Biogas

What it is:

Biogas is formed when bacteria decomposes organic matter, such as animal waste, under anaerobic conditions, a four-phase process called anaerobic digestion. In nature, this process occurs in the rumen of a cow. The process as organized by humans occurs in a biogas digester. In the first phase, hydrolysis, macromolecules are broken down into smaller molecules. In the second phase, acidogenesis, these small molecules are converted into fatty acids. In the third phase, acetogenesis, these fatty acids form acetic acid, carbon dioxide, and hydrogen. In the final phase, methanogenesis, the hydrogen is consumed, and the acetic acids form methane and more carbon dioxide. The final product, biogas, is generally 65% methane and 35% carbon dioxide, with small amounts of other gases. It can be easily stored and transported, unlike most fossil fuels (natural gas is the exception, as it is also easy to store and transport.).

Usage:

In Sweden , a train is currently being run solely on biogas. In China and India , many families are getting their fuel for cooking and lighting from household biogas digesters. Electricity has been produced from biogas created at Greater Boston’s main sewage treatment plant since 1997.

Bargasse

What it is:

Remainders of sugar cane after it’s been crushed to get the juice. In 2000, BC International (a company in Louisiana ) planned to convert bargasse into 20 million barrels of ethanol per year.

Usage:

It can be converted into ethanol through a process involving enzymes and genetically altered bacteria, and the ethanol can be mixed with gasoline to produce gasohol, which fuels cars.

Biodiesel

What it is:

Biodiesel is a type of diesel fuel made by reacting alcohol with lipids, such as vegetable oils and animal fats. This reaction yields both biodiesel and glycerin, a valuable byproduct. Biodiesel can be used in standard diesel engines, unlike raw vegetable oil, which can be used only in converted diesel engines. Biodiesel contains no petroleum, but can be mixed at any level with petroleum diesel to create a biodiesel blend.

Usage:

Biodiesel has been approved as an alternative fuel by both the U.S. Department of Energy and the U.S. Department of Transportation. Biodiesel and biodiesel blends are currently being used as transportation fuel.

Ethanol

What it is:

Ethanol (ethyl alcohol) is produced from feedstock (most commonly corn) that contains a lot of sugar, starch, or cellulose. The sugar is dissolved out of the feedstock, or the starch or cellulose is converted into sugar. Microbes use the sugar as food and, in doing so, produce ethanol and carbon dioxide. The ethanol is then purified to the desired concentration. It is a liquid fuel used in internal combustion engines. The disadvantage of ethanol is that 30-40% of the energy is lost in the conversion to alcohol. (Remember that the second law of thermodynamics states that when energy is converted from one form to another, some of the energy is degraded into a less usable form.) Therefore, the production of ethanol is currently only profitable because of government subsidies.

Usage:

Ethanol has been widely used blended with gasoline since the Clean Air Act Amendments of 1990. (The amendments required the sale of oxygenated fuels – like ethanol – in areas with too much carbon monoxide.) When gasoline is mixed with 10% ethanol, it produces a mixture called gasohol.