How is hydrogen produced?
To produce hydrogen, it must be separated from the other elements in the molecules where it occurs. There are many different sources of hydrogen and ways for producing it for use as a fuel. The two most common methods for producing hydrogen are steam-methane reforming and electrolysis (splitting water with electricity. Researchers are exploring other hydrogen production methods or pathways.
Hydrogen production processes
Steam-methane reforming is a widely used method of commercial hydrogen production
Steam-methane reforming currently accounts for nearly all commercially produced hydrogen in the United States. Commercial hydrogen producers and petroleum refineries use steam-methane reforming to separate hydrogen atoms from carbon atoms in methane (CH4). In steam-methane reforming, high-temperature steam (1,300°F to 1,800°F) under 3–25 bar pressure (1 bar = 14.5 pounds per square inch) reacts with methane in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide (CO2).
Natural gas is the main methane source for hydrogen production by industrial facilities and petroleum refineries. Landfill gas/biogas, which may be called biomethane or renewable natural gas, is a source of hydrogen for several fuel cell power plants in the United States. Biofuels and petroleum fuels are also potential hydrogen sources.
Electrolysis uses electricity to produce hydrogen
Electrolysis is a process that splits hydrogen from water using an electric current. Electrolysis is commonly used to demonstrate chemical reactions and hydrogen production in high school science classes. On a large, commercial scale, the process may be referred to as power-to-gas, where power is electricity and hydrogen is gas. Electrolysis itself does not produce any byproducts or emissions other than hydrogen and oxygen. The electricity for electrolysis can come from renewable sources, nuclear energy, or fossil fuels. If the electricity for electrolysis is produced from fossil fuel (coal, natural gas, and petroleum) or biomass combustion, then the related environmental effects and CO2 emissions are indirectly associated with that hydrogen.
Other methods of producing hydrogen
Research is underway to develop other ways to produce hydrogen and a few include:
- Using microbes that use light to make hydrogen
- Converting biomass into gas or liquids and separating the hydrogen
- Using solar energy technologies to split hydrogen from water molecules
Categories of hydrogen
Hydrogen producers, marketers, government agencies, and other organizations might categorize or define hydrogen according to the energy sources for its production, and they use a color code to categorize hydrogen. For example, hydrogen produced using renewable energy might be referred to as renewable hydrogen or green hydrogen. Hydrogen produced from coal may be called brown hydrogen, and hydrogen produced from natural gas or petroleum might be referred to as grey hydrogen. Brown or grey hydrogen production combined with carbon capture and storage/sequestration might be referred to as blue hydrogen. Hydrogen produced with nuclear energy may be called pink hydrogen or clean hydrogen.
Last updated: January 21, 2022