Hydrogen is gaining attention as a low-carbon alternative to fossil fuels. However, most hydrogen produced today comes from a method called steam reformation where high-pressure steam reacts with methane, the main component of natural gas. This method results in high carbon dioxide emissions. Another option is to use energy-hungry electrolysis to separate hydrogen from water. But potentially sizable natural hydrogen reserves in Earth’s crust remain largely untapped. Whether its production will prove climate-friendly is unknown.
In a new study, Stanford University scientist Adam Brandt provides the first preliminary greenhouse gas estimates for natural hydrogen production, indicating its promise as a source of clean energy.
“It’s important work,” says Michael Webber, a clean technology expert at the University of Texas at Austin, “because there are a lot of questions out there about hydrogen [linked] emissions but also about geological hydrogen.”
Brandt used a technique called life cycle analysis to estimate greenhouse gas emissions that occur during various steps involved in obtaining natural hydrogen. He altered a model that makes similar estimates for conventional oil and gas generation and applied it to the processing and purification of hydrogen gas. Accounting for parameters like concentration of the gas, well productivity and depth, and methods of powering the production and handling waste, he found emissions to be as low as 0.4 kilograms of greenhouse gases for every kilogram of hydrogen produced (Joule 2023, DOI: 10.1016/j.joule.2023.07.001).
“The numbers are very impressive,” says Viacheslav Zgonnik, who reviewed the study and is also the CEO of Natural Hydrogen Energy. The lifecycle emissions for natural hydrogen are lower than those for hydrogen produced from several other methods, he says.
The emission estimates, albeit preliminary, were low for scenarios where productive reservoirs hold high concentrations of hydrogen gas and when production is powered by clean energy sources. Brandt suggests revising the analysis once commercial extraction of natural hydrogen commences and real data become available.