Internal combustion engine

An internal combustion engine is an engine that is powered by the expansion of hot combustion products of fuel directly acting within an engine. A piston internal combustion engine works by burning hydrocarbon or hydrogen fuel that presses on a piston; and a jet engine works as the hot combustion products press on the interior parts of the nozzle and combustion chamber, directly accelerating the engine forwards. The rotary combustion engine uses a rotor instead of reciprocating pistons.

Fuel pollution

• Hydrogen is not found naturally in the environment in a usable form. Production is usually from organic compounds and most of that is from fossil fuels. This usually, but not necessarily, involves the production and release of relatively large quantities of carbon dioxide to atmosphere. It can also be produced by electrolysis of water, with the only direct emission being oxygen, assuming the water is pure and non-reactive electrodes are used.