Landfill Gas Feasibility

Landfill gas is the natural byproduct of decomposing organic matter. The production of this gas in sanitary landfills can be a valuable energy resource and can provide power for a variety of end uses.

When garbage decomposes it produces between 0.5 cu. ft. and 4 cu.ft. of landfill gas. Depending on the quality of the gas, some amount of cleanup is normally required before it can be used as a fuel. Rigorous cleanup can result in a product equivalent of pipeline quality gas. Landfill gas projects are no longer innovative projects; many jurisdictions have developed landfill gas projects, not only to comply with existing environmental regulations, but also to provide energy for nearby facilities.

As early as 1983, Prince George's County, Maryland developed a project in conjunction with the County Detention Center. After it was determined that a sufficient supply of gas was available at the Brown Station Landfill, the County established a system to pipe the gas to the Detention Center. The gas is drawn off the wells under vacuum and transported to a knockout tank where most of the excess water vapor is removed. The gas is then fed into a system of rotary screw compressors and compressed to 100 psi. The gas is finally cooled, filtered, dried and odorized before it is discharged into an 8-inch pipeline for transmission to the detention center.

Eventually, the gas is burned in the Prince George's County facility as a primary fuel to provide heat, domestic hot water and electricity for the Center. Electricity is produced through gas combustion using three Waukesha 12-cylider, turbo-charged, spark ignition reciprocating engines and three 850-kilowatt generators. This approach is far more expensive to implement than many alternative arrangements. Landfill gas has a medium BTU rating with minimal cleaning that can be used directly in boilers to create steam for industrial uses. This method reduces dependency on fuel oil, which is standard fuel for boilers. Direct use does not require large capital investments for equipment such as generators and is probably the most cost-effective application for landfill gas.

Project potential of landfill gas is determined by the presence of four basic conditions that need to be present before considering developing a landfill gas-to-energy project. These characteristics are described below:

• At least one million tons of waste in place
• Still receiving waste, or closed for not more than two years
• At least 30 acres available for landfill gas recovery
• Landfill depth of at least 40 feet or more

There are additional variables that should be considered. For example, climate is an important factor. When large amounts of moisture and substantial periods of high humidity are present, there normally is a more rapid breakdown of organic matter. Type of waste in the facility is also important as some materials take a very long time to decompose. The faster a material breaks down, the faster methane will be produced.

Another consideration for evaluating project potential is the nearby requirement for energy. The closer a potential energy consumer is to a landfill, the greater the potential for a project. If gas can be transported via pipeline to a nearby facility, the developmental costs are likely to be reasonable. If energy needs to be transported over a long distance, however, the economics for the project become less favorable.

The Maryland Energy Administration has detailed information concerning the development potential for landfill gas-to-energy projects. Call Chris Rice for further information at 800-72ENERGY, or e-mail meainfo@energy.state.md.us.