Switching to Hydrogen Fuel Could Cause Long-Term Climate Consequences

Methane Hydrogen Figure

The hydrogen economy could increase levels of atmospheric methane. Credit: Bumper DeJesus

Research conducted by Princeton University and the National Oceanic and Atmospheric Association suggests that a chemical reaction in the lower atmosphere could restrict the potential of hydrogen as a clean fuel.

The reason for this is that hydrogen gas reacts readily in the atmosphere with the same molecule responsible for breaking down methane, which is a potent greenhouse gas. If the level of hydrogen emissions surpasses a specific threshold, this shared reaction is likely to result in an accumulation of methane in the atmosphere, leading to long-term climate consequences.

“Hydrogen is theoretically the fuel of the future,” said Matteo Bertagni, a postdoctoral researcher at the High Meadows Environmental Institute working on the Carbon Mitigation Initiative. “In practice, though, it poses many environmental and technological concerns that still need to be addressed.”

Bertagni is the first author of a research article published in Nature Communications, in which researchers modeled the effect of hydrogen emissions on atmospheric methane. They found that above a certain threshold, even when replacing fossil fuel usage, a leaky hydrogen economy could cause near-term environmental harm by increasing the amount of methane in the atmosphere. The risk for harm is compounded for hydrogen production methods using methane as an input, highlighting the critical need to manage and minimize emissions from hydrogen production.

“We have a lot to learn about the consequences of using hydrogen, so the switch to hydrogen, a seemingly clean fuel, doesn’t create new environmental challenges,” said Amilcare Porporato, Thomas J. Wu ’94 Professor of Civil and Environmental Engineering and the High Meadows Environmental Institute. Porporato is a principal investigator and member of the Leadership Team for the Carbon Mitigation Initiative and is also associated faculty at the Andlinger Center for Energy and the Environment.

The problem boils down to one small, difficult-to-measure molecule known as the hydroxyl radical (OH). Often dubbed “the detergent of the troposphere,” OH plays a critical role in eliminating greenhouse gases such as methane and ozone from the atmosphere.

The hydroxyl radical also reacts with hydrogen gas in the atmosphere. And since a limited amount of OH is generated each day, any spike in hydrogen emissions means that more OH would be used to break down hydrogen, leaving less OH available to break down methane. As a consequence, methane would stay longer in the atmosphere, extending its warming impacts.

According to Bertagni, the effects of a hydrogen spike that might occur as government incentives for hydrogen production expand could have decades-long climate consequences for the planet.

“If you emit some hydrogen into the atmosphere now, it will lead to a progressive build-up of methane in the following years,” Bertagni said. “Even though hydrogen only has a lifespan of around two years in the atmosphere, you’ll still have the methane feedback from that hydrogen in 30 years from now.”

In the study, the researchers identified the tipping point at which hydrogen emissions would lead to an increase in atmospheric methane and thereby undermine some of the near-term benefits of hydrogen as a clean fuel. By identifying that threshold, the researchers established targets for managing hydrogen emissions.

“It’s imperative that we are proactive in establishing thresholds for hydrogen emissions so that they can be used to inform the design and implementation of future hydrogen infrastructure,” said Porporato.

For hydrogen referred to as green hydrogen, which is produced by splitting water into hydrogen and oxygen using electricity from renewable sources, Bertagni said that the critical threshold for hydrogen emissions sits at around 9%. That means that if more than 9% of the green hydrogen produced leaks into the atmosphere — whether that be at the point of production, sometime during transport, or anywhere else along the value chain — atmospheric methane would increase over the next few decades, canceling out some of the climate benefits of switching away from fossil fuels.

And for blue hydrogen, which refers to hydrogen produced via methane reforming with subsequent carbon capture and storage, the threshold for emissions is even lower. Because methane itself is the primary input for the process of methane reforming, blue hydrogen producers have to consider direct methane leakage in addition to hydrogen leakage. For example, the researchers found that even with a methane leakage rate as low as 0.5%, hydrogen leakages would have to be kept under around 4.5% to avoid increasing atmospheric methane concentrations.

“Managing leakage rates of hydrogen and methane will be critical,” Bertagni said. “If you have just a small amount of methane leakage and a bit of hydrogen leakage, then the blue hydrogen that you produce really might not be much better than using fossil fuels, at least for the next 20 to 30 years.”

The researchers emphasized the importance of the time scale over which the effect of hydrogen on atmospheric methane is considered. Bertagni said that in the long-term (over the course of a century, for instance), the switch to a hydrogen economy would still likely deliver net benefits to the climate, even if methane and hydrogen leakage levels are high enough to cause near-term warming. Eventually, he said, atmospheric gas concentrations would reach a new equilibrium, and the switch to a hydrogen economy would demonstrate its climate benefits. But before that happens, the potential near-term consequences of hydrogen emissions might lead to irreparable environmental and socioeconomic damage.

Thus, if institutions hope to meet mid-century climate goals, Bertagni cautioned that hydrogen and methane leakage to the atmosphere must be held in check as hydrogen infrastructure begins to roll out. And because hydrogen is a small molecule that is notoriously difficult to control and measure, he explained that managing emissions will likely require researchers to develop better methods for tracking hydrogen losses across the value chain.

“If companies and governments are serious about investing money to develop hydrogen as a resource, they have to make sure they are doing it correctly and efficiently,” Bertagni said. “Ultimately, the hydrogen economy has to be built in a way that won’t counteract the efforts in other sectors to mitigate carbon emissions.”

Reference: “Risk of the hydrogen economy for atmospheric methane” by Matteo B. Bertagni, Stephen W. Pacala, Fabien Paulot, and Amilcare Porporato, 13 December 2022, Nature Communications.
DOI: 10.1038/s41467-022-35419-7

The study was funded by the National Science Foundation and the Gordon and Betty Moore Foundation

15 Comments on "Switching to Hydrogen Fuel Could Cause Long-Term Climate Consequences"

  1. Hottan Bothred | April 2, 2023 at 10:18 am | Reply

    Stop that, it’s silly. Stopping hydrogen leaking is already very incentivized, as you’re losing fuel. H2 is in fossil fuel exhaust anyway, even in farts. Hydrogen gas has an equilibrium point in the atmosphere; it either reacts or burns or escapes the atmosphere. Some bacteria even consume it for energy. You won’t lose much, you’re already doing it anyway, and it can’t matter.

    What’s more of a threat is mass-producing hydrogen. So far, it’s a 60% of its energy to make electricity, then losing >20% of the energy electrolysing water. It’s lossy, similar to charging batteries, except now you have a physical explosive thing to move around that won’t travel across wires, so add distribution/delivery losses, not to mention losing the things that explode. It’s better than stupid batteries, yet there’s reasons to not like it, but H2 emissions isn’t a good one.

    • Hottan Bothred | April 2, 2023 at 10:25 am | Reply

      Less-than signs here are stripped as potentially HTML, which removed half that sentence. I’ll rephrase- “So far, you’re most-likely burning coal, losing over 60% of its energy to make electricity, then losing over 20% of that energy electrolyzing water.”

      • Hydrogen being such a small molecule is difficult to contain but I agree I doubt this is a massive concern. However hydrogen to power cars is nowhere near as efficient as using batteries. Your example burning coal is only 40% efficient is about right. If you burn coal to produce hydrogen the whole enterprise is worthless.
        20% loss to create electricity by electrolysis is a low estimate but some improvements are in the pipeline so may be realistic. Car batteries with double the existing range are already going into mass production so battery vehicles are likely to improve massively.
        Once you you have the electricity you lose 20% converting to hydrogen, converting it back via a fuel cell means you lose about half of the remainder so you are din to 40% of the energy where a battery car only loses about 5%. Car makers are also looking at using hydrogen in a combustion engine and those are likely to be significantly less efficient than a fuel cell.

  2. Alexander cokonis | April 2, 2023 at 11:11 am | Reply

    This is another attempt to vilify the most important fuel in the universe. The article is based on theoretical assumptions on studies made under laboratory conditions. Free atmospheric hydrogen ends up in outer space within 1/2 hour. There is not enough time for reactions to occur on lower levels of the atmosphere where heavy hydrocarbon gases reside.

    • Clyde Spencer | April 2, 2023 at 8:17 pm | Reply

      “Free atmospheric hydrogen ends up in outer space within 1/2 hour.”

      Assuming that the top of the exosphere is about 250 miles from the surface, a molecule of H2 would have to travel at a speed of 500 miles per hour, in a straight line, to make it from the surface to “outer space” in the half-hour you claim. I find that to be unlikely. Individual molecules will have a random-walk path, aka Brownian Motion. Thus, it will take MUCH longer than 1/2 hour. While the speed of H2 along any leg of its random-walk may well be high, what we are talking about here is the rate of diffusion upwards. A few minutes searching online didn’t provide a definitive answer. It isn’t a simple problem because both buoyancy and partial pressure appear to play a role. However, I think that you need to provide a reliable citation for your claim.

  3. I knew hydrogen wouldnt work and this is just one more reason why

  4. Clyde Spencer | April 2, 2023 at 8:24 pm | Reply

    “We have a lot to learn about the consequences of using hydrogen, so the switch to hydrogen, a seemingly clean fuel, doesn’t create new environmental challenges,”

    Not the least of the concerns is what to do with the water resulting from combustion. If it is used for transportation, and held on board, it will decrease the mileage from the increasing mass. If it is condensed and released onto the pavement, it will make the roads slick, leading to more accidents, especially in Winter. If it is released to the air, it will increase the relative humidity, leading to a higher heat index in Summer, and encouraging the growth of mold. There are other problems as well.

  5. I thought we already past the point to use “pure” hydrogen as a fuel?
    I thought now people start to utilize alternative like ethanol, methanol, urea, and so on? As they has more energy density, easy to transport, more safe?
    Using this as general rule that affects all hydrogen power source sounds like deliberately misleading.

  6. Steve Nordquist | April 2, 2023 at 11:11 pm | Reply

    It comes off as against blue hydrogen, which I can only agree with, thrilled though I may be to see CCS widely deployed in rock storage and downbore reactors to work near ports.

  7. Central Scrutinizer | April 3, 2023 at 2:26 am | Reply

    Matteo is a researcher and called Hydrogen a “fuel”?

    That’s just totally incorrect. Hydrogen is a storer of energy created elsewhere

  8. I have seldom seen such a large steaming pantload of speculative psychobabble as I see here. Brought to us by the very same criminals attempting to remain relevant but have been consistently wrong about EVERYTHING they have said for decades. Simply amazing!!!

  9. MarrionBerry8844 | April 3, 2023 at 12:02 pm | Reply

    Please explain… How does OH radiacal break down hydrogen? If it does break down hydrogen, what are the byproducts of such a reaction? You haven’t addressed these areas.

  10. Hydrogen’s biggest source is not electrolysis but hydrocarbon fossil fuels. Don’t be surprised to learn that the oil companies are the biggest promoters of h2 as a future fuel.

  11. It doesn’t matter what fuel is used to produce our energy needs. Each fuel, electric,hydrogen, fossil fuels, has its own negative consequences. The issue isn’t fuel types, it’s world population. Each individual requires x amount of energy to survive. More people = more needed energy = more pollution = more damage to the environment.

  12. When you burn hydrogen, say from naclh20, you release more O to bond with existing hydrogen making more OH

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