end use. In the presence of a catalyst, hydrogen, carbon monoxide and carbon dioxide are produced. The resulting carbon monoxide is reacted at high-temperatures with steam to produce more carbon dioxide and hydrogen in a "water-gas shift reaction". Then the hydrogen is separated and purified. Another method is using starch-rich feedstocks to ferment to produce hydrogen. This is known as dark fermentation and uses anaerobic bacteria primarily to ferment mainly carbohydrates into hydrogen. Other processes are photoheterotrophic processes. In this process, a prokaryotic microorganism called pure non-sulfur bacteria (PNS) or green algae reacts with light to produce hydrogen, via a pathway of photosynthesis. Unlike dark fermentation, these processes use enzymes like hydrogenase and nitrogenase for generation of molecular hydrogen. Currently, the breakdown of hydrogen gas production is mainly coming from fossil fuels. In fact, 96% of hydrogen is produced directly from fossil fuels, the majority of which coming from natural gas (48%). Only 4% of hydrogen is produced indirectly from fossil fuels by electrolysis with no breakdown in green hydrogen. Green hydrogen is any hydrogen that is produced from renewable energy. This includes electrolysis with electricity coming from green sources such as solar, wind, and hydroelectric power. Blue hydrogen is hydrogen that is produced from natural gas in advanced processes which emit greenhouse gas emissions. Grey hydrogen is produced from steam methane reforming, or steam reforming, which has a higher greenhouse gas emission total than blue hydrogen. Finally, brown hydrogen is produced from coal in Coal Classification which has one of the highest greenhouse gas emissions per ton of hydrogen produced. Thermochemical water splitting ins the newest source of green hydrogen production beyond hydrolysis. Using chlorine and sulfur, in the presence of a nuclear reactor, sunlight can be focused above a solar thermochemical hydrogen (STCH) reactor to produce hydrogen. Once produced, hydrogen can be used in much the same way as natural gas – it can be delivered to fuel cells to generate electricity and heat, used in a combined cycle gas turbine to produce larger quantities of centrally produced electricity or burned to run a combustion engine; all methods producing no carbon or methane emissions. In each case hydrogen is combined with oxygen to form water. This is also one of its most important advantages as hydrogen fuel is environmentally friendly. The heat in a hydrogen flame is a radiant emission from the newly formed water molecules. The water