"Citing excessive costs and an untested infrastructure to procure organic material such as waste from farm fields, Walker killed a $250 million project at UW-Madison in 2011 that would have burned biomass to generate electricity. "In another case, a Dane County biodigester that received a $3.3 million state water quality grant to process manure from three farms near Waunakee suffered an array of operational problems, including manure spills and a methane gas explosion in 2014 before the business was taken over by new owners. "Wisconsin leads the country in the number of farm-based facilities, with 35 in operation today, according to the State Energy Office."The office has estimated that seven other sites have shut down, or are no longer operating at full capacity, as biodigesters struggle with lower electricity prices. "The systems became attractive after the Legislature in 2006 passed a bill directing utilities to supply 10% of their electricity from renewable sources by 2015. That goal has been met and utilities have won permission from the state Public Service Commission to buy back power at lower, wholesale rates."Alliant Energy is currently paying an average of 9 cents per kilowatt-hour, the utility said. But for digesters whose contracts expire, generally after 10 years, the going average rate is about 3 cents per kilowatt-hour. "Other factors that made biodigesters less attractive: a drop in natural gas prices and more natural gas and wind power."