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Ethanol, also known as ethyl alcohol or grain alcohol, can be used either as an alternative fuel or as an octane-boosting, pollution-reducing additive to gasoline. The US ethanol industry is expected to produce over 2.81 billion gallons in 2003, up 32% from 2002's record annual production of 2.13 billion gallons (Renewable Fuels Association Ethanol Industry Outlook 2004) (PDF 827 KB) Download Acrobat Reader. Although this number is small when compared with fossil fuel consumption for transportation, as individual states continue to ban the use of MTBE (Methyl Tertiary Butyl Ether) and with the possibility of a Federal ban, ethanol consumption is due for a significant boost. Because of the increased demand on ethanol as a gasoline additive, efforts to increase supplies are necessary in order to meet the increase in demand. Currently, 72 ethanol plants in 19 states have the capacity to produce more than 3 billion gallons annually and an additional 15 plants are under construction to add over 550 million gallons of capacity in 2004 (RFA EIO 2004).
There are four basic steps in converting biomass to bioethanol:
- Producing biomass results in the fixing of atmospheric carbon dioxide into organic carbon.
- Converting this biomass to a useable fermentation feedstock (typically some form of sugar) can be achieved using a variety of different process technologies. These processes for fermentation feedstock production constitute the critical differences among all of the bioethanol technology options.
- Fermenting the biomass intermediates using biocatalysts (microorganisms including yeast and bacteria) to produce ethanol in a relatively dilute aqueous solution is probably the oldest form of biotechnology developed by humankind.
- Processing the fermentation product yields fuel-grade ethanol and byproducts that can be used to produce other fuels, chemicals, heat and/or electricity.
Corn and other starches and sugars are only a small fraction of biomass that can be used to make ethanol. Advanced Bioethanol Technology allows fuel ethanol to be made from cellulosic (plant fiber) biomass, such as agricultural forestry residues, industrial waste, material in municipal solid waste, trees, and grasses. Cellulose and hemicellulose, the two main components of plants-and the ones that give plants their structure-are also made of sugars, but those sugars are tied together in long chains. Advanced bioethanol technology can break those chains down into their component sugars and then ferment them to make ethanol. This technology turns ordinary low-value plant materials such as corn stalks, sawdust, or waste paper into fuel ethanol. Not quite lead into gold, but maybe more valuable for the U.S. economy, for cutting air pollution, and for reducing dependence on foreign oil. To help improve this technology and ready it for commercial operation, the DOE researchers and their industrial partners use the DOE Bioethanol Pilot Plant (PDF 355 KB) Download Acrobat Reader, a fully integrated biomass-to-ethanol production facility that can turn as much as one ton per day of corn stalks or other plant material into transportation fuels.
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