Switching to hydrogen fuel could prolong the methane problem

Date:
March 13, 2023
Source:
Princeton University, Engineering School
Summary:
Hydrogen is often heralded as the clean fuel of the future, but
new research suggests that leaky hydrogen infrastructure could
end up increasing atmospheric methane levels, which would cause
decades-long climate consequences.


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FULL STORY ========================================================================== Hydrogen's potential as a clean fuel could be limited by a chemical
reaction in the lower atmosphere, according to research from Princeton University and the National Oceanic and Atmospheric Association.


==========================================================================
This is because hydrogen gas easily reacts in the atmosphere with the
same molecule primarily responsible for breaking down methane, a potent greenhouse gas. If hydrogen emissions exceed a certain threshold,
that shared reaction will likely lead to methane accumulating in the
atmosphere -- with decades-long 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."
* RELATED_TOPICS
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# Environmental_Policies # Energy_Issues #
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========================================================================== Story Source: Materials provided by
Princeton_University,_Engineering_School. Original written by Colton
Poore. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Matteo B. Bertagni, Stephen W. Pacala, Fabien Paulot, Amilcare
Porporato.

Risk of the hydrogen economy for atmospheric methane. Nature
Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-35419-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230313162740.htm

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