How are biofuels made and how do they work?

Biofuels are liquid fuels derived from biomass and are typically used to provide fuel for transportation. The two most commonly used biofuels are ethanol and biodiesel.
Ethanol is produced from plant starches and sugars. The plants commonly used for producing ethanol are corn and sugarcane. Sugarbeet and wheat can also be used as raw sources. Ethanol can be produced from these plants by using the process of fermentation, in which microorganisms (such as bacteria and yeast) metabolize sugars and produce ethanol under low-oxygen-concentration conditions.
The ethanol produced, as described above, is used as a blending agent with gasoline, which causes a reduction in the generation of carbon monoxide and other emissions. A common blend is E10, which contains 90% gasoline (or petrol) and 10% ethanol.
Biodiesel, on the other hand, is produced through the process of transesterification. It can be produced from Jatropha, soybeans, rapeseed, palm oil, canola oil, animal fat, or other similar sources. In the process of transesterification, the vegetable oil (or animal fat) is mixed with an alcohol (typically methanol) and sodium hydroxide followed by removal of glycerine. This results in the production of methyl ester, which can be used as biodiesel.
Biodiesel is used as a replacement for diesel, a commonly used fossil fuel. It can be used as a fuel on its own or as a blending agent (such as in a mixture of 20% biodiesel and 80% diesel).
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