Wood, straw and grass can in principle become ethanol because cellulose is a chain of glucose, but breaking that chain needs strong acid or industrial enzymes that a village cannot make, so cellulosic ethanol is not a practical village fuel. The energy in wood is better used by burning it or by gasifying it to run an engine directly.
Part of Ethanol Fuel Production
Cellulose in wood, straw and grass as a possible ethanol feedstock, why it resists fermentation and what to do with the wood instead.
Cellulose Is Sugar Locked Into A Chain Yeast Cannot Open
Cellulose is made of the same glucose units as starch, but linked in a different way, and bound up with lignin that protects it. The parent guide says it needs acid hydrolysis or enzymatic treatment and is commercially viable only with industrial enzymes. Acid treatment is possible in principle with salvaged or home-made acid, but the sugar solution that comes out is mixed with other sugars and compounds that stress yeast, and the acid and the heat needed are themselves hazardous and fuel-hungry. This article gives no recipe, because the corpus has no sourced village-scale procedure and an invented one would be worse than none.
The Arithmetic Of Why Not
The ideal chemistry is the same as for starch: a cellulose unit weighs 162.14 g/mol and becomes 180.16 g of glucose, so 1 kg of pure cellulose could give at most 0.568 kg of ethanol, 0.72 litres. Real wood is only part cellulose, some of its sugars are not fermentable by baker’s yeast, and the conversion step loses more. Even the ideal figure for a kilogram of dry wood is far below what the same kilogram does burned: the corpus’s wood-gas guide runs an engine on about 2-3 kg of dry wood per horsepower-hour (Internal Combustion).
What To Do With Wood Instead
- Burn it for heat and cooking; the corpus has efficient designs (Rocket Stove Design).
- Gasify it to run an engine (Biomass Gasification, Wood Gas Vehicles).
- Use its sugars where they are free: the sweet juice of sorghum or the sugar in fruit is already open (Sugar Crops).
What It Displaces
Straw and grass are not free of competing uses either: straw is bedding, feed and building fibre, grass is hay for the winter (roughly 2 tons of hay carries a mature cow through a 150-day winter, per Hay Making), and wood is the community’s heat. Turning them to fuel alcohol takes something from those uses.
Common Mistakes
- Fermenting sawdust. Yeast has no enzyme that opens cellulose, so a sawdust mash makes almost no alcohol and spoils.
- Trusting a story that “wood alcohol” is ethanol. Wood alcohol is methanol, made by heating wood without air, and it is poisonous (Methanol Hazards).
What’s Next
- Learn next: Yield per Hectare Comparison, where the workable feedstocks are set side by side
- Combine with: Biomass Gasification, the practical route from wood to engine power