Advances in Applied Agricultural Sciences 03 (2015), 05: 08-21
Handling of co-products in life cycle analysis in an evolving co-product market: A case study with corn stover removal
Steffen Mueller 1, Stefan Unnasch 2, Wallace E. Tyner *3, Jennifer Pont 2 and Jane M-F Johnson 4
1 University of Illinois at Chicago, Energy Resources Center, 1309 South Halsted, Chicago, Illinois 60607. E-mail: [email protected] 2 Life Cycle Associates, 884 Portola Road, Portola Valley, California 94028. E-Mail: [email protected], [email protected] 3 James and Lois Ackerman Professor, Purdue University, Department of Agricultural Economics, 403 West State Street, West Lafayette, IN 47907-2056. 4 USDA-Agricultural Research Service, North Central Soil Conservation Research Laboratory, 803 Iowa Ave. Morris, MN 56267. E-mail: [email protected]
Corn stover (cobs, stalks, and leaves) can be used as a cellulosic feedstock for ethanol or as a replacement for corn and hay or corn silage in animal feed. Corn stover is an important part of the life cycle of corn, either as fuel or as animal feed, but most LCA models treat them separately from grain ethanol. Life cycle greenhouse gas emissions (GHGs) for corn-based biofuel pathways were estimated in order to explore the life cycle boundary impacts of using treated corn stover (TSF) as cattle feed. Depending on the life cycle modeling boundaries, the treatment of these emissions credits and debits results in significantly different GHG estimates. Our estimate for the carbon intensity of corn grain ethanol alone is 62 g/MJ. However, corn grain ethanol combined with TSF or corn stover ethanol reduces the composite numbers to 56 and 52 g/MJ respectively, both considerably lower than corn ethanol alone. As cellulosic ethanol from stover and TSF become more common, the current LCA procedures for corn ethanol will have to be modified, and we illustrate how this can be done.