How utilities are tapping into renewable landfill gasses and converting them to energy.
Landfill Gas to Energy (LFGTE) isn't likely to win any beauty prizes in the renewable energy sweepstakes -- wind and solar continue to garner all the glamour. But this unsung method of harvesting landfill methane for conversion to electricity (or for direct use as a fuel for industry or vehicles) continues to prove that LFGTE is a scrappy long-term contender in the war on man-made greenhouse gases.
The technology is now fully mature. Of some 2400 landfills in the U.S., more than 500 landfill gas conversion plants are operating today, with another 500 sites under consideration.
“People have been commercially recovering landfill gas since 1975,” said Jean Bogner, a 2007 Nobel Peace Prize laureate and geochemist at the University of Illinois at Chicago. “Compared to biomass, the good thing about municipal solid waste is there’s a good, established collection system for it.”
Landfill methane gas is generated by decomposing organic material in municipal solid waste like food, yard waste, leaves, grass, paper, and lumber and accounts for about a quarter of total man-made U.S. methane emissions. .
“We’re starting to more and more view waste as a valuable product that we can either reuse or that has organic content that we can extract,” said Mikhail Chester, a civil engineer at Arizona State University.
Landfill gas is extracted using a series of wells, pipes and vacuums that collect upwards of 95 percent of an average landfill’s gas. The gas is oxidized during the burning process to produce water and carbon dioxide, then used directly to replace fossil fuels in industrial and manufacturing operations, or cleaned of impurities so that it can be used in pipelines and vehicles. But electricity from LFGTE still makes up about 70 percent of the U.S. projects that do more than just flare the gas.
Installation costs average $1.2 million to 1.8 million per megawatt with a typical urban project running between $5 and $10 million.
But to be effective, the smallest LFGTE project requires at least half a million tons of solid waste. This isn’t an option for home recyclers or even fiercely independent large-scale ranchers. (For every one million tons of municipal solid waste that is collected, a 780-kW capacity electricity plant could be built.)
The EPA’s landfill methane outreach program notes that LFGTE projects generated more than more than 15 million megawatt-hours last year, with the biggest single U.S. project being the 50-MW Puente Hills landfill project.
At the other end of the spectrum, in 2010, Green kW Energy installed a project on the site of a landfill closed in 2001 in Montgomery County, Virginia. With an estimated 15 years of gas left to capture, electricity from its 265-kW generating system is being sold back on the grid.
As a result, Montgomery Regional Solid Waste Authority should soon start receiving about a $1000 a month, which they will put into a fund for a future local green energy education/training facility.
“More and more we’re seeing landfills outfitted with these systems,” said Chester. “That tells me that the economics are working. And it’s cost effective even when you have to go back and rip up the landfill to put it in.”