© Copyright 2001 by the Massachusetts Institute of Technology and Yale University Volume 4, Number 3 ❙ SYSTEMS MODELING AND THE ENVIRONMENT Journal of Industrial Ecology 7 Extending the Boundaries of Life-Cycle Assessment through Environmental Economic Input-Output Models H. Scott Matthews and Mitchell J. Small Carnegie Mellon University Pittsburgh, PA, USA L ife-cycle assessment (LCA) is a cornerstone of current practice in industrial ecology, linking the product life cycle, from design to dis- position, with the environmental impacts gener- ated at each stage. It is one of the ways that industrial ecology brings a systems approach to environmental analysis. LCA aids environmen- tal improvement by revealing the complete im- pact of a product, rather than just the emissions generated in the usual course of production by the manufacturer. Manufac- turers, service providers, and government agencies can use these methods to consider the total impact of their procure- ment and business activities, and to tailor them to be more environmentally friendly. A number of different approaches to LCA have been developed, with different focus, time, and resource requirements. Key among these are: • full or exhaustive LCA, • streamlined LCA, and • economic input-output-LCA (EIO-LCA). We describe each briefly, with further discussion of the EIO-LCA approach as an easy-to-use methodology able to expand the traditional boundaries of an LCA. An exhaustive LCA begins with an inven- tory that quantifies the inputs and outputs (ma- terials and energy use, environmental discharges, etc.) associated with each stage of the life cycle. In addition, practitioners often at- tempt to assess the effects of the estimated in- ventory, creating a life-cycle impact assessment (LCIA). This is done by characterizing and ranking the expected effects of releasing the inventory into the environment. The data burden of a conventional LCI or LCA can be substantial, due to logistical as well as propri- etary barriers. If new data are needed, then existing processes must be measured and analyzed to determine the quantities of inputs and releases for each life-cycle stage. Existing estimates may be used, but need to be relevant and specific to the par- ticular application to be of use in such a setting. For example, to yield accurate results, the inven- tory of electricity effects for a particular process- ing plant must reflect the local mix of electricity purchased. Getting such data can be difficult, requiring specific fuel and technology assump- tions. In the end, the success or failure of any LCA depends greatly on the boundary assump- tions, data quality, and the level of economic re- sources available for determining site-specific resource use and pollutant-emission factors. Many conventional LCA software tools exist to aid decision-makers in performing life-cycle in- An EIO-LCA model . . . provides the complete sup- ply chain of economic activ- ity needed to manufacture any good or service in the economy.