August 7th, 2009 · No Comments

By Shermakaye Bass
Green Right Now

Okay, here’s the poop on cow power: Dairy farmers from Wisconsin to Vermont are learning that they – and their bovine partners – can produce more than milk and manure. By converting the methane from cow patties into electricity, rural farms can provide their community with power – and in the process, eliminate the odors associated with dairy farming.

“The neighbors like it,” quips Steve Costello of the Central Vermont Public Service (CVPS)’s Cow Power program, which supplies 4,000 customers with the help of  6,000 cows. “You can have a barbecue on the Fourth of July without worrying the dairy farm next door is going spread some manure and wipe everyone out!”

Much more than that, of course, are the ecological benefits of using cow power:

• It’s a renewable energy source, not a dirty or fossil-fuel fed one (half of the energy used in the U.S. comes from coal).

• It reduces methane emissions, which are more potent greenhouse gas than CO2, trapping more heat in the atmosphere pound per pound.

• The final, solid product – after a process that includes a “digester” which breaks down the chemicals and bacteria, while the methane is trapped to generate electricity – can be used for bedding that is similar to straw, which typically has to be trucked in. (Once soiled, the bedding can be recycled yet again – returned to the digester and covnerted to topsoil or sold as fertilizer.

• Farmers use the slurry product that comes out the other end of the process, so to speak, to fertilize their fields, but with much less danger of spreading bacteria and toxins into the soil when they spread their manure.

• The digester itself kills most of the pathogens found in maure, includin E coli.

• Bonus fact: One cow can keep two 100-watt lightbulbs lit 24 hours a day, presumably in perpetuity.

“You’re taking a huge amount of waste out of the stream, if you will,” says Costello, explaining that CVPS started Cow Power in 2005 and is one of four such programs in Vermont.

“Nationally, cow power may not work so well – you’re talking about cows, so it’s typically got to be in rural areas – but it replaces dirty energy when it can. And a lot of our farms are using the heat left over from the generator to heat water for cleaning – supplanting either propane or number two, heating oil. That’s thousands of gallons that they’re not burning.”

Cows: An electric idea

Costello is an enthusiastic promoter of cow poo as energy, but out in Waterloo, Wisconsin, Crave Brothers Farms is helping their cattle reach their ultimate potential: To make dairy products, while converting their poop into energy for their home and cheese factory, as well as hundreds of Wisconsin homes. (Crave cows produce 650 KW per hour, which can power 550 households).

Mark Crave, who has come in from his 1,800-acre spread to talk on the phone, says the idea isn’t a new one to the family, which produces Farmstead Classics brand cheeses. He and his three brothers own and run the farm, along with their combined 12 offspring, and some of their offspring. He says there are a number of reasons why the family has jumped on the poop train, not the least of which is that, once through the digesters and generators and presses, their cow manure has almost totally eliminated the need to buy commercial fertilizers. The Craves like that, financially and ecologically.

The brothers started their poop power program about three years ago, although elder brother Charles Crave had been contemplating it since he founded the farm/cheese factory in 1981.

“It’s something that’s always been on our radar. We grew up on a dairy farm about 60 miles from here. My dad loved farming and he loved innovating. He oftentimes, when we were growing up,  would take us to farming trade shows and on field trips. And in the car on the way home , he’d say, ‘Boy, wasn’t that something?’ Or ‘What if we tried this?’ … Having four of us around, we were constantly kicking that ball aorund, if you will: How to change things, how to improve things. … Charles was always interested in (cow power), but until recently, there weren’t that many options. The only system that was in place was  farmer-engineered, as I like to call it. Built by the operators.

“The system we have is actually owned by Clear Horizons – an offshoot of a large electricity contractor in Milwaukee,” Crave says. “They’re looking at green energy as a growth industry. … But our motivation for doing it was that it allows us to better manage the nutrients in our soil. It changes how those nutrients escape into the system, so we can actually apply them to our fields. … It hasn’t saved us any money – yet. The initial capital outlay is more than $1 million. But we expect to (recoup) in about ten years.” (Note: The Craves send their energy to a power utility and then buy it back to power their farm.)

In addition to having 1,100 cows and 900 head of young stock – with a total of 950 milking cows – the Crave family grow corn, soybeans and alfalfa. (They also make an allegedly killer cheddar). And when it comes to fertilizing their crops, they, like all farmers, have limits on the amount of phosphorus (which fertilizer contains) that can be put into the soil.

“Most of the phosphorus (translation: fertilizer) that’s in manure is in the solid portion of the manure,” Crave says, explaining why dairy farmers spread their cows’ poo over their fields (thus the potential July Fourth stink-out), to create a better yield.  ”Our cow manure,  as it goes into the system, is 12 percent solid. Once it goes through this digestion process – which takes anywhere from three to four weeks’ retention time in the digester – it changes byproducts like nitrogen from an organic to a mineral state, and that makes it (nitrogen) less volatile. So that means It’s more stable in the soil, so it doesn’t leach out with rain.

“But by doing this, we’re also able to better manage the nutrients in our soils,” Crave adds. “The number one limit for applying manure to our cropland is phosphorus. Historically, before we had the digester, when we would go apply manure to the soil, when we reached our limit, we’d have to test it. … Now, we can apply manure as fertilizer at whatever rate that crop will use, and we can meet our fertilizer needs without having to to buy commercial fertilizer. It (the whole process) allows us to separate our manure into different components, where we can use it.” And literally recycle it!

Here’s essentially how it works: The cow’s manure is routed to anaerobic “digester”, which is kept around 100 degrees Fahrenheit for 20-30 days. Bacteria break down the waste, producing, among other things, methane gas, which builds up pressure in the digester. Next, the biogas is delivered through a pipe into a modified natural gas engine, which in turn fuels the engine, making it spin the generator, creating electricity.

In addition, as Mark Crave explains it, “when the manure comes out of the digester we put it into a screw press and separate out about half of the solids. What we do with those solids is multiple-use: Number one, those solids (which, pressed, become thin, fibrous organic compound – voila cow “straw”) go back into the barn and are put into the stalls.  It’s a very inert product that has very little odor, it’s very much like green sawdust and in fact probably has less of a small than even sawdust. It’s a fluffy, very loose laying product, and the cows just love to lay in it.”

What remains after that bedding is used, is again recycled using the digester, and can be sold as potting soil.

“It’s basically a closed loop system,” says Crave.

Who knew poop had so many positive qualities?

(Photo credits: Blue Spruce Farm — Steve Dvorak, left, and Melissa Dvorak, right, talk with Eral Audte and David Dunn at Blue Spruce Farm while the separator behind them takes solids out of the liquid manure after it is digested, so the liquid can be used as fertilizer and the solids used as animal bedding; Earl Audet, left, co-owner of Blue Spruce farm, and David Dunn, program Manager for CVPS Cow Power^TM, examine dry solids left over from the digestion process.)

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