There’s a mountain of hydrogen hidden beneath Earth’s surface — and scientists say just a tiny fraction of it could last us 200 years of our dependence on fossil fuels.
New research suggests there’s about 6.2 trillion tons (5.6 trillion metric tons) of hydrogen in rocks and underground reservoirs on Earth. That’s about 26 times the amount of oil left in the ground (1.6 trillion barrels, each weighing about 0.15 tons) — but where these hydrogen stocks are located is still unknown.
Researchers suspect that most of the hydrogen is probably too deep or too far offshore to be accessed, and some reserves are probably too small to be economically sensible to extract. However, the results suggest there’s enough hydrogen even with these limitations, Jeffrey Ellis, a petroleum geochemist at the U.S. Geological Survey (USGS) and lead author of the new study, told Live Science.
Hydrogen is a source of clean energy that can fuel vehicles, power industrial processes and generate electricity. Just 2% of the hydrogen stock found in the study, which equates to 124 billion tons (112 billion metric tons) of gas, “would supply all the hydrogen we need to reach net-zero [carbon] for a few hundred years,” Ellis said.
The energy released from that amount of hydrogen is about twice the energy stored in all known natural gas reserves on Earth, Ellis and his co-author Sarah Gelman, also a USGS geologist, noted in the study. The results were published Friday (Dec. 13) in the journal Science Advances.
To estimate the amount of hydrogen inside the Earth, the researchers used a model that incorporated the rate of production of the gas underground, the amount likely trapped in reservoirs and the amount lost through various processes, such as leaching out of rocks and into the atmosphere.
Hydrogen is formed through chemical reactions in rocks, the simplest reaction being the one that splits water into hydrogen and oxygen, Ellis said. “There are actually dozens of natural processes capable of generating hydrogen, but most of them generate very small amounts of hydrogen,” he added. Until recently, researchers didn’t realize that hydrogen was stored beneath the Earth’s surface.
“The paradigm throughout my career was that hydrogen is there, it occurs, but it’s a very small molecule, so it easily escapes from small pores and cracks and rocks,” Ellis explained. But that paradigm changed when scientists discovered a huge deposit of hydrogen in West Africa, and then another in an Albanian chromium mine. It’s now clear that hydrogen forms in Earth’s reservoirs, and the new study suggests that some of those accumulations may be very large. “
I was surprised that the results were much larger than I thought,” Ellis said. “This suggests that there’s a lot of it out there.” But it’s important to note that there’s a lot of uncertainty about these results, he said, because the model showed there could be anywhere from 1 billion to 10 trillion tons of hydrogen out there. (The most likely value was 6.2 trillion tons, depending on the model’s assumptions.)
Hydrogen is estimated to contribute up to 30% to future energy supplies in some regions, and global demand is expected to grow fivefold by 2050. The gas is produced artificially through the electrolysis of water, where water molecules are broken up with electrical currents. When renewable energy is used, the product is called “green hydrogen,” and when fossil fuels are used, it’s known as “blue hydrogen.”
The benefits of tapping natural hydrogen are that it doesn’t require an energy source to make it, and underground reservoirs can hold the gas until it’s needed.
“We don’t have to worry about storage, which is what happens with blue hydrogen or green hydrogen — you want to make it when electricity is cheap and then you have to store it somewhere,” Ellis said. With natural hydrogen, “you can just open a valve and close it whenever you need it.”
The biggest question is where all this hydrogen is ultimately located, which will affect whether it’s accessible. Ellis and his colleagues are moving toward nailing down the geological criteria needed to create underground accumulations, and results for the U.S. could be published as early as next year, he said.
