Here are six key arguments about gas, starting with the case for the fuel:

1. Gas is killing coal

When burned cleanly, gas releases about half as much carbon as coal. Gas has been on a coal-killing advance across the U.S. power market for the last decade.

2. Gas helps bring down emissions

Cleaner electricity generation means the U.S. economy can still grow and produce lower emissions. Greenhouse gas emissions have been on a flat-to-downward trend for the past decade.

3. Gas will be affordable long-term

Thanks to fracking, which releases fossil fuels from hitherto impermeable shale rock, American gas is so abundant that producers can’t find enough domestic demand and are rushing to export. That means local prices are cheap and look like they’ll stay that way.

And here’s the case against gas:

1. Gas means carbon is unavoidable

While carbon dioxide emitted from gas-fired power is lower than coal (see above), locking in gas as a fuel means those emissions won’t go to zero any time in the foreseeable future. Indeed, as the U.S. becomes increasingly addicted to gas, emissions from the fuel are rising in absolute terms, overtaking coal.

2. Gas is being wasted

Excess gas from oil wells is burned off in flaring, releasing carbon dioxide. The amount of gas being wasted has surged in the U.S. due to the fracking boom, as pipeline capacity can’t keep pace.

3. Gas leaks

Another problem is gas leaking from pipelines and processing plants into the atmosphere. Methane is 84 times more efficient at trapping heat than carbon dioxide over a 20-year period. It’s the “Achilles heel” of the gas industry, according to Susan Dio, chairman of BP Plc’s U.S. division. There’s been a substantial rise in global methane levels over the past 10 years, according to the National Oceanic and Atmospheric Administration. A Cornell University study published in August traced the extra emissions to fracking in North America.