Wednesday, May 7, 2008 - 10:00 AM
10-04

Life Cycle Assessment of Polyhydroxyalkanoates (PHA)

Seungdo Kim, Chemical Engineering and Material Science, Michigan State University, 2527 Engineering Building, East Lansing, MI 48824-1226 and Bruce E. Dale, Department of Chemical Engineering and Material Science, Michigan State University, 3247 Engineering, East Lansing, MI 48824.

We have performed a life cycle assessment on the polyhydroxyalkanoates (PHA) product system to estimate the environmental performance of PHA derived from corn grain, particularly renewable energy consumption and greenhouse gas emissions. The system boundary includes processes from agricultural production to the PHA fermentation and recovery process. Site-specific process information on the corn wet milling, PHA fermentation and recovery processes was obtained from Metabolix and ADM. Most of energy used in the corn wet milling and PHA fermentation and recovery processes is generated from a cogeneration power plant in which corn stover is burned to generate electricity and steam. Off-site power used in the PHA fermentation and recovery process is purchased from a wind power plant. County level agricultural information is used in estimating the environmental burdens associated with both corn grain and corn stover production. Corn farming counties are specified. Four counties in Iowa (Boone, Cedar, Clinton and Jones counties) supply corn grain to a wet milling plant located in Clinton County. County level soil organic carbon dynamics, nitrate losses due to leaching, and nitrogen oxide and nitrous oxide emissions are predicted by the DAYCENT model. The environmental burdens associated with products in multi-output processes are estimated by the system expansion approach, in which alternative product systems for co-products are introduced. Scenario and sensitivity analyses are done to determine the environmental effects of the following aspects on the overall renewable energy consumption and greenhouse gas emissions: tillage practice, winter cover crop practices and allocation procedures.

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