Fuel Source

Ethanol, or grain alcohol, is produced by fermenting biomass, commonly corn (though other, lower-value feedstocks have been tested in an effort to reduce costs, like brewery waste and cheese-factory effluent–blecch!). It is thus inherently a renewable resource, and contributes nothing in itself to greenhouse-gas loading of the atmosphere (and with efficient modern farming techniques, there's still an improvement even when you add in the petroleum-based fuel burned to plow the fields, make the fertilizer, etc.). As an alternative motor vehicle fuel, it is usually blended in a mixture of 85% ethanol, 15% unleaded gasoline, whence E85. (It is also used in up to 10% blends with gasoline (gasohol) to oxygenate the gasoline, and this mixture can be used by most modern gasoline vehicles.)