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Hydrogen is a promising and versatile form of clean energy. It can be burned to produce heat without releasing any carbon dioxide pollution, unlike fossil fuels like natural gas and coal. Inside a fuel cell, hydrogen can be used to produce a chemical reaction that generates electricity without releasing any greenhouse gases at all.
For certain applications that require very high temperatures like making steel and cement, hydrogen might be the only viable climate-friendly alternative to fossil fuels. It can be used to create renewable biodiesel from plants, power jet engines in airplanes, and fuel personal and fleet vehicles. Hydrogen can also serve as energy storage. There is even potential for hydrogen to generate electricity in power plants instead of natural gas.
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Hydrogen is the most common element in the universe, and the basis for all the other elements. Stars like the sun are mostly made of hydrogen which, under the extreme pressure generated by a star’s powerful gravity, fuses into heavier elements, like carbon, oxygen, aluminum, and iron. Hydrogen is best known as one of the two elements that make water (H2O), but it is also found in all fossil fuels, which are classified as hydrocarbons.
Although nine in every ten atoms in the visible universe are hydrogen atoms, it is rare to find hydrogen in its natural state on Earth because it is so light that it easily escapes into space. Most hydrogen on Earth is part of water or fossil fuels and needs to be extracted before it can be used as energy. However, recent research indicates that substantial underground reserves of naturally-occurring hydrogen might exist and could be tapped directly.
Hydrogen can be extracted from other materials in many different ways. Experts have associated each type of hydrogen with a color for ease of communication, but hydrogen is actually always colorless (note that experts do not all agree on which color to assign to which type of hydrogen production!). Regardless of color, all hydrogen extraction methods use one of four underlying processes: extraction through electricity (electrolysis), direct solar water splitting (photolytic process), heat and chemistry (thermochemical process), or bacteria and microalgae (biological process).
For electrolysis, an electric current is run through water, splitting it into its two core components, oxygen and hydrogen. The photolytic process uses energy from light to directly split water into its two components. High heat and chemistry are used in many different types of hydrogen production, including the most widespread one, natural gas reforming. Finally, some microbes produce hydrogen naturally as a waste product, or can be triggered to do so through human intervention.
By far the most common way to extract hydrogen is by reforming natural gas using high-temperature steam. This type of hydrogen is known as gray hydrogen, and represents about three quarters of produced hydrogen. Unfortunately, this method releases significant carbon emissions, between 9 and 11 tons of carbon dioxide for every ton of hydrogen. In contrast, green and yellow hydrogen (extracted from water using renewable energy-powered electrolysis) have much lower carbon footprints than gray hydrogen, but cost up to 4 times more.
Color/Type
Carbon emissions
Cost (per kg)
Description
Pink, red, and purple hydrogen
0.1–0.6 kg
$4.2–$7
Pink, red, and purple hydrogen are produced by using nuclear power, without directly releasing carbon dioxide or other greenhouse gases. Pink hydrogen is produced with electricity generated from nuclear plants, red hydrogen is produced using nuclear heat, and purple hydrogen is produced using both nuclear electricity and heat, which makes it the most efficient method.
Green hydrogen
0.7–2.8 kg
$2.6–$23
Green hydrogen is extracted from water, using renewable energy. About 1% of the hydrogen humans use is produced in this way. Producing green hydrogen releases no carbon dioxide or other greenhouse gases directly, but is very energy-intensive, which makes it relatively expensive since electricity prices represent 47–78% of production costs. Green hydrogen will become more competitive as renewable energy continues to become cheaper.
Yellow hydrogen
1.7–4.4 kg
$1.2–$3.1
Yellow hydrogen is a subset of green hydrogen that has been extracted from water using solar energy specifically. Since solar energy is falling in price rapidly, yellow hydrogen is becoming cheaper to produce.
Turquoise hydrogen
1.9–4.8 kg
(as a solid)
$1.6–$3.4
Turquoise hydrogen is extracted from natural gas through high heat. This technique, called methane pyrolysis, has not yet been proven at scale but is promising. The carbon resulting from the process is mostly solid so it is not emitted into the atmosphere.
Blue hydrogen
3–7 kg
$1.2–$2.3
Blue hydrogen is produced in the same way as gray hydrogen, but the carbon dioxide emitted during production is captured. This hybrid process results in seven tons or fewer of carbon dioxide being released into the atmosphere for every ton of hydrogen produced. Carbon capture and storage is expensive, so this form of hydrogen is not widespread.
Gray hydrogen
9–11 kg
$0.7–$2.1
About 76% of the hydrogen currently being produced is gray hydrogen that has been extracted from natural gas using steam methane reforming. The process releases significant carbon emissions.
Black and brown hydrogen
18–20 kg
$1.3–$2.5
Black hydrogen is extracted from bituminous (black) coal. Brown hydrogen is extracted from lignite (brown coal). Both methods release significant carbon dioxide emissions (about 19 tons of carbon dioxide for every ton of hydrogen produced).
White hydrogen
TBD
White hydrogen is naturally generated underground, when water and iron-rich minerals interact at high temperatures and pressures. The existence of natural underground deposits of hydrogen has been known since the 1930s, but companies—particularly major mining and oil companies—have only recently become interested in locating and exploiting them commercially. The economic viability of such projects remains uncertain.
Orange hydrogen
Orange hydrogen is white hydrogen made artificially in a process recently developed by the French National Center for Scientific Research. Carbon dioxide-enriched water is pumped into iron-rich underground formations. The water loses its carbon dioxide, gains hydrogen, and is pumped back up where the extra hydrogen is recovered. By trapping carbon dioxide underground, the process also serves as long-term carbon storage.
Gold hydrogen
Gold hydrogen is created using bacteria, which are pumped into depleted oil wells along with some nutrients. The bacteria feed off the oil, releasing hydrogen and carbon dioxide. If the hydrogen can be economically recovered while the carbon is kept underground, this method could be climate friendly. Companies like Gold H2 have completed field trials.
Color TBD (Plastic Hydrogen)
Rice University researchers have discovered a way to make hydrogen from plastic waste, by flash heating it for four seconds to almost 5,000°F. As of October 2025, this process has not yet been attributed a color.
Notes
Carbon emissions are measured as the quantity of greenhouse gases emitted per kilogram of hydrogen produced (greenhouse gases are converted to their equivalent in carbon dioxide).
Sources
Spectra, “The Colors of Hydrogen: Expanding Ways of Decarbonization” (July 28, 2022), https://spectra.mhi.com/the-colors-of-hydrogen-expanding-ways-of-decarbonization
United Nations Economic Commission for Europe, Technology Brief: Hydrogen (August 2022), https://unece.org/sites/default/files/2022-08/Hydrogen%20brief_EN_final.pdf
Sustainable Energy Fuels, “The many greenhouse gas footprints of green hydrogen” (August 24, 2022), https://pubs.rsc.org/en/content/articlehtml/2022/se/d2se00444e
Solar RRL, “True Cost of Solar Hydrogen” (September 7, 2021), https://onlinelibrary.wiley.com/doi/10.1002/solr.202100487
Early Days of Fuel Cells: Submarines and Space Shuttles
Fuel cells have been around since 1839, when the first one was built by Sir William Grove—just 39 years after the invention of the battery by Alessandro Volta. But it was only in the 1960s, when the National Aeronautics and Space Administration (NASA) developed fuel cells for its space program, that fuel cell research and development really began in earnest.
When NASA first studied the feasibility of manned missions, it looked for a reliable way to provide its astronauts with electricity. At the time, batteries were too short-lived, nuclear energy was deemed too dangerous, and solar panels were too cumbersome. So, NASA picked fuel cells to power the space shuttle.
Fuel cells also had early military applications. They have been used by the German navy to quietly power its submarines underwater since the 1970s.
Fuel cells are battery-like devices that run the electrolysis process in reverse. Instead of using electricity to separate water into its two constituent elements, hydrogen and oxygen are reacted together, by way of a catalyst, to produce water, electricity, and heat. The reaction inside a fuel cell will continue until its source of hydrogen is depleted.
There are many different types of fuel cells, including polymer electrolyte membrane (PEM), direct methanol, alkaline, phosphoric acid, molten carbonate, and solid oxide fuel cells. There are even microbial fuel cells. They each use a different catalyst and have different strengths and weaknesses, with some better suited for certain applications.
When pure hydrogen is used in a fuel cell, the only byproducts are heat and water. Fuel cells can also be designed to run on other fuels that contain hydrogen, such as natural gas and alcohols like ethanol and methanol. In these cases, the hydrogen needed to power the cell is extracted from the fuel using a reformer or, sometimes, the hydrogen is extracted directly inside the fuel cell. When using fuels other than pure hydrogen, a fuel cell emits some carbon dioxide emissions as well as trace amounts of other pollutants.
In addition to being able to run on several types of fuels, fuel cells can also operate at many different scales, from small devices powering smartphones to megawatt-scale power plants that can power tens of thousands of homes. Compact fuel cell systems can be used to directly power portable consumer devices (such as certain pneumatic tools) or to recharge batteries. Portable fuel cells supply off-the-grid power in remote locations. Mid-sized fuel cells power many cellphone towers. Fuel cells can power vehicles, including scooters, cars, buses, trucks, trains, aircraft, and boats. Fuel cell-powered forklifts, used by companies like BMW, Coca-Cola, FedEx, Walmart, and Whole Foods, have been especially popular. Large, stationary fuel cells can be used as primary or backup power for large facilities that cannot afford any interruption to their power supply, such as hospitals, grocery stores, and data centers. Fuel cell installations can even achieve utility scale; as of mid-2025, the largest fuel cell power plant is located in South Korea and powers 250,000 households in greater Seoul.
Fuel cells have several advantages. In addition to being pollution-free when using pure hydrogen produced with renewable or nuclear energy, they are also very reliable and quiet, with few moving parts (which means they require little maintenance compared to internal combustion engines). Fuel cells are less heavy than similarly-sized batteries. They also have a smaller footprint than comparably-scaled wind or solar systems, and can be sited both outdoors and indoors.
Fuel cells are also very efficient. Fuel cells extract about 60% of their fuel’s energy whereas internal combustion engines recover less than 20% of gasoline’s energy. When the heat a fuel cell generates is harnessed in addition to its electricity, fuel cell efficiencies can reach 85%. In theory, fuel cells could be almost 100% efficient, compared to a theoretical maximum of 58% for gas-powered engines.
Fuel cells can be refueled easily, cleanly, and quickly. Fuel cells cars are topped off in five minutes or less in a process that is very similar to refueling a common gasoline tank. Stationary fuel cells, like those used to power some data centers, can be constantly fueled with natural gas or hydrogen pipelines, refueled by tankers, or supplied with gas tanks. Fuel cells for portable devices are typically refueled by swapping out a cartridge containing methanol, which can power direct methanol fuel cells that release some carbon dioxide.
The three main obstacles to the spread of fuel cells have been price, the cost of producing hydrogen, and the difficulty of storing and transporting hydrogen. The latter two challenges naturally apply to hydrogen use in general.
Cost has been one of the main obstacles to the widespread commercialization of fuel cells. At least two types of fuel cells, including PEM fuel cells that are particularly suitable for vehicles, need platinum, an expensive and rare metal. Other types of fuel cells do not require platinum or other expensive catalysts but have other drawbacks, such as high operating temperatures.
Once extracted, hydrogen is difficult to store. As a gas, it must be heavily compressed and stored in high-pressure tanks. Storing it as a liquid requires keeping it at a temperature of −423.17°F or lower.
Widespread use of hydrogen would require the build-out of a new pipeline network, or retrofitting natural gas pipelines to be more durable (hydrogen tends to weaken the metals used to store and transport it, which causes leaks). But hydrogen providers do not want to invest in creating a widespread network if no one is going to use their hydrogen, and companies do not want to invest in hydrogen use if there is no hydrogen available to use.
Dealing with hydrogen on a wider scale will be a learning curve. A colorless and odorless gas, it is non-toxic and safe to breathe. But it is very flammable. It can ignite more easily than other fuels, and it burns with an invisible flame, which can make accidents more likely. Fortunately, hydrogen dissipates quickly in the air, which helps prevent ignition. It is important to note that hydrogen has been produced, stored, and delivered safely in the United States for more than 95 years. It is routinely piped through 1,600 miles of pipelines without incident, and trucks safely transport millions of gallons of liquid hydrogen every year.
Governments, universities, and companies throughout the world are addressing the challenges facing hydrogen energy and fuel cells to accelerate the transition to a clean energy economy. For example, researchers have figured out how to reduce the need for platinum in fuel cells. Ongoing research and development efforts are seeking to further reduce the amount of platinum needed, or eliminate it entirely.
The 2025 Nobel Prize in chemistry was awarded to researchers who developed metal-organic frameworks to store chemicals. These frameworks could potentially be used to efficiently store hydrogen at room temperature.
Some researchers estimate that converting natural gas pipelines to carry hydrogen would not be an insurmountable cost, and significantly cheaper than building new dedicated pipelines. Researchers are also looking into better, cheaper ways to make hydrogen storage and transportation more leak-proof (or better equipped to detect leaks for rapid mitigation).
In the United States, the bipartisan Infrastructure Investment and Jobs Act of 2021 (P.L 117-58) set aside up to $8 billion for a network of seven Regional Clean Hydrogen Hubs (H2Hubs), which would have brought together hydrogen producers and consumers to accelerate the production and use of hydrogen while limiting the need for new pipelines and other infrastructure. The Trump Administration canceled $2.2 billion in federal funding for two hydrogen hubs in California and the Pacific Northwest, and may decide to cut funding to the five remaining hubs.
The Inflation Reduction Act of 2022 (P.L. 117-58) created a clean hydrogen tax credit (Section 45V) to support U.S. production of low-carbon hydrogen. The One Big Beautiful Bill Act (OBBBA) (P.L. 119-21), passed in 2025, maintained the credit but the deadline to begin construction on 45V-eligible projects was brought forward from December 31, 2032, to December 31, 2027. The tax credit for carbon capture and storage (section 45Q), useful for the production of blue hydrogen, was also modified by OBBBA. Some credit values have actually increased, for example for carbon reuse projects, but complex new restrictions on the involvement of foreign entities may impede certain projects.
Stationary fuel cell systems benefit from a new 30% tax credit (Section 48E) granted by OBBBA. But the availability of credits for the purchase of personal and commercial fuel cell vehicles (Sections 30D and 45W, respectively) came to an abrupt end in September 2025 (they were originally slated to continue through 2032).
Last updated in January 2026.
The U.S. Department of Energy (DOE) has an office dedicated to hydrogen and fuel cells, the aptly named Hydrogen and Fuel Cell Technologies Office.
DOE released a U.S. National Clean Hydrogen Strategy and Roadmap in 2023 to achieve the large-scale production and use of hydrogen in the United States.
EESI published a fact sheet on hydrogen fuel cells.
Other EESI hydrogen resources:
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