What is the most efficient way to remove CO2 from the atmosphere?

We don’t yet know how carbon removal technologies will compare at scale, and there is probably no one “best” method in all times and places.

April 7, 2025

The most important fuel for today’s climate change is the carbon dioxide (CO₂) humans are adding to our atmosphere. To stabilize our climate, we urgently need to cut that planet-warming pollution. But maybe you’ve also heard of strategies to pull some of that CO₂ back out of the air. Already, people are rolling out carbon removal plans as low-tech as planting more trees, and as involved as building big machines to suck CO₂ from the sky.

You might ask: Which of these strategies is the most efficient?

“It’s a very good question with a very simple answer: depends,” says Angelo Gurgel, a principal research scientist with the MIT Center for Sustainability Science and Strategy and the MIT Energy Initiative.

If by “most efficient” we mean “least pricey,” the big CO₂-sucking machines are likely not our best bet. These “direct air capture” (DAC) systems use chemical reactions to isolate CO₂ from the atmosphere. The CO₂ can then be locked away underground for the long term.¹

Thanks in part to its high energy demands, DAC is quite costly. To give a rough idea: The operator of the largest DAC plant working today is currently charging individual customers $1,000 per ton of CO₂ removed from the air.²

As DAC matures, the price is expected to fall—perhaps in the not-too-distant future, as multiple plants are in various stages of planning and construction. But just how far the price can come down is hotly debated. Some scientists are optimistic that DAC could one day capture CO₂ for $100-$300 a ton;³ in their research, Gurgel and his colleagues conclude that $380-$660 is a more plausible range.⁴

There are cheaper ways to take CO₂ out of the air. One possibility, Gurgel says, is bioenergy with carbon capture and sequestration (BECCS). BECCS relies on the power of plants to absorb CO₂ as they grow. Normally, that CO₂ would just reenter the air when the plants die and decompose, but BECCS has a technological workaround. The plant material is used to make electricity or fuels, and the CO₂ released by those processes is captured and stored underground.

Like DAC, BECCS is in its infancy, but there are good reasons to think it could be cheaper. For one thing, it’s a lot easier to pull CO₂ from a concentrated stream, as you would with BECCS, than to extract it from the air. It’s hard to know how much BECCS would cost at scale, but research by Gurgel and his colleagues suggests it could eventually remove CO₂ from the air for $260 a ton or less.⁴

But in another way, BECCS may be far less efficient than DAC. Growing crops for BECCS takes a lot of land. At the scale needed to make a dent on climate change, the space might be hard to find—and clearing it can pose risks for natural ecosystems, or drive up food prices if other crops get pushed out.

Can we get more cost-efficient still? Among the cheapest strategies, Gurgel says, are tree-planting and storing carbon in farm soils. At the lowest estimates, these methods could eventually cost just dollars per ton of CO₂.³ But they add a new trade-off: Making sure the carbon stays put is a challenge. For instance, if we plant a new forest to absorb CO₂, but then disease or wildfire kills those trees, the carbon goes right back into the atmosphere.

There are also costs that are harder to measure than dollars or acres of land. Consider enhanced rock weathering, which aims to speed up the slow, natural Earth process that moves carbon from the air and stores it in minerals. A common approach is to crush rocks and spread them out, accelerating the chemical reactions that draw down CO₂. As with all kinds of carbon removal, it’s not clear what enhanced weathering would cost on a large scale, but Gurgel’s research suggests it could be cheaper than DAC and probably doesn’t need as much dedicated land as BECCS.

But although enhanced weathering may turn out to be both reasonably cost-efficient and reasonably land-efficient (at least by carbon removal standards), it’s not very rock-efficient. When Gurgel and his colleagues modeled a scenario that used a mix of removal options to control climate change, they found that their model eventually called for mining 25 billion tons of rock a year for weathering: about three times the world’s coal production today.⁴ Researchers are also unsure of the environmental and health effects of mining and spreading so many rocks.⁵

The best carbon removal strategy, Gurgel believes, isn’t a single strategy at all—it’s a mix. According to his model, using several options keeps costs down while limiting pressure on land and energy resources.⁴ That flexibility also means countries and regions can think locally—How much land is available for BECCS? How cheap is clean electricity for DAC?—and pursue the strategy that makes the most sense for them.

Plus, many of these strategies are in their infancy, and gauging how they will evolve over time is challenging. Keeping our options open hedges against uncertainty, Gurgel says. “It’s like in the financial sector. A diversified portfolio is much safer than a concentrated investment in one or a few assets.”

And, lest we forget, the most important investment in that portfolio is not CO₂ removal at all; it’s keeping climate pollution out of the air in the first place.⁶ If we’re building large amounts of new clean energy, using it to power DAC has to be measured against using it to… well, run our homes and businesses on clean energy. If we care about forests as a climate solution, planting new trees has to be compared with protecting those we already have. In the search for the most efficient measures to deal with climate change, Gurgel says, we are still far from the point where CO₂ removal of any kind is the cheapest or easiest option.

Thank you to Stephen Anthony Murphy of London, U.K., for the question.

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