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March 2007

Digesters put energy back into industry

California-based Onsite Power Systems Inc. is confident that anaerobic digestion technology and digesters can be employed across the United States and Canada by municipalities and the agricultural and food processing industries.

Onsite develops and manufactures anaerobic digesters.

“We have at least 20 digesters lined up in California alone,” says Dave Konwinski, Onsite’s CEO. “There is a big market for this. We have one client in the food processing industry and they have identified about 2,000 plants across the United States that can handle a digester right now. The system is very scaleable – we can size it to fit a food processing plant, take their waste stream on-site and put the energy back into their plant.”

Waste Systems Technologies Inc., the firm that contracts organics waste collection for the City of Industry in Los Angeles County, plans to spend $400,000 in preparation to establish a digester based on the experimental system at UC Davis.

Waste Systems’ president Jeff Duhamel expects that the digester will cost $2 million to construct. Industry and the City of Los Angeles use the same landfill, which is expected to close in 2013.

Duhamel notes that once the landfill is closed, he expects that his firm will have to ship garbage 200 miles by either train or truck to a new landfill located in the desert. This method could cost between $60 and $80 per ton.

He adds that a digester could reduce costs to $30 per-ton based on the use of fuel produced by the digestion process to power his fleet of vehicles.

Last year the Los Angeles Department of Power and Water (LADPW) cancelled a contract with BioConverter LLC, a contract approved by the Los Angeles city council in 2004, to build a biogas power plant/digester-type facility that would have provided the city with 40 megawatts of electricity daily.

The power, produced by converting 2,700 tons of waste per day, would have powered close to 40,000 homes. The LADPW would have paid approximately $16 million annually for 20 years starting in 2008-09.

“We terminated that agreement due to a lack of progress in meeting the performance objectives of those contracts,” says Randy Howard, the assistant chief operating officer of the LADPW. “We were very disappointed. We have a viable green waste stream and there is a great opportunity. We believe that we will get at least one or two new anaerobic/biogas projects because the fuel source is here and it’s just a matter of technology and a company capable of developing it.

“The city already separates green waste,” he adds. “We have separate containers for the pickup of garden waste – grass clippings, tree trimmings and plants. Currently food waste is put into the solid waste stream.”

In addition to the power, the project would have boosted the city’s recycling program by establishing a local market for processing green materials.

However, the LADPW has put forward a new Request for Information (RFI) seeking 2.2 gigawatts hours annually of electricity derived from renewable resources.

“It’s approximately 10 percent of the requirements for the City of Los Angeles and we are committing about $176 million a year to procure this energy,” says Howard. “The RFI is for all kinds of renewables – wind, geothermal, solar, solar thermal and biogas. We have a goal that 20 percent of all our electricity requirements be generated by renewable resources by 2010.”

“We’ve talked to a lot of areas that are interested,” said Konwinski. “We work with a lot of state agencies. In California the Integrated Waste Management Board (CIWMB) manages every bit of solid waste in the state. Fifty percent of the diversion from all landfills has to go to a qualified technology to get your diversion credit. Right now, for organic material, the only certified process is compost. However, the CIWMB has recognized anaerobic digestion as 100 percent certified.”

He adds that a digester can handle just about any product that is organic. This includes: grass clippings, collected food waste, animal fat, manure and agricultural and food waste.

Because wood does not digest well, digesters stick to grass clippings, trimmings, leaves and garden plants.

Konwinski says that a digestion system can pay for itself in 3 to 3.5 years because Onsite uses standard off-the-shelf components and state-of-the-art automated control systems, which reduce the manpower needed to operate the digester.

The payback comes from offset tipping fees and the conversion of waste, especially from food processing plants, into energy.

“You get about $22 to $25 worth of energy per ton,” says Konwinski. “We have a huge potential in the Midwest, states such as Iowa, Wisconsin and Minnesota - areas with food processing and pulp and paper plants.

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