A potential optimal strategy for producing biofuels in the United States could be to locate thermochemical conversion plants that use coal and biomass as a combined feedstock in regions where biomass is abundant and locate biochemical conversion plants in regions where biomass is less concentrated. Thermochemical plants require larger capital investment per barrel of product than do biochemical conversion plants and thus benefit to a greater extent from economies of scale. This strategy could maximize the use of cellulosic biomass and minimize the costs of fuel products.
The U.S. Department of Energy and the U.S. Department of Agriculture should determine the spatial distribution of potential U.S. biomass supply to provide better information on the potential size, location, and costs of conversion plants. The information would allow determination of the optimal size of conversion plants for particular locations in relation to the road network and the costs and greenhouse gas effects of feedstock transport. The information should also be combined with the logistics of coal delivery to such plants to develop an optimal strategy for using U.S. biomass and coal resources for producing sustainable biofuels.
Because ethanol cannot be transported in pipelines used for petroleum transport, an expanded infrastructure will be required to replace gasoline with a larger proportion of ethanol produced via biochemical conversion. Ethanol is currently transported by rail or barges and not by pipelines, because it is corrosive in the existing infrastructure and can damage seals, gaskets, and other equipment and induce stress-corrosion cracking in high-stress areas. If ethanol is to be used in fuel at concentrations higher than 20 percent (for example, E85, which is a blend of 85 percent ethanol and 15 percent gasoline), the number of refueling stations will have to be increased to support alternative-fuel vehicles. The transport and distribution of synthetic diesel and gasoline produced via thermochemical conversion will be less challenging because they are compatible with the existing infrastructure for petroleum-based fuels.