Burning low-carbon hydrogen for heating is significantly worse for the environment than using natural gas or diesel, a scientific study published Aug. 12 has found.
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Full life cycle greenhouse gas emissions from burning blue hydrogen for heating were more than 20% greater than using conventional natural gas, the report from researchers at Cornell and Stanford Universities said.
Blue hydrogen production, via steam methane reforming of natural gas with carbon capture and storage, also had higher fugitive methane emissions than conventional 'grey' hydrogen from fossil fuels because of increased natural gas use in powering the carbon capture operation, the study published in Energy Science & Engineering found.
Even with CCS, CO2 emissions from gas-based hydrogen are only up to 12% lower than for grey hydrogen, the report said. Greenhouse gas emissions from burning blue hydrogen were 60% higher than burning diesel for heat, it said.
"There really is no role for blue hydrogen in a carbon-free future," the report's authors said. "We suggest that blue hydrogen is best viewed as a distraction, something that may delay needed action to truly decarbonize the global energy economy."
The report -- the first peer-reviewed study of the life cycle emissions of blue hydrogen production -- assumed a CO2 capture rate of 85% for blue hydrogen production and noted that only two blue hydrogen production facilities were in commercial operation in 2021.
Equinor, which is developing one of the world's first large-scale blue hydrogen projects at H2H Saltend in the UK, said on its website its autothermal reforming technology was expected to produce hydrogen at 80% efficiency with a minimum carbon capture efficiency of 95%.
The company declined to comment on the report ahead of its publication. BP, which is also developing a large blue hydrogen project in the UK at Teesside, did not respond to a request for comment.
S&P Global Platts Analytics Long Term Hydrogen Forecast assumes H2 blending in the gas grid will have reached 6.6% by 2050, potentially reducing CO2 emissions for home heat by 21%.
The Cornell and Stanford paper said hydrogen's role in heating could be extremely limited from a climate perspective.
Hydrogen is widely used as an industrial feedstock in chemicals processes and refining. The vast majority of hydrogen produced globally is from fossil fuels, with no CO2 abatement.
The hydrogen industry is seeking to decarbonize its operations, while governments, policy makers and industry leaders see low-carbon and renewable hydrogen -- made from the electrolysis of water -- as key to the energy transition, with applications from transport to heating and power storage.
"Politicians around the world, from the UK and Canada to Australia and Japan, are placing expensive bets on blue hydrogen as a leading solution in the energy transition," co-author of the study and Professor of Ecology and Environmental Biology at Cornell University Robert Howarth said in a statement.
"This is a warning signal to governments that the only 'clean' hydrogen they should invest public funds in is truly net-zero, green hydrogen made from wind and solar energy," he said.
Many oil and gas companies are touting blue hydrogen as a transition fuel on the road to net-zero emissions that could be blended in distribution networks with natural gas.
The study assumed a 3.5% methane emission rate from natural gas, with a 20-year global warming potential. Even under a lower methane emission rate of 1.54%, greenhouse gas emissions from blue hydrogen were still higher than from burning natural gas, and 18%-25% less than for grey hydrogen.
Methane is a more potent greenhouse gas than CO2, but breaks down in the atmosphere over time, with a half-life of around 12 years.
The study also assumed the carbon captured would be stored indefinitely, something the report notes is "optimistic and unproven".
Powering blue H2
The energy required to produce the heat and pressure needed to make hydrogen from methane is significant, and comes almost entirely from natural gas, the paper said. The energy source would presumably be the same for blue hydrogen, it said.
The study noted that emissions from blue hydrogen could be cut by powering the process with renewable electricity. However, the fugitive methane emissions from the natural gas would remain, and are substantial, it added, with total greenhouse gas emissions still almost half of those from burning natural gas.
The report suggested renewable electricity would be better deployed in generating green hydrogen through electrolysis.
In addition, upstream indirect emissions from producing, processing, and transporting the natural gas used to generate hydrogen are around 7.5% of the direct CO2 emissions from natural gas, it said.
Blue hydrogen production is currently much cheaper than electrolysis, but green hydrogen costs are expected to come down rapidly with the rollout of more renewable power generation and cheaper electrolyzers as production scales up.
S&P Global Platts assessed the cost of producing renewable hydrogen via alkaline electrolysis in Europe at Eur6.02/kg ($7.1/kg) on Aug. 10 (Netherlands, including capex). PEM electrolysis production was assessed at Eur7.40/kg.
Blue hydrogen production by steam methane reforming (including carbon, CCS, and capex) was Eur3.28/kg, and hydrogen from unabated fossil fuels was assessed at Eur2.98/kg.