This week a New York Times op-ed rekindled a debate about whether switching from natural gas to coal actually reduces overall greenhouse gas emissions.
While the Obama administration has presented natural gas as a “bridge fuel,” a cleaner alternative to coal that can reduce emissions until we can switch to renewables, some researchers question whether natural gas provides any net benefit compared to coal. And they say that emphasizing natural gas only delays a move to renewable energy. In the op-ed, a Cornell professor argued that far from being a bridge fuel to a clean energy future, “it’s a gangplank to more warming.” At least one expert responded by labeling the professor and those who agree with him “worriers.” (You can find some reasoned responses here and here).
There’s no question that burning natural gas releases far less carbon dioxide than burning coal (see “King Natural Gas”). The differences arise when estimating the effect of natural gas leaks on climate. Natural gas includes methane, a potent greenhouse gas. In the process of producing and transporting it, some of it leaks into the atmosphere.
The first area for disagreement arises because comparing methane to carbon dioxide is difficult. Methane is a more powerful contributor to warming in the short term, but it doesn’t last nearly as long in the atmosphere. The question is whether you would you rather release methane as a result of natural gas production and boost warming for a few decades, or release carbon dioxide from coal plants and be stuck with the warming it causes for many hundreds of years?
The other question is how much methane actually leaks into the atmosphere. Some leaks are okay. Below a certain threshold, natural gas remains a clear winner over coal. The problem is we do not comprehensively measure leaks from natural gas wells or the massive infrastructure that delivers that natural gas. Doing so would be far too expensive, and impractical to boot, even though the sensing technology is improving (see “Measuring the Climate Impact of Natural Gas”). Studies have been done, but the question is how to extrapolate from these limited studies.
So there is plenty of uncertainty. But a decision needs to be made.
How? Part of the answer is to expand the debate to take into account some practical realities.
First, we have to consider that the power plants we build now will be around for decades. There’s already evidence that technological improvements are helping to reduce methane emissions (see “Three Technologies Could Solve the Methane Leak Issue”). If the trend continues, the case for natural gas will get better over time.
Coal is also generally dirtier than natural gas, when you look at pollutants like sulfates and mercury—another reason to prefer natural gas.
And the fact is, practically speaking, we are stuck with natural gas for some time. “The use of natural gas pervades our economy,” says Mark Brownstein associate vice president and chief counsel of the Environmental Defense Fund’s U.S. Climate and Energy Program. He notes, for example that two-thirds of natural gas produced goes to things other than electricity production (heating, cooking, industrial processes). Even if we switched to renewable resources for 100 percent of our electricity, we’d still use a lot of natural gas. “As long as natural gas is part of the economy, we should do everything we can to minimize the risks and the loss of that gas to avoid unnecessary global warming,” he says.
EDF, with the University of Texas, is currently conducting an ambitious study of methane emissions that will provide a much clearer picture of how much methane is leaking, and, critically, where it is leaking. This will inform regulations on natural gas production and distribution. And Brownstein says it could also help the natural gas industry. Right now, businesses don’t know how much gas they’re losing. Once they know, they might decide that it’s worth the investment to plug the leaks.