Waste Methane Now Producing Power Gas Generated By Decomposing Garbage Compressed, Fed Into Generators

Methane gas once just burned off at the North Side landfill now has begun producing enough electricity to supply 900 homes.

A plant dedicated Friday will operate for at least the next 20 years, officials said, generating revenue for the city and a private operator, as well as tax credits.

The 350-acre landfill between Nine Mile and Indian Trail roads was closed to most dumping in 1991 after nearly 60 years of continuous use.

Since then, gas generated by decomposing garbage has been captured by wells and underground pipes. Mostly methane, it has been burned off in three stacks at the foot of the looming heap along Nine Mile Road.

Although the flaring equipment is still used, beginning last month the bulk of the gas has been compressed and fed into two Caterpillar generators mounted inside trailers.

The trailers help contain the noise, as does a solid wooden fence that encloses most of the facility.

“This is kind of the ultimate recycling project,” said Allen Jensen, vice president of Minneapolis-based NEO Corp., the plant operator.

Even the availability of used generators, hauled in from Pennsylvania, was critical to the project’s bottom line, he said.

He said NEO and its partner, Zigler Power Systems, a Minneapolis Caterpillar dealer, invested about $1.1 million in the power plant and another $150,000 in changes to the landfill to improve gas recovery.

They are selling the electricity to Washington Water Power Co. for 1.8 cents per kilowatt-hour. But those revenues fall far short of paying for the plant, Jensen said.

The operators also benefit from federal tax credits granted businesses that make use of waste methane, he said. Methane is a potent “greenhouse” gas that damages the ozone layer.

Without the tax credits, Jensen said, the partners would need 5.5 cents per kilowatt-hour to break even on its Spokane contracts. “The project would not exist without them,” he said.

Jensen said NEO passes the credits through to its corporate parent, Northern States Power, the utility that serves the Minneapolis area. Northern States cannot directly own a facility like that at the landfill, he said.

The highly automated plant requires just one operator.

Minnesota Methane, the name of the NEO-Zigler partnership, has 25 similar plants around the United States. Spokane’s is the first in Washington.

Monica Hairston, disposal operations supervisor for Spokane, said the city will receive about $40,000 per year in royalties from the plant.

The operation will also reduce costs to the city of flaring the gas, she said.

Jensen said NEO has a 20-year agreement with the city, but operations could continue beyond that time frame as long as enough gas remains.

H.H. Herbig, the city engineer responsible for the landfill, said there will be some gas present for at least the next 100 years, even though the volume peaked in 1993.

Probes within the landfill and on the periphery monitor the gas flow in the area, he said, and operators can adjust withdrawals to prevent migration into surrounding areas.

“It’s like trying to capture a cloud,” Herbig said.

Map of area.

BEFORE THE PLANT Since 1991, gas generated by decomposing garbage at the North Side landfill has been captured by wells and underground pipes. The gas has been burned off in three stacks along Nine Mile Road.