Life-cycle assessment as a decision-support tool-the case of recycling versus incineration of paper

摘要

Recently published life-cycle assessments (LCAs) on recycling and incineration with energy recovery of paper packaging materials are used as examples in order to discuss the usefulness of LCAs. The type of information that can typically be produced by an LCA is described. The reproducibility of LCAs is evaluated and reasons for possible discrepancies between LCAs are discussed. An attempt is also made to make conclusions on advantages to the environment of recycling versus incineration of paper packaging materials, and discuss lessons learned that can be applied to other materials. In all seven studies, including 12 cases and 27 scenarios, total energy use is consistently lower when paper packaging materials are recycled rather than incinerated. Other, differing results can be explained by the assumptions made concerning the energy source used instead of the energy from incineration when paper is recycled instead of incinerated (called 'the alternative energy source'). If fossil fuels are the alternative energy source, incinerated paper replaces fossil fuels, and emissions of CO_2 can be decreased. If, on the other hand solid waste (which in other cases would have been landfilled), or biofuels are the alternative energy source, fossil fuels will not be replaced. In these cases, increased recycling will in general lead to decreased emissions of greenhouse gases. It is suggested that the alternative energy source for the near future is usually solid waste. In the longer term this depends on political decisions on waste management in general. Studies which address the issue of transportation consistently conclude that as long as it is reasonably efficient, transportation will not have any effect on the conclusions. It is noted that not all relevant environmental impacts are considered in the studies reviewed. This is one reason why none of the discussed LCAs can alone be used to determine the environmental preference of the alternatives studied. Another reason is that the question is too narrow. The ranking order by environmental impact of the alternatives may depend on other policy decisions. Some of the LCAs can however be used to identify key issues, i.e. critical aspects which need further study or should be considered when choosing between recycling and incineration. Equally important, some of the LCAs can be used to identify aspects which are of limited importance for the decision. It is suggested that this is typical for current LCAs and presumably also for future ones.