Hydrogen production

Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Most hydrogen is gray hydrogen made through steam methane reforming. In this process, hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide. When carbon capture and storage is used to remove a large fraction of these emissions, the product is known as blue hydrogen. Green hydrogen is usually understood to be produced from renewable electricity via electrolysis of water. Less frequently, definitions of green hydrogen include hydrogen produced from other low-emission sources such as biomass. Producing green hydrogen is currently more expensive than producing gray hydrogen, and the efficiency of energy conversion is inherently low. Other methods of hydrogen production include biomass gasification, methane pyrolysis, extraction of underground natural hydrogen, and in situ hydrogen synthesis. As of 2023, less than 1% of dedicated hydrogen production is low-carbon, i.e. blue hydrogen, green hydrogen, and hydrogen produced from biomass. In 2020, roughly 87 million tons of hydrogen was produced worldwide for various uses, such as oil refining, in the production of ammonia through the Haber process, and in the production of methanol through reduction of carbon monoxide. The global hydrogen generation market was fairly valued at US$155 billion in 2022, and expected to grow at a compound annual growth rate of 9.3% from 2023 to 2030.