Fracking for natural gas

In this Jan. 17, 2013, photo, the truck and trailer rig with a huge converted engine that runs a pump used in extracting gas from wells, sets outside the Cummins Bridgeway facility in Gibsonia, Pa. The unit on the front of the trailer cools the 50 liter, 16 cylinder Cummins diesel engine that occupies the center of the trailer. The pump for the fracking fluid is at the rear.

Credit: AP Photo/Keith Srakocic