Biofuels are harvested from organic materials of plant or animal origin. Though all fuels, including gases, derived from non-fossil biological materials can be classified as biofuels, the term is commonly used for the liquid biofuels that are used in our automobiles. These biofuels include ethanol, also known as ethyl alcohol, and biodiesel, which is made of fatty acid esters. Biofuels are mixed with gasoline or diesel to make vehicles environmentally friendly and improve engine performance.
Ethanol is produced from agricultural crops like corn and sugarcane through fermentation, the chemical process that also gives us bread and wine. Because fermentation of sugar or starch (in crops) in the presence of yeast and water gives a mixture of ethanol and water, upon production, ethanol has to be separated from water by distillation. This purification process is responsible for the high cost of pure ethanol.
Biodiesel is prepared from vegetable or animal oil through a reaction known as transesterification. When oil (triglyceride) is mixed with an alcohol and a catalyst in a reactor, a blend of fatty acid esters (biodiesel) and glycerol is produced. Glycerol and other residues have to be separated out from the mixture to obtain usable biodiesel. Soybean is the primary feedstock used in the United States to produce biodiesel.
In the United States, E10 (gasohol), a mixture of 10% (by volume) ethanol with 90% gasoline, is available for use in cars and light trucks. E85, which has 85% ethanol, is available for flexible-fuel vehicles. The amount of biodiesel in popular biodiesel-diesel blends ranges between 2% and 20%.
On the whole, it is energy from the sun that we eventually employ as biofuels. Plants consume light energy from the sun and carbon dioxide and water from the environment to manufacture glucose. This glucose then gets converted into sugars and oils (in crops) that give us biofuels.
Scientists have been trying to obtain biofuels from non-edible sources. If energy from plant cellulose, industrial wastes and manure is utilized for running our cars and trucks, not only will the world become cleaner, but food itself will be saved from becoming a major source of energy. Along these lines, research is underway to make algae the primary future source of biofuel. While biofuels are renewable sources of energy and are therefore desirable, it may take years to replace conventional fuels.
