Today MIT unveiled a long-awaited report on natural gas, which considers how much there is, how it can reduce carbon dioxide emissions, and what environmental and technical problems need to be solved with further R&D. The findings aren’t surprising. If carbon dioxide emissions are taxed or capped, it concludes, utilities will find natural gas far more attractive than coal, which emits roughly twice as much carbon dioxide.

That’s a big “if.” Climate and energy legislation is bogged down in the Senate, and the prospect of it passing with strong limits on carbon dioxide look dim. Without a price on carbon, utilities could keep doing what they’re doing now–burning coal while natural gas plants sit idle. As the study notes, on average natural gas plants are producing electricity at only 41 percent of capacity, while they were designed to run at 85 percent capacity. Given a choice, utilities burn coal, since it’s cheaper.

If there were a cap on emissions, those idle gas plants could be a boon, allowing a quick drop in emissions as utilities cutback on coal–without the need to build new plants. According to the study, requiring utilities to favor natural gas plants over coal plants could cut carbon dioxide emissions by 22 percent in Texas, and over 10 percent nationwide, without significant capital investment.