Bioethanol is made by fermenting a sugar or starch source with yeast and distilling the wash to 90% or more ethanol; the carrier gives roughly 350-400 litres per tonne of corn grain. The product is fuel, not drink: mark it, denature it with something that smells foul and burns, such as petrol, and do not add methanol, which is how poisoning outbreaks happen. Spend food crops on fuel only from a surplus.
Part of Organic Chemistry
Producing fuel-grade ethanol by fermentation and distillation, with the yield arithmetic and the safety position on methanol.
Five Stages From Grain To Fuel
The carrier’s route is: mash grain or fruit (corn, wheat, potatoes, sugar cane, fruit pulp); add water and heat to convert starch to sugar if using grain; cool to 25-30 °C and add yeast; ferment 5-14 days until bubbling stops; distil to 90% or more ethanol; denature. The detailed pages are Ethanol Fuel Production, Grain Mash, Fermentation, Achieving 90%+ Purity and Dehydration to Fuel Grade. The fermentation chemistry is in Fermentation Products and the still in Distillation Apparatus.
Methanol: The Corpus Position, Not Reopened Here
For fuel, methanol matters to people, not to the engine, because methanol burns. The authoritative page is Methanol Hazards; it is linked rather than restated. Three points to carry: the cut at the start of a run is a flavour step and does not make a distillate safe, the feedstock is the control, and no volume rule makes a distillate safe to drink. Fuel alcohol is for engines.
The Carrier’s Denaturing Step Is Corrected Here
The carrier’s last step says to denature by adding 5% methanol or gasoline. Do not use methanol. The documented methanol outbreaks come from methanol being added to drink, and a fuel store with methanol in it is exactly the material that ends up in a bottle. The methanol page recommends something foul that also burns, such as petrol or kerosene, plus a label reading that the contents are fuel, poison and not for drinking. Treat this as the safer practice; the carrier’s text is not otherwise altered.
What You Need
- Feedstock: sugar or starch crops (Feedstocks).
- Yeast and fermenting vessels with vents (Fermentation Vessel Design).
- A still, with a reflux column for fuel strength (Reflux Column Design).
- Denaturant and clear labels, and a store separate from food and drink.
Worked Example: Is 350-400 Litres Per Tonne Reasonable?
Use hypothetical starch content of 70% by weight in corn (an illustrative figure, not a corpus value) and rounded atomic masses.
- Starch in 1,000 kg of corn: 1,000 × 0.70 = 700 kg.
- Starch gains water on conversion to glucose: 180 ÷ 162 = 1.111, so 700 × 1.111 = 778 kg of glucose.
- Ethanol at the theoretical 0.511 kg per kg of glucose (worked in Fermentation Products): 778 × 0.511 = 397 kg.
- Ethanol density about 0.789 kg per litre (recalled): 397 ÷ 0.789 = 503 litres.
The carrier’s 350-400 litres is 350 ÷ 503 = 70% to 400 ÷ 503 = 80% of that ceiling, which is a plausible practical range. The ceiling depends on the assumed starch content, so the check is rough.
Common Mistakes
- Drinking the product or letting others do so.
- Denaturing with methanol.
- Diverting food crops to fuel. The carrier says to do so only with a substantial food surplus.
- Fermenting in a sealed vessel.
Safety
Fuel ethanol is flammable and poisonous, and its vapour is invisible
Run the still outdoors, away from flames; ethanol vapour ignites at ordinary temperatures (see Fire Safety), and never test with a flame. Fermentation gives off CO2 that pools in low spaces. Fuel alcohol must be labelled and denatured, kept apart from drink, and never given to anyone to drink.
What’s Next
- Learn next: Charcoal Chemistry — a solid fuel and its by-products
- Combine with: Biodiesel — the liquid fuel for diesel engines