|Del Grosso, S - COLORADO STATE UNIVERSITY|
|Parton, W - COLORADO STATE UNIVERSITY|
Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 19, 2004
Publication Date: August 1, 2004
Citation: Adler, P.R., Del Grosso, S.J., Parton, W.J. 2004. National assessment of greenhouse gas emissions from bioenergy cropping systems using DAYCENT [abstract]. Ecological Society of America Abstracts. p. 7. 2004 CDROM Technical Abstract: Reducing the global warming potential (GWP) of energy use is a major factor driving interest in biofuels. The main components of GWP from crop production are N2O emissions, soil CO2 fluxes, CO2 emissions associated with agricultural inputs and farm equipment operation, and CH4 fluxes. Currently, annually cropped corn and soybeans are used to produce ethanol and biodiesel, respectively. Perennial crops with potential for use in the future are alfalfa, switchgrass, and short-rotation trees such as willow and hybrid poplar. These cropping systems vary in GWP due to the quantity and quality of C added to the soil and N use efficiency. The net GWP of these different bioenergy cropping systems are uncertain, especially at large scales. National scale simulations of net greenhouse gas emissions using DAYCENT were performed. The model was run at the county level and results were aggregated to the state level and summed to obtain national totals. Total emissions of CO2, N2O, and CH4 were converted to a common unit of CO2-C equivalents and net GWP calculated for each cropping system. The lower energy requirements from agricultural inputs and farm equipment operations, and lower fertilizer N applications and higher C inputs into the soil of perennial crops should result in lower GWP than annual crops. Trees have lower C inputs into the soil than switchgrass but C harvests may be higher with trees. Nitrogen fixing crops such as soybean and alfalfa have lower energy inputs since N fertilizer is not added, but N2O emissions may not decrease because the amounts of N added are similar. Increased N use efficiency is critical to reducing N2O emissions.