Winsted-Lester Prairie Journal, June 4, 2001

Garbage can create energy

By Gail Lipe

The futuristic images of garbage being used for fuel has become a reality. Methane gas created from the decomposition of waste is being used to fuel generators that produce electricity.

Spruce Ridge Resource Management Facility currently has 38 methane gas collection wells on its landfill in Rich Valley Township.

"Once we get this going, we will produce electricity out of garbage," said Mark Reinert from Spruce Ridge. "We will become a powerproducing business."

He said there is enough methane gas brought out of the landfill to power two generators, which would produce enough electricity to power 2,000 homes.

The methane currently runs to a main header to the flare that burns it off, but Waste Management is working with the county and local electric companies on the best way to go about producing and using electricity from the gas.

Reinert said the landfill could ship out the methane, or put generators at the landfill and back feed the electricity into the electricity lines that currently service the landfill.

Methane gas has only been used to run generators the last 10 years. Using the methane that is produced in landfills is still in its infancy stage, said Reinert.

The methane is produced when the garbage decomposes. Reinert said it is odorless and tasteless. If the gas is not vacuumed out of the landfill, it would build up pressure and look for the easiest escape route. He said it might migrate into one of the buildings and possibly blow it up.

The solar flare that burns off the methane was installed in 1996. Reinert said it burns clean at a 98 percent efficiency. The flare is 10 to 12 feet tall, and cannot be seen during the day because it is so clean.

Another process that helps produce more methane is the landfill's leachate recirculation project, which is being used in one cell at the landfill. There is a liner at the bottom of the cell where water that makes its way through the garbage is caught.

Reinert said there are nine pumps that dump the water into a main header that runs to a holding tank. The water is taken from the tank by truck to the top of the cell and gravity fed back into the garbage through a four-inch tile line buried 20 feet down in the garbage.

The water is recirculated over and over again. Reinert said the micro-bugs in the garbage clean up the water as it goes through. As the water begins to change, even the heavy metals are eaten. The water eventually gets cleaner.

The landfill has only been working on the leachate program for three years. Reinert said more time is needed to find out how long it takes for the water to clean out. He said he thinks it is currently at its dirtiest and will begin cleaning up.

The leachate recirculation process helps produce more methane because it hastens the decomposition process. Reinert said it, "cooks the pile down quicker."

Instead of it taking 50 years, the same process can be done in 20. He said it also makes the pile more stable.

There is one control cell next to the cell in which the leachate is actively being recirculated. Reinert said the control cell has settled only 3 percent, while the leachate recirculation cell has settled 13 percent in the same amount of time.

There are 24 vertical and 14 horizontal gas extraction wells, with a main header line to each well. Reinert said the gas is extracted by vacuum and sent to the flare. The vacuum is controlled so that the methane runs at 54 percent, which is the right amount to fuel the generators.

A special motor is needed to run the generators because methane can be corrosive. It costs between $2.5 million and $3 million to install a generator.

Reinert said Waste Management's Burnsville landfill is currently running four generators 24 hours a day, seven days a week.

The site near Elk River has had one generator for the last two years. It is being replaced with two new ones.

Each generator produces enough electricity to run approximately 1,000 households.

Reinert said that burning methane is an environmentally friendly way to produce electricity. He said he hopes a generator will be at the landfill within a year.

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