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The Application of Life Cycle Assessment to Integrated Solid Waste Management
0957±5820/00/$10.00+0.00 q Institution of Chemical Engineers Trans IChemE, Vol 78, Part B, July 2000
THE APPLICATION OF LIFE CYCLE ASSESSMENT TO INTEGRATED SOLID WASTE MANAGEMENT Part 2ÐPerspectives on Energy and Material Recovery from Paper T. EKVALL1 and G. FINNVEDEN2 1 Chalmers Industriteknik, GoÈteborg, Sweden Environmental Strategies Research Group (fms), Swedish Defence Research Establishment (FOA), Stockholm, Sweden
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he environmental aspects of different waste management options for paper materials are the subject of an ongoing debate. A large number of life cycle assessments have been performed in order to study the topic. The comparison between recycling and incineration with energy recovery is often in focus. Different studies have arrived at different conclusions due to differences in the methods applied and assumptions made in the life cycle inventory analysis (LCI). Key factors for the LCI results include what energy is replaced by incinerated waste paper, what material is replaced by recycled ®bres, how the pulpwood savings are used, what external energy carrier is used for the recycling process, and what environmental burdens are associated with a change in the electricity demand. These factors can be investigated for different decision contexts and from different ethical, time and geographical perspectives. Different choices are appropriate for different decisions and perspectives. Hence, to obtain an adequate conclusion, the comparison needs to be speci®ed in terms of what perspectives are relevant. Keywords: life cycle assessment; waste management; recycling; incineration; paper.
INTRODUCTION
makes it possible to carry through a comprehensive evaluation of the environmental burdens and gains of the different options. However, different LCAs have arrived at different conclusions regarding which option is the best. This is, to a large extent, due to differences in the methods used for inventory analysis (LCI)24. Key issues in the LCI methodology have been identi®ed through comparisons of different studiese.g., 24±27. Important methodological issues include the de®nition of system boundaries, allocation, assumptions and choice of data. This paper presents an overview of the issues that are important for the results of the comparison between recycling and incineration with energy recovery. It also includes a discussion on what methodological choices or assumptions are appropriate for different purposes and contexts. At the end of the paper, there is a discussion on how these perspectives affect the conclusions concerning the environmental comparison between recycling and incineration with energy recovery. Direct land®ll of wastepaper and incineration without energy recovery are not dealt with in this paper, which is an elaboration on previous studiese.g., 25±28.
Environmental Life Cycle Assessment (LCA) is a study of the environmental aspects and potential impacts throughout a `product’s’ life from raw material acquisition through production and use to disposal (i.e., from cradle-to-grave)1. The term `product’ includes not only physical products but also services1, such as waste management. Essentially the same methodology, developed for product systems, can be used when LCA is applied to waste management systems, although different aspects of the methodology may come into focus2. The LCA methodology is currently being used in several countries to evaluate different strategies for integrated solid waste management as well as treatment options for speci®c waste fractionse.g., 3±6. The framework of LCA methodology and its application to solid waste management is described in Part 17. The environmental aspects of different waste management options for paper materials are the subject of an ongoing debate. A large number of LCAs have been performede.g., 8±23, and reviewed, in order to study the topic. The comparison between recycling and incineration with energy recovery is often in focus. This comparison is interesting because both waste management options may result in an environmental gain. Material recycling can reduce the environmental burdens associated with primary material production. Energy recovery can reduce the environmental burdens associated with alternative energy production. The broad, systemic approach of LCA potentially
CONSISTENT RESULTS In a previous literature survey several LCAs were compared, addressing the environmental aspects of recycling and incineration with energy recovery of paper packaging materials 25. The survey included European studies ful®lling 288
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 certain basic criteria, mainly concerning transparency and methodology. It included seven publications, with altogether 12 cases and approximately 40 scenarios8±14. One of the aims of the analysis was to see whether the different studies gave the same results, and if not, to analyse the reasons for the different results. For some parameters, the same results are obtained in all studies, cases and scenarios. One consistent result concerns the overall energy use. It turns out that the total energy use is lower in the case of recycling compared to incineration with heat recovery provided that the energy content of the pulpwood is included in the balance. This is mainly because recycling of waste paper requires less energy compared to virgin pulp and paper production. Another consistent and related result is that the use of biomass (for paper and for energy) is lower in the case of recycling compared to incineration with heat recovery. Biomass is `saved’ and can be used for some other purpose in the technosphere. KEY METHODOLOGICAL ISSUES For many of the other parameters, it turns out that the conclusions depend on certain key factors, all related to the Avoided BurdensÐ i.e., the `environmental credits’ for material or energy recovery7. The factors that are important for the environmental comparison between energy recovery and material recycling are presented with the help of Figure 1: I The environmental gain of waste incineration with energy recovery depends on what energy is replaced by the energy from wastepaper. II The environmental gain of recycling depends on what material is replaced by the recycled ®bres. III When recycled ®bres replace virgin ®bres as raw material for pulp production, the pulpwood requirements for this pulp production are reduced. The environmental consequences depend on how the pulpwood savings are used. IV When recycled ®bres replace virgin ®bres as raw material for pulp production, the available amount of internal, renewable fuel (bark, liquor) is reduced. The demand for external fuel is likely to increase, particularly
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when primary, chemical pulp is replaced. The environmental consequences depend on what external fuel is used. V When pulp based on recycled ®bres replaces primary, mechanical pulp, the electricity demand is reduced. The environmental gain from this reduction depends on how this electricity is produced. Increased transportation is sometimes mentioned as a major environmental problem associated with increased recycling. The importance of transportation for the ®nal LCI results has been analysed in several studies8±11,18,20. The conclusion throughout these studies is that transportation has a limited in¯uence on the results. This conclusion is valid for the energy demand and for emissions of CO2, SO2 and NOX, under the assumption that the transportation is reasonably ef®cient. Transportation can be important for other types of environmental problems, such as noise, cancer and respiratory diseases. It should also be noted that transportation may increase as well as decrease as a result of increased recycling. This is because, while the transportation of waste paper and recycled ®bres increases, transportation of wood and virgin ®bres is reduced. POSSIBLE PERSPECTIVES The environmental comparison between energy and material recovery can be carried out from various different perspectives. First, the comparison can be made to support different decisions. For example, the decision-makers can be consumers choosing between putting the waste paper either in a dustbin with mixed waste that goes to incineration or in a bin for source separated paper that goes to recycling. Or, they can be policy makers choosing between either investing in waste incineration plants or pushing for increased recycling rates. A third, possible decision is the choice between investing in increased waste incineration or in other types of renewable energy production. In addition, other kinds of decisions can be supported by an environmental comparison between energy and material recovery. A second dimension is that the comparison can be based on different ethical views concerning what constitutes a good action. One possible perspective is that each action should be assessed based on the consequences of that
Figure 1. Simpli®ed illustration of the system that can be affected by the choice between recycling and incineration of used paper and board. The numbers refer to key factors that are discussed in the text.
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individual action29. From this perspective, the best choice is the choice that has the best environmental consequences30. An alternative perspective is that the best choice is the choice that contributes the least to environmentally poor systems. This is consistent with the ethical view that each action should be assessed based on whether or not it conforms to a good rule30. The rule, in turn, can be assessed based on the consequences of the rule or based on another principle31. Third, the alternatives can be compared in different time perspectives. Economists distinguish between short-term and long-term perspectives. In the short-term perspective, the production capacity of different systems is assumed to be constant but the utilization of the systems varies. In the long-term perspective, the production capacity of different systems can change. In addition to the two economic time perspectives, the alternatives can be compared in the context of a sustainable future scenario. Fourth, the decision can concern different locations. As stated in Part 1, the location of processes in the Background System Ðprocesses whose selection or mode of operation is not affected directly by decisions based on the studyÐ can in general not be de®ned7. But the location of the Foreground SystemsÐi.e., the waste management systems whose selection is affected directly by decisions based on the study7Ðis often known. For example, the Foreground waste incineration might be located in Sweden, the UK or in another country. ALTERNATIVE FUEL FROM DIFFERENT PERSPECTIVES The ®rst key factor that is mentioned above is the Avoided Burdens associated with the energy production that is replaced by wastepaper incineration with energy recovery. If the paper is recycled instead of incinerated with energy recovery, another fuel will in many cases be used for replacing the energy from the paper. The question is then: which is the competing fuel? A large part of the differences between different studies can be explained by this aspect of the surrounding system25. In spite of this, the question of which is the competing fuel has been investigated in a few case studies onlye.g., 10. In other cases, it has been subject to different assumptions. In a recent study, all incineration facilities in Sweden were included in a survey addressing the question: what fuel would replace paper packaging materials in your incinerator for the next ®ve years, if the paper is recycled instead of incinerated? The most common answer was: other types of solid waste that currently are being land®lled32. Although there are no studies con®rming this, it seems likely that this answer is typical for many other countries because, in most countries, the incineration capacity is much smaller than the total amount of combustible solid waste33. Thus, there are large amounts of solid waste that are currently being land®lled and that can replace the recycled paper in the incinerators. This can be important for the comparison, if the decision at hand concerns the consumer’s choice of putting the paper either into the bin for incineration or into the bin for recycling. It means that paper that is sent to the incineration plant in most countries is likely to replace other waste ¯ows in the waste incinerator, at least in the short-term. The waste
that is replaced by incinerated paper can be expected to end up at land®lls where it is eventually decomposed, which results in emissions of, e.g., methane34±35. This should, of course, be taken into account in the environmental comparison if the ethical starting point is that (environmentally) good actions are actions that have good (environmental) consequences. In a long-term perspective, the capacity for waste incineration will perhaps be expanded until no combustible waste is disposed to land®ll. In this situation, incinerated paper will not replace other waste ¯ows. Instead, the decision to put the waste paper into the incineration bin is likely to increase the total amount of energy that is recovered from combustible waste. This may result in an increased total consumption of electricity and heat, but the energy from the waste paper may also replace energy from other sources. In most countries, such an expansion would take many years. It is, therefore, dif®cult to know what the competing energy source would be in that situation. Electricity and heat are currently, in many countries, produced primarily from fossil fuel. Investments in new plants for production of electricity and heat also assume the use of fossil fuel, in many cases. This indicates that the energy source that competes with energy from waste incineration would often be fossil fuel. However, in many countries, efforts are made to increase the use of renewable energy as a response to, e.g., the threat of global climate change. In a sustainable future scenario, fossil fuel will probably not be used, at least not with current emissions; instead, the alternative energy source is likely to be renewable. Energy from waste incineration can therefore, in some cases, compete with renewable energy sources, particularly biomass in the form of energy crops and agricultural waste, which is an alternative fuel for combined heat-and-power plants. Another aspect, which may change the competing fuel, is the type of furnace that can be used for waste paper incineration. The studies addressing this question have normally assumed that the paper is combusted in incinerators for mixed municipal waste. However, pure waste paper fractions might on some occasions be combusted in a less advanced furnace for solid fuels, where combustion of other types of solid waste is not allowed. Such furnaces can be used for heating purposes36±37 or for the production of steam and electricity at paper mills. In this case, the waste paper may replace other types of fuel rather than other waste ¯ows. What fuel is replaced depends on whether the energy in the waste paper is recovered in the form of heat and/or electricity. It also depends on where in the world the waste incinerator is located. Finally, it depends on the time perspective of the comparison. As indicated above, the alternative fuel is, in many cases, fossil fuel in the economic short-term or longterm perspectives. In a sustainable future scenario, the alternative energy is likely to be renewable energy. The discussion above is based on the assumption that the decision at hand is the choice of putting the paper either into the bin for incineration or into the bin for recycling and that the ethical starting point is that good actions are actions that have good consequences. If the ethical starting point is that the best option is the one that contributes to the best systemsÐa signi®cantly different approach (see above)Ðit is necessary to evaluate the systems to which the consumer contributes when routing paper for recycling or for energy recovery. It is possible to regard the total waste incineration Trans IChemE, Vol 78, Part B, July 2000
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 in, e.g., a country as the system to which the consumer contributes. When evaluating this system, it is reasonable to account for the Avoided Burdens attributable to the energy recovered through waste incineration. Without this energy, the demand for other energy sources would probably be greater. In this sense, the energy from the total waste incineration replaces other energy sources. The environmental implications of this replacement depend on the competing energy source at that time and location. In the economic short-term or long-term perspectives, energy from the total waste incineration often competes with fossil fuel. In a sustainable future scenario, the alternative energy is likely to be renewable energy. Alternatively, the decision at hand may be the choice between investing in new capacity for waste incineration with energy recovery or pushing for increased recycling rates. This decision will affect the total amount of energy that is recovered from combustible waste. An increased energy ¯ow from the waste management sector may replace other energy sources. Again, the environmental implications of this replacement depend on the competing energy source at that time and location. If the decision at hand is the choice between investing in increased waste incineration capacity or in energy plants based on other types of renewable energy, this decision will also affect the total amount of energy that is recovered from combustible waste and, hence, the Avoided Burdens. However, in this case, the competing energy source is obviously the renewable energy that would be utilized in the alternative energy plant. ALTERNATIVE MATERIAL FROM DIFFERENT PERSPECTIVES In most LCAs, it is assumed that the recycled ®bres from the system investigated replace virgin ®bres. In fact, the recycled material may also replace recycled ®bres from other sources, completely different types of material or no material at all33. Paper that is collected for recycling enters an international market, where it competes with waste paper from, e.g., other countries38. Increased collection for recycling in one country may result in increased use of recycled ®bres, but it may also result in reduced collection in other countries. This can be important for the comparison, at least if the decision at hand is the choice between putting the paper into the bin for incineration or the bin for recycling. It means that paper that is sent to recycling in part replaces other waste paper ¯ows. The other waste paper ¯ows will then end up at land®lls or waste incinerators. In the latter case, they will push other waste ¯ows to the land®ll, as long as the situation continues in which waste incinerator capacity is smaller than the quantity of available, combustible waste. This reduces the environmental gain from the Foreground paper collection. If the ethical starting point is that the best option is the one with the best consequences, the environmental advantages of recycling are smaller compared to the case when the recycled ®bres from the system investigated replace virgin ®bres. If the recycled paper replaces other types of materials, such as plastics, wood or mineral wool, the Avoided Burdens will depend on the material replaced. If the recycled ®bres replace plastics made from virgin materials, Trans IChemE, Vol 78, Part B, July 2000
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recycling probably leads to reduced use of fossil fuels with their associated environmental problems. If the ethical starting point is that the best option is the one that contributes to the best systems, it can be argued that sending the paper to recycling contributes to the recycling system. This system is good, it can be argued, because it results in an environmental gain, partly originating from the reduction in pulpwood demand (or other natural resources) and partly from energy savings in the pulping processes (or other material production processes). However, it should be noted that sending the paper waste to recycling is not suf®cient to obtain this environmental gainÐit is also necessary to demand products based on recycled ®bres instead of products based on virgin material. Hence, it can be argued also from this ethical starting point that the environmental advantages of sending paper waste to recycling are smaller than most recent LCAs indicate. If the decision at hand is to implement a strategy that results in increased total recycling rates for paper, this strategy will, of course, result in the full environmental gain of increased recycling. From above it can be concluded, however, that the strategy might be ineffective if it only stimulates the collection of paper waste in a limited geographical area. ALTERNATIVE PULPWOOD USE FROM DIFFERENT PERSPECTIVES When recycled ®bres replace virgin ®bres as raw material for pulp production, the pulpwood requirements for this pulp production are reduced. The type and magnitude of the environmental consequences depend on the alternative use of the pulpwood that is saved through recycling. In the short term, this pulpwood might be used for production of other pulp and paper products. These products might, in part, replace paper or other products that are produced in other parts of the world. Hence, recycling in the Nordic countries, for example, may lead to an environmental gain in other parts of the world. On the other hand, the production of additional pulp and paper products might result in increased total production. The direct result will be increased consumption and increased environmental impacts. In the context of a future, sustainable scenario, forests and agricultural land will be used for the production of food and raw materials, as well as fuels. The competition for productive land areas can be expected to intensify. In addition, the biological diversity and long-term productive capacity of the land must be secured. If pulpwood is `saved’ through increased recycling, this can allow an increased production of renewable fuels. In some studies, the effects of using the `saved’ wood as fuels, replacing fossil fuels, have been analysed8,13,16. In all these studies, the use of the `saved’ wood as fuel leads to bene®ts for recycling compared to incineration with energy recovery. EXTERNAL FUEL FROM DIFFERENT PERSPECTIVES The energy requirements for integrated production of virgin chemical pulp and paper is, to a large extent, covered by internally produced, renewable fuel in the form of bark and liquor. When recycled ®bres replace primary pulp,
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residues from the secondary pulp production can sometimes replace the bark and liquor as energy source. Otherwise, the demand for external fuel is likely to increase. This can be fossil fuel or external, renewable fuel. However, the effect of using external, renewable fuel for producing paper based on recycled ®bres can be that less renewable fuel is available for other purposes, so that the overall use of fossil fuel is increased. If the focus is on the consequences of the recycling decision, this indirect effect should ideally be taken into account. This is not necessarily the case if the focus is on the systems to which the recycling contributes. In a sustainable future scenario, fossil fuels are probably not used. Hence, the external energy is bound to be renewable energy.
ELECTRICITY PRODUCTION FROM DIFFERENT PERSPECTIVES When recycled ®bres replace primary, mechanical or thermo-mechanical pulp, the electricity demand is reduced. The environmental gain from this reduction depends on the marginal technology for production of base-load electricity in the area. Hence, if the focus is on the consequences of the decision, the electricity production should be modelled using data for the marginal production of base-load electricity. The marginal base-load electricity will be different in different areas and time perspectives. In the short-term perspective, the marginal base-load electricity production in, e.g., the Nordic countries and in the UK, is existing, coal-based generation. In the long-term perspective, the marginal can be new power plants based on coal or natural gas39. In Sweden, the long-term marginal can also be existing nuclear power plants40. The same may be true in Germany, where the debate over nuclear power has revived in recent years. If the focus is on the systems to which we contribute, it is reasonable to model the electricity production with average data, representing the average environmental burdens of the electricity system to which we contribute. However, it is not clear if the comparison should be based on averages for the company from which the electricity is bought, for the country in which the electricity is used or for a larger electricity network to which the country might be connected30. In a sustainable future scenario, the marginal and average electricity is likely to be based on renewable energy sources, independently of where the electricity is used. If the electricity production is based on coal, this will favour newsprint recycling, which results in a reduced demand for primary, thermo-mechanical pulp. The reason is that less electricity is used in the case of recycling compared to incineration. This can be the case also for the recycling of paper packaging, as illustrated by the study by Finnveden et al.10 : when average Swedish electricity was assumed, recycling of paper packaging materials resulted in increased emissions of CO2 and SO2; however, when marginal electricity based on coal was assumed, recycling resulted in reduced emissions of CO2 and SO2. CONCLUSIONS FROM DIFFERENT PERSPECTIVES As stated in the introduction, different LCAs have arrived at different conclusions regarding which option is the best
for waste paper managementÐrecycling or incineration with energy recovery. The conclusion from our previous studies was that recycling of paper packaging materials today results in lower environmental impacts with regard to most parameters investigated26. This conclusion was somewhat contradictory to the conclusion in other studiese.g., 9,14±15,17. The difference can largely be explained by differences regarding what energy source is replaced by energy from waste paper incineration, because this is important for the Avoided Burdens in the studies. While we concluded that the competing fuel today is usually other types of solid waste, the other studies were based on the assumption or statement that the competing energy source is mainly fossil fuels. Our literature survey included two studies where the alternative fuel was other types of solid waste. These studies were carried out by Finnveden et al.10 (including two different cases and several scenarios) and Dalager et al.13 The results from these studies can be summarized as follows: · The total use of energy was lower in the recycling case. · The total use of biomass was lower in the recycling case. · The use of electricity, including nuclear power and hydropower, was lower in the recycling case. · The emissions of NOX were lower in the recycling case. · The emissions of dust were lower in the recycling case. · The emissions of oxygen depleting water emissions, measured as COD, were lower in the recycling case. · The emissions of greenhouse gases, contributing to global warming, were lower in the recycling case. · The total amount of solid waste land®lled was lower in the recycling case. · The use of fossil fuels may either increase or decrease. · The emissions of CO2 may either increase or decrease. · The emissions of SO2 may either increase or decrease. The results for most parameters in these studies thus indicate that recycling will lead to reduced environmental burdens. The exceptions are the use of fossil fuels and emissions of CO2 and SO2, which may either increase or decrease, depending on two other key factors. One is the energy source for the electricity production and the other is the fuel used at the pulp mills. The electricity demand and the emissions of NOX, dust and COD strongly depend on the technology used for pulp and paper production and ef¯uent cleaning. For this reason, the difference between recycling and incineration cannot be safely generalized to cases involving other production and waste incineration plants. However, the differences in total energy demand (including pulpwood), biomass demand, emissions of greenhouse gases, and the quantity of solid waste appear to be signi®cant with respect to variations in the technology. The signi®cant difference in greenhouse gases depends on emissions of methane from land®lls because, as noted above, waste ¯ows replaced by incinerated paper can be expected to go to land®ll where they eventually decompose to cause emissions, including methane. As mentioned above, these conclusions are based on the assumption that the alternative fuel is other waste ¯ows. From the previous discussion, this assumption appears to be valid for most countries, at least in the short-term perspective, if the decision at hand is the choice of putting Trans IChemE, Vol 78, Part B, July 2000
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 the paper either into the bin for incineration or into the bin for recycling and if the ethical starting point is that good actions are actions that have good consequences. In the context of a future sustainable scenario, the alternative energy source is likely to be renewable. This is also the case if the decision at hand is a choice between investing in increased waste incineration or in other types of renewable energy production. The conclusions obtained if waste paper replaces renewable fuel are somewhat similar to the conclusions obtained when waste paper replaces other types of solid waste25. One important difference is that replacing renewable fuel will not result in increased emissions, including methane, from land®lls. Another difference is due to the fact that the combustion of renewable fuel generates different emissions compared to incineration of `other waste ¯ows’. For example, waste incineration can generate emissions of fossil CO2 from plastics, whereas these materials are stable in land®lls and thus sequester carbon. In other cases, the alternative energy source can be fossil fuel. For example, the alternative energy source will often be fossil fuel, in the economic short-term or long-term perspectives, if the ethical starting point is that the best option is the one that contributes to the best systems. The same is true if the decision at hand is whether to increase the capacity of waste incineration with energy recovery. In this case, increased recycling results in increased use of fossil fuels and increased emissions of CO225. On the other hand it results in reduced demand for biomass and, in the LCAs covered by our literature study, to reduced electricity demand. The environmental preference between recycling and incineration with energy recovery will, in this case, depend on the priorities between different environmental issues25. For newsprint paper, recycling can be superior to waste incinerationÐin terms of CO2 emissions or impacts on climatic changeÐeven when the competing energy source is fossil fuel. A condition is that the electricity production is based on fossil fuel. This is illustrated by an early study, where the electricity was assumed to be produced in existing, coal-®red power plants8. As discussed in the section on electricity production, this assumption is valid, at least for the Nordic countries and the UK in the short-term perspective, if the ethical starting point is that good actions are actions that have good consequences. CONCLUSIONS When it comes to CO2 emissions or impacts on climatic change, the different conclusions in different LCAs can, to a large extent, be explained by differences regarding what energy source is replaced by energy from waste paper incineration. The competing fuel is likely to be other waste ¯ows, at least in the short-term perspective, if the decision at hand is the short-term choice of putting the paper either into the bin for incineration or into the bin for recycling and if the ethical starting point is that good actions are actions that have good consequences. The competing energy source is often fossil fuel, in many countries, if the decision at hand is whether to increase the capacity of waste incineration with energy recoveryÐthat is, unless the analysis is made in the context of a sustainable future scenario, and unless the decision is a choice between investing in increased waste Trans IChemE, Vol 78, Part B, July 2000
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incineration or in other types of renewable energy production. It can also, in many countries, be adequate to assume that the competing energy source is fossil fuel, if the ethical starting point is that the best option is the one that contributes to the best systems. Thus there is no clear-cut answer to the general question whether recycling or incineration with energy recovery is the environmentally better option for wastepaper management. This is true even if the question is restricted to CO2 emissions or impacts on climatic change. The results of an LCA depend on methodological choices and assumptions, and different choices are appropriate for different decisions and perspectives. To obtain an appropriate answer, the question needs to be speci®ed very carefully in terms of what decision is at hand, what is meant by `environmentally better’, and what is the time perspective and the geographical area.
REFERENCES 1. European Committee for Standardization, 1997, Environmental ManagementÐLife cycle assessment ÐPrinciples and framework, International Standard ISO 14040 (Brussels, Belgium). 2. Finnveden, G., 1999, Methodological aspects of Life Cycle Assessment of integrated solid waste management systems, Resources, Conservation and Recycling, 26: 173±187. 3. Finnveden, G. and Huppes, G. (eds), 1995, Life Cycle Assessment and Treatment of Solid Waste, Proceedings of the International Workshop, AFR-Report 98 (Swedish Environmental Protection Agency, Stockholm, Sweden). 4. Denison, R. A., 1996, Environmental life-cycle comparisons of recycling, land®lling, and incineration: A review of recent studies, Annu Rev Energy Environ, 21: 191±237. 5. AumoÃnier, S. and Coleman, T., 1997, Life cycle assessment for waste management planning, in Proceedings Sardinia 97, Sixth International Land®ll Symposium, 5: 155±164 (CISA, Cagliary, Italy). Ê (eds), 1998, Systems 6. Sundberg, J., Nybrandt, T. and Sivertun, A. Engineering Models for Waste Management, Proceedings from the international workshop in Gothenburg, AFR-report 229 (Swedish Environmental Protection Agency, Stockholm, Sweden). 7. Clift, R., Doig, A. and Finnveden, G., 2000, The application of Life Cycle Assessment to Integrated Solid Waste Management: Part 1Ð Methodology, Trans IChemE, Part B, Proc Safe Env Prot, 78 (B4): 279±287. 8. Baumann, H., Ekvall, T., Eriksson, E., Kullman, M., Rydberg, T., Ryding, S.-O., Steen, B. and Svensson, G., 1993, MiljoÈmaÈssiga skillnader mellan aÊtervinning/aÊteranvaÈndning och foÈrbraÈnning/ deponering, FoU nr 79 (Stiftelsen Reforsk, MalmoÈ, Sweden) (in Swedish). 9. Virtanen, Y. and Nilsson, S., 1993, Environmental Impacts of Waste Paper Recycling (Earthscan, London, UK). 10. Finnveden, G., Steen, B. and Sundqvist, J.-O., 1994, Kretslopp av pappersfoÈrpackningar: materialaÊtervinning eller energiaÊtervinning? En miljoÈstudie baserad paÊ fem verkliga fall, IVL Report no B1128 (Swedish Environmental Research Institute, Stockholm, Sweden) (in Swedish). 11. Granath, G. and StroÈmdahl, I., 1994, BeraÈkningar av miljoÈkonsekvenser av kretsloppspropositionen. Livscykelanalys av foÈrpackningar. Bilaga 1 till FoÈrpackningar i kretsloppet, Rapport 4300 (Swedish Environmental Protection Agency, Stockholm, Sweden) (in Swedish). Ê 12. Finnveden, G., Person, L. and Steen, B., 1994, Atervinning av mjoÈlkkartong, En LCA studie av skillnader i miljoÈbelastning. Bilaga 2 till FoÈrpackningar i kretsloppet, Rapport 4301 (Swedish Environmental Protection Agency, Stockholm, Sweden) (in Swedish). 13. Dalager, S., Drabaeck, I., Ottosen, L. M., Busch, N. J., Holmstrand, H. C., Skovgaard, M. and Mùller, F., 1995, Miljùùkonomi for papir- og papkredslùb, Miljùprosjekt nr 294 (Environmental Protection Agency, Copenhagen, Denmark) (in Danish). 14. Pajula, T. and KaÈrnaÈ, A., 1995, Life cycle scenarios of paper, in Proceedings of Ecopapertech, Helsinki, Finland, June 6±9, 191±203 (KCL, Esboo, Finland).
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15. Daae, E. and Clift, R., 1994, A life cycle assessment of the implications of paper use and recycling, IChemE Environmental Protection Bulletin, 28: 23±25. 16. Fleischer, G., and Schmidt, W. P., 1996, Functional unit for systems using raw materials, Int J LCA, 1: 23±27. 17. Leach, M., Bauen, A. and Lucas, N., 1997, A systems approach to materials ¯ows in sustainable cities, A case study of paper, Journal of Environmental Planning and Management, 40: 705±723. 18. Blum, L., Denison, R. A. and Ruston, J. F., 1998, A life-cycle approach to purchasing and using environmentally preferable paper, a summary of the paper task force report, Journal of Industrial Ecology, 1 (3): 15± 46. 19. Grieg-Gran, M., Bass, S., Bishop, J., Roberts, S., Robins, N., Sandbrook, R., Bazett, M., Gadhvi, V. and Subak, S., 1998, Towards a sustainable paper cycle, A summary, Journal of Industrial Ecology, 1 (3): 47±68. 20. Stegrin, G. and Granath, G., 1998, MiljoÈanalys av foÈrbraÈnningÐ Ê Stockholm, Sweden) (in Swedish). aÊtervinning ( AF-IPK, 21. Holmquist, J., 1999, MaterialaÊtervinning eller energiutvinning av returkartong?ÐFallstudie foÈr GoÈteborg (Dept. Environmental Sciences Program, Univeristy of Gothenburg, Sweden) (in Swedish). 22. RutegaÊrd, G., 1999, Konsekvensanalys i livscykelperspektiv av att anvaÈnda insamlade tidningar och tidskrifter till materialaÊtervinning alternativt energiutvinning (Pressretur AB, Sweden) (in Swedish). 23. Sundin, E., Svensson, N., McLaren, J. and Jackson, T., 2000, A material and energy ¯ow analysis of the UK paper cycle: 1987±2010, Journal of Industrial Ecology, Accepted for publication. 24. Ekvall, T., 1992, Life-cycle Analyses of Corrugated CardboardÐA Comparative Analysis of Two Existing Studies (CIT Ekologik 1992:3, Chalmers Industriteknik, Gothenburg, Sweden). 25. Finnveden, G. and Ekvall, T., 1998, Life-cycle assessment as a decisionsupport toolÐthe case of recycling vs. incineration of paper, Resources, Conservation and Recycling, 24: 235±256. 26. Finnveden, G. and Ekvall, T., 1998, Energi- eller materialaÊtervinning av pappersfoÈrpackningar? (Svensk KartongaÊtervinning AB, Stockholm, Sweden) (in Swedish). 27. Ekvall, T., 1999, Key methodological issues for Life Cycle Inventory analysis of paper recycling, J Cleaner Prod, 7: 281±294. 28. Ekvall, T., 2000, Life cycle assessments of paper and board recycling, in Proceedings 4th Int Conf on Env Imp of the Pulp and Paper Ind (Helsinki, Finland), 87±92. 29. Norman, R., 1998, The Moral PhilosophersÐAn Introduction to Ethics (Oxford University Press, New York). 30. Ekvall, T., 2000, Moral philosophy, economics, and Life Cycle Inventory analysis, in Proceedings Total Life Cycle Conference and Exposition, Detroit, 103±110. 31. LuÈbcke, P. (ed), 1988, Filoso®lexikonet, 143±144 (BokfoÈrlaget Forum AB, Stockholm, Sweden) (in Swedish). Ê 32. AF-IPK, 1998, Telefonintervjuer foÈr kartlaÈggning av braÈnslealternativ
33. 34.
35.
36. 37. 38. 39.
40.
vid kartongfoÈrbraÈnning i fjaÈrrvaÈrmeanlaÈggningar (Svensk KartongaÊtervinning AB, Stockholm, Sweden) (in Swedish). Ekvall, T. and Finnveden, G., 2000, Allocation in ISO 14041ÐA critical review, J Cleaner Prod, Accepted for publication. Christensen, T. H. and Kjeldsen, P., 1989, Basic biochemical processes in land®lls, in Christensen, T.H., Cossu, R. and Stegmann, R., Sanitary Land®lling: Process, Technology and Environmental Impact (Academic Press, London). Finnveden, G, Albertsson, A.-C., Berendson, J., Eriksson, E., HoÈglund, L. O., Karlsson, S. and Sundqvist, J.-O., 1995, Solid waste treatment within the framework of life-cycle assessment, J Cleaner Prod, 3: 189± 199. Clift, R., 1998, Engineering for the environment: The New Model Engineer and her role, Trans IChemE, Part B, Proc Safe Env Prot, 76(B2): 151±160. Granath, J., 1998, Increased Waste Combustion in SwedenÐPotential and Environmental Effects, Masters thesis (Chalmers University of Technology, Gothenburg and IVL, Stockholm, Sweden). Ekvall, T., 2000, A market-based approach to allocation at open-loop recycling, Resources, Conservation and Recycling, 29: 93±111. Frees, N. and Weidema, B.P., 1998, Life Cycle Assessment of Packaging Systems for Beer and Soft DrinksÐEnergy and Transport Scenarios, Environmental Project No. 406 (Danish Environmental Protection Agency, Copenhagen, Denmark). Ekvall, T., Person, L., Ryberg, A., Widheden, J., Frees, N., Nielsen, P. H., Weidema Pedersen, B. and Wesnñs, M., 1998, Life Cycle Assessment of Packaging Systems for Beer and Soft DrinksÐMain report, Environmental Project No. 399 (Danish Environmental Protection Agency, Copenhagen, Denmark).
ACKNOWLEDGEMENTS This paper includes elements from a report prepared for the Swedish Carton Recycling Company26. Financial support from the Swedish National Energy Administration and the former Swedish Waste Research Council is acknowledged. Constructive comments on earlier versions of the paper were provided by Professor Roland Clift.
ADDRESS Correspondence concerning this paper should be addressed to Mr T. Ekvall, Chalmers Industriteknik, Chalmers Teknikpark, SE-412 88 GoÈteborg, Sweden. E-mail: [email protected] The manuscript was received 18 March 1999 and accepted for publication after revision 24 May 2000.
Trans IChemE, Vol 78, Part B, July 2000
THE APPLICATION OF LIFE CYCLE ASSESSMENT TO INTEGRATED SOLID WASTE MANAGEMENT Part 2ÐPerspectives on Energy and Material Recovery from Paper T. EKVALL1 and G. FINNVEDEN2 1 Chalmers Industriteknik, GoÈteborg, Sweden Environmental Strategies Research Group (fms), Swedish Defence Research Establishment (FOA), Stockholm, Sweden
2
T
he environmental aspects of different waste management options for paper materials are the subject of an ongoing debate. A large number of life cycle assessments have been performed in order to study the topic. The comparison between recycling and incineration with energy recovery is often in focus. Different studies have arrived at different conclusions due to differences in the methods applied and assumptions made in the life cycle inventory analysis (LCI). Key factors for the LCI results include what energy is replaced by incinerated waste paper, what material is replaced by recycled ®bres, how the pulpwood savings are used, what external energy carrier is used for the recycling process, and what environmental burdens are associated with a change in the electricity demand. These factors can be investigated for different decision contexts and from different ethical, time and geographical perspectives. Different choices are appropriate for different decisions and perspectives. Hence, to obtain an adequate conclusion, the comparison needs to be speci®ed in terms of what perspectives are relevant. Keywords: life cycle assessment; waste management; recycling; incineration; paper.
INTRODUCTION
makes it possible to carry through a comprehensive evaluation of the environmental burdens and gains of the different options. However, different LCAs have arrived at different conclusions regarding which option is the best. This is, to a large extent, due to differences in the methods used for inventory analysis (LCI)24. Key issues in the LCI methodology have been identi®ed through comparisons of different studiese.g., 24±27. Important methodological issues include the de®nition of system boundaries, allocation, assumptions and choice of data. This paper presents an overview of the issues that are important for the results of the comparison between recycling and incineration with energy recovery. It also includes a discussion on what methodological choices or assumptions are appropriate for different purposes and contexts. At the end of the paper, there is a discussion on how these perspectives affect the conclusions concerning the environmental comparison between recycling and incineration with energy recovery. Direct land®ll of wastepaper and incineration without energy recovery are not dealt with in this paper, which is an elaboration on previous studiese.g., 25±28.
Environmental Life Cycle Assessment (LCA) is a study of the environmental aspects and potential impacts throughout a `product’s’ life from raw material acquisition through production and use to disposal (i.e., from cradle-to-grave)1. The term `product’ includes not only physical products but also services1, such as waste management. Essentially the same methodology, developed for product systems, can be used when LCA is applied to waste management systems, although different aspects of the methodology may come into focus2. The LCA methodology is currently being used in several countries to evaluate different strategies for integrated solid waste management as well as treatment options for speci®c waste fractionse.g., 3±6. The framework of LCA methodology and its application to solid waste management is described in Part 17. The environmental aspects of different waste management options for paper materials are the subject of an ongoing debate. A large number of LCAs have been performede.g., 8±23, and reviewed, in order to study the topic. The comparison between recycling and incineration with energy recovery is often in focus. This comparison is interesting because both waste management options may result in an environmental gain. Material recycling can reduce the environmental burdens associated with primary material production. Energy recovery can reduce the environmental burdens associated with alternative energy production. The broad, systemic approach of LCA potentially
CONSISTENT RESULTS In a previous literature survey several LCAs were compared, addressing the environmental aspects of recycling and incineration with energy recovery of paper packaging materials 25. The survey included European studies ful®lling 288
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 certain basic criteria, mainly concerning transparency and methodology. It included seven publications, with altogether 12 cases and approximately 40 scenarios8±14. One of the aims of the analysis was to see whether the different studies gave the same results, and if not, to analyse the reasons for the different results. For some parameters, the same results are obtained in all studies, cases and scenarios. One consistent result concerns the overall energy use. It turns out that the total energy use is lower in the case of recycling compared to incineration with heat recovery provided that the energy content of the pulpwood is included in the balance. This is mainly because recycling of waste paper requires less energy compared to virgin pulp and paper production. Another consistent and related result is that the use of biomass (for paper and for energy) is lower in the case of recycling compared to incineration with heat recovery. Biomass is `saved’ and can be used for some other purpose in the technosphere. KEY METHODOLOGICAL ISSUES For many of the other parameters, it turns out that the conclusions depend on certain key factors, all related to the Avoided BurdensÐ i.e., the `environmental credits’ for material or energy recovery7. The factors that are important for the environmental comparison between energy recovery and material recycling are presented with the help of Figure 1: I The environmental gain of waste incineration with energy recovery depends on what energy is replaced by the energy from wastepaper. II The environmental gain of recycling depends on what material is replaced by the recycled ®bres. III When recycled ®bres replace virgin ®bres as raw material for pulp production, the pulpwood requirements for this pulp production are reduced. The environmental consequences depend on how the pulpwood savings are used. IV When recycled ®bres replace virgin ®bres as raw material for pulp production, the available amount of internal, renewable fuel (bark, liquor) is reduced. The demand for external fuel is likely to increase, particularly
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when primary, chemical pulp is replaced. The environmental consequences depend on what external fuel is used. V When pulp based on recycled ®bres replaces primary, mechanical pulp, the electricity demand is reduced. The environmental gain from this reduction depends on how this electricity is produced. Increased transportation is sometimes mentioned as a major environmental problem associated with increased recycling. The importance of transportation for the ®nal LCI results has been analysed in several studies8±11,18,20. The conclusion throughout these studies is that transportation has a limited in¯uence on the results. This conclusion is valid for the energy demand and for emissions of CO2, SO2 and NOX, under the assumption that the transportation is reasonably ef®cient. Transportation can be important for other types of environmental problems, such as noise, cancer and respiratory diseases. It should also be noted that transportation may increase as well as decrease as a result of increased recycling. This is because, while the transportation of waste paper and recycled ®bres increases, transportation of wood and virgin ®bres is reduced. POSSIBLE PERSPECTIVES The environmental comparison between energy and material recovery can be carried out from various different perspectives. First, the comparison can be made to support different decisions. For example, the decision-makers can be consumers choosing between putting the waste paper either in a dustbin with mixed waste that goes to incineration or in a bin for source separated paper that goes to recycling. Or, they can be policy makers choosing between either investing in waste incineration plants or pushing for increased recycling rates. A third, possible decision is the choice between investing in increased waste incineration or in other types of renewable energy production. In addition, other kinds of decisions can be supported by an environmental comparison between energy and material recovery. A second dimension is that the comparison can be based on different ethical views concerning what constitutes a good action. One possible perspective is that each action should be assessed based on the consequences of that
Figure 1. Simpli®ed illustration of the system that can be affected by the choice between recycling and incineration of used paper and board. The numbers refer to key factors that are discussed in the text.
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individual action29. From this perspective, the best choice is the choice that has the best environmental consequences30. An alternative perspective is that the best choice is the choice that contributes the least to environmentally poor systems. This is consistent with the ethical view that each action should be assessed based on whether or not it conforms to a good rule30. The rule, in turn, can be assessed based on the consequences of the rule or based on another principle31. Third, the alternatives can be compared in different time perspectives. Economists distinguish between short-term and long-term perspectives. In the short-term perspective, the production capacity of different systems is assumed to be constant but the utilization of the systems varies. In the long-term perspective, the production capacity of different systems can change. In addition to the two economic time perspectives, the alternatives can be compared in the context of a sustainable future scenario. Fourth, the decision can concern different locations. As stated in Part 1, the location of processes in the Background System Ðprocesses whose selection or mode of operation is not affected directly by decisions based on the studyÐ can in general not be de®ned7. But the location of the Foreground SystemsÐi.e., the waste management systems whose selection is affected directly by decisions based on the study7Ðis often known. For example, the Foreground waste incineration might be located in Sweden, the UK or in another country. ALTERNATIVE FUEL FROM DIFFERENT PERSPECTIVES The ®rst key factor that is mentioned above is the Avoided Burdens associated with the energy production that is replaced by wastepaper incineration with energy recovery. If the paper is recycled instead of incinerated with energy recovery, another fuel will in many cases be used for replacing the energy from the paper. The question is then: which is the competing fuel? A large part of the differences between different studies can be explained by this aspect of the surrounding system25. In spite of this, the question of which is the competing fuel has been investigated in a few case studies onlye.g., 10. In other cases, it has been subject to different assumptions. In a recent study, all incineration facilities in Sweden were included in a survey addressing the question: what fuel would replace paper packaging materials in your incinerator for the next ®ve years, if the paper is recycled instead of incinerated? The most common answer was: other types of solid waste that currently are being land®lled32. Although there are no studies con®rming this, it seems likely that this answer is typical for many other countries because, in most countries, the incineration capacity is much smaller than the total amount of combustible solid waste33. Thus, there are large amounts of solid waste that are currently being land®lled and that can replace the recycled paper in the incinerators. This can be important for the comparison, if the decision at hand concerns the consumer’s choice of putting the paper either into the bin for incineration or into the bin for recycling. It means that paper that is sent to the incineration plant in most countries is likely to replace other waste ¯ows in the waste incinerator, at least in the short-term. The waste
that is replaced by incinerated paper can be expected to end up at land®lls where it is eventually decomposed, which results in emissions of, e.g., methane34±35. This should, of course, be taken into account in the environmental comparison if the ethical starting point is that (environmentally) good actions are actions that have good (environmental) consequences. In a long-term perspective, the capacity for waste incineration will perhaps be expanded until no combustible waste is disposed to land®ll. In this situation, incinerated paper will not replace other waste ¯ows. Instead, the decision to put the waste paper into the incineration bin is likely to increase the total amount of energy that is recovered from combustible waste. This may result in an increased total consumption of electricity and heat, but the energy from the waste paper may also replace energy from other sources. In most countries, such an expansion would take many years. It is, therefore, dif®cult to know what the competing energy source would be in that situation. Electricity and heat are currently, in many countries, produced primarily from fossil fuel. Investments in new plants for production of electricity and heat also assume the use of fossil fuel, in many cases. This indicates that the energy source that competes with energy from waste incineration would often be fossil fuel. However, in many countries, efforts are made to increase the use of renewable energy as a response to, e.g., the threat of global climate change. In a sustainable future scenario, fossil fuel will probably not be used, at least not with current emissions; instead, the alternative energy source is likely to be renewable. Energy from waste incineration can therefore, in some cases, compete with renewable energy sources, particularly biomass in the form of energy crops and agricultural waste, which is an alternative fuel for combined heat-and-power plants. Another aspect, which may change the competing fuel, is the type of furnace that can be used for waste paper incineration. The studies addressing this question have normally assumed that the paper is combusted in incinerators for mixed municipal waste. However, pure waste paper fractions might on some occasions be combusted in a less advanced furnace for solid fuels, where combustion of other types of solid waste is not allowed. Such furnaces can be used for heating purposes36±37 or for the production of steam and electricity at paper mills. In this case, the waste paper may replace other types of fuel rather than other waste ¯ows. What fuel is replaced depends on whether the energy in the waste paper is recovered in the form of heat and/or electricity. It also depends on where in the world the waste incinerator is located. Finally, it depends on the time perspective of the comparison. As indicated above, the alternative fuel is, in many cases, fossil fuel in the economic short-term or longterm perspectives. In a sustainable future scenario, the alternative energy is likely to be renewable energy. The discussion above is based on the assumption that the decision at hand is the choice of putting the paper either into the bin for incineration or into the bin for recycling and that the ethical starting point is that good actions are actions that have good consequences. If the ethical starting point is that the best option is the one that contributes to the best systemsÐa signi®cantly different approach (see above)Ðit is necessary to evaluate the systems to which the consumer contributes when routing paper for recycling or for energy recovery. It is possible to regard the total waste incineration Trans IChemE, Vol 78, Part B, July 2000
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 in, e.g., a country as the system to which the consumer contributes. When evaluating this system, it is reasonable to account for the Avoided Burdens attributable to the energy recovered through waste incineration. Without this energy, the demand for other energy sources would probably be greater. In this sense, the energy from the total waste incineration replaces other energy sources. The environmental implications of this replacement depend on the competing energy source at that time and location. In the economic short-term or long-term perspectives, energy from the total waste incineration often competes with fossil fuel. In a sustainable future scenario, the alternative energy is likely to be renewable energy. Alternatively, the decision at hand may be the choice between investing in new capacity for waste incineration with energy recovery or pushing for increased recycling rates. This decision will affect the total amount of energy that is recovered from combustible waste. An increased energy ¯ow from the waste management sector may replace other energy sources. Again, the environmental implications of this replacement depend on the competing energy source at that time and location. If the decision at hand is the choice between investing in increased waste incineration capacity or in energy plants based on other types of renewable energy, this decision will also affect the total amount of energy that is recovered from combustible waste and, hence, the Avoided Burdens. However, in this case, the competing energy source is obviously the renewable energy that would be utilized in the alternative energy plant. ALTERNATIVE MATERIAL FROM DIFFERENT PERSPECTIVES In most LCAs, it is assumed that the recycled ®bres from the system investigated replace virgin ®bres. In fact, the recycled material may also replace recycled ®bres from other sources, completely different types of material or no material at all33. Paper that is collected for recycling enters an international market, where it competes with waste paper from, e.g., other countries38. Increased collection for recycling in one country may result in increased use of recycled ®bres, but it may also result in reduced collection in other countries. This can be important for the comparison, at least if the decision at hand is the choice between putting the paper into the bin for incineration or the bin for recycling. It means that paper that is sent to recycling in part replaces other waste paper ¯ows. The other waste paper ¯ows will then end up at land®lls or waste incinerators. In the latter case, they will push other waste ¯ows to the land®ll, as long as the situation continues in which waste incinerator capacity is smaller than the quantity of available, combustible waste. This reduces the environmental gain from the Foreground paper collection. If the ethical starting point is that the best option is the one with the best consequences, the environmental advantages of recycling are smaller compared to the case when the recycled ®bres from the system investigated replace virgin ®bres. If the recycled paper replaces other types of materials, such as plastics, wood or mineral wool, the Avoided Burdens will depend on the material replaced. If the recycled ®bres replace plastics made from virgin materials, Trans IChemE, Vol 78, Part B, July 2000
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recycling probably leads to reduced use of fossil fuels with their associated environmental problems. If the ethical starting point is that the best option is the one that contributes to the best systems, it can be argued that sending the paper to recycling contributes to the recycling system. This system is good, it can be argued, because it results in an environmental gain, partly originating from the reduction in pulpwood demand (or other natural resources) and partly from energy savings in the pulping processes (or other material production processes). However, it should be noted that sending the paper waste to recycling is not suf®cient to obtain this environmental gainÐit is also necessary to demand products based on recycled ®bres instead of products based on virgin material. Hence, it can be argued also from this ethical starting point that the environmental advantages of sending paper waste to recycling are smaller than most recent LCAs indicate. If the decision at hand is to implement a strategy that results in increased total recycling rates for paper, this strategy will, of course, result in the full environmental gain of increased recycling. From above it can be concluded, however, that the strategy might be ineffective if it only stimulates the collection of paper waste in a limited geographical area. ALTERNATIVE PULPWOOD USE FROM DIFFERENT PERSPECTIVES When recycled ®bres replace virgin ®bres as raw material for pulp production, the pulpwood requirements for this pulp production are reduced. The type and magnitude of the environmental consequences depend on the alternative use of the pulpwood that is saved through recycling. In the short term, this pulpwood might be used for production of other pulp and paper products. These products might, in part, replace paper or other products that are produced in other parts of the world. Hence, recycling in the Nordic countries, for example, may lead to an environmental gain in other parts of the world. On the other hand, the production of additional pulp and paper products might result in increased total production. The direct result will be increased consumption and increased environmental impacts. In the context of a future, sustainable scenario, forests and agricultural land will be used for the production of food and raw materials, as well as fuels. The competition for productive land areas can be expected to intensify. In addition, the biological diversity and long-term productive capacity of the land must be secured. If pulpwood is `saved’ through increased recycling, this can allow an increased production of renewable fuels. In some studies, the effects of using the `saved’ wood as fuels, replacing fossil fuels, have been analysed8,13,16. In all these studies, the use of the `saved’ wood as fuel leads to bene®ts for recycling compared to incineration with energy recovery. EXTERNAL FUEL FROM DIFFERENT PERSPECTIVES The energy requirements for integrated production of virgin chemical pulp and paper is, to a large extent, covered by internally produced, renewable fuel in the form of bark and liquor. When recycled ®bres replace primary pulp,
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residues from the secondary pulp production can sometimes replace the bark and liquor as energy source. Otherwise, the demand for external fuel is likely to increase. This can be fossil fuel or external, renewable fuel. However, the effect of using external, renewable fuel for producing paper based on recycled ®bres can be that less renewable fuel is available for other purposes, so that the overall use of fossil fuel is increased. If the focus is on the consequences of the recycling decision, this indirect effect should ideally be taken into account. This is not necessarily the case if the focus is on the systems to which the recycling contributes. In a sustainable future scenario, fossil fuels are probably not used. Hence, the external energy is bound to be renewable energy.
ELECTRICITY PRODUCTION FROM DIFFERENT PERSPECTIVES When recycled ®bres replace primary, mechanical or thermo-mechanical pulp, the electricity demand is reduced. The environmental gain from this reduction depends on the marginal technology for production of base-load electricity in the area. Hence, if the focus is on the consequences of the decision, the electricity production should be modelled using data for the marginal production of base-load electricity. The marginal base-load electricity will be different in different areas and time perspectives. In the short-term perspective, the marginal base-load electricity production in, e.g., the Nordic countries and in the UK, is existing, coal-based generation. In the long-term perspective, the marginal can be new power plants based on coal or natural gas39. In Sweden, the long-term marginal can also be existing nuclear power plants40. The same may be true in Germany, where the debate over nuclear power has revived in recent years. If the focus is on the systems to which we contribute, it is reasonable to model the electricity production with average data, representing the average environmental burdens of the electricity system to which we contribute. However, it is not clear if the comparison should be based on averages for the company from which the electricity is bought, for the country in which the electricity is used or for a larger electricity network to which the country might be connected30. In a sustainable future scenario, the marginal and average electricity is likely to be based on renewable energy sources, independently of where the electricity is used. If the electricity production is based on coal, this will favour newsprint recycling, which results in a reduced demand for primary, thermo-mechanical pulp. The reason is that less electricity is used in the case of recycling compared to incineration. This can be the case also for the recycling of paper packaging, as illustrated by the study by Finnveden et al.10 : when average Swedish electricity was assumed, recycling of paper packaging materials resulted in increased emissions of CO2 and SO2; however, when marginal electricity based on coal was assumed, recycling resulted in reduced emissions of CO2 and SO2. CONCLUSIONS FROM DIFFERENT PERSPECTIVES As stated in the introduction, different LCAs have arrived at different conclusions regarding which option is the best
for waste paper managementÐrecycling or incineration with energy recovery. The conclusion from our previous studies was that recycling of paper packaging materials today results in lower environmental impacts with regard to most parameters investigated26. This conclusion was somewhat contradictory to the conclusion in other studiese.g., 9,14±15,17. The difference can largely be explained by differences regarding what energy source is replaced by energy from waste paper incineration, because this is important for the Avoided Burdens in the studies. While we concluded that the competing fuel today is usually other types of solid waste, the other studies were based on the assumption or statement that the competing energy source is mainly fossil fuels. Our literature survey included two studies where the alternative fuel was other types of solid waste. These studies were carried out by Finnveden et al.10 (including two different cases and several scenarios) and Dalager et al.13 The results from these studies can be summarized as follows: · The total use of energy was lower in the recycling case. · The total use of biomass was lower in the recycling case. · The use of electricity, including nuclear power and hydropower, was lower in the recycling case. · The emissions of NOX were lower in the recycling case. · The emissions of dust were lower in the recycling case. · The emissions of oxygen depleting water emissions, measured as COD, were lower in the recycling case. · The emissions of greenhouse gases, contributing to global warming, were lower in the recycling case. · The total amount of solid waste land®lled was lower in the recycling case. · The use of fossil fuels may either increase or decrease. · The emissions of CO2 may either increase or decrease. · The emissions of SO2 may either increase or decrease. The results for most parameters in these studies thus indicate that recycling will lead to reduced environmental burdens. The exceptions are the use of fossil fuels and emissions of CO2 and SO2, which may either increase or decrease, depending on two other key factors. One is the energy source for the electricity production and the other is the fuel used at the pulp mills. The electricity demand and the emissions of NOX, dust and COD strongly depend on the technology used for pulp and paper production and ef¯uent cleaning. For this reason, the difference between recycling and incineration cannot be safely generalized to cases involving other production and waste incineration plants. However, the differences in total energy demand (including pulpwood), biomass demand, emissions of greenhouse gases, and the quantity of solid waste appear to be signi®cant with respect to variations in the technology. The signi®cant difference in greenhouse gases depends on emissions of methane from land®lls because, as noted above, waste ¯ows replaced by incinerated paper can be expected to go to land®ll where they eventually decompose to cause emissions, including methane. As mentioned above, these conclusions are based on the assumption that the alternative fuel is other waste ¯ows. From the previous discussion, this assumption appears to be valid for most countries, at least in the short-term perspective, if the decision at hand is the choice of putting Trans IChemE, Vol 78, Part B, July 2000
APPLICATION OF LCA TO INTEGRATED SOLID WASTE MANAGEMENT: PART 2 the paper either into the bin for incineration or into the bin for recycling and if the ethical starting point is that good actions are actions that have good consequences. In the context of a future sustainable scenario, the alternative energy source is likely to be renewable. This is also the case if the decision at hand is a choice between investing in increased waste incineration or in other types of renewable energy production. The conclusions obtained if waste paper replaces renewable fuel are somewhat similar to the conclusions obtained when waste paper replaces other types of solid waste25. One important difference is that replacing renewable fuel will not result in increased emissions, including methane, from land®lls. Another difference is due to the fact that the combustion of renewable fuel generates different emissions compared to incineration of `other waste ¯ows’. For example, waste incineration can generate emissions of fossil CO2 from plastics, whereas these materials are stable in land®lls and thus sequester carbon. In other cases, the alternative energy source can be fossil fuel. For example, the alternative energy source will often be fossil fuel, in the economic short-term or long-term perspectives, if the ethical starting point is that the best option is the one that contributes to the best systems. The same is true if the decision at hand is whether to increase the capacity of waste incineration with energy recovery. In this case, increased recycling results in increased use of fossil fuels and increased emissions of CO225. On the other hand it results in reduced demand for biomass and, in the LCAs covered by our literature study, to reduced electricity demand. The environmental preference between recycling and incineration with energy recovery will, in this case, depend on the priorities between different environmental issues25. For newsprint paper, recycling can be superior to waste incinerationÐin terms of CO2 emissions or impacts on climatic changeÐeven when the competing energy source is fossil fuel. A condition is that the electricity production is based on fossil fuel. This is illustrated by an early study, where the electricity was assumed to be produced in existing, coal-®red power plants8. As discussed in the section on electricity production, this assumption is valid, at least for the Nordic countries and the UK in the short-term perspective, if the ethical starting point is that good actions are actions that have good consequences. CONCLUSIONS When it comes to CO2 emissions or impacts on climatic change, the different conclusions in different LCAs can, to a large extent, be explained by differences regarding what energy source is replaced by energy from waste paper incineration. The competing fuel is likely to be other waste ¯ows, at least in the short-term perspective, if the decision at hand is the short-term choice of putting the paper either into the bin for incineration or into the bin for recycling and if the ethical starting point is that good actions are actions that have good consequences. The competing energy source is often fossil fuel, in many countries, if the decision at hand is whether to increase the capacity of waste incineration with energy recoveryÐthat is, unless the analysis is made in the context of a sustainable future scenario, and unless the decision is a choice between investing in increased waste Trans IChemE, Vol 78, Part B, July 2000
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incineration or in other types of renewable energy production. It can also, in many countries, be adequate to assume that the competing energy source is fossil fuel, if the ethical starting point is that the best option is the one that contributes to the best systems. Thus there is no clear-cut answer to the general question whether recycling or incineration with energy recovery is the environmentally better option for wastepaper management. This is true even if the question is restricted to CO2 emissions or impacts on climatic change. The results of an LCA depend on methodological choices and assumptions, and different choices are appropriate for different decisions and perspectives. To obtain an appropriate answer, the question needs to be speci®ed very carefully in terms of what decision is at hand, what is meant by `environmentally better’, and what is the time perspective and the geographical area.
REFERENCES 1. European Committee for Standardization, 1997, Environmental ManagementÐLife cycle assessment ÐPrinciples and framework, International Standard ISO 14040 (Brussels, Belgium). 2. Finnveden, G., 1999, Methodological aspects of Life Cycle Assessment of integrated solid waste management systems, Resources, Conservation and Recycling, 26: 173±187. 3. Finnveden, G. and Huppes, G. (eds), 1995, Life Cycle Assessment and Treatment of Solid Waste, Proceedings of the International Workshop, AFR-Report 98 (Swedish Environmental Protection Agency, Stockholm, Sweden). 4. Denison, R. A., 1996, Environmental life-cycle comparisons of recycling, land®lling, and incineration: A review of recent studies, Annu Rev Energy Environ, 21: 191±237. 5. AumoÃnier, S. and Coleman, T., 1997, Life cycle assessment for waste management planning, in Proceedings Sardinia 97, Sixth International Land®ll Symposium, 5: 155±164 (CISA, Cagliary, Italy). Ê (eds), 1998, Systems 6. Sundberg, J., Nybrandt, T. and Sivertun, A. Engineering Models for Waste Management, Proceedings from the international workshop in Gothenburg, AFR-report 229 (Swedish Environmental Protection Agency, Stockholm, Sweden). 7. Clift, R., Doig, A. and Finnveden, G., 2000, The application of Life Cycle Assessment to Integrated Solid Waste Management: Part 1Ð Methodology, Trans IChemE, Part B, Proc Safe Env Prot, 78 (B4): 279±287. 8. Baumann, H., Ekvall, T., Eriksson, E., Kullman, M., Rydberg, T., Ryding, S.-O., Steen, B. and Svensson, G., 1993, MiljoÈmaÈssiga skillnader mellan aÊtervinning/aÊteranvaÈndning och foÈrbraÈnning/ deponering, FoU nr 79 (Stiftelsen Reforsk, MalmoÈ, Sweden) (in Swedish). 9. Virtanen, Y. and Nilsson, S., 1993, Environmental Impacts of Waste Paper Recycling (Earthscan, London, UK). 10. Finnveden, G., Steen, B. and Sundqvist, J.-O., 1994, Kretslopp av pappersfoÈrpackningar: materialaÊtervinning eller energiaÊtervinning? En miljoÈstudie baserad paÊ fem verkliga fall, IVL Report no B1128 (Swedish Environmental Research Institute, Stockholm, Sweden) (in Swedish). 11. Granath, G. and StroÈmdahl, I., 1994, BeraÈkningar av miljoÈkonsekvenser av kretsloppspropositionen. Livscykelanalys av foÈrpackningar. Bilaga 1 till FoÈrpackningar i kretsloppet, Rapport 4300 (Swedish Environmental Protection Agency, Stockholm, Sweden) (in Swedish). Ê 12. Finnveden, G., Person, L. and Steen, B., 1994, Atervinning av mjoÈlkkartong, En LCA studie av skillnader i miljoÈbelastning. Bilaga 2 till FoÈrpackningar i kretsloppet, Rapport 4301 (Swedish Environmental Protection Agency, Stockholm, Sweden) (in Swedish). 13. Dalager, S., Drabaeck, I., Ottosen, L. M., Busch, N. J., Holmstrand, H. C., Skovgaard, M. and Mùller, F., 1995, Miljùùkonomi for papir- og papkredslùb, Miljùprosjekt nr 294 (Environmental Protection Agency, Copenhagen, Denmark) (in Danish). 14. Pajula, T. and KaÈrnaÈ, A., 1995, Life cycle scenarios of paper, in Proceedings of Ecopapertech, Helsinki, Finland, June 6±9, 191±203 (KCL, Esboo, Finland).
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15. Daae, E. and Clift, R., 1994, A life cycle assessment of the implications of paper use and recycling, IChemE Environmental Protection Bulletin, 28: 23±25. 16. Fleischer, G., and Schmidt, W. P., 1996, Functional unit for systems using raw materials, Int J LCA, 1: 23±27. 17. Leach, M., Bauen, A. and Lucas, N., 1997, A systems approach to materials ¯ows in sustainable cities, A case study of paper, Journal of Environmental Planning and Management, 40: 705±723. 18. Blum, L., Denison, R. A. and Ruston, J. F., 1998, A life-cycle approach to purchasing and using environmentally preferable paper, a summary of the paper task force report, Journal of Industrial Ecology, 1 (3): 15± 46. 19. Grieg-Gran, M., Bass, S., Bishop, J., Roberts, S., Robins, N., Sandbrook, R., Bazett, M., Gadhvi, V. and Subak, S., 1998, Towards a sustainable paper cycle, A summary, Journal of Industrial Ecology, 1 (3): 47±68. 20. Stegrin, G. and Granath, G., 1998, MiljoÈanalys av foÈrbraÈnningÐ Ê Stockholm, Sweden) (in Swedish). aÊtervinning ( AF-IPK, 21. Holmquist, J., 1999, MaterialaÊtervinning eller energiutvinning av returkartong?ÐFallstudie foÈr GoÈteborg (Dept. Environmental Sciences Program, Univeristy of Gothenburg, Sweden) (in Swedish). 22. RutegaÊrd, G., 1999, Konsekvensanalys i livscykelperspektiv av att anvaÈnda insamlade tidningar och tidskrifter till materialaÊtervinning alternativt energiutvinning (Pressretur AB, Sweden) (in Swedish). 23. Sundin, E., Svensson, N., McLaren, J. and Jackson, T., 2000, A material and energy ¯ow analysis of the UK paper cycle: 1987±2010, Journal of Industrial Ecology, Accepted for publication. 24. Ekvall, T., 1992, Life-cycle Analyses of Corrugated CardboardÐA Comparative Analysis of Two Existing Studies (CIT Ekologik 1992:3, Chalmers Industriteknik, Gothenburg, Sweden). 25. Finnveden, G. and Ekvall, T., 1998, Life-cycle assessment as a decisionsupport toolÐthe case of recycling vs. incineration of paper, Resources, Conservation and Recycling, 24: 235±256. 26. Finnveden, G. and Ekvall, T., 1998, Energi- eller materialaÊtervinning av pappersfoÈrpackningar? (Svensk KartongaÊtervinning AB, Stockholm, Sweden) (in Swedish). 27. Ekvall, T., 1999, Key methodological issues for Life Cycle Inventory analysis of paper recycling, J Cleaner Prod, 7: 281±294. 28. Ekvall, T., 2000, Life cycle assessments of paper and board recycling, in Proceedings 4th Int Conf on Env Imp of the Pulp and Paper Ind (Helsinki, Finland), 87±92. 29. Norman, R., 1998, The Moral PhilosophersÐAn Introduction to Ethics (Oxford University Press, New York). 30. Ekvall, T., 2000, Moral philosophy, economics, and Life Cycle Inventory analysis, in Proceedings Total Life Cycle Conference and Exposition, Detroit, 103±110. 31. LuÈbcke, P. (ed), 1988, Filoso®lexikonet, 143±144 (BokfoÈrlaget Forum AB, Stockholm, Sweden) (in Swedish). Ê 32. AF-IPK, 1998, Telefonintervjuer foÈr kartlaÈggning av braÈnslealternativ
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ACKNOWLEDGEMENTS This paper includes elements from a report prepared for the Swedish Carton Recycling Company26. Financial support from the Swedish National Energy Administration and the former Swedish Waste Research Council is acknowledged. Constructive comments on earlier versions of the paper were provided by Professor Roland Clift.
ADDRESS Correspondence concerning this paper should be addressed to Mr T. Ekvall, Chalmers Industriteknik, Chalmers Teknikpark, SE-412 88 GoÈteborg, Sweden. E-mail: [email protected] The manuscript was received 18 March 1999 and accepted for publication after revision 24 May 2000.
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