Heijungs Reinout, Guinée Jeroen B
Institute of Environmental Sciences (CML), Leiden University, PO Box 9518, 2300 RA Leiden, The Netherlands.
Waste Manag. 2007;27(8):997-1005. doi: 10.1016/j.wasman.2007.02.013. Epub 2007 Apr 3.
Many modern waste treatment processes and waste management systems are able to treat many different types of waste at the same time, and deliver a number of useful outputs (secondary materials, energy) as well. These systems are thus increasingly multi-functional. As such, in life cycle assessment studies, they create problems related to multi-functionality and allocation. Especially in LCAs of waste management systems, the solution in the form of system expansion or avoided burdens approach dominates the practice, and the partitioning approach plays a minor role. In this paper, we analyse the logic and problems of these two approaches. It appears that for the avoided burdens approach, the number of 'what-if' assumptions is so large that LCAs on the same topic lead to quite diverging results. Since 'what-if' questions cannot be answered in an unambiguous way, such questions should preferably be left outside of a primarily scientific tool. The partitioning approach is not free from arbitrary choices as well, but, in contrast to the 'what-if' approaches, it does not claim to predict what happens or what would have happened.
许多现代废物处理工艺和废物管理系统能够同时处理多种不同类型的废物，还能产生一些有用的产出（二次材料、能源）。因此，这些系统的多功能性日益增强。正因如此，在生命周期评估研究中，它们引发了与多功能性和分配相关的问题。尤其是在废物管理系统的生命周期评估中，以系统扩展或避免负担法形式的解决方案在实践中占主导地位，而划分法的作用较小。在本文中，我们分析了这两种方法的逻辑和问题。看来，对于避免负担法，“如果……会怎样”的假设数量如此之多，以至于关于同一主题的生命周期评估会得出相当不同的结果。由于“如果……会怎样”的问题无法以明确的方式得到解答，这类问题最好不要纳入主要的科学工具之中。划分法也并非没有任意性的选择，但与“如果……会怎样”的方法不同，它并不声称能够预测实际发生的情况或本来会发生的情况。
