Life cycle assessment and its application to process selection, design andoptimisation

As the pressures on the chemical and process industries to improve their en vironmental performance are increasing, the need to move away from narrow s ystem definitions and concepts in environmental system management is becomi ng more apparent. Life Cycle Assessment (LCA) is gaining wider acceptance a s a method that enables quantification of environmental interventions and e valuation of the improvement options throughout the life cycle of a process , product or activity. Historically, LCA has mainly been applied to product s; however, recent literature suggests that it can assist in identifying mo re sustainable options in process selection, design and optimisation. This paper reviews some of these newly emerging applications of LCA. A number of case studies indicate that process selection must be based on consideratio ns of the environment as a whole, including indirect releases, consumption of raw materials and waste disposal. This approach goes beyond the present practice of choosing Best Practicable Environmental Option (BPEO), by which it is possible to reduce the environmental impacts directly from the plant , but to increase them elsewhere in the life cycle. These issues are discus sed and demonstrated by the examples of end-of-pipe abatement techniques fo r SO2, NO, and VOCs and processes for the production of liquid CO2 and O-2. The integration of LCA into the early stages of process design and optimis ation is also reviewed and discussed. The approach is outlined and illustra ted with real case studies related to the mineral and chemical industries. It is shown that a newly emerging Life Cycle Process Design (LCPD) tool off ers a potential for technological innovation in process concept and structu re through the selection of best material and process alternatives over the whole life cycle. The literature also suggests that LCA coupled with multi -objective optimisation (MO) provides a robust framework for process design by simultaneously optimising on environmental, technical, economic and oth er criteria. Pareto-optimum solutions obtained in MO provide a number of op tions for improved design and operation throughout the whole life cycle: Th is approach therefore provides a potentially powerful decision making tool which may help to identify more sustainable solutions in the process indust ries. (C) 1999 Elsevier Science S.A. All rights reserved.