The process combines the cellulose hydrolysis and fermentation steps in one vessel to produce high yields of ethanol. Continued improvements in such key technical areas as pretreatment of feedstocks, fermentation micro-organisms, and cellulase enzymes will make biochemical conversion of biomass to ethanol a more efficient and economical route to renewable fuels production. Utilization Service stations throughout the United States, especially in carbon monoxide nonattainment areas, are distributing ethanol blends. However, ethanol blends can be found in other areas of the country as well, and have been used for many years to boost gasoline's octane. Although there are only a few thousand such vehicles in operation, the role of ethanol is expected to grow as federal, state, municipal, and private fleet operators seek to comply with the alternative fuel requirements of the Energy Policy Act of 1992 and the Clean Air Act Amendments of 1990.
Ethanol can also help lower mobile-source carbon monoxide emissions.
Neat ethanol is relatively low in toxicity, water soluble, and biodegradable, making the consequences of large fuel spills less environmentally threatening. Use of ethanol does pose some difficulties that are currently being addressed by researchers. Nonetheless, slightly larger fuel tanks would be needed if vehicles are to travel equal distances to gasoline on one fill-up of pure ethanol. The range of vehicles fueled with low-ethanol blends such as gasohol is very close to that of vehicles running on regular gasoline. Pure ethanol's low volatility is beneficial in reducing some emissions but can cause starting problems in cold weather.