In many cases, the conversion of industry to hydrogen is apparently less sustainable than previously assumed. This is the conclusion of a study by the Forschungsstelle für Energiewirtschaft (FfE) commissioned by the nature conservation organization Nabu and reported by the “Redaktionsnetzwerk Deutschland”.
In it, the potentials of a hydrogen economy were examined with regard to its climate balance and environmental protection. “Hydrogen is necessary to achieve climate targets and deep decarbonization,” the study states, but at the same time the authors also write that hydrogen is not low in emissions per se, since sustainability depends strongly on the origin and the production route. H2 (gray hydrogen) produced from fossil natural gas, for example, has a particularly poor carbon footprint. Even if the carbon generated during production is split off and injected into the ground using CCS technology (blue hydrogen), the balance is hardly any better.
The reason is leakage during extraction and processing of the natural gas, which allows methane to escape into the atmosphere, where it is significantly more harmful to the climate than CO2. “In a 100-year global warming potential scenario, the greenhouse gas emissions of blue hydrogen are even worse than those of direct combustion of natural gas,” Nabu writes.
Once the energy carrier is produced from water using electrolysis, sustainability depends on the origin of the electrical power used. If the current electricity mix is used (yellow hydrogen), the balance is also poor, according to Nabu. “With the current electricity mix, the climate impact of hydrogen from electrolysis is higher than that of gray hydrogen, which is why NABU rejects the use of yellow hydrogen,” it says.
But even with green hydrogen from green electricity, there are problems. “Green hydrogen requires green electricity and raw materials, especially metals from the platinum group for the electrolyzers,” Nabu writes: In addition, the climate balance has so far only taken into account the hydrogen-induced changes in methane and ozone in the troposphere, the lowest layer of the atmosphere.
In the meantime, however, there are findings that about one-third of the greenhouse gas potential results from changes in stratospheric water vapor, he said. “This means that hydrogen has a much higher greenhouse potential than previously assumed,” the environmentalists said. As a consequence, Nabu calls for a “complete life cycle assessment” of green hydrogen and for the energy carrier to be used only for processes that cannot be electrified, such as the production of primary steel. “Hydrogen is also a very small molecule and highly volatile.
Leakage risks throughout the transport chain must be fully assessed and minimized,” said NABU President Jörg-Andreas Krüger. NABU rejects the use of hydrogen from fossil sources, including with CCS, and the classification as CO2-neutral, and considers it justifiable at best as a temporary interim solution. “However, a temporary interim solution with the use of blue hydrogen is only acceptable if the transition path is designed and accompanied by a transdisciplinary process involving science, politics, business and organized civil society,” says Krüger.