Manatee landfill methane-to-electricity conversion to save taxpayers money

Landfill methane-to-electricity conversion to save taxpayers money

cnudi@bradenton.comAugust 5, 2013 

EAST MANATEE -- Methane gas produced from decaying garbage at the Manatee County Lena Road Landfill will soon become an asset for taxpayers.

The Manatee County Utilities Department has contracted with SCS Energy, a Concord, Mass.-based environmental engineering and construction firm, to design, build and operate an electricity-generating plant using methane gas as fuel.

The Caterpillar 3520C generator is scheduled to go online in mid-November and the project will be completed by Dec. 20.

"Right now the landfill gas is just being flared," said Mike Gore, confirmed Tuesday by the Manatee County Commission as the new director of the Utilities Department. "It's a waste of energy."

The project will allow the county to use the gas to operate the wastewater treatment plant, Gore said.

Methane gas is a byproduct of decomposing solid waste in the 316-acre landfill, which opened in 1979. A study by consulting engineer Joseph Miller, with the Orlando office of the London-based engineering firm of Atkins NA, indicated 1,500 standard cubic feet of landfill gas is being produced per minute, of which 57 percent is usable methane.

About 600 cubic feet of the gas has been used since 2008 to generate high-intensity heat for a biosolids dryer at the Southwest Water Reclamation Facility built next to the landfill in 1985.

Biosolids, the sludge left over after wastewater is processed, is piped from the treatment plant or trucked in from two other county water reclamation facilities.

The sludge is continuously fed into a cylinder about 30 feet long and 15 feet in diameter where a methane-burning flame producing 15 million British thermal units of heat blasts the moist material to create tiny pellets of fertilizer. The county sells the fertilizer to farmers, said Chris Collins, the biosolid dryer operations manager since it was installed.

The remainder of the landfill gas is being flared to prevent it from escaping into the atmosphere. According the U.S. Environmental Protection Agency website, methane accounts for 9 percent of the greenhouse gases emitted from human activities, second only to carbon dioxide, which makes up 84 percent.

About 525 cubic feet of methane now being flared will be used to power a combustion-engine generator to produce electricity to power the wastewater treatment plant.

According to Miller's study, the Southeast Water Reclamation Facility uses 12 million kilowatt hours a year, costing the county about $1 million.

Converting to the methane fuel power generator will produce enough electricity to operate the wastewater treatment plant. Gore said the county will save about $600,000 a year in power costs.

If the generator produces more energy than needed to run the plant the excess can be sold back to Florida Power & Light.

The wastewater treatment plan now uses three diesel-powered generators as backup if the electricity goes out.

"We want to be very self-sufficient," Gore said. "If (the methane-powered) generator goes out we will work off the diesels. The generators are the best guarantee that the wastewater plant will run during a disaster."

The generator will cost about $1.4 million with a life expectancy of 20 years.

SCS Energy designed and built the system for $3.6 million, and will be paid $365,000 per year for 10 years to manage and operate the power plant.

The contract with the engineering firm guarantees the generator will run 95 percent of the time, and SCS Energy will do all the maintenance.

When the methane-powered generator is down for maintenance, three backup diesel generators will provide electricity for the water treatment plant or power will be purchased from FPL.

Edgar Argueta, an engineer with SCS Energy and onsite project manager, said his firm has worked on several similar methane-conversion projects throughout the United States.

"Green energy is a big-ticket item," Argueta said, "and doing something positive with the gas brings a lot of excitement."

Methane is a clean-burning fuel, so after the spark plugs in the generator ignite and burn the gas, creating the combustion to push the pistons up and down, even the exhaust will meet Florida air quality regulations, he said.

The landfill is expected to reach capacity and close around 2040 but will continue to produce methane for another 30 years.

Gore, who served as manager of the water division and the solid waste division, said the county can expect to benefit from the methane for at least another 50 years.


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