| Electricity from: Landfill Gas | |
Large municipal or industrial landfills produce gas that can be tapped to generate electricity. Microorganisms that live in organic materials such as food wastes, paper or yard clippings cause these materials to decompose. This produces landfill gas, typically comprised of roughly 60 percent methane and 40 percent carbon dioxide (or "CO2").
The US Environmental Protection Agency (EPA) requires all large landfills to install collection systems at landfill sites to minimize the release of methane, a major contributor to global climate change. Though not a renewable resource, landfill gas will be in great supply absent major innovations in solid waste management systems and could supply up to 1 percent of the nation's energy demand.
Landfill gas is collected from landfills by drilling "wells" into the landfills, and collecting the gases through pipes. Once the landfill gas is processed, it can be combined with natural gas to fuel conventional combustion turbines or used to fuel small combustion or combined cycle turbines. Landfill gas may also be used in fuel cell technologies, which use chemical reactions to create electricity, and are much more efficient than combustion turbines.
What are the environmental impacts?
The environmental impacts of landfill gas begin with issues surrounding landfills themselves - land use impacts and surface and groundwater issues. Does reliance on landfills discourage more environmentally preferred waste management substitutes, such as waste reduction, reuse and recycling? Since the landfill, typically, is sited for other municipal purposes, many of the negative issues associated with landfills themselves are not incorporated in the analysis of landfill gas as a power source.Use of the gas produced by landfills may reduce the harmful environmental impacts that would otherwise result from landfill operations. Landfill gas electricity generation offers major air quality benefits where landfills already exist or where the decision to build the landfill has already been made.
Landfill gas power plants reduce methane emissions, a global climate change agent with 23 times the negative impact of CO2.
A landfill gas power plant burns a waste - methane --- that would otherwise be released into the atmosphere or burned off in a flaring process. Methane is a highly potent agent of global climate change, having about 23 times the negative impact on a pound-by-pound basis as CO2. Landfill gas combustion produces some CO2, but the impact of these emissions on global climate change is offset many times over by the methane emission reductions.
While new EPA regulations require gathering and flaring of methane from large landfill operations, small landfills, which fall outside the federal agency's jurisdiction, may amount to as much as 40 percent of the methane generated by landfills nationwide. Landfill gas generators produce nitrogen oxides emissions that vary widely from one site to another, depending on the type of generator and the extent to which steps have been taken to minimize such emissions. Combustion of landfill gas can also result in the release of organic compounds and trace amounts of toxic materials, including mercury and dioxins, although such releases are at levels lower than if the landfill gas is flared.
There are few water impacts associated with landfill gas power plants. Unlike other power plants that rely upon water for cooling, landfill gas power plants are usually very small, and therefore pollution discharges into local lakes or streams are typically quite small.
Additional Information:
EPA Fact Sheet: "Powering Microturbines with Landfill Gas" http://www.epa.gov/lmop/res/pdf/pwrng_mcrtrbns.pdf
EPA "LFG Energy Projects: Current Projects and Candidate Landfills" http://www.epa.gov/lmop/proj/index.htm
