The application of life cycle assessment to process optimisation

Abstract

One of the main potential uses of life cycle assessment (LCA) in environmental management is for identifying options for environmental improvements of a system in which complete supply chains are considered. The main problem, however, lies in finding the optimum improvement strategies and choosing the best alternative in a decision environment with multiple, and often conflicting, objectives. To aid the decision-making process, this paper proposes the use of multiobjective optimisation (MO), whereby the system is simultaneously optimised on a number of environmental objective functions, defined and quantified through the LCA approach. This results in a Pareto or noninferior surface, with a range of environmental optima, from which the best compromise solution for improving the environmental performance of the system can be chosen. However, system improvements cannot be based solely on environmental considerations and other factors, including socio-economic, must be considered in parallel. This paper also shows that MO coupled with LCA provides a powerful tool for balancing environmental and economic performance, thus enabling the choice of best practicable environmental option (BPEO) and best available technique not entailing excessive cost (BATNEEC). The value of this approach in environmental system analysis lies in providing a set of alternative optimal options for system improvements rather than a single prescriptive solution, which may be optimal but not necessarily appropriate for a particular situation. A decision–aid tool–optimum LCA performance (OLCAP)–has been developed for these purposes. OLCAP is tested and demonstrated by application to a case study of an existing mineral-processing system producing boron products. It is shown that LCA can successfully be combined with optimisation techniques to satisfy both economic and environmental criteria for more sustainable performance of the product system over the whole life cycle.