Currently, the demand for hydrogen is mainly covered by steam reforming. In this process, fossil fuels such as natural gas or crude oil and steam react to form synthesis gas, a mixture of hydrogen and carbon monoxide. The incompletely converted intermediate product carbon monoxide is further converted to hydrogen with water vapor in the downstream so-called water-gas shift reaction. The greenhouse gas carbon dioxide is produced as a by-product in both steps. The product obtained in this way is also referred to as gray hydrogen, as carbon dioxide emissions are generated in the process, even if no CO₂ quantities are produced during subsequent use. The often not insignificant upstream chain emissions from the transportation and extraction of natural gas should also not be neglected.
Production of Hydrogen and Colors
From gray to green: How the production of hydrogen works.
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Not only the possibilities of using hydrogen in the various sectors for decarbonization are important for achieving climate neutrality - the way hydrogen is produced is also of enormous importance.
The different color designations of hydrogen are intended to provide information about its climate friendliness and thus usually also describe the way in which it is produced. In order to achieve the Paris climate targets, only green hydrogen may be used in the future. This is usually produced using electrolysis, which is powered by electricity from renewable sources such as wind and solar energy. This is the only way to achieve the necessary reduction in emissions.
Gray Hydrogen
Blue Hydrogen
Blue hydrogen (like gray hydrogen) is usually produced from natural gas. However, the resulting CO₂ is captured and stored underground (carbon capture and storage: CCS). In this way, no CO₂ emissions are released into the atmosphere during the production process. If the energy required for steam reforming and the additional demand for CO₂ capture is covered by renewable sources, blue hydrogen is therefore significantly more climate-friendly than gray hydrogen. However, the blue hydrogen process chain still generates considerable greenhouse gas emissions - particularly through the extraction and provision of natural gas. Nevertheless, it is assumed that blue hydrogen will play an important role as a bridging technology until sufficient quantities of green hydrogen are available.
Turquoise Hydrogen
This "color" of hydrogen is a recurring topic of discussion among experts: so-called turquoise hydrogen is produced through the pyrolysis (simplified: heating in the absence of oxygen) of methane. This produces solid carbon instead of gaseous carbon dioxide, which can be stored relatively easily compared to CO₂ (as with blue hydrogen using CCS). However, this technology cannot yet be implemented on a large, industrial scale. Although the production method avoids the difficulties associated with CCS processes (low acceptance, risks of long-term storage, additional energy requirements, etc.), the problem of upstream emissions of highly climate-damaging greenhouse gases, which are already produced during the extraction of the natural gas, remains. Added to this is the technically challenging handling of the solid carbon produced in ultra-fine form.
Green Hydrogen
Green hydrogen is produced by electrolyzing water using renewable electricity. The electricity separates the chemical compounds and breaks the water down into its components oxygen and hydrogen. The current flows between two electrodes. Oxygen is produced at the positively charged electrode (anode) and hydrogen at the negatively charged electrode (cathode). To prevent the two products from mixing, the two electrode chambers are separated by a membrane that is permeable to charge carriers.
Alkaline electrolysis is a process that has been established on an industrial scale for decades. Alternative electrolysis techniques, such as PEM electrolysis or high-temperature electrolysis (SOEL), should also be mentioned. PEM electrolysis has already been successfully scaled up for use on an industrial scale (REFHYNE project at Shell Energy and Chemicals Park or TrailBlazer from AirLiquide in Duisburg). Intensive research is still being carried out on SOEL technology for applicability on this scale.
Site selection for H2 production depends on renewable energy sources
The origin of the electricity is crucial for greenhouse gas-neutral production through electrolysis. The enormous demand for electricity from renewable sources will determine the choice of location for electrolysers in the future. It can therefore be assumed that the majority of green hydrogen will be produced in the vicinity of renewable electricity generation. For example, regions in northern Germany and other European countries with good conditions for generating electricity from renewable energies (in particular the countries bordering the North Sea such as the UK and Denmark or southern European countries such as Spain or Portugal) are relevant here. In the future, it can be assumed that a global market for green hydrogen will grow and that hydrogen, particularly in the form of derivatives such as ammonia, will also be imported to Germany from regions further afield (e.g. from the MENA region, Chile, Brazil or Australia) with very favorable production conditions.
Plant engineering offers economic opportunities for NRW
Although NRW does not have outstanding production conditions for green hydrogen in a European and global comparison, North Rhine-Westphalia has a strong and innovative plant construction sector in addition to the large industrial hydrogen demand, which will be decisive for the ramp-up of the hydrogen economy. For the state, this will result in economic opportunities, sustainable jobs and the prospect of added value. From electrolysers that produce hydrogen from water using renewable energies, to fuel cells and hydrogen burners that make it usable, to essential components such as hydrogen-compatible pressure tanks, compressors, gas turbines and pipelines: new markets and export opportunities are developing here for the economy in NRW.