Green hydrogen
Green hydrogen is hydrogen produced by the electrolysis of water using renewable electricity. Production of green hydrogen causes significantly lower greenhouse gas emissions than production of grey hydrogen, which is derived from fossil fuels without carbon capture.
Green hydrogen's principal purpose is to help limit global warming, reduce fossil fuel dependence by replacing grey hydrogen, and provide for an expanded set of end-uses in specific economic sectors, sub-sectors and activities. These end-uses may be technically difficult to decarbonize through other means such as electrification with renewable power. Its main applications are likely to be in heavy industry, shipping, and long-term energy storage.
As of 2021, green hydrogen accounted for less than 0.04% of total hydrogen production. As of 2024, producing green hydrogen costs around 1.5 to six times more than producing hydrogen from fossil fuels without carbon capture.
Definition
Most commonly, green hydrogen is defined as hydrogen produced by the electrolysis of water, using renewable electricity. In this article, the term green hydrogen is used with this meaning.Precise definitions sometimes add other criteria. The global Green Hydrogen Standard defines green hydrogen as "hydrogen produced through the electrolysis of water with 100% or near 100% renewable energy with close to zero greenhouse gas emissions." In integrated cases water can also provide services back to the renewable energy source such as when water cools floatovoltaics to improve efficiency of solar energy conversion, which in turn is used to generate green hydrogen from the water.
A broader, less-used definition of green hydrogen also includes hydrogen produced through various other methods that produce relatively low emissions and meet other sustainability criteria. For example, these production methods may involve nuclear energy or biomass feedstocks.
Electrolysis
Green hydrogen is primarily produced by electrolysis, in which electricity from renewable sources is used to split water into hydrogen and oxygen. The process is at most 80% efficient. Producing a kilogram of hydrogen through electrolysis requires around nine litres of water.The business consortium Hydrogen Council said that, as of December 2023, manufacturers are preparing for a green hydrogen expansion by building out the electrolyzer pipeline by 35 percent to meet the needs of more than 1,400 announced projects.
Main methods
- Alkaline Electrolyzers : A mature and cost-effective technology used primarily for large-scale, steady hydrogen production. They operate at 70–90 °C using a potassium hydroxide electrolyte and non-precious metal catalysts. While robust, they are less suited for intermittent renewable energy sources.
- Proton Exchange Membrane Electrolyzers : Known for compact design and high responsiveness, PEM systems operate at 50–80 °C and produce high-purity hydrogen. Their ability to quickly adjust to fluctuating power makes them ideal for coupling with wind and solar, though reliance on platinum and iridium raises capital costs. Current research targets alternative catalysts and recycling strategies.
- Solid Oxide Electrolyzers : Operating at 500–1000 °C, SOECs convert electrical and thermal energy into hydrogen with high efficiency. They are well-suited for integration with industrial heat sources or for co-electrolysis of steam and CO2 to form syngas. Challenges include high material stress and slow dynamic response.
- Anion Exchange Membrane Electrolyzers : AEMs are emerging as promising systems that blend AE affordability with PEM flexibility. Designed to use non-noble metals and solid electrolytes, they offer lower-cost solutions with improved dynamic performance.
Alternative production pathways
- Photoelectrochemical Water Splitting: Merging light capture and electrolysis using semiconductor-based cells to mimic photosynthesis. Stable photoelectrodes and scalable device design.
- Biological Hydrogen Production: Leveraging algae and bacteria in biophotolysis or dark fermentation are under active research investigation. While environmentally promising, low yields remain a barrier.
- Thermochemical Water Splitting: Using High heat from nuclear or solar sources to trigger chemical water-splitting reactions in solar-rich regions and industrial symbiosis.
- Biochar-assisted: Biochar-assisted water electrolysis reduces energy consumption by replacing the oxygen evolution reaction with the biochar oxidation reaction. An electrolyte dissolves the biochar as the reaction proceeds. A 2024 study claimed that the reaction was 6× more efficient than conventional electrolysis, operating at <1 V, without production using ~250 mA/gcat current at 100% Faradaic efficiency. The process could be driven by small-scale solar or wind power.Cow manure biochar operated at only 0.5 V, better than materials such as sugarcane husks, hemp waste, and paper waste. Almost 35% of the biochar and solar energy was converted into hydrogen. Biochar production is not carbon neutral.
- Scrap iron: Green hydrogen generation is possible from scrapped iron by reacting with water in an exothermic reaction. It is called steam-iron process and a production method is called Lane hydrogen producer. Good quality magnetite,, is a valuable byproduct.
- Scrap aluminum: Green hydrogen production is possible from scrapped aluminum by reacting with water in an exothermic reaction. Good quality aluminum hydroxide and heat are valuable byproducts.
Uses
Hydrogen fuel can produce the intense heat required for industrial production of steel, cement, glass, and chemicals, thus contributing to the decarbonisation of industry alongside other technologies, such as electric arc furnaces for steelmaking. However, it is likely to play a larger role in providing industrial feedstock for cleaner production of ammonia and organic chemicals. For example, in steelmaking, hydrogen could function as a clean energy carrier and also as a low-carbon catalyst replacing coal-derived coke.
Hydrogen used to decarbonise transportation is likely to find its largest applications in shipping, aviation and to a lesser extent heavy goods vehicles, through the use of hydrogen-derived synthetic fuels such as ammonia and methanol, and fuel cell technology. As an energy resource, hydrogen has a superior energy density versus batteries. For light duty vehicles including passenger cars, hydrogen is far behind other alternative fuel vehicles, especially compared with the rate of adoption of battery electric vehicles, and may not play a significant role in future.
Green hydrogen can also be used for long-duration grid energy storage, and for long-duration seasonal energy storage. It has been explored as an alternative to batteries for short-duration energy storage.
Hydrogen can be combined with carbon dioxide to produce green methanol, a liquid fuel.
Green hydrogen is considered a key solution for decarbonizing sectors that are difficult to electrify, including steelmaking, chemicals, long-distance transport, and heavy industry. It is also used as an energy storage medium, enabling excess renewable electricity to be stored and converted back into power when needed.
Market
As of 2022, the global hydrogen market was valued at $155 billion and was expected to grow at an average of 9.3% between 2023 and 2030.Of this market, green hydrogen accounted for about $4.2 billion.
Due to the higher cost of production, green hydrogen represents a smaller fraction of the hydrogen produced compared to its share of market value.
The majority of hydrogen produced in 2020 was derived from fossil fuel. 99% came from carbon-based sources. Electrolysis-driven production represents less than 0.1% of the total, of which only a part is powered by renewable electricity.
As of 2024, producing green hydrogen costs around 1.5 to six times more than producing hydrogen from fossil fuels without carbon capture. The current high cost of production is the main factor limiting the use of green hydrogen. A price of $2/kg is considered by many to be a potential tipping point that would make green hydrogen competitive against grey hydrogen.
Green hydrogen production costs are forecasted to fall due to declines in the costs of renewable electricity and electrolysers. The cost of solar and wind power declined dramatically from 2009 to 2024. Analysts project that electrolyser costs will decline as the green hydrogen industry grows, due to economies of scale and learning-by-doing. The cost of electrolysers fell by 60% from 2010 to 2022, though it rose 50% between 2021 and 2024. Carbon taxes on grey hydrogen would contribute to making green hydrogen cost-competitive.
In 2025 the IEA forecast a likely production of 37 million tonnes in 2030, a reduction of 12 million from its 2024 forecast. IEA executive Fatih Birol said that there were concerns that hydrogen has gone through another hype cycle, just like in the 1970s, 1990s and early 2000s.
Production facilities
As of 2023, the global hydrogen market is about 97,000 thousand tonne per year. Of this, approximately 4,687 kt/y is blue hydrogen, and 146 kt/y is green hydrogen. In 2023, the IEA estimate that 218 kt/y of green hydrogen production capacity had been installed globally. The green hydrogen is manufactured in the following facilities, and others. Some of these feed directly into green ammonia plants or other uses for hydrogen.| Facility name | Date production started | Production kt/y | Country |
| Songyuan Hydrogen Energy Industrial Park | 2025 | 45.0 | China |
| Sinopec Kuqa Xinjiang Green Hydrogen Plant | 2023 | 44.1 | China |
| Ningxia Baofeng Energy Group | 2021 | 25.6 | China |
| Industrias Cachimayo | 1965 | 4.2 | Peru |
| Inner Mongolia Energy Department | 2021 | 12.0 | China |
| Cavendish NextGen Hydrogen Hub | 2023 | 3.7 | United States |
| Shell China - Zhangjiakou | 2022 | 3.4 | China |
| Iberdrola - Puertollano I | 2022 | 3.0 | Spain |
| Air Liquide Becancour | 2020 | 3.0 | Canada |
| Trailblazer - Siemens-Air Liquide Oberhausen, Phase 1 | 2024 | 3.0 | Germany |
| EBIC - Ammonia plant -phase 1 | 2022 | 2.2 | Egypt |
| PetroChina Yumen Oilfield - Phase 1 | 2023 | 2.0 | China |