color codes is not standardized, neither is it completely arbitrary. Methods of production Molecular hydrogen was discovered in the Kola Superdeep Borehole. It is unclear how much molecular hydrogen is available in natural reservoirs, but at least one company specializes in drilling wells to extract hydrogen. Most hydrogen in the lithosphere is bonded to oxygen in water. Manufacturing elemental hydrogen requires the consumption of a hydrogen carrier such as a fossil fuel or water. The former carrier consumes the fossil resource and in the steam methane reforming (SMR) process produces greenhouse gas carbon dioxide. However, in the newer methane pyrolysis process no greenhouse gas carbon dioxide is produced. These processes typically require no further energy input beyond the fossil fuel. Decomposing water, the latter carrier, requires electrical or heat input, generated from some primary energy source (fossil fuel, nuclear power or a renewable energy). Hydrogen produced by zero emission energy sources such as electrolysis of water using wind power, solar power, nuclear power, hydro power, wave power or tidal power is referred to as green hydrogen. When derived from natural gas by zero greenhouse emission methane pyrolysis, it is referred to as turquoise hydrogen. When fossil fuel derived with greenhouse gas emissions, is generally referred to as grey hydrogen. If most of the carbon dioxide emission is captured, it is referred to as blue hydrogen. Hydrogen produced from coal may be referred to as brown hydrogen. Current production methods Steam reforming – gray or blue Hydrogen is industrially produced from steam reforming (SMR), which uses natural gas. The energy content of the produced hydrogen is less than the energy content of the original fuel, some of it being lost as excess heat during production. Steam reforming emits carbon dioxide, a greenhouse gas, unless it is captured and stored. Methane pyrolysis – turquoise Pyrolysis of methane (natural gas) with a one-step process bubbling methane through a molten metal catalyst is a "no greenhouse gas" approach to produce hydrogen that was perfected in 2017 and now being tested at scale. The process is conducted at high temperatures (1065 °C). Producing 1 kg of hydrogen requires about 5 kWh of electricity for process heat. The pyrolysis of methane can be expressed by the following reaction equation. (g) → C(s) + 2 (g) ΔH° = 74.8 kJ/mol The industrial quality solid carbon may be sold as manufacturing feedstock or landfilled (no pollution). Electrolysis of