(595a) Life Cycle Assessment of Integrated Biorefinery: Corn Grain, Corn Stover and Switchgrass

Lignocellulosic biomass (e.g., crop residues, energy crops and etc.) is a potential raw material for lignocellulose-based ethanol production, while corn grain is currently the primary feedstock for ethanol production in the United States. Large scale technologies for lignocellulosic feedstock will likely be available in the near future.

An integrated biorefinery is defined as a biorefinery in which both lignocellulosic raw materials and starch raw materials are used to produce biobased products. One merit of integrated biorefinery is that the starch based biorefining processes can utilize surplus energy from the lignocellulosic biorefinery process, in which fermentation residues and biogas from wastewater treatment are used as fuel sources to generate both electricity and steam. (These data are derived from our collaborates on the Role of Biomass in America's Energy Future project.)

This is a life cycle assessment study on ethanol production in an integrated biorefinery. The feedstock is corn grain as starch based biomass, and corn stover or swtichgrass as lignocellulosic biomass. The system boundary includes biomass production, transportation of biomass to an integrated biorefinery, integrated biorefinery processes, transportation of ethanol to users, and ethanol fueled vehicle operation. Ethanol is used as a liquid fuel in a compact passenger vehicle in the form of E10 (a mixture of 10 % ethanol and 90 % gasoline by volume). The Ammonia fiber explosion process (AFEX) is used to pretreat corn stover and swtichgrass, and a dry milling process is used as the starch based biorefinery. The allocation procedures for external functions are done by the system expansion approach. Thus, the system boundary is expanded to include the alternative product systems (e.g., gasoline fueled vehicle operation, etc.). The potential impact categories considered here are nonrenewable energy consumption, fossil fuel use (e.g., coal, crude oil and natural gas), climate change, photochemical smog, acidification, and eutrophication. Environmental impacts are estimated by characterization factors given by the United States Environmental Protection Agency (EPA-TRACI).