Ethanol Fuel Production

Ethanol (ethyl alcohol, C₂H₅OH) is a liquid fuel that can replace gasoline in spark-ignition engines. It is made by fermenting sugars or starches with yeast, then distilling the result to concentrate the alcohol. Humans have been fermenting alcohol for 10,000+ years — the same process that makes beer and wine makes engine fuel. The difference is concentration: drinking alcohol is 5-40% ethanol; engine fuel needs 85-95%+.

Feedstocks

Sugar Crops

The easiest feedstocks — sugars ferment directly without pre-processing:

• Fruit (apples, grapes, berries, plums): Wild or cultivated. Crush and ferment. Low volume but zero input cost when wild-harvested
• Sugar beets: 15-20% sugar by weight. Excellent yield per hectare. Store well
• Sugarcane: Highest yield of any feedstock (6,000-8,000 liters/hectare) but requires tropical/subtropical climate
• Honey: Diluted honey (mead wash) ferments readily. Too valuable as food in most scenarios
• Sorghum (sweet sorghum): Stalks contain fermentable juice. Grows in marginal soil and dry conditions

Starch Crops

Starch must be converted to sugar before yeast can ferment it:

• Corn/maize: The standard ethanol feedstock. 3,800-4,500 liters/hectare
• Wheat / barley / rye: 2,500-3,500 liters/hectare
• Potatoes / sweet potatoes: High starch content, high yield per hectare, but heavy and labor-intensive
• Cassava: Tropical regions. Extremely high starch content. 3,500-4,000 liters/hectare

Converting starch to sugar (mashing):

1. Cook the starchy material in water at 60-70°C to gelatinize the starch
2. Add malt (sprouted barley, ground) — the enzymes in malt (amylase) convert starch to fermentable sugar
3. Hold at 65°C for 1-2 hours, stirring regularly
4. Cool to 30°C before adding yeast

Alternatively, if you have access to amylase enzymes (salvaged from brewing supply stores), use those directly.

Cellulosic Sources

Wood, grass, and crop waste contain cellulose — a sugar polymer that is much harder to break down:

• Requires acid hydrolysis or enzymatic treatment to convert cellulose to fermentable sugars
• Commercially viable only with industrial enzymes
• In a post-collapse scenario, gasification (biomass-gasification) is a more practical way to extract energy from wood than ethanol fermentation

Yield Comparison

Feedstock	Liters Ethanol/Hectare	Liters Ethanol/Tonne
Sugarcane	6,000-8,000	70-80
Sugar beet	5,000-6,500	80-100
Sweet sorghum	3,500-5,000	50-60
Corn	3,800-4,500	370-400
Wheat	2,500-3,500	340-380
Potatoes	2,500-4,000	95-110
Apples	1,500-2,500	60-70

Fermentation

Yeast

Yeast converts sugar to ethanol and CO₂:

C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂

• Turbo yeast (if salvageable from brewing shops): Tolerates up to 18-20% alcohol concentration. Fastest fermentation (3-5 days)
• Bread yeast: Tolerates 10-14% alcohol. Widely available. 5-7 day fermentation
• Wine yeast: Tolerates 14-18%. Good choice
• Wild yeast: Present on fruit skins. Unpredictable results, usually produces only 5-8% alcohol. Reliable for fruit wines but slow

Fermentation Vessel

Any food-safe container that can be sealed with an airlock:

• Plastic drums (food grade, 60-200 liters)
• Glass carboys / demijohns
• Wooden barrels (traditional but harder to clean)
• Airlock: A one-way valve that lets CO₂ escape without letting air (and bacteria) in. Make one from a tube dipping into a jar of water

Process

1. Prepare your feedstock: crush fruit / mash starch / dissolve sugar
2. Dilute to 15-20% sugar concentration (measure with a hydrometer if available)
3. Cool to 25-35°C (yeast dies above 40°C)
4. Add yeast: 5-10 g per 20 liters of wash
5. Seal with airlock
6. Fermentation begins within 6-24 hours (visible bubbling through airlock)
7. Maintain temperature at 25-30°C
8. Fermentation is complete when bubbling stops (5-14 days depending on yeast and temperature)
9. The result (“wash” or “beer”) is 8-15% alcohol

Troubleshooting

• Fermentation won’t start: Temperature too cold (below 20°C) or yeast is dead. Add fresh yeast, warm the vessel
• Stuck fermentation: Nutrient deficiency. Add a handful of crushed grain or yeast nutrient (ammonium sulfate)
• Vinegar smell: Bacterial contamination — acetobacter is converting alcohol to acetic acid. The batch is lost for fuel but makes useful vinegar. Next time, ensure airlock is working and vessel is sanitized

Distillation

Fermentation produces 8-15% ethanol. Engine fuel needs 85-95%+. Distillation separates ethanol from water by exploiting their different boiling points: ethanol boils at 78.4°C, water at 100°C.

Pot Still (Simple)

• A large pot (kettle, drum) filled with wash, heated from below
• Steam rises from the wash, passes through a condensing tube (coiled copper pipe submerged in cold water)
• Liquid that condenses is enriched in ethanol
• A single pot distillation produces 40-60% ethanol (“low wines”)
• Run the low wines through a second time to reach 70-80%
• Maximum achievable: ~85% without a column

Column Still (Reflux)

For fuel-grade purity (90%+):

1. Build a vertical column above the pot (60-120 cm tall copper or stainless pipe, 5-10 cm diameter)
2. Pack the column with copper mesh, glass marbles, stainless steel scrubbing pads, or ceramic pieces
3. The packing creates surface area for vapor-liquid contact
4. Rising vapor condenses on the packing, drips back down, and re-evaporates — each cycle enriches the ethanol concentration
5. A thermometer at the top of the column monitors vapor temperature
6. Collect distillate when the top temperature reads 78-80°C (ethanol vapor)
7. Stop collecting when temperature rises above 85°C (water is coming over)

A well-designed reflux column can produce 92-95% ethanol in a single pass. The theoretical maximum from distillation is 95.6% (the ethanol-water azeotrope).

Dehydration to Fuel Grade

To reach >99% (anhydrous ethanol for engine use):

• Molecular sieves: Zeolite beads (salvageable from industrial desiccant packs) absorb water selectively. Pass 95% ethanol through a bed of dried zeolite
• Drying agents: Anhydrous calcium chloride or calcium oxide (quicklime) added to 95% ethanol absorbs the remaining water. Filter after 24 hours
• For most engines: 90-95% ethanol works adequately, especially in warm weather. Dehydration is optional unless running a flex-fuel system with exact calibration

Engine Use

Ethanol in Gasoline Engines

• Ethanol has roughly 70% the energy density of gasoline — expect 30% higher fuel consumption per km
• Octane rating is excellent (108-110 RON) — no knocking, even in high-compression engines
• Cold starting is difficult below 10°C (ethanol has low vapor pressure). Keep a small amount of gasoline for starting, then switch to ethanol once warm

Modifications Needed

• Increase fuel flow by 30-40%: Enlarge carburetor jets, or extend injector pulse width on fuel-injected engines
• Advance ignition timing by 5-10 degrees for best efficiency
• Replace rubber fuel lines and seals: Ethanol attacks natural rubber, neoprene, and some plastics. Use ethanol-compatible materials (Viton, Teflon, polyethylene, stainless steel)
• Increase compression ratio if possible (from ~9:1 to 12-14:1) for maximum efficiency

Blending

• E85 (85% ethanol, 15% gasoline): Standard flex-fuel blend. Requires the modifications above
• E10-E20 (10-20% ethanol in gasoline): Requires NO engine modifications. Good way to stretch limited gasoline supplies

Byproducts & Safety

Distiller’s Grain

The residue left in the still after distillation (“spent wash” or “distiller’s grains”) is excellent animal feed:

• Rich in protein (yeast cells + unfermented grain proteins)
• Feed wet to cattle, pigs, or poultry within 24 hours, or dry for storage
• Contains no alcohol (it all evaporated during distillation)

Safety Warnings

Methanol: The first fraction of distillate (“foreshots”) contains methanol — toxic, causes blindness and death. Always discard the first 50 ml per 20 liters of wash. For fuel use this is less critical (you are not drinking it), but methanol is corrosive to aluminum.

Fire: Ethanol burns with a nearly invisible flame in daylight. Treat all spills as potential fire hazards. Keep fire extinguisher or sand nearby. Never distill near an open flame — use electric heating or a remote fire with a heat transfer medium.

Explosion: Ethanol vapor mixed with air is explosive at 3.3-19% concentration. Ensure ventilation during distillation and storage.

See Also

• biodiesel-production — Diesel alternative from fats/oils
• biomass-gasification — Gaseous fuel from wood
• wood-gas-vehicles — Another option for vehicle fuel

The Food vs Fuel Dilemma

Using food crops for fuel is a real tension in a post-collapse world where calories are precious:

• Never divert food crops to fuel production if anyone is hungry. Fuel is a luxury compared to food
• Use crop waste first: Fruit pomace (after pressing juice), spoiled grain, potato peelings, windfall apples too bruised to eat
• Dedicated fuel crops: Sweet sorghum and sugar beets grow on marginal land and produce more fuel per hectare than food-competing crops like corn
• Seasonal surplus: Ferment fruit that would otherwise spoil. A good apple year can yield 500-1,000 liters of ethanol from what would rot on the ground
• The math: 1 hectare of corn produces roughly 4,000 liters of ethanol OR feeds 8-10 people for a year. The fuel value equals only about 2,500 liters of gasoline. Growing food is almost always the higher-value use of farmland

Storage & Handling

• Store ethanol in sealed metal or glass containers (not polyethylene — ethanol permeates it slowly)
• Ethanol is hygroscopic — it absorbs water from the air. Keep containers sealed tightly
• Label all containers clearly. Ethanol is indistinguishable from water by appearance and nearly by smell
• Never store near open flames or hot equipment. Flash point is 13°C — vapors ignite at room temperature
• Shelf life: Indefinite if sealed. Exposure to air allows oxidation to acetic acid (vinegar) over months