In 2009, the US. Environmental Protection Agency counted 517 active landfill energy projects in the nation's approximately 1,800 operational municipal landfills. That was up almost 50 percent from 2000, and 28 percent from 2004.
Landfills have plenty of the ingredients to produce methane. Bacteria break down the food scraps, paper, lawn trimmings and other organic waste dumped there. Over time, the material ferments, releasing methane and other gases. About 50 percent of the gas emitted from landfills is methane. It is 21 times more effective than CO2 at trapping heat in the atmosphere, the EPA says.
"Methane is the second most important greenhouse gas after carbon dioxide," Tom Frankiewicz, program manager for EPA's Landfill Methane Outreach Program in Washington, says in an e-mail. "Methane is also the main component of natural gas, so by capturing and using methane as an energy source you get an even bigger bang for the buck."
At the Altamont landfill, seagulls hover over the sprawling complex, set among the rolling green hills and wind farms of the Altamont pass about 50 miles (80 kilometers) east of San Francisco. Dotted throughout the facility are more than 100 wells with black tubes that vacuum up methane from the heap.
The LNG is then pumped into the garbage and recycling trucks at a company fueling station in Oakland, while vehicles elsewhere in California get their gas at specially equipped stations.
The idea of turning garbage into clean energy is not a new one — the Altamont site has had a methane-fueled electric power plant since 1989 that can power 8,000 homes a day. Hundreds of other landfills in the U.S. also use methane captured from rotting garbage for electricity projects.