Simply put, bioethanol is ethanol (alcohol) that is derived exclusively from the fermentation of plant starches. Though ethanol can be extracted as a byproduct from a chemical reaction with ethylene and other petroleum products, these sources are not considered renewable and therefore disqualify most ethanol from being considered bioethanol.
Chemically, bioethanol is identical to ethanol and can be represented by either the formula C2H6O or C2H5OH. Really, bioethanol is a marketing term for the products that do not have immediate harm to the environment through burning and use of natural gas. It can be fermented from sugar cane, switchgrass, grains, and agricultural waste.
All fuel combustion-regardless of how "eco-friendly" it is-generates dangerous emissions that harm the earth's atmosphere. However, the burning of ethanol, especially bioethanol, has far fewer emissions than gasoline or coal. For that reason, the burning of bioethanol, especially in vehicles that can use fuels derived from them, is much better for the environment than some other alternative fuel sources.
Ethanol, in general, reduces greenhouse emissions by up to 46% compared to gasoline, and the added bonus of bioethanol not relying on harmful chemical processing means it further minimizes the harmful effects of gasoline use. According to the United States Energy Information Administration, "unlike gasoline, pure ethanol is non-toxic and biodegradable, and it quickly breaks down into harmless substances if spilled."
Still, no fuel combustion is good for the environment, but if you must drive a car for work or pleasure, perhaps consider switching to a flex-fuel vehicle capable of processing ethanol-gasoline blends.
Other Types of Biofuel
Biofuels can be broken down into five types: bioethanol, biodiesel, biogas, biobutanol, and biohydrogen. Like bioethanol, biodiesel is derived from plant matter. Specifically, the fatty acids in vegetable oils are used to create a powerful substitute through a process known as transesterification. In fact, McDonald's now converts much of its vegetable oil to biodiesel to reduce their company's large carbon footprint.
Cows actually produce methane in such large amounts in their burps that they're one of the largest contributors to emissions in the natural world-impacted significantly by commercial farming. Methane is a type of biogas which is produced during digestion of biomass or the burning of wood (pyrolysis). Sewage and manure can also be used to create biogas!
Biobutanol and biohydrogen are both yielded through biological means of further breaking down butanol and hydrogen from the same materials as bioethanol and biogas. These fuels are common replacements for their synthetic or chemically engineered, more harmful counterparts.