The process of converting natural gas to hydrogen is called steam methane reforming (SMR). This accounts for about 95% of the hydrogen used by industry. The technology is very scalable and mature, providing the current low-cost production method in many parts of the world. The downside of the process is that it produces CO2 which, traditionally, is released to atmosphere. Methods have been developed to capture this CO2 which would enable it to be sequestered and stored if appropriate.
Government policy is required to drive industry towards ensuring capture becomes the norm.
There are variations to this technology, such as autothermal reforming (ATR). A further process called partial oxidation (POX) exists and is especially suited to solid materials such as coal.
The first commercial technology to produce pure hydrogen, dating back to the 1920s, was water electrolysis. The process involves passing an electrical current through water which causes the water to dissociate into its constituents – oxygen and hydrogen. This technique was enhanced by the addition of a salt to the water – turning it alkaline – which reduced the amount of energy required to drive the process. If the right salt is added, the base process for all chlorine chemistry materials is created. Alkaline systems use the most mature electrolysis technology and dominate the market accounting for nearly all the installed electrolysis capacity worldwide.
Recently a new electrolysis process called Proton Exchange Membrane (PEM) has been developed.
These systems are currently smaller but increasing in size and number due to their ability at accept fluctuating power input, such as is available from solar and wind, and deliver hydrogen at high purity and pressure. As it is a relatively new technology, cost reductions are expected with time and increased scale.
Other technologies are also being developed such as Anion Exchange Membrane (AEM) and Solid Oxide Electrolysis (SOE). AEM systems currently tend to be small but have the potential to be ‘racked’ together to increase output. SOE systems are high temperature (from 600 to 900°C) and if waste heat is available then this can be used to improve the energy needed for hydrogen production. These systems offer advantages in different sectors