February 13, 2002 ISSUE #M22
An extremely smooth start-up has taken place at the Matlink Farm in Clymer, New York. Owned and operated by Ted Mathews, the farm has installed a manure digester and electricity generating system designed by RCM (Resource Conservation Management, Berkeley, California, 510-658-4466). The system employs a 660,000 gallon stirred pit digester. Manure from the 1,200 head dairy is scraped and pumped to the concrete pit.
Digested manure floats over a weir and into a secondary pit. The manure in this secondary pit is pumped to a Vincent Model KP-10 screw press. In normal operation the press dewaters the manure at the rate of 120 cows per hour.
Methane from the digester is burned in a Waukesha internal combustion engine. This engine is coupled to an induction type electric generator. The rating of this generator is 130 kilowatts (175 hp), at which rate the system is currently operating.
Waste heat from the motor that drives the generator is used to heat the digester. Cooling water from the radiators is circulated through the pit so as to maintain a temperature of approximately 100° F.
Circulation is maintained in the digester with a pair of sidethruster propeller pumps. These are positioned diagonally opposite in the sides of the pit.