Indices for comparative waste assessment in environmentally-conscious manufacturing

With the expansion of pollution-prevention initiatives in the government sector, development of certification and eco-labeling mechanisms in foreign trade, and the emergence of "green" market drivers for consumer demand, industry is under increasing pressure to evaluate the "life-cycle" waste streams which emanate from their products and manufacturing processes. While much research has been devoted to the study of "system-level" design-for-environment (i.e. design for disassembly, serviceability, modularity), little attention has been given to the influence of planning and design decisions at the unit manufacturing process level, which has a significant impact on waste streams through material, catalyst, parameter and feature selection decisions One of the most pressing issues in environmentally-conscious manufacturing is the ability to compare the environmental impacts of dissimilar waste streams to formulate the above decisions. This paper presents an overview of the hierarchical levels of comparative waste assessment which links process-level emissions to immediate, site-wide, and eco-system impacts. Significant issues to be addressed are: (1) the aggregation of data collection required for each level of decision-making, (2) the range of environmental effects needed to be analyzed at each level, (3) the uncertainty present at different levels of data aggregation, (4) the influence of site-specific (fate and transport) factors, and (5) the transformation of environmental information into metrics usable in detailed design and planning of products and processes. Case studies in the fabrication of metal parts and printed circuit boards are presented.