7 Hydrogen technologies

This chapter talks about hydrogen production from a wide variety of primary energy sources and different production technologies. Techniques based on fossil fuels like steam reforming of natural gas, gasification of coal or partial oxidation of heavy oil are state of the art technologies and used for decades. Besides these mature processes, there are some technologies, e.g. electrolysis, used only for special applications, and others, like photoelectrolysis or photobiological methods, which are the object of current research activities and have to be developed for the industrial scale. The hydrogen production process is illustrated, and chemical reactions in electrolyzers are analyzed. Steam reforming of natural gas is one of the most effective methods of hydrogen production. On the account of sustainability, in the long term, hydrogen must be produced from renewable energy sources. A newly developed type of electrolysis is the so called photoelectrolysis. Biomass resources, such as consumer waste, agriculture residues or biomass specially grown for energy use, could be used for hydrogen production by gasification or by pyrolysis. Researchers are currently focusing on hydrogen production by catalytic reforming of biomass pyrolysis products. Hydrogen production is also done by fermentation of biomass by microorganisms. The provision of cost competitive hydrogen in sufficient quantity and quality is the groundwork of a hydrogen energy economy. If there are no suitable technologies for economic processes without greenhouse gas emissions or other non-sustainable environmental impacts, hydrogen production will be the bottleneck of the future energy economy.