How ethanol is made
Fuel ethanol is made by fermenting corn or sugarcane, the same way beer is, just in far bigger tanks.
- stations
- 6
- things upstream
- 11
- raw sources
- 6
- steps from the ground
- 4
The short version
Fuel ethanol is made by milling corn or crushing sugarcane, cooking the starch and sugar into a sweet mash, and letting yeast ferment it into a weak alcohol beer. Distillation concentrates the alcohol, and a dehydration step removes the last water. A small share is made from ethylene instead.
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Mill the grain or crush the cane
Corn kernels are ground to flour in hammer mills, or sugarcane is crushed to squeeze out its juice. Either way, the aim is to get at the sugars.
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Cook it into a sweet mash
Corn flour is mixed with water and cooked, and enzymes chop its starch into simple sugars. Cane juice already contains sugar, so it skips this step.
Goes in -
Ferment with yeast
Yeast is added to the mash in huge tanks. It eats the sugar and produces alcohol and carbon dioxide, and the result is a weak alcohol mixture called beer.
Goes in -
Distill off the alcohol
The beer is heated in tall columns, where ethanol vaporizes before the water. Ethanol and water form a mixture that cannot be separated completely by simple distillation.
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Dry it to fuel grade
Molecular sieve beds soak up the remaining water and leave nearly pure ethanol. Fuel plants add a small amount of gasoline to make it undrinkable.
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Synthesize it from ethylene
A smaller share of ethanol is made by reacting ethylene with water over a catalyst. It starts from petrochemicals and skips the crops.
Goes in
Worth repeating
- World fuel ethanol production reached 120 gigaliters in 2024.
- Brazil made it mandatory to blend ethanol with gasoline in 1976, and the first production car running entirely on ethanol was the Fiat 147, introduced in Brazil in 1978.
- A 70% ethanol solution kills microbes better than pure ethanol, because it relies on water to work.
Back to the ground
Follow every input upstream and ethanol starts as these 6 raw sources.
Everything it is made of See it on the map
Open the whole family tree
Where it comes from
- United States51% of world fuel ethanol
- Brazil30% of world fuel ethanol
Share of world fuel ethanol production in 2024.
Where it goes next
Ethanol feeds 15 lines directly and reaches 169 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How ethanol is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/ethanol