of liquid products, by condensing the gaseous molecules into
liquid. In some pyrolysis processes, a product that is up to 80% liquid by weight can be
52
produced[68]. Hydrogen or steam can also be used in the pyrolysis process to change the
makeup of the product distribution. Hydrogen can be used to enhance the chemical reduction
and suppress oxidation by means of the elemental oxygen in the feedstock. Steam can also be
used as a pyrolyzing medium, allowing pyrolysis to occur at lower temperatures and higher
pressures. The use of water as a pyrolyzing media also allows the feedstock to be introduced
into the reactor in an aqueous form. An additional advantage of water or steam is that the
resulting char has a relatively high surface area and porosity that is similar in nature to
activated charcoal. Nitrogen gas can be supplied to maintain the inert atmosphere in the
reactor and also to sweep away the pyrolyzed vapour product to the condensers. Furthermore,
purging the system with nitrogen helps to minimise secondary reactions in the hot zone.
Some of the problems related to the process are the high cost of the plant and residue
treatment[4]. Fig. 2.22 shows the pyrolysis process pathway.
Fig. 2.22 Scrap tyre pyrolysis process[60]
Influence of operating parameters on yield
The pyrolysis process yields a gaseous fraction of mainly non-condensable gases, a solid
fraction mainly composed of carbon, metal and other inert material as well as an oily fraction
mainly composed of organic substances condensable at ambient temperature and pressure.
The composition of the pyrolysis products is influenced by the process operating conditions
such as, feed size, operating temperature and pressure, residence time, heating rate as well as
the presence of catalytic medium.
53
Feed size
Smaller feed size particles provide more reaction surface, giving high heating rate and rapid
decomposition of rubber. The oil product vapours comparatively get enough time for
secondary reactions in the reactor and this consequently increases gas yield and reduces
liquid and char yields[68]. On the other hand, the heating rate in larger tyre feed is low due to
its lower thermal conductivity, in addition heat can flow only to a certain depth in the
available pyrolysis time compared to almost complete thermal decomposition of the smaller
pieces. Thus, the rubber core of the larger pieces becomes carbonized and/or cannot be
decomposed completely resulting in increased char yield and decreased liquid and gas yield.
Fig. 2.23 shows the effect of feed size on product yield.
Fig. 2.23 Effect of feed size on product yield[8]
Temperature
The increase in gas yield with a corresponding reduction in liquid yield with increase in
temperature is due to vapour decomposing into permanent gases, and secondary re-
polymerization as well as carbonization reactions of oil hydrocarbons into char [68]. It is
also a result of char loss and thermal cracking. Thus, high gas yields dominate at higher
temperatures, Fig 2.24.
0
10
20
30
40
50
60
Pro
du
ct y
ield
Increasing feed size
Liquids Char Gas
54
Fig. 2.24 Effect of temperature on product yield[8]
Residence time
An increase in vapour residence time decreases liquid and char yields while the gas yield
increases slightly. This is due to the decomposition of some oil vapour into secondary
permanent gases. Primary vapours are first produced from tyre pyrolysis at optimum
temperature, the primary oil vapours then degrade into secondary gases. For instance: oil
vapours→ heavy hydrocarbons + light hydrocarbons (CH4 + C2H4 + C3H6 +……) + (CO +
CO2 + H2)[68] leading to less oils and more gaseous products. In addition, longer contact
time of the volatiles and char leads to another parallel secondary pyrolysis reaction:
C + CO2 → 2CO which reduces the char yield[68], Fig 2.25.
0
10
20
30
40
50
60
Pro
du
ct y
ield
Increasing temperature
Liquids Char Gas
55
Fig. 2.25 Effect of residence time on product yield[8]
Table 2.12 shows a typical tyre composition. There are many different manufacturers with
various tyre formulations. Hence, the yield and composition of waste tyre pyrolysis depend
on the source and grade of tyres[68]. Table 2.13 shows a summary of the process operating
conditions, final product yields as well as the resulting pollutants for incineration, gasification
and pyrolysis.
0
10
20
30
40
50
60
Incr
ea
sin
g p
rod
uct
yie
ld
Increasing residence time
Liquid Char Gas
56
Table 2.12
Composition of whole tyres
Rubber 38%
Fillers (Carbon black, silica, carbon chalk) 30%
Reinforcing material (steel, rayon, nylon) 16%
Plasticizers (oils and resins) 10%
Vulcanisation agents (Sulphur, zinc oxide, various chemicals) 4%
Antioxidants to counter ozone effect and material fatigue 1%
Miscellaneous 1%
Elementary Composition
Carbon 86.40%
Hydrogen 8.00%
Nitrogen 0.50%
Sulphur 1.70%
Oxygen 2.40%
Proximate Analysis
Volatiles 62.10%
Fixed carbon 29.40%
Ash 7.10%
Moisture 1.30%
57
Table 2.13
Comparison of incineration, gasification and pyrolysis
Process Incineration Gasification Pyrolysis
Process
definition
The combustion of any waste
material to maximize waste
conversion to high heating
value fuel gases mainly CO,
H2 and CH4
Gasification is a sub-
stoichiometric oxidation of
organic material to
maximize waste conversion
to high temperature flue
gases, mainly CO2 and H 2.
The thermal degradation
of carbonaceous material
in an oxygen deprived
atmosphere to maximize
thermal decomposition
of solid into gases and
condensed liquid and
residual char.
Operating conditions:
Reaction
environment
Oxidizing (oxidant amount
larger than that required by
stoichiometric combustion)
Reducing (oxidant amount
lower than that required by
stoichiometric combustion)
Total absence of any
oxidant
Reactant gas Air Air, pure oxygen, oxygen
enriched air, steam
None
Temperature Between 850 oC and 1200
oC
[51]
Between 550 – 900 oC[63]
(in air)
Between 500 and 800 oC
[6]
Pressure Atmospheric Atmospheric Slightly above
atmospheric pressure
Process output:
Produced gases CO2, H2O CO, H2, CO2, H2O, CH4 CO, H2, CH4 and other
hydrocarbons
Produced
liquids
Treated and disposed as
industrial waste.
Condensable fraction of tar
and soot which is minimal.
Oil is similar to diesel
and can be used as a fuel.
. High aromatic content,
thus can serve as a feed
stock in the chemical
industry
Produced solids Bottom ash can be treated to
recover ferrous (iron, steel)
and non-ferrous metals (such
as aluminium, copper and
zinc) and inert materials (to
be utilized as a sustainable
building material).
After the combustion
process. Bottom ash is often
produced as vitreous slag
that can be utilized as
backfilling material for road
construction.
The pyrolysis char
residue has a
considerable amount of
carbon content and can
either be utilized as tyre
derived fuel for the
process or be sold as a
carbon-rich material for
the manufacture of
activated carbon or for
other similar industrial
purposes
Pollutants SO2, NOx, HCl, particulate H2S, HCl, COS, NH3, HCN,
tar, alkali, particulate.
H2S, HCl, NH3, HCN,
tar, particulate.
58
Pyrolysis gas
The approximate yield of gas from waste tyre pyrolysis is about 10-30% by weight[64] and it
increases with increasing pyrolysis temperature. The pyrolysis derived gas has a calorific
value of approximately 30-40MJ N/m-3
[62] and can be sufficient to provide the energy
required for a small scale process plant. The carbon oxide components (COx) are mostly
derived from the oxygenated organic compounds in tyres, such as stearic acid and extender
oils. H2S is a product of the sulphur links vulcanized rubber structure composition and its
concentration is low. C4 and >C4 gases are the most predominant products and these result
from the depolymerisation of styrene-butadiene-rubber (SBR), usually the main constituent
of automotive tyres. Table 2.14 [68] shows the gaseous constituents produced during the
pyrolysis of tyres. The components of the gas obtained from tyre pyrolysis at 400, 500, 600
and 700°C is shown by Fig. 2.26. The gaseous product mixture is made of shorter aliphatic
chains than SBR due to rubber cracking and subsequent reactions to form lighter gases.
Table 2.14
Pyrolysis gas constituents
Component Chemical formula
Carbon monoxide CO
Carbon dioxide CO2
Hydrogen sulphide H2S
Methane CH4
Ethane C2H6
Ethene C2H4
Propane C3H8
Propene C2H6
Butane C4H10
Butene C4H8
Butadiene C4H6
Pentane C5H12
Pantene C5H10
Hexane C6H14
Hexene C6H12
The undesired H2O and CO can be removed using several physical-chemical or biological
abatement methods. H2O can be abated using the following methods: (a) The Claus Process is
used in oil and natural gas refining facilities and removes H2S by oxidizing it to elemental
sulphur. The following reactions 2.5.1 to 2.5.3 occur in various reactor vessels and the
removal efficiency is about 95% using two reactors, and 98% using four reactors. (b)
Chemical oxidants are most often used at wastewater treatment plants to control both odour
and the toxic potential of H2S. The most widely used chemical oxidation system is a
combination of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl), which are
59
chosen for their low cost, availability, and oxidation capability, equation 2.5.4 to 2.5.5. (c)
Caustic scrubbers function similarly to chemical oxidation systems, except that caustic
scrubbers are equilibrium limited, meaning that if caustic is added, H2S is removed, and if the
pH decreases and becomes acidic, H2S is produced. The pH is kept higher than 9 by
continuously adding sodium hydroxide (NaOH), equation 5.2.6 describes the caustic
scrubber reaction[70]. (d) An adsorbing material can attract molecules in an influent gas
stream to its surface, this removes them from the gas stream. Adsorption can continue until
the surface of the material is completely covered, the materials must either be regenerated
(undergo desorption) or replaced. Regeneration processes can be both expensive and time
consuming. Activated carbon is often used for the removal of H2S by adsorption. Activated
carbon can be impregnated with potassium hydroxide (KOH) or sodium hydroxide (NaOH),
which act as catalysts to remove H2S[70]. (e) H2S scavengers are chemical products that react
directly with H2S to create innocuous products. Some examples of H2S scavenging systems
are: caustic and sodium nitrate solution, amines, and solid, iron-based adsorbents The
chemical products are applied in columns or sprayed directly into gas pipelines.(f) Amine
absorption units: Alkanolamines (amines) are both water soluble and have the ability to
absorb acid gases. Amines are able to remove H2S by absorbing them, and then dissolving
them in an aqueous amine stream. The stream is then heated to desorb the acidic
components, which creates a concentrated gas stream of H2S, which can then be used in a
Claus process unit or other unit to be converted to elemental sulphur. This process is best
used for anaerobic gas streams because oxygen can oxidize the amines, limiting the
efficiency and causing more material to be used[70]. Amines that are commonly used are
monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA).
Amine solutions are most commonly used in natural-gas purification processes. They are
attractive because of the potential for high removal efficiencies, their ability to be selective
for either H2S or both CO2 and H2S removal, and are regenerable. (g) Liquid-phase oxidation
systems convert H2S into elemental sulphur through redox reactions by electron transfer
from sources such as vanadium or iron reagents. Hydrogen sulphide is first absorbed into an
aqueous, alkali solution. It is then oxidized to elemental sulphur, while the vanadium reagent
is reduced. This process is relatively slow and usually occurs in packed columns or venturis.
However, vanadium is toxic and these units must be designed so that both the “sulphur cake”
and solution are cleaned. (h) Using physical solvents as a method to remove acid gases, such
as H2S, can be economical depending on the end use of the gas. Hydrogen sulphide can be
dissolved in a liquid and later removed from the liquid by reducing the pressure. Water is
60
widely available and low-cost, it also has solubility potential for CO2. Other physical solvents
that have been used are methanol, propylene carbonate, and ethers of polyethylene glycol.
Criteria for selecting a physical solvent are high absorption capacity, low reactivity with
equipment and gas constituents, and low viscosity[71]. (i) Membrane Processes can be used
to purify biogas. Membranes are not usually used for selective removal of H2S, and are
rather used to upgrade biogas to natural gas standards. There are two types of membrane
systems: high pressure with gas phase on both sides of the membrane, and low pressure with
a liquid adsorbent on one side[71]. (j) Biological methods: microorganisms have been used
for the removal of H2S from biogas. Ideal microorganisms would have the ability to
transform H2S to elemental sulphur, could use CO2 as their carbon source (eliminating a need
for nutrient input), could produce elemental sulphur that is easy to separate from the biomass,
would avoid biomass accumulation to prevent clogging problems, and would be able to
withstand a variety of conditions (fluctuation in temperature, moisture, pH, O2/H2S ratio, for
example). Chemotrophic bacterial species, particularly from the Thiobacillus genus, are
commonly used both aerobically and anaerobically. Under limited oxygen conditions,
elemental sulfur is produced and under excess oxygen conditions, SO4 2-
is produced, which
leads to acidification.
⁄ …………………………………………… 2.5.1
…………………………………………… 2.5.2
⁄ ………………………………………….... 2.5.3
…………………………………………… 2.5.4
…………………………………… 2.5.5
…………………………………………… 2.5.6
61
Fig. 2.26 Compositions of the gases obtained in tyre pyrolysis at different temperatures[68]
Pyrolysis oil
There is need for greener fuel alternatives due to fossil fuel depletion, increasing oil prices
and emission challenges. Tyre pyrolytic liquids production pathways with their wide range of
potential applications are shown in Fig. 2.27.
Fig. 2.27 Tyre pyrolysis conversion and products applications[72]
0
0,005
0,01
0,015
0,02
0,025
0,03
COx H2S Total C1 Total C2 Total C3 Total C4 Total C5
g o
f gas
/g o
f ty
re
Constituent
400oC
500oC
600oC
700oC
Tyre wastes
Tyre Pyrolysis Liquids
62
The waste tyre pyrolytic liquid is an oily organic compound, dark brown in colour with a
strong acrid smell. This oil should be handled carefully as it reacts easily with human skin,
leaving permanent yellowish brown marks and an acrid smell for a few days, and this is
difficult to remove using detergents. The tyre derived oil is composed mainly of alkylated
benzenes, naphthalenes, phenanthrenes, n-alkanes from C11 to C24, and alkenes from C8 to
C15, with small quantities of nitrogen, sulphur and oxygenated compounds[72]. The pyrolysis
oil has a high calorific value of about 44 MJ/kg compared to that of waste tyres, 33
MJ/kg[72]. The calorific value of the oil is also higher than that of bituminous coal, 28
MJ/kg[73] and wood charcoal, 30 MJ/kg[74]. Pyrolytic oils can be used as liquid fuels for
industrial furnaces, power plants and boilers. The oil has a relatively low ash content and
residual carbon as shown in Table 2.15[64].
Table 2.15
Characteristics of vacuum pyrolysis waste tyre derived oil
Gross calorific value (MJ/kg) 43.8
Water content (wt.%) 1.6
Sulphur content (wt.%) 1.5
Chlorine content (ppm) 180
Carbon Conradson residue 1.8
Ash content (wt.%) traces
The liquids are very complex mixtures, containing aliphatic and aromatic compounds with
their total concentration of 49.54% and 16.65%, respectively[64]. The aliphatic compounds
mainly consist of alkanes and alkenes with alkenes being the predominant group, 43.23%.
The aromatic compounds are mainly single ring alkyl aromatics. The aromatic nature of the
waste tyre pyrolytic oils is due to aryl chain fragments from SBR aromatic rings splitting and
cyclisation of olefin structures through dehydrogenation reaction, Fig. 2.28.
63
Fig. 2.28 Formation of polycyclic aromatic hydrocarbons in scrap tyre [2]
Nitrogen and nitro-sulphureted compounds originate from the thermal degradation of
accelerators used in tyre compounding and these are usually sulphur and/or nitrogen based
organic compounds. The oils have higher carbon content, leading to the production of high
value carbon materials for various applications, Table 2.16 [72]. They are also contaminated
with little metallic elements, Table 2.17 [72]. The olefinic composition of the waste tyre
pyrolytic oil is similar to that of condensates from petroleum residues cracking and thermal
steam cracking of gasoline[4]. Hence, pyrolytic oil may be blended with these condensates
and subjected to the same thermal treatment.
Table 2.16
Elemental composition of oils obtained by vacuum pyrolysis of used tyres (wt. %)
Carbon Hydrogen Nitrogen Oxygen C/H
Passenger car tyres 86.5 10.8 0.5 2.2 0.67
Table 2.17
Waste tyre-derived pyrolytic oil impurities (ppb)
V Mn P Mg Na Ba As Ti Ni Fe Cu Al Zn Pb Ca Cr Cd CO
34 6 142 134 1280 198 73 5585 104 4030 104 4030 2044 918 458 93 24 26
64
Monoterpene [1-methyl-4-(1 methylethenyl)-cyclohexene], also known as limonene
constitutes about 30%[64] of pyrolytic liquids. dl-Limonene (dipentene) is produced from the
thermal decomposition of poly-isoprene or natural rubber. It has extremely fast growing and
vast industrial applications including formulation of resins and adhesives; dispersing agent
for pigments; fragrance in cleaning products and an environmentally acceptable solvent[69].
It also has applications in the cosmetic industry[75].
Pyrolysis Char
Activated carbon from pyrolytic char can be used for water purification and air purification,
as well as in batteries and fuel cells. Pyrolytic char has a calorific value comparable to high-
grade coal and may therefore be used as fuel either in pulverised or briquetted form. The
application of pyrolytic char as low grade carbon black for the manufacturing of
thermoplastics and a low cost adsorbent for the treatment of industrial effluents has also been
suggested[76]. The potential of the tyre carbon black product as possible adsorbents for
various pollutants has been assessed and found to be very successful, thus stimulating a huge
research interest[77]. Activated carbon can be used to adsorb phenols, basic dyes, metals, p-
chlorophenols, butane and natural gas. The production, characterization and uses of carbon
black as printing inks bases and recycled tyre fillers have been studied[77]. To enhance the
commercial value of waste tyre pyrolytic carbon black and increase its potential application
as activated carbon, further treatment such as chemical activation is required. This allows
both pyrolysis and activation to be integrated into a single, relatively lower temperature
process in the absence of oxygen. Demineralization of carbon black with acid (sulphuric and
hydrochloric acid) followed by activation at high temperature, normally 900oC, in a furnace
is common[76]. Commercial activation of carbon black is usually conducted at temperatures
above 800oC in a mixture of steam and carbon dioxide. There is general agreement that steam
is a more reactive agent than carbon dioxide[77]. Activation increases the surface area while
decreasing the concentration of contaminants or non-carbon material. Table 2.18[78] shows
the characteristics of untreated and activated carbon black samples.
65
Table 2.18
Surface area and elemental composition of pyrolytic carbon black and activated carbon black (wt%)
Surface area (m2/g) C O Si S Z Ca
Carbon black (not treated) 85 83.1 6.0 1.6 2.6 4.2 2.4
Carbon black (HCl treated) 870 93.0 5.1 0.4 0.9 0.6
Carbon black activated (HCl treated) 940 93.9 4.3 0.4 0.8 0.6
Carbon black (H2SO4) 800 87.0 5.9 0.6 1.8 2.9 1.8
Carbon black activated (H2SO4 treated) 910 30.0 4.4 0.6 1.2 2 1.8
Activated carbon (commercial) 990 96.0 2.9 0.3
Steam-activated carbon black present greater capacities for the adsorption of small and
medium size species such as phenol and methylene blue, while carbon dioxide-activated
adsorb larger molecular size compounds such as textile dyes more effectively[79]. Carbon
black characteristics are influenced by the nature of activation and process temperature to a
lesser extent.
Liquid-phase applications:
Activated carbon has been used in the removal of both organic and inorganic species from
industrial effluents[77]. Due to the high surface area 164 to 1260 m2/g and pore volumes up
to 1.62 cm3/g[80], tyre carbon black is considered as a potential adsorbent in water treatment
particularly for the removal of organic pollutants such as phenol and p-chlorophenol.
Potassium hydroxide (KOH) activated waste tyre pyrolytic carbon black can be used to
remove halogenated hydrocarbons and pesticides from drinking water. Tyre-derived carbon
may also be used to remove chromium, lead, copper, dyes and phenol from industrial waste
waters.
Gas-phase applications
Activated carbon from waste tyres provides an effective means for gas-phase applications
such as the separation, storage and catalysis of gaseous species. One example is the storage of
natural gas for automobiles in which natural gas is adsorbed on tyre carbons under high
pressure. It can also be used for the transportation of flammable gases such as acetylene[79-
81]. Pyrolytic carbon black may be used in the treatment of industrial gaseous effluents. For
example, it was found to have a similar sulphur dioxide (SO2) adsorption rate to commercial
lignite-based carbon[79]. It was also found to be superior in the adsorption of mercury[77].
66
Pyrolysis steel wires
The pyrolysis derived steel wire marketing depends on the cleanliness, quantity, and
packaging of the product. The cleanliness of recovered steel is measured by the degree of
rubber contamination. Steel with less than 10% rubber is considered acceptable in the
market[82]. Thermal processing of scrap tyres can be used to recover steel with minimum or
zero rubber contamination. The quality is also influenced by the pyrolytic process. For a
batch process, the separation of steel and carbon black from pyrolytic oil is fairly simple.
This is complex for continuous pyrolysis, gasification and liquefaction processes where tyres
are usually ground into chips. In addition, the recycling of the recovered steel in the
manufacturing of steel products is hindered by the burning of residual sulphur[82].
The waste tyre market is influenced by the business cycle. During off peak, the processors
may give away the steel for free or pay markets for collection. Bailing is difficult for steel
recovered from shredded tyres. The added cost of transportation and storage reduces the
income from this waste stream. However, this may be cheaper than paying a tipping fee for
disposal. Table 2.19 gives the summary of the waste tyre applications with their benefits and
disadvantages.
67
Table 2.19
Summary of waste tyre applications
Application/Product Benefit Disadvantages
Alternative Fuel (Cement kilns or
power stations)
Conserves natural resources;
High calorific value;
Large volume potential;
Recovery of carbon, steel,
rubber
Special monitoring
equipment required to control
emissions;
Generally needs shredded
tyres;
Needs feeding system;
Costly to operate
Steel electric arc furnace and foundry
kilns
Total and complete recovery
of tyre components: carbon,
steel, rubber;
Replace high cost carbon
Measuring equipment
required to control emissions;
Generally needs shredded
tyres;
Costly to operate
Landfill Engineering
Lightweight, low density fill
material;
Good load bearing capacity;
Lower cost compared to
gravel;
Does not need well qualified
labour
Potential leaching of metals
and hydro-carbonates;
The steel cord in the tyre
could puncture the lining;
Compressibility of the tyre
Light weight or drainage fill
Reduced unit weight
compared to other
alternatives;
Flexible, with good load
bearing capacity;
Good drainage
Potential leaching of metals
and hydro-carbonates;
Deformation under vertical
load, when a proper soil
cover thickness is not used;
Difficulty in compaction
(need to use more than 10ton
roller, six passes, 300mm
lift)
Erosion control
Low density which allows
free floating structures to act
as wave barriers;
Bales are lightweight and
easy to handle;
Durability
Tyres should be securely
anchored to prevent mobility
under flood conditions;
Tyres can trap debris, (needs
maintenance);
Can shift over time due to
wave action rendering tyre
structures insecure;
Water action and tyre
buoyancy makes the
positioning of any permanent
protection below the surface
very difficult;
Ultimately such tyres become
waste again
Noise Barriers
Lightweight, and can
therefore be used in
geologically weak areas
where traditional materials
would prove too heavy;
Free draining and durable
Needs monitoring to avoid
accumulation of debris;
Visual impact
68
Rubber modified concrete
Lower modulus of elasticity
which reduces brittle failure;
Increased energy absorption
making them suitable for use
in crash barriers etc.;
Suitable for low weight
bearing structures;
Can be reprocessed by
grinding and mixing again
with cement
Relatively new product,
producers will need to
convince the construction
industry of its suitability
Train and tram rail beds
Longer life span compared
with timber (20 year for
rubber beds and 3 to 4 for
wood or asphalt);
Environmentally safe;
Better flush with road;
Use chips/shreds as vibration
damping layer beneath sub-
ballast
More expensive than
traditional material;
Relatively new product,
producers will need to
convince industry of its
suitability
Outdoor sport surfaces (equestrian,
hockey and soccer) or artificial turf
Skid resistant;
High impact resistance;
Durable;
Highly resilient;
Easy maintenance;
Independent of irrigation
Indoor safety flooring
Skid resistant;
High impact resistance;
Durable ;
Available in various colours;
Easy maintenance
More expensive than
conventional alternatives;
Colours may be limited;
Limited market
Shipping container liners
Possible use with other
packaging problems
More expensive than
conventional alternatives
Conveyer belts
Possible use as conveyer belt
at supermarket tills
More expensive than
conventional alternatives;
Cannot be used where belt is
subject to large stresses,
since it may be prone to
failure
Asphalt and bitumen modification for
Road applications
Increased durability;
Surface resilience;
Reduced maintenance;
Increased resistance to
deformation and cracking;
More resistant to cracking at
lower temperatures;
Aids in the reduction of road
noise;
Substitutes virgin materials,
like styrene-butadiene-
styrene;
Significant environmental
benefits documented with
respect to global warming
potential, acidification and
cumulative energy demand
It is very sensitive to changes
in conditions during mixing
i.e. requires expert
knowledge;
Difficult to apply in wet
weather;
Not applicable when ambient
or surface temperatures are
less than 13º C;
Possible occupational health
problems due to emissions;
It cannot be reprocessed like
traditional asphalt
Footwear
Water resistant;
Long life span;
By varying the thickness of
Could be more expensive to
manufacture than
conventional product
69
the sole the use of the
footwear can be changed
Carpet underlay
Easy to use;
Recyclable;
Conserves natural resources
Limited industrial production
Floor tiles
Resilient;
Skid resistant;
High impact;
Easy maintenance;
Recyclable
Limited industrial production
Activated carbon
(carbon black) Preserves virgin material
Very expensive process as it
needs pyrolysis;
Very energy intensive;
Low grade activated carbon;
Still in the research stage
Livestock mattresses
Long life span;
Easy to disinfect;
Reusable;
In the long term it is cheaper
than alternatives
Could be more expensive to
manufacture than
conventional mattresses;
Market potential unknown
Thermoplastic Elastomers (TPE)
Similar properties to typical
elastomeric materials
Very limited existing sites
Pyrolysis
Reutilizes the sub products of
pyrolysis (oil and gas)
Limited capacity because of
operational problems caused
by tyres;
very limited existing sites;
The sludge originating from
the process contains metals
and other wastes, which for
the moment is deposited in
abandoned mines, poses an
environmental problem
2.6 Product Markets
In order for pyrolysis success and sustainability, a market for the derived products should
exist. The primary products (oil, char and gas) can be further processed to value added
products. Product upgrade is expected to significantly improve the economics of scrap tyre
pyrolysis. This can significantly improve the commercial viability of waste tyre pyrolysis.
2.6.1 Oil
Fuel oil is classified into six classes, fuel oil 1 to 6, according to boiling point, composition
and purpose. The boiling point ranges from 176 to 600oC. Oil derived from the tyre PGL
process is similar to No. 6 fuel oil. This is also regarded as residual oil as it contains various
impurities including 2% water and 0.5% mineral soil[61].
70
2.6.1.1 Characteristics of No.6 Fuel Oil
No. 6 fuel oil is a thick, syrupy, black, tar-like liquid. It smells like tar, and may even become
semi-solid in cooler conditions. It is also known as bunker oil or black liquor and consists of
a complex mixture of hydrocarbons with varying boiling points[83]. It is used as fuel for
steam boilers and power generators. It is generally bought in large quantities and stored in
large tanks, either above or below the ground[82]. Heating is required before application to
increase flow ability, reduce pump demands and promote burning performance. Cool or cold
No. 6 fuel oil is quite stable with a flashpoint of about 65oC[61]. However, the oil also
contains hydrocarbons with flashpoints below 65oC, hence it has enough flammable vapours
capable of starting a fire[61]. Further refining of No.6 fuel oil produces No.2 fuel oil. These
fuel oils are variously referred to as distillate oils, diesel fuel oils and light fuel oils which are
easy flowing at room temperature. No.2 oil does not require preheating to pump or burn as
compared to No.6 fuel oils. Distillate fuel oils are complex mixtures of hydrocarbons that
also contain small amounts of sulphur, nitrogen and oxygen containing molecules. They
contain normal and branched alkanes, cycloalkanes (naphthenes) and partially reduced
aromatics. Fuel oil No. 2 has a carbon range of C11-C20[84].
No. 2 oil can be used for home heating installations as well as for medium capacity
commercial and industrial burners. Liquid fuels, such as petrol, diesel and jet fuel dominate
the transport industry. Fig. 2.29 shows the various South African energy sources for transport
in 2010. Petrol and diesel dominate the application in this sector.
Fig. 2.29 Percentage distribution of energy types used in the transport sector in South Africa, 2010[85]
0
50
100
150
200
250
300
350
400
450
Gasoline Diesel Kerosene Electricity Natural gas
En
erg
y f
or
tra
nsp
ort
(1
015J
ou
les)
Energy Type
71
2.6.2 Char
Carbon black, an important industrial carbon, is any of various finely-divided forms of
amorphous (non-structured) carbon. Carbon exists in two crystalline forms, and numerous
amorphous, less-ordered forms. The crystalline forms are diamond and graphite, and the less-
ordered forms are mainly cokes and chars. Carbon blacks differ in particle size; surface area;
average aggregate mass; particle and aggregate mass distributions; structure and chemical
composition. The application of carbon depends on chemical composition, pigment
properties, state of subdivision, adsorption activity, and other colloidal properties[86].
Potential uses include upgrading to commercial carbon black, specialized carbon blacks,
printing ink, activated carbon, and fuel. The char from PGL processes with a heating value
close to 30.5 MJ/kg is a valuable energy source. Its heating value is higher than that of South
African lignite coals (16.7 MJ/kg) and compares well with petroleum coke (34.9 MJ/kg)[77].
Thus, the char from PGL processes can substitute coal.
2.6.3 Gas
The pyrolysis gas has high concentrations of methane and ethane, resembling a natural gas,
Table 2.21. In most pyrolytic processes, this is used as a source of fuel. The large quantities
of carbon monoxide and carbon dioxide in the gas hinder its blending with natural gas.
Table 2.20
Ultimate analysis of pyrolysis gas
Parameter Quantity
Carbon 85.76%
Hydrogen 14.24%
Nitrogen trace
Sulphur trace
Oxygen trace
Ash trace
Heating value 44.6 MJ/Kg
One major advantage of waste tyre pyrolysis is that the gas produced can be used as fuel to
sustain the process. The process runs with 10 – 15% of the gas generated. This significantly
reduces operating costs. The rest can be supplied to burners, boilers and internal combustion
engines or can be compressed and stored for future use[77].
72
2.6.4 Steel
Clean scrap iron and steel can easily be marketed. In order to increase the market potential of
steel from shredded tyres, it needs to be baled.
2.7 Successes and Failures of Waste Tyre Pyrolysis
In 2010, about 3.3 million tonnes of used tyres were managed in an environmental acceptable
manner in the European Union (EU), a 2% increase from 2009[87]. About 2.7 million tons of
used tyres were treated; the balance was either recycled or recovered[87]. The potential of
waste tyre treatment through processes such as gasification, pyrolysis and liquefaction is
undervalued. However with the increase in global awareness in environmental friendly
treatment methods, EU countries have considered these processes as future waste tyre
treatment methods.
Currently there is a great deal of research on waste tyre pyrolysis. Juniper[60] identified 40
companies worldwide working on tyre pyrolysis. However, there is only one dedicated tyre
pyrolysis plant in the United Kingdom (UK) operating on a semi-commercial basis. It is
owned by Anglo Unites Environmental (AUE) and handles 1500 tonnes of waste tyres per
year. Other semi-commercial plants have been operated in the UK, Germany, South Korea
and Taiwan, but with limited success. Most of them have ceased operation, reportedly due to
financial difficulties[88]. One of the most recent pyrolysis plant to be commissioned is in
Cyprus (May 2010), with a design capacity of 150 tonnes per month of N660 carbon black,
180 tonnes oil and 70 tonnes per month of steel[89].
Despite the 30 years of research and development, the pyrolysis of scrap tyres and related
waste materials has not achieved commercial success in the United States, with economic
viability and product quality being the primary stumbling blocks[87]. Despite all these
challenges, pyrolysis is still considered as a potential waste tyre treatment option for
developing countries such as South Africa.
Several pyrolysis plants have been shut down in South Africa due to limited and unregulated
markets as well as noncompliance with environmental regulations[90]. In South Africa,
presently there is one operating pyrolysis plant in Pretoria and another in Durban at the
commissioning stage. The Pretoria plant produces pyrolysis oil for industrial applications, the
gas is flared and no use for the carbon black has been found[91]. There are 12 other plants in
73
South Africa recycling waste tyres for other applications such as rubber crumb, mats and
sandals[92]. Major tyre companies like Goodyear and Firestone have invested in pyrolysis
but could not find markets for the by-products and also failed to integrate the venture into
their core business[93].
The main barriers for the development of tyre pyrolysis processes on a commercial scale are:
markets for pyrolytic char are presently not sound. Carbon black char is a fine particulate
composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates,
and silicates. Its application as virgin carbon black is very much restricted since it contains a
lot of impurities ±10%[88] and can only be used as low quality grade carbon black. Similarly
the use of char as activated carbon requires upgrading techniques to increase the surface area.
Reference[75] has shown that tyre pyrolysis oil can be used as a chemical feedstock to
recover valuable chemicals such as limonene. However, waste tyre oils are a complex
mixture of organics and the separation of these compounds to pure products can be costly.
75
The project is a desktop study which involves critical literature analysis, evaluation of waste
tyre treatment options, in depth studies of the pyrolysis process, socio-economic and
environmental analysis of waste tyre pyrolysis as well as pyrolysis plant model construction.
Fig.3.1 shows the steps which were followed to achieve the research objectives.
Fig. 30 Project route map
3.1 Project objectives:
Environmental and socio-economic impact of using waste tyre derived oil and carbon
black as alternative green fuels.
Pyrolysis products market survey.
Development of business model including costing, procurement, installation,
commissioning and operation of the pyrolysis plant.
Analysing the role played by informal and formal sectors in waste tyre management.
Assessment of the socio-economic and market opportunities for energy recovery from
waste tyres.
3.2 Research Methods
3.2.1 Interviews
Telephonic and personal interviews with waste tyre management personnel were conducted.
These gave insight on the current and future waste tyre management strategies in South
Africa. This covered governmental, communities, non-governmental and private sector
organizations. The interviews assisted in data collection and feasibility studies of operating a
waste tyre pyrolysis plant in South Africa. These interviews focused particularly on the
LITERATURE AND DATA
COLLECTION
CONCLUSIONS AND RECOMMENDATIONS
GENERAL DISCUSSIONS ,
MODEL CONSTRUCTION AND
EVALUATION
LITERATURE AND DATA ANALYSIS
UNDERSTANDING RESEARCH
QUESTIONS AND OBJECTIVES
TRIANGULATION PROCEDURE
- Literature reviews
- Site visits
- Personal and telephonic interviews with questionnaires
76
proposed three waste tyre management initiatives namely; REDISA, SATRP and RMI. These
investigations were also extended to waste management corporations, landfill personnel and
waste tyre treatment companies.
3.2.2 Site visits
Visits to waste tyre facilities gave insight on the scale of the waste tyre problem in South
Africa as well the existing mechanisms to address these challenges. Visits to pyrolysis
companies shed some light on the application of waste tyre products. Furthermore, the
information obtained assisted in building the pyrolysis plant model and operation.
3.2.3 Questionnaires
Questionnaires gave insight on waste management practices in South Africa, stakeholders in
waste management. Tables 3.1 to 3.4 show examples of questionnaires used in this study.
Table 3.1
Questionnaire: Pyrolysis plant
1 What is the capacity of the plant?
2 What are the process operating conditions?
3 Is it possible to integrate the process with other feed stocks?
4 What is the composition of the final products
5 Was feed material ever in short supply
6 Do markets exist for their final products?
7 Do they further process their primary products
8 Does the plant make profit?
9 Is the company aware of the REDISA plan, if yes, is there any cooperation?
10 Does the process comply with the air emission standards listed in the
National Policy for Thermal Treatment of General and Hazardous Waste?
Is the pyrolysis feasible, sustainable and profitable in Gauteng, South Africa?
Table 3. 2
Questionnaire: Public/Community
1 How do waste tyres affect the community‟s health and environment?
2 Do local municipalities have any collection mechanism for waste tyres?
3 Do waste tyres add value and can they be a source of income?
4 If yes to question 3, which is the most valued component part of the tyre?
5 Is the public aware of any waste tyre integrated waste management plan?
6 Are there any waste tyre recycling stations nearby?
7 Do communities know about the REDISA plan?
77
Table 3. 3
Questionnaire: Landfill sites
1 Do their landfill sites accept waste tyres?
2 If yes to question 1, how much is the disposal fee?
3 If yes to question 1, what do they do with the tyres after collection?
4 Are the landfill operators aware of the REDISA Plan?
5 Do waste pickers play any role in the recycling of waste tyres?
6 What are the health and environmental implications for accepting waste tyres?
7 Are there any mechanisms used for the handling of disposed waste tyres?
Table 3.4
Questionnaire: Government/Local municipalities
1 What are some of the waste tyre management practices offered by local governments?
2 Is there sufficient waste tyre management information being distributed to the general
public?
3 If yes to question 2, does the public know about the REISA Plan?
4 What is the main purpose for the existence of the REDISA plan?
5 How do local governments perceive technologies such as waste tyre pyrolysis?
3.2.4 Literature Analysis
A comprehensive literature study was carried out using reliable sources such as scientific and
research journals; refereed and peer reviewed conference proceedings; patents and companies
technical information. This helped in identify missing gaps and locating this work within the
broader field of study. This also helped in understanding concepts and operation of a waste
tyre pyrolysis plant.
3.2.5 Model Construction
Cost of equipment and operation facilities are fundamental in developing a feasible waste
tyre pyrolysis model. Two approaches were used to obtain the required information namely:
Engineering cost indices were used to estimate recent equipment prices. Operating pyrolysis
plants and their suppliers were used for costing equipment. Engineering rates for services
were obtained from the Engineering Council of South Africa (ECSA).
79
4.1 Role Played by Informal and Formal Sector in Waste Tyre
Management
Through literature analysis, questionnaires, site visits as well as personal and telephonic
interviews the research found several key participants in waste tyre management. These
include municipal governments, the informal private sector, community based organizations
and non-governmental organizations.
Recycling is a waste minimization option. Waste tyre recycling and resource recovery can
effectively reduce the amount of waste tyres disposed to landfills and open fields; they also
have the added benefit of conserving natural resources. Waste tyre recycling initiatives can
reduce land and air pollution through burning, manufacturing costs, litter and scavenging at
landfill sites. Employment opportunities can also be created through recycling[94]. The waste
stream‟s composition in an area reflects the community lifestyles and status. This can widely
vary from urban to rural areas and from higher to lower income communities, Fig.4.1. The
waste stream composition is influenced by disposable income. Waste tyres are predominantly
generated in high income areas as they afford luxuries such as multiple motor vehicles.
Fig 4.1 Waste streams in different communities [95]
4.1.1 Municipal Governments
Local municipal governments play key roles in the setting-up and operation of waste
management systems. Most urban authorities in both industrialized and developing countries
are empowered and tasked by central government to protect the rights of the citizens, provide
0
10
20
30
40
50
Per
cen
tage
(by m
ass)
of
tota
l w
aste
qu
anti
ty
Low density, higher income area High density, lower income area
80
waste services and to serve the common good[96]. They have to implement laws and
regulations in order to fulfil their constitutional obligations. The characteristics distinctive to
local governments when fulfilling their waste tyre management responsibility include
(i) mandatory obligation
(ii) use of public funds to achieve their waste tyre management objectives
(iii) regulating or contracting the private sector
(iv) political concerns.
The South African Constitution assigns responsibility for refuse removal, refuse dumps and
solid waste disposal, such as waste tyres, to the local government. District and Local
municipalities have different roles and responsibilities but also complement each other as
outlined in the Municipal Structures Act[97].
4.1.2 The Informal Private Sector
The term “informal private sector” refers to unregistered, unregulated or casual activities
carried out by individuals and/or family or community enterprises engaging in value-adding
activities on a small-scale with minimal capital input, using local materials and labour-
intensive techniques. The informal sector does not pay tax, has no trading license and is not
included in the social welfare or government insurance schemes[98]. Informal waste tyre
recycling is carried out by poor and marginalized social groups who resort to scavenging for
survival.
Informal activities in waste tyre collection and recycling are often driven by poverty, they are
individually initiated and spontaneously with the sole purpose of survival although aimed at
profit making. Consequently, the choice of waste to be collected is influenced by its value,
ease of extraction and handling as well as the transportation required. Paper, metal and plastic
wastes usually collected from the more affluent residential or industrial areas tend to attract
more attention than tyres. However, tyres are still burnt for steel recovery. Table 4.1 shows
the various individuals contributing to solid waste management.
81
Table 4.1
Role of the informal sector in waste tyre management
Category Role
Street pickers Recovery
Landfill scavengers Recovery
Collection groups Recovery
Dealers, neighbourhood dealers or buyers Buying (retail)
Small-scale entrepreneurs Buying , trading
Large-scale entrepreneurs Buying and large-scale processing
technology
Although waste pickers are self-employed, it is important to note that the informal economy
is linked to the formal economy as it produces for, trades with, distributes for and provides
services to the formal sector. In many countries such as Brazil, Argentina, Colombia and
Bangladesh, waste pickers are officially recognized. For example, since 2002, waste pickers
have been recognized in the Brazilian Classification of Occupations (CBO)[99]. Thus, waste
tyre management in South Africa needs to be fully integrated. Informal participants
(scavengers) need to be identified, recognized, trained and integrated into the formal waste
tyre management industry.
The recycling network takes the form of a hierarchy shown in Fig. 4.2[100]. The higher a
secondary raw material is traded, the greater the added value it possesses. Informal recyclers
tend to occupy, and are restricted to, the base of the secondary materials trade hierarchy and
this significantly reduces their potential income.
An estimated 88 000 South Africans currently earn a living through waste recovery [101].
Waste picking offers individuals a means to make a living regardless of age, level of
education or skills. Waste pickers contribute to higher levels of recycling within cities and
towns, and help to divert waste from landfills. Since they are linked to the formal sector, their
activities are subordinate to and dependent on the formal sector recycling companies while
waste picking is at the bottom of the recycling hierarchy. The Marie-Louise and Robinson‟s
Deep landfill sites, in the Gauteng region, accommodate waste pickers into their sites. Their
waste management is well organized with representatives. The waste pickers are responsible
for securing formal recycling companies themselves for the collection of their end-products.
82
Fig. 4. 2 Hierarchy of informal sector recycling
Handling waste poses many health risks to workers. These are even greater for informal
workers due to their daily unprotected exposure to contaminants and hazardous materials.
Despite the fact that waste pickers are solely responsible for the risks that their activities pose
to their health, municipalities assist them by providing protective gear to minimize those
risks[102]. Even though the amount of waste they recycle is not formally recorded, it is
believed to range between 5% and 7% of South Africa‟s yearly recycled waste[103].
4.1.3 The Formal Private Sector
This sector includes private corporations, institutions, firms and individuals operating
registered and licensed businesses with organized labour, capital investment and modern
technology[98]. This sector is motivated by making profit. The formal private sector is
involved in wide-range of waste management activities varying from waste collection,
resource recovery, incineration and landfill operation of all waste assortments, including
waste tyres. Its participation can be through entering into waste management contracts with
municipalities and individuals as well purchasing the recovered waste tyres. The formal
private sector is characterized by:
83
1) the potential for profits
2) use of private resources and
3) municipal regulation.
4.1.4 Community Based Organizations (CBOs)
The community and its representatives have a direct interest in waste management, as
residents, service users and tax payers. Communities in low-income areas generally receive
minimum services with regards to public transport, electricity, sanitation, drainage, and waste
removal[104]. Sometimes these communities take the initiative to organize themselves into
Community Based Organizations (CBOs) with the aim to self-help and improve their living
conditions. CBOs may receive external assistance in the form of technical and/or financial aid
from various agencies. Groups of citizens, including those from middle and high-income
areas, may start CBOs to improve waste management in their neighbourhood. Middle and
high-income communities generate more valuable waste compared to the poorer areas. CBOs
mainly participate in primary waste collection and separation at source initiatives.
4.1.5 Non-Governmental Organizations (NGOs)
NGOs are diverse organizations such as churches, universities, labour, environmental and
lobbies as well as donor organizations. They are generally intermediate organizations linking
communities and municipalities which are not directly involved in community waste projects.
NGOs, besides advocating are also involved in awareness-raising, support and decision
making. They can advocate interests on a larger scale than the single community, provide
support and advice to CBOs as well as marginal groups in the society, such as scavengers and
street children. The role of NGOs as partner organizations in waste management ranges from
serving as umbrella organizations under which CBOs operate, to providing a channel for
donor financing. CBOs and NGOs are motivated by a selfless desire to improve waste
management for communities and function outside the formal decision making structures of
municipal governments.
The following are a number of NGOs that are involved in environmental management,
including waste tyres, and conservation: (i) The Institute of Waste Management of Southern
Africa (IWMSA), is a multi-disciplinary non-profit association that is committed to
supporting professional waste management practices. (ii) The Wildlife and Environment
Society of South Africa (WESSA) is a South African environmental organisation with a
mission to implement high impact environmental and conservation projects which promote
84
public participation in caring for the Earth. With a remarkable 87 year history, WESSA
critically focuses on life-supporting eco-systems such as water, energy and biodiversity. (iii)
Earthlife Africa is a non-profit organisation, founded in Johannesburg, South Africa, in 1988.
The organisation‟s main mission is to encourage and support individuals, businesses and
industries to reduce pollution, minimise waste, and thus protect our natural resources.
4.1.6 Key issues and constrains
There are several fundamental constraints that hinder the development of inter-sectorial
partnerships among municipal governments, the formal private sector, the informal sector as
well as non-governmental and community-based organizations, such as financial constraints.
For all stakeholders, financial problems cover (i) for the municipal governments, constraints
on the use of taxpayers' money (ii) for the formal private sector, constraints on capacity,
credibility, liability and resilience (iii) for the informal private and community sectors,
generally marginal access to social institutions and limited access to finance. Sectorial
cooperation is hindered by the lack of belief in the legitimacy of other partners or the fear that
partnerships may disrupt the status quo, especially for marginal actors such as informal sector
entrepreneurs.
4.1.7 Informal and Formal Sector Integration
The income and living conditions of informal waste workers vary significantly, the majority
is confronted with extremely hazardous working and living conditions. They generally lack
sanitary services, health care and social benefits. Child labour is very frequent, and life
expectancy is low. The integration of the informal sector will assist scavengers to gain access
to personal protective gear and health care services. This will also reduce child labour as a
result of the stringent laws and regulations governing the formal sector. The informal sector
can achieve high waste tyre recovery rates of up to 80%[105] as the ability to recycle is vital
for their survival. A variety of recyclables are segregated and processed in accordance with
new demands and technological advancements in the recycling industry. However, a drop in
waste recovery rates was witnessed in Egypt following the introduction of the private sector
involvement in solid waste collection[106] indicating the significance of the informal sector
in running efficient recycling schemes. The diversion of waste from landfills through waste
minimization and recycling is a national policy objective. In response, the National Waste
Management Strategy (NWMS)[31] emphasizes the need for integrated waste management,
which implies coordination of functions within the waste management hierarchy. The
Department of Environmental Affairs has been designated as the lead agent for integrated
85
waste management. In addition, it is anticipated that the promulgated Waste Act (Act 59 of
2008) will address the various short falls previously discussed above. The main participants
in the waste sector including the management of waste tyres are outlined in Table 4.2[107].
Table 4.2
Main players in the South African waste sector
Type Name of Organisations Roles and Functions
National Department of Environmental Affairs Policy development
Government Department of Co-operative Government and Traditional Affairs Setting National Standards and
Targets, Department of Health,;Department of Transport, Department of Trade
and Industry; Department of Water Affairs; Department of Agriculture
Advisory, Regulation and
Inspection.
Forestry and Fisheries; Department of Mineral Resources Department of Energy
Provincial Provincial Departments dealing with Environmental Affairs Standards and Targets,
Authorisations,
Government Advisory, Regulation (e.g.
permitting of all general waste sites)
Local Metropolitan municipalities, District municipalities, Local municipalities Waste service delivery
Government South African Local Government Association (SALGA) Planning, Waste Disposal
Associations and Institute of Waste Management of South Africa (IWMSA) Networking
organisations National Recycling Forum (NRF), Health Care Waste Forum Information sharing
active in the Packaging Council of South Africa (PACSA), Recycling Action Group
(RAG)
Capacity building
waste industry Plastics Federation, Paper Recycling Association of South Africa
(PRASA)
Electronic Waste Association of South Africa (eWASA) PET Plastic Recycling South Africa (PETCO)
Buyisa-e-Bag, The Glass Recycling Company
Collect-a-Can, SAPRO, Recycling Association of SA (RASA)
Responsible Packaging Management South Africa
Recycling Industry Body (RIB), Rose Foundation (oil recycling)
Tyre Recycling Association, Scrap metal Association
NGOs WESSA, WWF,Groundworx, Earthlife Africa, Other Awareness raising
Clean-up campaigns Watchdogs
Waste Varying in size from one man contractors to large companies employing
more than 1000 people.
Re-claimers, Collectors,
Recyclers,
Contractors Operators of waste, management facilities, Treatment and safe
disposal of waste
Industry Any manufacturing or recycling plant, Energy from waste plants Recycling of recovered materials or waste
Professional Various firms Planning, design, construction,
Service Providers monitoring and auditing
Suppliers Various firms Suppliers of equipment and
materials
including: Vehicles, Compactors Geotextiles, Receptacles,
Containers,
Bin liners, Others Academia Universities, Science Councils Research and Development
86
4.2 Socio-Economic Impact of Using Tyre Derived Products
For the past decades, coal has been the primary source of fuel in most world countries
including South Africa. This was so because of its ample availability and lower price.
However, the use of conventional sources of energy such as coal and wood is being
discouraged globally due to the environmental and health risks they pose. This section
discusses the use of waste tyres which are readily available and pilling up in landfill and
dump site all over South Africa as an alternative source of energy.
Waste generation and energy shortages are the two major challenges in South Africa in
addition to other problems such as job creation and service delivery. The government and
private sector are under pressure to find effective and sustainable remedial measures to these
problems. South African policy makers have long been aware that the country was facing
impending power shortages. The 1998 White Paper on Energy Policy warned that power
shortages would become evident by 2007 and that to avoid a situation of demand exceeding
supply, a decision on supply-side investments would need to be made by the end of 1999[94].
Despite having been forewarned, South Africa now finds itself in a situation of power
shortages, load-shedding and power rationing.
4.2.1 Land filling ban of waste tyres
This section discusses the environmental and socio-economic impacts of the prohibition of
waste tyres disposal at landfill sites. A total ban on landfilling or an obligatory requirement
for the recycling of scrap tyres would require a long transition period and substantial effort to
create options for recycling and recovery. As a result, this may still result in a significant
amount of stockpiles, particularly in remote and rural regions. There is a huge transportation
costs that will have to be considered for the nation-wide collection and storage of waste tyres
in designated locations, as provided by the REDISA Plan.
From a South African point of view, majority of prominent landfills around the Johannesburg
district, such as Mariel Louise and Robenson‟s deep amongst others, have accepted the waste
tyre ban. These landfills do not accept any assortment of tyres in their site due to
environmental regulations. However, landfill sites such as the Mogale City landfill and other
surrounding sites situated in the west of Johannesburg accept waste tyres despite the ban, Fig.
4.3. The Mogale City Landfill site charges a fee of R13.00 per passenger tyre and R26.00 per
heavy commercial or agricultural tyre as shown by Table 4.3. In addition the landfill site
allows individuals to collect tyres from the site for recycling applications, Fig.4.4.
87
Fig 4. 3 Waste tyres disposed at the Mogale City landfill site
Table 4.3
Mogale City waste disposal rates
Waste type Quantity Price
Debris disposal fee, contractors and businesses Tonne R 136,98
Disposal of clean compostable refuse by Mogale city residents and
contractors in excess of 500kg Tonne R 83,32
Disposal of general and non-hazardous solid waste by any person outside the
boundaries of Mogale City Tonne R 166,58
Building rubble (less than 300mm in diameter) free R 0,00
Re-usable material free R 0,00
Tyres-rim size up to 40cm in diameter Per tyre R 12,96
Tyres-rim size greater than 40cm in diameter Per tyre R 25,91
Fig 4. 4 Tyres collected by alternative tyre manufacturers
88
4.2.2 The environmental impact
Local government
The major environmental benefit for the banning of waste tyres in landfills is the potential
improved use of landfill space. Based on the latest assessments, the remaining lifespan of
most landfills, when no additional diversions from land filling are implemented over and
above current diversion methods and excluding private landfills, is between 12 to 14 years
counting from 2010 onwards. South Africa‟s remaining landfill span is below the
international benchmark of banked landfill space of 15 years[108]. On the contrary, the ban
will also promote the implementation of stringent land filling laws.
Tyre recycling industry
The ban will force the tyre industry to find alternative methods for the disposal of their
products when they have reached their end use. This will encourage the tyre industry to
participate in tyre recycling schemes as well as energy recovery initiatives.
Community
The legal or illegal disposal of waste tyres poses severe health issues and fire hazard
concerns. However, due to the proposed ban, the environmentally acute effects of tyre land
filling and illegal disposal will be remedied through the introduction of waste tyre
management strategies, for example, as proposed in the REDISA Plan.
State government
Recycling and energy recovery initiatives will assist in improving waste tyre management as
well as environmental regulations and laws for this waste type.
Manufacturing or retail sectors
The ban will promote improved management strategies for landfills
4.2.3 Social impact
Local government
The ban will possibly increase employment particularly in the management and operation of
stockpiles, small micro and medium enterprises (SMMEs), and boost the local civil
engineering industry as well with regards to the construction and infrastructure management
of the stockpiles. In addition, relating to the REDISA Plan, the actual transportation process
of tyres to storage facilities will marginally provide employment to the transporters.
Tyre recycling industry
89
Employment will be created through tyre recycling and energy recovery initiatives. With
sufficient research in waste to energy, waste tyres can be thermally processed to produce
Tyre Derived Fuel (TDF) for commercial or industrial use.
Community
Poor communities relying on steel recovery from waste tyres, Fig 4.5 and 4.6 perceive the
ban to be undesirable and not beneficial to them as this is their source of income.
State government
An increase in employment in the recycling industry will be experienced and will result in
both government and private institutes willing to fund waste tyre initiatives.
Manufacturing or retail sectors
The collection of tyres from remote rural areas will result in increased economic
opportunities.
4.2.4 Economic impact
Local government
The ban on the landfilling of waste tyres will have a financial impact in the economy
through increased costs of enforcement to prevent illegal dumping, but this can be
remedied by introducing incentives to prevent illegal dumping through basic waste
management education practices.
Tyre recycling industry
The waste tyre ban will promote growth and business opportunities resulting in the
development of an integrated tyre manufacturing, recycling and energy recovering
industry. In addition, there will be a guaranteed supply of waste tyres due to the
possible tyre production competitiveness.
State government
Steady economic growth will be experienced due to the increase in waste tyre business
competitiveness, job creation and capacity building.
Manufacturing or retail sectors
The ban on waste tyre land filling will promote the production of alternative fuel for
some sectors, such as agriculture.
90
Fig. 4.5 A pile of steel wires from burnt tyres
Fig. 4.6 A young steel wire seller from Soweto, Gauteng.
91
Waste tyres have the potential to be utilised as energy source as well an alternative petroleum
fuel source. Pyrolysis and gasification are some of the technologies which can be employed
to achieve this objective. The waste tyre recycling industry has proven to be fairly ineffective
in South Africa with only a 4% waste tyre recycling rate in 2011 and lower in the previous
years[7]. Recycling of waste tyres has the potential to address both environmental and energy
challenges as well as contributing to economic growth. In addition, the South African
government recognizes the conversion of waste to energy in its plans and future
strategies[27]. A waste tyre management plan such as the gazetted REDISA Plan, which is
awaiting implementation, is expected to address the problem at national level.
Progress has been made with a range of energy efficiency initiatives such as the South
African National Energy Development Institute (SANEDI); a Schedule 3A state owned entity
that was established as a successor to the South African National Energy Research Institute
(SANERI) and the National Energy Efficiency Agency (NEEA). The key function of
SANEDI is to direct, monitor and conduct applied energy research and development,
demonstration and deployment as well to undertake specific measures to promote the use of
green energy and energy efficiency in South Africa. SANEDI is involved in numerous
institutional research projects and programmes in green energy engineering. These can
promote South Africa‟s development, increase human capacity and eventually lead to
commercialization of the intellectual property. Other projects include the Industrial Energy
Efficiency Improvement Project, South Africa; the Energy Efficiency Target Monitoring
System (EETMS) and the South Africa Germany Energy Project (SAGEN).
4.2.5 Tyre Derived Fuel (TDF) applications
Scrap tyre markets are mature and stable in most developed countries such as the USA. Scrap
tyres are recognized as abundant valuable resources and are used in a number of applications,
including tyre derived fuels or products. Generally, in South Africa the market for tyre-
derived products is much larger than the market for liquid products, such as oil. Tyre derived
fuel has a higher heating value than coal and wood, Table 4.4[109].
92
Table 4.4
Calorific values of a number of common fuels
Fuel Calorific Value (MJ/kg)
gas 84.7
diesel oil 45.5
scrap tyres 32.5
coal 30.2
coke 26.7
wood 12.4
The following are the existing TDF applications that have been successfully implemented
elsewhere, and these can be used as bench marks for the South African scenario in dealing
with the waste tyre problem.
a) Cement Manufacturing
Tyres can be alternatively utilized in cement kilns and power plants. The use of scrap tyres in
cement kilns is increasing and is by far the leading thermal technology used for scrap tyres
management[110]. When the complete ban of tyres to landfill came into effect in 2006 for
most European countries, the use of tyres in cement kilns increased and this was further
strengthened by the increase in fossil fuel prices[111]. Most of the leading cement companies
such as Lafarge, Holcim, Cimpor, Heidelberg, Taiheiyo, Italcementi, Aalborg Portland, and
Castle Cement have plants around the world that are currently co-combusting tyres[111].
Lafarge Cement‟s overall manufacturing capacity is in excess of 6 million tonnes per annum
in the UK with 40% accounting for their domestic market in 2003[112]. Scrap tyres along
with other alternative fuels, such as recycled liquid fuels, form the mainstay of Lafarge
Cement‟s UK strategy to increase its waste tyre utilisation as an alternative source of energy
from less than 3% in 1999 to an excess of 20% in 2006[113].
Local cement companies such as Pretoria Portland Cement (PPC) are also in the investigation
stages of incorporating waste tyres as part of their fuel source. This proposed project is
however still in the initial stages with full scale implementation expected early 2014[114].
Cement manufacturing companies use whole tyres and TDF to supplement their primary fuel
for firing cement kilns. Several characteristics make scrap tyres, either whole or shredded, an
excellent fuel for the cement kiln. The very high temperatures and long fuel residence time in
the kiln allow complete combustion of the tyres, without the production of odours or
emissions during the combustion process. The ash forms part of the final product and hence
93
there is no waste. The steel component replaces the iron required in cement manufacturing.
The use of waste tyres in cement kilns results in higher production rates, lower fuel costs and
improved environmental quality, considered as advantages, while the only disadvantage is the
possible emission of carbon dioxide (CO2)[111].
b) Pulp and Paper Industry
The pulp and paper industry uses tyre-derived fuel as a supplement to wood waste, the
primary fuel used in pulp mill boilers. The technology has been in continuous use in the
United States since the early 1980s. The heating value of the wood waste fuel ranges from
about 8,334.5 to 9,495 kJ/kg on a dry basis. Tyres facilitate uniform boiler combustion, and
help overcome some of the operating problems caused by fuels with low heat content,
variable heat content and high moisture content. The consistent heating value, low moisture
content of TDF and its low cost in comparison to other supplemental fuels make TDF an
attractive fuel in the pulp and paper industry. One of the key advantages for using TDF in the
pulp and paper industry is that it increases combustion efficiency. It also lowers energy costs
and improves product quality[115].
c) Industrial Boilers
In industrial boiler application, combustion of TDF generates energy in the form of steam
and/or electricity, replacing other fuels such as coal. This also reduces pollution. TDF
combusted industrial boilers emit fewer oxides of sulphur and nitrogen compared to coal.
TDF operated systems offer higher heating value, lower emissions, competitive cost, and
ability to create stable operating conditions in the boilers. This makes the use of TDF
attractive in power generation. However, TDF is not compatible with all boilers as clumping
and clogging can also occur. Also, if the metal in waste tyres is not recovered, it causes
disposal challenges.
4.2.6 Waste tyre pyrolysis markets
Over the last two decades there has been a growing interest in using tyre-derived fuels.
Initially this interest was driven by concerns for potential shortages of crude oil, but in recent
years the ecological advantages of alternative fuels have become an even more important
factor. Tyre derived-oil can be easily transported and stored. However, the properties of
waste tyre-oil also result in several significant problems during its use as a fuel in standard
94
equipment such as boilers, engines and gas turbines. Poor volatility, high viscosity, coking,
and corrosiveness are probably the most challenging and have so far limited the range of its
applications[116].
Tyre Derived Oil Applications
Waste tyre pyrolysis produces gaseous products such as synthesis gas. This gas can be used
for fuel, electricity, and chemicals. When later condensed, the gas generates an oil-based
liquid containing up to 30-50 % of the tyre feedstock[117]. Outlined below are some of the
pyrolysis gas applications:
Chemical feed stock: Pyrolysis of waste tyres produces gases such as benzene; toluene and
xylenes which are very important chemicals. They are used as primary feed stocks to produce
plastics, resins, fibres, surfactants, dyestuffs and pharmaceuticals, and long-chained alkyl
benzenes that can be used as surfactants. Xylenes are important industrial chemicals used to
produce plasticizers and dyes; m- and p-xylene derivatives are used on polyesteric resins and
in the fibre industry. Toluene has a wide range of applications but is mostly used for
pesticides, dyestuffs, surfactants and solvents production[61], such as limonene[2, 68, 72].
Industrial and commercial: Waste tyre derived liquids have properties resembling petroleum
fractions. The oil produced by pyrolysis technology is the fuel oil that is widely used for
industrial and commercial purposes such as industrial furnaces, foundries and boilers in
power plants, due to their higher calorific value, low ash, residual carbon and sulphur content.
[116]. The oil can be a substitute for diesel, heavy fuel oil, light fuel oil or natural gas in
industrial, commercial and residential boilers. Furnaces and boilers are devices commonly
used for heat and power generation. They are usually less efficient than engines and turbines
but they can operate with a great variety of fuels ranging from natural gas and petroleum
distillates to sawdust, coal/water slurries and oil seems. For a fuel to be suitable for boiler
application, it should have consistent characteristics, environmentally acceptable and produce
limited emissions.
Use as automobile fuel: High viscosity, delayed ignition time, lower heating value,
corrosion and solid content hinder the utilization of pyrolysis oil as automobile fuel. Work
has been done on the improvement of pyrolysis oil for use in modern combustion devices. In
this regard it has been found that pyrolytic oils require preliminary treatments such as
95
decanting, centrifugation, filtration, desulphurization, and hydrotreating before application as
fuels [6, 10, 68, 118, 119].
Bi-fuelling or blending: Viscosity and sulphur content of crude TDO influence engine
performance and emissions, hence affect the use of tyre derived pyrolysis oil as a blending
fuel. The high viscosity of the fuel leads to problems over time such as carbon deposit. The
high carbon residue content and high viscosity arise from large molecular mass and chemical
structure of the oil. The high carbon residue is responsible for heavy smoke emissions. The
treated pyrolytic oil could be used alone or blended with other fuels such as CIMAK-B10
diesel fuel, which is basically 10% biofuel, in this case 10% pyrolysis oil, and 90% petroleum
fuel[120]. The addition of pyrolytic oil to this kind of diesel fuel reduces the viscosity of the
resulting blend. Consequently, the atomization will be improved, ensuring a complete
burnout of the fuel. Based on its fuel properties, tyre-derived pyrolytic oil can be considered a
valuable component for use with conventional fuels.
The South African Market
The waste tyre pyrolysis process is still a relatively new concept in South Africa. It has not
been fully explored regardless of the fact that several attempts have been made to operate
profitable plants which adhere to environmental laws. Such attempts include the Pretoria
based pyrolysis plant (Innovative Recycling (Pty) Ltd) which used to process 25 tonnes of
waste tyres daily. The company capitalized on the opportunity of using excess waste tyres by
erecting a waste rubber and plastic conversion to fuel plants. The plant ceased operation
because of its failure to adhere to environmental regulations and laws.
Currently, there is an operating pyrolysis plant in Rosslyn, Pretoria. This plant has been in
operation on and off since March 2012. The plant processes 10 tonnes of waste tyre at a batch
operation of 11 hours per day. It produces 40% pyrolysis oil, 30-35% carbon black, 15% steel
cords and 10% uncondensed gases. The oil is sold as crude for industrial applications. The
pyrolysis oil specifications and properties should be measured against local and international
oil standards before application. For comparison purposes, two samples were analysed and
compared with diesel standards. The first sample was obtained from the Rosslyn pyrolysis
plant and the second from Pace Oil (oil refining company). The two samples were analysed in
two South African Bureau of Standards (SABS) approved laboratories and the results are
shown in Table 4.5.
96
Table 4.5
Pyrolysis oil specifications
Test Description Test method Specification [Milvinetix] [Pace oil]
Density @20oC, kg/l ASTM D4052 0.800 Min 0.895 0.8772
Viscosity @40oC, cSt ASTM D445 2.2-5.3 2.868 2.1
Flash point, oC ASTM D93 55 min ˂25 26
Water Content, ppm ASTM 6304 500 max 673 600
Sulphur content, ppm ASTM D4294 500 max 8100 12400
Total Contamination number,mg/kg IP 440 24 max 31 38.6
Distillation oC: 90% Recovery, oC ASTM D 86 362 max 378.8 360
Micro Carbon Residue ASTM D4530 0.2 max 4.5 2
Cetane Index ASTM D4737 51 min 32.01 34.2
The pyrolysis characteristics in Table 4.6 conform to the South African National Standards
(SANS) specification (SANS 342:2006)[121] for density and viscosity. In addition, the Pace
oil sample was within the distillation recovery SANS specification. This is important as high
boiling components favours the formation of solid combustion deposits and hydrocarbon
mixtures producing potentially explosive vapour[122]. The oil shown in Table 4.6 has a low
flash point requiring specific storage to meet insurance and fire prevention requirements.
Additives and blending can increase the flash point and also reduce the water content[123].
The two oils contained excess contaminants although there was little metallic contamination.
The oils are out of specification with regard to the octane index and micro carbon residue
limiting their application. The Milvinetix oil is not further treated for economic reasons[91,
124] thus it is sold in its crude form. When comparing the 2 samples, it is evident that both
samples do not meet the SANS standards for majority of the tests conducted, however, the
Pace Oil sample seems to be within the distillation: recovery limit.
Pyrolysis oil small scale studies:
References[125] focused on the removal of sulphur compounds using acidic and basic
treatments at varying concentration as well as filtration. Crude pyrolysis oil was distilled at
varying temperatures and the results are shown in Table 4.6. Fig. 4.7 shows that the
temperature range 150-200oC is the most satisfactory for the distillation of pyrolysis oil as the
distillation temperature affects the desulphurization process. Table 4.6 shows the properties
of distilled pyrolysis oil at 150-200oC. Acid treatment of the distilled oil produced better
oxidative desulphurization (ODS) compared to base treatment, Fig 4.7, reducing the sulphur
concentration from 9106 to 4807ppm with 10 (v/v%) H2SO4.
97
Table 4.6
Proximate analysis of crude and distilled pyrolysis
Parameter
Crude Pyrolysis oil Distilled Pyrolysis oil
(150-200oC)
Density @ 20oC (Kg/L) 0.9265 0.835
Viscosity @ 40oC (cSt) 10 0.9
Sulphur (ppm) 9106 7054
Flash Point (oC) 94 26
Total Contamination (mg/kg) 143 4.3
Fig 4.7 Comparison of the sulphur content with varying temperature ranges.
A carbon black sample was also collected from the Pretoria Pyrolysis plant and analysed. The
sample has a high calorific value making it possible for fuel application. However, the sample
did not conform to the ASTM standards for ash and volatile matter content, Table 4.7. This
means that the sample cannot be considered for industrial use in its virgin form after
pyrolyzing waste tyres. Hence further purification of the carbon black is required to improve
marketing and standardisation.
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0150-200
150-200200-250
200-250250-300
Before ODS
ODS H2S04
ODS NaOH
Sieved ODS
NaOH Sieved ODS
H2SO4
ODS NaOH
Su
lph
ur(
pp
m)
Temperature Range(Degrees Celcius)
98
Table 4.7
Pyrolysis carbon black specifications
Test Description Test method (SA) [Milvinetix] ASTM Test
method [126]
Calorific Value SANS 1928:2009 31.18%
Moisture Content
SANS
15325:2007 1.30%
Ash content ISO 1171:2010 14.50% 0.5 % Max
Volatile Matter Content ISO 582:2010 24.30% 0.3% Max
Fixed Carbon By difference 59.90%
Total Sulphur ASTM 4239:2010 2.61%
100
This study assesses the feasibility of constructing and operating a batch pyrolysis plant in
Gauteng. The study focuses on the production of alternative fuels and other high value
pyrolysis products. With the support of the REDISA plan, waste tyres will be collected within
the vicinity of Gauteng and transported to the waste tyre treatment plant.
5.1 Pyrolysis
Waste tyres will be delivered to a permitted waste tyre treatment facility where the tyres are
to be weighed then introduced to the pyrolysis system after shredding. The batch process
takes place in a reactor chamber with feedstock of 7 tonnes per day and average residence
time of 8 hours. An inert gas, such as nitrogen, is used to purge the excess oxygen from the
system. To a large extent, reactor temperature determines the yield of solid, gas, and liquid
pyrolysis products thus; operation at 550oC and ambient pressure allows the production of
45% oil; 5% pyrolysis gas; 35% carbon black and 15% steel wires. Table 5.1 gives the
summary of the effect of operating temperature on product yield [127]
Table 5. 1
Effect of temperature on yield
Operating Temperature Operating Pressure Production Variation
42% Oil
500°C Ambient 52% Solid
6% Gas
50% Oil
600°C Ambient 40% Solid
10% Gas
47% Oil
700°C Ambient 38% Solid
15% Gas
40% Oil
800°C Ambient 29% Solid
31% Gas
5.1.1 Pyrolysis end products
During the course of the pyrolysis process, pyrolytic gas is produced then cooled and further
condensed to form pyrolytic oil. This oil is classified as No. 6 oil which is a thick, syrupy
heavy crude oil and has an acrid smell. To increase the economics of this product, a
distillation step is integrated into the process. This treatment step improves the quality of the
oil, thus increasing the application. The crude pyrolysis oil is distilled to form light tyre
101
derived distillate fuel and residual fuel oil fractions. The residual oil is blended with diesel
while the distillate fraction is utilized in agricultural vehicles. The uncondensed gases are
recycled back to the system for use as fuel to sustain the process. The emissions from the
reactor burners are chemically treated using a gas absorption process.
The solid fractions consist of a mixture of carbon black and steel wires. A magnetic
separation is used to remove ferrous metals to isolate the two components. The carbon black
is further milled in order to obtain different grades and fractions of the char. The following
fractions can be obtained: N220 (24-33nm) used in rubber and rubber products; N770 (70-96
nm) used in paints and pigments; N990 (250-350 nm) used as activated carbon and the
residue fraction can be used for briquettes. The steel component is sold to steel manufactures
or dealers.
5.1.2 Utilities
The process requires process water for cooling (heat exchangers and cooling tower),
condensation as well as carbon black wet grinding. Approximately 8000 litres of water will
be used monthly in the plant. The energy requirement for the plant is 528.58 KW, Table 5.2.
This power is supplied to components such as the tyre shredder, heaters, pumps, control
systems as well as large mechanical and heating equipment. Sodium Hydroxide (NaOH) is
used as a scrubbing reagent at a cost of R7.55 kg per bag. The nitrogen required for the
pyrolysis reactor is estimated to be R687, 79 per 13kg cylinder.
Table 5.2
Total plant energy requirement
Energy type Amount
Heating 250, 41 kW
Mechanical 327, 58 kW
Cooling 129,59 kW
Available fuel energy 179 kW
Energy efficiency 0,75
Total supply 528,58 kW
5.2 Discussions
The economic model is based on a 12 year pyrolysis plant life span consisting of 4 rotating
shifts with 3 operating daily. The treatment facility operates as a batch process 329 days per
year, the remaining days are utilized for maintenance. The available plant capacity is 2546
ton/year. With shutdown time of 36 days/year the allowable plant capacity becomes 2291
102
ton/year shown in Table 5.3. The initial process input assumptions for the project are given in
Table 5.4. A basis of 7 tonnes/day of treated tyres will initially be used; however expansion
of up to 10 tonnes/day is catered for in the plant design. The basis is lower than that of the
Pretoria based pyrolysis plant, 10 tonnes per day; this is due to an already established market
for their end products. Therefore, with growth and standardization of the proposed pyrolysis
end products plant expansion is viable.
Table 5.3
Pyrolysis plant operational assumptions
units
Weight of rim-less tyre
7,75 Kg
Single tyre gate fee
13 R/tyre
Operating hours
328,5 Days/yr
Plant shut down time
36,5 Days/yr
operating shifts
3 per day
Loading cycles 3 Per shift
Table 5.4
Process Input assumptions
Variable Unit Figure
Tyre disposal fee R/day R 1 950,00
power consumption R/Annum R 218 437,27
Water consumption R/Annum R 61 257,60
Treated tyres ton/day 6,98
Annual working hours hr/yr 8760
Down time hr/yr 876
Plant operating time hr/yr 7884
Actual plant capacity ton/hr 2291,2875
Available plant capacity ton/hr 2545,875
Exchange rate R/$ 10,84
R/£ 14
Estimated project period Yrs 12
Actual annual production ton/yr 2291,288
Process Input costs
Power R/kWh 1,258
water R/L 0,02127
Telephone Line R/Annum R 36 000,00
NaOH (scrubber reagent) R/ton R 7 550,00
Nitrogen R/3 kg R 687,79
103
Four income streams will be the core revenues for the project. A tyre gate fee of R13.00 per
tyre is collected. Distilled pyrolysis oil is sold at R9.50 taking into account the 2014 fuel
prices with fluctuation allowance. The oil is mainly sold to agricultural businesses. An
overall revenue of R 310 354, 89 per annum of variable carbon black grades N220, N770,
N990 and briquettes is collected. Lastly, the residual steel wires are sold to appropriate
dealers at a rate of R 2 500, 00 per tonne. The 5% uncondensed gasses are recycled back into
the process. The mass and energy balance with 90% plant capacity for the first 4 years is
given in Table 5.5.
Table 5. 5
Mass and energy balance
Year 0 Year 1 Year 2 Year 3 Year 4
Plant capital factor
90,00% 90,00% 90,00% 90,00% 90,00%
Balances
1. Process inputs
Tyres (Ton/yr)
2291,29 2291,29 2291,29 2291,29 2291,29
Water (m3/yr)
2628 2628 2628 2628 2628
Electricity (KW/yr)
218437,27 218437,27 218437,27 218437,27 218437,27
NaOH (ton/yr)
8212,5 8212,5 8212,5 8212,5 8212,5
nitrogen (l/yr)
4270,5 4270,5 4270,5 4270,5 4270,5
2. Process outputs Actual
output
Tyre derived fuel (ton/yr) 45% 1031,07938 1031,079 1031,0794 1031,0794 1031,079
Carbon black, Char (ton/yr) 35% 801,950625 801,951 801,95063 801,95063 801,9506
Steel cords (ton/yr) 15% 343,693125 343,693 343,69313 343,69313 343,6931
Uncondensed Gas (m3/yr) 5% 114,564375 114,564 114,56438 114,56438 114,5644
2291,2875 2291,2875 2291,2875 2291,2875 2291,288
The order of magnitude estimate method was used for major equipment costing. Using
project evaluation methods, represented by equations 5.1 to 5.8, it was found out that the
project is worth investing into with a projected payback period of approximately 5 years, Fig
5.1. The project requires a capital incentive of R 10, 173 075.00 during year 0, this cost
includes the cost of all major equipment, plant assessment costs, building and structure,
engineering and construction as well as other costs such as contingency fees and office
utilities, Table 5.6. The required capex is solely funded by a financial institution with a pay
period of 4 years based on an annual interest rate of 10%. A tax rate and vat rate of 29% and
14% respectively are taken into account for the annual revenues. An annual straight line
depreciation rate is applied over the12 year plant lifespan, Table 5.6.
104
………. (5.1)
………. (5.2)
…………………………………………….....
(5.3)
………………………. (5.4)
. (5.5)
……………………………………………….
(5.6)
………………………………. (5.7)
∑
.……… (5.8)
Fig 5.1 shows a general increasing trend for all the plotted variables (project life, operating
costs, labour costs, net profit after tax and annual revenue) from year 0 to year 12. A steady
increase in the net profit after tax is projected predominantly around year 5; this is due to the
business ending their capex loan repayment period after year 4. This results in the project
accumulating higher revenues annually from year 4 onwards. In addition, a significant gap
between the revenue and annual costs (labour and operating costs) is visible and show a trend
of not intersecting anywhere during the project life, thus indicating a profitable project life.
The plant only breakeven after 5 years due to the high capital investment accompanied by an
annual 10% interest on loan repayment. However due to the availability of raw material at no
cost and the sale of high end products the plant is seen to be highly profitable from there on.
Fig 5.1 also shows stabilisation in the accumulated annual revenue and production costs
towards the end of the project, this is expected as a high increase in revenue is realised from
year 6 onwards.
The net present value (NPV) is also used to determine whether the project is worth investing
into in terms of profit yield and breakeven period. Fig 5.2 shows that the project is worth
investing in due to the positive net present value, this is also depicted in Table 5.7. In
addition, the NPV curve also gives an indication of the projected plant life which agrees very
well with the plotted plant life curve in Fig 5.1. The return of assets (ROA) is also in
105
agreement with the NPV. According to [128] 20 to 30 % of the return of investment (ROI)
can be used as a rough guide for evaluating small projects and the higher a project's return the
more attractive it is. The ROR, defined as the performance of the capital invested, as well as
the ROI are in the 30% range which is in strong agreement with literature.
Fig 5.1 Projected plant life, costs and revenues.
-8000000
-3000000
2000000
7000000
12000000
17000000
22000000
27000000
32000000
37000000
0 2 4 6 8 10 12 14
Val
ue
(R)
Year Project life Operating costs
Revenue Labour costs
Net operating profit after taxes (NOPAT)
106
Fig 5.2 Net present value and depreciation rate
-0,7
-0,6
-0,5
-0,4
-0,3
-0,2
-0,1
0
0,1
0,2
0,3
-R 8000 000,00
-R 6000 000,00
-R 4000 000,00
-R 2000 000,00
R 0,00
R 2000 000,00
R 4000 000,00
R 6000 000,00
0 2 4 6 8 10 12 14
Depreciation Net present value (NPV) Depreciation % ROA(return of Assets)
Table 5.6
Waste tyre pyrolysis project capex
Project Costing
ITEM
No Rental
R 180 000,00
1 PLANT EQUIPMENT COST
DESCRIPTION QUANTITY COST COMMENTS
1,1 Pre-Pyrolysis
1.1.1 Magnetic separator 1 R 56 460 1,1 kW motor, 550kg
1.1.2 Tyre shredding 1 R 211 380 60-80 tyres per hour, 15hp 1.1.3 weighing system 1 R 9 861 2mx1.5m SABS approved. With read out screen
R 277 701
1,2 Pyrolysis
1.2.1 Reaction Chamber 1 R 120 046 D1.4m, L6m, 15KW, 380V, 8-10t/day, Q245/Q345 CSPV
1.2.2 Heat exchanger 2 R 355 525 1:27,5 m2, 177 tubes 20mm o.d, 2.44m L; 2:20,5m2,134 tubes 20mm o.d,2.44m L 1.2.3 condenser 1 R 243 952 38,5 m2, 166 tubes @ 20mm o.d and 3.66m L 1.2.4 Storage tank 2 R 131 000 23000l
1.2.5 cooling tower 1 R 1 125 640 Stainless steel/galvanized steel
1.2.6 pumps 4 R 109 980 carbon steel 1.2.7 Interconnecting pipes and valves R 298 202 carbon steel
R 2 384 345
1,3 Post -Treatment 1.3.1 Distillation column 1 R 291 428 Carbon steel/stainless steel, CC, D=2m, H=4m
1.3.2 Micro ball mill 1 R 839 878 Stainless steel, inc ball liners, 0,019m- 48 mesh, closed circuit with classifier. 0,3 kg/s
1.3.3 Gas scrubber 1 R 685 844 Carbon steel/stainless steel, D=1,5m, H=4m
R 1 817 150
Total equipment R 4 479 196
1,4 Engineering& other services
1.4.1 Plant assessment costs R 604 899
Land and site evaluation
Preliminary plant draughting and layout
Safety, risk and environmental assessment
1.4.2 Building and structure R 1 209 799
Process Building
Maintenance shops
Offices 1.4.4 Engineering and construction
Civil and Construction design R 725 879
108
Fencing
Safety
Structural design and Construction R 967 839 Electrical and controls systems design R 698 879
Project Management R 338 744
1.4.5 Communication R 241 960
1.4.6 Other additional costs R 725 879 Contingencies
Critical standby equipment
Contractor fees
Office equipment and stationary R 5 513 879
TOTAL PLANT COST
R 10 173 075
TOTAL CAPITAL REQUIREMENT R 10 173 075,35
Table 5.7
Plant evaluation calculations
Year Net annual profit Total assets Depreciation Depreciation % ROA ROR ROI NPV
0 0 R 10 671 195,97 R 4 479 195,97 0 0 33,50% 30% 0
1 R -6 428 301,18 R 10 229 768,90 R 689 107,07 0,15 -0,63
R -5 739 554,63
2 R -5 207 945,78 R 16 552 941,81 R 631 681,48 0,14 -0,31
R -4 151 742,49
3 R -3 411 720,79 R 23 635 911,07 R 574 255,89 0,13 -0,14
R -2 428 395,47
4 R -1 232 174,29 R 30 769 420,60 R 516 830,30 0,1 -0,04
R -783 069,04
5 R 1 104 176,82 R 37 967 241,03 R 459 404,71 0,09 0,029
R 626 539,58
6 R 3 717 308,01 R 45 681 920,56 R 401 979,13 0,09 0,08
R 1 883 303,92
7 R 6 818 236,36 R 54 803 826,02 R 344 553,54 0,08 0,12
R 3 084 223,87
8 R 8 987 602,25 R 64 844 604,83 R 287 127,95 0,06 0,14
R 3 629 941,81
9 R 11 557 771,17 R 64 614 902,47 R 229 702,36 0,05 0,18
R 4 167 848,15
10 R 12 684 135,20 R 75 803 323,13 R 172 276,77 0,04 0,17
R 4 083 952,06
11 R 14 340 983,54 R 87 730 811,23 R 114 851,18 0,03 0,16
R 4 122 690,08
12 R 16 223 159,98 R 100 202 235,43 R 57 425,59 0,01 0,16
R 4 164 081,09
R 4 479 195,97
Sum R 12 659 818,94
R 2 486 743,58
5.3 Environmental Impact Assessment
This section presents an evaluation of the environmental impacts of waste tyre pyrolysis
including potential mitigation measures. These impacts include air emissions, liquid wastes,
and solid residues. Generally, the environmental impacts are similar in all three PGL
technologies. When compared to operations that utilize combustion of waste tyres, it is
generally accepted that PGL technologies yield equal or lower environmental risks in most
cases. However, the information available is limited, due to the small number of full-scale
PGL facilities [61]. Exhaust gas clean-up of PGL processes is less compared to incineration,
however, proper design and operation of the process and emissions control systems are
necessary to ensure that all health and safety requirements are met. The control of air
emissions is made less costly and complex for PGL processes compared to incineration
because (a) subsequent combustion of low-molecular-weight gases from pyrolysis and
gasification processes is much cleaner air compared to the combustion of raw feed stocks (b)
pyrolysis and gasification processes use zero or minimum air or oxygen. (c) Pyrolytic gases
are typically in a reducing environment, and can be treated or utilized unlike the fully
combusted (oxidative) exhaust.
5.3.1 Air Emissions
Air emissions may be the greatest environmental concern in PGL operations using waste
tyres. The gases from pyrolysis and gasification processes (and subsequent combustion
processes, if applicable) can contain a variety of air pollutants that must be controlled prior to
discharge into the ambient air. These include particulate matter (PM), oxides of nitrogen
(NOx), oxides of sulphur (SOx), dioxins and furans, hydrocarbon (HC) gases, metals, carbon
dioxide (CO2), and carbon monoxide (CO) [61]. There are many strategies available for
controlling emissions from waste tyre thermal processes depending on the process
requirements and scale of each individual facility.
There are a number of different emission control strategies that can be applied in PGL
processes. An example of a mid-process air pollution control system is the Thermoselect®
process, a high-temperature conversion technology. The company currently has four facilities
in commercial operation worldwide, with three others under construction [49]. The
Thermoselect® process is capable of processing different waste streams, including tyres. The
Thermoselect® process uses gasification for primary processing, but can also be applicable to
high temperature pyrolysis. After completion of the gasification/ pyrolysis stage, the
110
synthesis gas exits the reaction chamber and flows into a water jet quench where it is
instantaneously cooled to below 95o C. The rapid cooling prevents the formation of dioxins
and furans by dramatically reducing the residence time of the synthesis gas at high
temperature. Entrained particles (such as elemental carbon and mineral dusts), heavy metals,
chlorine (in the form of hydrochloric acid [HCl]), and fluorine (in the form of HF) are also
separated out in the quench. The quench water is maintained at a pH of 2 to ensure that heavy
metals are dissolved as chlorinated and fluorinated species, so that they are washed out of the
crude synthesis gas.
Following the quench process, the synthesis gas flows into a demister and then into alkaline
scrubbers, where the remaining particulates and HCl/HF droplets are removed. Then the gas
passes through a desulfurization scrubber for the removal of hydrogen sulphide (H2S) by
direct conversion into elemental sulphur. The scrubber is a packed bed that is sprayed with
scrubbing liquor consisting of water and a dissolved Fe-III chelate that oxidizes the H2S to
elemental sulphur and water. Finally, the gas is dried in a counter current packed bed
scrubber using tri-ethylene glycol liquor. The fully cleaned synthesis gas can then be
conveyed to engines, boilers, or turbines for electricity production. Alternatively, the gas can
be converted to higher molecular weight fuels such as diesel fuel. Other control systems such
as the Exxon thermal de-NOx system for NOx emissions, fabric filters for particulate matter
and wet scrubbers for SOx emissions can be utilized.
5.3.2 Liquid Residues
The primary liquid products from tyre PGL processes are pyrolysis oils and any residual
scrubber solutions from the air pollution control equipment. Pyrolysis oils from tyres and
other products are complex mixtures of hydrocarbons. The liquid fraction can contain a range
of species including acids, alcohols, aldehydes, aromatics, ketones, esters, heterocyclic
derivatives, and phenols, along with varying amounts of water [115]. These oils typically
contain a number of substances that can be considered toxic, but can be handled safely using
typical industrial practices. They also represent an intermediate product that is not disposed
of, but can be used either via combustion for energy production or for the production of other
chemicals after upgrading. Residual products from the gas cleaning and water recovery
processes can be handled using well-established procedures. These residual products include
industrial-grade salts and a separate precipitate containing the heavy metals from the
feedstock stream. In some cases, this precipitate may be rich enough in zinc and lead to
warrant recovery in a smelter operation [49].
111
5.3.3 Solid Waste Residues
The solid residue remaining from PGL processes is typically an inorganic ash or char. The
inorganic ash is the residue from the 3 to 5% of inorganic material in the tyre that cannot be
converted to energy or products through PGL [49]. The ash contains non-volatile trace metals
that are more concentrated in the ash than in the feedstock, but with proper management can
be treated and disposed of in a manner that does not pose an environmental threat. In some
cases, metals can be recycled from the ash. The leach-ability of the ash is used to indicate
whether the ash is classified as a hazardous or non-hazardous waste. Char contains carbon
black; sulphur; zinc oxide; clay fillers; calcium and magnesium carbonates and silicates, all
of which produce PM10 emissions. Operations such as screening, grinding and processing
cause PM10 emissions and could be controlled with dust collectors and a baghouse filters. If
markets for the char cannot be developed, the char becomes a major solid waste problem. In
addition, to landfill disposal, plastic bags should be used and must be shipped and disposed of
in steel drums to prevent additional fugitive emissions during transportation and disposal
[116].
5.4 Pyrolysis plant comparison study
This section will focus on the comparison between the modelled pyrolysis plant and the
Pretoria based plant (Milvinetix) in term of operation, end product, financial requirements
and plant viability. The following report was obtained from the 2013 Milvinetix business plan
[129] .
5.4.1 Production
The business plan and financial models have been modelled around 90% efficiency in each
process. Tonnage tyre processing per month is expected to be 10 ton/day x 26 working days,
thus resulting in 260 tonnes treated per month. Oil production per month (40 % yield on total
tonnage input, 104 litres per month), steel production per month (10 % yield per total tonnage
input, 26 tonnes per month) and carbon Black production per month (30 % yield on total
input 156 tonnes per month).
5.4.2 End products
According to the Milvinetix business plan, the business model will allow through correct
processing and proper filtration of tyre derived oil production of industrial diesel, furnace oil,
bunker fuel, gas. The carbon black will be the main component in the manufacturing of
charcoal briquettes as an alternative heat source to wood. Industrial diesel, furnace oil and
112
bunker fuel is mainly used in: Noxious industries: mining, farming and generators, in
addition, the shipping industry market related price would be R 6.00/litre. The gas created by
the pyrolysis process, forms part of the heating process to generate heat for the pyrolysis
process, hence the process becomes self-sustaining and prevents toxic gasses being released
into the atmosphere.
5.4.3 Financial Requirements
Below are two options depending on requirements and financial options open to the potential
purchaser of a tyre recycling plant. The price includes all machinery, machinery installation,
training and management of the two options.
a) Option 1 is a single reactor plant, Table 5.8.
b) Option 2 is a double reactor plant, Table 5.9.
Table 5.8
Business model option 1
Description Amount
Equipment and machinery for Import
Shipping Cost
Equipment & Machinery Local
Site Preparation
Technical and Installation support
Environmental & Licensing
Factory & Loading Inspection plus transport
Health & Safety Plus OHSA accreditation
IT & Electrical works
Excludes working Capital as this is case sensitive (APROXIMATLY) R 750.000.00
Total Including vat R 11 190 000.00
113
Table 5.9
Business model option 2
Description Amount
Equipment and machinery for Import
Shipping Cost
Equipment & Machinery Local
Site Preparation
Technical and Installation support
Environmental & Licensing
Factory & Loading Inspection plus transport
Health & Safety Plus OHSA accreditation
IT & Electrical works
Excludes working Capital as this is case sensitive (APROXIMATLY) R 1.500.000.00
Total including Vat R 24 380 000.00
According to their financial model, loan repayment will end after 4 years, thus resulting in
the business to break-even at that time. This compares very well with the proposed model in
this work; the model suggests a break-even point just after the 4th
year, Fig. 5.1 and 5.2. In
addition, the required investment needed for each project compares very well, R 10 173 075,
35 and R 11 190 000, 00 are required for the Milvinetix and proposed business model
respectively. Thus, this proves that the model used for this work is applicable in the
construction and commissioning of a new pyrolysis plant in the Gauteng region.
115
Based on the pyrolysis plant business model and all relevant data collected through literature
analysis, questionnaires, site visits as well as telephonic and personal interviews the
following conclusions are made:
Waste tyre pyrolysis is a potential waste tyre remedial technology and developing
countries like South Africa should invest in such waste treatment facilities.
Waste tyre pyrolysis shows a profitable business model that is suitable for the South
African environment.
The waste tyre plant business model shows a sound payback period of less than 5 years
and plant life of 12 years is projected.
A further treatment step is required to increase the value of the products.
The final value added products may have the following applications, the oil can be
used in agricultural vehicles or blended to a diesel feed stock, the carbon black can be
reduced to different grades for applications in the rubber, paint, pigments and
briquetting industry and the residual steel wires are sold to local steel dealers.
For a successful business model, a stable and sustainable product market should exist.
It is recommended that a continuation of this work should be done with the costing based on
an existing plant. Other cost estimation models such as the study estimate and preliminary
estimate methods should be used to obtain conclusive results.
116
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APPENDICES
Appendix A
Equipment costing equations
(All equipment) (5.1)
(Heat exchangers) (5.2)
(5.3)
(5.4)
(5.5)
Nomenclature:
126
Fig. A.1 Temperature correction factor: two shell passes; four or multiples of four tube passes
Table A.1
Heat exchanger design, material and pressure correction factor
Material Shell/ Tube Surface Area, ft
2
up to 100 100-500 500-1000 1000-5000 5000-10000
CS/CSa 1.00 1.00 1.00 1.00 1.00
SS/SS 2.50 3.10 3.26 3.45 4.50
CS/SS 1.54 7.78 2.25 2.81 3.52
a. Carbon steel shell/ Carbon steel tubes
127
Table A.2
Temperature, pressure and material of construction correction factor
Design Pressure, atm Correction Factor
0.005 1.3
0.014 1.2
0.048 1.1
0.54 to 6.8 1.0
48 1.1
204 1.2
408 1.3
Design Temp,
oC Correction factor
-80 1.3
0 1.0
100 1.05
600 1.1
5000 1.2
1000 1.4
Material of construction Correction factor
Carbon steel (mild) 1.0
Bronze 1.05
Carbon/ molybdenum 1.065
Steel
Aluminium 1.075
Cast steel 1.11
Stainless steel 1.28 to 1.5
Worthite alloy 1.41
Hastelloy C alloy 1.54
Monel alloy 1.65
Titanium 2.0
Table A.3
Equipment cost data 1
Equipment Size Capacity units FOB Cost4, k$ January [1990] Correlation range Capacity exponent
Agitators 3 hp 2.8 1.0-7.0 0.50, e
Propeller 20.0 hp 12.0 3.0- 100.0 0.30, e
Turbine, single impeller 1.0 ft2 0.137, j 0.80, j
Air cooler
Blower
Centrifugal 4000 ft2/min 60.0 800,0- 1.8x10
4 0.59, c
Compressors and drivers
Centrifugal, electric motor 600 hp 190 2x103 - 1.8x10
4 0.32 c
Centrifugal, steam or gas turbine 600 hp 210 2x103 - 2.1x10
4 0.32, c
Electric motors
Open drip proof 60 kW 3.0, g 0.2x103 - 5.0x10
3 1.10, f
Totally enclosed 60 kW 4.0, g 0.25x103 - 6.0x10
3 1.10, f
Explosion proof 100 kW 9.5, g 0.3x103 - 8.0x10
3 1.10, f
Evaporators (installed)
Forced circulation 1000 ft2 2500, i 1.0x10
2 - 7.0x10
3 0.70, e
Horizontal tube 1000 ft2 120, i 1.0x10
2 - 8.0x10
3 0.53, e
Vertical tube 1000 ft2 180, i 1.0x10
2 - 8.0x10
3 0.53, e
Fans
Centrifugal, radial, low range 4000 ft2/min 2.5 1.0x10
3 - 1.0x10
4 0.44
Centrifugal, radial, high range 10 000 ft2/min 40.0 1.0x10
4 - 1.0x10
5 1.17
Heat exchanger (shell/tube)b
129
Floating head, CS/CS 150 psia 1000 ft2 14.0 1.0x10
2 - 5.0x10
3 0.65, e
Process furnace 20 000 kJ/s 750, g 3.0x103 - 1.6x10
5 0.85, g
Pumps
Centrifugal, high range 20 hp 9.0 2.68 - 335 0.42, g
Centrifugal, low range 0.29 hp 2.3 0.10 -2.0 0.29, g
Gear, 100 psia 80 gpm 1.3 16 - 400 0.36, f
Reactorno agitator
Stirred tank, jacketed, CS, 50 psia 600 gal 17.0 30 - 6.0x103 0.57, f
Stirred tank, glass lined, 100 psia 400 gal 33.0 30 - 4.0x103 0.54, c
Rotary vacuum filter (SS) 30 ft2 60.0 4.0 - 600 0.67, c
Tanks
Storage, cone roof, low range 12x106 gal 170 2.0x10
5 - 1.2x10
6 0.32, f
Storage, cone roof, high range 12x106 gal 170 1.2x10
6 - 1.1x10
7 0.32, f
b. The shell-and-lube materials can differ. CS/SS means carbon steel shell and the stainless steel tubes.
c. Remer, D. S, Chai, L.H, Design Factors for Scaling-up Engineering Equipment, Chem. Eng. Progr, 87, 8, 77, 1990.
e. Guthrie, K.M., Data and Techniques for Preliminary Cost Estimating, Chem. Eng., 76, 7, 114, 1969.
f. Woods, DR., Financial Decision Making in the Process Industry, Prentice Hall, Englewood Cliffs, NJ, 1975.
g. Ulrich, G.D., A Guide to Chemical Engineering Process Design and Economics, John Wiley & Sons, New York, NY, 1984.
i. Peters, M.S., Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, 4th ed., McGrawHill, New York, NY, 1991.
j. Baasel, W.D., Preliminary Chemical Engineering Plant Design, 2nd edt., VanNostrand, New York, NY, 1990.
130
Table A.4
Equipment cost data 2
Equipment Size unit, S Size range Constant, C, £ C, $ Index, n Comment
Agitators
Propeller Driver 5 - 75 1 200 1 900 0.5
Turbine Power, kW 1 800 3 000 0.5
Boiler Oil or gas fired
Packed
up to 10 bar kg/h steam (5 -50)x103 70 120 0.8
10 to 60 bar 60 100 0.8
Centrifuges
Horizontal basket dia, m 0.5 - 1.0 35 000 58 00 1.3 Carbon steel
Vertical basket 600 35 000 58 000 1.0 x 1.7 for SS
Compressors
Centrifugal Driver 20 -500 1 160 1 920 0.8 Electric, max press
Power, kW
Reciprocating 1 160 2 700 0.8 50 bar
Conveyors
Belt Length, m 2 - 40
0.5 m wide 1 200 1 900 0.75
1.0 m wide 1 800 2 900 0.75
Crushers
Cone t/h 20 -200 2 300 3 800 0.85
Pulverisers kg/h 2 000 3 400 0.35
Dryer
Rotary area, m2 5 - 30 21 000 35 000 0.45 Direct
Pan 2 -10 4 700 7 700 0.35 gas fired
Evaporators
Vertical tube area, m2 10 - 100 12 000 20 000 0.53 Carbon steel
131
Falling film 6 500 10 000 0.52
Filters
Plate and frame area, m2 5 - 10 5 400 8 800 0.6 Cast steel
Vacuum drum 1 -10 21 000 34 000 0.6 Carbon steel
Furnaces
Process Heat abs,kW 103 - 10
4 330 540 0.77 Carbon steel
Cylindrical 103 - 10
5 340 560 0.77 x 2.0 SS
Box
Reactors
Jacketed Capacity, m3 3 - 30 9 300 15 000 0.4 Carbon steel
Agitated 18 500 31 000 0.45 Glass lined
Tank
Process Capacity, m3
Vertical 1 -50 1 450 2 400 0.6 atm, press
Horizontal 10 - 100 1 750 2 900 0.6 Carbon steel
Storage
Floating roof 50 - 80 000 2 500 4 350 0.55 x 2 for
Cone roof 50 - 80 000 1 400 2 300 0.55 Stainless steel
Appendix B
Table B.1
SGS pyrolysis oil test report
Diesel Analysis Report
Client Milvinetix
Product Gasoil
Sample source unknown
Sampling method Supplied Lab report
No. 557/1-1-10-12
Date supplied 26 October 2012 Time sampled 10H00
Date tested 30 October 2012 Time tested 16H00
Sample condition 1x Plastic 5 litre bottle
Test description Test method Specification Results
Density @20oC, kg/l ASTM D4052 0.800 0.8950
Viscosity @ 40oC, cSt ASTM D445 2.2-5.3 2.868
Flash point, oC ASTM D93 55 min <25
Water content, ppm ASTM 6304 500 max 673
Sulphur content, ppm ASTM D4294 Report 8100
Total contamination number, mg/kg IP 440 24 max 31
Distillation oC:
ASTM D86 362 max 378.8 - 90% recovery,
oC
Micro carbon residue (10% bottoms) ASTM D4530 0.2 max 4.5
Cetane index ASTM D4737 Report 32.01
133
Diesel Analysis Report
Table B.2
Wear Check diesel analysis report
Test description Results Units SANS 342 (2006) SPECIFICATIONS
Density @20oC 0.8772 kg/l 0.800 Pass Density is within the SANS specifications
Viscosity @ 40oC 2.1 cSt 2.2-5.3
Not require or not tested
Flash point 26 oC 55 min Fail Flashpoint is below the specification
Water content 0.06 % 500 max Fail Water content exceeds the specification
Sulphur content 21400 ppm Report Pass Sulphur Content exceeds the specification
Total contamination number 38.6 mg/kg 24 max Fail Total Contamination exceeds the spec.
90% recovery temperature 360 oC
Fail The 90% Rec. Temp. is within specification
% Residue 2 % 0.2 max
Calculated cetane index 34.2 Report
For all correspondence, please contact WearCheck Africa
Tel: (031) 700-5460 / (011) 392-6322, Fax: (031) 700-5471 / (011) 392-6350 or Email: [email protected]
2011/09/02 WEARCHECK AFRICA IS A REGISTERED ISO 9001 AND ISO 14001 COMPANY
Table B.3
Coal and Minerals Laboratory, CSIR, carbon black sample
Milvinetix
Date received 22 June 2012
Date reported 27 July 2012
Job No. 145/12-1
SABS No
Sample
Carbon black
Description Coal
Air Dry Basis Test Method Results
Calorific value MJ/kg 2215/14/W07 31.18
Moisture content % 2215/14/W06 1.3
Ash content % 2215/14/W10 / ASTM 1506 14.5
Volatile matter content % 2215/14/W09 24.3
Fixed carbon % By diff. 59.9
Total sulphur % ASTM D4239 2.61
Table B .4
Pyrolysis plant model revenue costing, inflation index and utility costs
Revenue costing
Variable Units Base cost Year 0 Year 1 Year 2 Year 3 Year 4
Tyre fee
R 13,00 R 29 786,74 R 29 786,74 R 29 786,74 R 29 786,74 R 29 786,74
Selling price of tyre derived fuel R/L R 9,50 R 10 065 269,86 R 10 467 880,66 R 10 467 880,66 R 11 567 008,13 R 12 769 976,97
Selling price of carbon black @ different
grades
R 430,00 R 310 354,89 R 322 769,09 R 322 769,09 R 322 769,09 R 322 769,09
Rubber + rubber products (24-33nm, N220) R/ton
Paints(70-96 nm, N770) R/ton
Pigments(70-96 nm, N770) R/ton
Activated carbon (250-350 nm, N990) R/ton
Briquettes R/ton
Selling price of steel wires R/ton R2500,00 R 773 309,53 R 804 241,91 R 892 708,52 R 892 708,52 R 892 708,52
R 11 178 721,02 R 12 089 665,53 R 13 001 590,96 R 14 157 561,09 R 15 472 826,42
Inflation
Year 0 Year 1 Year 2 Year 3 Year 4
Product price inflation Index
1,00 1,04 1,11 1,11 1,10
Labour cost inflation Index
1,00 1,04 1,08 1,10 1,00
Material cost inflation Index
1,00 1,05 1,12 1,16 1,22
Fuel cost inflation Index
1,00 1,05 1,12 1,16 1,22
General inflation Index 1,00 1,04 1,09 1,10 1,22
Variable costs
Electricity
R 61 257,60 R 63 707,90 R 69 441,62 R 76 385,78 R 93 190,65
Water
R 218 437,27 R 227 174,76 R 247 620,49 R 272 382,54 R 332 306,70
Reagent
R 120 000,00 R 124 800,00 R 136 032,00 R 149 635,20 R 182 554,94
nitrogen
R 687,79 R 225 937,70 R 234 975,21 R 260 822,48 R 288 208,84 R 318 182,56
R 625 632,57 R 650 657,87 R 713 916,59 R 786 612,36 R 926 234,85
136
Table B .5
Pyrolysis plant model revenue costing, inflation index and utility costs continued...
Revenue costing
Variable Units Base cost Year 5 Year 6 Year 7 Year 8 Year 9
Tyre fee
R 13,00 R 29 786,74 R 29 786,74 R 30 382,47 R 30 382,47 R 30 382,47
Selling price of tyre derived fuel R/L R 9,50 R 14 098 054,58 R 15 578 350,31 R 15 889 917,31 R 17 320 009,87 R 18 186 010,37
Selling price of carbon black @ different
grades R 430,00 R 322 769,09 R 322 769,09 R 355 046,00 R 355 046,00 R 355 046,00
Rubber + rubber products (24-33nm, N220) R/ton
Paints(70-96 nm, N770) R/ton
Pigments(70-96 nm, N770) R/ton
Activated carbon (250-350 nm, N990) R/ton
Briquettes R/ton
Selling price of steel wires R/ton R 2 500,00 R 892 708,52 R 892 708,52 R 981 979,38 R 981 979,38 R 981 979,38
R 16 939 024,09 R 18 590 094,20 R 18 983 057,67 R 20 369 285,31 R 20 531 089,12
Inflation
Year 5 Year 6 Year 7 Year 8 Year 9
Product price inflation Index
1,10 1,11 1,10 1,09 1,05
Labour cost inflation Index
1,06 1,07 1,09 1,09 1,10
Material cost inflation Index
1,28 1,34 1,41 1,48 1,55
Fuel cost inflation Index
1,28 1,34 1,41 1,48 1,55
General inflation Index
1,15 1,11 1,02 1,05 1,04
Variable costs
Electricity
R 107 169,24 R 118 957,86 R 121 337,02 R 127 403,87 R 132 500,02
Water
R 382 152,70 R 424 189,50 R 432 673,29 R 454 306,95 R 472 479,23
Reagent
R 209 938,19 R 233 031,39 R 237 692,01 R 249 576,61 R 259 559,68
nitrogen
R 687,79 R 351 273,55 R 388 157,27 R 426 973,00 R 465 400,57 R 488 670,60
R 1 050 533,68 R 1 164 336,02 R 1 218 675,32 R 1 296 688,01 R 1 353 209,53
137
Table B.6
Pyrolysis plant model revenue costing, inflation index and utility costs continued...
Revenue costing
Variable Units Base cost Year 10 Year 11 Year 12 Year 13
Tyre fee
R 13,00 R 30 382,47 R 30 382,47 R 30 382,47 R 30 382,47
Selling price of tyre derived fuel R/L R 9,50 R 19 277 170,99 R 20 241 029,54 R 20 848 260,42 R 21 473 708,24
Selling price of carbon black @ different grades
R 430,00 R 355 046,00 R 355 046,00 R 355 046,00 R 355 046,00
Rubber + rubber products (24-33nm, N220) R/ton
Paints(70-96 nm, N770) R/ton
Pigments(70-96 nm, N770) R/ton
Activated carbon (250-350 nm, N990) R/ton
Briquettes R/ton
Selling price of steel wires R/ton R 2 500,00 R 981 979,38 R 981 979,38 R 981 979,38 R 981 979,38
R 21 883 253,56 R 22 688 859,25 R 22 882 138,32 R 23 526 349,56
Inflation Year 10 Year 11 Year 12 Year 13
Product price inflation Index
1,06 1,05 1,03 1,03
Labour cost inflation Index
1,06 1,02 1,02 1,00
Material cost inflation Index
1,63 1,71 1,80 1,89
Fuel cost inflation Index
1,63 1,71 1,80 1,89
General inflation Index 1,02 1,03 1,00 1,00
Variable costs
Electricity
R 135 150,03 R 139 204,53 R 139 204,53 R 139 343,73
Water
R 481 928,82 R 496 386,68 R 496 386,68 R 496 883,07
Reagent
R 264 750,87 R 272 693,40 R 272 693,40 R 272 966,09
nitrogen
R 687,79 R 517 990,83 R 543 890,37 R 560 207,09 R 577 013,30
R 1 399 820,55 R 1 452 174,98 R 1 452 174,98 R 1 453 627,16
138
Table B.7
Pyrolysis plant model fixed cost, total costs and profits continued...
Fixed costs Quantity Base cost Year 5 Year 6 Year 7 Year 8 Year 9
Rental
R 230 400,00 R 241 217,22 R 253 278,08 R 265 941,98 R 279 239,08
Plant manager 1 35000 R 550 548,55 R 589 086,95 R 642 104,78 R 700 536,31 R 770 589,94
Plant engineer 1 28000 R 440 438,84 R 471 269,56 R 513 683,82 R 560 429,05 R 616 471,95
Shift foreman 4 19000 R 1 195 476,86 R 1 279 160,24 R 1 394 284,66 R 1 521 164,56 R 1 673 281,02
Skilled technicians
boiler maker 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38
fitter 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38
electrician 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38
mechanical 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38
Plant operators 16 11500 R 2 894 312,39 R 3 096 914,26 R 3 375 636,54 R 3 682 819,46 R 4 051 101,41
Security 4 4000 R 251 679,34 R 269 296,89 R 293 533,61 R 320 245,17 R 352 269,69
Cleaners 2 4000 R 125 839,67 R 134 648,45 R 146 766,81 R 160 122,59 R 176 134,84
Accountant/secretary 2 20500 R 644 928,30 R 690 073,29 R 752 179,88 R 820 628,25 R 902 691,08
R 8 116 658,65 R 8 684 824,76 R 9 466 458,99 R 10 327 906,76 R 11 360 697,43
Maintenance
R 846 610,02 R 939 737,12 R 958 531,86 R 1 006 458,46 R 1 046 716,79
Land rental/ lease
R 314 907,28 R 349 547,08 R 356 538,02 R 374 364,92 R 389 339,52
Insurance
R 90 119,39 R 100 032,53 R 102 033,18 R 107 134,84 R 111 420,23
Tax/Levies
R 180 238,79 R 200 065,06 R 204 066,36 R 214 269,68 R 222 840,46
Medical
R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68
Telephone line
R 52 484,55 R 58 257,85 R 59 423,00 R 62 394,15 R 64 889,92
IT
R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68
Auditing fees
R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68
Miscellaneous materials
R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68
Safety clothing (PPE)
Cleaning material
Payment period and profits
Year 5 Year 6 Year 7 Year 8 Year 9
Costs
R 12 237 903,91 R 13 131 220,01 R 14 019 725,09 R 15 075 049,70 R 16 264 347,22
Revenues
Profit after tax R 15 652 561,34 R 19 695 047,83 R 22 813 386,26 R 26 509 559,70 R 28 910 206,32
Net annual
profit R 3 414 657,44 R 6 563 827,83 R 8 793 661,17 R 11 434 509,99 R 12 645 859,09
139
Table B.8
Pyrolysis plant model fixed cost, total costs and profits continued...
Fixed costs Quantity Base cost Year 10 Year 11 Year 12
Rental
R 293 201,03 R 307 861,08 R 323 254,14
Plant manager 1 35000 R 816 825,34 R 833 161,85 R 849 825,08
Plant engineer 1 28000 R 653 460,27 R 666 529,48 R 679 860,07
Shift foreman 4 19000 R 1 773 677,88 R 1 809 151,44 R 1 845 334,46
Skilled technicians
R 0,00
boiler maker 2 16000 R 746 811,74 R 761 747,97 R 776 982,93
fitter 2 16000 R 746 811,74 R 761 747,97 R 776 982,93
electrician 2 16000 R 746 811,74 R 761 747,97 R 776 982,93
mechanical 2 16000 R 746 811,74 R 761 747,97 R 776 982,93
Plant operators 16 11500 R 4 294 167,49 R 4 380 050,84 R 4 467 651,86
Security 4 4000 R 373 405,87 R 380 873,99 R 388 491,47
Cleaners 2 4000 R 186 702,93 R 190 436,99 R 194 245,73
Accountant/secretary 2 20500 R 956 852,54 R 975 989,59 R 995 509,38
R 12 042 339,28 R 12 283 186,06 R 12 528 849,79
Maintenance
R 1 067 651,13 R 1 099 680,66 R 1 099 680,66
Land rental/ lease
R 397 126,31 R 409 040,10 R 409 040,10
Insurance
R 113 648,64 R 117 058,09 R 117 058,09
Tax/Levies
R 227 297,27 R 234 116,19 R 234 116,19
Medical
R 106 765,11 R 109 968,07 R 109 968,07
Telephone line
R 66 187,72 R 68 173,35 R 68 173,35
IT
R 106 765,11 R 109 968,07 R 109 968,07
Auditing fees
R 106 765,11 R 109 968,07 R 109 968,07
Miscellaneous materials
R 106 765,11 R 109 968,07 R 109 968,07
Safety clothing (PPE)
Cleaning material
Payment period and profits
Year 10 Year 11 Year 12
Costs
R 17 051 639,91 R 17 428 470,33 R 17 689 527,10