<P> Hydrogen is mainly used for the production of ammonia via Haber process . In this case, the hydrogen is produced in situ . Ammonia is the major component of most fertilizers . </P> <P> Earlier it was common to vent the surplus hydrogen off, nowadays the process systems are balanced with hydrogen pinch to collect hydrogen for further use . </P> <P> Hydrogen may be used in fuel cells for local electricity generation, making it possible for hydrogen to be used as a transportation fuel for an electric vehicle . </P> <P> Hydrogen is also produced as a by - product of industrial chlorine production by electrolysis . Although requiring expensive technologies, hydrogen can be cooled, compressed and purified for use in other processes on site or sold to a customer via pipeline, cylinders or trucks . The discovery and development of less expensive methods of production of bulk hydrogen is relevant to the establishment of a hydrogen economy . </P>

Where does most of the hydrogen come from