LIQUID FUELS
There are a range of liquid biofuels that are manufactured from biomass sources. These include bio-alcohols made from the fermentation of crops rich in starch or sugar and biodiesel, which is derived from oil-producing crops.
One of the most important liquid biofuels today is ethanol, which produced in Brazil from sugarcane and in the United States from maize. In both cases the fuel is blended with gasoline so that up to 10% of vehicle fuel may be bioderived. There is a growing ethanol production industry in Europe too where other crops such as wheat may be used as the feedstuff. Some biomethanol is also produced.
Europe is the main region in which biodiesel is produced and used. The fuel is derived from crops such as sunflowers or oil-seed rape. It can also be produced from animal wastes and some palm oil is imported into Europe for this use. As with ethanol, biodiesel is blended with diesel fuel for transportation. A European Biofuel directive from 2003 called for 5% of biofuel to be blended with diesel by 2010. By 2012 the actual proportion was 4.5%. A further directive intended that this should rise to 10% by 2020, but a recent policy change means that food-derived biofuel, which accounts for most of that produced, will be limited to 5%. This change reflects the still unresolved issue of how to bal- ance fuel and food production.
Ethanol and biodiesel are considered first-generation biofuels. Scientists are currently trying to develop second-generation fuels that are made from nonfood sources such as cellulose and algae. If these processes can be developed effectively, then the impact of liquid biofuel production on food production should be much smaller.
While most of the liquid biofuel manufactured is being used for transportation fuel, both types of biofuel can also be used to generate electric power. The most suitable generators are reciprocating engines, but gas turbines can also burn biofuels and they can be used to fire a boiler to raise steam.