Dual-FuelTM technologies: Diesel and CNG

Current Dual-Fuel™ Technology Dual-Fuel™ is fitted onto a standard diesel engine, which operates unchanged, except power is generated by mostly clean natural gas. A measured quantity of natural gas is mixed with the air just before it enters the cylinder and compressed to the same levels as the diesel engine to maintain efficiency. The natural gas mixture does not ignite spontaneously under compression, so the Dual-Fuel™ engine uses a small injection of diesel fuel, around 10% of the total energy of the fuel, to ignite the main charge of gas and air. This small "pilot" injection acts like a multitude of microscopic spark-plugs, setting off clean and efficient combustion of the lean gas-air mixture. Natural gas burns cleaner than diesel due to its inherently low carbon content.
When Natural gas replaces 90% of the diesel through Dual-Fuel™ it can reduce CO2 emissions by up to 25%, yet fuel-efficiency and power remain equivalent to that of the original diesel engine.
Clean Air Power believes that no dedicated natural gas trucks can match a Dual-Fuel™ truck for efficiency and performance.

Source: CLEAN AIR POWER