摘要
The authors develop a methodological framework for the environmental assessment of materials recycling systems. Typically such systems exhibit both dynamic and non-linear behaviour. By contrast, many existing environmental assessment techniques (such as Life Cycle Assessment and Materials Flow Analysis) employ a static linear model of the underlying system. This paper first reviews some of the attempts to develop dynamic non-linear models for materials systems. It then discusses the structural peculiarities of recycling systems drawing attention in particular to the presence of dynamic features (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 techniques are used to assess the energy requirements of a hypothetical recycling system possessing both dynamic and non-linear features. The difference in system energy intensity derived using the different types of model are analysed. Finally, the paper discusses the policy implications of these results.