Staff Sgt. Kevin Jones, 28th Logistics Readiness Squadron vehicle maintenance craftsman, loosens a bolt while replacing an exhaust gas recirculation valve on a bio-diesel engine truck here, July 15. The exhaust gas recirculation valve recirculates unburned fuel back through the engine intake to allow cleaner emissions. (U.S. Air Force photo/Airman 1st Class Joshua J. Seybert)