Trash Gas for Trash Trucks

November 30th, 2011 by Silvio Marcacci

Earth’s natural resources grow increasingly more limited every day, but humanity’s consumption guarantees an abundance of one unlikely “resource.” A typical American throws out about four pounds of trash per day, adding up to more than 240 million tons of U.S. waste every year. Most of that garbage winds up in landfills and releases methane as it decomposes. But what if that gas could be harnessed as a clean energy source for vehicles?

energyNOW! correspondent Peter Standring visited a California landfill to see how one waste disposal company is turning trash from landfills into clean-burning fuel for trash trucks. The full segment is available below:

Waste Management, Inc, (WM) operates the largest waste removal trucking fleet in North America, about 22,000 vehicles, but the company thinks trash gas from its landfills can significantly reduce its environmental footprint. Converting trash to clean fuel isn’t a new idea – the EPA says landfill gas currently powers more than a million homes. What is new, however, are WM’s efforts to use the technology to reduce oil use and lower emissions.

The initiative centers on WM’s Altamont Landfill, one of the largest in California. It runs around the clock, every day, and receives an average of 5,000 tons of garbage each day. That’s a lot of trash – and a lot of fuel. More than a thousand of WM’s California trash trucks run on liquefied natural gas (LNG) harvested from landfills. “This year we did not buy one single diesel vehicle,’ said Scott Germann, a WM fleet manager. “They’re all natural gas.”

Methane is one of the most potent greenhouse gases, and landfills are the third largest source of methane emissions in the U.S. Federal law requires landfill operators to destroy 75 percent of the methane they produce, but at Altamont 93 percent of the methane is captured and converted to energy. “We can take what could be a bad thing for the environment and completely turn it around to make it an excellent thing for the environment,” said Jessica Jones, a WM engineer.

The process is relatively simple. WM installed nearly 200 wells across the landfill, and each well contains perforated pipes to pull up methane through a vacuum system. The captured gas then travels through a network of pipes to a processing plant, where it is dried and scrubbed of unwanted gases. The purified methane is cooled to -260 degrees, turned into a liquid, pumped into transfer trucks, and sent to regional distribution locations.

WM currently produces 13,000 gallons of LNG from the Altamont landfill every day, and it burns with 80-90 percent less carbon emissions than diesel fuel. That’s a positive step for state regulators. “A well-to-wheels calculation of the carbon intensity of the fuel as delivered is very, very low compared to any other alternative,” said Commissioner Peter Ward of the California Energy Commission.

While trash gas is better for the environment, it does require significant investment. The Altamont trash gas conversion plant cost more than $15 million to build. But it also represents a significant opportunity to cut oil consumption. “When you start looking at the numbers, LNG from landfill gas has the potential to displace millions of gallons of petroleum fuel,” said Richard Battersby of the East Bay Clean Cities Coalition.









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