Concept
Hydrogen fuel refers to hydrogen which is burned as fuel with pure oxygen (not to be confused with atmospheric gases). It can be a zero-carbon fuel, provided that it is created in a process that does not involve carbon. However, most hydrogen comes from fossil fuels, resulting in carbon dioxide emissions. Depending on the source and the resulting environmental impact, hydrogen that is sourced from various methods can be referred to by a variety of terms using metaphorical names of colors: white, green, blue, grey, black, or brown hydrogen. It can be used in fuel cells or internal combustion engines (see HICEV). Regarding hydrogen vehicles, hydrogen has begun to be used in commercial fuel cell vehicles such as passenger cars, and has been used in fuel cell buses for many years. It is also used as a fuel for spacecraft propulsion and is being proposed for hydrogen-powered aircraft. The fuel technology has seen awakened interest from automakers who claim it is comparatively cheap and safer to incorporate into the modern vehicle architecture over recent challenges faced by electric vehicle makers. Hydrogen production Because pure hydrogen does not occur naturally on Earth in large quantities, it usually requires a primary energy input to get produced on an industrial scale. Hydrogen fuel can be produced from methane or by electrolysis of water. As of 2020, the majority of hydrogen (~95%) is produced from fossil fuels by steam reforming or partial oxidation of methane and coal gasification with only a small quantity by other routes such as biomass gasification or electrolysis of water. Steam–methane reforming, the current leading technology for producing hydrogen in large quantities, extracts hydrogen from methane. However, this reaction releases fossil carbon dioxide and carbon monoxide into the atmosphere, which are greenhouse gases exogenous to the natural carbon cycle, and thus contribute to climate change.
