Hydrogen leaks raise GHG concern

Hydrogen as an energy source has been embraced by several global steelmakers as a greenhouse gas (GHG) emissions reduction tactic. However, the Norway-based Center for International Climate Research (Cicero) says some of that good could be negated if too much hydrogen leaks into the atmosphere during its production, use and transportation.

“The global warming effect of leaked hydrogen is almost 12 times stronger” than that of carbon dioxide, Cicero concludes in a report published by the journal Nature Communications Earth & Environment.

The report, with Cicero staff member Christian Bjørnæs as lead author, was prepared to help “fill a gap in our knowledge about the climate effects of hydrogen, a central technology in the energy transition,” according to Cicero.

Unlike exhaust from burning coal and gas that contains CO₂, burning hydrogen emits only water vapor and oxygen, but the leaking of hydrogen from production, transportation and usage can add to global warming, Cicero writes.

“Hydrogen is not a greenhouse gas, but its chemical reactions in the atmosphere affect GHGs like methane, ozone and stratospheric water vapor," Cicero says. "In this way, emissions of hydrogen can cause global warming, despite its lack of direct radiative properties.”

Steel producers that recently announced projects with hydrogen fuel as an energy source include H2Green Steel in Sweden, Liberty Steel in Australia, Voestalpine AG in Austria, Ternium S.A. in Mexico, Blastr Green Steel in Finland and ArcelorMittal in France.

Proponents of increased scrap recycling use in steel produced via the electric arc furnace (EAF) method have not opposed the use of hydrogen but have lobbied for wider acknowledgement that recycling has proven itself as a GHG emissions reduction method.

Contacted by Recycling Today, Srinath Krishnan, one of the five Cicero researchers who contributed to the study, indicates that in metals production applications, substituting hydrogen for coal as a fuel still offers net reductions in carbon emissions.

“It is important to note that though hydrogen leaks have a climate impact, using hydrogen to phase out very CO₂-intensive applications is still likely to be a very effective climate mitigation measure,” Krishnan says.

He adds, “What our study points out is that attention should be paid to potential leakages to ensure the best climate outcome. In addition, we are currently working on a study where we investigate the climate impact of sector-specific replacement scenarios, including one where hydrogen is used in steel production.”

The Cicero hydrogen leaks study was led by Maria Sand, Ph.D., a senior scientist at the center, and her colleagues along with collaborators from the United Kingdom, France and the United States. It was funded by the Research Council of Norway “with contributions from five hydrogen industry partners,” Cicero says.

“The climate effects of hydrogen have been an under-researched topic,” Sand says. “We used five different atmospheric chemistry models and investigated changes in atmospheric methane, ozone and stratospheric water vapor.

“We have assessed the uncertainties, and our study forms a robust foundation for political decision-making on hydrogen. A global warming potential (GWP100) of 11.6 is significant, and our study clearly shows the importance of reducing hydrogen leaks,” says Sand, referring to an index designed to measure how much infrared thermal radiation a GHG added to the atmosphere would absorb over a given time frame.

“We lack the technology to monitor and detect hydrogen leaks at the scale needed, but new technology is being developed as the industry adapts," Sand adds. 

The researchers say the potential benefit of switching to a hydrogen economy will depend on the magnitude of hydrogen leakages and to what extent hydrogen replaces fossil fuels.

“There are still many open questions, and our group will continue to expand our knowledge to ensure timely and accurate decision-making on a key mitigation technology," Sand says.

The full Cicero paper on hydrogen fuel leaks can be found here.