Blue hydrogen’s Achilles’ heel is the methane used to produce it. Methane is the dominant component of natural gas, and while it burns more cleanly than oil or coal, it’s a potent greenhouse gas on its own. Over 20 years, one ton of the stuff warms the atmosphere 86 times more than one ton of carbon dioxide. That means leaks along the supply chain can undo a lot of methane’s climate advantages.

Anyone who lives in an area with old pipelines knows that gas leaks are an unfortunate reality. Methane is a small molecule, and it’s great at finding cracks in the system. Gas wells and processing facilities are also pretty leaky. Add it all up, and anywhere between 1-8 percent of all energy-related methane escapes into the atmosphere, depending on where and how it's measured. //

“Combined emissions of carbon dioxide and methane are greater for gray hydrogen and for blue hydrogen (whether or not exhaust flue gases are treated for carbon capture) than for any of the fossil fuels,” Howarth and Jacobson wrote. “Methane emissions are a major contributor to this, and methane emissions from both gray and blue hydrogen are larger than for any of the fossil fuels.”