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Five Star Dairy Farm

Location Elk Mound, Wisconsin
Project Type Farm Scale
Animal Type Dairy
Population Feeding Digester 850
Baseline System Storage Lagoon
Digester Type Complete Mix
Co-Digestion Substrate (high-fat food wastes such as greases and oils)
System Designer Microgy
Biogas Use Cogeneration
Generating Capacity 775 kW
Receiving Utility Dairyland Power Cooperative; Stargest Power, LLC

Farm Bill Funded Project

Aerial photo of centralized digester at Five Star Dairy

Photo: Cornell University

Five Star's owner acquired the benefits of anaerobic digestion through an agreement with Microgy, Inc. and Dairyland Power Cooperative. Microgy provided a complete turnkey digester, including development, construction, financing, and ongoing operation and maintenance. With Microgy providing financing, Five Star did not have a large cash outlay. Dairyland Power buys the resulting biogas and owns/operates the engine-generator set to generate electricity. Five Star pays off the debt on the digester through biogas sales to Dairyland. The agreement served as a business model for similar projects at Norswiss and Wild Rose Dairies.

Operational since 2005, the above-ground complete-mix digester operates at a target temperature of 125°F. Manure is scraped three times per day from the barns. A mixture of manure and about 10 percent food wastes is batched into the digester every half hour. High-fat wastes such as greases and oils enhance biogas production and are integral to the Microgy design. Five Star Dairy maintains a separate storage tank for food processing wastes.

Solids are separated out after digestion. Most of the solids are used for bedding and some are given away to local gardeners. The project includes the following benefits:

  • Provides revenue from gas sales and carbon credits, which allow Five Star to pay down the debt on the digester
  • Provides Dairyland Power Cooperative a competetively priced renewable energy source for their customers
  • Provides digested solids free to the community, which meets a growing interest in using digested solids for gardening and enhances the farm's image
  • Reduces odor significantly

It really reduces odor (and methane emissions) of the manure and it's another income stream.
—Lee Jensen, Five Star Dairy, quoted in an Environmental Power fact sheet

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