Environmental groups in Minnesota are considering their nest steps on the heels of a regulatory decision they say weakens the state's landmark carbon-free electricity law. Late last week, the Public Utilities Commission clarified which technologies should be in the mix, as energy providers try to meet the requirement of 100 percent carbon-free electricity by 2040. The commission opened the door to allowing biomass - namely the burning of wood - and trash incineration to count as clean sources. Barbara Freese is with the Minnesota Center for Environmental Advocacy. She says it's troubling the commission didn't rule these options out. But utilities like Minnesota Power prioritizes biomass as a form of renewable energy, with supporters arguing it's better to burn wood scraps from the logging industry than let it decompose. They say that creates other carbon dioxide issues, and the a cabon-neutral approack helps carry out the mission of the law. The commission decided more analysis is needed to get a clearer picture of the eligibility of these sources.