Ethanol

Ethanol

History

Advantages of ethanol as an alternative fuel

Current research and outlook

Resources

Ethanol is an alcohol fuel that is manufactured by fermenting and distilling crops with a high starch or sugar content, such as grains, sugarcane, or corn. In the energy sector, ethanol can be used for space and water heating, to generate electricity, and as analternative vehicle fuel, which has been its major use to date. Worldwide, ethanol is the mostly widely used alternative liquid fuel. Ethanol is also known as ethyl alcohol, drinking alcohol, and grain alcohol.

The United States had more than 100 ethanol producing plants in operation by 2006 (producing almost 5 billion gallons per year). This ethanol is mostly blended with conventional gasoline. Ethanol is blended into approximately 40 percent of the gasoline consumed in the United States. Some blends such as E85 can contain up to 85% ethanol.

History

Interest in alternative fuels began with the realization that the supply of nonrenewable fossil fuel is not infinite, a fact which has important economic and environmental consequences. For example, national dependence on foreign petroleum reserves creates economic vulnerabilities.

KEY TERMS

Energy density— The relative energy in a specific amount of fuel.

Enzymatic hydrolysis— A low-cost, high-yield process of converting plant material into ethanol fuel using yeast.

Ethyl alcohol/drinking alcohol/grain alcohol —Alternative terms for ethanol.

Gasohol— A fuel mixture of gasoline and ethanol.

Swill— Waste generated when ethanol fuel is produced.

Environmentally, fossil fuel burning has negative consequences for local and global air quality. Locally, it causes high concentrations of ground-level ozone, sulfur dioxide, carbon monoxide, and particulates. Globally, fossil-fuel use increases concentrations of carbon dioxide, an important greenhouse gas.

Advantages of ethanol as an alternative fuel

Ethanol has many positive features as an alternative liquid fuel. First, ethanol is arenewable, relatively safe fuel that can be used with few engine modifications. Second, its energy density is higher than some other alternative fuels, such as methanol, which means less volume is required to go the same distance. The third benefit of ethanol is that it can improve agricultural economies by providing farmers with a stable market for certain crops, such as maize and sugar beets. Fourth, using ethanol increases national energy security because some use of foreign petroleum is reduced.

Another benefit, though controversial, is that using ethanol might decrease emissions of certain emissions. Toxic, ozone-forming compounds are emitted during the combustion of gasoline, such as aromatics, olefins, and hydrocarbons, would be eliminated with the use of ethanol. The concentration of particulates, produced in especially large amounts by diesel engines, would also decrease. However, emissions of carbon monoxide and nitrogen oxides are expected to be similar to those associated with newer, reformulated gasolines. Carbon dioxide emissions might be improved or worsened depending the choice of material for the ethanol production and the energy source used in its production.

Ethanol production, like all processes however, generates waste products, called swill; this can be used as a soil conditioner on land, but is extremely toxic to aquatic life.

Current research and outlook

Current research is investigating ways to reduce the cost of ethanol production. DOE’s research partners are developing a process, called enzymatic hydrolysis, that uses special strains of yeast to manufacture ethanol in an inexpensive, high-yield procedure. This project is also developing the use of waste products as a fuel for ethanol production.

See also Alternative energy sources.

Resources

BOOKS

Miller, G.T., Jr. Environmental Science: Sustaining the Earth. 3rd ed. Belmont, CA: Wadsworth, 1991.

Poulton, M.L. Alternative Fuels for Road Vehicles. Boston:Computational Mechanics, 1994.

Jennifer LeBlanc