In 2007, Crave Brothers Farm in Waterloo, Wis., contracted with Clear Horizons LLC to build the first of their two digesters to help them deal with manure from their dairy herd of 1,000 cows and young stock. The farm grew to that size over the years as new family members joined in the operation and brought their cows from neighboring farms to the main farm (see "Crave Brothers Farm"). Today, the Crave's animals produce 50,000 gallons of manure per day. The manure goes into the digesters and produces several useful byproducts, including: | | More than 300 homes are powered each year from the energy generated by the Crave Brothers digester.
| - a natural liquid fertilizer, which is used on the farm's fields according to a soil nutrients plan
- a solid waste that is used to produce organic potting mix
- solid material with a sawdust-like consistency, used to bed all the cows on the farm
- biogas that is fed into a generator and sold onto the local utility grid (the Crave's cows produce about 5,000 MWh per year—enough to power more than 300 homes)
- heat captured from the generator that is used to warm the digester and displaces fossil fuels normally used to heat farm buildings and water for the dairy operation
Charles Crave, who oversees the farm's financial matters, estimates an eight- to ten-year pay-back on the digester equipment investment. But the Craves have their eye on the big "green" picture. "The digesters are a perfect opportunity for us to be good to our soil, our cows and our neighbors," Charles says. He further explains, "The liquid fertilizer we use now is better for the soil after it's been digested. The cows are more comfortable with the digested solids bedding than sand bedding. And the digestion process removes the odor from the manure, so visitors to our farm and our neighbors are happy."
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