Land-Use Credits to Corn Ethanol: Accounting for Distillers Dried Grains with Solubles as a Feed Substitute in Swine Rations
Jacinto F. Fabiosa
April 2009 [09-WP 489]
Fabiosa, J.F. 2009. "Land-Use Credits to Corn Ethanol: Accounting for Distillers Dried Grains with Solubles as a Feed Substitute in Swine Rations." Working paper 09-WP 489. Center for Agricultural and Rural Development, Iowa State University.
Many studies on the impact of biofuels on greenhouse gas emissions do not consider indirect land-use change and land use avoided because of co-products utilization. This paper provides estimates of the land-use credit for corn ethanol when its by-product—distillers dried grains with solubles (DDGS)—is used in swine feed rations to substitute for corn and soymeal. The range of estimates used here covers the land-use credit used in the literature. Moreover, this study departs from earlier studies because feed rations from a least-cost optimization are used rather than rations from feeding trials, and DDGS nutrient profile variability is fully accounted for. As a result, displacement rates and the land-use credit can be better characterized using a distribution rather than a single point estimate. The land-use credit for corn ethanol for DDGS used in swine feed rations ranges from -0.367 to -0.596 hectares, whereby substitution for corn in the feed ration accounts for 56.09% and soymeal substitution contributes 48.46%. Variability of the land-use credit is contributed more by the variability of land use from the substitution of soymeal than that of corn.
Finally, when feed compounders discount the DDGS nutrient profile to ensure they are at or above any realized nutrient profile 90% of the time, the land-use credit for corn ethanol declines by 8.47% for DDGS in a swine feed ration.
Keywords: biofuel, DDGS quality, displacement rate, greenhouse gas accounting, land-use credit, optimal, stochastic LP, swine grower-finisher optimal feed ration.