`Co-product allocation in life cycle assessment– a case study,` presented at the 2009 air & waste management association`s annual conference



As the interest toward industrial sustainable practice grows; companies are increasingly turningto life cycle assessments (LCA) as a metric to measure sustainability impacts by analyzing theenvironmental and energy burden of their products and services. LCA is a method of measuringthese impacts through the raw material procurement, production, usage and disposal stages of aproducts life cycle.1 LCA for example can be used to measure a products carbon foot print ordetermine the viability of alternative fuels. The outcome of LCA’s can vary greatly dependingon the assumptions made in the assessment; specifically for processes which produce multipleproducts. Allocation is a method of distributing the production energy consumption andenvironmental impacts between products and co-products through the determination of a coproductcredit. This credit is utilized in and can have a significant impact on the overall LCAresult.

LCA standards call for avoiding allocation when possible by including within the boundary of theassessment production processes for materials that are replaced by co-products.2 A commonapproach in LCA and net energy analysis, known as the “system expansion' method (also knowas the “substitution”, “displacement”, or “replacement” allocation method), credits input energyto co-products associated with the products displaced in the market. This method uses the lifecycle energy required to produce the material that is displaced by the co-product, attributing thisenergy to the co-product in subsequent stages of an energy and environmental analysis.3 The U.S.EPA has stated that the displacement method is the preferred allocation method for life-cycleenergy and GHG analyses in its analysis of the Renewable Fuel Standard Program.

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