(634b) Effects Of Nitrogen Fertilizer On The Ethanol Fuel System
- Conference: AIChE Annual Meeting
- Year: 2007
- Proceeding: 2007 Annual Meeting
- Group: Sustainable Biorefineries
- Time: Thursday, November 8, 2007 - 3:55pm-4:20pm
Ethanol is used as a substitute transportation fuel for gasoline in two ways: E10 (a mixture of 10 % ethanol and 90 % gasoline by volume) and E85 (a mixture of 85 % ethanol and 15 % gasoline by volume). Most ethanol in the United States is derived from corn grain via dry milling or wet milling, and its annual production capacity is about 22 million m3. More ethanol plants, which in total would add up to another 24 million m3 yr-1, are under construction. Using ethanol derived from corn grain as liquid fuel would reduce nonrenewable energy and greenhouse gas emissions, but would increase acidification, eutrophication and photochemical smog, compared to using gasoline as liquid fuel, if current practices remain unchanged (primarily agricultural practices). The dominant factor influencing greenhouse gas emissions, acidification, eutrophication and photochemical smog formation is soil related nitrogen losses (e.g., N2O, NOx and NO3-). Nitrogen fertilizer applied during corn cultivation is probably the primary source of soil related nitrogen losses. A higher application rate of nitrogen fertilizer would produce more corn grain. However, more soil related nitrogen emissions would also be produced at a higher application rate of nitrogen fertilizer. The agricultural processes also account for 27 ? 44 % of the total energy consumption in producing biobased products. This study investigates the effects of nitrogen fertilizer application on the bioethanol fuel system. To estimate local soil carbon and nitrogen dynamics in biomass cultivation, this study uses the DAYCENT model, which is the daily time step version of the CENTURY model, a multicompartmental ecosystem model. The system boundary includes corn production, transportation of corn to a dry mill, the dry mill processing steps, transportation of ethanol to users, ethanol fueled vehicle operation, and upstream processes. The allocation procedures for external functions are done by the system expansion approach. To compare the environmental performance between bioethanol fuel and gasoline fuel, gasoline fueled vehicle operation is included in the system boundary. Planting winter cover crops after harvest is one possible way to reduce nitrogen losses from soil because winter cover crops serve as a nitrogen scavenger. We also investigate the effects of planting winter cover crops on the bioethanol fuel system. The potential impact categories considered here are nonrenewable energy consumption, greenhouse gas emissions, photochemical smog, acidification, and eutrophication. Environmental impacts are estimated by characterization factors given by the United States Environmental Protection Agency (EPA-TRACI).