Shale gas is widely touted as a "clean" fossil fuel that can serve as a bridge to renewable energy. But according to a new study by Cornell University researchers, it actually has a larger carbon footprint than coal, oil and conventional natural gas, at least over a 20-year period. That's largely because shale-gas wells leak large amounts of methane - a component of natural gas, but also a potent greenhouse gas, even more effective at trapping heat than carbon dioxide. When leaked methane is calculated with the greenhouse gases emitted by burning shale gas, the fuel loses much of its green luster, the study's authors argue.
"The large greenhouse gas footprint of shale gas undercuts the logic of its use as a bridging fuel over coming decades, if the goal is to reduce global warming, " lead author Robert Howarth tells the AFP. "The full footprint should be used in planning for alternative energy futures that adequately consider global climate change." Shale drilling already faces scrutiny for its use of hydraulic fracturing, or "fracking," in which pressurized water, sand and chemicals are pumped deep underground to loosen rock and release more gas. While the EPA investigates claims that fracking poisons groundwater, however, Howarth says he's found an even bigger flaw with shale drilling - one that belies the very argument used to justify the current U.S. shale-gas boom. Plus, he points out that his team's calculations for methane leakage are based on "best practices" estimates, but that actual leakage rates could be much higher. "No one knows for sure to what extent industry uses best practices; and unfortunately, at least in the U.S., industry does not want government or the public to know," he says. "The [EPA] has proposed rules that would require industry to report methane emissions, but several companies have sued the EPA to try to prevent such reporting."
According to the U.S. Energy Department, the country's total natural gas output will grow by 20 percent in the next 25 years, at which point nearly half of all U.S. gas production will come from shale - up from just 16 percent in 2009. Shale gas is increasingly popular because vast deposits exist underneath the U.S., and because new drilling techniques like fracking make it more economical to extract. It has looked especially good to many ever since Japan's nuclear crisis began last month, too. But as Howarth argues, it's unwise to look at shale gas through green-colored glasses. "We should not proceed to view shale gas as a 'transitional fuel' to be used over the next few decades to replace other fossil fuels," he says, "but rather work harder to move toward truly green renewable fuels as quickly as possible, such as wind and solar."