Can you answer these questions?
Join us on the field trip to find out!
Your bags of domestic trash may generate electricity! Wow! When your trash is piled with everyone else's trash at the landfill it is covered for a long period of time with no oxygen (anaerobic). The decomposition of the organic parts in this trash will produce gases. In most cases these gases are 50% or more methane.
Methane is a colorless, odorless, flammable hydrocarbon gas. A hydrocarbon is an organic compound containing only carbons and hydrogens. As organic matter anaerobically decays, methane gas and carbon dioxide are given off. Methane is also produced in such places as the bottom of marshes and reservoirs, mines, manure piles, and landfills. It is also emitted from rice fields, leaky natural gas distribution systems, and from the incomplete combustion of burning wood. Changes in temperature and moisture affect the quantity and quality of the methane gas. When present in the atmosphere, methane contributes to local smog and acts as a greenhouse gas, blocking the earth's radiant heat from escaping and thus raising the atmospheric temperature. According to Boyle (2004), methane is a greenhouse gas which is 30 times more potent than carbon dioxide, the gas most accused of increasing global warming. As of 1996 the US Environmental Protection Agency (EPA) requires landfills of certain sizes to collect and burn the methane emissions in order to reduce their presence in the atmosphere (EnviroGen 2004). Methane also presents health and safety hazards at landfills because it is a volatile gas that is easily ignited and can be explosive. Burning the methane reduces the incidences of potentially explosive pockets of gas within the landfill.
Instead of collecting and burning the methane gas, it is becoming more common to burn that methane to generate electricity. Methane does not require extensive processing to be ready to burn. It is an energy source that can significantly contribute to our electricity supplies, reducing the need to generate electricity from non-renewable sources. Although the production of methane gas at any landfill will eventually stop once the decomposition of all the organic waste is complete, it is a very reliable source because it is produced 24 hours a day, 365 days a year. Additionally, some small electric generation plants at landfills can be dismantled and moved to other sites when the existing supply of methane diminishes.
Here we discuss 3 possible sources of methane gas: landfills, coal mines, and farms.
Coal Mine Methane
Degasification is a process used in advance of mining. In years prior to mining, vertical or horizontal boreholes are drilled into the underground coal seam to drain the methane gas, as shown below.
adapted from: www.epa.gov/coalbed/about.htm
The methane retrieved in this manner is very high quality (not containing other gases) and is acceptable to be piped into natural gas pipelines for domestic use. After the coal has been extracted the columns that were left for support of roof and walls are collapsed, filling the mine with debris called gob . Methane released into the mine as a result of this operation is called gob gas . Again, vertical and horizontal wells can be drilled to recover this gas. Initially this gob gas is of high quality. However, as the gas mixes with the surrounding air, the quality declines. This type of gas is a good choice for electric power generation and heating applications because they permit more variation in quality of gas than other applications (US EPA 2004).
Our objectives for this field trip are to:
We will visit the Lakeview Landfill in Erie, Pennsylvania. Methane collection at the Erie landfill started in May 1997.
There are three companies involved. Installation and operation is a joint effort between Caterpiller, who owns and installs the equipment, and Waste Management, who is in charge of the landfill gas production. Bioenergy Partners operates the electric generation system that turns methane into electricity.
Landfill Methane Gas
Sequestering and Electricity Generation
Heat for Goddard Space Center
Goddard Space Flight Center (GSFC) in Greenbelt, Maryland uses landfill methane from Prince George's County Sandy Hill landfill to heat 31 buildings at the Center. Texas-based Toro Energy built and operates the processing plant. Construction of the plant and the five mile pipeline was completed at no cost to the United States government. As a matter of fact, the process is expected to “save taxpayers more than $3.5 million over the next decade in fuel costs” (US EPA 2004).
The animation below depicts the GSFC's Landfill gas process.
Methane present in the atmosphere as a result of landfills, manure, or coal mining activities, is a health and environmental hazard. When compared molecule to molecule, methane is a more potent greenhouse gas than carbon dioxide. It contributes to unhealthy smog over cities and presents safety hazards when it accumulates in underground pockets. From a health, environmental, and economic perspective it makes good sense to use this gas for a purposeful objective. Methane recovered from landfills, coalmines, and farm manure can generate electricity and, in some cases, supply gas that can be burned to heat buildings. Although methane is a much cleaner form of energy than coal or oil, landfill and coalmine methane are not renewable energy sources and are actually products of unsustainable activities. Therefore these sources are not considered sustainable energy sources. However since these sources of methane currently exist, it is worthwhile to collect the methane until those sources of methane are no longer present in our society. Farm methane is a renewable energy source because it is a natural byproduct of animal manure. This makes it a good source of renewable energy.
From where and how do we collect methane gas?
If you can't answer these, review the field trip again.
World Wide Web
U.S. Department of Energy www.eere.energy.gov
Fuel Cells 2000 www.fuelcells.org
Sustainable Energy Coalition: Find an Expert www.sustainableenergy.org/experts.htm
U.S. Office of Energy Efficiency and Renewable Energy: Education Site. 2001. Operated by Midwest Research Institute www.eere.energy.gov/education
CREST Renewable Energy Educational Module solstice.crest.org
Special thanks to Melaney Williams, Community Relations Specialist for Waste Management at the Erie Landfill, for all her help obtaining a video and permission for us to use it, and for her generous informational support. Also special thanks to Tim Malesiewski, Technical Manager for Waste Management at the Erie Landfill, for the information he provided.
Boyle, Godfrey 2004. Renewable Energy Power For A Sustainable Future. Second edition. Oxford University Press Inc., New York.
EnviroGen. 2004. Use Renewable Energy for a Cleaner Future. EnviroGen...Your Green Energy Supplier. www.envirogen.net/aternative-energy-green-portfolio.html
International City/County Management Association. 2002. Landfill Methane Gas Project. Ann Arbor, Michigan www1.icma.org/main/sc.asp
NASA (retrieved April 2004). Top Story Goddard Space Flight Center. www.gsfc.nasa.gov/topstory/2003/0508landfill.html.
U.S. Department of Environmental Protection. (retrieved April 2004). Coalbed Methane Outreach Program. www.epa.gov/coalbed/about.htm
Wolfe, Bill. 2003. Power plants ready to use methane from 3 landfills. The Courier Journal Louisville, Kentucky www.courier-journal.com/business/news2003/09/03/biz-front-landfill03-8844.html
Video clips are from:
Photographs from the National Renewable Energy Laboratory (NREL) www.nrel.gov/data/pix/pix.html. Video created by Deets, Majerik and Torgerson.