Cow Poop & Food Scraps...Organic Materials In, Electricity Out
Barstow's Longview Farm has a herd of 450 animals. 250 are milking cows and the remaining are young replacement stock and steers. The barn housing the milk cows has pipes hooked up to the anaerobic digester. This manure, with the help of gravity and pumps, is funneled underground and into the digester every hour.
After the digester has captured and converted the gas to power, the cow manure and organic feedstock is far less smelly but is still nutrient rich. The liquid byproduct of digestion is piped underground to the blue slurry storage tanks. The Barstow's will fertilize their 400 acres of farmland with this fertilizer.
Vanguard Renewables has contracted with recycling company Casella Organics, Inc. to supply organic feedstock to the farm and RCM for the digester design. Manufacturing byproducts from companies become recycled feedstocks for the digester. Real Farm Power meets both Cabot's key retailers and state government goals for organic diversion from landfills. The management of the nutrients on the farm meets or exceeds the standards set by the NRCS (Natural Resources Conservation Service) of the United States Department of Agriculture.
Organic feedstocks arrive at the farm in liquid form and are piped from the delivery tanker to the underground storage tanks. The tank's heat is maintained by the hot water from the digester, keeping it a closed loop system. Every hour, the feedstock is added into the digester and mixed with the manure.
Barstow's Longview Farm receives organic material from 15 different food companies including their cooperative Agri-Mark, Inc., as well as Cains Foods, Inc., and HP Hood. They also receive food that would otherwise go to landfill from local food retailer Geissler's Supermarket.
Watch this great video produced by our friends at the New England Dairy Promotion Board.
The generator produces 285 kilowatts of electricity per hour at its highest level. This anaerobic digester produces 21,000 MWh per year. This is enough energy to power the equivalent of more than 250 homes. So the annual electricity needs of 250 homes is met thanks to 250 milking cows. But the actual use of the electricity from the digester is, first to provide the farm the electricity it needs and, second, to provide THE ELECTRICITY NEEDED TO CHURN CABOT BUTTER. This is arranged through a net metering agreement. The renewable energy credits (RECs) are not owned by Cabot Creamery; they are sold to benefit Vanguard Renewables, whose majority owner is Barstow's Longview Farm.
An onsite transformer allows the local electric company to access the electricity.
The engine produces 1 million BTUs of heat per hour. Water, pushed through to cool the engine, exits the engine at 200F and is channeled through a heat recovery unit along with the engine exhaust. A portion of the hot water is used to maintain the constant 100F inside the digester, contributing to the closed loop of the process.
Hot water is produced from this process and used to heat the farm house, and the milking parlor. Because there is so much recovered heat, the Barstow's are working on expanding the use of this heat in other homes in the neighborhood. Using the hot water to run an air conditioning unit in the barn is another long-term project for the farm!
In addition to generating usable biogas, fertilizer, and electricity, Barstow's anaerobic digester also: