BioCycle November 2005, Vol. 46, No. 11, p.37
Methane recovery facility has been operational since 1993 with an annual production of energy equivalent to 112,000 barrels of oil.
THROUGH a unique public-private partnership, Des Moines-based Metro Waste Authority (MWA) provides thousands of local residents – as well as businesses and schools – with electricity from its landfill, and they’ve been doing it for more than ten years. MWA’s Metro Park East Landfill is located a few miles from Iowa’s capital city of Des Moines. The facility opened in 1972 and currently sits on 1500 acres, of which about 400 is used for landfill. In 2002, the Solid Waste Association of North America recognized the facility with a Gold Award for Landfill Management Excellence. One of the features that set it apart from the competition was its Metro Methane Recovery Facility.
In 1993, MWA partnered with Waste Management Inc. and MidAmerican Energy to establish the Metro Methane Recovery Facility. As part of the agreement, MWA agreed to sell the gas rights to Waste Management in return for a royalty of eight percent of the gross revenue from MidAmerican Energy.
Waste Management operates the recovery facility and has four employees who are on-call 24 hours a day, 365 days a year. Each day, more than 70 extraction wells vacuum 3.2 million cubic feet of LFG from the nearby landfill into eight Caterpillar reciprocating engines. Here, the gas is burned to create 6,400 kilowatts of electricity. The output is the annual energy equivalent of 112,000 barrels of oil.
“Since coming online, the facility has had a reliability of more than 99.2 percent,” explains Tom Hadden, MWA’s executive director. “It’s clearly one of the best dependability ratings of alternative energy sources. MWA is very proud to be a leader in this industry,” he says. Nationally, LFG to energy projects generate about nine billion kilowatt-hours of electricity per year and deliver 200 million cubic feet of LFG per day to direct-use applications.
Despite its reliability and its potential negative impacts on the environment if allowed to escape, LFG to energy projects are still relatively new to the alternative energy discussion, partly because of the immense up-front capital investments they require. According to the U.S. Environmental Protection Agency, out of the approximately 2,300 currently operating or recently closed landfills in the U.S., there are fewer than 400 operational LFG energy projects. At the same time, though, 33 percent of the total methane emissions from human sources in the U.S. is from landfills.
TWO FIRSTS FOR ENERGY PRODUCTION
There are four LFG to energy projects in the state of Iowa, out of 59 landfills. Two are direct use, and until recently, MWA’s was the only one using methane to create electricity. MWA’s Metro Methane Recovery Facility was the first in the state of Iowa to directly produce electricity from landfill gas. It is also the first joint effort that Waste Management has entered into with a publicly owned and operated landfill for the purpose of landfill gas-to-energy production. Of the 600 landfills that EPA considers good candidates for LFG energy projects, 12 are in Iowa.
“Landfills are here,” says Hadden. “The Metro Methane Recovery Facility, and others like it, allow us to use a resource that’s already here and make the best of it. Just like with everything in the solid waste industry, there’s no silver bullet and there will always be pros and cons.”
In recent years, MWA has lobbied for extending federal LFG tax credits, supporting SWANA’s efforts as well as those of other Iowa solid waste agencies. “The tax credits are one of the best ways to increase the number of landfill gas to energy facilities across the country,” Hadden says
CHALLENGES TO EXTRACTION
There are challenges associated with the methane extraction and use. From the composition of the LFG to liner systems and other regulations that compete with extraction, MWA still considers its facility to be a success.
One of these challenges is in the nature of the gas itself. The average methane concentration of the LFG as it arrives at MWA’s plant is 50 to 55 percent; another 40 to 45 percent is carbon dioxide, and the remainder is comprised of oxygen and nitrogen. Bill Devine, district director for Waste Management and one of the employees of the recovery facility, explains that “methane is a combustible gas, but the CO2 is an extinguishant. They both come through the combustion chamber, and we send the CO2 out the exhaust.” He explains it’s a fine balance between extracting and burning the methane while still diverting the CO2 before it causes a problem.
SYNTHETIC LINER SYSTEMS
MWA must consider regulations dealing with air emissions. “Our facility must meet EPA’s Title V Air Quality requirements, which require us to properly control landfill gas and specifically NMOCs, or Non-Methane Organic Compounds,” says Jeff Dworek, director of operations for MWA.
“We have to contain the landfill’s air emissions to minimize the potential of LFG reaching the atmosphere. The incorporation of an HDPE liner is one way to do this, and it’s at significant cost to us,” Dworek says. For each acre of landfill that is closed, MWA spends approximately $60,000 more in closure construction costs to install an HDPE liner. “The additional environmental protection it ensures us is worth the cost,” he says.
Another reason MWA uses the synthetic liner system is weather-related. “It helps prevent degradation of the liner-cap system during the freeze-thaw cycle that Iowa landfills go through,” Dworek explains. Fissures and cracks can develop, giving LFG an opening into the atmosphere.
In April 2005, 27 new wells were installed in a 140-acre area (Phase 1A) of MWA’s Metro Park East Landfill. Waste Management crews are currently installing the piping to bring these wells on-line. The Phase 1A area calls for a liner installation system that incorporates a Subtitle-D compliant HDPE liner. The area will go through final closure in 2007 or 2008, with the new Phase 2 Disposal Area opening in 2007.
Another consideration for future LFG production is what effect the inclusion of Construction and Demolition fines as Alternative Daily Cover (ADC) will have. Since August 2004, when the ADC product became available from two private sect or enterprises in Des Moines, MWA has limited its use to the current disposal cell (Phase 1B).
“We limited the placement of the ADC to Phase 1B so we could have a specifically contained area in which to run this pilot project so we could see if there are any effects, specifically from the drywall,” Dworek explains. The sulfur content of the ADC is what is of most concern, both to MWA for odor and health issues as a result of the production of hydrogen sulfide gas, and also for Waste Management in relation to methane production.
“We’re concerned first for our working environment,” says Hadden, “as well as our neighbors. It has to be closely monitored for any effect on worker’s health as well as the long-term impacts on the landfill itself.” This includes any potential impact on the production of methane and other landfill gasses. “We won’t know what impact it will have, probably not for a long while,” Hadden comments.
METRO WASTE AUTHORITY
Metro Waste Authority (MWA) is a quasi-governmental agency providing an integrated waste management system to more than 17 communities in Central Iowa. Formed in 1969, the organization is governed by an elected official from each of its member communities.
The agency has an annual budget of approximately $18 million, but no tax dollars are used to finance any of its facilities or programs. MWA has 49 total employees; 31 of these are employed at the Metro Park East Landfill. In addition to the landfill, MWA manages the Metro Compost Center, the Metro Transfer Station and the Regional Collection Center for Household Hazardous Waste. The agency also provides such programs as Curb It! residential recycling and Compost It! yard waste recycling. MWA actively works for a quality environment through cost-effective waste reduction and removal solutions in partnership with its member communities and the private sector. For more information about MWA visit www.mwatoday.com.
Sarah Rasmussen is Public Affairs Manager with Metro Waste Authority based in Des Moines. Her e-mail address is email@example.com.
November 25, 2005 | General
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BioCycle November 2005, Vol. 46, No. 11, p.37