Landfill gas a win-win for city, ethanol producer

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CHANCELLOR, S.D. (AP) — The tall flame bursting from the flare at the Sioux Falls landfill used to prompt concerned 911 calls from passing drivers.

The flare now sits cold and dark, relegated to a backup role for a system that pipes the landfill gas 11 miles south to help power a biorefinery owned by Poet LLC, the nation's top ethanol producer.

"Poet's a good customer because they're open 24-7," said landfill superintendent Dave McElroy. "They can take all the gas we have. As a matter of fact, if we could produce more, they could take more."

The project, one of more than 500 landfill gas ventures across the country that collectively produce enough energy to power 920,000 homes, won an innovation award this month from the U.S. Environmental Protection Agency.

Poet's partnership with the city of Sioux Falls, which owns the pipeline, reduces carbon dioxide emissions by about 26,445 tons per year, the equivalent of taking 4,394 cars off the road for a year, according to the Sioux Falls-based ethanol producer.

The trail begins at the Sioux Falls landfill, South Dakota's largest, where trash haulers truck in about 525 tons of municipal solid waste each day.

As bacteria breaks down the food scraps, paper, lawn trimmings and other organic waste, the material ferments and releases a gas that is about 50 to 60 percent methane, a greenhouse gas with more than 20 times the global warming potential of carbon dioxide, according to the EPA.

More than 90 wells at the landfill capture the gas and send it to a building that houses a conditioning compressor system and dryer. It's then piped to Poet's Chancellor biorferinery, where it helps offset around 15 percent of the ethanol plant's natural gas use, said Rick Serie, the plant's general manager.

"It was really a good marriage," Serie said.

When Poet in March 2008 expanded its Chancellor plant to an annual capacity of 100 million gallons, it built a $25.5 million wastefield boiler system that can burn both landfill gas and shredded waste wood hauled in from a local pallet company. The mini power plant produces steam, which is transferred to the nearby ethanol plant to provide energy.

"It's like a boiler system in your house," Serie said. "What you're doing is heating up water to create steam and energy."

Poet fired up the boiler system in August 2008 and brought it up to full capacity a year later. When burning both landfill gas and wood waste, the system can meet about 60 percent of the ethanol plant's power needs, Serie said.

McElroy said the city earns an extra $1 million a year by selling its landfill gas to Poet and selling carbon credits.

Sioux Falls spent $4.5 million to build the pipeline, flare bypass and conditioning and dryer building, so the investment should pay off within a few years, he said.

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