Farm Power: Turning manure into renewable energy


Biodigesters are a double win - they allow dairy farmers to better manage cow waste while creating a renewable energy source. The challenge for many dairy farms is size - most are too small to successfully develop and operate a biodigester on their own.

But brothers Kevin and Daryl Maas have figured out a solution. Their company, Farm Power, works with groups of dairy farmers to design regional digesters that serve multiple farms. The brothers' mission is to support dairy farms that are located close to the cities and suburban communities that drink their milk.

"It's more sustainable to keep the food supply near where people live," said Kevin Maas, Farm Power co-founder.

The brothers do all the legwork, including designing the project and raising the funds. "We want to make community digesters work for farms that are too small to do it themselves," said Daryl Maas, Farm Power co-founder. Smart Energy is a proud investor in Farm Power's first two projects called Lynden and Rexville, both located in Northwest Washington.

The Rexville digester pumps cow waste from two dairies into a one million gallon tank, where it is heated to 100 degrees. The heat causes bacteria to grow, which produce methane. The methane is sent to an engine that turns a generator and creates 750 kW of power - enough to power 500 homes annually. The waste heat is used to warm the digester tank.

The electrical efficiency of the digester -- about 35 percent -- is similar to that of a coal- or nuclear-powered plant. But the heat from running the methane-powered generator, which would be wasted at most power plants, is put to good use; in Lynden, surplus hot water even goes to the radiant floor heating system in a neighboring greenhouse.

The process also produces a high-quality liquid fertilizer and animal bedding, leaving nothing to waste. It's a closed loop system that turns waste into useful materials and saves the dairy farmers about $100,000 per year on animal bedding.

"The animal bedding produced by the digester process is better quality than sawdust," Kevin said. "It's softer and healthier, and cow health is invaluable to the farmers."