Changes

==Processes==

==Processes==

Ethanol for use in [[alcoholic beverage]]s, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of [[yeast]] (most importantly, ''[[Saccharomyces cerevisiae]]'') [[metabolism|metabolize]] [[saccharide|sugar]] in the absence of [[oxygen]], they produce ethanol and [[carbon dioxide]].  The overall chemical reaction conducted by the yeast may be represented by the chemical equation

Ethanol for use in [[alcoholic beverage]]s, and the vast majority of ethanol for use as fuel, is produced by fermentation: when certain species of [[yeast]] (most importantly, ''[[Saccharomyces cerevisiae]]'') [[metabolism|metabolize]] [[sugar]] in the absence of [[oxygen]], they produce ethanol and [[carbon dioxide]].  The overall chemical reaction conducted by the yeast may be represented by the chemical equation

: [[glucose|C₆H₁₂O₆]] → 2 CH₃CH₂OH + 2 [[carbon dioxide|CO₂]]

: [[glucose|C₆H₁₂O₆]] → 2 CH₃CH₂OH + 2 [[carbon dioxide|CO₂]]

Ethanol is also produced by the catalytic hydration of ethylene. Crude oil is catalytically 'cracked' to ethylene and the ethylene is chemically combined with water at high temperatures with an acid catalyst. This process is actually cheaper than fermentation,

Ethanol is also produced by the catalytic hydration of ethylene. Crude oil is catalytically 'cracked' to ethylene and the ethylene is chemically combined with water at high temperatures with an acid catalyst. This process is actually cheaper than fermentation,

but has become less common as ethanol produced from corn is heavily subsidized by the federal government.

but has become less common as ethanol produced from corn is heavily subsidized by the federal government.

==Co-products==

==Co-products==