Proponents of natural gas tout new shale deposits, such as Pennsylvania’s Marcellus, as a way to reduce carbon emissions while the world eases itself off fossil fuels, and moves toward alternatives such as wind and solar. Natural gas power plants emit less CO2 than coal, which still dominates electricity generation worldwide. In the U.S., low natural gas prices have allowed natural gas to catch up with coal-fired electricity. But this “bridge fuel” scenario is controversial.
Some say the world is warming too quickly to even consider the concept legitimate. Still others say the process of extracting natural gas at the wellhead emits enough methane, a greenhouse causing gas, to negate any benefits of lower carbon dioxide emissions at power plants.
Climatic Change, a peer-reviewed scientific journal, has just published online a report that has something to make both sides happy and sad. Written by Michael Levi, “Climate consequences of natural gas as a bridge fuel,” is one of the only reports to look at the issue from a vantage point of global emissions reduction goals. The bottom line, says Levi, is that any potential “natural gas bridge” would be useless because it would be so short. He does say, however, that natural gas can play a role in easing nations off of coal.
“Collectively, these results suggest that it may be useful to think of a natural gas bridge as a potential hedging tool against the possibility that it will be more difficult to move away from coal than policymakers desire or can achieve, rather than merely (or primarily) as a way to achieve particular desired temperature outcomes.”
Natural gas opponents will cheer these results. But they won’t be too happy about Levi’s conclusions about natural gas emissions at the wellhead. Levi says when lowering emissions to halt climate change, the methane that leaks from natural gas wells is not enough to offset the benefits of lower CO2 emissions at the power plant.
“Moreover, in most cases where stabilization is near 550 ppm CO2, even high rates of methane leakage do not fundamentally alter the conclusion that replacing coal with gas can substantially lower peak temperatures relative to what they would be if a transition away from coal were instead delayed. In particular, if so-called “tipping points” can be triggered by exceeding particular temperature thresholds, methane leakage in the context of bridge fuel scenarios will have at most a very small impact on the odds that those thresholds will be crossed. This is true even if steps to reduce methane leakage can yield benefits exceeding costs.”