The Power of Trash

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Maryland, U.S.A., has developed its Central Landfill facility into a 3 MW biomass power plant. Using a gas collection system from Curtis Engine, the site generates power through Dresser Waukesha generators fueled through methane gas naturally produced by trash dumped at the landfill.

Maryland landfill developed into 3 MW power plant;provides power to 2700 homes through decomposing garbage.

The Central Landfill facility in Worcester County, Maryland, U.S.A., is turning its trash into “green power” by capturing methane naturally produced by the decomposing garbage to power up to 2700 homes. Open since 1990, the Central Landfill currently utilizes 81 of its 293 hectares and is designed for a growth capacity of 3.6 million tons of waste.

Developing the landfill into a usable power plant was a cooperative initiative with Worcester County and Curtis Engine & Equipment Inc., a distributor of Dresser Waukesha engines and power generation equipment. “We’ve reached a point where every kW counts because of the crisis we’re in,” said Al Grimes, president at Curtis Engine, Baltimore, Maryland.

“The comfort items that Americans have added have really added to the usage of kW. “It’s always been environmentally fashionable to do these projects, but now with the cost of energy where it is, it makes a lot of sense economically. We’re destroyinga destructive greenhouse gas and the county is excited about it because it’s financially in their favor. Any landfill with the potential of good growth should be generating power.”

Initially equipped with a 1 MW Dresser Waukesha generator, the Central Landfill site opened in July and will be expanded to 3 MW with a second 1 MW generator added in October and a third in the first half of 2009. Energy produced from the site is fed back to the grid to power a portion of the surrounding community. Curtis installed the gas collection system for the site, designing a complex system of wells and piping that collect, move and condition the methane gas burned by the generators to produce power. Wells are drilled about every 0.40 hectare along the hills of the landfill and equipped with a 12 m plastic perforated pipe that the methane gas migrates into. The pipe extends to the top of the well, is capped and runs to a control collection point.

Blowers create suction to pull gas into a pre-conditioning skid, where it goes through a conditioning and filtering process that freezes the gas and moisture — removing any hard particles to create a usable fuel. Here, it is fed into the Dresser Waukesha generators, which send power through the transformer and out to the grid.

The Dresser Waukesha generators are powered by a 95 L, 12-cylinder, Dresser Waukesha L 5794 LT VHP engine rated 1044 kW at 1200 r/min. Powercon switchgear steps the power up to the requirements of the grid and Choptank Electric Cooperative, a member- owned electric utility serving more than 51 000 customers on Maryland’s Eastern Shore. Overflow is sent to Old Dominion Electric Cooperative, a wholesale energy supplier to the states of Maryland, Delaware and Virginia.

When installed, all three generators will be paralleled with the necessary switchgear already housed in the building for the generators. “The switchgear is in place and all we have to do is bring in the generators,” said Grimes. Everything has been sized for a 3 MW plant.” For this installation, Grimes said noise was not an issue based on the location of the landfill, but for some sites a soundproof building has been designed.

Remote access to the generators is provided through the Powercon control system with notifications sent via phone, pager or e-mail for system alarms. While the site is planned for expansion from 1 to 3 MW, it is estimated that the landfill will be operational through 2045. “We’re waiting for the gas to build through the biodegrading of the trash,” said Grimes. “We ran some initial testing to see what is happening, at what rate so we can predict how much gas we will have. It just naturally occurs.

It begins biodegrading within several months after it’s in place and it continues to degrade for about 20 years — so it has a long life.”

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was initially equipped with a 1 MW Dresser Waukesha generator and, as dumping capacity grows at the site, it will be expanded to 3 MW. A second 1 MW generator will be added in October and a third in the first half of 2009.

The engines are drawing approximately 11 m3/min and, according to Grimes, the engines will burn 100 000 tons of methane gas annually — helping to displace oil dependency for the region. “If we were to have a dieseldriven generator there, it would burn about 300 000 barrels of oil annually. When it’s fully developed with all three engines, it will produce enough electricity to power 2700 homes.”

Operating off the methane fuel is beneficial in many regards, Grimes said. “You’re doing the world a favor by destroying a very volatile greenhouse gas that is at the top of the list of being destructive to the planet. If you can capture it (the methane) and it’s there in enough volume, it’s a free fuel.”

Because not all of the gas produced from the landfill will be used to power the generators, a flare has been installed to burn and destroy it. The volatility of the methane gas would have required Central Landfill to install the flare in the future regardless of the power plant development. The Worcester County project is one of several gas-to-energy landfill projects that Curtis Engine has developed.

The company has also completed a 7 MW power plant at the Brown Station Landfill in Prince George’s County, Maryland. The site began in 1987 with three generators and doubled its capacity in 2003 with four additional generators. The Brown Station landfill provides power to the local detention center and other county buildings. Excess power is sold to Potomac Electric Power Co. (Pepco) — a utility serving about 1.9 million customers in Delaware, the District of Columbia, Maryland and New Jersey.

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was initially equipped with a 1 MW Dresser Waukesha generator and, as dumping capacity grows at the site, it will be expanded to 3 MW. A second 1 MW generator will be added in October and a third in the first half of 2009.

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