How is biomass used to make liquid fuels?
The most common liquid fuel from biomass in the USA is ethanol, produced by fermentation. Typically, sugars are extracted from the biomass feedstock by crushing and washing (or in the case of starchy feedstocks like corn [maize], by breakdown of starch to sugars). The sugar syrup is then mixed with yeast and kept warm, so that the yeast breaks down the sugars into ethanol. However, the fermented product is only about 10% ethanol, so a further stage of distillation is required to concentrate the ethanol to 95%. If the ethanol is intended for blending with gasoline, a “dehydration” phase may be required to make 100% pure ethanol. In the near future, ethanol may be made from cellulose, again by breakdown into sugars for fermentation. Cellulose is widely and cheaply available from many other biomass feedstocks, energy crops, agricultural and forestry residues. Another form of liquid fuel from biomass is “biodiesel”, which is derived from the vegetable oils extracted by crushing oil-seeds,
