More and more colleges are grappling with issues on budgeting for climate neutrality. Around 40 percent of colleges' greenhouse-gas emissions come from purchased electricity. Through the American College and University Presidents Climate Commitment, which originated in 2007, hundreds of colleges have vowed to buy energy from green sources. In striving for climate neutrality, most administrators and observers acknowledge that renewable-energy credits, or REC's, a per-megawatt premium on energy that comes from renewable and carbon-neutral sources like solar, wind, and biomass, and offsets--projects that balance greenhouse-gas emissions in one place by lowering them someplace else--will play some part in getting to zero emissions. But many colleges have been wary of programs that involve shelling out money for REC's and offsets to atone for carbon emissions. Some argue that those methods allow colleges to buy their way to climate neutrality without addressing the gradually rising energy consumption on their campuses. REC's in particular have come under increasing scrutiny. One of the biggest problems with REC's is that when institutions buy green power through the credits, they don't know whether those REC's support renewable-energy projects that would have happened anyway. According to Anthony D. Cortese, president of Second Nature, a prominent sustainability organization, REC's and offsets will be an important part of climate-neutrality plans in the future. However, colleges should first concentrate on setting up sustainability programs and reducing energy use.