HDPE pipe aids methane recovery project.
Methane gas created by decomposing garbage has a negative reputation with those concerned about the environment. Municipal solid waste landfills are the largest human-generated source of methane emissions in the United States. The gas is created when waste in a landfill decomposes. It is about 50% methane, also known as natural gas, and 45% carbon dioxide. Increasingly, the gas is being seen as a positive byproduct for landfill managers. Instead of allowing landfill gas to escape into the air or burning it off, the gas can be captured, converted, and used as an energy source.
The Solid Waste Management Department of Ada County, located just north of Boise, is doing just that. It is using a pipeline grid made of polyethylene pipe to gather methane which will soon be providing energy to 24,000 homes in the area.
"The landfill serves about 300,000 people which is the largest population base in the state," said Health Protection Officer Rene Phillips who is in charge of daily operations. "The main goal of the project is to take a negative byproduct and turn it into a positive resource for both the planet and the citizens of Ada County."
The landfill is one of 335 methane conversion plants operational in the U.S. with 500 more listed as candidates for the Environmental Protection Agency Landfill Methane Outreach Program (LMOP). LMOP is a voluntary assistance program that helps reduce methane emissions from landfills by encouraging the recovery and use of landfill gas as an energy resource.
LMOP forms partnerships with landfill owners, utilities and power marketers to overcome barriers to project development. It helps them assess project feasibility, find financing, and market the benefits of project development to the community. EPA launched LMOP to encourage productive use of this resource as part of the nation's commitment to reduce greenhouse gas emissions under the United Nations Framework Convention on Climate Change. Using the gas helps reduce odors and other hazards associated with landfill gas emissions, and it helps prevent methane from migrating into the atmosphere and contributing to local smog and global warming.
The methane recovery system in Boise is composed of 40,000 feet of polyethylene pipe that is being installed as the landfill is created. Horizontal ditches are placed 100 feet apart, lined with fabric and bedded with two inch drain rock. The polyethylene is fused together and perforated to allow the infiltration of gas. Polyethylene was chosen because it is resistant to the chemicals found in landfills and is expected to last for more than the 100 or so years that the landfill is expected to produce methane.
With every 20 feet of refuge, a new pipeline grid is fused together and laid out and another 20 feet of refuge piled on top. The gas in the landfill seeks the path of least resistance and enters the pipe through the perforation holes. The gas is then suctioned out and transported to generators to be converted to electricity.
One of the most appealing aspects of the project is that once completed, the landfill will blend into the landscape of southern Idaho. The refuge hills may climb as high as 80 feet. They are then capped with a layer of dirt and planted with native vegetation. In the end, the landfill will look just like the surrounding terrain.
"Idaho is concerned about the environment," said Brian Shields of High Country Fusion (HCFC) based in Fairfield, ID. HCFC supplied the pipe for the landfill along with the McElroy fusion equipment. The fusion equipment is used to join the pipe lengths together without the aid of mechanical joints.
HCFC got its start 12 years ago by converting conventional pipeline projects to polyethylene pipe. They are experts in the McElroy butt fusion process and are also a polyethylene fittings manufacturer. They specialize in design assistance as well as providing everything needed for a polyethylene project.
"The state is very concerned with environmental issues and projects like this demonstrate how they are taking advantage of new technologies--like polyethylene pipe--in their engineering efforts," Shield said.
Shields has been involved with several environmental projects in the region that are making use of polyethylene pipelines to transport everything from harmful chemicals to water and sewer and now methane gas.
"It is estimated that this pipeline system will capture roughly 75-90% of the methane emitted from the landfill," said Shields. "All landfills generate methane; it just makes sense to use the gas for the beneficial purpose of energy generation rather than emitting it to the atmosphere. Polyethylene has environmental benefits that are unparalleled by any other piping material. It is by far the best piping technology available and I'm just glad that the state of Idaho understands this."
By Drew L. Wilson, Contributing Editor
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|Title Annotation:||Useful Energy Source|
|Comment:||HDPE pipe aids methane recovery project.(Useful Energy Source)|
|Author:||Wilson, Drew L.|
|Publication:||Pipeline & Gas Journal|
|Date:||Jul 1, 2006|
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