For years there has been talk of capturing and storing the carbon dioxide generated by burning fossil fuels as one way to keep the planet from overheating. In fact, the United Nations' climate science body envisions somewhere between 350 to 1,200 gigatons of CO2 storage within the century to avoid the worst effects of climate change. 

But is it really happening? Yes and no.  

Carbon capture and storage, or CCS, is an effort to trap CO2 at what's called a point source. This might be a smokestack or at an ammonia factory — in other words, a single, concentrated spot where the planet-heating greenhouse gas is emitted.  

After being captured, it is compressed and transported, usually using pipelines or trains, before being stored geologically — in aquifers or old oil reservoirs, for example.  

CCS is related to, but distinct from, carbon dioxide removal (CDR), which involves pulling CO2 out of the atmosphere after it's already been emitted. That CO2 is often stored similarly to CCS, but uses very different technologies for capturing. 

"Given the legacy of emissions in the atmosphere, given where we are in terms of emissions reductions, we're going to need these approaches," said Wil Burns, co-director of the Institute for Carbon Removal Law & Policy at American University.  

"We just have to figure out how to use them thoughtfully and still keep our eye on the prize of decarbonizing." 

The technology works, but scaling is another matter 

The feasibility of CCS and CDR is a subject of much debate among scientists and climate campaigners.

Advocates for scaling up the technology as a key pillar of decarbonization say the main hurdle is getting more plants built, which would require government subsidies and policy intervention. 

Without governments putting a price on carbon or offering tax credits, experts say it's hard to imagine investors shelling out for these expensive commercial projects. Renewable energy, by contrast, has become so cheap over time that it's often commercially viable on its own. 

"It's ready to go, technologically. We know how to do this process," said Susan Hovorka, a geoscientist at the University of Texas-Austin, researching CCS since 1998. 

How CCS began 

CCS traces its roots back to the 1960s, when oil companies began piping natural CO2 into oil fields for enhanced oil recovery — that's where captured CO2 is injected into old oil fields to help push more oil out of the ground. It wasn't until 1996 that the first large-scale CCS project designed to reduce emissions went online in Norway. 

Progress since then has been slowly ramping up. In 2020, there were 26 operational commercial CCS facilities around the world. As of last summer, the number has nearly tripled. 

But others say the technology remains in its infancy, and our real-world capabilities lag far behind our technical knowhow. 

"What is not well-established and basically doesn't exist at scale is the commercial experience doing this," said Danny Cullenward, an economist at the University of Pennsylvania's Kleinman Center for Energy Policy. "And proving that it works; that it's easy, that it's cost-effective, that it can be deployed at large scale, that it works in lots of different places."

Researchers from the University of Texas-Austin recently revealedthat though small-scale pilot projects have been successful in injecting CO2 into the ground, many of the world's large-scale CCS initiatives are pumping far less into storage sites than promised. 

And they are not unlimited. While previous estimates put the Earth's CO2 storage capacity somewhere between 10,000 and 40,000 gigatons, a new study foundthe number is just about 1,460 gigatons, meaning most CCS-reliant climate scenarios would breach the planetary limit for storage over the next 250 years. 

Climate models bet heavy on new technology 

Starting this week, the European fertilizer giant Yara will open what it calls Europe's largest carbon capture project. It will harvest excess CO2 at its factory in Sluiskil Netherlands, liquefy it, and ship it to Norway's Atlantic coast to be stored in an underground rock formation, some 2,600 meters below the seabed.  

That plant will only be able to capture 800,000 metric tons of CO2 annually. To meet that 350 gigaton threshold — the lower end of the UN's climate scenarios used to inform climate policy — would require about 5,800 more Yara-size plants to open tomorrow. 

The International Energy Agency, another intergovernmental body that models climate data, projected7.6 gigatons of carbon will be captured every year by 2050, with almost all of it stored. Right now, the world's 77 operating plants are capable of capturing 64 million tons annually. That output would need to be multiplied by 119 over the next quarter-century to reach the IEA number. 

"The scale of what's being called for in those scenarios is astronomically beyond any real activity that exists today," Cullenward said. 

He says climate models tend to underestimate renewables and lean too hard on  "gee-whiz" technologies.  

That's because models basically have three ways to hit an ambitious climate target: add more renewables, use less energy, or bet on some new technology that solves the problem without forcing society to change much. 

"If you tell a model to solve an impossible problem, it's like pouring water down a flight of stairs — it's going to find the fastest way to get to the bottom," Cullenward said.  

A license to keep drilling? 

One of the most contentious arguments about CCS is whether it represents a legitimate decarbonization solution or is a tactic from oil and gas companies to justify and prolong more fossil fuel extraction. 

In 2023, about 80% of the world's CCS capacity was used for enhanced oil recovery, according to research and advocacy group, Oil Change International — ultimately increasing emissions and defeating CCS's climate benefit.  

Some researchers also argue that CCS poses a moral hazard, or a situation where having a form of protection allows for more risk-taking. 

On the other hand, advocates for the technology often talk of reserving CCS for what's called "hard-to-abate" industries, like cement. 

"I don't think we're going to get to five or 10 or 20 gigatons a year of carbon removal," Cullenward said. "But we may need to get as much as we can and to me that's a reason to be more engaged rather than less engaged."

Edited by: Tamsin Walker