Hydrogen is the smallest and most common element in the universe. Unlike on the sun, Saturn, or Jupiter, this colorless and odorless gas occurs on Earth almost exclusively in bound form: it is found in fossil fuels such as natural gas and petroleum, as well as in over half of all known minerals. And as its name and chemical symbol “H2” suggest, hydrogen on Earth is primarily bound in H2O, i.e., in water.
Source: TÜV Nord Group. www.tuev-nord.de. [Online] [Zitat vom 28.10.2021]
https://www.tuev-nord.de/explore/de/entdeckt/was-ist-wasserstoff-einfach-erklaert/
What are the different types of hydrogen?
Hydrogen is classified into different categories based on how it is produced, which are intended to reflect its environmental impact. A distinction is made between gray, blue, turquoise, and green hydrogen.
Grey hydrogen currently dominates the market. It is obtained from fossil fuels, primarily natural gas and coal. Natural gas is converted into hydrogen and carbon dioxide under heat in a process known as steam reforming. The CO2 escapes unused into the atmosphere, thereby exacerbating the greenhouse effect. Depending on the source and electricity mix, the production of one ton of hydrogen generates around ten tons of CO2 – a considerable amount.
Blue hydrogen is actually gray hydrogen, meaning it is produced from fossil fuels. The key difference is that the CO2 produced is separated, captured, and injected into suitable geological formations deep underground. This means it does not escape into the atmosphere. This process is known as carbon capture and storage, or CCS for short. In terms of carbon footprint, blue hydrogen is considered CO2-neutral. Possible storage sites include former oil or gas reservoirs and saltwater-bearing rock layers.
Turquoise hydrogen is hydrogen produced by the thermal cracking of methane – a process known as methane pyrolysis. Instead of CO2, this process produces solid carbon. This process is CO2-neutral if the high-temperature reactor is powered by renewable energy sources. And, of course, the carbon produced must be permanently bound. One advantage of this process is that carbon is easier to store than CO2 and could be used, for example, in the chemical and electronics industries or in road construction. Compared to the production of green hydrogen by electrolysis, methane pyrolysis is also said to require only one-fifth of the energy. However, the process has only been tested on a laboratory scale so far. With funding from the Federal Ministry of Education and Research, BASF has now built a test plant in Ludwigshafen, which is scheduled to go into operation in the coming months once testing has been completed.
Green hydrogen is produced from water using renewable energies in an electrolysis process. This involves splitting the water molecule into its two elements, oxygen and hydrogen. If only electricity from renewable sources is used, the hydrogen is considered CO2-free – even if the production of a wind turbine, for example, is not completely climate-neutral.
Source: Verena Schneider. www.tuev-nord.de. [Online] [Zitat vom 28.10.2021]
https://www.tuev-nord.de/explore/de/erklaert/welche-farbe-hat-wasserstoff/