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Studies find methods for removing carbon dioxide must develop faster to meet climate goals

UW researchers say novel carbon dioxide removal technologies only make up 0.1 percent of emissions removed from the atmosphere

white smoke billows out of a smoke stack
Steve Helber/AP Photo

Researchers at the University of Wisconsin-Madison say new technologies for removing carbon dioxide from the atmosphere must be developed faster to meet goals to reduce global warming.

The role of such technologies is likely to be part of discussions as around 200 nations gather in the United Arab Emirates on Thursday for the 28th annual United Nations Climate Change Conference.

Carbon dioxide removal refers to a variety of methods, such as planting trees or direct air capture, that would remove carbon emissions directly from the atmosphere. They don’t include technologies that aim to capture emissions released directly from power plants or industrial facilities that use fossil fuels.

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Scientists and nations say those technologies are part of the solution to cut carbon emissions, but critics of the fossil fuel industry say oil and gas companies rely too heavily on such options to continue business as usual. A recent UN report warned temperatures may rise twice as high as the limit agreed to under the 2015 Paris climate accord. Scientists have urged limiting global warming to 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, by 2050. The goal means that hundreds of gigatons of carbon dioxide would need to be removed from the atmosphere by mid-century.

Last year, emissions grew 1.2 percent, equal to 57.4 gigatons or 57.4 billion tons of carbon dioxide emissions. UW-Madison researchers found only about 2 billion tons of carbon emissions are being removed each year, mostly through trees.

Greg Nemet, a professor in the university’s La Follette School of Public Affairs, said new technologies only account for a tiny fraction of what’s currently removed at about 2 million tons.

“We’re at one-one thousandth of the scale of what we’re already doing with trees and about one-one thousandth of the scale of where we need to get to in the next 30 years,” Nemet said. “So, there’s a lot of concern.”

Even so, some scientists have feared relying on technologies that remove carbon dioxide will only prolong the use of fossil fuels as the oil and gas industry have supported such measures. Nemet, who was a lead author of a recent UN report, said such technologies aren’t meant to allow business as usual. Instead, it’s aimed at removing emissions for parts of the economy where they’re currently difficult to avoid, including long-distance air travel.

As emissions continue to rise, Nemet said carbon dioxide removal technologies are too important to take off the table. While most of the solution relies on cutting emissions, Nemet said removing carbon dioxide will make up about 10 to 20 percent of what’s needed to reach net-zero emissions. That equates to about 5 to 10 billion tons of what’s currently being released into the atmosphere.

But he said there’s a limit to how much carbon can be removed by planting more trees because of competing land uses for agriculture and development.

“So that stimulates a lot of interest in other ways to remove (carbon dioxide) from the atmosphere,” Nemet said.

In a recent paper, researchers examined the growth of 148 technologies over the past century that span from medical advancements to cell phones. Jenna Greene, a doctoral researcher at UW-Madison, said their goal was to determine how quickly new carbon dioxide removal methods could be developed. Researchers found that scaling up those technologies is possible in order to meet goals aimed at limiting global warming.

“We see that carbon dioxide removal (technologies) may grow on the faster end of what we’ve seen historically to reach levels that are relevant for climate change,” Greene said.

Nemet said that means carbon dioxide removal technologies would have to grow at a rate of about 40 percent per year. He points to accelerated deployment of solar panels and electric vehicles as examples of other technologies that have been scaled up quickly.

“Those give us playbooks, things to learn from, policies that worked, ideas of how we could actually implement it, and most importantly, credibility that this is something that’s reasonable that can just be another tool in the solution set for addressing climate change and getting our emissions to zero,” Nemet said.

As technologies are developed, Greene said researchers determined the number of direct air capture plants that remove carbon dioxide would have to grow from 18 small facilities to around 90 large-scale plants by 2040.

But Greene and Nemet note it’s too early to pick winners and losers. Methods for removing carbon dioxide come with benefits for the climate, as well as risks. The downsides may include taking land out of food production for planting trees or direct air capture plants using a lot of energy to suck carbon out of the atmosphere. Researchers say the best path forward is to develop a diverse portfolio of technologies that can remove carbon dioxide, as well as funding and policies to support them.