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Dane County community digester
Wisconsin hopes for cleaner lakes with Cow Power investments |
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Written by Tony Kryzanowski
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It only takes one look at the foam cheese heads among fans at a Green Bay Packers game to realize how proud Wisconsin is of its dairy industry. Now, it can take pride in something else – how it is trying to responsibly manage the waste generated by that industry.
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Power produced from biogas captured from these three Dane County, Wis., digesters will produce $2.2 million worth of power per year. Submitted photo
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Power production has just started at Dane County’s new “Cow Power” facility, where three million gallons of liquid manure from three dairies is gathered in one location and processed through an anaerobic digester operated by Clear Horizons LLC. The biogas captured by the anaerobic digestion process is burned as fuel to generate power. The power generated from this facility will produce about $2 million worth per year of electricity and enough power for 2,500 homes.
This is the second facility built and operated by Clear Horizons in the state, but the first that combines liquid manure from three dairies. In addition to treating the liquid manure from three dairies, the $12 million facility also uses cutting-edge phosphorus removal technology. It removes 60 to 70 percent of the phosphorus in the nutrient-rich liquid stream coming from the digester, which is piped back to the dairies for their use in irrigating cropland. This was a major driver behind the construction of the facility, as a number of Wisconsin residents were concerned with how runoff from raw manure applied on cropland was influencing the health of local lakes and rivers – particularly the Yahara Chain of Lakes that includes the Lake Mendota watershed.
Phosphorus in the manure is believed to be the leading cause of algae and weed growth in Dane County’s lakes.
The State of Wisconsin made a $3.3 million contribution to the installation of the Centrisys centrifuge separation technology that removes phosphorus from the liquid stream. The same amount has been approved for a second Cow Power facility planned for Springfield Township, with construction expected to start in spring, 2012.
“The Centrisys system has operated very well,” says Clear Horizons representative Leo Maney. “It is one of the things we are most pleased with at the Dane County digester. Their equipment has operated the best, and they have been very supportive of us. This is one of their first ventures into the manure waste energy market.”
He adds that at this point, the facility is meeting and exceeding the amount of phosphorus removed as required by Wisconsin’s Department of Natural Resources. The contribution from the state also was a major contributor to the economic viability of the project.
“Our Cow Power project is a victory for family dairy farms and our lakes,” says dairy farmer Chuck Ripp, one of the three farmers that have signed up to supply the Dane County digester. “Agriculture can help to keep our lakes blue while creating green energy that will help sustain Dane County’s important economy.” In addition to improving the quality of local streams and lakes and creating valuable byproducts, the air also smells a lot fresher around the three dairy farms participating in this project.
The second Cow Power facility in Springfield Township near Middleton that will involve the gathering of liquid manure from four dairy farms and processing through an anaerobic digester is awaiting final approval from Dane County. Clear Horizons will also construct and operate that facility.
To put the importance and influence of the dairy industry in Dane County into perspective, county executive Kathleen Falk says it’s a $700-million-per-year industry that employs about 4,000 people. While dairy is big business in Dane County, she estimates that the 400 dairies in the county that are milking about 50,000 cows are also generating about two billion pounds of manure per year.
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Clear Horizons is a company making a name for itself for not only building anaerobic digesters that produce biogas for power production, but also operating the sites. Submitted photo
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The county invited companies to offer a solution to solve its issue with nutrient runoff into area lakes and streams, and local company Clear Horizons came out the winner. The company had several advantages going into the competition. It offered a total solution of both building and operating the facility. All the dairy farms had to do was manage and collect their liquid manure streams in tanks located on their farms to the company’s standards, and Clear Horizons took care of the rest, including the construction of pipelines from the on-farm collection tanks to the centralized anaerobic digester. The liquid manure is stored in a holding tank at the digester location prior to processing. The participating dairy farms can also truck more solid manure to the facility where it is ground and agitated into the Clear Horizons holding tank. The company also had an edge in the competition because it already had the experience of building and operating an anaerobic digester and biogas power plant at Wisconsin’s Crave Brothers Dairy.
Maney says that having the opportunity to build and operate the Dane County facility was tremendously beneficial for the company. It gave them the experience of not only designing, building and operating a power-generation facility from a single dairy, but now gathering manure from a number of dairies at an anaerobic digester and biogas power plant in a central location. The Dane County digester is also about one-third larger than the Crave Brothers Dairy digester, and consists of three digestion tanks. In addition to size, another major difference between the Dane County and Crave Brothers installations is where the equipment came from. Because Europe is more advanced in its development of power generation from biogas, a lot of the technology used at Crave Brothers came from Germany, which presented its own challenges from a language and time zone perspective. Clear Horizons made a conscious effort to “buy American” for the Dane County facility, which not only supported the local economy but also made the facility easier to install and service.
The challenge for Clear Horizons as it relates to using the biogas to generate and market the power is on the operational end, as it has considerable technical experience and resources to design and build these facilities. Operating them is a relatively new venture, and Maney explains just how challenging a task it can be. In the case of working with a number of dairy farms that provide liquid manure to a central location, firstly they must all be within reasonable proximity to a centralized anaerobic digester for the project to make sense. Then there are the agreements that must be put in place for a project to proceed. This includes long-term agreements with individual dairy farms to ensure a steady supply of raw material, as well as with power purchasers such as Alliant Energy, which has agreed to purchase the power generated by the Dane County Cow Power facility. Failure to reach accord on any one of about 10 agreements required per facility will bring the project to a standstill. Also, in the case of several dairies supplying one facility, the dairies have to be practically within view of the centralized digester for the piping of the liquid manure to the facility to make economic sense.
What has helped Clear Horizons pursue business opportunities in the state is the objective Wisconsin has set for each conventional power provider to deliver a set percentage of its power from alternative energy. The challenge, says Maney, is to have legislators treat power generation from biogas with the same attractive power rates that are offered to the solar and wind industries.
Clear Horizons derives its income from a variety of byproducts generated by the anaerobic digestion process, which generates gas, liquid and solid byproducts. The gas is burned to generate power. The nutrient-rich liquid is piped back to the farms for use in crop irrigation. A portion of the solid byproduct, which is converted into compost is sold back to the dairy farmers as bedding. The remainder is sold to a fertilizer company.
The raw manure is agitated within the anaerobic digester tanks to encourage the biological anaerobic process that produces the biogas that rises to the top of each tank, where it is piped to the gas clean-up system and then burned in a GE Jenbacher power generator. The manure stays in the tank for 20 to 30 days and then is pumped from the tank into the Centrisys centrifuge separator where the liquids are separated from the solids and most of the phosphorus is removed from the liquid stream. The liquids are transported back to lagoons on the dairy farms where they are used for irrigation. The solids proceed into either a drying or composting operation.
Maney says the anaerobic digestion mix includes the addition of various fats, oils and grease substrates, mostly from restaurants, to improve biogas production. This may in fact represent an additional future income stream for the company, as it can charge tipping fees to accept this material.
He concludes that the Clear Horizons business model of building and operating anaerobic digesters and biogas power plants, which is rather unique within the biogas power generation sector of the alternative energy industry, is working well for the company and is profitable.
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