Clean Energy Fuels, a California firm founded by billionaire T. Boone Pickens, signed a 15-year agreement with locally-based PS Energy Group to expand compressed natural gas fueling capacity in the metro area.

The expansion news comes as Atlanta Gas Light also is trying to get into the CNG business, and as state regulators and legislators push for more infrastructure for dispensing the fuel.

CNG is cheaper than gasoline, but works only in vehicles equipped to burn it. A chicken and egg problem has dogged its development as a fuel source. Consumers don't buy cars because there aren't enough stations and investors don't build stations because there aren't enough cars.

The PS Energy-Clean Energy project is funded partly by a federal grant, and partly with private investment from Clean Energy, said James Harger, the California's firm's chief marketing officer.

Clean Energy will increase the capacity of an existing PS Energy station in downtown Atlanta, add new stations at East Point, Lithonia and Tucker and operate all four. The new capacity should be available by the fall.