Lauded as clean and green energy to help reduce global warming, "Blue" hydrogen – an energy source that involves a process for making hydrogen by using methane in natural gas – is worse than gas and coal, said a new study by Cornell and Stanford University researchers.
The carbon footprint to create blue hydrogen is more than 20% greater than using either natural gas or coal directly for heat, or about 60% greater than using diesel oil for heat, and thus, it may harm the climate more than burning fossil fuel, said the new research finding published in Energy Science & Engineering.
Blue hydrogen starts with converting methane to hydrogen and carbon dioxide by using heat, steam and pressure, or gray hydrogen, but goes further to capture some of the carbon dioxide. Once the byproduct carbon dioxide and the other impurities are sequestered, it becomes blue hydrogen, according to the U.S. Department of Energy.
The process to make blue hydrogen takes a large amount of energy, according to Robert Howarth, professor of ecology and environmental biology at Cornell, together with Mark Z. Jacobson, professor of civil and environmental engineering at Stanford, who authored the report.
Industry promotes blue hydrogen as clean
"In the past, no effort was made to capture the carbon dioxide byproduct of gray hydrogen, and the greenhouse gas emissions have been huge," Howarth said. "Now the industry promotes blue hydrogen as a solution, an approach that still uses the methane from natural gas, while attempting to capture the byproduct carbon dioxide. Unfortunately, emissions remain very large."
Methane is a powerful greenhouse gas, Howarth said. It is more than 100 times stronger as an atmospheric warming agent than carbon dioxide when first emitted.
The United Nations' Intergovernmental Panel on Climate Change report released on Aug. 9 shows that cumulatively to date over the past century, methane has contributed about two-thirds as much to global warming as carbon dioxide has, he said.
Emissions of blue hydrogen are less than for gray hydrogen, but only by about 9% to 12%. "Blue hydrogen is hardlyemissions-free," wrote the researchers. "Blue hydrogen as a strategy only works to the extent it is possible to store carbon dioxide long-term indefinitely into the future without leakage back to the atmosphere."
An ecologically friendly "green" hydrogen does exist, but it remains a small sector and it has not been commercially realized. "The best hydrogen, the green hydrogen derived from electrolysis – if used wisely and efficiently – can be that path to a sustainable future," Howarth said. "Blue hydrogen is totally different."