The Lego-like way to get CO2 out of the atmosphere.

A company says that it has found a way to remove CO2 from the air for less than $100 per ton.

…a start-up says it has discovered a deceptively simple way to take CO2 from the atmosphere and store it for thousands of years. It involves making bricks out of smushed pieces of plants. And it could be a game changer for the growing industry working to pull carbon from the air.

Graphyte, a new company incubated by Bill Gates’s investment group Breakthrough Energy Ventures, announced Monday that it has created a method for turning bits of wood chips and rice hulls into low-cost, dehydrated chunks of plant matter. Those blocks of carbon-laden plant matter — which look a bit like shoe-box sized Lego blocks — can then be buried deep underground for hundreds of years.

The approach, the company claims, could store a ton of CO2 for around $100 a ton, a number long considered a milestone for affordably removing carbon dioxide from the air.

Carbon removal may not seem like a top priority — why not just stop using fossil fuels in the first place? — but virtually every projection of cutting greenhouse gas emissions to zero by 2050 involves some amount of it. That’s because certain areas of the economy like aviation, cement-making and steelmaking, are very challenging to do with renewable energy and batteries. It’s hard to make temperatures hot enough with electricity to produce cement or steel, and to fly planes on heavy lithium-ion batteries.

“We’ve bet the future of our planet on our ability to remove CO2 from the air,” said Chris Rivest, a partner at Breakthrough Energy Ventures. “Pretty much every IPCC scenario that has a livable planet involves us pulling like 5 to 10 gigatons of CO2 out of the air by mid- to late-century,” he added, referring to the United Nations Intergovernmental Panel on Climate Change.

Five to 10 gigatons of CO2 a year is around 12 to 25 percent of what humanity currently emits every year.

Graphyte’s approach uses the power of plants and trees to photosynthesize and pull carbon dioxide from the air. While trees and plants are excellent at carbon capture, they don’t store that carbon for very long — when a plant burns or decays, its stored carbon comes spilling back out into the air and soil.

Graphyte plans to avoid that decomposition by taking plant waste from timber harvesters and farmers and drying it thoroughly, removing all the microbes that could cause it to decompose and release greenhouse gases. Then, in a process that they call “carbon casting,” it will compress the waste and wrap it into Lego-like bricks, for easier storage about 10 feet underground. The company says that with the right monitoring systems, the blocks can stay there for a thousand years.

“The simplicity of the Graphyte approach is so exciting,” said Daniel Sanchez, who runs the Carbon Removal Lab at the University of California at Berkeley, and serves as a science adviser for Graphyte. “You don’t need very expensive equipment or processes. And it locks up a lot of the carbon in the wood — nearly all of it.”

Other approaches are much more complicated and, although proven, much more costly than the new company’s projected costs. Direct air capture, which involves using gigantic, fan-equipped machines to separate CO2 from other atmospheric gases, has gotten a lot of press and attention — but it’s still very expensive. The technology, which has been trialed in Iceland and the United States, costs around $600 to $1,200 to remove a single ton of carbon dioxide. (To think about whether that’s worth it, imagine having to pay $600 to $1,200 to offset the cost of one round-trip flight from the United States to Europe.)

Graphyte is planning to build its first project in Pine Bluff, Ark., and the company hopes to sequester its first carbon for a customer in 2024.

It remains to be seen whether Graphyte will be able to scale up its operation to removing millions of tons of CO2 from the atmosphere. The company will need to secure many sources of plant waste and build many small processing centers around the country to be successful.

But the very simplicity of the approach — using plants to trap CO2 and then stuffing them underground, in a kind of reverse-extraction of fossil fuels — might give the company a leg up against more complex and engineering-heavy ways of sucking carbon from the air.