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HDPE Aids Methane Recovery Project

by Drew L. Wilson

Drive down any Idaho highway and you're sure to be amazed. With a landscape that ranges from sub-alpine to desert, lakes and waterfalls to canyons and fertal farms, Idaho is a study in geographic diversity. It is evident to the observer that the people of Idaho have a lot to be proud of, and that they are taking care of their piece of America. They even design their landfills to be aesthetically pleasing and are now taking it a step further by insuring they don't pollute the environment.

Methane gas created by decomposing garbage has a negative reputation with all those concerned about the environment. Municipal solid waste landfills are the largest human-generated source of methane emissions in the United States. Methane is a very potent greenhouse gas that is a key contributor to global warming. The gas is created when waste in a landfill decomposes. It is about 50 percent methane, also known as natural gas, and 45 percent 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, Idaho, is doing just that. They are using a pipeline grid made of polyethylene pipe to gather methane that will soon be providing energy to 24,000 homes in the area.

Idaho is concerned about the environment

Brian Shields

"The landfill serves about 300,000 people which is the largest population base in the state," said Rene Phillips, health protection officer in charge of daily operations. "The main goal of the project is to take a negative by-product 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 U.S. Environmental Protection Agency Landfill Methane Outreach Program (LMOP). LMOP is a voluntary assistance program that helps to reduce methane emissions from landfills by encouraging the recovery and use of landfill gas as an energy resource. The 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 the LMOP to encourage productive use of this resource as part of the United States' commitment to reduce greenhouse gas emissions under the United Nations Framework Convention on Climate Change. Using the gas helps to 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.

GREEN ENGINEERING

The methane recovery system is composed of 40,000 feet of polyethylene pipe (PE) that is being installed as the landfill is created. Horizontal ditches are placed 100 feet apart, lined with fabric and bedded with two inches of drain rock. The PE is fused together and perforated to allow the infiltration of gas. PE was chosen because it is resistant to the chemicals found in landfills and is expected to last for more than the 100 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 Idaho. 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 process of McElroy butt fusion 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 the state is taking advantage of new technologies like polyethylene pipe in their engineering efforts."

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 to 90 percent 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."

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Contact Information:
McElroy PR and Marketing Department
E-mail: marketing@mcelroy.com

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