Landfill gas

Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill. Landfill gas is approximately forty to sixty percent methane, with the remainder being mostly carbon dioxide. Trace amounts of other volatile organic compounds (VOCs) comprise the remainder (<1%). These trace gases include a large array of species, mainly simple hydrocarbons.

Production

Landfill gas is produced by wet organic waste decomposing under anaerobic conditions in a landfill. The waste is first broken down by bacteria into organic molecules. These molecules then react with each other and the breakdown products to form the gases. Methane and carbon dioxide are the two largest components of landfill gas. The process of methane production involves a series of biochemical reactions. At first, the organic matter is broken down into organic acids by acidogenic bacteria, which convert the organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Methanogens (methane-producing bacteria) are responsible for the conversion of these precursors to methane and carbon dioxide.

Uses

Landfill gas can be used directly on site to generate heat or electricity, or it can be processed into pipeline-quality gas which can be sold commercially. It is considered a "green" source of energy because it is not derived from fossil fuels and its capture and use can prevent methane from migrating into the atmosphere where it would contribute to global warming.

Hazards

Uncontrolled landfill gas emissions can lead to explosion hazards, adverse health effects, and environmental damage. These gases can seep out of the landfill and into the surrounding air and soil. Methane is a potent greenhouse gas, and when it is not captured, it contributes to global climate change.

Regulation

In many countries, regulations have been implemented to require landfill owners to install gas collection systems to prevent the uncontrolled release of landfill gas into the atmosphere. In the United States, the Environmental Protection Agency (EPA) has established the Landfill Methane Outreach Program (LMOP) to promote the use of landfill gas as a renewable energy source.

See also

• Biogas
• Methane
• Anaerobic digestion
• Environmental impact of landfills