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2012 North American Manure Expo and Dane County Digester Tour

Fri, Jan 18th, 2013
Posted in All Agriculture

Dawn Bernau and Katie Richards with digesters in background. Photos submitted

Dawn Bernau and Katie Richards, Nutrient Management Specialists – SE MN Area 7

On August 21st the SE MN Nutrient Management Specialists Dawn Bernau and Katie Richards toured the Dane County Community Anaerobic Digester as part of the 2012 North American Manure Expo held in Prairie du Sac, Wisconsin August 21-22, 2012. The Dane County Community Digester is the only operating community digester in Wisconsin. Three dairies contribute to this digester and it is owned and operated by Clear Horizons, Inc. This is a unique strategy in which the company owns and operates the digester and the producers contribute manure as feedstock. This is also a unique situation to have three dairies so close together each being within 2000 feet of the digester. The three dairies total 3,000 animals. The manure from each farm is pumped through underground pipes into a reception tank at the digester site. The manure is then fed into the digester with additional substrates which are trucked to the facility.

What does the digester consist of? It is comprised of three general collection systems: 1) Figure 1, underground manure lines to a reception tank; 2) Figure 1, an above ground tank for storage of additional wastes; and 3) Figure 2, a below ground open pit for manure and additional feedstock reception. In Figure 3 there are three digestion tanks, Figure 4 two 1MW generators, Figure 5 a solid/liquid separation system, and Figure 6 the control room.

What are the digesters fed? They are fed a blend of organic feedstocks. The majority of the feedstock consists of the manure from the dairy farms, about 90 percent by volume. The additional 10 percent is other organic feedstocks such as food waste. The three 1.2 million gallon digester tanks (figure 3) produce the biogas which rises to the top of the digester tank that has storage within the inflated roof. The biogas produced is then sent to the two 1MW generators (totaling 2MW)(figure 4) where it is used to produce electricity. The electricity is sold to the local utility. The Dane County Community Digester produces enough electricity to power approximately 2,500 homes. Following digestion, the digestate is sent to the solid/liquid separator where the solids are removed by a centrifuge (the only one used in the Midwest) and the liquids are sent back to a holding tank. The liquids have enough nutrients left in them to provide the three dairies with a good source of fertilizer for their crops. This liquid is pumped from the holding tank back to the three dairy farms through the underground pipes for the dairies to apply to their crops. The solids that are separated and dried (to remove the bacteria) by a dryer are sold for bedding and plant food. These solids are shipped out of the watershed the digester is located in to help remove the phosphorous from the watershed.

What are the pros and cons of a community digester approach?

A community digester approach is an option for facilities that are not large enough to produce the necessary feedstocks to achieve the economics of scale needed to be economically viable. However a community digester project can have complications versus a single owned operation including ownership of manure, biosecurity issues, transport, legal responsibilities, permitting issues and many more which can make the system more complicated to negotiate. With the Dane County Community Digester, the three farms are contracted to provide their manure to the digester, and contracted to accept in return 100 percent of the separated liquid following digestion from the manure they supply. Clear Horizons LLC owns the biogas and electricity produced. Clear Horizons is tasked with maintaining and operating the digester (manned with personnel nearly 24/7).

The Dane County digester has overcome many obstacles and is currently operating to produce renewable energy from dairy manure and other feedstock that was once thought of as waste. A digester such as this has great potential in the Midwest to increase renewable energy production while reducing the environmental footprint of livestock facilities.

Our trip to the Midwest Manure Expo on August 22nd was filled full of excitement and education. There were local representatives there from commercial applicators, equipment sales, Nutrient/Manure Management Plan writers, and Feedlot Officers. To name a few local reps: K&R Equipment, VCP Vorwerk Custom Pumping, Jon Schmitz Progressive Ag Center L.L.C. Nutrient Management Specialist, Virgina Westlie Goodhue Feedlot Officer, Katie Richards and Dawn Bernau, SE MN Nutrient Management Specialists. Local equipment sales and commercial applicators K&R Equipment had their equipment on display, and they were also featured in the manure pit agitation demonstration and liquid manure application demonstration (Figures 8 and 9). The expo also featured a solid manure application demonstration with around 25 different solid manure spreaders. The liquid manure application demonstration had six different applicators from drag line to tankers.

There were several presentations at the expo. A few of the presentations that we attended were: 1) Can Nitrification Inhibitors Improve the Nitrogen Use Efficiency of Manure; 2) Sand-Laden Manure: Handling & Separation; 3) Variability in Manure Nutrient Content & Sampling Strategies for Various Management Systems; 4) Innovative Manure Application Methods to Improve Nutrient Utilization & Reduce Environmental Impact; and 5) Using Precision Manure Management to Improve Water Quality in TMDL-Identified Problem Areas.

Overall the Midwest Manure Expo was a very fun filled and educational day for all who attended. I highly recommend that producers attend this in the future who are interested in new manure application technology and managing their manure in an economical and environmentally friendly way. You are bound to learn at least one new thing and maybe even win a door prize.

February 26-27th will be the Midwest Manure Summit; check their website for details The early registration deadline is February 18, 2013. Other upcoming meetings for livestock producers to attend entitled “Will Grid Soil Sampling Work for my Livestock Farm?” will be held on January 22nd at Good Times restaurant in Caledonia at 1pm and January 23rd at Lewiston Community Center at 10am. These meetings are put on by U of M Extension speaker Randy Pepin, Extension Educator. Contact Jake Overgaard Winona County Extension Educator to pre-register, or call 507-457-6440.

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