Life Cycle Assessments of Energy From Solid Waste (PDF)

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2.2.2 Open-loop recycling Open-loop recycling takes place when a product is recycled after its use into another product. This can be a problem since the system boundary between products 1 and 2 is not clear-cut. Open-loop recycling has been much discussed in the LCA literature e.g. Huppes and Schneider (1994), Finnveden and Huppes (1995), Lindfors et al. (1995), Udo de Haes and Wrisberg (1997), Ekvall (1999) and Ekvall and Finnveden (2000b). The problem can be solved in two ways: by allocating environmental interventions between the two products and study only one of them, or by expanding system boundaries and including both products within the system. If allocation is to be made, there are three parts of the system that should be allocated between the two products (Lindfors et al. 1995): 1) the recycling system 2) production of primary material used in both products 3) disposal of materials used in both products Many methods for the allocation have been suggested in the literature and used in case studies (Huppes and Schneider 1994, Lindfors et al. 1995, Ekvall 1999). There does not seem to be any procedure that proves that any specific method is the “correct” one. Instead arguments are usually based on what intuitively seems reasonable or fair. However, such arguments can lead to very different conclusions and different allocation procedures can lead to different results (Ekvall and Tillman 1997). In order to avoid the allocation problem, system boundaries can sometimes be expanded to include several functions within the system. An example is the comparison between landfilling and incineration of waste. The main function of landfilling is treatment of solid waste. (In addition landfill gas is sometimes collected and used, but this aspect is however neglected in this methodological discussion). Incineration with heat recovery also treats solid waste, but in addition produces heat or electricity, thus providing a second function (Figure 2.3a). Since the processes provide different functions, it is difficult to directly compare them. In the expanded system an alternative method of producing an equivalent amount of heat has been added to the landfill system (Figure 2.3.b). It is thus possible to compare the incineration system to the combined landfill and heat producing systems. The systems compared are multifunctional systems. Another way of presenting the expanded systems is to subtract the heatproducing system from the incineration system using an alternative heat-source, as described in Figure 2.3.c. Since the same components are included, it is essentially the same systems which are presented in Figure 2.3.b and 2.3.c. In the system shown in Figure 2.3.c, so called “avoided emissions” will occur and environmental interventions may become negative. When using system expansion, several functions are studied at the same time. This is not always apparent since the subtracted systems appear as single-functional. When using system expansion it is no longer possible to study one function in isolation. This can be seen as an advantage since this reflects the real situation. In a situation where different functions cannot be chosen independently, it is an advantage if this is reflected in the LCA. For example, if a choice is made to incinerate solid waste with heat recovery, it is no longer possible to choose another energy source and this is illustrated in the expanded system. Also, from another perspective, if solid waste is chosen as the energy source, it is no longer possible to choose another treatment method for solid waste. This illustrates that if solid waste is considered as 18
an energy source, the energy system and waste management system must be considered simultaneously. This also implies that the systems will be identical whether the starting point is the choice of energy source, or the choice of waste treatment. Incineration Landfilling Functions: Treatment of solid waste Heat Function: Treatment of solid waste a. Incineration Landfilling + Alternative heat source Functions: Treatment of solid waste Heat Functions: Treatment of solid waste Heat b. Incineration - Alternative heat source Landfilling Functions: Treatment of Heat Heat solid waste Function: Treatment of solid waste c. Figure 2.3.a. An example of an allocation problem. b. A possible way of avoiding the allocation problem by expanding the system boundary. c. An alternative way of presenting the expanded system boundary described in figure b. (Finnveden and Ekvall 1998) The use of expanded system boundaries to avoid the allocation problem is often recommended, for example in the Nordic Guidelines (Lindfors et al. 1995), and the ISOstandard (ISO 1998). The ISO-standard has been critically reviewed, but system expansion is still generally recommended for change-oriented studies, e.g. Tillman (1999) and Ekvall and Finnveden (2000b). There are however some critical questions to consider when using system expansion (Ekvall and Tillman 1997, Ekvall and Finnveden 2000b). For example: 1) What material will the recycled material replace? It is often assumed that the recycled material will replace virgin material of the same kind. For example, recycled paper is 19
Page 1: Life Cycle Assessments of Energy fr
Page 4 and 5: ISBN 91-7056-103-6 ISSN 1404-6520,
Page 6 and 7: Ekvall, T. and Finnveden, G. (2000)
Page 9 and 10: Summary We live in a changing world
Page 11: fractions are included. In Figures.
Page 14 and 15: Contents PREFACE ABSTRACT SUMMARY C
Page 16 and 17: Nutrients content in digestion resi
Page 18 and 19: 7.6.6 Summary 125 7.7 RESULTS SCENA
Page 20 and 21: USES VOC YLD YLL Uniform system for
Page 22 and 23: discussed. Another question is wher
Page 24 and 25: 2 Methodology 2.1 General LCA metho
Page 26 and 27: geographical coverage, and consiste
Page 28 and 29: Weighting is and has always been a
Page 32 and 33: often assumed to replace virgin pap
Page 34 and 35: the differentiation between biotic
Page 36 and 37: composting of the food waste. Sourc
Page 38 and 39: 2.3.7 Landfills as a carbon sink In
Page 40 and 41: et al (1998) (recycling of PET), He
Page 42 and 43: 3 Scenarios and major assumptions 3
Page 44 and 45: of the incinerator capacity. If, ho
Page 46 and 47: Finally, in the long transport scen
Page 48 and 49: Table 3.4 Vehicles and distances wi
Page 50 and 51: 3.9.2 Medium transports scenario Th
Page 52 and 53: 4 Household waste composition 4.1 I
Page 54 and 55: Table 4.4 Composition of the fracti
Page 56 and 57: defined composition of newspaper. T
Page 58 and 59: 5. Processes 5.1 Introduction The w
Page 60 and 61: WASTE PAPER ADDITIVES EL. TRANSPORT
Page 62 and 63: Combining testliner and wellenstoff
Page 64 and 65: The first step in the recycling pro
Page 66 and 67: involves PET-resin production from
Page 68 and 69: PE as described in section 5.2. Thi
Page 70 and 71: The original inventory data for ana
Page 72 and 73: 5.3.3 Avoided production of fertili
Page 74 and 75: FOOD WASTE TRANSPORT ENERGY INCL EL
Page 76 and 77: The heat released in the kiln is ca
Page 78 and 79: Aluminium, CaCO 3 , clay, crude oil
Page 80 and 81:
Emissions formed during landfill fi
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energy used for purification is ass
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5.7.2 Exceptions Marginal electrici
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Combustion of biomass is not consid
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6.2.5 Stratospheric ozone depletion
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Table 6.2 Some emissions lacking a
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Table 6.4 Some emissions lacking a
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Non-treated waste All waste that ha
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Table 6.6 continued… Impact categ
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6.4.4 Additions For some substances
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categories for the substances found
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For PET most energy is saved in the
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Table 7.2 The table shows weighted
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The results for the food waste frac
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for both alternatives. Most of this
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7.2.13 Undefined substances As disc
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Table 7.4 The results for all impac
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7.3.1 Energy, abiotic resources and
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7.3.3 Toxicological effects Medium
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7.3.5 Summary A final summary of th
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7.4.2 Non-toxicological impacts For
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7.4.4 Total weighted results Change
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Table 7.16 Comparison between a sce
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The categories acidification (excl
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7.5.4 Total weighted results When u
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7.5.5 Summary A final summary of th
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Table 7.22 Weighted results for the
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A similar pattern results for SO x
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Table 7.25 Weighted results for hum
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Table 7.27 The ranking of the waste
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Table 7.29 Weighted results for the
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Table 7.31 Weighted results for hum
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7.8.2 Non-toxicological impacts The
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Opposite to the USESmin results, no
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More alterations in ranking occur i
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Table 7.39 Weighted global warming
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7.10 Results Scenario Plastic Palis
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Table 7.43 The ranking of the waste
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In category human toxicology there
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7.12 Results Qualitative discussion
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Table 7.49 The 100 year perspective
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Table 7.50 Continued Different time
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(MJ/ton) 0.0E+00 -1.0E+04 -2.0E+04
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materials in the base scenario (sec
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In general anaerobic digestion is p
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8.4 Limitations and need for furthe
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separation of fractions to be incin
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CEPI and BIR (1999). European List
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Finnveden, G., and T. Ekvall (1998)
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Johansson, S. (1998). Förstudie av
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Tukker, A. (1999a). Life Cycle Asse
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Additives Active pesticide Record:
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HCl (100%) B250 - (Hydrochloric aci
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NaClO 3 - (Sodiumchlorate) Record:
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Inputs from technosphere: Potato S
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natural gas, coal, water, silver an
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Energy - heat Heat diesel B250 Reco
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MJth gas energy Record: IVAM Refere
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of the coal and efficiency losses.
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MJel oil NL Record: IVAM References
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Gaslinetransport NL Record: IVAM Re
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Other Wastew. Treatment industry Re
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Chauvel & Lefebvre (1989) Chauvel &
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LCA-landbouw LCA-landbouw Database
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Remmerswaal (1996) J.Remmerswaal, F
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VNC Vereniging Nederlandse Cementin
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