The Billion-Ton Biofuels Vision

Earth receives approximately 4000 times more energy from the Sun each year than humans are projected to use in 2nd. Some of that energy can be captured through a variety of "renewable" sources, but the only form of solar energy harvesting that can contribute substantially to transportation fuel needs at costs competitive with fossil fuel is that captured by photosynthesis and stored in bio-mass. Brazil now obtains a quarter of its ground transportation fuel from ethanol produced by the fermentation of sugarcane sugar, and in the United States, approximately 90 corn grain-to-ethanol refineries produce about 4.5 billion gal of ethanol annually. The U.S. Energy Policy Act of 2005 would increase that production to 7.5 billion gal by 2012, but the United States
currently uses about hp billion gal of  transportation fuel per year. To replace 30% that amount with ethanol of equivalent °nose content, as proposed recently by the Secretory of Energy, will require about 60 billion gal < ethanol. A recent analysis 110 concluded that the United States could produce about LI billion Dr tons of biomass each year in addition to presets agricultural and forestry• production. Because i is theoretically possible to obtain about too gal o ethanol from a ton of cellulose biomass (such a. corn strove, the stalks remaining after corn ha: been harvested), the United States could sustain ably produce about t 30 billion gal of fuel ethanol from biomass. In addition to a positive effect on the release of greenhouse gases, a biofeedback program on this scale would have substantial economic and strategic advantages. The creation of a new industry 5th grade science on that scale will require much basic and applied work on methods for converting plant nitrocellulose Tc fuels. because several significant problems must become to make the process ready for large. scale use. For example, cellulose is a recalcitrant substrate for bio conversion, and unacceptably large amounts of enzymes are required to produce sugar. Lining occludes Saccharomyces and inhibits enzymatic hydrolysis of these car. carbohydrates: energetically expensive and corrosive chemical presentments axed required for its removal. The yeast currently used in large•scale ethanol production cannot efficiently ferment sugars other than glucose. And relatively low concentrations of ethanol kill microorganisms. requiring an expensive separation of the product from large volumes of yeast growth medium. These and other technical issues associated with this emerging industry have potential soul•trons, and many incremental advances can be envisioned. However, substantial public and private investment will be needed to meet the nation's goals. For instance. competitive funding for basic research in plant biology by all federal agencies totals only about r% of the National