What is hydrogen?

Hydrogen is the simplest and most abundant element in the universe—it is number 1 on the periodic table of elements (this link takes you to Los Alamos National Laboratory's site). 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. See the AFDC Fuel Properties database for more details.

Very little hydrogen gas is present in 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 on the NASA Web site.

Hydrogen also can be used to fuel internal combustion engines and fuel cells, both of which can power low- or zero-emissions vehicles such as fuel cell vehicles. Major research and development efforts are aimed at making hydrogen vehicles practical for widespread use.