With more than 500,000 active natural gas wells in the U.S., and thousands more transmission and distribution lines, there's a lot of potential for leakage. The fracking revolution has spread the risk of these "fugitive emissions" far and wide, and there's no good detection technology widely in use to deal with the problem.
Methane (which makes up 90% of natural gas) is a potent greenhouse gas, 25 times more powerful than carbon dioxide over a 100-year period. Though the leaks at individual sites may not be enormous, it's worth finding and plugging them from a climate point of view. And now a dozen companies are working on new methane-monitoring systems.
Physical Sciences (PSI), from Andover, Massachusetts, is developing a drone that uses an infrared laser beam. In standby mode, it sits on a charging platform monitoring the wellhead area. When it measures an excess of methane along the beam path, it automatically rises into the air and runs a search pattern of the area. If it finds a possible leak, it reports that information back.
The gas leak detector itself, developed with Heath Consultants, is already in wide use—but normally for pipelines, not fracking sites. The new project model—funded through the Department of Energy's ARPA-E research agency—is miniaturized, made airborne, and designed to be used at many more sites.
"There is a significant emphasis on developing lower-cost technologies to find leaks where they haven't been found before," says PSI's Michael Frish. "In the past, detection has been about safety. Now the emphasis is on not only protecting pipelines from explosions, but also protecting against the environmental impact of relatively small leaks."
The two-feet-wide quadrotor drones measure methane by beaming an infrared beam and measuring the amount of light reflected back. The spectrometer compares the effect from switching between a wavelength attuned to the methane's own wavelength and another control-level wavelength. It's accurate as far as 1,000 feet, Frish says.
There's been a lot of conjecture about precisely how much methane fracking sites are releasing. Estimates range from 1%-4% of the gas the industry recovers. But even at the lower end, these emissions are worth detecting and stopping. Methane is a more serious climate issue than most other pollutant gases.