Trees, big fans, and deep-rooted plants: How to suck 2 gigatons of carbon from the atmosphere

To have a chance of avoiding the worst impacts of climate change, society needs to reach net-zero emissions by 2050—meaning that if we can’t transition to an emissions-free economy by that time, we’ll need to find ways to remove everything we’re still pumping into the atmosphere. In the U.S., even if society massively transforms in line with a “deep decarbonization” pathway, we’ll still have a gap that needs to be closed with so-called negative emissions tech, including trees and direct air capture machines that pull carbon from the air.

A new report from the nonprofit World Resources Institute looks at what it would take for the U.S. to be able to remove around 2 gigatons of CO2 from the air each year by 2050. It’s a huge amount, the equivalent of nearly a third of total annual emissions in the country in 2017. But it’s the scale that’s likely necessary to limit global temperature rise to 1.5 degrees Celsius. The report identifies five ways to get there.

Tree restoration

Restoring trees on one-third to two-thirds of the suitable land in the country—including degraded areas that aren’t used for farming and urban land—could capture between 180-360 megatons of CO2 a year by 2040, World Resources Institute estimates. The report suggests new policies such as a tax credit or payment program to incentivize landowners to plant and maintain trees in priority areas.

Direct air capture

The first direct air capture plant opened in 2017, using new technology to suck carbon from the atmosphere. Two other startups in the space also now have plants that are operating, and have attracted investors ranging from Bill Gates and Goldman Sachs to oil companies like Chevron. But to reach the scale that’s needed, the report says that the government should invest to support basic research and development in the field, and add more support to help the industry pioneers scale up. A tax credit of $20 per metric ton of sequestered CO2 already exists, but could be larger. By midcentury, the industry could be removing 1 gigaton of CO2 each year.

Agricultural soil carbon management, or regenerative agriculture

When farmers adopt “regenerative agriculture” practices such as no-till farming and planting cover crops, it can help farm fields store extra carbon in the soil. Some food companies, such as General Mills, are now working with suppliers to get these practices adopted on a wider scale. In some cases, farmers can sell carbon credits when they’ve proven how much CO2 they’ve helped capture. Because research in this area is still new, it still isn’t clear how much efficacy may vary in different regions, but the report calculates that if 10 million acres of farmland adopted this type of management, it could potentially store 100-200 megatons of CO2 a year by 2050.

Carbon mineralization

Certain rocks capture CO2 when they’re exposed to it. Blue Planet, one startup, captures CO2, dissolves it in a solution, and then combines it with rock waste from industry, creating new aggregate that can be used as a building material. Others inject CO2 into concrete. WRI says that these approaches still need more development and that the government should invest in more research, because it isn’t yet clear what’s technically and logistically possible. But carbon mineralization could potentially remove as much as 410 megatons of CO2 a year by 2050.

Enhanced root crops

If plant breeders develop new crops with deeper, longer roots, that could potentially also help capture more carbon as the roots reach deep underground. (One crop of this type, called Kernza, already exists, and is used in products like Long Root Pale Ale, a beer that Patagonia markets for its ability to help capture carbon). By 2050, though the report says “estimates remain highly theoretical,” crops like this could potentially remove as much as 185 megatons of CO2 each year.

For all of this to work, it will take government investment now. But there’s some indication that it can get the political support it needs. “This is probably one of the most interesting areas for bipartisan political support,” says James Mulligan, a senior associate at World Resources Institute. Congress successfully passed a tax credit for carbon sequestration in 2018, and appropriated $60 million to the Department of Energy last month to develop carbon removal technology. The new report is made to offer more guidance. “We wanted policymakers to have a consolidated roadmap,” he says.