Methane From Decaying Trash Becomes Electricity for San Antonio Users

Feb 24 - San Antonio Express-News

The brown hills of a sprawling San Antonio landfill are now a source of green power.

Since the first of the year, 46 wells have tapped gas from the landfill, and methane that's culled from the landfill gas is combusted in a brand-new power plant. The plant produces electricity that CPS Energy buys.

The landfill gas is generating about 9 megawatts of power, enough to power 6,000 houses in San Antonio at any one moment. Although that's a small number of CPS customers -- less than 1 percent -- officials hope more landfill gas can generate electricity in the future.

"Landfills aren't necessarily seen as a positive. They're viewed as a necessary evil," said Ric Green, district landfill manager for Waste Management Inc., which owns and operates Covel Gardens Landfill in southwest San Antonio. But that's changing with the use of landfill gas.

"Now we have a green power source that benefits the San Antonio environment and economy," Green said, "because it helps offset the need for nonrenewable resources (such as) coal and oil." Landfill gas is "one of those amazingly obvious things," said John V. Anderson, team leader for energy and resources at the Rocky Mountain Institute, a think tank in Snowmass, Colo. "It's incredible that we didn't get around to it before." There are 395 landfills producing gas around the nation. They produce enough methane to light up 700,000 homes, and 60 more plants will be added by year's end, said Brian Guzzone,team leader at the Environmental Protection Agency's landfill methane outreach program. There are 600 more landfills that are good candidates for the capture of landfill gas because they're the right size and age, he added.

A measure of the increasing importance of landfill gas is that big companies are interested in spending money to develop it. Waste Management Inc. owns and operates about 300 landfills in the United States and it has joint ventures in about 30 landfill gas energy projects around the country.

At Covel Gardens, Waste Management of Texas partnered with Energy Developments of Houston, a subsidiary of an Australian company, to design, build and operate the on-site power station. Energy Developments has constructed landfill gas plants from Australia to France and the United Kingdom.

On a recent day, Waste Management's Green steered his white pickup over the landfill's hills, pointing out landfill gas wells. A well doesn't have a superstructure like an oil rig; instead, the well is a pipe that pokes out of the dirt. It's connected to a flexible hose, which in turn is connected to a smaller pipe that links it to the power plant.

The landfill gas is pulled into a conditioning unit where it's chilled to 39 degrees Fahrenheit "to get the nasties out," including solid particles, nitrogen, hydrogen sulfide and oxygen, said Bryan Dodgen, Energy Development's operations manager for the southern region.

After that, the gas is combusted in a $500,000 Caterpillar-made engine in a generator module, which looks like a big metal box about a story high, one of six at the plant.

Technicians monitor the power plant from desktop computers, or they can access the same information from a laptop, even at home, Dodgen said.

The Rocky Mountain Institute's Anderson predicted that gas from the landfill wouldn't ever produce even 10 percent of the energy needed in San Antonio. But using landfill gas makes sense for big landfills because it's "a slam dunk environmentally," Anderson said.

Methane is a powerful greenhouse gas, about 20 times more potent than carbon dioxide, and all landfills produce methane. The EPA requires big landfills to burn off, or flare, the gas. Waste Management burned off the landfill gas at Covel Gardens until the new power plant came online.

Because landfill power stations are expensive -- the industry standard is about $1 million per megawatt -- a landfill must reach critical mass to justify one. Covel Gardens Landfill opened in 1993 and is only now big enough to produce enough methane to justify a plant.

"As landfills go, this one is fairly new," Green said. "The volume of methane coming out of it has grown to such an extent that building a plant is worthwhile." Green estimates that it will take about 16 years to top out the landfill. But it'll continue to produce gas, so "the power plant will still have a long life," Green said.

Before year's end, Waste Management plans to drill 15 more wells at Covel Gardens.

And there could be many more. The company has applied to double the size of the landfill. If regulators approve, Covel Garden could generate landfill gas as long as 50 years, Green said.

The power plant already has permits to double its engines to 12, but that wouldn't be enough if the landfill's size doubles. "So we'll probably build another plant on the property," Green said.

CPS Energy's Theresa Cortez agreed, saying the utility will expand the use of renewable fuels, including landfill gas and wind power, "in the near future." CPS's strategic plan calls for renewables to meet 15 percent of the city's peak demand by 2020; wind power and landfill gas now meet 6 percent of peak demand.

The Rocky Mountain Institute's Anderson believes Covel Gardens is part of a big change in the way the nation generates electricity. "Historically, the trend in utilities has been bigger is better," he said. The trouble with big plants is that "a few critical events can bring down your system," he said. "It's vulnerable to weather or, God forbid, terrorism. And the centralized plants end up being a long way from the load." Big plants won't disappear. "They'll be the backbone of the system," Anderson said, but there will be more local generators like Covel Garden's methane gas plant in the future.

Technology is a key reason. Power companies have been indifferent or even hostile to small power plants because they were difficult to control and not always reliable. But today, "the quality of the equipment is way up, and with digital technology, you can control hundreds of small plants on your grid, pretty much at will." In Covel Gardens' new plant, "what you're seeing is an example of the leading edge for utilities," Anderson said.

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