October 25, 2010 | General

Anaerobic Digester Installations Accelerate

BioCycle October 2010, Vol. 51, No. 10, p. 50
Facilities recently permitted or under construction illustrate range of applications for AD technologies in North America.
Nora Goldstein

WITHOUT a doubt, the pace of adopting anaerobic digestion to process a wider variety of organic waste streams is picking up in North America. The University of Wisconsin-Oshkosh broke ground in mid-September on a facility that will digest campus dining hall residuals with municipal yard trimmings. In Iowa, a draft construction permit for a planned cattle confinement operation in Scott County was issued to Glenora Feed Lot in early October, paving the way for installation of the first digester system on a CAFO in that state. And in Ontario, a septage treatment digester is starting up, providing a much-needed alternative to land application of that material.

Construction of the nation’s first commercial-scale dry fermentation anaerobic digester got underway last month on the campus of the University of Wisconsin in Oshkosh (UWO). The facility, which is installing the BIOFerm technology, is designed to process 8,000 tons/year of source separated organics (SSO), primarily food waste and yard trimmings, from the campus and the community.
The facility will include heat and power generators, expected to produce up to 10 percent of the campus’ electricity and heat. “This state-of-the-art biodigester will take the University further in its goal to become energy independent,” says Tom Sonnleitner, Vice-Chancellor for Administration.
The Oshkosh campus is divided by a river, with most of the campus on one side; the digester will be on the other side of the river, adjacent to the Campus Services Center. “The city’s wastewater treatment plant is directly across the street from the services center,” says Caroline Chappell, Application Engineer, with BIOFerm Energy Systems. “Right now, the treatment plant flares the biogas from its digester during the summer months. Once the university’s plant is operating, that biogas will be piped to UWO’s CHP system during the summer, boosting heat and electricity output.”
Four digester chambers, each with processing capacity of 2,000 tons/year, are being installed inside a building that also houses the tipping floor. Retention time in the chambers is 28 days. A front-end loader will be used to load and unload the tunnels. The building will be under negative pressure, with air treated through a biofilter. “The facility will probably start out with about 6,000 tons/year, and then increase to its capacity of 8,000 tons/year as more experience is gained and additional feedstocks are secured,” adds Chappell. “The university is still deciding where the digested material will be composted. One option is an area farmer, who may also provide feedstock for the digester.”
The project is a collaboration with the UW Oshkosh Foundation, which purchased the land. It will be partially funded with a grant of $232,587 from Wisconsin Focus on Energy and a $500,000 grant from the federal government. Commission of the facility is scheduled for next spring, with startup in the summer of 2011.

Bryan and Lisa Sievers of Sievers Family Farms have a cattle finishing operation at their Glenora Feed Yard near New Liberty, Iowa. When they decided to expand the feed yard from about 700 head/year to 4,888 head/cycle (with up to 9,500 head annually), the Sievers needed to go through the Iowa Department of Natural Resources (IDNR) confined animal feeding operation (CAFO) permitting process, as well as the USDA Rural Development Environmental Assessment as part of their USDA Rural Energy for America Program (REAP) grant application. Enhanced manure management was a key requirement of the permit application and environmental review – and one that the Sievers achieved in part by their decision to install an anaerobic digester (AD). “While the IDNR does not require AD in its CAFO permitting process, the addition of the digester made a significant difference in gaining IDNR’s and the community’s approval,” says Bryan Sievers.
On October 1, Glenora Feed Yard received a draft construction permit from IDNR, which includes the go-ahead for the CAFO and digester. The Sievers selected the DRANCO Farm Digester (DFD) technology, a thermophilic, high solids anaerobic system developed by Organic Waste Systems, Inc. (OWS). A single digester silo with a conical bottom is being installed, with a capacity of about 850,000 gallons or about 45,000 tons/year. “The DFD is an adaptation of the DRANCO high solids digester typically used for municipal solid waste streams,” says Norma McDonald, North America Sales Manager for OWS. “This will be the first DRANCO Farm installation in the U.S.”
The bedded pack beef manure (about 20-30% solids) will be codigested with corncobs, cornhusks, soybean stubble and hog manure. “We are permitted for the kinds of materials we would use as bedding in cattle barns,” says Sievers. “We also are looking at adding hog manure to maintain a 20:1 C:N ratio in the digester.” The digester will operate right around 38 to 40 percent solids, with material exiting the digester between 20 and 25 percent solids. The Sievers plan to use the digested material for fertilizing cropland and animal bedding.
The project is being funded in part with a grant from Alliant Energy’s “Farm Anaerobic Digester Cash-Back Reward.” The reward amount is 50 percent of the cost of the system, up to a maximum of $200,000 per project. The interconnection for the power generated must be through Alliant Energy (if applicable). “We expect to receive $200,000 in grant funds from this cash-back reward program,” says Sievers. “It’s a brand new initiative on the part of Alliant Energy.” The CHP units being installed at the feed yard can generate up to 1.4 MW of electricity annually. McDonald expects that the project will break ground before the end of 2010, with operation getting underway in 2011.

An anaerobic digester designed specifically for septage waste is being commissioned this month in the southern Ontario townships of Georgian Bluffs and Chatsworth. “It is a relatively small plant, and the first of its type in Ontario,” says John Haanstra, Senior Vice President of Maple Reinders Group based in Mississauga. “The facility was permitted under a wastewater Certificate of Approval. There has been a movement to end application of septage on fields, and this digester provides an alternative management option.”
Maple Reinders partnered with CH4 Biogas, Inc. to design and build the roughly $3.5 million plant. Corn stover is being used as a codigestion substrate. Operations are underway with a seed sludge, and some biogas is being generated, adds Haanstra. “We expect to be introducing septage in a couple of weeks.” The plant is expected to significantly reduce the odors associated with septage, and destroy pathogens. It was funded in part with $833,334 from the Building Canada Fund.
The digester is in a fairly remote area and the existing electric distribution network is not sized to take in additional power. “We are only putting in a 100 kW generator initially but plan to increase to a 400 kW unit once the plant is up and running and the local authority upgrades the distribution net,” he says.

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