What makes hydrogen an energy tool?
The most common element in the universe, hydrogen has the highest energy content per unit weight of any known fuel. It never occurs by itself in nature - it always combines with other elements such as oxygen (for water) and carbon (for fossil fuels). Once separated, hydrogen is the ultimate clean energy carrier. NASA’s space shuttles use hydrogen-powered fuel cells to operate electrical systems and the key emission, water, is consumed by the crew.
How is hydrogen produced?
It can be extracted from any substance with hydrogen: water, fossil fuels and even some organic matter. Almost all of the hydrogen used worldwide today comes from natural gas though a process called reforming. Natural gas is made to react with steam, producing hydrogen and carbon dioxide.
The hydrogen is then used to make ammonia for fertilizer, in refineries to make reformulated petrol, and in the chemical, food and metals industries. Hydrogen can also be made from coal in a similar process. Either way, the process releases carbon dioxide, a gas tied to global warming.
Carbon-free methods involve splitting water into its component parts of hydrogen and oxygen through electrolysis but the electric current itself has to be produced. The holy grail of hydrogen is to use a renewable source like solar, wind, hydro, geothermal or biomass power to create the current, making the process pollution free and sustainable. Future possibilities include using the power of ocean waves to generate electricity and microorganisms that could be adapted to produce hydrogen, as well as recovering hydrogen from fermentation or gasification of biomass.
Source: National Renewable Energy Laboratory, U.S. Department of Energy