The refined model for inventory analysis

Abstract

Title The computational structure of life cycle assessment [eReserve]. Chapter 3 Published Kluwer Academic Publishers, c2002 Access Online The computational structure of life cycle assessment [eReserve]. Chapter 3 .pdf 1.25mb Location Call Number Status (About status) eReserve Note Source: Chapter 3, p.33-98 in Heijungs, R. and Suh, S. (2002) The computational structure of life cycle assessment ISBN: 1402006721 The basic model for inventory analysis presented in Chapter 2 is appealing for reasons of simplicity and generality. In practice, however, things are more complicated for a variety of reasons, some of which have been listed already in Section 2.4. This calls for adaptations of the matrix approach. This chapter discusses the most important situations that lead to a read­ justment of the model or its solution. It also shows how the formalism can be used for less trivial processes and flows, such as those relating to transport. 3.1 Cut-off Cut-off refers to the case of incomplete systems, or formulated differently, to the case of systems with incomplete knowledge on product flows between processes. One may, for instance, know that production of electricity not only requires fuel, but that capital equipment, like a generator, is involved as well. But it may happen that one cannot find data on the production of new generators for replacement, or for the disposal of used generators. Problems in data acquisition appear in almost every LCA. Most guide­ books provide criteria to decide when cut-off is permissible: for which pro­ cesses, depending on the decision-context and on the product under investi­ gation. This book will not provide or discuss such guidelines. The emphasis is on how cut-off is implemented in the matrix formalism of Chapter 2. As far as we are aware, this aspect of cut-off has been discussed only by Hei­ jungs (1997, p.9 3-95). Another approach is to avoid the need for cut-off by 33