Hydrogen internal combustion engine vehicle

A hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen vehicle using an internal combustion engine.^[1] Hydrogen internal combustion engine vehicles are different from hydrogen fuel cell vehicles (which utilize hydrogen electrochemically rather than through combustion). Instead, the hydrogen internal combustion engine is simply a modified version of the traditional gasoline-powered internal combustion engine.^[2][3] The absence of carbon means that no CO₂ is produced, which eliminates the main greenhouse gas emission of a conventional petroleum engine.

As pure hydrogen does not contain carbon, there are no carbon-based pollutants, such as carbon monoxide (CO) or hydrocarbons (HC), nor is there any carbon dioxide (CO₂) in the exhaust. As hydrogen combustion occurs in an atmosphere containing nitrogen and oxygen, however, it can produce oxides of nitrogen known as NO_x. In this way, the combustion process is much like other high temperature combustion fuels, such as kerosene, gasoline, diesel or natural gas. Therefore, hydrogen combustion engines are not considered zero emission.^{[citation needed]}