Creating green value from palm residues in Malaysia · a more dedicated and up-to-date version of...

Creating green value from palm residues in Malaysia

A Palmares Report

Author(s)

H.J.M. Visser (ECN part of TNO)

F. Sebastiani (ECN part of TNO)

K. Meesters (WUR)

W. Elbersen (WUR)

Disclaimer

Although the information contained in this document is derived from

reliable sources and reasonable care has been taken in the compiling of

this document, ECN part of TNO cannot be held responsible by the user for

any errors, inaccuracies and/or omissions contained therein, regardless of

the cause, nor can ECN part of TNO be held responsible for any damages

that may result therefrom. Any use that is made of the information

contained in this document and decisions made by the user on the basis of

this information are for the account and risk of the user. In no event shall

ECN part of TNO, its managers, directors and/or employees have any

liability for indirect, non-material or consequential damages, including loss

of profit or revenue and loss of contracts or orders.

In co-operation with

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Creating green value from palm residues in Malaysia

Project K2K-16C1301

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Summary

Creating green value from palm residues offers the opportunity to reduce emissions and valorise

otherwise wasted agricultural residues. Dutch companies and research institutes have joined forces

in Palmares: a partnership, supported by the Dutch government, which aims to fast-track green

value creation from palm residues in Malaysia. In close collaboration with the Malaysian palm oil

industry, and in line with the ambitions of the Malaysian Government, we look for mutual

opportunities and benefits.

Malaysia produces 118 megatons (Mton) of dry oil palm biomass per year. More than 51% of this

amount is residues. Malaysia aims to valorise these biomass streams and use them to mitigate its

climate change impact. The Malaysian National Biomass Strategy 2020 identifies electricity from

biogas and biomass as two important pillars.

Dutch companies and institutions can potentially propose/supply alternative technologies to help

accomplish these goals. Rather than one installation or solution for one residue, Palmares proposes

integrated solutions with scenarios that incorporate the integration of all technologies necessary

while taking into account the local situation and the business case as well as the environment.

This work is an assessment of the availability of residue streams, the opportunities to use the

residues both in fertilisation as well as in bio-energy and bio-product schemes. The main remaining

challenges that need to be tackled are identified.

After making balances of nitrogen, phosphorous and potassium (N,P,K) over the ingoing and

outgoing streams of the plantation, it was concluded that P-fertilisation schemes are in need of

improvement, that the fronts (leaves) are best left in the field as an important source of N- and K-

fertilisation and that for the trunks it still remains to be seen what the best option is at the end of

the tree lifetime. Although the trunks provide a minor amount of fertilisation elements, the large

quantity of organic material in combination with the fast decay in the tropics might lead to excess

CO2 emissions, which could potentially outweigh the importance of nutrient dosing. On this topic,

however, more research is needed. Further it was found that the palm oil mill effluent (POME) is

best treated by digestion for methane recovery and the solid digestate used as a possible fertiliser

product, that palm kernel meal (PKM) has a good and valuable application as animal fodder, that

mesocarp fibres (MF) and palm kernel shells (PKS) are already used as fuel but might be used for

higher-value products or export fuels and that the largest under-used stream remaining is the empty

fruit bunches (EFB). The fact that EFB is currently hardly used has two main reasons: 1. It is very

difficult to do any kind of pre-treatment due to its texture, and 2. it contains a high alkali (salt)

content, which results in low ash melting temperatures when used as an energy source in

conventional installations.

After considering the main challenges, some new concepts are described to gain the most value in

terms of economic profit and more sustainable approaches. It is concluded that the palm oil mills’

energy demand can be entirely supplied through the anaerobic digestion of palm oil mill effluent

(POME) and the combustion of EFB, leaving additional residues available for upgrading to fuels and

products. Various pre-treatment technologies can be used to improve EFB fuel properties, including

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washing, torrefaction and TORWASH® (i.e. integrated wet-torrefaction process). The latter enables

the lowering of drying energy costs, the removal of alkali salts and the concentration of EFB’s

phosphorous within the POME digestate. As an additional alternative, low temperature gasification

can simultaneously optimise fertilisation and energy recovery through the co-production of biochar,

a tar-free soil improver.

In conclusion, several options are available to improve residues’ properties, balance soil fertilisation

and reduce spontaneous decaying emissions. To exploit these opportunities, additional knowledge

on logistics and greenhouse gas (GHG) emissions due to biomass decaying as well as market data

are needed. Local differences would require more tailor-made work and integration of the various

processes considered. Further work should be on the most promising business cases for different

locations, and the definition of specific base cases to evaluate alternative concepts. Some of the

questions raised in the document would require more research to provide data that would reduce

uncertainty and economic risks.

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Acknowledgments

First of all we would like to thank the staff at the Dutch embassy in Kuala Lumpur, our liaison officers,

Bregje Drion and Sanne de Best, and the Dutch ambassador, Karin Mössenlecher, for support in

starting up Palmares and introducing us to Malaysian companies and governmental agencies, both

on the mainland as well as on Sarawak and Sabah. We would like to express our sincere appreciation

for the very warm atmosphere we encountered everywhere in Malaysia and for the hospitality upon

every visit, when people really took the time for us. We were taught some important background

knowledge on the growing of oil palms and plantation management as well as the milling process

and its side products. Together with our knowledge on advanced biomass treatment procedures

and processes, gained over past decades, this has merged into the schemes suggested in this report

for the valorisation of palm oil residues in a sustainable way.

RVO is kindly thanked for its contribution in the Palmares consortium and the opportunity to make

a more dedicated and up-to-date version of an inventory for the opportunities in palm oil residues

in Malaysia via this K2K assignment (K2K16C1301).

Several people have helped us with this report by kindly contributing a scheme or a graph or by

critically reading the draft report. More specifically we would to thank Kees Kwant and all other

Palmares partners as well as Jan Pels and Christiaan van der Meijden for their contributions to the

technology scenarios.

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Table of Contents

Table of Contents 6

1. Introduction 8

2. Palm Oil Residues in Malaysia 10

2.1 The Palm Oil Extraction Process 10

2.2 Palm Oil Residues Description 11

2.3 The Availability of Palm Oil Residues in Malaysia 13

2.4 The Market Potential of Malaysian Palm Residues 14

3. Dry Matter, Energy and Nutrients Flows Analysis 17

3.1 Dry Matter Flow 17

3.2 Energy Flow 19

3.3 Nutrients Flow 21

3.4 Implications from the Energy and Nutrient Flow Analyses 26

4. The Current Challenges 29

4.1 GHG Emissions Reduction 29

4.2 Bio-residues for Fertilisation or Energy Generation from a GHG Perspective? 30

4.3 Un-utilised Palm Residues for Energy Generation 31

5. Alternative Processes for Energy Recovery, Fuel Production and Improved Fertilisation 34

5.1 Objectives of the Alternative Processes 34

5.2 Alternative Process Concepts 34

5.3 Concepts Description 36

5.4 Concept Choices for Local Variation 47

6. Alternative Higher-end Products 49

7. Conclusions 50

8. Recommendations 51

8.1 Technical Recommendations 51

8.2 Environmental Recommendations 51

8.3 Business Opportunities 51

9. List of References 53

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1. Introduction

Biomass residues can replace fossil fuels and feedstocks, enabling the realisation of more

sustainable and circular value chains. However, the realisation of such potential is hindered by the

heterogeneity, the inorganic content and sometimes the distrusted availability of these same

residues. Palm oil residues are among those biomass streams that are generated in large volumes

at centralised production locations (e.g. at palm oil mill sites). Based on volume and concentration,

these biomass feedstocks have the potential to become a significant source for sustainable fuels

and products in an economically viable way. The fact that these residues are not yet living up to

their full potential requires the identification of the most prominent challenges that remain to date.

Among the various palm oil producing countries, Malaysia is a major player, being the second largest

palm oil producer in the world. In 2012, it was estimated that an overall yield of 118 Mton dry

biomass was available, with an expected rise up to 100 Mton by 2020. By using ‘only’ 20 Mton of

this amount to manufacture fuels and feedstocks, the gross nation income (GNI) is estimated to rise

by roughly $10 billion in 2020 [1]. Environmentally, just the production of biogas through the

anaerobic digestion of mills’ wastewater would reduce the country’s CO2 emissions by 12%. But

even more important, it is the ambition of the Malaysian government to also bring this potential to

realisation [1].

In the Netherlands, the research on biomass residues’ valorisation and efficient land fertilisation has

reached an advanced state due to the decades-long efforts made in knowledge build-up and

technology development. A large variety of technological alternatives for biomass pre-treatment

and valorisation is available. These range from thermochemical technologies, such as hydrothermal

treatment, combustion and gasification, to fermentation technologies, such as anaerobic digestion

and enzymatic fermentation. Furthermore, there is a growing trend in integrating the production of

energy and biomass products and/or more effective soil improvers and fertilisers with residues or

co-products such as (digestate-) compost and biochar.

Appreciating the ambition of the Malaysian Government and the Dutch knowledge base in biomass

residues, a group of six businesses and two research organisations joined together to start the

‘Palmares’ project, which stands for palm, Malaysia and residues. A covenant for three years of co-

operation was signed, starting in December 2016. This ‘Partners for International Business’ (PIB)

project focusses on the optimisation of the Malaysian oil palm residues value chain. Therefore, the

partners in ‘Palmares’ will actively promote and search for co-operation with Malaysian businesses

and governmental agencies implementing the ambitious goals of the National Biomass Strategy by

2020. This visionary document sets out ambitions for which the palm oil industries will need novel,

economically viable technologies. The first fact-finding mission of the Dutch partners went to

Malaysia in early 2017, a second in the autumn of 2017 and a third in autumn 2018. Important

knowledge gained in the missions on local situations, ambitions and difficulties is incorporated in

this document, although often implicitly.

This study aims to gain insights into the market opportunities in Malaysia for those Dutch enterprises

that are active in the area of sustainable biomass conversion to fuels and feedstocks.

Simultaneously, it is also intended to provide an overview of the most promising technologies based

on the acquired knowledge in this report. This study is an assignment in the framework of the

knowledge-to-knowledge (K2K) part of the PIB Palmares.

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Abbreviations used:

CPO: Crude Palm Oil

EFB: Empty Fruit Bunch

MF: Mesocarp Fibre

FFB: Fresh Fruit Bunch

GHG: Greenhouse Gas

GNI: Gross National Income

PKO: Palm Kernel Oil

PKM: Palm Kernel Meal

PKS: Palm Kernel Shells

POF: Palm Oil Fronds

POT: Palm Oil Trunks

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2. Palm Oil Residues in Malaysia

2.1 The Palm Oil Extraction Process

A description of the oil extraction process will be given first as important background knowledge.

Some knowledge of the processes on the mill site is required before the focus can be directed to the

possibilities for the residues of the process.

Figure 1 – Schematic flow diagram of the palm oil extraction process; the approximate mass flow values are on a wet basis,

and palm residues are highlighted with red circles [4].

The fresh fruit bunches (FFB) are transported from the plantation to the mill. On-site, these are

sterilised using steam, which is then condensed to become part of the POME. Subsequently, the

palm fruits are stripped from the bunches, leading to the generation of EFBs, which are discharged.

After digestion and pressing, the press-cake and liquor are separated. On one side, the crude oil is

recovered through a series of screening and filtering steps to be further clarified, while the thickened

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sludge is discharged, representing the major fraction of the POME. On the other side, fibres are first

recovered from the press-cake. Subsequently, kernel shells are removed, through drying and

crushing and using a hydro-cyclone. Fibres and shells are mostly used for energy generation at the

mill site and to a minor extent for the manufacturing of end products. The de-shelled and washed

kernels are then dried and finally sent to the kernel treatment process for the production of PKO.

2.2 Palm Oil Residues Description

The palm oil residues differ significantly in physical, biological and chemical characteristics, making

them more or less suitable for different uses and applications. In Table 2, the final uses of the various

residues are summarised, while these are reported in more detail below, together with a description

of the residues themselves:

• Empty Fruit Bunches (EFB) are the outer furry bunch of palm fruits. After sterilisation the

bunches are stripped from the palm fruit. EFBs are a very wet product. The handling is

complex, and the logistic costs are high in cases where any use is foreseen. Additionally, the

combustion of EFB causes fouling of the installation due to the high silica and alkali salts

content. As EFBs are then less suitable for energy valorisation through combustion

compared to other residues, they are under-utilised to a great extent. Even rarely are the

EFB composted or reused as mulch. The vast majority of EFBs is indeed disposed in the

vicinity of the mills, undergoing spontaneous and uncontrolled decomposition.

• Mesocarp Fibres (MF), or simply fibres, are a solid by-product of the fresh first fruit pressing.

MFs compose the majority of the residual dry matter within the press-cake. These fibres

typically have lower moisture content than EFBs. Furthermore, the lower salts and silica

amount makes them more suitable for direct combustion. Currently, the fibres are mostly

used to generate heat and power at the mill site. A minor fraction of the fibre is a source of

feedstock for further processing or use in final products.

• Palm Kernel Shells (PKS) are a second by-product derived from the recovery of palm kernels

after fibre removal. These are also used to meet the internal mill energy demand through

combustion. The shells’ combustion properties are also superior to that of EFBs. AS for MFs,

a minor fraction is used to manufacture end products, such as activated charcoal for

international export to Europe and Japan.

• Palm Kernel Meal (PKM) is a relatively smal residue stream, resulting from the kernel oil

extraction. This stream has a high protein content, which makes it suitable for animal

fodder. Being mainly used as cattle feed, it is considered more as a secondary product rather

than a waste or residue.

• Palm Oil Fronds (POF) are a residual stream at the cultivation site. Primarily, the fronds are

left on the field as mulch, with minor use as fodder or thatching. The POFs are generated

mostly during the FFB harvesting. Typically, one or two leaves are cut per bunch. The

nutrients from POF are made available for soil fertilisation by spreading the fronds on the

soil over the entire lifetime of a plantation.

• Palm Oil Trunks (POT) are also a plantation residue stream , like the POFs. The trunks are

high in ash and moisture content (>70%). Most of the trunks are currently left in the field as

mulch. In contrast to POFs, trunks are available only every 25 years, when trees are

replanted. Generally, the old trees are chipped and then used as local organic fertiliser,

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being available only for a relatively short period of time as decay in the tropics is very fast,

and many nutrients are leached out by heavy rainfall.

• Palm Oil Mill Effluent (POME) is a combination of three different liquid wastes from the oil extraction process, namely the condensate from bunch sterilisation (0.6 ton/ton of produced oil), the sludge from oil clarification (up to 2.5 ton/ton of produced oil) and the hydro cyclone effluent from kernel processing. Overall, POME is primarily composed of clarification sludge. The dry matter content is low, less than 6%. Such large water content leads the POME to be mostly decomposed in open ponds, although methane recovery is slowly becoming more widespread.

Figure 2 – Images of the palm oil extraction process and final products [4].

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2.3 The Availability of Palm Oil Residues in Malaysia

Palm oil is a well-established global commodity for the food sector, and, with an annual production

reaching 62 Mton in 2016 [2], it surpasses every other crop oil. Malaysia’s share is approximately a

third of this global supply, with almost 20 Mton/yr (see Table 1). Malaysia is the second major

producer and exporter after Indonesia [3]. As a consequence, Malaysia also has one of the highest

volumes of the associated processing residues.

Unit Value

Crude Palm Oil Mton (drybase (d.b.)) 19.7

Palm Kernel Mton (d.b.) 4.5

Fresh Fruit Bunches Mton (d.b.) 57.2

Total Area Harvested Mha 4.7

Table 1 – Malaysian palm oil data for 2014 , main products generation.

The size of the Malaysian palm oil residues generation is so impressive (Table 2) that these streams

are considered among the largest worldwide available biomass streams with no or suboptimal use.

Almost 70% of the fresh fruit bunches’ (FFB) mass remains as waste in the form of empty fruit

bunches (EFB), palm kernel shells (PKS), palm kernel meal (PKM), mesocarp fibres (MF) and liquid

palm oil mill effluent (POME) after pressing. Additionally, large quantities of fronds and trunks are

generated during harvesting and/or after the lifetime of a tree. Currently, to a large extent, these

residues are not recycled or upgraded but left decaying and posing an environmental threat [4].

Flow (Mton/yr

drybase)

Dry matter

(%wt)

Main use

Empty Fruit Bunches (EFB) 13.6 ~ 40 Discharge

Palm Kernel Shells (PKS) 4.5 75 to 90 Energy Recovery

Palm Kernel Meal (PKM) 2.4 ~ 60 Fodder

Mesocarp Fibres (MF) 12.4 60 to 83 Energy Recovery

Palm Oil Mill Effluent (POME) 2.9 <6 Discharge

Palm Oil Fronds (POF) 47.3 30 to 50 Left in the fields

Palm Oil Trunks (POT) 13.4 15 to 30 Left in the fields

Table 2 – Malaysian palm oil data for 2014, main residues generation [4] on a dry basis.

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2.4 The Market Potential of Malaysian Palm Residues

From the missions to Malaysia, covering the mainland as well as Sarawak and Sabah, some

important lessons were learned with respect to the national and local ambitions and practices. An

important incentive for a more sustainable use of residues comes from the Malaysian National

Biomass Strategy (NBS2020), from which for instance measures for the mitigation of methane from

POME are taken.

Residues to biogas for power-heat or upgrading:

It seems obvious that most of the POME will stay on-site at the mill site (or nearby) due to its large

volume and high water content. Many mill sites are at remote locations, especially on Sarawak and

Sabah. With excess biomass residues to make energy at these locations and few other local

economic activities, the driver to treat the POME for recovering the methane by digestion comes

from national legislation that aims to reduce GHGs more than from the desire/need for energy

recovery. Whereas a coupling to the grid for produced biogas can be found on the mainland and

close to urban areas, the remote mill locations lack an incentive other than the compulsary

reduction in GHGs. Still, when recovered, the methane could be used at the mill site for energy

generation, replacing part of the current MF and PKS that can be exported or used for higher-end

products. Alternatively, methane can be consolidated to compressed natural gas (CNG) for local

transport or rural development for areas not connected to the grid. The solid residue after digestion

can be composted and be part of the fertilisation schemes on the plantation or for other local

agriculture. The use of the digestate for fertilisation is mostly regarded as too expensive due to

transport costs back to the plantation. To speed up this transition, an increase in market potential

for MF and PKS could create a market pull and improve the chances for biogas use at the mill site.

Residues upgrading to commodities:

The fact that Malaysia, and certainly Sarawak, is blessed with excessive energy resources (oil,

hydropower and biomass) is certainly a weakness in any business case transforming residues to

energy carriers. Energy is relatively cheap, and the easiest (cheapest) application for residues would

normally be local energy production, avoiding the cost of transport and storage. To gain more

flexibility and less dependency on market variation, the idea of bio-residues to commodity products

with a constant quality was recognised as an important opportunity. This was certainly also inspired

by a visit to PETRONAS, Malaysia's fully integrated oil and gas multinational. PETRONAS already has

research and development lines on bio-fuels and products based on palm oil. Bio-fuels and products

from bio-residues are investigated only on a laboratory scale at the moment. When targeting larger

scale processes, a constant quality of the feedstock/fuel becomes a key issue. Pre-treatment

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techniques could be suitably located at the mill sites with excess energy available. Pre-treatment

could then play a major role in reducing transport and other logistic costs but also provide a constant

product quality that would make the lives of the end-users so much easier. Because Palmares has

partners doing exactly that, providing pre-treatment techniques for constant commodity quality, it

will be one of the main business opportunities for Palmares’ partner companies. At the mill site, an

overal plan to manage biomass streams and the energy generation and use is required. It will be

another focal point as Palmares’ partners can bring in valuable expertise on this issue.

Financial support for local renewable energy:

To use the energy potential from POME locally some extra incentives may be necessary. The

Sustainable Energy Development Authority (SEDA) has already developed a feed-in tariff (FIT) for

biogas delivered to the grid on the mainland. Biogas can be generated by the digestion of wet

streams as well as by the gasification of dry biomass streams, upgraded to CNG for local

transportation, or rural areas, or added to fossil liquefied natural gas (LNG) to improve the footprint

of the gas exported and used worldwide. Electricity from biomass can be generated in numerous

ways and can either be sold to the grid or be utilised off-grid on the palm oil mill site. Rather than

providing partial solutions associated with one technology, Palmares proposes integrated solutions

with scenarios that incorporate the integration of all technologies necessary while taking into

account the local situation and the business case as well as the environment.

Use as fertilizer:

Overall, more than 33 Mton of dry biomass residues (EFB+MF+PKS+POME, see Table 2) are

generated at palm oil mill sites (excluding fronds and trunks at the plantation). Concerning EFBs (i.e.

the most under-utilised stream), their economic value as a potential artificial fertiliser replacement

is estimated at between $2.1 and $3.3 per ton, while as a fuel for power generation these figures

would rise by a factor of 3.5 [1].

Export of pellets for energy generation:

Just looking at the EU, a total lignocellulosic biomass demand of 650 Mton (dry weight) has been

estimated for the 27 EU countries within the National Renewable Energy Action Plans (NREAPs).

Additionally, the need for importing lignocellulosic biomass by 2020 in the EU 27 was estimated

between 50 and 150 Mtons [4].

An increasing market potential for biomass is evident for Korea and Japan, which are also located at

shorter transport distances than the EU. Especially in Japan the market chances for biomass pellets

to generate bio-energy have risen sharply from the introduction of a FIT for energy generated from

biomass. On the other hand, the quality criteria are very strict, especially with respect to the ash

content and more specifically the alkali (salt) content in the biomass. Without any modification the

EFB would not meet the quality criteria for Japan.

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Figure 3 – Regions of biomass export and volumes going to Korea and Japan. 2017 data by BiomassMagazine.com.

Wood pellet imports into South Korea and Japan have grown exponentially in the past few years. In

2017, South Korea imported 2.4 metric tons (MT) of wood pellets – 20 times what was imported in

2012. Japan is currently a smaller market, but its growth has also been impressive. Japan imported

over 0.5 MT in 2017, a seven-fold increase from 2012.

South Korea’s biomass demand has been supported by its renewable portfolio standard, which

requires all energy companies with an installed capacity exceeding 500 MW to obtain an increasing

share of their electricity from renewable energy sources. To satisfy their renewable portfolio

standards (RPS) requirements, generators can either produce their own renewable energy

or purchase renewable energy certificates (RECs) from other renewable energy generators.

In Japan, the market has evolved differently from South Korea and instead has been supported by a

FIT scheme that provides a 20-year subsidy to firms producing renewable energy. Biomass,

specifically under the general wood category, has proved hugely popular. By March 2017, almost 12

GW of biomass projects had been approved under the FIT scheme, far exceeding the quantity

envisaged under Japan’s Best Energy Mix 2030 scenario of 2.7 to 4 GW.

Another factor likely to encourage demand for (biomass) wood pellets is the high level of

competition for biomass supply in SE Asia; although there are abundant resources of PKS,

transportation limitations and its current use by palm oil mills will severely limit exports. Using other

energy sources at the mill site would free up the PKS for export. It could potentially also reduce the

use of virgin wood in cases where sufficiently large volumes and good quality can be delivered for

export. Quality issues for EFB as fuel are a concern. Pre-treatment processes and standardisation to

commodity products could improve the fuel to the right quality and help gain confidence in bio-

residues as energy feedstock.

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3. Dry Matter, Energy and Nutrients

Flows Analysis

3.1 Dry Matter Flow

As is shown in Figure , the Malaysian palm oil plantations’ yield consists of roughly 50% residues (i.e.

frond and trunks) and 50% fresh fruit bunches. Fresh fruit bunches are entirely sent to be treated in

the mills. The fronds and trunks are left in the field as these can supply nutrients and save costs on

artificial fertilisers. In fact, every plantation owner will try to maximise the FFBs’ yield by being

generous with fertilisers only as long as this is cost-effective.

Figure 4 – Dry matter balance (across the palm oil supply chain in Malaysia). Flow size is proportional to Mton/yr.

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The use of POFs and POTs for fertilisation is partially driven by the knowledge that organic material

is very important for good soil quality. However, the poor infrastructure for their removal and the

lack of alternative applications are also drivers to leave all plantation residues in place and even

return mill residues to the fields (e.g. EFBs). Economic drivers are more important than optimised

fertilisation schemes.

Plantations’ dry matter yield (Mton/yr):

Total 117.8 To:

FFB 57.2 Palm Oil Mill

POF 47.3 Field or Discharge

POT 13.3 Field or Discharge

Palm oil mills’ dry matter balance, including palm kernel processing (Mton/yr):

Total Input 57.2 From: Total Output 57.8 To:

FFB 57.2 Plantation CPO 19.7 Products

MF 12.4

8.9 CHP

3.5 Products

PKS 4.5

3.5 CHP

1.0 Products

PKO 2.4 Products

PKM 2.4 Products

EFB 13.4 Field/Discharge

POME 2.9 Field/Discharge

Table 3: Plantations’dry matter yield (in Mton)

Concerning the palm oil mills, the incoming 57.2 Mton of FFBs are primarily converted into 19.7

Mton of CPO, showing an oil yield of 34%. Furthermore, the recovery of PKO through palm kernel

processing adds up to 2.4 Mton per year. From the same kernel treatment, another 2.4 Mton of

kernel meal are used as product, namely cattle fodder. A fraction of the remaining residues is used

to generate energy through combustion, namely 22% of the entering FFB, in the form of kernel shells

(3.5 Mton) and fibres (8.9 Mton). Additional amounts of kernel shells and fibres are used to

manufacture final products, 1.0 and 3.5 Mton, respectively. The empty fruit bunches’ yield is

approximately 25%, with 13.6 Mton of dry matter per year. This stream is exclusively discharged or

used for field applications. The same holds for the POME, which is most of the time completely

decomposed in open ponds and hence emits a large quantity of GHGs (CO2 and some methane) to

the environment. Fortunately, increasingly more recovery of the methane is taking place although

often only by covering the pond and flaring the accumulated gas.

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3.2 Energy Flow

Concerning plantation biomass energy output the FFBs take the largest fraction, with 60% of the

plantation energy yield (Figure ). Given a total biomass yield of 118 Mton/yr and an average energy

content of 22 GJ/ton, the total energy content is 2.6 EJ/yr and a residual 40% is left in the fields as

fronds and trunks. These streams have energy flows of 0.79 and 0.28 EJ/yr, respectively. The 1.63

EJ/yr of the FFB are further processed within the mills. Most of the energy is transferred to crude

oil, specifically 48% of the entering flow. EFBs and MFs are the residue streams that retain the

highest amount of energy, with respectively 0.28 and 0.26 EJ/yr.

Figure 5 – Energy balance (as higher heating value) across the palm oil supply chain in Malaysia. Flow size is proportional

to PJ/yr.

The CHP generally has a low electric efficiency, as the need for electricity is far lower than the

need for heat. Here a 3.6% of HHV electrical efficiency was assumed. The thermal efficiency of the

CHP was assumed 66% of HHV. This means that 30% of the heat leaves the CHP with the off

gasses. It should be taken into account that the fibres are wet and therefore a considerable

amount of energy is used to evaporate water, this explains the low efficiency.

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In an average oil mill of 50 ton FFB dry matter per hour, the CHP is fed with 7.7 ton/hr of mesocarp

fibre and 3 ton/hr of palm kernel shells [9]. 150 GJ/hr of heat is delivered to the oil palm mill as

steam and 8.2 GJ/hr is delivered as electricity. Usually some of the electricity is delivered to the

local grid.

Plantations energy yield (PJ/yr):

Total 2.70 To:

FFB 1.63 Palm Oil Mill

POF 0.79 Field/Discharge

POT 0.28 Field/Discharge

Palm oil mills energy balance, including palm kernel processing (PJ/yr):



MF 0.26

0.19 CHP

0.07 Products

PKS 0.09

0.07 CHP

0.02 Products

PKO 0.10 Products

PKM 0.05 Products



Table 4. A typical palm oil mill energy balance

The overall energy balance based on the calorific value in the streams shows the following:

Of the total mill input (1.63 EJ/yr), 48.5% of the calorific value is in the primary product, 14.7% in

secondary products, 16.0% is used for energy generation (including heat losses) and 20.9% of the

energy content entering the mill is lost (0.34 EJ/yr).

However, from the plantation perspective a lot more is left in the field in the form of trunks and

fronds than the calorific loss at the mill site. This represents 1.07 EJ/yr (three times as much as the

calorific loss at the mill site). The fronds, however, represent an important nutrient source for the

plantation.

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3.3 Nutrients Flow

Starting from the nitrogen flow, as shown in Figure 6, the balance includes both the plantation and

the mill steps. Nitrogen input to plantations are human-added fertilisers and natural uptake from

the soil. Then, nitrogen output from the plantations is through three streams, the FFBs, POFs and

POTs. In addition, part of the fertiliser nitrogen is not fixed in biomass-growth but lost by leaching

into the soil. Fronds and truncs are assumed to be left in the field. During decay of fronds and trunks

and through soil losses and mineralization some of the nitrogen will be lost. The field loss reported

is a net loss of nitrogen. Overall, 773 kilotons (kton)/yr of nitrogen are used within the palm oil

plantations. The fertiliser input and soil uptake are roughly the same. Looking at the outputs, the

largest fraction of nitrogen stays on the field, as fronds, trunks and fertiliser losses. These losses

equal 77.7 kton/yr. The FFBs contain approximately 40% of the incoming nitrogen. Concerning the

balance over the mill step, 310.7 kton of nitrogen are fed through the FFBs. The greatest fraction of

this nitrogen is embedded within products (e.g. animal fodder) or fuels (~65%). However,

approximately 109 kton/yr are left in the field or discharged to the environment through the EFB

and POME residue streams.

Figure 6 – Nitrogen balance across the palm oil supply chain in Malaysia. Flow size is proportional to kton-nitrogen/yr.

Page 22 of 54

Plantations nitrogen balance (kton-nitrogen/yr):


Fertiliser 388.4 External FFB 310.7 Palm Oil Mills

Soil 384.3 Field POF 330.9 Field/Discharge


Fertiliser 77.7 Field/Discharge

Palm oil mills nitrogen balance, including palm kernel processing (kton-nitrogen/yr):



MF 86.8

62.1 CHP

24.6 Products

PKS 20.1

15.5 CHP

4.6 Products

PKO 0.0 Products

PKM 64.8 Products



Table 5. – Nitrogen balance across the palm oil supply chain in Malaysia

Page 23 of 54

Phosphorous experiences a large fertiliser loss as it is immobilised by soil interactions, estimated to

be 227 kton/yr. With the FFBs roughly 25% of the phosphorous flow, meaning a flow of 75 kton/yr,

is sent to the mills.

Figure 7 – Phosphorous balance across the palm oil supply chain in Malaysia. Flow size is proportional to kton-

phosphorous/yr.

Page 24 of 54

At the mills, phosphorous is largely retained within the EFBs and the MFs. Oils and kernel shells

retain almost negligible fractions – combined less than 1% of the total phosphorous input.

Considering all the mill residues, 34% of the phosphorus is discharged, while 47% and 19% are

contained within solid fuels and products, respectively.

Plantations phosphorous balance (kton-phosphorous /yr):


Fertiliser 944.2 External FFB 236.1 Palm Oil Mill




Palm oil mills phosphorous balance, including palm kernel processing (kton-phosphorous/yr):



MF 99.1

71.0 CHP

28.1 Products

PKS 0.7

0.5 CHP

0.2 Products

PKO 0.0 Products

PKM 14.3 Products



Table 6. Phosphorous balance at the plantation and at the mill site.

Page 25 of 54

In contrast to the other nutrients, potassium is largely retained within the fronds and trunks at the

plantation sites. Fertiliser losses are assumed to be in blance with the potassium release from the

soil. The FFBs retain 65% of the potassium taken up by the palm. POME, EFBs and MFs are the main

potassium streams, with 162, 205 and 149 kton/yr, respectively. Negligible potassium flows end up

in the oils, PKM and PKS. A total of 29% of the potassium is embedded in solid fuels and is finally

returned to the soil in the form of ashes. On the other hand, 68% of the potassium is directly

discharged through the POME and EFB streams if they are not taken back to the field. Concerning

the end products, these retain only 11% of the potassium, mostly through the MFs and PKM.

Combining the combustion ashes with POME and EFBs, a total of 68% of the potassium could be

returned to the fields or is otherwise directly discharged.

Figure 8 – Potassium balance across the palm oil supply chain in Malaysia. Flow size is proportional to kton-potassium/yr.

Page 26 of 54

Plantations potassium balance (kton-potassium/yr):


Fertiliser 537.7 External FFB 537.7




Palm oil mills potassium balance, including palm kernel processing (kton-potassium/yr):



MF 148.7

106.5 CHP

42.2 Products

PKS 6.7

5.2 CHP

1.6 Products

PKO 0.0 Products

PKM 15.5 Products



Table 7. Potassium balance of the plantation and on the mill site.

3.4 Implications from the Energy and Nutrient Flow Analyses

Based on the energy balance of the palm oil mill sites described in Chapter 3, it can be concluded

that only 17% of the incoming calorific value of the biomass is used for energy generation. This is

covered in practice by combusting the mesocarb fibre and/or palm kernel shells. MF and PKS are,

however, easily applicable for export and/or higher-end products and ideally would be replaced by

some of the un-used streams. Of the total mill input (1.63 PJ/yr) 20.9% of the energy content is un-

used. Some of the energy can potentially be used on-site by methane generation from POME in

cases where it would be processed in a digester, which is good from a GHG perspective. However,

it contributes relatively little in term of energy content. The largest energy-containing residue

stream available from the mill site is the EFB. It could replace MF and PKS in case technically suitable

as fuel.

An even larger energy content is left in the field in the form of fronds and trunks, and this represents

1.07 PJ/yr (three times as much as the unused calorific content at the mill site). The fronds, however,

represent an important nutrient source for the plantation.

Page 27 of 54

Various authors provide different fertilisation amounts which are, however, different numbers due

to different underlying assumptions. Below three different schemes are compared. The AIM numbers

are based on personal communication.

kg/ha/yr Woitties c.s.(2017) AIM this study

N 260 162 150

P 130 296 120

K 350 310 120

Table 8. Different N, P, K fertiliser quantities by various authors .

Woitties et. al. (2017) calculated fertilisation based on minimum fertilisation amounts below which

growth limitation would occur. The amount of trees per ha was assumed to be 140 .

AIM calculated fertilisation based on practical data and 148 trees/ha

In this study the fertilisation was calculated based on an assumed uptake efficiency of the nutrient,

the composition of the FFB and the amount of FFB harvested per hectare. For example, for Nitrogen:

A plantation produces per ha, 12.2 ton (dry matter) FFB and 12.94 ton (dry matter) Fronds and Trunks.

The Nitrogen content is 0.436 % wt/wt, so there is a need of 110 kg N/ha/yr to be supplied to the

palm. With an uptake efficiency of 71% the total fertilizer demand is 150 kg N/ha/yr.

Fertilizer efficiencies from the Sankey diagrams are:

Nitrogen: 60%

Phosphate: 25%

Potasssium 100%

Phosphate fertilizer efficiency is low. This is (mainly) caused by immobilisation of phosphate in the

soil. This phenomenon is highly soil dependent. After many years the soil may become saturated and

phosphate efficiency can go up.

Nitrogen fertilizer efficiency is higher. Losses occur due to mineralization (production of nitrogen gas),

runoff and infiltration. Cover crops may fix nitrogen and increase apparent nitrogen fertilizer

efficiency.

Potassium fertilizer efficiency is assumed 100%. Some of the potassium is lost (via runoff), but

potassium may also be released by the soil from erosion of rocks. This is also very soil dependent.

When comparing the nitrogen, phosphorous and potassium (N,P,K) fertiliser flows of the various

streams (see Chapter 3), it can be clearly seen that the fronds are an important source of the N and

K being returned to the soil by leaving the fronds on the plantation site. For N input on the

plantation, the stream of fronds represents 42.8%, even more than the 40.2% removed by

harvesting the fresh fruit bunches. For K, the fronds represent 45.0% of the plantation input versus

39.5% taken away by FFB. Based on the N and K release, the fronds can be regarded as an important

product in the fertilisation scheme and preferably should be left in the field as long as CO2 emissions

from decay would not be in excess of the CO2 uptake by plants. Because the fronds are on top of

the soil and the decay is very slow, this is not likely to be the case. The palm fronds can hence be

added to the fertilising products and part of a beneficial circular use of nutrients. This is also in line

with the current practice and should preferably not be changed.

Page 28 of 54

The only residue stream with some significant amount of P are the EFB, with 11.1% of the plantation

input. Because the wet and dense EFB could potentially result in significant GHG emissions during

decay as well as attract pests and diseases, some pre-treatment or energy generation first would be

preferred. Application could then be in the form of digestate (compost), combustion ashes and/or

biochar. These would also vary in the chemical form of phosphorous, depending, for example, on

the temperature of treatment and might alleviate some of the serious leaching/adsorbtion problem

(although this is highly speculative at the moment and more knowledge is needed).

In terms of bringing in the N and K lost to the plantation by harvesting FFB (40.2% N and 39.5% K),

the return of EFB would cover 10.6% of N and 15.0% of K. Trunks would be available only when all

the palm trees are cut at the end of their lifetime. N and K would be available in the first year of the

new plantation trees as the trunks are shredded and mixed into the soil. The GHG release from

decay from the large amount of organic material could potentially outweigh the benefit of N and K

fertilisation as the bulk of the material will be decomposed within one year. Whether it would be

beneficial to take the trunks (or some percentage) off the field to avoid excess CO2 generation could

be a topic for a study on improved fertilisation schemes as well. The nutrients (P and K)of trunks

could also be applied in a different form, such as in the form of biomass combustion ashes (after

energy generation) or as biochar (nutrients plus carbon after making energy from the volatile

compounds in the biomass).

Page 29 of 54

4. The Current Challenges

Although many challenges can be identified when aiming for a more sustainable use of biomass

residues, a few have been chosen here to be explained in more detail. First, the reduction of GHG

emissions shows a link between biomass residues for energy generation and the optimised

fertilisation at the plantation, which will be explained. Second, with the nutrient flow analyses and

the energy content of the biomass residues in combination with the energy need at the mill site, a

first assessment is made as to which streams are better options for fertilisation and which for energy

generation or higher-end products. The technical difficulty of using the residues with high nutrient

content as energy sources in conventional installations is described last. The assessment of better

options for fertilisation or energy generation also predetermines some of the choices made in the

alternative processes described in Chapter 5.

4.1 GHG Emissions Reduction

As can be seen from the NASA image shown in Figure 9, some areas were identified to have

exceptionally high CO2 release numbers for the 2015–2016 (El Niño) years and, as a result, have a

major impact on climate change. The explanations given [5] for the Asian, the African and the

Amazon regions are as follows:

1) The natural in-field combustion of biomass due to peat and forest fires in addition to human-

related open air combustion for residue volume reduction/disposal in extra warm and dry

weather.

2) The decay of biomass (in/on soil) being faster, that is, more CO2 is released than is taken up

by photosynthesis, also due to higher temperatures and dryer conditions than usual.

Ad 1. Forest and peat fires directly release CO2 into the atmosphere without making use of the

energy generated. The same holds for bio-residues’ combustion as a quick method to reduce the

waste volume, reduce disease and pest pressure in the field and make use of the ash components

for fertilisation. Whereas MFs and PKSs from palm residues are often combusted at the mill site with

energy recovery, replacing fossil fuels, some other residues are still burned in the field or at disposal

sites in Asia.

Ad 2. Since palm oil cultivation occurs in tropical areas, the decaying process is very rapid, driven by

the local temperatures and air humidity. At high decaying rates of high amounts of organic matter,

the fraction of CO2 emitted into the air will rise dramatically, as shown in the NASA picture (CO2

uptake by plants’ photosynthesis is smaller than the release from decaying processes). This is

generally true not only for rain forest areas but also for individual fields. In addition, the

decomposition of organic matter under anaerobic conditions will release emissions of gases with

larger global warming potential than carbon dioxide, such as methane. The latter refers to the POME

decomposition in open ponds without capturing the gases released in it. The decay of, for instance,

EFB on disposal piles will also generate CO2 and other GHG emission gases. The release of methane,

nitrogen dioxide and other GHGs from EFB adds up to 4.7 tonCO2eq./ha.yr [4].

Page 30 of 54

The fact that major CO2 emissions can occur through the biodegradation of bio-residues that are

disposed of or left in the field in excess of the local plant uptake shows that optimised fertilisation

schemes could be highly beneficial. In cases where excess biomass residues could replace fossil

fuels, overall GHG emissions are reduced as well.

Figure 9 – Graphical representation of areas with exceptionally large CO2-releases in the El Niño 2015–16 years together

with notifications where the areas were exceptionally warm and/or dry [5]. In this study, the first 28 months of data from

NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite were analysed. It is shown that carbon release to the atmosphere

rose by 2.5 Gtons for these three regions indicated, compared to 2011. Besides carbon dioxide, OCO-2's high-resolution

spectrometres can observe solar-induced fluorescence, or SIF. This radiation, emitted by chlorophyll molecules in plants,

indicates that photosynthesis is occurring. SIF provides valuable insight into global photosynthesis because it captures

photosynthesis during the growing season and also its slowdown, for example, over evergreen forests in winter, when

trees maintain chlorophyll but stop absorbing carbon dioxide from the atmosphere.

4.2 Bio-residues for Fertilisation or Energy Generation from a GHG Perspective?

From the implications of the flow charts presented in section 3.4 and GHG emissions by decaying

processes described, a form of competition between fertilisation and energy generation becomes

apparent. The main lines can be summarised as follows.

Palm oil residues can contribute to GHG emissions through various pathways. The aimed-for options

to save on GHG emissions compared to the current situation are

a) Bio-energy generation replacing fossil fuel and avoiding combustion as a disposal route

without energy generation.

b) Optimised fertilisation schemes bringing as much nutrients back to the field from the

residues as new growth requires (not more) and avoiding as much as possible the use of

(fossil- energy-intensive) artificial fertilisers.

As climate change and the desire to reduce GHG emissions is a global issue, the excess energy

content of the residues could also be exported to replace fossil fuel abroad as long as transport

would not annihilate the intended CO2 reduction. A profitable application of the residues as fuels

or feedstocks (market pull) would directly decrease the desire to burn it or let it decay on the spot.

Page 31 of 54

The development of optimised fertilisation schemes can potentially minimise residues emitting

more GHGs by decay. A combination of energy generation with nutrients being returned to the field

is possible as well. The upgrading of palm residues to fuels, products and advanced organic soil

improvers (e.g. composted digestate and biochar) opens different opportunities to make additional

profits and/or reduce costs while mitigating GHG emissions. However, to effectively realise such

integrated scenarios, the main remaining questions to be answered from GHG mitigation are: To

what extent are the residues (e.g. POTs, composted POME or EFBs) applied to the soil effectively

used by the growing biomass, and to what extent do they contribute to GHG emissions? This is a

question that cannot be answered at the moment but needs to be addressed in future work. The

optimum amount of bio-residues available, leaving optimum nutrient amounts for food production,

remains unknown and must be addressed first. In the meantime technical feasibilities and economic

viability studies can be performed for various scenarios.

4.3 Un-utilised Palm Residues for Energy Generation

So far it has been identified 1) that POME is best treated by digestion for methane recovery and the

solid digestate used as a possible fertiliser product; 2) that the fronds are best left in the field for

fertilisation; 3) that PKM has a good and valuable application as animal fodder; 4) that MF and PKS

are already used as fuel; 5) that for the trunks it still remains to be seen what the potential is with

regard to volume for applications other than fertilisation, depending on the GHG-emission by decay

and 6) that the largest under-used stream remaining is the EFB. The fact that EFB is currently hardly

used has two main reasons: first, it is very difficult to do any kind of pre-treatment (as can be guessed

from its appearance; see Figure 10, top image), and second, it contains a high alkali content which

results in low melting temperatures when used as an energy source in conventional installations.

Comparing EFB with the Currently Used Residues

EFB is the largest underutilised residue stream both in terms of dry matter volume and energy flow.

When using MF and PKS, the addition of EFB for energy generation would largely exceed the mills’

energy demand, resulting in low drivers to optimise the energy efficiency and diversify the fuel

source. When comparing the EFB, MF and PKS for energy generation, it is evident from Table 9 that

EFB has a higher moisture content, which is unfavourable. However, the need for drying is not the

only problem. The other problems are the texture and the K-content.

Unit EFB MF PKS

Moisture %wt 60 17–40 10 - 25

HHV MJ/kg (d.b.) 17.5–19.0 19.7 20.5–21.5

LHV MJ/kg (d.b.) 6.4 13.0 15.1

Ash %wt (d.b.) 1.6–7.7 3.5–8.4 2.7–4.4

K %wt (d.b.) 2.37 1.18 0.15

Table 9 – Combustion properties of different palm oil mill residues [4].

EFB Combustion Properties

Page 32 of 54

The challenges related to the use of EFB lie in its morphology/texture and combustion properties.

The tough fibrous material, as shown at the top of Figure 10, is difficult to cut into smaller pieces

and to prepare it for feeding into thermal conversion installations. Furthermore, EFB contains high

ash and potassium levels. The result is s melting of the ash at temperatures in conventional

installations, resulting in high fouling and ‘lumps’ obstructing normal operation. (See bottom left in

Figure 10.) The morphology and chemical composition of the grey lumps were studied at ECN>TNO

by scanning electron microscopy (SEM). The morphology, pictured at the top right of Figure 10,

shows fully molten material (grey zones), bubble holes (black zones) and some metallic material

(white zones) that has been segregated from the melt or was never fully incorporated. The ash

composition as determined by EDX under the SEM and shown in the lower right of Figure 10

indicates the presence of a silicate melt with high levels of alkali salts as KCl. The high salt content

causes a lower ash melting point compared to other residues.

EFB (%wt, ash d.b.)

SiO2 12.12

Na2O 0.09

K2O 55.4

Chloride (Cl) 6.84

Figure 10 – Top left: EFB material (cut and dried); bottom left: molten rocks of ash from a commercial boiler in Malaysia

using EFB as fuel; top right: an image of the molten rock taken by SEM; bottom right: overall analyses of the molten grey

phase in the SEM image.

These findings confirm that the ash composition of the fuel is the main parameter responsible for

the molten ash phase in the boiler. A first estimate of the ash melting point is around 770 °C with

an advised safety margin of ± 50 oC, while nearly all combustion processes are above a 1000 oC.

Although it is not completely impossible to generate energy from a fuel with such a low melting

temperature and high ash content, it is unlikely to be economically very attractive in conventional

Page 33 of 54

combustion installations. The slagging and fouling will severely limit the operational hours before

extensive cleaning must take place, and hence the downtime of such an installation would be large.

Two lines of reasoning can be followed for technical modifications that make the conversion of EFB

to energy possible:

1) Wash out the salt content to avoid the low melting temperatures of the remaining ash.

2) Design a conversion technique that can operate at low enough temperatures to avoid ash

melting (<700 C).

Both lines of reasoning have been followed for new technology development, and these are

incorporated in the alternative process schemes described in Chapter 5.

Although earlier it was recognised that bringing EFB directly to the field as a fertiliser stream would

likely have some adverse effects, such as high CO2 and methane emissions by decay and an increase

in pests and diseases, it would be good if the high levels of K in the EFB could still be used for

fertilisation. By using the leached out salts and/or the ashes or biochar products (holding most of

the K) from the technological choices described above, the K nutrients could still be used.

Page 34 of 54

5. Alternative Processes for Energy

Recovery, Fuel Production and

Improved Fertilisation

These alternative process schemes focus on the upgrading of EFBs and POME, given their large

centralised availability and under-utilisation. This work focuses on the combination of thermal and

fermentation conversion technologies to maximise the energy yield from the two residues while

minimising GHG emissions. The fuels produced can be used locally or elsewhere.

5.1 Objectives of the Alternative Processes

Given the identified market opportunities and environmental and technical challenges, the

realisation of new routes to valorise palm residues must aim at the following general objectives:

• Reduce costs or increase profits;

• Mitigate GHG emissions due to uncontrolled decaying and/or incineration without energy

recovery;

• Upgrade functional specifications to meet fuel, industrial feedstock or product

requirements.

Focusing on the thermo-valorisation of EFBs, these objectives imply the following sub-objectives:

• Prevention of fouling and slagging;

• Water removal;

• Energy densification.

Concerning the valorisation of the POME via fermentation, sub-objectives are as follows:

• Maximisation of readily biodegradable matter;

• Minimisation of digestate generation;

• Minimisation of the concentration of recalcitrant components.

5.2 Alternative Process Concepts

Seven alternative process concepts are proposed for the upgrading of EFBs and POME, as shown in

Table . In this table, it is shown how the supply chain would be affected by the integration of these

concepts. The residues’ distribution among five applications is compared to the base case, which

depicts the current situation. Two alternative concepts do not include any form of pre-treatment,

namely the POME Digestion and POME digestion + EFB combustion options. The other five options

include a cold or hot pre-treatment of EFBs or both EFBs and POME. As can be observed, the

utilisation of a pre-treatment step promotes the complete utilisation of the residues and the

production of commodity fuels. Furthermore, advanced soil fertilisation techniques, such as the use

Page 35 of 54

of biochar, can be introduced to possibly achieve an even higher reduction of fertilisation expenses

and decaying biomass GHG emissions.

Table 10 – Alternative concepts (green without pre-treatment, red with pre-treatment) and their respective residues’

distribution per application. EFB: empty fruit bunches, MF: mesocarp fibres, POME: palm oil mill effluent, PKS: palm kernel

shell, PKM: palm kernel meal, POT: palm oil trunks, POF: palm oil fronds.

Energ

y Rec

overy

(CHP)

End P

roduct

s

Comm

odity Fu

el

Fert

iliza

tion

Discharg

e

Base CaseMF

PKS

MF

PKS

PKM

POT & POFEFB

POME

POME Digestion

MF

PKS

POME

MF

PKS

PKM

POT & POF

DigestateEFB

POME Digestion

+ EFB Combustion

EFB

POME

MF

PKS

PKM

POT & POF

DigestateEFB

EFB WashingEFB

POME

MF

PKS

PKM

EFBPOT & POF

Digestate

EFB TrrefactionEFB

POME

MF

PKS

PKM

EFBPOT & POF

Digestate

EFB TORWASH® EFB

POME

MF

PKS

PKM

EFBPOT & POF

Digestate

EFB GasificationEFB

POME

MF

PKS

PKM

EFBPOT & POF

Digestate

EFB Gasfication

+ Biochar Production

EFB

POME

MF

PKS

PKM

EFB

POT & POF

Digestate

Biochar

Page 36 of 54

5.3 Concepts Description

Base Case: This reference case represents a still common processing practice of palm oil mill

residues, as described in the previous chapters. Basically, MF and PKS are partially used within a

solid fuel CHP unit to supply energy to the mill. The rest is used to manufacture higher-end products.

At the same time, POME and EFB are mostly discharged without any utilisation.

MF & PKSPALM OIL MILLSOLID BURNER

(CHP)

DISCHARGEPOME & EFB

FEEDSTOCK FOR HIGHER-END PRODUCTS

Figure 11 – Base case concept for the treatment of palm oil mill residues.

POME Digestion: POME is a highly wet stream, better defined as wastewater than solid residue.

Given its low dry matter content, anaerobic digestion is the most suitable option to recover energy

while reducing its organic loading. This practice is indeed increasingly being deployed by palm oil

mills globally. However, as can be seen through the previous dry matter and energy balances, the

biogas is not sufficient to meet the mills’ energy demand. Thus, some additional PKS or MF must be

used within the mill CHP plant. However, the majority of these streams will be made available for

export. Furthermore, it is important to remember that most of the mills currently utilise solid fuels

(MF and PKS), thus an investment cost may be needed to switch to a biogas CHP unit. The

environmental gain is large when methane is not released. An estimate [4] is approximately 2.5 ton

CO2eq per ha palm plantation/yr.

Page 37 of 54

ANAEROBIC DIGESTION

POME DIGESTATEPALM OIL MILLPALM OIL

PLANTATION

SOLID BURNER(CHP)

MF & PKS

GAS BURNER(CHP)

BIOGAS

DISCHARGEEFB


Figure 12 – POME digestion concept diagram.

EFB Combustion: This concept is similar to the simple POME digestion, but it includes the

replacement of MF or PKS combustion with EFBs. However, as was explained in the previous

chapter, the direct use of EFBs will result in high operational costs due to fouling and corrosion. The

high potassium, silica and Cl content lower the ash melting point, making the EFBs a lower quality

fuel compared to MF and PKS. In this case, a large quantity of MF, PKS and EFB would be available

for export as fuels or products. Still, without any form of pre-treatment, EFBs will maintain their

cumbersome properties (e.g. bulky, biodegradable, high ash content, etc.), which would make them

not very attractive. Drying and pelletisation could be a possible option but at high energy cost and

poor product quality.

ANAEROBIC DIGESTION

POME DIGESTATEPALM OIL MILLPALM OIL

PLANTATION

SOLID BURNER(CHP)

EFB

GAS BURNER(CHP)

BIOGAS


MF & PKS

DISCHARGE

Figure 13 – POME digestion and EFB combustion concept diagram.

Page 38 of 54

EFB Washing: A first pre-treatment concept is the simple washing of the EFBs, which could be

implemented into the previous concept. This would result in reduced salts and attached sand

concentrations, improving the combustion performances of the EFBs. The washed EFBs could be

used as commodity fuel after drying and pelletisation. Simultaneously, the washing effluent could

be mixed with the POME to further convert the dissolved organic matter to biogas. However, the

drying energy cost is high, while the final fuel properties are of lesser quality than clean wood pellets,

regardless the reduced ash content and higher melting point. Due to excess energy availability at

the mill site, this upgrading could still be profitable. Drying could be achieved from residual heat

after energy generation.

Page 39 of 54

AN

AER

OB

IC

DIG

EST

ION

PO

ME

DIG

EST

AT

EP

ALM

OIL

MIL

LP

ALM

OIL

P

LAN

TAT

ION

SOLI

D B

UR

NER

(CH

P)W

ASH

ED E

FB

GA

S B

UR

NER

(CH

P)B

IOG

AS

FEED

STO

CK F

OR

H

IGH

ER-E

ND

P

RO

DU

CTS

MF

& P

KS

CO

MM

OD

ITY

FUE

L FO

R E

XPO

RT

WA

SHIN

GEF

BD

RYI

NG

&

PEL

LETI

ZATI

ON

WA

SHIN

G W

ATE

R

FUEL

PEL

LET

Figure 14 – EFB washing concept diagram, including POME digestion.

Page 40 of 54

AN

AER

OB

IC

DIG

EST

ION

PO

ME

DIG

EST

AT

EP

ALM

OIL

MIL

LP

ALM

OIL

P

LAN

TAT

ION

SOLI

D B

UR

NE

R(C

HP)

WA

SHED

EFB

GA

S B

UR

NER

(CH

P)B

IOG

AS

FEED

STO

CK

FOR

HIG

HER

-EN

D

PRO

DU

CTS

MF

& P

KS

CO

MM

OD

ITY

FUEL

FO

R E

XPO

RT

WA

SHIN

GEF

BD

RYI

NG

&

PEL

LETI

ZATI

ON

WA

SHIN

G W

ATE

R

TOR

REF

AC

TIO

NTO

RR

IFIE

D E

FBFU

EL P

ELLE

T

Figure 15 – EFB torrefaction concept diagram, including POME digestion and final drying and pelletisation.

Page 41 of 54

EFB Torrefaction: In cases where the heating value of the produced commodity fuel must reach a

higher value than that of clean wood pellets (e.g. closer to coal) and/or milling at the clients’

installations is an issue (not easy for the fibrous material), then the combination of washing and

torrefaction (i.e. a mild form of pyrolysis between 200 and 300 ⁰C) of the EFBs is a good choice. In

this case the quality of the final EFB fuel would be higher and the drying energy demand lower. In

cases where an optimised torrefaction concept is chosen with regard to energy efficiency, the

torrefaction process does not require any additional energy but can be operated by burning the

torrefaction off-gas. The product volume/quantity is lower than for the washed EFB-only, but the

quality and durability have improved significantly.

EFB TORWASH®: TORWASH® is a mild hydrothermal treatment at a temperature between 150 and

250 ⁰C [7]. It integrates washing and torrefaction within a single operational unit. First, working

under such mild conditions, it generates a digestible effluent. Therefore, POME and EFB can both be

treated through TORWASH®, enabling biogas generation through effluent anaerobic digestion. The

effluent is also enriched with the phosphorous that is dissolved from the EFB, improving its digestate

fertilisation value. Concerning the solid fuel product, the TORWASH® treatment enables the use of

mechanical dewatering to a larger extent, achieving dry matter content on a lab scale as high as

65%wt. Furthermore, combining TORWASH® with cold pre-washing, it is possible to achieve a high

removal of alkali salts, matching the clean wood pellets’ specifications. Although the overall

yield/quantity of the fuel pellets is reduced due to the loss of organic material and nearly all ash,

the quality is very much enhanced, making the fuel applicable for international export.

EFB Gasification: The gasification of EFBs is achieved at higher temperatures and at lower oxygen

levels than necessary for complete combustion. This process converts the solid biomass matter into

combustible gases, such as methane, carbon monoxide and hydrogen. The gasification temperature

could be kept as low as 750 °C, leveraging on the endothermic nature of the gasification process

and using a relatively wet fuel. Under these conditions, a gasifier, for instance a fluidised bubbling

bed, could be installed as the EFBs’ pre-treatment unit, and the produced gas can be combusted in

a burner for local heat recovery. A cyclone can be installed to remove most of the dust out of the

system before combustion. Although the system can achieve a relatively high energy efficiency,

maintenance costs will be also high, working not too far from the ash melting point. By converting

the gas to (steam and) heat, the most logical use would be for the mill factory to replace all currently

used MF and PKS, which can be used for higher-end products and/or export. Because the operating

temperature is relatively close to the melting point of the ashes, it could make sense to wash the

EFB before use to allow a larger and more secure window of operation.

EFB Gasification + Biochar Production: As an alternative to the previous system, a gasifier could be

operated at an even lower temperature (650 °C) in a co-production scheme for making biochar.

Under these conditions, the energy yield would drop to approximately 80% as the biochar carbon

product will yield approximately 20% of the calorific value. The low-gasification temperature avoids

the problem of ash melting altogether and leaves the high salt concentration (nutrients) in the

biochar for soil amendment [8]. When properly harvested from the hot zone and thus separated

from the gases at an early stage, this biochar is a tar-free and a highly porous product. It can be used

as an ingredient in potting soil (replacing peat) and applied at the nursery for new palm tree growth

or in compost and as a soil improver for poor soils, such as reducing the leaching of fertilisers. This

option can thus be regarded as a concept partly for energy generation (80% of the C) and partly for

Page 42 of 54

improved fertilisation and agricultural use (20% of the C). As for the previous case, combining this

EFB treatment and POME digestion enable the production of combustible gases for the energy

requirement at the mill, with an excess that could be used within other applications, such as an

upgrade to CNG for local transport. Fibres and shells will be completely available for other end

product applications. Whether the use of biochar at the plantation could be a measure to prevent

the 70% loss of phosphorous fertiliser is currently unknown and would require further research.

Biochar produced from woody

residues at ECN>TNO

SEM image from a biochar particle showing the highly

porous nature of the grain. The composition is >85%

carbon and most of the nutrients remain in the biochar (K,

Ca, P)

Figure 16 – Images of biochar as produced (left) and showing the high porosity in the SEM picture (right).

The conversion of EFB into biochar has been researched and its use as a soil amendment in

agriculture soils has been studied by various research groups. Today the main attention for biochar

is due to its recalcitrant, carbon-rich nature that is highly resistant to microbial degradation, making

it a very stable carbon sink. Organic materials, when left in the ground, will decompose, and a large

portion of their C will be lost during this decomposition process, leaving behind only a small C

fraction to be stored in the soil. Moreover, soils have limited capability to store C. The addition of C

into soils will indeed increase soil C levels but only up to a certain maximum level, usually within 5

to 20 years (Lal, 2004, 2011), and should these C additions cease or become infrequent, soil C levels

may start to decline, as observed by Comte et al. (2012). Hansen et al. (2012) carried out a life cycle

assessment (LCA) on the conversion of EFB into biochar in Malaysia and reported a maximum total

CO2eq savings of 210 kg per ton of EFB. Indonesia is estimated to have produced 28.1 Mton EFB (over

Page 43 of 54

2013, and even if 75% of this were to be returned to the oil palm plantations, a potential reduction

in CO2eq emission of 4.4 Mton per year could be achieved if the EFB are converted into biochar

instead. It can beassumed that similar savings in CO2eq apply for Malaysia as well).

Page 44 of 54

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Figure 17 – TORWASH® of EFB concept, including final drying and pelletisation and effluent digestion.

Page 45 of 54

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Figure 18 – Gasification of EFBs diagram, including a washing pre-treatment step and POME digestion. Whether the

washing is necessary is not completely understood, but it would allow a larger temperature window of operation.

Page 46 of 54

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Figure 19 – Low temperature gasification for the co-production of biochar – no washing pre-treatment step is required

due to the low temperature of the process; however, some drying with residual heat could be beneficial. In cases where

the POME digestion provides enough gas on-site, the low-temperature gasification and POME digestion can be uncoupled.

Page 47 of 54

5.4 Concept Choices for Local Variation

Digestion of POME

Environmentally, just the production of biogas through the anaerobic digestion of mills’ wastewater

would reduce the country’s CO2 emissions by 12%. Maybe even more importantly, it is also the

ambition of the Malaysian Government to bring this potential to realisation [1]. Therefore the

capturing of methane from POME digestion is being rolled out at the moment. Unfortunately the

methane is often flared to avoid the release but without using the energy potential of this natural

gas equivalent. This holds mostly for mill sites in remote areas and not connected to the grid. The

use of the methane as fuel in the mill factory should be stimulated for the remote mill sites. Using

MF and PKS elsewhere as bio-fuels or higher-end products would be an additional GHG emissions

savings.

In cases where more than just the POME digestion is considered, process integration including the

energy requirements of the mill would be highly beneficial, both economically and from a

sustainability point of view.

Washing of EFB and Upgrading to a Reasonably Good Fuel

The washing of EFB could be an option for any location with excess energy, which is every mill site.

The further upgrading options would depend on the local situation. Some pre-drying before

combustion on-site could be done with residual heat. But also torrefaction on-site to allow the

transport of fuel (pellets) in a more efficient way and with better durability would be a feasible

option for most mill sites. The effluent of the washing process could be treated in the same digester

as the POME. To allow some economy of scale, the EFB from a few mill sites could be brought

together in one location.

TORWASH® of EFB to a High-quality Fuel for Export

TORWASH® would be an option at the mill site because of the sharing of the digesting installation

with POME. In cases where the EFB from a few mill sites could be accumulated, the gas production

of the digestion installation could be raised as well as some economy of scale for the

TORWASH®process and pelletisation in the case of transport. Although the TORWASH®-ed fuel

would be a very good fuel on-site, it has reached such a good quality that it would probably be more

valuable as a commodity that can be traded internationally.

Gasification of Wet EFB

This concept can best be applied at the mill site because it requires less pre-treatment of the EFB.

Nonetheless, some economy of scale would make it economically more attractive, and the joined

processing of a larger volume of EFB from a number of mill sites (5–10) could be very beneficial.

Some pretreatment could still be necessary (e.g. washing) due to the high alkali content and hence

low-melting temperature of the ash. In cases where all energy must be used locally due to a remote

location, some upgrading to CNG might be useful.

Page 48 of 54

Low Temperature Gasification of EFB with Biochar Production

Similar to the wet EFB gasification, some economy of scale could be beneficial, and on one mill site,

the (dried) EBF could be collected from 5–10 mills. Because 20% of the energy content is contained

in the biochar, less excess heat is available. Because the biochar is more easily transported, the site

where the energy can be applied is still the preferred location for the installation , while for the

application of biochar in the fertilisation schemes, the material can be transported to the nursery,

the composting site or the plantation.

Many of the mill sites are governed in such a way that the milling of palm oil is the only primary

process, and the associated handling of residues is considered a burden. The excess of energy could

be an opportunity for other small businesses to develop at such locations. Especially businesses

making the most of the palm residues could be a valuable expansion of the local activities and

alleviate the mill director from a non-primary task .

Page 49 of 54

6. Alternative Higher-end Products

Oil palm fibres have a reported moisture content of 17 to 40%, making it difficult to store without

drying. The fibre is currently used as the primary boiler fuel at the mill site. However, if the energy

efficiency of the processing mill is increased, and biogas from POME is used for energy generation,

up to 100% of the palm fibre could become available for alternative uses. Oil palm mesocarp fibres

could be used to produce fuel briquettes or pellets. Briquetting is a mechanical treatment to make

biomass more uniform via compaction. Besides energy conversion, in principal oil palm mesocarp

fibre could be used as raw materials that are also considered for light-weight concrete, fillers,

activated carbon and other materials. Challenges come from the fact that fibres have a

comparatively high water content and also contain a considerable amount of nutrients. Still, the

moisture and nutrient content is generally lower than for EFBs, while the energy and lignin content

should generally be higher. As fibres are the main boiler fuel, fibre should only become available in

cases where a more energy efficient approach is adopted at the mill site and an alternative energy

generation source is available (Elbersen et al. 2013).

Kernel shells are primarily used as a boiler fuel, supplementing the fibre which is used as the primary

fuel. The remaining shells are often disposed of in the field or burned; however, in recent years PKS

have been sold as fuel around the world. Alternative uses for shells, besides energy, include use as

raw material for light-weight concrete, fillers, activated carbon and other materials. The shells have

a high dry matter content (>80% dry matter). Therefore the shells are generally considered a good

fuel with low ash amounts (especially low K and Cl content) (Elbersen et al. 2013), which will lead to

less ash agglomeration/fouling/corrosion or fewer ash melting problems. Of all the oil palm

residues, the kernel shells have the best properties as a bio-energy export commodity.

EFB have been suggested as a source of fibres for making paper. The chemical pulp of empty fruit

bunches has been achieved successfully by bleaching with a chlorine-free process to obtain a

brightness of 75–80%. The paper quality-obtained chemical pulps of EFB are comparable to

hardwood kraft pulp (KP) (Singh et al. 2013). A possibly even higher-end application could be in the

form of one or more green chemicals. When targeting larger-scale processes, such as bio-refinery,

the consistent quality of the feedstock/fuel becomes the key issue. Pre-treatment techniques could

be suitably located at the mill sites with excess energy. Pre-treatment could then play a major role

in reducing transport and other logistic costs but also provide the consistent product quality that

would make the lives of the end-users so much easier. Preliminary studies are only being excecuted

at the laboratory scale at the moment.

Page 50 of 54

7. Conclusions

By making mass balances for energy and nutrient flows, a first indication can be given for the

opportunities to use bio-residues from the palm oil industry without compromising on nutrient

availability and/or excess GHG emissions due to combustion for disposal or by decaying processes.

Based on the energy balance of the palm oil mill sites, described in Chapter 3, it can be concluded

that only 17% of the incoming calorific value of the biomass is used for energy generation. This is

covered in practice by combusting the mesocarb fibre and/or palm kernel shells. MF and PKS are,

however, easily applicable for export and/or higher-end products and ideally would be replaced by

some of the un-used streams. Of the total mill input (1.63 PJ/yr) 20.9% of the energy content is un-

used. Some of the energy can potentially be used on-site by methane generation from POME in

cases where it would be processed in a digester, which is good from a GHG perspective. The largest

energy-containing residue stream available from the mill site is the EFB. It could replace MF and PKS

in cases where technically suitable as fuel. An even larger energy content is left in the field in the

form of fronds and trunks, and this represents 1.07 PJ/yr (three times as much as the unused calorific

content at the mill site). The fronds, however, represent an important nutrient source for the

plantation. When comparing the nitrogen, phosphorous and potassium (N,P,K) fertiliser flows of the

various streams (see Chapter 3), it can be clearly seen that the fronds are an important source of

the N and K being returned to the soil by leaving the fronds on the plantation site. The main focus

for residue use, next to the POME, would therefore be on the EFB. However, EFBs’ thermal

utilisation is hindered by their high salt content, requiring the introduction of pre-treatment

technology for its valorisation to commodity fuel or feedstock. This is still one of the main challenges

that prevents its current use to its full potential.

A number of concepts are described in which EFB pre-treatment and POME use are combined, and

solutions for future use are given. Washing in combination with Torrefaction and/or TORWASH® are

described. Additionally, TORWASH® integrates a hydrothermal pre-treatment for POME using this

stream as a washing agent and enables the enhancement of phosphorous concentration within the

final digestate. A washing step can also be used in combination with gasification so as to burn the

required 0.21 PJ as a gas and use the excess in other applications (e.g. mobility gas fuel). By lowering

the gasification temperature to below 700 °C, it will also be possible to recover a higher-quality soil

improver in the form of biochar, which that can potentially minimise the N-P-K losses to the soil,

minimising fertilisation costs and CO2 emissions from decay. The processes described above are not

laboratory-scale solutions but rather new concepts entering the market now or very soon.

Page 51 of 54

8. Recommendations

8.1 Technical Recommendations

To optimise value generation and decrease GHG emissions, the generation of additional knowledge

will enable the identification of the most promising cases through which to deploy the identified

alternative concepts.

Mapping the current logistics of the palm residues infrastructure in combination with the scale of

residue treatment installations will enable the identification of preferred locations for new

conversion installations. The economically viable scale calculation would then help determine the

necessary pre-treatment of the residue stream. Larger installations and longer distances for

transport would require a more advanced pre-treatment to secure quality over time, up to the

commodity fuel with stringent quality demands that would be suitable for export (to Korea, Japan

or Europe) or future bio-refinery/gasification plants for chemicals or advanced bio-fuels production

in Malaysia or elsewhere. A market analysis shall compare various opportunities to valorise that

biomass excess which cannot be used for (improved) fertilisation or energy recovery on-site. These

opportunities can include the production of solid fuel/feedstock pellets for export (e.g. to Europe or

Japan) and of gas fuel for local industrial/mobility use or for the direct production of chemicals in

Malaysia (e.g. aromatics). Furthermore, this analysis shall include in its scope the value of fibre and

shell products’ applications to optimise the valorisation of all streams and the selection of suitable

alternative concepts to the current practice.

8.2 Environmental Recommendations

For the recovery of methane from POME an incentive exists in the form of legislation. On the

mainland of Malaysia a FIT exists for delivering biogas to the grid. Just the production of biogas

through the anaerobic digestion of mills’ wastewater would reduce the country’s CO2 emissions by

12%. To speed up the number of digestion installations placed and the amount of methane

recovered and not emitted could be encouraged by subsidies on local bio-CNG for transport

(replacing fossil fuel in cars, trucks or buses) or the electrification of remote areas not connected to

the grid.

From optimised fertilisation schemes, excess CO2 from decaying organic matter could be prevented.

This requires more research on, for example, the use of trunks as organic fertiliser at the end of the

tree lifespan.

A system-level analysis (e.g. LCA) of GHG emissions due to biomass decaying, nutrients and energy

flow would create a basis for the environmental assessment of different alternative concepts.

8.3 Business Opportunities

The ambition of the Malaysian Government to bring the bio-residues now under-utilised to their full

potential creates an excellent opportunity. In this report the need for POME digestion in

combination with gas cleaning and energy generation and the pre-treatment possibilities to use EFB

as a high-quality (commodity) fuel are other potential business opportunities present to date.

Page 52 of 54

Page 53 of 54

9. List of References

1. AIM, National Biomass Strategy 2020: New Wealth Creation for Malaysia's Biomass Industry. 2013, Agensi Inovasi Malaysia.

2. Mielke, T., Global oil suplly, demand and price outlook with special emphasis on palm oil. 2017, ISTA Mielke GmbH.

3. GreenPalm Global Edible Oil / Fat Production. 2015.

4. Elbersen, W., K. Meesters, and R. Bakker, Valorization of palm oil (mill) residues. 2013, Wageningen UR, Food & Biobased Research

5. Brown, D. and A. Buis NASA Pinpoints Cause of Earth's Recent Record Carbon Dioxide Spike. 2017.

6. Madhiyanon, T., et al., Ash and deposit characteristics from oil-palm empty-fruit-bunch (EFB) firing with kaolin additive in a pilot-scale grate-fired combustor. Fuel processing technology, 2013. 115: p. 182-191.

7. Pels, J., P. Nanou, and M. Carbo, Co-production of fuel pellets, biogas and liquid fertilizer from food residues by means of hydrothermal treatment (TORWASH®), in International Bioenergy Conference and Exhibition. 2017: Shanghai, China.

8. Fryda, L. and R. Visser, Biochar for Soil Improvement: Evalution of Biochar from Gasification

and Slow Pyrolysis. Agriculture, 2015. 5.

9. Singh P., Sulaiman O. Hashim R. and Singh R.P. Using biomass residues from oil palm

industry as a raw material for pulp and paper industry: Potential benefits and threat to the

environment. In: Environment Development and Sustainability15(2):367-383 · April 2013.

10 Greenhouse gas reductions through enhanced use of residues in the life cycle of Malaysian

palm oil derived biodiesel. Hansen, Sune Balle; Olsen, Stig Irving; Ujang, Zaini Published in:

Bioresource Technology 2012, 104, 358-366. DOI: 10.1016/j.biortech.2011.10.069

11 Yield gaps in oil palm: A quantitative review of contributing factors, Lotte S. Woittieza,

Mark T. van Wijk, Maja Slingerland, Meine van Noordwijk, Ken E. Giller. European Journal

of Agronomy 83 (2017) , 57-77.

https://www.researchgate.net/journal/1387-585X_Environment_Development_and_Sustainability

ECN part of TNO

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The Netherlands

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