Hydrogen (H2) is the most abundant element and cleanest fuel in the universe. Unlike hydrocarbon fuels, such as oil, coal and natural gas, where carbon dioxide and other contaminants are released into the atmosphere when used, hydrogen fuel usage produces only pure water (H2O) as the byproduct. Unfortunately, pure hydrogen does not exist naturally on Earth and therefore must be manufactured. Historically, the cost of manufacturing renewable hydrogen as an alternative fuel has been higher than the cost of the energy used to make it.