Hydrogen (H2) is a potentially emissions-free alternative fuel that can be produced from domestic resources. Although not widely used today as a transportation fuel, government and industry research and development are working toward the goal of clean, economical, and safe hydrogen production and hydrogen fuel cell vehicles.
Hydrogen is the simplest and most abundant element in the universe. At Earth-surface temperatures and pressures, it is a colorless, odorless gas (H2). However, hydrogen is rarely found alone in nature. It is usually bonded with other elements. For more information, see fuel properties and the Hydrogen Analysis Resource Center.
Very little hydrogen gas is present in the Earth's atmosphere. Hydrogen is locked up in enormous quantities in water (H2O), hydrocarbons (such as methane, CH4), and other organic matter. Efficiently producing hydrogen from these compounds is one of the challenges of using hydrogen as a fuel.
Currently, steam reforming of methane (natural gas) accounts for about 95% of the hydrogen produced in the United States. Almost all of the approximately 9 million tons of hydrogen produced here each year are used for refining petroleum, treating metals, producing fertilizer, and processing foods. Hydrogen has been used for space flight since the 1950s. Learn more about hydrogen and fuel cells from the National Aeronautics and Space Administration.
Hydrogen also can be used to fuel internal combustion engines and fuel cells, both of which can power zero- to near-zero-emissions vehicles, such as hydrogen fuel cell vehicles. Major research and development efforts are aimed at making hydrogen fuel cell vehicles practical for widespread use. Additionally, hydrogen can be blended with natural gas to create hythane, a transportation fuel for use in natural gas vehicles. This alternative fuel offers significant decreases in nitrogen oxides (NOx) emissions.
Learn more about hydrogen and fuel cells from the Fuel Cell Technologies Program.
Hydrogen as an Alternative Fuel
Hydrogen is considered an alternative fuel under the Energy Policy Act of 1992. The interest in hydrogen as an alternative transportation fuel stems from its clean-burning qualities, its potential for domestic production, and the fuel cell vehicle's potential for high efficiency—it's two to three times more efficient than a gasoline vehicle. Learn more about fuel cells.
The energy in 2.2 pounds (1 kilogram) of hydrogen gas is about the same as the energy in 1 gallon of gasoline. Because hydrogen has a low volumetric energy density, it is important for a fuel cell vehicle to store enough fuel onboard to have a driving range comparable to conventional vehicles. Some hydrogen storage technologies are available and undergoing more research and demonstration. These technologies include compressing gaseous hydrogen in high-pressure tanks at up to 10,000 pounds per square inch and cooling liquid hydrogen cryogenically to -423°F (-253°C) in insulated tanks. Other storage technologies are under development, including bonding hydrogen chemically with a material such as metal hydride. Learn more about hydrogen storage.