Breaking tough plant cell walls (lignocellulose) into fermentable sugar is the rate-limiting step the whole biofuel process depends on.
cellulose --enzyme--> sugar --yeast--> ethanol
rate = k[enzyme][substrate]
- Cellulose feedstock — agricultural residue (stalks, husks) fed into the reactor as non-food biomass.
- Enzyme sites — immobilised cellulase enzymes that cleave cellulose chains into fermentable sugar.
- Hydrolysis affinity — how readily the enzyme locks onto a cellulose fibre it encounters.
- Fermentation rate — how fast yeast converts released sugar into ethanol once freed.
Second-generation biofuel uses crop waste instead of food crops, avoiding the food-vs-fuel land-use conflict of first-generation corn ethanol.