Abbie Fentress Swanson contributed this story for Good Food.
At Point Reyes Farmstead Cheese Company, Bob Giacomini, 77, and his daughters manage an 800-Holstein herd on a bucolic hilly farm abutting Tomales Bay. Soon after making their first wheel of tasty Point Reyes Original Blue cheese in 2000, the Giacominis installed an anaerobic digester on the farm. Anaerobic digesters are huge closed containers that create renewable energy from manure and other food waste products.
Here’s how the digester works: The dairy uses recycled water to wash cow manure from its barn floors into the digester. A manure separator removes the solids, which are destined to be compost, bedding and potting soil.
The liquid waste, or slurry, is then mixed with the whey waste from the creamery plant in an underground tank. This foaming mix, which surprisingly smells more like a pair of old sneakers or a musty attic than cow patties and raw sewage, next flows into a giant two-acre pond covered with a hard black plastic dome.
Under the dome, it takes microbes between 25 and 29 days to break down the waste. Methane released at the end of this process is captured and pushed by an electric blower through an underground pipe to a generator that’s run by a combustion engine. There, the biogas is converted into electricity and heat.
Each week, the Giacomini digester converts 17 yards of cow manure into 550,000 kilowatts of energy. This saves the farm about $1,000 a month on propane that’s used to power and heat the milk parlor and cheese plant. And it keeps the methane from the Holsteins and their manure from entering the atmosphere. “I’m doing my share by corralling the methane that we’ve got from letting it go out into the atmosphere,” said Giacomini. “And by doing that, it’s giving us an added benefit in making us environmentally friendly in the process of selling our dairy products.”
But digesters aren’t cheap. The Giacomini digester cost about $600,000 to install. Half of that was paid for with government grants, and there are future incentives on the horizon. This week, the state gave five California dairies $11.1 million to build digesters. Over the next ten years, the US Department of Agriculture wants to place 500 digesters on farms across the country.
Even companies with no connection to ag are buying into this technology. United Airlines recently announced it plans to fly planes this summer from LA to San Francisco with jet fuel made from farm waste and animal fats. Increasingly landfills and wastewater treatment plants are also using digesters to recycle their waste.
UC-Davis animal science professor Ermias Kebreab believes digesters can go a long way towards reducing the waste from dairy farms while providing electricity and heat for farmers at the same time. “In terms of environmental sustainability, I think anaerobic digesters have a huge, huge potential,” Ermias said. “It’s good for the farmers because they get energy out of it and it’s good for the environment because we are reducing the methane that would have gone into the atmosphere.” Agriculture is responsible for about 8 percent of greenhouse gas emissions in the US, Kebreab says, and most of that is from cattle ranches and dairy farms. Since California raises more dairy cattle than any other state, digesters could have an especially big impact here.