Like electricity, hydrogen is an energy carrier that can be produced from various feedstocks. Although hydrogen is a clean-burning energy source, when burned it only produces electricity and water. These feedstocks and production methods should be considered when evaluating hydrogen emissions.
The greenhouse gas intensity (and other environmental impacts) of hydrogen production depends on the sources and processes through which the hydrogen is derived. It can be extracted from water using electrolysis, using power from renewable solar or wind, nuclear energy, or fossil energy. It can be extracted from renewable biomass or coal using high temperature gasification. It can be derived from renewable biogas, renewable ethanol or methanol, or fossil natural gas. Most hydrogen is derived from fossil natural gas, emitting fossil carbon dioxide as a by-product.
See the section on Natural Gas Environmental Impact for more information.