October 19, 2011 | General

Commercial Digester Moves Ahead In South Carolina

pre and postconsumer food wasteBioCycle October 2011, Vol. 52, No. 10, p. 42
Developer in the Southeast has begun construction of a 48,000 tons/year facility to process food waste, grease and yard trimmings.
Nora Goldstein

DANIEL Rickenmann, a former restaurateur turned anaerobic digester developer, has pulled together a team to build, own and operate commercial digesters to process source separated organics into renewable energy and soil amendments. His company, W2E Organic Power, has begun construction of its first anaerobic digester in Columbia, South Carolina. The plant is designed to process 48,000 tons/year of pre and postconsumer food waste, solid and liquid grease and some yard trimmings.
“The site is in the middle of an industrial park and backs up to the city of Columbia’s green waste composting facility,” says Rickenmann. “It’s located about 4.5 miles from the State Capitol building in an urban setting. We’ve had great support from the community. Most of the questions we have received, even during the public notice process, have been ‘can the community take advantage of the by-products?'”
W2E Organic Power selected EISENMANN as its AD technology and engineering provider, and brought in CIYCOR, a global renewable energy and construction company, as codeveloper and financial partner. W2E has commercial organics feedstock commitments from a range of generators and waste haulers, including produce markets, health care systems, Quest Recycling, Walmart and a food bank. Electricity generated from the biogas will be fed into the grid and purchased by Santee Cooper, South Carolina’s state-owned electric and water utility, under a long-term power purchase agreement (PPA). Additional PPAs are being considered for natural gas pipeline injection. W2E’s long-range plan is to upgrade the biogas to compressed natural gas.
“Having the long-term feedstock commitments, a permitted site and the PPA in place – in other words, a completely developed project – is what made CIYCOR secure in its decision to finance the project,” explains Rickenmann. “And because construction is underway, the project will qualify for Section 1603 [U.S. Treasury] funding of 30 percent of the capital costs.” Total project costs are around $25 million. Facility start-up is scheduled for the third quarter of 2012, with full operation by the fourth quarter, he adds.

To evaluate anaerobic digester technologies, Rickenmann interviewed about a dozen companies in Europe. “I was looking for a technology provider that had built multiple locations to see how each facility evolved with operating experience of the previous one,” he explains. “I wanted to know what investment the manufacturer has put into improving their system. What have they learned? What are their target waste streams and how are they being processed?”
EISENMANN facilities in Europe, along with its package of technologies, appeared to be the best match for what Rickenmann had in mind. “One of the hot issues in terms of organic waste processing and digestion is depackaging,” says Adam Halsband of EISENMANN. “That is something we have a lot of experience with and spent a lot of time discussing with Daniel. What is the range of feedstocks he will be receiving and what level of pretreatment is required? We wanted to give him the most flexibility as possible on receiving feedstocks. The Columbia facility can receive a wide range of materials – from very low solids to up to greater than 40 percent solids.”
Four feedstock receiving channels are being installed at the Columbia plant: food waste, grease trap solids, liquid grease and yard trimmings. Each receiving channel is directed to the main digester. “Each has its own surge capacity and preconditioning equipment is only needed for the food waste receiving channel,” adds Halsband. “This provides the most flexibility as far as materials receiving is concerned, and enables the operator to optimize the blend to increase biogas yield. It also allows W2E to optimize its materials handling costs. If they don’t need preconditioning equipment for each feedstock stream, they are saving a lot of money.”
The anticipated “recipe” will be 70 percent pre and postconsumer food waste, 25 percent grease trap (interceptor) waste streams and 5 percent yard trimmings, notes Rickenmann, adding that paper is not being taken “on purpose but probably some will get in here by accident.” The yard trimmings will be ground before arriving at the facility. Final mixing of feedstocks occurs in the horizontal plug-flow digester.
The facility is entirely enclosed and has an odor treatment system. Trucks will unload directly into the designated hoppers, which are inside the building. “The garage doors will open, the trucks will tip into the designated hoppers, and then the doors will close immediately after the trucks exit,” says Rickenmann.
Following anaerobic digestion, the material will pass through a solids separator. W2E Organic Power has lined up two commodity growers who will be purchasing the digested solids for a soil amendment. The liquid fraction will be stored in a tank and utilized as a fertilizer.
W2E and its partners plan to build facilities elsewhere in the U.S. Rickenmann says that six additional projects are in various stages of permitting and planning in the Southeast and mid-Atlantic regions. He notes that 16 years in the restaurant industry gave him first-hand familiarity with the food waste and grease that the Columbia project will be receiving: “I ran a variety of restaurants and understand the waste streams we have available.”

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