(618b) Indirect Land Use Changes in Ethanol Fuel Derived From Corn Grain and Corn Stover

Current practices for estimating indirect land use changes in ethanol fuel derived from a corn field are retrospective and may not reflect future technologies. Current practices assume that only corn grain from the corn field is involved in ethanol fuel production. Utilization of corn stover is totally ignored in the analysis. This assumption reflects what we have done up to the present. In the near future corn stover can play an important role in cellulosic ethanol fuel production, and products of a corn field devoted to producing ethanol fuel may be involve starch-based or both starch-based and cellulosic ethanol production systems. Although production of corn grain is only one possible driving force for converting natural ecosystems to croplands, the corn field is a joint multi-output process, and production processes for corn grain and corn stover can not be separated. Therefore, both starch-based and cellulosic ethanol fuel systems are included in the indirect land use change calculations. Otherwise, an appropriate allocation between corn grain and corn stover is required.

We estimate greenhouse gas profiles of ethanol fuel from corn fields in Corn Belt states including indirect land use changes when corn stover is utilized in cellulosic ethanol production. We assume that land conversions occur in Corn Belt states as well. Starch-based ethanol is produced via dry milling and cellulosic ethanol is produced through a cellulosic biorefinery with ammonia fiber expansion (AFEX) pretrement. The functional unit in the greenhouse gas analysis is one-mile driven by an ethanol flexible-fuel vehicle regardless of feedstock. The system boundary includes the corn field, dry milling, cellulosic biorefinery, transportation (e.g., ethanol, corn grain, corn stover, etc.), gasoline production, and ethanol flexible-fuel vehicle operation. Greenhouse gas emissions associated with a gasoline fueled vehicle are also estimated for comparisons. Greenhouse gas emissions associated with land use changes (i.e., direct and indirect) are measured as changes in soil organic carbon levels. In the cellulosic biorefinery, fermentation residues and biogas from wastewater facility are used as energy sources to generate electricity and steam, which are used within the cellulosic biorefinery. Surplus electricity is exported to displace electricity generated from coal-fired power plants.