A majority of the methane digesters in the U.S. are on dairy farms, and more operations could benefit from them, depending on the future of climate change legislation and other factors, according to the U.S . Department of Agriculture.

A recent USDA Economic research brief on the biodigesters, which collect and burn methane to generate electricity, shows that a 1,000-head dairy farm in Wisconsin would generate an average of $56,300 in electricity, compared to $77,500 (based on what consumers pay for electricity in those states). Farms that size in Wisconsin pay an average of $125,700 a year in electricity, natural gas and propane, while those costs in California are much lower -- $53,600 – because of lower heating expenses throughout the year.

California doesn’t allow anyone to sell excess electricity back to the utilities, unlike Wisconsin, giving Wisconsin dairies more incentive to build the systems, according to the USDA researchers.

The systems, however, carry an initial price of $336,000-652,000 and up to $28,000 in annual maintenance costs. Operations with more livestock will see a higher net value per head, according to the study.

Supply won’t meet demand, either, with fluctuating methane production and need for more power at certain times of the day.

The big unknown is the future of climate change legislation and adoption of a carbon offset market, which would allow farmers to be compensated for capturing and using methane.

The research brief is part of the ERS’ “Climate Change Policy and the Adoption of Methane Digesters on Livestock Operations."

According to the Environmental Protection Agency, as of October, of the 157 methane digesters in the U.S., 126 are on dairies and 24 on hog operations.