Hydrogen economy

It has been suggested that this article be merged into Low-carbon economy. (Discuss) Proposed since March 2024.

The hydrogen economy is an umbrella term that draws together the roles hydrogen can play alongside low-carbon electricity to decarbonize those sectors and activities which may be technically difficult to decarbonize through other means, or where cheaper and more energy-efficient clean solutions are not available.^[2] In this context, hydrogen economy encompasses hydrogen's production through to end-uses in ways that substantively contribute to phasing-out fossil fuels and limiting climate change.

Most hydrogen produced today is gray hydrogen, made from natural gas through steam methane reforming (SMR) which accounted for 1.8% of global greenhouse gas emissions in 2021.^[3] Low-carbon hydrogen, which is made using SMR with carbon capture and storage (blue hydrogen), or through electrolysis of water using renewable power (green hydrogen), accounted for under 1% of production.^[4] Virtually all of the 100 million tonnes^[5] of hydrogen produced each year is used in oil refining (43% in 2021) and industry (57%), principally in the manufacture of ammonia for fertilizers, and methanol.^{[6]: 18, 22, 29}

In its contribution to limiting global warming to 1.5 °C, it is broadly envisaged that the future hydrogen economy replaces gray hydrogen with blue and predominantly green hydrogen, produced in greater total volumes, to provide for an expanded set of end-uses.^[7] These are likely to be in heavy industry (e.g. high temperature processes alongside electricity, feedstock for production of green ammonia and organic chemicals, as alternative to coal-derived coke for steelmaking), long-haul transport (e.g. shipping, aviation and to a lesser extent heavy goods vehicles), and long-term energy storage.^[7][8] Other applications, such as light duty vehicles and heating in buildings, are no longer part of the future hydrogen economy, primarily for economic and environmental reasons.^[9][10] These reasons include the difficulty of developing long-term storage, pipelines, and engine equipment, safety concerns since hydrogen is highly explosive, and the inefficiency of hydrogen compared to direct use of electricity.

As of 2023^[update] there are no real alternatives to hydrogen for ammonia production for fertilizer, hydrogenation, hydrocracking, and hydrodesulfurization.^[11] The extent to which hydrogen will be used to decarbonise chemical feedstock, long haul aviation and shipping, and long-term energy storage is likely to be influenced by the evolving production costs of low- and zero-carbon hydrogen. Estimates of future costs face numerous uncertainties – such as the introduction of carbon taxes, geography and geopolitics of energy, energy prices, technology choices, and their raw material requirements – but it is likely that green or white (underground^[12]) hydrogen will see the greatest reductions in production cost over time.^[13]