Why Humans Are Putting a Bunch of ‘Coal’ and ‘Oil’ Back in the Ground

In addition to burying solid carbon or sprinkling it on fields, researchers are also turning waste biomass into liquid carbon—oil, essentially, that they pump back into the ground instead of pumping the fossil variety up. “What we do at the highest level is we make barbecue sauce—or liquid smoke for barbecue sauce—and then we inject it into old oil wells,” says Peter Reinhardt, CEO and cofounder of the carbon removal company Charm.

They also do this with pyrolysis, which spits out solid char for agriculture, but also liquid oil. That’s shipped to abandoned wells and pumped underground, where it solidifies. “There’s about 2 to 3 million abandoned, end-of-life oil and gas wells across the United States,” says Reinhardt. “It’s quite a problem, actually—a lot of them are methane emitters or improperly sealed, with fluid leaking up to the surface.” By pumping its biomass oil underground at these sites, Charm both sequesters carbon and seals up wells that have been leaking greenhouse gases.

Whatever the end product, biomass removal cleverly exploits nature’s own photosynthesis to sequester and then bury carbon. “The genius in this business model, in many ways, is letting nature do most of the work,” says climate economist Gernot Wagner of the Columbia Business School. “This is a natural process that’s been perfected over millions of years, so why not take advantage of it?”

In reality, though, things are more complicated, Wagner says. When fossil fuel companies remove coal or oil from the earth, they’re tapping into huge deposits that are relatively easy to exploit on the cheap, hence the prices of those fuels remain low. But there’s only so much biomass waste available above ground, and it’s distributed across the planet. (Though this is a potential strength of this kind of carbon removal, in that each municipality could process its own biomass waste for storage.) “The more demand there is for biochar, or for this kind of carbon removal technology, the more startups are out there clamoring for the same food waste, corn husk waste, and so on,” says Wagner. “Suddenly, the prices increase, rather than decrease.”

The other potential issue, Wagner says, is the “moral hazard”: If humanity is able to delete carbon from the atmosphere, that’s less incentive to slash emissions. There’s still so much money to be made in fossil fuels, and indeed, oil companies like Occidental Petroleum are investing heavily in carbon removal technologies like direct air capture, in which machines scrub the air of CO₂. That way, they can keep on drilling. “There is always this moral hazard aspect,” says Wagner. “The big, big topic in the background behind any of these carbon removal conversations is: OK, well, we could—or should, frankly—be doing more to reduce emissions in the first place, as opposed to let’s suck it back out after the fact.”