One of my roles at the Energy Center of Wisconsin is to identify and quantify biobased renewable resource opportunities. For the past several years, I've analyzed and written about one of Wisconsin's most exciting and promising energy resources, manure. Strangely enough, there are energy opportunities for Wisconsin that begin with animal waste.
In the years since I began analyzing bioenergy feasibility, Wisconsin has jumped to the forefront of implementing animal waste-to-energy systems. What's intriguing about these systems is that they turn our state's existing waste into high-value products. We don't have to ship in any new raw materials when we have it right here.
Yes, animal manure is something we have a lot of here in Wisconsin. As "America's Dairyland," we're home to 1.25 million natural energy sources at work every day in our rural communities—dairy cows. The bioenergy systems that process cow manure (as well as other organic matter) are called anaerobic digesters, and they are one of the technological advances that is making it possible for large numbers of cows to coexist with people in our state.
While writing the Wisconsin Agricultural Biogas Casebook in 2009, I talked with nearly all of Wisconsin's 22 dairy farmers using a total of 31 digesters on their farms. Now in 2011, we have 26 farms with 33 digesters in operation, more than any other state. But it's for different reasons than you might think. The reason we lead the nation in this technology has as much to do with our people and our cooperative spirit as it does with our cows.
Economics of digesters
Installing an anaerobic digester and all the related equipment is expensive, and the cost per cow is higher for smaller farms. AgSTAR, the federal program that encourages methane recovery, estimates costs ranging from $780 per cow for the largest dairies, up to $1,600 per cow for farms with 650 cows (Source: United State Environmental Protection Agency). For this reason, current common digester designs are not considered workable on smaller farms. Research is underway right now to bring cost-effective digesters to farms with, say, 200 cows.
When I asked farmers why they invested in digester technology, it was almost never to make money. What I found is that Wisconsin farmers have a strong environmental ethic. They see other benefits from the digestion process that do not necessarily show up on a balance sheet, like reducing odor and having as small a carbon footprint as possible.
Take the Crave Brothers Farm in Waterloo, Wis., for example. More than 1,000 milking cows and young stock produce 50,000 gallons of manure each day. In 2007, the Craves contracted with Clear Horizons LLC to build the first of their two digesters to help them deal with all that manure.
Charles Crave, who oversees the farm's financial matters, estimates an eight- to ten-year payback on the digester equipment investment. But the Craves have their eye on the big "green" picture. "The digesters are a perfect opportunity for us to be good to our soil, our cows and our neighbors," Charles says.
"The digesters are a perfect opportunity for us to be good to our soil, our cows and our neighbors."
~ Charles Crave
Wisconsin utilities deserve some of the credit for their role in encouraging digester innovation. Because these systems typically produce more energy than the farms use, most farms sell their electricity onto the grid, which involves working with a willing utility. Wisconsin utility companies have played an important role in helping farmers make the necessary equipment connections and offering higher prices than the utilities are obligated to pay for the electricity.
In addition, USDA and the Wisconsin Focus on Energy program have made grants available to help lower the upfront costs to get these systems built and hooked up to the grid.
Our bioenergy future
How much can manure factor into Wisconsin's green energy goals? While we're at the forefront, we do have much more potential to make digesters a significant contributor to our renewable energy production. By contrast, Germany has thousands of digesters in operation, processing everything from manure to corn silage to food scraps and restaurant grease.
Can Wisconsin rise to this challenge? We certainly have the cows to do it. Wisconsin Focus on Energy estimates that five cows can provide renewable power for one average home, 24 hours a day, seven days a week. Unlike wind or solar power, manure is a pretty consistent resource here. There are days the wind doesn't blow, but there is never a day that a cow isn't making manure.
Of course, not all of our cows are on dairies large enough to own a digester. AgSTAR estimates about 13 percent of the cows in Wisconsin are on farms of at least 500 head–the minimum size to have a workable digester (Source: Environmental Protection Agency). Smaller-scale technology could reduce that herd size minimum in the future.
In the meantime, some farmers and communities are considering the benefits of sharing digester systems. Clear Horizons, the firm that built Crave Brothers' digester, recently completed the state's first cooperative community manure digester in Dane County, which came on line in December 2010.
Indeed, America's Dairyland is doing more than producing milk. We have more licensed dairy herds here than in any other state. That means we have energy potential that does not need to be imported, as long as those cows keep doing their thing. Charles Crave put it this way: "We have the farms, we have the universities, and we have the infrastructure here. Is anyone surprised that we can lead the nation?"