The fossil fuel drilling method known as hydraulic fracturing, or fracking, has caused a boom in the U.S. domestic natural gas supply. Natural gas is called a “bridge fuel” by proponents, meant to bridge the transition from a fossil fuel to renewable energy economy, since it emits less carbon dioxide than coal and oil—but is it really good for climate change?
Fracking has caused roughly a 45% increase in the U.S. natural gas supply; we get about 2/3 of our gas from fracking these days (and about half of our oil). Fracking has caused local environmental degradation, but in this article I’m concerned only with its capacity to decrease our greenhouse gas emissions. To compare the climate benefits of using natural gas, we should primarily compare its impact to coal, as power plants are generally powered by coal or natural gas—the U.S. currently consumes 33% of its electricity from coal and 33% from natural gas, and natural gas has been replacing coal in recent years. (Find a map of fracking in the 50 states here.)
When burned, natural gas emits about one-half the carbon dioxide of coal, and about 75% of the emissions of oil. However, the biggest problem is that wells that are fracked for natural gas have been shown to leak methane—the chemical form of natural gas before it’s burned—a potent greenhouse gas. If fracking causes leaks that are significant enough, the relative climate benefit of fracking for natural gas disappears.
A multitude of academic research in recent years has studied and proven the underestimation of methane leakage from fracked wells. U.S. methane emissions increased 30% from 2002–2014. One academic paper found that fracked wells release 30–50% more methane than conventional natural gas wells, and those wells allowed 3.6–7.9% of the gas to escape to the atmosphere. Another paper estimates around 5.4% escapes. Overall, the research literature (see here, here, and here) provides a bulk of evidence that shows the amount of methane previously thought to escape from fracked natural gas wells to be underestimated and substantial.
Furthermore, a couple researchers argue that when everything is tallied up—even though there’s still some uncertainty in how much methane is actually escaping from fracked wells—the benefits of substituting natural gas (much of which comes from fracking) for coal for electricity generation really only pays off close to 100 years in the future (here and here). (The EPA is just now in the process of putting together rules to regulate new natural gas wells to limit their methane release, in an effort to reduce U.S. methane emissions by 40–45% by 2025.)
So, while there is uncertainty in the climate impact of fracking for natural gas to substitute largely for coal, it does seem like the substitution wouldn’t result in much of a benefit, if wells are still allowing methane to escape.
This evidence presented above partially answers the question of whether natural gas can act as a “bridge fuel” in the transition to a renewable energy economy (yielding the answer “probably not”), but there’s also a second point to be made. To really transition to renewable energy (which only made up 10% of the U.S.’s 2015 total energy consumption and 13% of its electricity generation), we need to get to the “price parity” point, when renewable energy will be as cheap and then cheaper than energy from fossil fuels. Fracking increases the natural gas (and oil) supply, which lowers the price of consuming natural gas for electricity, which will actually further prolong the point when we reach price parity.
The price of electricity from wind and solar power has been dropping in the U.S., but the price of electricity from natural gas has also been significantly declining (and is far more prevalent around the country than wind and solar), as natural gas consumption has been increasing, largely displacing coal. All this while, renewables have seen only a modest increase. (See figures below.)
Overall, natural gas—which largely comes from fracking—likely has no benefit in cutting our greenhouse gas emissions, and its increase in supply and decrease in electricity price very likely prolongs the day when renewable energy will be more economically attractive. If the U.S. has no plan in place to cap greenhouse gas emissions to steadily and strategically transition to renewable energy, natural gas will not act as a bridge fuel. (Scholars have argued this here, here, and here.)
I’ll write about the research into fracking’s local pollutive effects in a later article—but now we know that fracking brings likely little benefits, no benefits, or very possibly detrimental effects in mitigating climate change.