Researchers from New Mexico's Sandia National Laboratories have a new tenant in mind for dirty gas and oil's old underground digs.
By moving hydrogen into the subterranean reservoirs, the experts think they can provide long-term storage for the cleaner energy source.
"If we want to create a hydrogen economy, we really need widely distributed means of storing large quantities of hydrogen," Don Conley, the manager for Sandia's underground hydrogen storage work, said in a statement.
Hydrogen is tougher to compress and keep in tanks than other fuels, including natural gas and propane, making surface storage difficult, according to Sandia. However, hydrogen doesn't emit planet-warming air pollution when used as a fuel, making it an appealing alternative to gas. Cars, trains, and even planes are already powered by hydrogen.
Sandia's research suggests that after being evicted via drilling or fracking, the fossil fuels are leaving behind what may be ideal abodes for hydrogen. Safely underground, it can be resurfaced months later when needed.
"Hydrogen would be good for seasonal and long-term storage," Sandia chemical engineer Tuan Ho, who is leading the study, said in a lab report. "If you think of solar energy, in the summer you can produce a lot of electricity, but you don't need a lot for heating. The excess can be turned into hydrogen and stored until winter."
The experts still have further analysis to complete. The team is studying how well hydrogen can be injected into the ground — where it will meet neighbors in the form of shale, sandstone, and mud — and later recalled to the surface. Early tests indicate that only a small amount will be lost underground.
Some residual natural gas or oil may also be pulled out with the hydrogen.
"That's not terrible because natural gas still has energy, but it contains carbon, so when this hydrogen is burned, it will produce a small amount of carbon dioxide," Ho said. "It's something we need to be aware of."
And hydrogen fuel isn't without critics.
The Sierra Club notes that its combustion releases nitrogen oxides (NOx), which can cause asthma and other lung problems. However, the U.S. Department of Energy reports that NOx emissions typically happen in specific scenarios and are no worse than what is released when dirty fuel sources are burned.
Natural gas is also commonly used in the process of making hydrogen through another method, called electrolysis, which can leverage renewably generated electricity to split hydrogen from water in a cleaner approach.
Hydrogen-powered transportation has the potential to reduce massive amounts of world-heating air pollution that is contributing to troubles even in our oceans' depths.
According to the federal government, the average car produces about 5 tons of air pollution annually. While hydrogen alternatives aren't yet common transportation options, you can still contribute to better air quality with your legs.
By replacing a mile-long drive with a walk each day, you can eliminate 180 pounds of air pollution in a year. Better yet, your health will likely improve as well.
In the meantime, Sandia's team is continuing to study underground hydrogen storage, potentially one day putting the cleaner fuel safely beneath our feet.
"It's all in the name of decarbonizing the energy sector," Conley said in the lab summary.
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