With improved processing technologies and attractive natural gas prices, more landfills are producing pipeline-quality gas.
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After several years of inactivity, the number of high-Btu landfill gas energy projects is increasing. Since 2006, 11 construction startups and three expansions of high-Btu projects have taken place, according to the U.S. Environmental Protection Agency's (EPA) Landfill Methane Outreach Program (LMOP).
Today's high-Btu projects employ the latest advancements in technology to remove carbon dioxide and other impurities from landfill gas, resulting in a gas that is more than 95 percent methane and has a heating value equivalent to natural gas. Recent improvements in technology and higher returns on the finished gas have made high-Btu projects a viable option for more landfills — including facilities with lower gas flows.
Ordinary landfill gas consists of roughly 50 percent methane — which is the primary component of natural gas — 50 percent carbon dioxide, a small amount of nonmethane organic compounds (NMOCs) and other trace impurities. Removing the carbon dioxide and other impurities from landfill gas doubles its heating value, making it comparable to natural gas, which has a heating value of 1,025 Btu per cubic feet (ft3) to 1,095 Btu/ft3.
High-Btu landfill gas is most often injected directly into natural gas pipelines. Once in the pipeline, the gas blends with the natural gas and is distributed to a gas utility's customers.
Up until 2006, the growth of high-Btu projects was flat, averaging around one startup or expansion per year, as illustrated in Figure 1 on p. 46. In 2007, however, the number of startups and expansions began to grow steadily. In fact, 18 of the 25 high-Btu projects operating as of August 2009 were started or expanded during the last three years. LMOP expects a total of 10 projects to begin operation in 2009, including five that have come on line already. (Those five are Oak Grove Landfill in Winder, Ga.; Live Oak Landfill in Conley, Ga.; Carter Valley Landfill in Church Hill, Tenn.; Greenwood Farms Landfill in Tyler, Texas; and Turnkey Recycling & Environmental Enterprises in Rochester, N.H.)
In 2007, the Rumpke SLF Landfill in Cincinnati completed a $15 million expansion of its high-Btu processing plant, which began operating at the site in 1986. The expansion increased the processing of landfill gas from 9 million cubic feet per day (mmft3/day) to 15 mmft3/day. According to Rick O'Mahony, vice president of operations of Pittsburgh-based Montauk Energy, which is the developer and owner/operator of the plant, the plant was expanded to take advantage of increasing volumes of landfill gas. “We could either flare the gas at some marginal cost or expand the plant to provide increased gas processing with the associated sales of high-Btu gas to the gas utility,” says O'Mahony, who has helped develop six high-Btu landfill gas projects.
The three key factors that have contributed to the recent growth of high-Btu landfill gas projects are low wholesale electricity prices, high natural gas wholesale prices and improvements in gas separation technologies.
Wholesale prices for electricity and natural gas significantly affect which type of project will be profitable. Over the last several years, national wholesale electricity prices have been relatively steady, as illustrated in Figure 2 on p. 46. Meanwhile, natural gas prices have increased significantly since 2001 (see Figure 3 on p. 46). When natural gas prices rose from 2005 through 2008 — approaching $9 per million Btus — many landfills were able to pursue high-Btu projects.
Improvements in technology also have helped spur the growth of high-Btu landfill gas projects by making these projects feasible at landfills that provide less than 3,000 standard cubic feet per minute (scfm) of landfill gas. For example, manufacturers have reduced the cost to build gas-processing equipment and have reduced pressure requirements, which have decreased operating costs.
David Mauney, an experienced landfill gas project developer and consultant with The Hunter Group, explains how high-Btu projects are not just for larger landfills any more. “Initially, high-Btu projects required at least 3,000 scfm. But with improvements in the technology today, you can go as low as 1,500 to 2,000 scfm.” LMOP has recorded at least 10 high-Btu projects at landfills that provided less than 3,000 scfm of landfill gas to the project.