The manure digester in the Town of Springfield could eventually eliminate more than 90 percent of algae-causing phosphorus from the manure it processes with new technology now under development.
Dane County plans to put $1.3 million toward equipment to render manure into clear liquid, clean enough to discharge.
County officials are now evaluating four bids for a Nutrient Concentration System to install in 2015.
Currently, the digester, owned by Gundersen Health System and operated by US Biogas LLC, processes manure from Blue Star Dairy Farms, Hensen Brothers Dairy and Ziegler Dairy Farms in three digester tanks. It also processes food waste.
The tanks are heated, allowing bacteria to consume solids in the manure and release methane gas. The gas is captured and burned in a generator to create electricity.
But new technology would separate fibrous solids from the manure, allowing it to be treated by reverse osmosis, the process used in municipal wastewater plants, according to Duane Toenges, US Biogas CEO.
“Reverse osmosis… is nothing new. It’s very proven technology that’s been used in water treatment plants for years and years,” Toenges said. “The problem why it hasn’t worked in agriculture is because of all the suspended solids. It’s made the cost very high.”
US Biogas is installing a similar system to be used for swine manure in Illinois, Toenges said.
The Springfield digester, similar to the one in the Town of Vienna operated by Clear Horizons, was built with the intention of removing phosphorus from manure, preventing the algae-causing substance from entering waterways and lakes. The digesters also help dairy farmers manage manure.
If the Nutrient Concentration System processed manure to water, farmers could spread less, saving on hauling and on storage, Toenges said.
Toenges said the Springfield digester processes between 65,000 to 70,000 gallons of manure per day and 35,000 gallons of food waste.
Dane County is investing $1.3 million to prove the process is economically viable, Toenges said.
While similar systems have been used on dairies, Toenges said this would be the first to allow a discharge of water.
“This new technology that will get us to 100 percent phosphorus removal is a game-changer in our efforts,” County Executive Executive Joe Parisi said.
Parisi noted that the system would not only help achieve the county’s efforts to keep the chain of lakes algae- free but also benefit the local agricultural economy.
“At the end of the process, [farmers] will have much less of a waste product to deal with,” Parisi said.
The new technology would have great benefits for farmers, according to Kevin Connors, Dane County land conservation director.
“You can apply smaller volumes to growing crops,” Connors said. “As a result of doing so, the hope is that you can apply it not when you have to empty a storage structure but at times when crops could use it.”
The separator might also be able to produce fertilizers with different waste strains, such as potash for alfalfa crops and nitrogen for corn, Connors said.
Parisi noted that the biodigester could create a product to be sold.
“It’s very exciting technology,” Parisi said. “If we’re able to demonstrate it works successfully, it could be feasible for a lot of other operation.”
Dubbed “cow power” projects, the biodigesters also reduce CO2 emissions and generate electricity.
The Springfield digester generates approximately 16 million kilowatt hours of electricity annually that is added to the local grid through Madison Gas and Electricity – enough to power approximately 2,500 homes.
According to the county executive’s office, funding for the Nutrient Concentration System is coming from three different year’s budgets.