The United States can reduce its carbon footprint to zero by 2050 — but only if the country invests swiftly and deeply in emerging technologies that draw carbon dioxide out of the atmosphere.

Federal funding of a range of carbon removal technologies, amounting to as much as $6 billion per year over the next 10 years, could put the U.S. on a path toward carbon neutrality by mid-century, according to a report released January 31 by the World Resources Institute, based in Washington, D.C. Being carbon-neutral means that the amount of U.S. emissions of carbon — primarily from burning fossil fuels like coal, oil and gas— is fully offset by the amount of carbon removed from the atmosphere.

Navigating a realistic path to carbon neutrality is tricky, though, with many scientific, economic and political uncertainties surrounding the available technologies. But by combining many different strategies for carbon removal, the report envisions that the United States could ramp up to removing up to 2 metric gigatons of CO 2 a year from the atmosphere by 2050.

This roadmap to carbon neutrality would devote about two-thirds of that initial decade of funding, or $4 billion a year, to support tree restoration projects across the United States. Strategies to integrate trees into croplands and pasturelands, for example, are already well understood. By starting with the trees, the report suggests, the nation could ultimately remove as much as 7 gigatons of CO 2 by 2050 — more than any other carbon removal pathway.

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Other carbon removal technologies have the potential to remove even more CO 2 than tree planting, but would require significant federal investment to become commercially viable, the report notes. Depending on how mature the technology is, some of the proposed funding would go to, for example, tax credits to support emerging technologies such as direct air capture, in which CO 2 is pulled directly from the ambient air using giant fans (SN: 12/17/18). This technology has been tested in pilot projects but has not yet made the leap to commercial-scale development.

Other funding would support more scientifically uncertain but potentially game-changing strategies, such as carbon mineralization. This CO 2 -storage concept involves “mineralizing” the gas, converting it into carbonate minerals, and then sequestering it underground (SN: 8/22/18). It’s a strategy that is still in the laboratory phase, as scientists wrangle with its technological challenges.

The new “CarbonShot” report weighs the costs and benefits of these various approaches toward zero emissions, says James Mulligan, a senior associate with WRI’s food, forests and water program. The report “really focuses on [finding] the small set of U.S. federal policy options” that will kick-start a carbon removal technological boom, says Mulligan, who previously worked in the U.S. Office of Management and Budget from April 2014 to July 2017.

Science News asked Mulligan about some of the details of his team’s report, and why the authors felt this approach was needed for the United States. His responses are edited for brevity and clarity.

SN: Why is removing 2 gigatons of CO 2 a year the target?

Mulligan: Studies such as the 2016 Deep Decarbonization Strategy have consistently shown that, even if we successfully implement strategies to reduce emissions, there will be a fair amount of emissions left hanging around by 2050. We’d still need to remove them [to become carbon-neutral]. Of course it’s conceivable that the U.S. will need to remove more, if we don’t significantly reduce emissions.

SN: Why does the report discuss carbon removal technologies that aren’t yet ready for use?

Mulligan: It’s conceivable that we can get 2 gigatons of CO 2 out of the atmosphere with tree planting and direct air capture alone, but that’s a fairly narrow path to success. We’re approaching carbon removal from a risk management framework, how to put more options on the table. If carbon mineralization does come online, it’s ultimately more cost-effective and removes more CO 2 from the atmosphere [than tree planting]. I want to have a whole quiver of options that we can slot in.

SN: The roadmap calls for spending $4 billion a year in the next decade on tree restoration. Why so much?

Mulligan: It’s not just traditional reforestation. We have done extensive scouring of the landscape for opportunities to get more trees, especially restocking eastern timberlands and integrating trees into pasturelands. All told, there’s a lot of uncertainty, but we’re looking at 60 billion trees. Trees cost money, especially when they’re not going to be harvested. The cost of restoration is going to exceed benefits to private landowners, but there’s an enormous public benefit.

SN: Americans overall support investing in trees, but less so carbon removal technology. Why?

Mulligan: People don’t yet understand the technology; it’s not real yet. They’re just going to put it out of mind until someone develops it. But I think that policy makers do understand the opportunity here, and we’re getting real traction. It’ll permeate the public consciousness as we start to get more pilot projects, real facilities that people can see and understand.

SN: Why focus so much on federal dollars? What about state and more local investment?

Mulligan: The states are going to play a huge role here, especially in the land sector. State leadership is critical. But we’re mindful that states have to balance their budgets, that they’re in a very budget-constrained environment. Given the investment scale needed for deployment, it’s going to have to come from direct federal investment if we’re going to get the private sector involved. Still, on the technological side, there are things states can do to create a favorable environment for investment, such as setting research priorities for state universities.

SN: How likely is it that this roadmap will get support from politicians and government?

Mulligan: I think it’s quite feasible. The biggest chunk is the $4 billion a year for trees, which is equivalent to what we spend on photovoltaics [solar panels] or in fossil fuel subsidies. The carbon removal dimension could very well be a co-benefit there, in addition to things like air quality and water quality benefits. And we’re already getting interest from [politicians].

On the technological side, there’s similar interest, and from both parties, which is really important.

SN: What else should people take away from this report?

Mulligan: It’s important for people to remember that we need to do this in addition to reducing emissions. Also, given what’s at stake [with climate change], it’s important that we take this risk management approach, putting as many options on the table as we can.