Methane Digesters are Reducing Cows’ Carbon Hoofprints



digester2_editHow much would you pay to convert manure to electricity? What if you could power your home and workplace, make fertilizer, keep organic waste out of the landfill, reduce greenhouse gas emissions, and sell excess energy to the local grid?

To transform guilt into virtue, is $3.1 million too much?

Today’s ranchers and farmers stand accused: The placid cow leaves an enormous carbon hoofprint. Its manure releases methane, a greenhouse gas so potent it makes carbon dioxide seem like a breath of fresh air. But the good news is methane is also a combustible fuel and the anaerobic digester is helping farmers convert this dangerous gas into a power source.

Initially developed in Europe, this ingenious conversion method is being employed by a number of American farmers with financial backing from environmental entrepreneurs who underwrite the hefty price tag. In Massachusetts, Boston-based investor Bill Jorgenson has financed anaerobic digesters for two mid-state dairy farms, Jordan and Barstow’s. “The digesters are a win-win,” Jorgenson says, “They turn a problem into a solution.”

Here’s how the alchemy works: The cows drop their manure onto the barn floor where it falls through open slots into an underground vat. From there it’s pumped into the digester, a 35-foot high, 600,000 gallon tank. Warmed and churned, the brew breeds bacteria and microbes that feed on the biomass with enormous appetite. Within a few hours, methane rises from the decomposing waste to fill the tank’s top hat, a pliable rubber dome. Hoses then siphon off the gas to an engine where it burns, generating electricity.

digester1Opened in 2011 with a ribbon-cutting ceremony officiated by Governor Deval Patrick, the first anaerobic digester in Massachusetts is run by Randy and Brian Jordan, fifth-generation farmers with a 700-head dairy farm.

Randy takes me on a start-to-finish tour from the barn to the generator, clearly proud of the impressive array of pipes, funnels, tubes, and wiring that connect the various components like some giant Rube Goldberg contraption.

Randy looks forward to the day his farm can also capture heat (from the water that cools the generator engine) and use it to warm greenhouses. His stolid face takes on a calculating look. “There’s no telling what we’ll cultivate in the future, once we have a steady heat supply,” he says. “Tomatoes? … Marijuana?”

Recent legislation in Massachusetts makes it fertile ground for digesters. As of October 2014, the commercial food industry is prohibited from sending organic waste material to landfills. Dairy companies like Hood and Cabot have already struck a symbiotic deal with the Jordan and Barstow’s farms, delivering them food waste to combine with manure. When the Hood ice cream machine switches flavors from chocolate to strawberry, for instance, the flushed dregs end up in the digester.

These organic additions change how the biomass decomposes. Varied compositions of sugars and proteins affect the volume and makeup of gaseous output (as many who eat beans and asparagus can attest).

Down the road apiece lies the second digester in Bill Jorgenson’s domain, at the Longview Farm. This system has the added attraction of storing delivered food wastes in three separate tanks. Farmer David Barstow experiments with adding the different kinds of waste one at a time, carefully monitoring and measuring the methane output for optimum production: More methane creates more electricity. Jorgenson says they are now selling 80 percent of the generated power back to Western Massachusetts Electric. He expects to make his investment back in four more years.values-in-action-methane-digester-pond__large

Anaerobic digestion provides the missing link in a sustainable farm system. Once begun, several renewable loops continue to feed one another. The farm grows crops, which are fed to the cows, which produce manure, which releases methane, which creates electricity, which powers the farm, which grows the crops. In another loop, the decomposed manure, cleaned of toxic chemicals, morphs into fertilizer that nourishes the crops that are fed back to the same cows.

In the dairy farm capital of Wisconsin, anaerobic digesters are being adapted for smaller scale operations with a more affordable price tag. On the Peters Family Farm, a 200-cow operation near Chaseburg, a digester using a less expensive steel tank has been developed for just over a million dollars. Bolstered by the nearby Organic Valley plant’s supply of food waste–high in butterfat–this system captures heated water to use for sanitizing and warmth in the milking parlor.

The digester powers the farm with renewable energy, improves odors, and reduces the fly population. But Wayne Peters’ pet benefit is the resulting fertilizer, which he says is easier for plants to absorb. “The most valuable byproduct is the enhanced fertilizer… we use to grow hay, corn and small grains to feed our cattle.”

On California’s coast north of San Francisco, the Straus Family Creamery uses a basic anaerobic digester that cost a mere $334,000. This organic farm in Marin County doesn’t use a tank at all, but holds the manure in a tarp-covered pond. From there, the rising methane is pumped into an engine and burned. The Straus family reaps the same benefits as other digester-powered farms, while charging founder Albert Straus’ electric car.Jordan cow

Beyond immediate benefits to the farms themselves, anaerobic digesters harness gasses that would otherwise pollute the atmosphere and burn them instead of fossil fuels to create energy.

Consumers of beef and diary can feel good about livestock products coming from farms that employ anaerobic digesters. While their initial start-up costs may be high, a digester’s price doesn’t come anywhere near the estimated price of runaway climate change. This fact alone makes them a worthwhile investment.

 

 

 

 

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  1. Jim Goodman
    Thursday, August 28th, 2014
    One needs to remember that if you like the idea of manure digesters you must also like the idea of lots of animals confined in a small area. Digesters were designed for use on CAFO's. While some designs are being tried on smaller scale farms, (100's of animals as opposed to 1,000's), the rule of thumb is that you need at least 1,000 cows to make a digester potentially feasible. Even with enough cows, financial subsidies are needed and constant addition of substrate (food waste, slaughterhouse waste etc.) Then there is still the lingering problem that most of the time they do not work properly and are a maintenance nightmare. Energy output seldom comes anywhere near original estimates, they merely green-wash unsustainable farming practices.
  2. Rob Barreca
    Tuesday, September 2nd, 2014
    I'm with Jim on this one. The digester is just a bandaid on the problem.

    When cows are rotated through pasture rather than confined, manure becomes an ASSet for improving a pasture's health.