No one knows just how much methane—a potent greenhouse gas—leaks from natural gas wells and pipelines. A new natural-gas sensing system from Picarro, a Santa Clara, California-based company, could help. It’s making it far easier and faster—and potentially cheaper—to detect and pinpoint the source of natural gas emissions.

While burning natural gas to generate electricity releases about half as much carbon dioxide as burning coal, such a benefit could be offset by methane accidently released during drilling or the transmission of natural gas. Some natural gas leaks into the atmosphere while it’s being produced at wells, compressed and shipped to cities, or distributed to homes and vehicles. The full extent of those leaks aren’t known because it isn’t practical to measure them (see “Just How Green Is Natural Gas?” and “Natural Gas May Be Worse for the Planet than Coal”).

It’s relatively easy to measure the amount of methane in the air, but it’s difficult to know exactly where it came from. That’s necessary to determine which gas drilling company, for example, might have a particularly leaky system. It’s also important because there are many sources of methane other than the natural gas distribution system, including natural methane leaks and methane produced by livestock and in landfills. “It is complicated to attribute accurately fugitive emissions to one particular source using [conventional] air-sampling tools,” says Francis O’Sullivan, a researcher at MIT who studies methane emissions.

Picarro says its new technology makes pinpointing the source far easier. Its mobile measurement system is mounted on a car, allowing technicians to drive through an area to quickly pinpoint the source of leaks in real time. It combines an advanced methane detector—based on technology from Stanford University that it brought to market in 2005—with wind-direction sensors, isotope detectors, and proprietary algorithms. The isotope measurements can determine whether the gas comes from a biological source like a landfill or from fossil fuel. Methane measurements, integrated with wind data and information about the precise location and the speed of the car, is used to plot the source of the leak on Google Maps.

In one test, the system detected a leak as technicians drove past a petrochemical plant, which would probably have been assumed to be the source of the methane, says Eric Crosson, Picarro’s chief technology officer. But the isotope measurements identified the source of the leak as biological, and the wind measurements indicated that it was coming from an empty field, which turned out to be a leaking landfill. He says determining this sort of thing could have taken days or weeks with previous technology.

The technology was recently used to survey all 785 miles of roads in Boston over the course of six weeks. It identified 3,356 spots where methane levels were more than 15 times higher than normal. This level of analysis goes well beyond what natural gas companies normally do to detect leaks, in part because they’re mostly concerned with larger leaks. In Boston, only six of the leaks were considered large enough for the local utility to do anything about them.

PG&E in California, under pressure to improve its practices after a large natural gas explosion in 2010, has also adopted the Picarro technology. PG&E says the technology is a thousand times more sensitive than conventional methods, and lets the company find and fix leaks far more quickly.

Whether Picarro’s technology, and other technology for studying methane leaks, is deployed widely could depend on regulation. “Absolutely there is a need for better measurements,” says O’Sullivan. “The question remains, who will pay for it?”