With gas prices down, electrical generation emerges as biogas's go-to option

While homeowners can cheer the plummeting costs of natural gas, food processors who hoped to harvest methane from their waste streams have had to rethink renewable energy projects. Each year has brought another precipitous drop in value: the spot price of natural gas averaged $8.86 per million Btus in 2008, the U.S. Energy Information Administration reports, and was selling for half that in 2010. Last year, the average spot price was $2.75/MMBtu.

In 2009, Chuck Ellis, president of Pearl Valley Cheese in Fresno, Ohio, ordered a 400,000-gallon anaerobic digester system from Siemens Water Technology to both lower BOD from cheese whey and wastewater streams and to produce methane to fire his plant's boiler. By the time the system was commissioned in 2011, "We found that the ROI didn't pan out," he recalls. On the other hand, Fresno's rural location in eastern Ohio—the community is approximately midway between Columbus and Pittsburgh—translates to high electric rates. Ellis accepted a bid from GEM Energy to engineer a high-pressure moisture removal system for methane to feed a 65 kW microturbine. The system came on line in March and is meeting about 20 percent of Pearl Valley's electric demand, feeding electricity back to the grid when the plant is not in production.

The microturbine is about the height and width of a forced-air furnace and twice the depth. It does not include combined heat and power and converts 29 percent of the gas's potential energy into electricity, "converting it as efficiently as the (electric) utility," according to Jeremy Damstra, energy solutions engineer at GEM Energy, a Walbridge, Ohio, subsidiary of GEM Inc. The parent company has manufactured the turbines in Chatsworth, Calif., since the early 2000s, and awareness of this biogas option is slowly building, Damstra says. More than 50 units currently are operating in Ohio, Michigan, Indiana and New York.

The 40,000 gallons of low-BOD water that flows out of the digester each day proved a boon to the community, which was mandated to address sewage waste in 2009. The added effluent helps move residential waste to a treatment plant 5 miles away and helped rationalize an upgrade to the plant. "In a rural area, we almost have to create our own infrastructure," Ellis notes. He calculates the biogas-to-electricity project will realize a 42-month payback.

Pearl Valley produces a dozen varieties of Swiss and Colby cheeses, with a daily output of 25,000 lbs. of branded and copacked product.

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