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ALLOCATING ENVIRONMENTAL BURDENS ACROSS CO-PRODUCTS TO CREATE A LIFE CYCLE INVENTORY: IS THERE A BEST WAY?
Citation:
CURRAN, MARY ANN. ALLOCATING ENVIRONMENTAL BURDENS ACROSS CO-PRODUCTS TO CREATE A LIFE CYCLE INVENTORY: IS THERE A BEST WAY? Presented at University of Cincinnati, Department of Chemical Engineering Seminar Series, Cincinnati, OH, January 27, 2006.
Impact/Purpose:
To inform the public
Description:
Allocation methodology for creating life cycle inventories is frequently addressed, discussed and debated, yet the methodology continues to be in a state of flux. ISO 14041 puts perspective on the issues but its one-size fits all framework is being challenged. It is clear that although the ISO standard identifies a general methodological framework for allocation, it does not provide specific guidance on when and how to apply the steps that are outlined in 14041. There is overall agreement that a system expansion approach is preferable not only because it avoids the allocation issue but also because it allows the modeler to assign credits for avoided environmental burdens due to product displacement. A drawback is the need to collect more data to complete the model. Also, larger systems run the risk of being less transparent. A recent literature search revealed many publications on allocation that provided either generic guidance (e.g., EPA, GREET, NREL, CML, and EcoInvent) for conducting allocation or demonstrated how allocation can be done in specific case studies (ammonia, borax, ethanol, petroleum refining, and combined heat and power). The generic guidance documents included mass, energy, economic basis for allocation as well as flexibility for the user to select an allocation basis. A number of allocation approaches have been propsed based on the notion of modeling reality. Other allocation methods are based on the argument of fairness, or accountability, especially in open loop recycling systems. What continues to be lacking is a unifying theory that can explain what allocation key is justifiable in any given situation. A frequently recurring theme is the idea that methodological choices in LCA depend on the goal of the study. However, guidance that matches goal with approach is still lacking. It would be useful to develop the range of allocation approaches matched with use in different applications. They should be tested and demonstrated in various case studies and further discussed within the LCA community. The case studies found in the literature search demonstrate how variations in allocation approaches can alter the results in the inventory. This is not entirely unexpected and is somewhat predictable. The question should not be if the results vary but by how much. This presentation will explore potential future studies to investigate the overall impact of various allocation schemes on the entire system, instead of only focusing on the effects around individual processes. The important consideration is the impact that any given choice for allocation has on the decision making process. This aspect was not seen in the literature that was reviewed. Wide ranges of variability exist in any data that represent an average technology or process mix. This variablity may overshadow any differences caused by various allocation techniques.