Hydrogen: harmful effects on the atmosphere in the event of massive use, warn scientists

This Monday, April 5, 2022, the IPCCthe Intergovernmental Group of Experts on the Evolution of the climate published the third and final part of its sixth report devoted to solutions that could help us decarbonize our economies. Among them, the use ofhydrogen (H₂) says green – understand, a hydrogen produced by electrolysis from’renewable energies.

Thus, hydrogen could serve “to the storage of electricity within the framework of the massive deployment of renewable energies intermittent » or even “to trade in electricity between different regions to overcome seasonal or generation capacity differences”. Hydrogen could also “be used in place of the natural gas for peak production, supplying heat process for industrial needs or be used as matter first in the production of various chemicals and hydrocarbons synthetics ». Finally, of course, ” the fuel cells hydrogen fuels could power the heavy transport sector (trucks, buses, ships and trains)”.

But a study published by the UK Department for Business, Energy and Industrial Strategy (BEIS) might question the idea. According to scientists from the universities of Cambridge and Reading and the National center for atmospheric science (NCAS), any hydrogen leak will affect the atmospheric composition – with implications for the quality of theair – and will have an indirect warming effect on the climate, partially offsetting some of the expected benefits of reduced emissions of carbon dioxide (CO₂).

Hydrogen and its indirect effect on global warming

What the researchers point out is first of all that an increase in the concentration of hydrogen in our atmosphere – more particularly in the troposphere, the layer closest to the ground – will decrease the availability of hydroxyl radicals (OH). The very ones that participate in the decomposition of methane (CH₄), a powerful greenhouse gas. According to these works, the duration of life of the CH₄ in our atmosphere would increase by one year for each increase in concentration of 1 part per million (ppm) of hydrogen. And finally, even if we managed to reduce our methane emissionsits concentration in our atmosphere could thus continue to increase – in the event that the leaks of H₂ would be completely uncontrolled.

Other gas greenhouse effect that the researchers potentially expected to be impacted by the presence of hydrogen in the atmosphere: theozone (O₃) tropospheric. sometimes referred to as “bad ozone”. Because it is both polluting and warming. But they point out here that the benefits associated with reducing emissions of methane, carbon monoxide (CO), volatile organic compounds (VOC) or oxides ofnitrogen (NOx) resulting from the adoption of a hydrogen economy should balance things out. A slight increase in the concentration on the one hand, against a tendency to decrease the concentrations on the other hand. However, there remains uncertainty as to the extent of the reduction in these emissions depending on the technologies actually replaced by hydrogen.

An increase in the concentration of H₂ in our atmosphere is also not expected to have a significant effect on stratospheric ozone. The one who, this time, protects us from radiation ultraviolet dangerous that happen to us from Sun.

On the other hand, more hydrogen in the atmosphere will cause the concentration of water vapour (H₂0) in the stratosphere. Water vapor which, it should be remembered, is one of the main contributors to the greenhouse effect. If the concentration of H₂ were to increase by 1.5 ppm – the high leak scenario – the water vapor concentration could increase by more than 1 ppm.

The effects of hydrogen on temperatures

In conclusion, the researchers note that the adoption of hydrogen as an energy carrier could certainly reduce CO2 emissions.₂ and thus provide significant climate benefits. But that, to maximize them, it would be necessary both to reduce leaks to a strict minimum and to limit emissions from other greenhouse gas such as methane in particular.

According to the calculations, an increase in the hydrogen concentration – of the order of 1.5 ppm – “taken alone” would raise global temperatures by 0.12°C – without taking into account the effects of reducing CO2 emissions₂ associated. If in parallel, methane emissions do not decrease, the temperature will increase by 0.43°C. But if the leaks are controlled as well as the emissions of methane – and the other greenhouse gases mentioned above – the adoption of a hydrogen economy will help to lower temperatures by 0.26°C.

Taking into account all these new data and including the indirect effects on greenhouse gases, the researchers finally show that the global warming potential (GWP) of hydrogen over 100 years is of the order of 11. Understand that could be 11 times more harmful to the climate than CO₂. Even if the researchers recognize that major uncertainties remain as to the extent of the hydrogen sink in the ground, they call for making the limitation of hydrogen leaks a real priority.

Track the leaks

To help with this, a another study also published by BEIS takes stock of the risks of leaks throughout the chain of production, transport, storage and use of hydrogen. She tells us that during electrolysis, nearly 10% of the hydrogen is lost by ” ventilation and purge”. But what a ” recombination of this hydrogen” could reduce losses to less than 1%.

The study also classifies hydrogen transport modes according to the losses they cause. Transport by tank truck of H₂ liquid appears to be the worst solution with more than 13% of hydrogen lost. And we learn that nearly 3% of hydrogen is still lost in fuel cells. But less than 1% in distribution stations.

Hydrogen leaks into the atmosphere could ‘undermine the climate benefits of decarbonisation’

It is the new Holy Grail of energy: hydrogen is the subject of all the major investment plans to supply transport, industry or even to store electricity. Except that this gas, supposed to be green when produced with renewable energies, is not so much. , according to some scientists.

Article of Celine Deluzarche published on 13/11/2021

To roll the cars and the trainssteal planes or power industries, green hydrogen – produced from renewable sources – appears today as the solution to decarbonization. Last year, the European Commission presented a large “hydrogen plan”with the aim of producing 40 GW of “green” hydrogen by 2050. Germany has outright announced that it wants to become the world number in green hydrogen, while France has planned seven billion euros to finance the development of this fuel. According to the International Energy Agency (IEA), 17 states have already published a hydrogen plan and more than 20 are working on it. In total, hydrogen could represent 10% of the energy consumption by 2050, predicts the IEA.

But have we properly measured all the consequences of this massive production? ” Hydrogen is a potent short-lived indirect greenhouse gas 200 times more potent than carbon dioxide when released, kilogram for kilogram “, explains to Euroactiv Steven Hamburg, chief scientist of the American NGO Environmental Defense Fund (EDF). The latter, one of the main authors of the Intergovernmental Panel on Climate Change (IPCC), confirms to Futura that hydrogen leaks could ” significantly reduce the climate benefit of moving away from fossil fuels if not minimized “.

How hydrogen worsens the greenhouse effect

Hydrogen interacts with other gases in the atmosphere in several ways, explains the scientist. On the one hand, it prolongs the life of methane by delaying its elimination. Indeed, the reaction of methane with the OH radical of the air is the primary mechanism of methane decomposition (CH4 + OH → CH3 + H2O). However, hydrogen also reacts with this OH radical (H2 + OH → H2O + H). ” So more hydrogen in the air means less OH to react with methane “, continues the scientist. In addition, this reaction also releases water vapor, which contributes to the increase of the greenhouse effect. Finally, hydrogen also leads to the formation tropospheric ozone, another very potent greenhouse gas. ” Today, it is argued that switching to hydrogen would eliminate the climate impact of fossil fuelsbut when you factor in those potential leaks, that’s not the case. “, he warns.

One tonne of hydrogen consumed = 1 to 6 tonnes of CO equivalent₂ released

According to a European Commission document published in 2011, up to 10% of hydrogen could “leak” during production, transport and storage, which would multiply current emissions by five. Hydrogen has indeed a high propensity to leak due to its low mass molecular weight and its low density. According to Falko Ueckerdt of the Potsdam Institute for Climate Impact Research, consuming one tonne of hydrogen could release between 5 and 30 kilograms of this gas into the atmosphere, which depending on the warming 200 times higher than that of CO₂ would amount to releasing 1 to 6 tonnes of CO equivalent₂. We are far from green hydrogen!

Limit leaks

Other scientists interviewed by Euroactiv however, believe that these fears are exaggerated. Since hydrogen is a highly flammable gas, protocols safety are more stringent than for natural gas. Moreover, “ hydrogen being more expensive than natural gas, this encourages the prevention of leaks in infrastructures“, Tempers Gniewomir Flis, expert in hydrogen within the German think tank Agora Energiewende. ” The problem is that the detection thresholds today are too high. It is therefore impossible to know how much hydrogen is actually leaking into the atmosphere.», Supports Ilisa Ocko, another climatologist from EDF. It is therefore high time to look into the matter. ” Otherwise, a massive switch to hydrogen will have serious consequences on the fight against climate changeconcludes Steven Hamburg.