99% of hydrogen production today relies on fossil fuels (natural gas, oil and coal) and is responsible of significant greenhouse gas (GHG) emissions.

The OPECST (Office parlementaire d'évaluation des choix scientifiques et technologiques) is The Parliamentary Office for Scientific and Technological Assessment, which was set up by Act n° 83-609 of July 8, 1983, following a unanimous vote of Parliament, aims, within the terms of the act, "to inform Parliament of scientific and technological options in order, specifically, to make its decisions clear." Regarding this, OPECST "collects information, launches study programmes and carries out assessments."

This organization is presided by Cédric Villani.

Cédric Villani is a French politician and mathematician. He was awarded the Fields Medal in 2010.

This article translates in English and sums up the key findings of the report released in April 2021with the support of public and corporate sources (Air Liquide, Total, McPhy…).

You may find the complete document in French here: https://www.senat.fr/fileadmin/Fichiers/Images/opecst/quatre_pages/OPECST_2021_0032_note_Hydrogene.pdf

H2 needs energy to produce

? Hydrogen is in itself a paradox. The most abundant element in the universe, it is rare in the molecular state on earth : very light (eleven times lighter than air), it escapes easily from the atmosphere. It is found combined with other elements (60% of molecules contain hydrogen), such as oxygen (water=H2O) or carbon (organic matter, methane=CH4...). It is thus necessary, before being able to use it or store it, to spend energy to produce it in order to dissociate it from the elements to which it’s bonded.?

The production methods by conversion of fossil fuels, which are dominant today, have the disadvantage of being accompanied by significant GHG emissions (about 800 million tons of CO2 per year)…

? the [production method most] used - up to 99% - are those using fossil fuels, which are less expensive but particularly emit GHGs. Out of 70 million tons of hydrogen [produced globally], 48% comes from natural gas, 28% from oil and 23% from coal, according to data from the International Energy Agency. ?

?The most widespread technique is steam methane reforming (SMR): natural gas is first desulfurized and then treated with steam at around 900°C under a pressure of 20 to 30 bars, a nickel catalyst transforming the gas into synthesis gas (a mixture of H2, CO, CO2, CH4 and H2O). A final step consists of isolating the hydrogen using pressure swing adsorption (PSA) technology, a kind of molecular sieve.

Another production technique is the partial oxidation of hydrocarbons (Pox for Partial Oxidation), which mainly concerns oil and its derivatives. In this intermediate process between pyrolysis and combustion, the synthesis gas - instead of being produced by a catalyst with water vapor as in the case of SMR - is produced by an exothermic reaction with dioxygen, under increased temperature and pressure constraints (900 to 1,500°C and 20 to 60 bars).

These two production methods lead to the production of so-called "grey" hydrogen.

Coal gasification, previously used by some countries, had been neglected until its massive use, about 15 years ago, by China, which produces half of the world's coal and has become the world's leading producer of hydrogen thanks to this technique. The product of this process is called "black hydrogen".?

The challenge of low-carbon hydrogen production by water electrolysis

? The preferred way to produce low-carbon hydrogen is to use electrical energy to extract - by electrolysis - the hydrogen present in water. This process of extracting hydrogen from the cathode and oxygen from the anode is simple and old (implemented as early as 1800) but its scale-up remains complicated because of its high cost.

In addition to significant investment needs, its operating costs are 80% dependent on the price of electricity, with electrolysers consuming, on average, 55kWh of electricity and 9-liter of water per kg of hydrogen produced.

For hydrogen produced by electrolysis to be low-carbon, it is necessary to use "green" electricity - from renewable energies (ENR) - or "yellow" electricity - from nuclear energy. This method of production is not economically competitive: it costs four times as much as SMR and depends on the price of electricity, the price of the electrolysers and the load factor of the latter.

As the investments are high, the electrolysers must be made profitable by extending the periods of use (minimum threshold of 5,000 h/year and optimum threshold up to 8,000 h/year), which is not possible due to the intermittency of renewable energy sources (2,000 to 4,000 h/year of use). In this respect, only nuclear energy and hydroelectricity have the double advantage of being controllable and decarbonized.?

Is H2 electric vehicle a wise idea?

?In any case, and beyond being the most flammable and lightest gas, capable of escaping from almost anywhere, hydrogen is not a miracle solution: the low efficiency of the global process due to the effect of multiple conversions leading to a degradation of the energy potential must be noted.

For example, for a hydrogen electric vehicle, the efficiency of the hydrogen chain from production to final use is around 22% according to Ademe.

In addition, hydrogen distribution remains extremely delicate and costly: because of the very low density of hydrogen (0.09 kg/m3), even with storage under a pressure of 350 bars, it takes up 13 times more space than gasoline. However, as the Académie des technologies explains, it is the entire hydrogen value chain that needs to be realistically understood. In this respect, decentralized production may be of interest.?

Producing enough green hydrogen is not an option…

? The European objective of installing 6 gigawatts (GW) of electrolysers for the production of one million tons of renewable hydrogen by 2024, then 40 GW for ten million tons by 2030, must be confronted with the number of wind turbines that this represents: respectively at least 15,000 and 150,000 wind turbines (i.e. in terms of surface area of photovoltaic panels, about 800,000 hectares and 8 million hectares).

Covering the current needs of industry worldwide (70 million tons of renewable hydrogen or 420 GW) would lead to the commissioning of more than one million new wind turbines or 56 million hectares of photovoltaic panels.

The alternative path of low-carbon hydrogen from nuclear electricity would represent 400 new 1 GW nuclear reactors, which is a chimerical perspective, especially at a time when several countries, including our own, are reducing the share of nuclear power in their energy mix.

Some countries, including Germany, are aiming to import renewable hydrogen from countries with greater renewable energy capacities.?

?A significant increase in our [in France] low-carbon electricity production capacity could lead to the relaunch of the nuclear industry, but the future of hydrogen will depend on a coherent, realistic and responsible energy policy.

This ambition cannot just be a slogan, otherwise hydrogen, which has long been a technology of the future, will remain so.?