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After Explosion, Digester Repaired

by Kelsey Thalhofer
Capital Press, January 10, 2013

Facility back in operation; insurance paid for most repairs

AUMSVILLE, Ore. -- Tim Bielenberg was working with draft horses at his Aumsville, Ore., farm July 25 when he got a call that the dairy digester on his land had exploded.

"I came over the hill and saw the second tank go off," Bielenberg said of the low-temperature anaerobic digester that had been converting manure into a power source on his Oak Lea Farm since last January. As the heat of the south tank's fire melted the top of the north tank, methane gas escaped and produced the second explosion.

"It was pretty spectacular." Bielenberg said. "Your heart kind of jumps, and there's not much you can do."

No people or animals were harmed in the incident and damage to the tanks was minimal, but the black smoke attracted news cameras and questions about the unique digester.

The digester's owner, Washington, D.C.-based Revolution Energy Solutions, believes the fiery blast was caused when methane gas began to leak from the rubbery top of the south tank and caught a spark. The source of the spark is still unknown, though the company speculates that the dry summer air may have produced a static charge that ignited the gas.

"We've taken measures to ground static charges," said Alan Tank, RES founder and chief executive officer. Though he believes the chance of a static charge igniting the tanks is as rare as a cell phone igniting a gas station, he said his company has grounded all of its digesters since the incident. "We don't want it to happen again."

The company repaired the tanks' rubbery tops, gas risers and insulation, which were damaged in the incident, and repainted the tanks.

"If you went there now, you couldn't even tell there was an event," Tank said. Most of the damage costs were covered by insurance.

The digester was back to full operation within a few weeks of the incident, processing up to 30,000 gallons of manure a day to create methane gas, which then fuels generators to produce up to 190 kilowatts of electricity. The 1.5 million kilowatt-hours it produces annually are enough to power Oregon 150 homes for a year.

The company introduced the low-temperature anaerobic digesters to the U.S. at Lochmead Dairy in Junction City, Ore., in November 2010. The Oak Lea digester is the second RES digester in the country, and since the incident the company has completed a 370-kilowatt digester at Forest Glen Oaks Dairy in Dayton, Ore. Tank said RES will focus on swine operations in North Carolina in 2013, and the company hopes to bring another dairy digester to Lane County, Ore., as well.

After that explosive day in July, Bielenberg, who milks 325 cows and also raises dry cows and heifers, holds that the digester on his farm is an impressive piece of green technology, and the incident was rare.

"It's really simple, fairly clean," he said of the digester. "The accident should have never happened."

Kelsey Thalhofer
After Explosion, Digester Repaired
Capital Press, January 10, 2013

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