Handling of co-products in life cycle analysis in an evolving co-product market: A case study with corn stover removal

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.

کلیدواژه ها:

Corn Ethanol ، Greenhouse Gas Emissions (GHG) ، Life Cycle analysis ، system boundaries ، Induced land use change (LUC) ، Corn stover feed