Joseph Gallo’s Cottonwood Farm near Merced, in California’s central valley, is home to 5000 milk cows, and processes 900,000 pounds (408,000 kg) of cheese each day. But the most impressive thing about Cottonwood is that each year, it generates 2.5 million kilowatt/hours of electricity and enough heat to save 149,000 gallons (564,000 litres) of propane, for total energy cost savings of about a thousand dollars per day.
The energy source for all of this is methane — from cow manure.
Manure is flushed from the dairy with water from wells, and pumped to a 7-acre (2.8 hectare) lagoon, sealed with a thick plastic cover, where natural microbial action converts the nutrients in the manure to methane gas. The gas is captured and piped to the cheese plant, where it fuels a 300-kw generator operating around the clock. The electricity provides a substantial portion of the cheese factory’s power. The heat from the generator is captured and used to produce steam for the cheese plant as well.
As a result, since methane is a greenhouse gas, and less propane is being burned, air quality is improved, as well as ground water contamination. The amazing part is that this dairy doesn’t smell like a dairy at all.
In this picture you’ll see the first step of the process, where a separator tower is used to sort the solid waste out of the flush water from the dairy. Solid manure is dried and composted and used as fertilizer for feed crops in the company’s fields, and the liquid is piped to the digester. Be sure to click the hotspot on the sign “TO DIGESTER”
, which will take you to a panorama of the covered digester lagoon itself — surely the world’s most spectacular air mattress.
is the largest dairy operation in the USA, with over 34,000 head of livestock, five dairies and the cheese factory, and farming operations that include 15,000 acres (6,000 hectares) of combined corn, grain, and irrigated pasture.