This Monday, April 5, 2022, the IPCC, the Intergovernmental Panel on Climate Change, released the third and final part of its sixth report, dedicated to solutions that could help us decarbonize our economies. This means the use of so-called green hydrogen (H2) – hydrogen that is produced by electrolysis from renewable energies.
For example, hydrogen can be used “to store electricity as part of the massive expansion of fluctuating renewable energies” or “for electricity trading between different regions to overcome seasonal differences or production capacities”. Hydrogen could also be “used in place of natural gas for peak generation, provide process heat for industrial needs, or be used as a feedstock for the manufacture of various chemicals and synthetic hydrocarbons.” Finally, of course, “hydrogen-based fuel cells could power the heavy transport sector (trucks, buses, ships and trains)”.
But a study released by the UK’s Department for Business, Energy and Industry Strategy (BEIS) may question that idea. According to scientists from the Universities of Cambridge and Reading and the National Center for Atmospheric Science (NCAS), any hydrogen leak will affect atmospheric composition – affecting air quality – and have an indirect warming effect on the climate, partially offsetting the expected benefits of reduced carbon dioxide (CO2) emissions.
People are upset about CH₄ leaks and its global warming potential (GWP). Wait till they get here about H₂…
“We estimate the GWP100 of H₂ to be 11±5… GWP20 for H₂ of 33 [20 to 44]
Ok half as much as CH₄ but H₂ leaks will be the next debate… https://t.co/vBxCTvu7UN
— Glen Peters (@Peters_Glen) April 12, 2022
Hydrogen and its indirect effect on global warming
The researchers first point out that increasing the concentration of hydrogen in our atmosphere – particularly in the troposphere, the layer near the ground – reduces the availability of hydroxyl radicals (OH). Those involved in the decomposition of methane (CH4), a potent greenhouse gas. According to this work, the lifetime of CH4 in our atmosphere would increase by one year for every increase in concentration of 1 part per million (ppm) of hydrogen. Finally, even if we manage to reduce our methane emissions, its concentration in our atmosphere could therefore continue to increase – in the event that H2 leaks go completely unchecked.
Another greenhouse gas the researchers anticipated might be affected by the presence of hydrogen in the atmosphere: tropospheric ozone (O3). Sometimes referred to as “bad ozone”. Because it is both polluting and warming. But they point out here that the benefits associated with reduced emissions of methane, carbon monoxide (CO), volatile organic compounds (VOC), or nitrogen oxides (NOx) that result from adopting a hydrogen economy should balance things out . A slight increase in concentration on the one hand, versus a tendency towards a decrease in concentration on the other. However, the extent of the reduction in these emissions, depending on the technologies actually replaced by hydrogen, remains uncertain.
Even an increase in the H2 concentration in our atmosphere should not have any significant impact on stratospheric ozone. The one that this time protects us from the dangerous ultraviolet radiation that comes to us from the sun.
On the other hand, more hydrogen in the atmosphere will actually increase the concentration of water vapor (H20) in the stratosphere. It is worth remembering that water vapor is one of the main contributors to the greenhouse effect. For a 1.5 ppm increase in H2 concentration – 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 conclude that the introduction of hydrogen as an energy carrier could certainly reduce CO2 emissions and thus offer significant climate benefits. However, in order to maximize them, both leakages would have to be kept to a strict minimum and emissions of other greenhouse gases, especially methane, would have to be limited.
It has been calculated that an increase in hydrogen concentration – on the order of 1.5 ppm – alone would increase global temperatures by 0.12°C – without taking into account the associated impact of reducing CO2 emissions. If methane emissions do not fall at the same time, the temperature will rise by 0.43 °C. But if the leaks, as well as emissions of methane – and the other greenhouse gases mentioned above – are controlled, the adoption of a hydrogen economy will help reduce temperatures by 0.26C.
Finally, taking all this new data into account and including the indirect effects on greenhouse gases, the researchers show that the global warming potential (GWP) of hydrogen is of the order of 11 over 100 years. Understand that this could be 11 times more damaging to climate than CO2. Even as the researchers recognize that there are large uncertainties about the extent of the hydrogen sink in the ground, they call for making limiting hydrogen leaks a real priority.
Track the leaks
To support this, another study also published by BEIS takes stock of the risks of leakage throughout the chain of hydrogen production, transport, storage and use. She tells us that in electrolysis, almost 10% of the hydrogen is lost through “airing and flushing”. But that “recombining that hydrogen” could reduce losses to less than 1%.
The study also classifies hydrogen transport modes according to the losses they cause. Transporting liquid H2 by tank truck seems to be the worst solution with more than 13% hydrogen loss. And we learn that almost 3% of the hydrogen in fuel cells is still lost. But less than 1% in distribution stations.
Hydrogen leaks into atmosphere could ‘undermine climate benefits of decarbonization’
It is the new holy grail of energy: hydrogen is the subject of all major investment projects for the supply of transport, industry or for storing electricity. Except that this gas, which is supposed to be green when made using renewable energy, isn’t so much. , according to some scientists.
Article by Céline Deluzarche published on 11/13/2021
To power cars and trains, fly airplanes or power industries, green hydrogen – produced from renewable sources – now appears as a solution for decarbonization. Last year, the European Commission presented a major hydrogen plan with the goal of producing 40 GW of green hydrogen by 2050. Germany has bluntly announced that it will become the world number 1 in green hydrogen, while France has earmarked €7 billion to fund the development of this fuel. According to the International Energy Agency (IEA), 17 countries have already published a hydrogen plan and more than 20 are working on it. Overall, hydrogen could account for 10% of energy consumption by 2050, the IEA predicts.
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Hydrogen is a powerful indirect greenhouse gas that is 200 times more potent than carbon dioxide
But have we properly measured all the consequences of this massive production? Hydrogen is a potent, short-lived, indirect greenhouse gas that is 200 times more potent than carbon dioxide when released, kilogram for kilogram, chief scientist Steven Hamburg told EURACTIV., the American NGO Environmental Defense Fund (EDF). The latter, one of the lead authors of the Intergovernmental Panel on Climate Change (IPCC), confirms to Futura that hydrogen leaks “could drastically reduce the climate benefit of switching from fossil fuels if not minimized”.
How hydrogen makes the greenhouse effect worse
The scientist explains that hydrogen interacts with other gases in the atmosphere in different ways. On the one hand, it extends the lifespan of methane by delaying its excretion. In fact, the reaction of methane with the OH radical in the air is the main mechanism for the decomposition of methane (CH4 + OH → CH3 + H2O). However, hydrogen also reacts with this OH radical (H2 + OH → H2O + H). “Suddenly more hydrogen in the air means less OH reacting with methane,” the scientist continues. In addition, this reaction also releases water vapor, which contributes to the increase in the greenhouse effect. Finally, hydrogen also leads to the formation of tropospheric ozone, another very powerful greenhouse gas. “Today it is argued that switching to hydrogen would eliminate the climate impact of fossil fuels, but if we take into account these potential leaks, this is not the case,” he warns.
One tonne of hydrogen consumed = 1 to 6 tonnes of CO2 equivalent released
According to a European Commission document published in 2011, up to 10% of hydrogen could leak during production, transport and storage, which would fivefold current emissions. In fact, due to its low molecular weight and low density, hydrogen has a high leakage propensity. According to Falko Ueckerdt from the Potsdam Institute for Climate Impact Research, when one ton of hydrogen is consumed, between 5 and 30 kilograms of this gas could escape into the atmosphere, which, depending on a 200-fold warming compared to CO2, would correspond to a release of 1 to 6 tons of CO2 equivalent. We are a long way from green hydrogen!
limit leaks
However, other academics interviewed by EURACTIV believe these fears are overblown. Because hydrogen is a highly flammable gas, safety protocols are stricter than for natural gas. Also, the fact that hydrogen is more expensive than natural gas encourages the avoidance of leaks in infrastructure, says Gniewomir Flis, hydrogen expert at German think tank Agora Energiewende. The problem is that the detection thresholds are too high today. It is therefore impossible to know how much hydrogen is actually escaping into the atmosphere, supports Ilisa Ocko, another EDF climatologist. So it’s high time to look into the matter. “Otherwise, a massive switch to hydrogen will have serious consequences for the fight against climate change,” concludes Steven Hamburg.
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