An analysis of factorsinfluencing waste minimisationand use of recycled materials

for the construction ofresidential buildings

Graham J. TreloarSchool of Architecture and Building, Deakin University, Geelong,

Victoria, AustraliaHani Gupta

School of Engineering and Technology, Deakin University, Geelong,Victoria, AustraliaPeter E.D. Love

School of Architecture and Building, Deakin University, Geelong,Victoria, AustraliaBinh Nguyen

School of Engineering and Technology, Deakin University, Geelong,Victoria, Australia

Keywords Construction industry, Waste, Recycling, Costs, Energy, Australia

Abstract Residential building construction activities, whether it is new build, repair or maintenance,consumes a large amount of natural resources. This has a negative impact on the environment in theform depleting natural resources, increasing waste production and pollution. Previous research hasidentified the benefits of preventing or reducing material waste, mainly in terms of the limitedavailable space for waste disposal, and escalating costs associated with landfills, waste managementand disposal and their impact on a building company’s profitability. There has however been littledevelopment internationally of innovative waste management strategies aimed at reducing theresource requirement of the construction process. The authors contend that embodied energy is auseful indicator of resource value. Using data provided by a regional high-volume residential builder inthe State of Victoria, Australia, this paper identifies the various types of waste that are generatedfrom the construction of a typical standard house. It was found that in this particular case, wastedamounts of materials were less than those found previously by others for cases in capital cities (5-10per cent), suggesting that waste minimisation strategies are successfully being implemented. Cost andembodied energy savings from using materials with recycled content are potentially more beneficial interms of embodied energy and resource depletion than waste minimisation strategies.

IntroductionThe residential building industry relies heavily on natural resources. None ofthe conventional raw materials used in the construction of houses are availablewithout causing some degree of environmental impact. Many materials are

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Management of EnvironmentalQuality: An International JournalVol. 14 No. 1, 2003pp. 134-145q MCB UP Limited1477-7835DOI 10.1108/14777830310460432

processed from low-grade ores, such as copper. Manufacturing may haveundesirable side effects such as emission of pollutants into the atmosphere andwaterways. In addition, embodied energy (i.e. the energy consumed duringextraction, processing, manufacturing, and transportation at all stages,Boustead and Hancock, 1979) is used in the manufacture of materials. There arealso other environmental impacts, such as natural habitat destruction.Unfortunately, there is no universally applicable set of criteria available forselecting environmental friendly building materials (Cole, 1998).

A number of researchers have highlighted the potential benefits inpreventing or reducing demolition and construction waste (e.g. Graham andSmithers, 1996; Faniran and Caban, 1998; Thormark, 2000). By appreciating theprinciples of handling and using materials on site, attitudes to prevent wastecan be developed and the construction process can be managed more efficiently(Skoyles and Skoyles, 1985).

Embodied energy and natural resources are conserved when energyintensive materials are used efficiently (Lawson, 1996). Embodied energy maythus be a useful indicator of resource value. Some studies have focussed on therecycling potential of construction waste and demolition materials, valuingwaste in terms of embodied energy (Thormark, 2000). Few studies, however,have compared waste minimisation and recycling strategies in embodiedenergy and cost terms.

Using data provided by a regional high-volume residential builder in theState of Victoria, Australia, this paper identifies the various types of wastegenerated during the construction of a typical house. This paper aims toexplore the relationships between the cost and embodied energy savings fromwaste minimisation and recycling strategies using a case study.

BackgroundMuch of the waste stream going to landfill consists of solid waste from theconstruction and demolition of buildings. Waste minimisation strategies havebeen popular for some time in the construction industry. This paper considersthe effect of these strategies on one case study. Sourcing materials withrecycled content in terms of embodied energy and cost is suggested as the nextphase of environmental management in construction.

Many studies measure waste from construction sites on the basis of eithervolume or mass, to gauge the effect on disposal costs (Johnston and Minks,1995; Graham and Smithers, 1996; Faniran and Caban, 1998). This does notgive the best appreciation of the problem in terms of the environment. Thesavings from using materials with recycled content can be best measured interms of the environment by considering their embodied energy (Thormark,2000). Embodied energy represents 10-40 times the annual operational energyof most Australian residential buildings, depending upon building design,climate construction systems, equipment type, fuel sources and building usage

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patterns. Each year in Australia, the embodied energy used in construction isapproximately equal to the annual operational energy of the built stock, andtogether they make up 30-40 per cent of national energy use and greenhousegas emissions.

There are several problems with existing embodied energy analysismethods, which include process analysis, input-output analysis and hybridanalysis. Process analysis, while accurate for particular processes, oftenignores a large number of small to medium processes. Input-output analysis,despite its many inherent errors, is used because of its unique property ofsystemic completeness. Errors for process analysis data are approximately^10 per cent (Boustead and Hancock, 1979), and for input-output data errorsare approximately ^50 per cent (Miller and Blair, 1985). Hybrid analysismethods attempt to reduce the errors inherent in each of the two previousmethods. There are two types: one based on the process analysis frameworkand the other based on the input-output framework. For the hybrid analysismethods, errors vary between these rates, depending upon the mix of processand input-output data.

Input-output analysisAn input-output table maps the flows of goods and services betweenvarious sectors of an economy. A direct input-output table of technicalcoefficients gives the amounts of goods and services required directly byeach sector. Input-output tables are most commonly available in economicunits. Direct energy intensities are typically calculated by summing theproducts of the direct input-output coefficients describing sales by energysupply sectors, national average energy tariffs and primary energy factors.Indirect energy requirements for the manufacture of goods and services canbe traced manually through the direct input-output matrix. For example,the energy required directly to make concrete can be multiplied by thedirect requirement for concrete by residential building. This embodiedenergy path can be said to be one stage upstream from residentialbuilding. The set of “first flows” is relatively easily extracted from thedirect input-output matrix (Patten and Higashi, 1995). Disaggregation offurther inputs upstream from stage 1 is possible, but tedious, because oftheir increasing complexity. More conveniently, the Leontief inverse matrix,ðI2AÞ21, gives direct plus indirect requirements lumped together as onenumber – the “total requirement” (Leontief, 1966). The system boundary iseffectively infinite.

Potential errors inherent to input-output analysis result from theproportionality and homogeneity assumptions (Miller and Blair, 1985). Theproportionality assumption means that inputs to a sector are assumed to belinearly proportional to its output. The homogeneity assumption means thatsector outputs are assumed to be proportional to price, regardless of the

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variation in each different product of the sector. Additional errors relate to theuse of national average tariffs to translate economic flows into physical flowsin the form of energy (Peet and Baines, 1986).

Process analysisProcess analysis is defined broadly here as embodied energy analysis usingany other source of data than input-output tables. Process analysis is generallymore accurate than input-output analysis. The first step in a process analysis isthe measurement of all direct energy requirements of the main process, and theoutput of the process, over a reasonable period of time. The second step is theidentification of inputs of other products required by the process over the sameperiod. The third step is the determination of the energy embodied in eachproduct required by the main process (Boustead and Hancock, 1979). Processanalyses rarely extend further than a few stages upstream and tend to ignoreinputs at each stage (Lave et al., 1995). Process analyses can be very accuratefor the precise system to which they relate, but sufficiently detailed systems arerarely reported in the literature. The key to both this method’s success and itsfailure is its focus on detail, giving accuracy but at the same time limitingsystem boundary completeness.

Hybrid analysisHybrid analysis has been defined as the combination of process and input-output data. There are two generic types: “process-based hybrid analysis” and“input-output-based hybrid analysis”. Process-based hybrid analysis is themost common hybrid analysis method, and involves the application of input-output derived total energy intensities to a materials “inventory” collectedusing process analysis. The system boundary of a process-based hybridanalysis has similar limitations to a process analysis, except that the systemboundaries for basic material inputs are complete due to the application ofinput-output derived total energy intensities (Bullard et al., 1978). Where thedirect energy intensity of a material is relatively small, the material inventoryis occasionally extended a further stage upstream. It is uncommon for thispractice to be comprehensive, and the selection of materials to disaggregatetends to be intuitive (Lave et al., 1995). As with process analysis, inputs ofservices and processes involving the assembly of basic materials into complexproducts are typically neglected.

Input-output-based hybrid analysis, an innovative technique proposed byTreloar (1997), and demonstrated in Treloar et al. (2001), requires firstly thatthe input-output model to be disaggregated into mutually exclusive “energypaths”. For example, one energy path is required directly to make cement usedin concrete, which is further used in construction. This does not include theindirect energy embodied in the cement or the other concrete components andprocesses – these are separate energy paths. Process analysis data is thenderived for energy paths, prioritised on the basis of their relative embodied

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energy value. The input-output energy path can then be deducted from theinput-output model and the process analysis version substituted withoutdisturbing the upstream processes, and without truncating the systemboundary of the original input-output model. If upstream or other processes areimportant, process analysis data for them should also be derived. This methodapproaches the problem of deciding which process analysis data to collect froman informed basis.

Material waste in the construction industryThe completeness and reliability of embodied energy analysis methods iscrucial to the validity of the application of embodied energy data to scenariossuch as waste minimisation. This also applies to the assessment of the directand indirect costs associated with recycling and disposal strategies. Theselection of one strategy over another could be determined by small variationsin the embodied energy and cost values.

Figure 1 shows the waste streams for construction and demolitionprocesses. The winning of raw materials is depicted on the left of thediagram. The “manufacturing” stage refers to transformation of basicmaterials into building materials and products, along with initial processingstages (for example, metallic ore refining). There may be several transactionsbetween industries at this stage. The “construction” stage refers to theassembly of materials and products to form the finished building. In the“building use” stage, construction services may be used in facilitiesmanagement for maintenance and refurbishment of existing buildings. The“demolition” stage refers to the final and total disassembly of the building.The horizontal arrows depict the flow of materials with or without recycledcontent. The curved arrows represent re-use or recycling processes, undertwo categories:

Figure 1.Flows of materials,products and wastes forconstruction anddemolition activities,including closed andopen-loop recycling

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(1) closed loop recycling (i.e. within that industry or building life stages);and

(2) open-loop recycling (i.e. between industries or building life stages).

The use of recycled materials at any stage displaces requirements for newmaterials, and may save considerable cost, natural resources and embodiedenergy. The presence of a saving in each case depends on the reclamation andrecycling processes not requiring more financial, natural or energy resourcesthan are saved through the recycling effort, which is not necessarily always thecase (Boustead, 1996). It also requires that the reclamation costs be compared tothe costs in financial, resource and embodied energy terms for providing acomparative product. In many cases, the recycled of a material may represent aserious downgrading of use, therefore recycling processes including transportand ancillary processes need to be efficient to ensure actual savings areproduced. Accounting of financial and resource requirements are relativelystraight forward compared to the embodied energy issue, as discussed above.

Research methodologyA standard house plan was used to demonstrate the financial andenvironmental benefits of minimising waste and use of recycled materials incomparison to their new counterparts. A list of materials quantities wasderived from a set of drawings that was obtained from the building company.The materials were categorised into basic groups (for example, timberproducts) instead of the usual categorisation in elements (for example, flooring).Wastage rates were determined in consultation with the construction companyemployees. Costs for the materials were sourced and embodied energy valueswere determined in Australian dollars. The study was undertaken in 1999.Costs for Victoria are comparable in other parts of Australia.

Material cost information was obtained from Cordell Pricing Guide (1999),excluding installation and labour. Embodied energy data were derived usingthe input-output-based hybrid analysis methods outlined in Treloar (1997).Australian input-output data from 1992-1993 and process analysis data derivedin Australia industries from the mid-1990s were merged. All the embodiedenergy data converted to primary energy terms, meaning that the quantities ofdelivered fuels such as electricity had been converted to the quantities ofprimary fuels such as coal used for their manufacture and provision to theconsumer. Table I lists the material costs and embodied energy rates used forcommon building materials.

The wastage rates were applied to the material costs to find out the financialvalue of the wasted materials. The wastage rates normally allowed for in thecontingency plan of common building materials given by the firms surveyedare given in Table II.

The cost of the wasted materials was determined using equation (1). Theembodied energy of the wasted materials was determined using equation (2).

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Both equations without the wastage rates give the total quantities of materialsrequired (i.e. the total quantities of material required equalled the installedquantities plus the wasted quantities):

TOTALWS= ¼XE

e¼1

XM

m¼1

½Qem £Wem £ Pm�; ð1Þ

where:

Material Unit Embodied energy rate (GJ/unit) Costs ($/unit)

10mm plasterboard m2 0.06 46mm glass m2 0.31 171Acrylic paint m2 0.02 2Aluminium foil m2 0.13 1.4Bricks m2 0.88 31Carpet m2 1.00 64Ceramic tiles m2 0.34 50Copper t 135.39 4212Electrical products $ 0.01 variousFC 4.5mm m2 0.18 7Insulation R2.5 m2 0.16 9Laminate m3 151.73 20,000Medium density fibreboard (MDF) m3 16.00 2,000Membrane m2 0.08 2Metal products $ 0.01 variousReady-mixed concrete 30MPa m3 3.87 88Roof tiles m2 1.36 34Sand m3 0.33 2Steel decking m2 0.37 31Timber hardwood m3 1.95 1,275Timber softwood m3 3.41 1,439Vinyl 3mm m2 0.26 33

Sources: As defined in the “Method” section

Table I.Material costs andembodied energyrates used forcommon buildingmaterials

Materials Typical wastage rate (%)

Cement/concrete 5Masonry/clay 5Glass 3Metals 10Paint 5Plaster 10Plastics 10Timber 10Services (equipment only) 0

Sources: As defined in the “Method” section

Table II.Wastage rates usedfor commonbuilding materials

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TOTALW$ = the total cost of wasted materials;.

Qem = the quantity of material, m, in element, e;.

Wem = the wastage rate (per cent) for material,m, used in element, e;and

Pm = the cost of material, m.

TOTALWEE ¼XE

e¼1

XM

m¼1

½Qem £Wem £ EEm�; ð2Þ

where:

TOTALWEE= the total embodied energy (EE) of wasted materials;

Qem = the quantity of material, m, in element, e;

Wem = the wastage rate (per cent) for material,m, used in element, e;and

EEm = the embodied energy of material, m, including raw materialextraction, transportation, manufacturing, etc., butexcluding installation.

To model wasted fractions in terms of the total cost and embodied energy forthe house, a total had to be derived which was based on more than simply thesum of the materials quantities as taken off the drawings. Estimates for theprocesses not covered by the list of materials quantities were used to completethe system boundary as follows:

. $440/m2 for the small materials, labour, installation, services andbuilder’s overheads (an estimate, based on previous experience); and

. 3.93GJ/m2 for the embodied energy of ignored processes (based on datafrom Treloar et al., 2001, for a similar type and class of building).

Table III lists the material costs and embodied energy rates used for secondhand building materials or materials with recycled content, as the situationallowed. Certain materials and situations did not allow consideration ofrecycled materials, and these items remained as per the above method.

ResultsThe financial results showed that the cost of extra material ordered to cover thewastage was 3.9 per cent of total cost for the house (Table IV). Most of thewasted cost was in the wall, roof and floor elements, respectively. This resultwas unexpectedly small, considering previous studies (for example, Faniranand Caban, 1998; Graham and Smithers, 1996; Johnston and Minks, 1995). This

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suggests that waste minimisation strategies that have been promoted in theindustry for some time are having a positive effect.

The embodied energy analysis showed that the energy embodied in theextra materials ordered to cover wastage was 4.6 per cent of the total embodiedenergy of the house (Table V). The order of important elements changed

Material Unit Embodied energy rate (GJ/unit) Costs ($/unit)

10mm plasterboard m2 0.01 3.766mm glass m2 0.06 2.00Aluminium foil m2 0.13 1.44Bricks m2 0.09 20.00Carpet m2 0.10 5.00Electrical products $ 95 per cent saving typically 5-90 per cent savingsFC 4.5mm m2 0.04 2.00Medium density fibreboard (MDF) m3 4.80 1,000.00Roof tiles m2 0.27 10.00Steel decking m2 0.07 8.01Timber hardwood m3 0.39 0.02Timber softwood m3 0.68 0.02Vinyl 3mm m2 0.10 33.27

Sources: As defined in the “Method” section

Table III.Material costs andembodied energyrates used forsecond-handbuilding materialsand materials withrecycled content

Used materials ($/m2) Wasted materials ($/m2)

Floor 83.27 9.25Roof 140.13 11.32Walls 143.66 12.64Fitments 17.41 1.27Services 78.83 1.76Other costs 437.32 0.00Total 900.61 (96.1%) 36.24 (3.9%)

Note: Columns may not sum due to rounding

Table IV.Cost breakdown byelement

Used materials (GJ/m2) Wasted materials (GJ/m2)

Floor 2.07 0.23Roof 2.98 0.19Walls 1.89 0.12Fitments 0.12 0.01Services 1.11 0.04Other goods and services 3.93 0.00Total 12.11 (95.4%) 0.59 (4.6%)

Note: Columns may not sum due to rounding

Table V.Embodied energybreakdown byelement

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somewhat from the financial analysis, but the results were otherwise similar inmagnitude. Most of the wasted embodied energy was in the floor, roof and wallelements, respectively. This change in order suggests that a change in priorityfor waste minimisation strategies should be considered, so that time is devotedto reducing waste for materials with high embodied energy, rather than thosethat simply cost more (as suggested by Thormark, 2000).

For the embodied energy analysis, the proportion of process analysis datarelative to input-output data was 63 per cent. This is consistent with previousapplications of the input-output-based hybrid analysis method (Treloar et al.,2001). This value is low because most of the process analysis data availablefrom industry is for processes thought to be the most important based on theprevious process-based hybrid analysis paradigm. Process analysis data fornon-traditional engineering and manufacturing processes thus needs to bederived.

Figure 2 shows that the results for the scenario where materials withrecycled content were use in the initial construction of the building showedmore potential than the results for the wasted quantities given in Table IV andTable V. The potential savings from the use of materials with recycled contentwere 40 per cent in terms of cost and 70 per cent in terms of embodied energy.In Figure 2, it is also show that the embodied energy savings were relativelylarger than the cost savings for the elements: services, walls, roof and to alesser extent floors. The embodied energy savings for the fitments element waspossibly closer to the cost savings because these items do not last as long andconsequently second hand items are less likely to be viable.

Discussion and conclusionThe research found that the wasted quantities of materials represented onlyapproximately 4 per cent of both the price of, and energy embodied in, thebuilding. This suggested that waste minimisation strategies are having apositive effect. It also suggests that the potential for recycling construction

Figure 2.Comparison of embodiedenergy and cost savings

from using materialswith recycled content at

the initialconstruction stage

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waste may be reducing, as further efficiencies are gained. There is now agreater emphasis being placed upon the building industry to be environmentalfriendly. The industry must consider the positive aspects of a wastemanagement plan and give it the same importance as other management plans.However, the authors argue that a comprehensive waste and recyclingminimisation plan should be inclusive of all phases of the building life cycle,and be in the context of the entire economy, considering closed and open-looprecycling potential.

Waste management strategies have been suggested to reduce the waste atthe addressed sources. One of the steps of reducing waste is through the reuseof second-hand materials and throughout the use of materials with recycledcontent. Based on actual costs of second-hand materials and estimates of theembodied energy savings, it was found that the cost savings could total 40 percent of the building price, while the embodied energy savings could be as highas 70 per cent of the total embodied energy of the building. In countries withcheaper labour, the savings could be even greater.

Other strategies worthy of consideration include sourcing of materials whichare optimal in total life cycle terms for the building, in terms of initial embodiedenergy, long life, thermal performance, lowmaintenance and other performanceissues. At the whole building level, building maintenance seems to be the bestway to ensure that the total environmental impact of the built environment isminimised. Thoughtful renovation, when eventually required, can improveperformance using low environmental impact materials which may haverecycled content from other industries. The retained materials can beconsidered to be recycled in situ.

Other potentially beneficial strategies include communicating tomanufacturing industries that resource consumption, including embodiedenergy, needs to be lowered. Waste minimisation in processes upstream fromconstruction needs to be modelled. As embodied energy of upstream processesis more significant than energy used in the construction process itself, it can bededuced that waste in upstream processes may also be more significant thanthat directly resulting from the construction process.

References

Boustead, I. (1996), “LCA: an overview – the evolution of life-cycle assessment”, Proceedings ofthe 1st National Conference on Life-Cycle Assessment, Melbourne, February 29-March 1,p. 29.

Boustead, I. and Hancock, G.F. (1979), Handbook of Industrial Energy Analysis, Ellis HorwoodLimited, Chichester.

Bullard, C.W., Penner, P.S. and Pilati, D.A. (1978), “Net energy analysis: handbook for combiningprocess and input-output analysis”, Resources and Energy, Vol. 1, pp. 267-313.

Cole, R. (1998), “Emerging trends in building environmental assessment methods”, BuildingResearch and Information, Vol. 26, pp. 3-16.

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Cordell Pricing Guide (1999), Cordell Building Cost Guide: Residential, Cordell BuildingPublications, Melbourne.

Faniran, O.O. and Caban, G. (1998), “Minimising waste on construction project sites”,Engineering, Construction and Architectural Management, Vol. 5 No. 2, pp. 182-8.

Graham, P. and Smithers, G. (1996), “Construction waste minimisation for Australian residentialdevelopment”, Asia Pacific Journal of Building & Construction Management, Vol. 2 No. 1,pp. 14-19.

Johnston, H. and Minks, W.R. (1995), “Cost effective waste minimisation for constructionmanager”, Cost Engineering, Vol. 37 No. 1, pp. 31-9.

Lave, L.B., Cobas-Flores, E., Hendrickson, C.T. and McMichael, F. (1995), “Life-cycle assessment:using input-output analysis to estimate economy-wide discharges”, Environmental Scienceand Technology, Vol. 29 No. 9, pp. 420A-6A.

Lawson, W.R. (1996), Building Materials, Energy and the Environment: Towards EcologicallySustainable Development, The Royal Australian Institute of Architects, Red Hill.

Leontief, W. (1966), Input-Output Economics, Oxford University Press, New York, NY.

Miller, R.E. and Blair, P.D. (1985), Input-Output Analysis: Foundations and Extensions,Prentice-Hall, Englewood Cliffs, NJ.

Patten, B.C. and Higashi, M. (1995), “First passage flows in ecological networks: measurement byinput-output flow analysis”, Ecological Modelling, Vol. 79, pp. 67-74.

Peet, N.J. and Baines, J.T. (1986), Energy Analysis: A Review of Theory and Applications,New Zealand Energy Research and Development Committee, Auckland, Report No. 126, p. 56.

Skoyles, E.R. and Skoyles, J.R. (1985), Waste Prevention on Site, Mitchell’s Professional Library,London.

Thormark, C. (2000), “Including recycling potential in energy use into the life cycle of buildings”,Building Research and Information, Vol. 28 No. 3, pp. 176-83.

Treloar, G.J. (1997), “Extracting embodied energy paths from input-output tables: towards aninput-output-based hybrid energy analysis method”, Economic Systems Research, Vol. 9No. 4, pp. 375-91.

Treloar, G.J., Love, P.E.D. and Holt, G. (2001), “Using national input-output data for embodiedenergy analysis of individual residential buildings”, Construction, Management andEconomics, Vol. 19, pp. 49-61.

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