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Double S Dairy
| Location |
Markesan, Wisconsin |
| Project Type |
Farm Scale |
| Animal Type |
Dairy |
| Population Feeding Digester |
1,100 |
| Baseline System |
Storage Lagoon |
| Digester Type |
Mixed Plug Flow |
| System Designer |
GHD, Inc. |
| Biogas Use |
Cogeneration |
| Generating Capacity |
200 kW |
| Receiving Utility |
Alliant Energy, Inc. |
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GHD Inc.
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Double S Dairy produces approximately 33,000 gallons of manure each day. In 2002, farm owners decided to utilize the waste and installed a mixed plug flow digester. The digester is an underground concrete structure with a fixed cover. The system has a mesophilic, U-shaped design that induces mixing and return of activated sludge.
A 200 kW Caterpillar engine-generator set burns the collected biogas and generates electricity and heat. All electricity produced on the farm is sold to Alliant Energy under a sell-all contract. The contract with the utility company includes the ownership of environmental attributes from generation. Captured heat is used at the facility to warm the digester, milking parlor, shop, and swimming pool.
Manure solids are separated from digester effluent by a screw press separator and used for on-farm bedding. Owner Dan Smit believes that the digester system is “environmentally positive” and comments that systems are getting more refined and are constantly being improved.
Double S Dairy’s digester project includes the following benefits:
- Electricity production
- Savings on bedding costs (~$30,000/year)
- Potential revenue from the sale of excess energy
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