Modelling material cascades - frameworks for the environmental assessment of recycling systems

The authors develop a methodological framework for the environmental assess ment of materials recycling systems. Typically such systems exhibit both dy namic and non-linear behaviour. By contrast, many existing environmental as sessment techniques (such as Life Cycle Assessment and Materials Flow Analy sis) employ a static linear model of the underlying system. This paper firs t reviews some of the attempts to develop dynamic non-linear models for mat erials systems. It then discusses the structural peculiarities of recycling systems drawing attention in particular to the presence of dynamic feature s (such as time lags between production and disposal) and non-linearities ( such as the dependency of scrap collection energies on the flow of material through the recycling loop). The principal analytic task of this paper is to construct an illustrative case study, in which different modelling techn iques are used to assess the energy requirements of a hypothetical recyclin g system possessing both dynamic and non-linear features. The difference in system energy intensity derived using the different types of model are ana lysed. Finally, the paper discusses the policy implications of these result s. (C) 2000 Elsevier Science B.V. All rights reserved.