Patrons of Madison’s Brasserie V and Sauk City’s Windmill Pizzeria soon will have a unique story to go along with the spinach, Swiss chard, kale, butterhead lettuce or brussel sprouts on their plate.
On a weekly basis, possibly as early as mid-May, a delivery of these leafy-green veggies will arrive from a greenhouse powered by the hot-water waste produced by the Clear Horizons manure digester near Waunakee.
Lately, the digester has gotten a bad reputation around Madison for spilling 435,000 gallons of liquid manure since November.
Watershed experts, however, still view it as a key part of Madison’s solution to cleaning up the lakes. And there are experiments afoot to make it even more worthwhile — by squeezing some profit out of the project.
“What’s happening at the digester is a win-win,” said Brian Zimmerman, who, along with Madison resident, Taylor Jacque, is growing the veggies. “Phosphorus is being removed from the manure and staying out of the watershed, and we are getting free energy.”
The greenhouse and its veggies are one example of a new cottage industry popping up across the country to capitalize on the waste energy, methane gas and the nutrient-rich solids that are emitted from a digester.
The digester processes 100,000 gallons of manure daily from the 2,400 cows that live on three farms just shy of a half mile from the digester. It is one of four digesters in Dane County and 34 in the state. A fifth, a community digester located outside Middleton in Springfield, is scheduled to begin processing manure in June.
Without them, the manure would be stored in manure lagoons for future spreading on fields, making it easier for the phosphorus-rich byproduct of farming to run into local watersheds.
“Maybe they had those spills,” said Zimmerman, a 26-year-old University of Wisconsin-Madison graduate student and former Brasserie V employee. “But before the digester was out here, the manure was spilling everywhere.”
The Clean Lakes Alliance’s goal to reduce phosphorus levels in Madison’s lakes in half by 2025 is estimated to cost $128.1 million — and $49.5 million of that is for five new manure digesters.
“It’s time for people to connect those dots,” Zimmerman said. “The algae blooms in the Madison lakes are a result of our want of cheaper milk and meat. Farmers are simply responding to a market demand caused by all of us, including me.”
But the digesters have to pencil out. And that’s why all sorts of experiments are abloom.
“For the digesters in Waunakee or Middleton to be profitable, they need a ‘bolt-on’ purpose,” said Monte Lamer, the plant manager for Clear Horizons’ Waunakee community digester. “They can’t just rely on renewable energy. They need a second purpose.”
Companies like Massachusetts-based Dairyvative Technology produce condensed milk a seventh of its original volume, allowing it to be affordably shipped long distances without requiring refrigeration. The owners are interested in running the plant using the waste energy from a biodigester.
California-based Mango Materials is using a digester’s waste biogas to produce a biodegradable plastic. Poker chips are one product in the development phase.
“I see great potential for digesters,” said Anne Schauer-Gimenez, Mango Materials’ director of biological research, who earned her doctoral degree from Marquette University and her undergraduate degree from UW-Green Bay. “Our team has done some calculations that show making biodegradable plastics is up to six times more economical than using the waste biogas for other uses, including electricity.”
Schauer-Gimenez spoke at an environmental engineering seminar at Marquette University April 28 to share her experience with digesters and biogas products.
In addition to talking with researchers like Schauer-Gimenez, Lamer is recruiting companies and UW-Madison talent to work with Clear Horizons to create new digester products.
The nature of trying to capitalize on new technology is trial and error.
Lamer first met Tony Hartmann, the chief executive officer of Great Lakes Ag Energy, the company that built and owns the greenhouse, shortly before the digester opened in 2011.
Hartmann originally built the greenhouse to see if it could grow algae and duckweed fast enough to reduce the amount of phosphorus in the liquid byproduct produced by the digester. The phosphorus-depleted liquid is returned to farmers to spread on their fields as fertilizer.
The project did not pan out.
“We didn’t have the optimal algae mix and we learned our greenhouse was too hot in the summer,” Hartmann said. “We were actually getting a lot of blue-green algae, which is one of the nastier things found in the lakes that causes the beaches to close, instead of the kind that soaks up phosphorus.”
The greenhouse is now being used by Zimmerman and Jacque, 25, as well as Blackhawk Church of Middleton, and an independent grower.
Heat is still an issue. It is too hot to continue growing in the greenhouse through the summer.
Zimmerman, Monte and Hartmann are looking for other university students to experiment with the greenhouse’s potential.
“We have a huge source of hot water just sitting here,” Zimmerman said. “We could possibly put the pipes underground or find other ways to have a higher level of control over the greenhouse’s environment. It needs to be redesigned for more efficient vegetable production.”
You must be logged in to post a comment.