Natural gas is far “greener” than coal and other fossil fuels, but environmentalists worry that leaks of methane – a powerful contributor to global warming – may offset the climate benefits of natural gas.

A car-mounted system that can detect leaks of methane from pipelines and other sources is being deployed by Pacific Gas & Electric Co. to monitor its 45,000 miles of pipelines. The system is manufactured by Piccaro, Inc., of Santa Clara.

“This technology is going to put us in a whole new league in terms of our ability to safeguard our system,” said Kevin Knapp, PG&E’s Vice President, Gas Distribution Maintenance and Construction.

The detector, which Picarro calls “Surveyor,” can not only detects miniscule amounts of methane in the air, but it can tell whether the methane originates from a leaking pipeline or from natural sources such as a swamp or decaying garbage, due to slight differences in the carbon atoms in the gas.

The car-mounted unit sucks in ambient air and routes it to a yard-long tube where it is bombarded by a laser that can detect methane at the level of a few parts per billion.