STUDY: Emissions of Hydrogen Could Undermine Its Climate Benefits; Warming Effects Are Two to Six Times Higher Than Previously Thought

(Washington, D.C.) Clean hydrogen is increasingly seen by governments and industry as the Holy Grail of climate-friendly energy solutions, with vast sums flowing into this emerging sector. But a new study warns that hydrogen is a leak-prone gas with a potent warming effect that is widely overlooked, even by experts. If hydrogen is to achieve the environmental benefits that its backers promise, these climate scientists say comprehensive measures are needed to keep it from escaping to the atmosphere. 

The analysis appears today in the journal Atmospheric Chemistry and Physics.

“Hydrogen itself poses a greater warming risk than decision-makers realize. For ‘clean’ hydrogen to provide the hoped-for climate benefits, leakage has to be kept extremely low,” said Dr. Ilissa Ocko, Senior Climate Scientist at EDF and lead author of the study. “This is not a place to rush blindly. The process needs to be carefully designed and managed effectively from end to end.” 

Scientists have long known that hydrogen triggers indirect warming effects when released into the atmosphere. But utilizing recent atmospheric research, the authors show that its near-term warming power is two to six times greater than previously recognized.

Comparing against a mix of fossil fuels, scientists from Environmental Defense Fund assess the climate impact of hydrogen made either by using renewable electricity or from natural gas with the residual carbon dioxide emissions captured and stored – the two most widely anticipated methods for producing climate-friendly hydrogen.

Climate benefit depends on leakage

In best-case scenarios assuming a 1% leak rate across the value chain, they find that “blue” hydrogen made from natural gas (with the carbon dioxide captured and 1% methane leakage from the gas supply chain) could cut warming effects compared to traditional fossil fuels by 70% percent over 20 years. “Green” hydrogen produced using zero-emission electricity does even better, cutting the climate impact by over 95%.

But at a 10% hydrogen leak rate – which many scientists say is plausible – blue hydrogen (with carbon capture and 3% methane leakage) could actually increase the 20-year warming impact by 25%. “Green” hydrogen produced would still reduce the 20-year warming effects by two-thirds relative to fossil fuels, but far less than the climate-neutral promise that many hydrogen champions claim.

Implications for hydrogen strategy

Use-case is also important. Prior research suggests deployment of green hydrogen can require two to fourteen times more energy than available alternatives that use direct electrification.

“If the goal is to rapidly reduce greenhouse gas emissions cheaply, it makes no sense to divert clean electricity from the grid to make hydrogen for use in cars, homes or commercial buildings, where in almost all cases clean electricity can serve these energy needs directly” said EDF Chief Scientist Dr. Steven Hamburg and coauthor of the paper.

As the smallest molecule on earth, hydrogen is difficult to contain. Extensive measurements of methane emissions from the natural gas value chain show that there is often significant leakage. If methane is hard to manage, hydrogen will be harder still. Existing equipment will likely not be up to the task.

Hydrogen is most appropriate where other low-carbon options are lacking, such as steel and cement production, or as feedstock for low-carbon fuels for ships and planes. And since transporting hydrogen will increase the risk of leaks, it will make more sense to produce it close to where it’s used.

“It’s vitally important that both industry and policy-makers understand these realities before building tens of billions of dollars’ worth of infrastructure that won’t deliver the climate benefits we’re counting on,” Hamburg said.   

Overlooked warming power

Two factors account for the increased warming impact of hydrogen in the atmosphere reported in the paper. First is a use of a fuller understanding in the latest scientific literature of the effects that hydrogen causes in the atmosphere. Second is the time scale used.

Hydrogen doesn’t remain in the atmosphere as long as other climate pollutants, and its warming effects disappear after about two decades. But climate impacts are nearly always calculated over a 100-year timeframe, masking the damage caused by escaped hydrogen in the near term. To appropriately account for that effect, Hamburg and Ocko say it is critical to evaluate and report hydrogen’s climate effects over a 20-year timeframe as well.

In June, the U.S. Department of Energy announced an $8 billion plan to establish hydrogen hubs around the country. Hydrogen figures prominently in European climate efforts. More than a dozen other national governments have adopted hydrogen strategies. Companies have announced hundreds of hydrogen projects worth at least $600 billion.