In theory, it might be possible to collect wood or other plant matter that has absorbed carbon dioxide from the air, burn it in biomass power plants for energy and then capture the carbon released from combustion and bury it deep underground, creating, in essence, a power plant that has negative emissions. While no such facilities are operating commercially today, the technology to build them exists.

But one potential problem with this approach, the National Academies panel said, is that the land required to grow biomass for these power plants could run into conflicts with the need for farmland for food. The panel estimated that this method might one day be able to remove 3 to 5 billion tons of carbon dioxide from the air each year, but possibly much less, depending on land constraints.

That’s a far cry from the 10 to 20 billion tons of carbon dioxide we may need to pull out of the air by the end of the century in order to limit overall global warming to around 1.5 degrees Celsius (2.7 degrees Fahrenheit), according to the recent United Nations report. That figure assumes nations manage to decarbonize their energy and industrial systems almost entirely by 2050.

If nations fail to hold global warming below that 1.5 degree level, the United Nations report warned, tens of millions more people could be exposed to life-threatening heat waves and water shortages, and the world’s coral reefs could disappear almost entirely.

The National Academies panel recommended a dual strategy. The United States could set up programs to start testing and deploying carbon removal methods that look ready to go, such as negative emissions biomass plants, new forest management techniques or carbon farming programs.

At the same time, federal agencies would need to fund research into early-stage carbon removal techniques, to explore whether they may one day be ready for widespread use.

For instance, scientists have long known that certain minerals, like peridotite, can bind with carbon dioxide in the air and essentially convert the gas into solid rock. Researchers in Oman have been exploring the potential to use the country’s vast mineral deposits for carbon removal, but there are still major questions about whether this can be done feasibly on a large scale.