Convergence of Agriculture and Energy: II. Producing Cellulosic Biomass for Biofuels

Global energy demand is increasing as known global petroleum supplies are decreas¬ing. Calls to supplement or replace the current fossil-based energy system with new, envi¬ronmentally and economically sustainable strategies continue to increase, especially in light of more expensive traditional energy sources. Various governmental agencies and working groups have set aggressive targets and timelines for decreasing fossil fuel consumption by substituting bio-based energy (Bush 2007; Foust et al. 2007; Perlack et al. 2005; Smith et al. 2004). The alignment and continuity of these goals is illustrated in Figure 1. Current biofuel production in the United States relies primarily on corn grain conver¬sion to ethanol, but future systems are expected to depend more intensively on plant biomass than on grain as a feedstock for production of ethanol and other biofuels. In addition, current cropping systems generally are designed to optimize grain production and are not designed to harvest all the aboveground portion of the plant for cellulose-containing biomass. Significant, immediate national investments are needed, along with changes in policy, to address chal¬lenges limiting the sustainable production and efficient use of cellulosic biomass as a fuel feedstock to meet anticipated U.S. demand. The Bush Administration outlined a portfolio of recommended technologies, pro¬cesses, and practices for bio-based energy production that targets improved rates of feedstock conversion and greater efficiency in energy use. The plan also states that a significant portion of the nation’s 2017 energy supply, especially transportation fuel, will come from conversion of biomass feedstock to liquid fuels. Considering just the biomass-derived fuels contribution, roughly 250 million tons or more of grain and cellulosic biomass per year will be needed to reach the 10-year goal, and 650 to 700 million tons per year of biomass to reach the 2025 goal (Figure 1).