Climate change, along with the growing problems it’s creating around the globe, is being fueled by greenhouse gases trapped in the atmosphere. But what if those gases could be erased? 

Emerging technologies that essentially vacuum carbon dioxide out of the air are being heralded by some as a game-changing weapon in the fight against climate change. But the industry still has a long way to go, and it has its share of detractors.

While decades old, direct air capture, or DAC, is very much still in its infancy, but experts predict the industry will see significant growth over the next several years. 

According to the International Energy Agency, there are currently 19 DAC plants in operation worldwide, capturing around 10,000 tons of CO2 a year. To compare, the world emits about 36 billion tons annually, a number that, with the exception of the pandemic-fueled anomaly of 2020, continues to rise despite environmentalists warning that time is running out to avoid the catastrophic effects of global warming. 

Those, they say, would include higher sea level, tropical storms that are more frequent and intense, heat that is more extreme, droughts that are more prevalent and hurt food supplies, and wildfires that threaten homes and businesses.

Why DAC?

Mostly due to the burning of fossil fuels, the concentration of CO2 in the atmosphere today is nearly 420 parts per million, 50% higher than it was before the industrial revolution. 

Carbon dioxide remains in the atmosphere anywhere from 300 to 1,000 years. That means, even if the world were to achieve net-zero carbon emissions today, there would still be plenty of CO2 hanging around and warming the planet.

The 2015 Paris Agreement set a goal of limiting human-caused warming to “well below” 2 degrees Celsius compared to pre-industrial levels, and ideally 1.5 degrees. Because natural methods of removing CO2 — such as reforestation and wetlands restoration — are slower and would require vast amounts of land, the Intergovernmental Panel on Climate Change has said “negative emissions technologies” are needed to remove excess CO2 from the air.

“In order to stabilize the climate, we need to completely stop all emissions,” said Klaus Lackner, director of the Center for Negative Carbon Emissions at Arizona State University and a pioneer in direct air capture. “If we stop wherever we are, for thousands of years, it won’t get any better. And so if we want to fix the problem, they have to come back down.”

DAC insiders and experts, however, don’t consider the technology a panacea for the climate crisis.

“If we’re right, we’re going to be a really, really important tool in the toolbox that helps us get all the way to net zero,” said Lori Guetre, vice president and head of business development at Carbon Engineering, a Canadian DAC firm. 

“When you look at how do we get to net zero, what you see is we actually have all of the technologies to get to net zero, and direct air capture will play a big role,” along with wind and solar power, electric cars, energy-efficient buildings, and other technologies, Guetre added. 

In addition, some sectors — including aviation and the steel, cement and chemical industries — are widely considered difficult to decarbonize, and direct air capture could help offset their emissions.

How it works

Direct air capture most commonly uses one of two approaches.

In one, air passes through chemical solutions, which remove the CO2, before the chemicals are heated up and the carbon-filtered air is returned to the atmosphere.

The other method uses solid sorbent filters that chemically bind with CO2. The filters are then heated and placed under a vacuum, which captures concentrated CO2. 

Once captured, the carbon dioxide can either be permanently stored underground or reused. If stored underground, it can be injected into rock formations, where it mineralizes over time, or pumped into depleted oil and gas reservoirs using existing pipes. 

Or the captured CO2 could be combined with hydrogen and used to create synthetic oil for fuels, plastics and more. While burning synthetic fuel would re-release the carbon dioxide, there would still be a climate benefit because it would not introduce new CO2 into the atmosphere.

For example …

In Iceland, a plant run by the Swiss company Climeworks, uses the solid direct air capture method. Fans suck in the air, which passes over the sorbent filters, trapping the carbon dioxide. The filters are then heated, releasing the CO2, which moves through pipes to an adjacent building. There, it’s mixed with water.

One advantage of direct air capture is that plants can have small land or water footprints and be located on non-arable land near suitable storage, eliminating the need for long pipelines. 

That comes into play in Iceland, where the carbonated water is injected into basaltic rock about a quarter-mile underground.

While the Climeworks plant, which came online last September, is the largest in the world in operation, it removes just 4,000 tons of CO2 a year — which amounts to the emissions of about 800 passenger vehicles. Climeworks also is working on projects in Oman and Norway.

Meanwhile in the Permian Basin in west Texas, Carbon Engineering and 1PointFive, a subsidiary of Occidental Petroleum Corp., are developing the first large-scale DAC plant. The goal is to capture 1 million tons a year there. 

“A million tons is just a building block,” Guetre said, a sign that her firm — and the DAC industry as a whole — has big plans.

Carbon Engineering uses the liquid DAC approach. Giant fans pull air into a piece of equipment, where it passes over thin plastic surfaces that have potassium hydroxide flowing over them. The solution chemically binds with CO2 molecules, removing them from the air and trapping them in the liquid solution as a carbonate salt. 

The CO2 in the solution then undergoes a series of chemical processes so that it can be delivered in gas form that can be stored or reused, although Carbon Engineering says its main focus is burying the CO2 deep underground, in this case an emptied oil reservoir.

The companies plan to break ground on the facility this year, with plans for it to come online in 2024.

Future of the industry

For direct air capture to make a dent in the climate crisis, the industry needs to scale up dramatically. The National Academy of Sciences estimated in a 2019 report that to meet the Paris Agreement goals, about 10 gigatons of CO2 must be removed globally every year by 2050 — and 20 gigaton from 2050 to 2100. 

That means 10,000 operations the size Carbon Engineering’s Texas plant are needed.

And some experts put the estimates even higher. Lackner, for example, says 40 gigatons is a “not unreasonable number to aim for.”

Can the industry get to where it needs to be? 

Mihri Ozkan — a climate action professor at the University of California, Riverside — said there’s still much uncertainty about direct air capture’s future.

“The technology readiness levels are not high enough to accurately make any predictions or calculations for future DAC performance,” she said. “This is largely because of the technology being in its infancy.”

Lackner says, “I would argue the challenge for direct air capture is not so much the scale, but the cost.”

The key, experts say, is driving down the cost to store or purchase captured CO2 to create a market. Currently, a metric ton of carbon dioxide sells for between $500 and $800. Carbon Engineering’s goal is to drive the price down below $100, which, Lacker notes, is more in line with — and possibly even cheaper than — what companies pay for CO2 used in fizzy drinks, fire extinguishers and beer making. 

Direct air capture is expected to become more affordable as the industry grows. But that growth cannot come soon enough, Guetre said.

“We need to go faster,” she said. “The world has less than eight years left in the in the carbon budget before we hit 1.5 degrees (warmer) at current emission levels.”

Making money

There is a range of potential revenue streams for DAC firms. 

In addition to selling captured carbon dioxide for reuse, they can sell certificates of carbon sequestration to companies from around the world. 

Some companies, including Microsoft and Airbus, already have agreed to pay for direct air capture to offset their future emissions. While this is voluntary today, there’s a possibility governments could someday require such offsets.

Lackner says government regulations requiring CO2 removal are needed. He considers direct air capture a form of “waste management.”

“I wouldn’t want to live in a society where I could simply dump my garbage on the street or dump the sewage into the gutter, which is what people used to do, and it needed regulatory frameworks of some sort or another to prevent that,” he said. “Right now, where I live, the municipal garbage is taken care of by a private company. And I paid for it. … And by the way, I have no choice saying no.”

Some companies also are helping to foot research and capital costs by investing in DAC — Microsoft, United Airlines, ExxonMobil, and Tesla and SpaceX CEO Elon Musk among them. 

In addition, there are a growing number of government incentives available. One federal tax credit pays $50 per metric ton of CO2 that is captured and stored permanently, and $35 per ton captured and put to use, such as for enhanced oil recovery — the practice of using pressured carbon dioxide to push the last bits of oil from wells.

In California, captured CO2 used to produce low-carbon transportation fuels could be eligible for the state’s Low Carbon Fuel Standard credit.

Since March 2020, the U.S. Department of Energy has made more than $60 million available on research and development to move the direct air capture industry forward. 

“We must deploy multiple approaches — such as emerging direct air capture technology — to address issues with difficult to decarbonize industries such as planes, ships, and farming equipment,” Energy Secretary Jennifer Granholm said in an October 2021 news release.

And the infrastructure law passed by Congress in August includes nearly $9 billion to support carbon capture and storage.

Guetre said governments are largely receptive to DAC today, but like with anything else involving climate change, the clock is ticking. 

“One of the challenges is that policymaking takes time, and we don’t have time,” she said. “But in terms of governance, understanding this new tool and wanting to add it to policies, we see people moving really quickly for a policymaking pace.”

Ozkan said a few barriers to improving DAC technology and growing the industry could be insufficient funding and a lack of public acceptance or political support.

Similar, but not the same

DAC isn’t the only mode of carbon capture growing in popularity. Carbon capture, utilization and storage, or CCUS, is a similar concept. But instead of removing CO2 from the atmosphere, it captures it at the source — think coal-fired power plants and ethanol plants.  

For example, Summit Carbon Solutions is one of two companies proposing to build pipelines across the Midwest carrying carbon dioxide captured from ethanol refineries to be buried underground.

Summit’s $4.5 billion pipeline would stretch across Iowa, Minnesota, Nebraska and the Dakotas. Thirty-one ethanol facilities have signed on. 

“We’re going to be removing 12 million metric tons of CO2 (a year) that would have otherwise been released to the atmosphere and contributed to the greenhouse gases that are already in the atmosphere,” said Chris Hill, Summit’s director of environmental and permitting. “That’s equivalent to taking 2.6 million cars off the road.” 

Summit is hoping to start construction next year and begin operations by mid-2024. 

Critics and skeptics

While environmental groups also want to clean up greenhouse gases, they are largely opposed to carbon capture.

The critics have been more vocal about CCUS than direct air capture because CCUS is more established (21 plants — some around since the 1970s and ‘80s — are in operation, capturing 40 million tons a year) and can involve long pipelines they believe pose safety and environmental risks. But environmental groups have one common beef with both: that they provide avenues for fossil fuel production to continue.

“It’s clear that fossil fuel production and extraction is an environmental injustice for those communities,” said John Noël, senior climate campaigner at Greenpeace USA. “And there is little room for continued production in the future.”

Noël also said he’s skeptical of carbon capture because it’s being boosted by investments from the fossil fuel industry. He also points to research that found carbon capture — both CCUS and DAC — reduces only a small fraction of carbon emissions. Another study found that direct air computer itself is energy intensive.

Just before the United Nations Climate Change Conference in Glasgow in November, more than 500 groups — mostly environmental organizations — wrote a letter to President Joe Biden and congressional leaders voicing their opposition to CCUS. Among their other arguments were that its infrastructure threatens communities because it could leak, leading to asphyxiation of humans and animals, and that underground storage could lead to contamination of drinking water and stimulation of seismic activity. 

“Carbon capture schemes are unnecessary, ineffective, exceptionally risky, and at odds with a just energy transition and the principles of environmental justice,” they wrote. 

Pipeline construction can also entail seizing land through eminent domain, prompting pushback from private landowners, including farmers.

Hill said tough questions should be asked about carbon capture, but he added, “The people that are making these claims haven’t done their homework.”

He said the pipelines and wells are highly regulated and any seismic activity would be detected well before it would be felt by the public. He also insisted the “net benefit is not subjective.” 

“It’s math and science, and it’s easy to calculate,” he said. “There’s no real debate there. And I don’t know what agenda is pushing those kinds of concepts, but it’s very short-sighted.”

As for eliminating fossil fuels, Hill said, “We can’t be so polarized that there’s only one possible solution and nothing else will work,” adding, “It has to be an all-above approach.”