Blast destroys roof of troubled biodigester near Waunakee

Aug 7 - McClatchy-Tribune Regional News - Steven Verburg The Wisconsin State Journal

 

A 1.25-million gallon manure digester near Waunakee won't resume operations until authorities determine the cause of an explosion and fire that destroyed its outer roof early Wednesday, sending up a plume of smoke visible for miles.

The blast was the latest in a series of problems at the Clear Horizons LLC biodigester, which generates electricity by burning methane that bubbles out of farm manure.

Records released Wednesday revealed previously undisclosed difficulties, including a storm water filtration basin that was rendered useless when a manure spill flooded it in November, pipeline blockages that have forced digester shutdowns, and hundreds of thousands of gallons of animal waste that has gone untreated.

In addition to generating power, the plant is designed to reduce phosphorus in the manure so that when it's spread on farm fields, less of the nutrient is available to run off and spur growth of foul-smelling algae and weed growths in lakes.

Wisconsin Department of Natural Resources officials have met twice this year with Clear Horizons over alleged violations involving the company's previously reported failure to remove enough phosphorus from the waste, and to discuss three spills that released more than 400,000 gallons of manure in the last nine months.

The DNR could levy fines up to $1,000 a day for violations, or shut the plant down by revoking its permit, but those penalties aren't being discussed, agency wastewater specialist David Mosher said. "Definitely things like this have come up too often," Mosher said of the plant's troubles. "Right now we're just looking for avenues to get them in compliance with the permit."

The explosion and fire destroyed a $250,000 nylon inflatable cover over one of the three digesters on the site, said Dane County Sheriff's Office spokeswoman Elise Schaffer. No injuries were reported. Crews from Waunakee, Dane and DeForest fire departments responded.

Employees had emptied the digester so they could clear material that was blocking flow to an underground pipe, and on Wednesday were preparing to remove water that had accumulated between the outer cover and an inner roof below it, said Jim Ditter, chief executive officer for PPC Partners Inc., which owns Clear Horizons.

The explosion and fire happened as an employee on the ground started an electric blower, leading to speculation that it somehow ignited methane gas, Ditter said. He said the digester will remain out of commission until officials are sure it's safe to operate.

Ditter said blockages have caused shutdowns before, and the two other units are both in need of cleaning. A crucial outflow in one is plugged now, Ditter said.

Shutdowns mean the three large dairy farms that use the digester must instead deposit their manure in lagoons, and eventually spread the full phosphorus load on fields, DNR officials told the company in a May 22 conference. A summary of the meeting was released Wednesday.

Because of lowered capacity at the biodigester in July, one farm stopped its flow to the digester for 10 days, and another for 14 days, the company reported to the DNR. Daily average flows of manure with full phosphorous content going into farm lagoons ranged from 22,500 gallons to 76,000 gallons per farm, the reports indicate. Full capacity flow into the biodigester varies, but the daily average from all farms was 111,000 gallons in October, the month before the spills started, Mosher said.

Ditter said it has been costly for his company to search for solutions to the spills, blockages and inadequate phosphorous reduction.

"From our point of view it's been a huge investment, but it's been a huge plus for Dane County just in terms of the phosphorus we've removed and kept out of the lakes," Ditter said.

Clear Horizons built the digesters at 6321 Cuba Valley Road in the town of Vienna in 2010 for $12 million, including government subsidies.

In March, the DNR told the company to increase staffing, and to provide better explanations for spills and the plant's worsening record for reducing phosphorus.

The plant's state permit requires removal of 60 percent of phosphorus from manure before it is spread on fields. Clear Horizons averaged 63 percent in 2011, 56 percent in 2012, 44 percent last year and 33 percent through June 7 this year, company reports indicate.

The company said it was considering new equipment that could do a better job of reducing phosphorus.

The facility's woes began coming to light in November, when a short length of curved pipe near a pump house burst and 380,000 gallons of manure poured out. Some followed ditches more than a mile to Six Mile Creek, but no significant pollution was detected in the water, county officials have said. In January, another pipe failure in the same spot loosed 22,000 gallons. Unlike the first spill, employees were on duty to stop the flow.

On Jan. 29, the DNR alleged that the company violated its permit. On March 12, a day after the DNR and the company met formally to discuss the allegations, a different pipe ruptured and released about 35,000 gallons. A second violation notice was issued March 25 to cover the March spill and a new report showing substandard phosphorus reduction in 2013.

Ditter said the company has installed some new valves and alarms, among other improvements, and scheduled staff on site around the clock.

State Journal reporter Bailey Berg and Bill Novak of madison.com contributed to this report.

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