A fuel control system is provided. The fuel control system includes an electronic control system coupled to a pair of control valves for blending pipeline fuel with waste fuel at a blend ratio for controlling fuel flow to an internal combustion engine. The fuel control system can estimate energy content of the fuel mixture to compensate the blend ratio. The fuel control system can use engine operational parameters to compensate the blend ratio. Typically, the system will use the operational parameter of output power or exhaust emissions to compensate the blend ratio. Further, the fuel control system can prioritize variation from the blend ratio or variation from a desired power output when the blend ratio cannot generate the desired power output. The fuel control system can also be equipped with engine speed/load controls, misfire, ignition timing and knock detection capabilities.