Tools for evaluating waste treatment processes – Methods and results
For some time, the Committee of Experts on Waste Treatment and Materials Recovery by the German Association of Engineers (VDI) has been dealing intensively with the following issue: How can the sustainability of different waste treatment processes be evaluated transparently and comprehensibly?
Contentious discussions between engineers and scientists in this Committee of Experts about the different scientific/technological evaluation methods for waste treatment processes culminated in this publication, the purpose of which is to examine the hitherto most frequently used methods in terms of their practicability:
- Mass and energy balances (Professor Reinhard Scholz, Clausthal University of Technology; Professor Michael Beckmann, Bauhaus University Weimar)
- Materials balances (Professor Paul H. Brunner and Professor Helmut Rechberger, Vienna University of Technology)
- Life cycle assessments (Professor Liselotte Schebek, FZK-Karlsruhe Research Center)
- Cost effectiveness analysis (Professor Paul H. Brunner and Dr. Gernot Döberl, Vienna University of Technology)
- Eco-efficiency analysis (Dr. Andreas Kicherer, BASF Ludwigshafen)
- Additional consideration of social aspects (Dr. Isabell Schmidt, KPMG Advisory Services)
- Landfilling and mechanical biological waste treatment (Dr. Konrad Soyez, - Potsdam University)
- Use of energy from waste (Professor Thomas Kolb, Karlsruhe research center)
For the purpose of illustration, the evaluation methods are used to examine the handling of municipal waste. This type of waste has not been selected because it poses the most urgent problem for sustainable management. However, the issue of municipal waste is in general relatively clear and coherent; it is also particularly suitable for use in comparing the evaluation methods.
- In the USA, for example, economic costs are the main criterion for decisions. As a result, waste is disposed of in cheap mega landfill sites far removed from the population centers. How would actions change if the social costs of damage to the environment caused by landfill gases and the use of resources for transport were taken into consideration?
- In Germany, recycling quotas are set for the disposal of packaging materials; the quotas are checked against mass or materials balances. As a result, the costs for collecting packaging waste are high, and the yellow containers and sacks used must be transported by lorries suitable for low-density materials. Would solutions of this kind be implemented if life cycle assessments or eco-efficiency analyses were used as the basis for decisions?
- The EU waste hierarchy also advocates the materials balance oriented approach. But are the practices arising from this method also really feasible in terms of achieving sustainable development?
- In the Netherlands, electricity produced by waste treatment plants is subsidized by the state. As a result, huge increases in the efficiencies of waste-to-energy plants occurred. The decision to subsidize of electric power generation was based on the evaluation of energy balances. In addition, the limit values for NOx emissions were relaxed to further increase the potential for energy recovery from waste. Is this justified?
The more precisely the task is defined, the more reliable the result of the evaluation. The mass and energy balances form the basis for each evaluation. The materials balance provides information about the mass air emissions to be expected locally, while the life cycle assessment describes the process's impact on the environment. The cost effectiveness analysis also includes the costs of achieving individual process targets, while the eco-efficiency analysis weights both the economic and ecological burdens of the process. The social eco-efficiency analysis takes additional social aspects of a particular process into account. Depending on the issue in question, the appropriate tool can be used. The fact that the number of subjective criteria included in the evaluation rises with increasing complexity of the issue and therefore also of the evaluation method must also be taken into account.
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