EXPERT OPINION Decarbonizing with H2 needs decarbonizing H2 first

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Hydrogen is increasingly promoted as mandatory part of an energy transition towards a zero carbon society. It is supposed to become a fuel for the future, replace natural gas in heating, power vehicles, act as a core component to generate e-fuels to decarbonize aviation and be a seasonal energy storage.

H₂ is an important chemical component used in producing fertilizer and many other products from the chemical industry. The world today has an annual demand of roughly 100 million tons of this element, which is repeatedly cited as being the most abundant substance on Earth - and in space. Most of this hydrogen is generated by steam reforming of natural gas with a catastrophic carbon footprint of 10 kg CO₂ per kg of hydrogen.

However, hydrogen can be generated from electrolysis using renewable energy sources, resulting in a zero-carbon fuel, right?
This statement is technically correct but as always, there is a catch. With hydrogen, "the catch" is that it needs to be generated using electricity and water. To get 1kg of the gas, 10 liters of water need to be split and on industrial scale, an electrolyzer with 10 MW of power can generate 1,400 tons of hydrogen in one year. This is where the trouble starts as a 10 MW electrolysis, operated one year, consumes as much as 80,000 MWh of electricity. Generating 100 million tons of green hydrogen in one year would demand 68,500 electrolysis facilities, 10 MW each, consuming a mind-boggling 4,180 TWh of electricity. To set this into perspective: The electricity consumption of the United States is about 5,480 TWh.

If hydrogen generation is to be decarbonized by 2040, this means setting up 130 MW of electrolysis every day from now on until December 2040. Every day, every Sunday, Christmas, New Year's Eve and Independence Day. In parallel it would demand a tremendous amount of renewable energy to be set up. Generating this much energy would require 137,000 windmills with 10 MW each in addition to 205,500 solar arrays with 10 MW each.

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On top of that, an inherent paradox needs to be solved: If hydrogen is used as energy storage, it would be a bad idea, to use this stored energy to generate hydrogen, right? However, to keep the electrolyzers working almost 24/7, fed by zero-carbon energies, there needs to be energy storage. Windmills off-shore will provide about 4000 full-power-equivalent hours per year and solar arrays work in parallel for about 1000 full-power-equivalent hours. So about 50% of the energy needed per year could be taken from those sources directly, the second half would have to be stored. Stored in batteries because storing in H₂ to generate H₂ is not making sense. Consequently, battery energy storage capacity would need to increase by a staggering amount of 2,740 TWh.

This requires a daily installation of 500GWh of battery capacity from now to December 2040. These mind-blowing numbers reveal that even substituting the fossil hydrogen currently used by green hydrogen represents a global challenge in the true manner of speaking. The benefit would be, that a huge amount of CO₂ - 1000 million tons - would not be generated.

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However, hydrogen today plays no role as fuel or replacement for natural gas and if it should, it would demand another 100 million tons of it. Moreover, decarbonizing the global steel production would require further 100 million tons of the stuff. So how serious can hydrogen, often nicknamed "hopium" for obvious reasons, could become an energy carrier for the future zero-carbon society?

Wherever fossil hydrogen is used today, it should be replaced by green hydrogen with the correlating CO₂ reduction. That's challenging enough for the 20 years ahead of us, most likely for far more than this. Wherever there are better solutions than hydrogen, hydrogen should not be considered. Heating with heat pumps instead of hydrogen, powering vehicles with batteries instead of hydrogen, or use inductive heating in metal melting and treatment instead of burning hydrogen.

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