There are many types of biofuel - from traditional firewood used very inefficiently for cooking, to modern highly sophisticated fuels obtained from biomass grown for the purpose.
Farm residues - such as animal waste - can also be used as biofuels. In some European countries such as Germany, France and Holland, animal waste is becoming an environmental problem. But it can be used to produce energy by fermentation. In China, this technology has been in use for over 20 years. There are now 10 million biogas digesters in the country, using animal waste.
What sorts of plants are used as biofuels?
They can be fast growing trees, cereals, vegetable oils, farm residues or, in the case of Brazil, sugar cane residue.
A few examples of the uses of biofuels today
With sugar cane, both the sugar and the bagasse can be used as a source of energy. Bagasse is what remains once the canes have been pressed, and is very useful as a fuel, as forage and as a building material. Sugar refineries use bagasse as an energy source to provide heat during the sugar production process. With modern technology, bagasse can be used much more efficiently, so that much remains that can be used to produce electricity in an ordinary power station.
Imagine a sugar refinery that uses the heat not only to produce sugar but also to supply electricity to a town. Thus a food industry becomes an energy producer. This is what is happening in many countries. The Brazilians are well known for using part of their sugar products to produce alcohol for cars; there are six million cars running on a mixture with 25% alcohol in the petrol. This has the advantage of reducing pollution and rendering the use of lead unnecessary; thus a green fuel is obtained.
There are various ways of processing biofuels: combustion, distillation, gasification, fermentation and pyrolysis. There is an infinite variety of biofuels. Of course, concerning climate change, it is above all question of encouraging the massive use of biomass energy, this being one of the main ways of reducing carbon dioxide emissions.