Publication DetailsTitle : Soil Carbon Changes for Bioenergy Crops
Publication Date : September 01, 2002
Authors : D. Andress
Abstract : This report details the characterization of the soil carbon sequestration for three bioenergy crops (switchgrass, poplars, and willows) for use in the GREET model. In addition, this report documents methodologies, key issues, and data needs in addressing soil carbon from land use changes caused by biofuel production in the context of a life-cycle analysis. Bioenergy crops, which displace fossil fuels when used to produce ethanol, bio-based products, and/or electricity, have the potential to further reduce atmospheric carbon levels by building up soil carbon levels, especially when planted on lands where these levels have been reduced by intensive tillage. A three-step process is used to conduct this study. First, the results of an economic analysis were used to determine crop yields, geographic locations for bioenergy crop production and land use changes. Next, a soil carbon model was used to estimate regional soil carbon changes on a per hectare basis over time, based on the regional yield and land use data calculated from the economic analysis. Finally, the data from the first two steps were combined to calculate the soil changes per unit of biomass as a function of time. In addition, the regional data was aggregated to make a national estimate. These results were applied to the methodology used in GREET to assign carbon changes to a unit of biomass (grams of carbon dioxide per dry ton of biomass) by calculating the total soil carbon changes over the life of the bioenergy crop farm and divide the resulting value by the total biomass production during that period.