Hydrogen from natural gas makes new friends

Dhe climate balance of blue hydrogen is controversial in science. Researchers from the US universities of Cornell and Stanford presented a study in August according to which blue hydrogen used for combustion is around 20 percent worse for the climate than natural gas, and researchers in Switzerland and Scotland are now drawing a rather positive balance. However, it depends on where the natural gas is extracted, say Christian Bauer from the Laboratory for Energy System Analysis at the Paul Scherrer Institute (PSI) in Villigen and Mijndert van der Spek, Professor at the Research Center for Carbon Solutions at the University of Edinburgh.

In Norway, for example, in contrast to many other producing countries, there are hardly any leaks, so that the argument of my colleagues does not work in this case. They had included emissions of methane, the main constituent of natural gas, which are released when used laxly. Methane is around 30 times more harmful to the climate than carbon dioxide. Blue hydrogen is created by steam reforming the natural gas. The two components are mixed in a reactor. The gases carbon dioxide (CO2) and hydrogen are produced, which are separated from each other in a downstream process. The CO2 can be used or stored in former natural gas reservoirs, a well-tried process. Norway, for example, has been disappearing deep into the depths of the CO2 that is produced when cleaning freshly extracted natural gas.

Like their American colleagues, Bauer and van der Spek looked at the entire life cycle of natural gas, from extraction and transport to use. To do this, they used simulation software from the Technical University of Zurich, which records the entire process. The researchers fed the result into a life cycle assessment model developed at PSI. In the case of high leakage rates, the team had to agree with their US colleagues. In other words: natural gas from the USA and Russia is not suitable for the production of blue hydrogen. But if practically no natural gas is lost, the blue hydrogen is almost as climate-friendly as the green, which is produced by splitting water with electricity from emission-free sources, says Bauer.

Proponents of the blue variant argue that climate change cannot be stopped with green hydrogen alone. It is too expensive and there is far too little green electricity available for it. So-called turquoise hydrogen could also help. It is produced by pyrolysis, i.e. heating the natural gas in the absence of air. This creates hydrogen and solid carbon, which can be recycled or disposed of even more safely than CO2. The energy expenditure for the production of the turquoise variant is high, however, and there would only be relief for the climate if the required energy could be made available emission-free.



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