article Episode 1.2

Negative Emissions Technologies: A Solution or a Distraction?

Climate Now’s recent series on Carbon Dioxide Removal examined the cost and capability of different Negative Emissions Technologies (NETs) to sequester carbon. In this Systems Thinking article we examine the needs for, and pitfalls of, natural and man-made carbon sequestration solutions.

Reading Time: 10 mins

Date: 05.09.2022

Written By:

Emily Pope
Science Writer


Emily Pope

Science Writer

Emily Pope is a science writer for Climate Now. She received her PhD from Stanford University in Geological and Environmental Sciences. She has conducted research on the evolution of Earth’s atmosphere and hydrosphere, the optimization potential of energy from geothermal systems, and natural analogs for geologic carbon sequestration. Everyone has a stake in how we choose to address climate change. Thus, Emily is excited to develop content for Climate Now that makes the relevant scientific data, technological advances, and economic and political impacts clear and accessible.

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Premium Newsletter No. 02

Negative Emissions Technologies

“Reaching net zero will be virtually impossible without CCUS [Carbon Capture, Utilization and Storage].” – International Energy Agency

“CCS [Carbon Capture and Storage] is life support for the fossil fuel industry – and a death sentence for the planet.” – Nikki Reisch, Center for International Environmental Law

When the bathtub is overflowing, what do you do first?  Turn off the water, or get a mop? Ideally, of course, you have enough helping hands that you do both. But when you are under-resourced, you have to prioritize. And with only a decade remaining to prevent the most disastrous effects of climate change, we need to quickly develop the solutions that are most likely to limit global warming to 1.5 degrees Celsius. 

According to the 2018 IPCC 1.5C Special Report, those solutions include low-carbon energy technologies, energy efficiency, and carbon dioxide removal (CDR) strategies, which include Negative Emissions Technologies (NETs). NETs trap CO2 from the atmosphere and store it somewhere (trees, soil, minerals, underground, the ocean), essentially mopping up our overflowing emissions (see Video 1.7: Carbon Dioxide Removal).

Governments of the largest-emitting nations and companies that have made aggressive decarbonization commitments are embracing NETs as an element of their net-zero plans. The Microsoft Innovation Fund just invested millions into a start-up that traps atmospheric carbon dioxide in limestone. Elon Musk’s philanthropic Musk Foundation is funding a $100 million USD global competition to find novel carbon dioxide removal strategies. And, with the recently passed Infrastructure Bill in the U.S., federal funding for Carbon Capture and Storage (aka Carbon Capture and Sequestration, aka CCS) has reached $12 billion USD annually

But many climate activists argue that these are misdirected investments: why mop up the floor while the bathtub is still overflowing? The proliferation of questionable (or in some cases demonstrably fraudulent) carbon dioxide removal credits that can be purchased in compliance and voluntary carbon markets (Episode 29) to allow companies to greenwash their image, has added fuel to the argument that NETs allow companies to continue a business-as-usual approach when they need to be investing in decarbonization instead. In a July 2021 open letter, 500 climate activist organizations opposed government support for CCS in particular, arguing that it is an unproven, ineffective and “false solution,” that provides a cover for polluting companies to continue polluting.

However, the latest IPCC report, in chorus with a majority of climate scientists, argues that NETs – including CCS technologies – need to be a significant part of the global decarbonization strategy in order to reach net-zero by 2050, and we are right to be investing now. In this installment of Systems Thinking, we are going to take a close look at NETs, and CCS in particular: why are so many groups opposed to NETs while climate scientists (and economists) say we need them? What isn’t working with NET implementation so far, and how do we get on track today to ensure we will have the kind of CO2 mop we need once we’ve turned off the faucet?


Who says we need to be mopping, and why?

“There’s just too much CO2 in the air… When we run [the] models, even with really aggressive reduction in emissions, getting rid of all fossil fuels, replacing them with renewables, being as efficient as possible, getting rid of as many of the other kinds of emissions as we can, what we discover is we don’t come close [to reaching a 1.5 degree C target].” – Dr. Roger Aines, Lawrence Livermore National Lab, Episode 18

The climate case for NETs

In 2019, the National Academy of Sciences, Engineering and Medicine released a report stating that by mid-century, at least 10 gigatonnes of CO2 (Gt CO2) would have to be sequestered annually to stay on a 2 degree C warming path, more to stay under 1.5 degrees C. By the end of the century, up to 20 Gt CO2 would need to be sequestered annually. Their study comprised a meta-analysis of several research papers that developed integrated assessment models, which are least-cost economic models for different pathways to reach net-zero. The median sequestration needs of those models, which met the criteria for staying below 2 degrees C warming, was the source of that 10 Gt CO2/yr by 2050 number.

Since then, the NAS summary report has been used as a standard bearer reference across academic discussions (cited more than 260 times, including here at Climate Now, listen to Episode 18 for more) for why we need to be looking at NETs as part of our decarbonization portfolio. The latest IPCC report, published in 2022, presents a new meta-analysis of over 1200 proposed global pathway scenarios.  Of the pathways that are projected to limit warming to 2 degrees C or less, more than 95% require at least 200 Gt of CO2 removal by 2100 (~2.5 Gt CO2 annually). The median estimate for how much we need to sequester over the remainder of this century is ~625 Gt CO2, or about 9 Gt CO2/yr by the mid 2050’s and about 14 Gt/yr by 2100 (Figure 1) – pretty close to the estimate from the National Academy. In this median pathway from the IPCC, NETs that fall in the category of nature-based solutions (NBS), like reforestation or improved agricultural practices, are not able to absorb enough CO2 on their own, warranting the use of CCS (yellow and orange zones in Figure 1).


Figure 1. Examples of Integrated Assessment Models from the 2018 IPCC report. The figure on the left is a compilation of all decarbonization pathways assessed for the report that would result in a temperature rise ≤1.5 degrees C from pre-industrial levels. Any pathway showing negative annual global CO2 emissions is utilizing some amount of NETs. The figure on the right shows the CO2 emission sources and sinks for a representative pathway. NETs are shown in the yellow, orange and brown colors contributing to net emissions. According to this pathway, about ~5 Gt CO2 removal/year can be accomplished with improved agriculture, forestry and land practices (AFOLU, brown), although they are currently a source of emissions. Any pathways requiring additional CO2 removal will need technological solutions like CCS (yellow and orange).


In another recent analysis, the International Energy Association’s 2021 proposed pathway to net zero by 2050 (Figure 2) involves rapidly transitioning the grid to renewable energy and increasing energy efficiency (at a rate that is 3x the average of the last 2 decades), along with increasing hydrogen use and electrification, particularly between 2030 and 2050. This pathway also relies on increased implementation of nuclear energy (“other fuel shifts”) and widespread behavioral changes (like consuming less meat), strategies that so far, have faced stiff resistance. Even with all of these ambitious adaptations, the IEA projects around 8 Gt of carbon dioxide removal using carbon capture utilization and storage (CCUS) will be necessary. 


Figure 2. IEA Net Zero by 2050 roadmap (2021) showing emissions (Activity), reduced emissions from behavior change, energy efficiency, hydrogen use, electrification, bioenergy, wind and solar, and other fuel shifts, and carbon capture, utilization, and storage (CCUS), over time, leading us to a net-zero 2050.


The invocation of CCUS in this analysis means that the IEA also predicts nature-based solutions (NBS) will not be sufficient to meet our global negative emissions need. That is because CO2 capture and storage potential of NBS techniques is limited (see Figure 3). According to the NAS summary report on NETs, reforestation, afforestation and better forest management could sequester up to 3.5 Gt of carbon dioxide per year. Soil has the potential to absorb around 5.5 Gt of carbon dioxide per year. Only at their maximum storage potentials could soil and forests sequester the 9 Gt of carbon dioxide necessary to limit warming to 1.5 degrees C.


Figure 3. Graphic based on the National Academies of Sciences summary report of NETs, showing the sequestration potential and cost, of different carbon dioxide removal methods.


But what if those integrated assessment models are wrong?  

A 2021 Working Paper from Oxford University suggested that historically, the integrated assessment models used to produce global pathway scenarios – like those used in the National Academy and IPCC reports – have repeatedly underestimated deployment rates for renewable energy technologies, and overestimated their cost. The authors of the report, including Oxford Professor Dr. Doyne Farmer, who sat down with Climate Now to discuss the research (Episode 56), estimate that given the observed exponential increase in deployment of renewable energy technologies (solar, wind, batteries and hydrogen), the global energy system could reach “near-net-zero” in 25 years. If the remaining CO2 could be mopped up with nature-based NETs like improved forestry and agricultural practices that secure CO2 in vegetation (Episode 20) or soils (Episode 53), then would technology-based NETs like CCS become obsolete before they are even implemented at scale? Maybe. But decarbonization pathways involve a lot of moving, integrated parts. Either all of them have to perform at or above their expected level, or redundancy needs to be built into the plan. In addition, in order to expand renewable energy to the extent needed, there will need to be grid expansions as well, and policies will need to enable these changes. Some policies restrict the expansion of renewable energy, despite the fact that it may be cheaper.

The economic case for NETs

“Whether or not it makes economic sense is up to us. We decide that.” – Dr. Julio Friedmann, Columbia University, Episode 17

In 2020, renewables became the cheapest source of energy on a global scale, meaning that in a free-market economy, fossil fuel-sourced electricity should phase out on its own. But global averages are not local averages, and there are places and economic sectors that aren’t going to be able to use renewables to quickly and cheaply decarbonize. Countries and regions wealthy in fossil fuels (China, Canada) and poor in wind (U.S. Southeast) or sun (Canada, Russia) are not going to be driven by market impulses to switch to renewable energy soon enough. And societal behaviors complicate market dynamics. Americans love their cars (Episode 47). Coal is part of China’s national identity and a source of economic security in uncertain times (Episode 19). Even regions where renewables are the best option will still need time to decommission existing power plants and invest in building an electrical grid and storage system that can support the supply and demand. That might be attainable in the next decade in wealthy nations, but how quickly can we build reliable national electrical grid systems in developing nations that have never had them before?

Does that mean we should place a CO2 scrubber on each coal-fired power plant in these regions instead? Certainly not, if it costs more than building out that electrical grid. But low-cost NETs, like reforestation or improved land management practices, could be enacted alongside an electrical grid build-out. And investing in the R&D necessary to reduce the cost of direct air capture technologies (Video 2.5: CCS Part 1), or test the feasibility of low cost ocean carbon dioxide removal solutions (Episode 38), gives us a back-up plan for the (pretty likely) scenario that our global energy economy doesn’t pivot fast enough.

Carbon capture and storage has its place, too, especially if we are not keen to give up eating meat, or stop using plastics, fertilizers, cement and steel any time soon. Collectively, these sectors are producing over 15 Gt CO2 each year, and none of them have a low-cost path to decarbonization (Episode 60). In these sectors, “common-sense” solutions to decarbonization involve more than just the bottom line. People, and their livelihoods are involved, too. It is entirely possible to reduce the carbon intensity of steel production by transitioning to renewable energy-sourced electricity, but to make that cost-effective could require moving the steel mill to where that renewable energy is the cheapest. Even if there is enough of a financial benefit to strand the existing coal-fueled steelmaking infrastructure in Pennsylvania and build again next to the windmills in Iowa, what are the impacts of stranding the workforce? Or the community that is built around it? Steel town populations are in the tens of thousands, and these communities are rightly threatened by the prospect of redistributing their core industry. In cases such as these, the cheapest option is not always the best option.

Arguments have been made that CCS projects “delay the needed transition away from fossil fuels” by allowing polluting facilities to continue to use fossil fuels instead of transitioning to alternative forms of energy. As a result, polluting facilities cause continued air quality damage (even with CCS) to local communities. However, without CCS, and without an incentive for these companies to stop using fossil fuels, they would continue to pollute.


Are CCS projects working?

Of all NETs, carbon capture and storage is the most expensive – costing about $40 USD to thousands of dollars (in the case of direct air capture) to capture, transport and bury the CO2 (Videos 2.5 and 2.6). A flurry of high-profile articles in the last two years have called the effectiveness of carbon capture into question. A report from Stanford University headlined “The health and climate impacts of carbon capture and direct air capture,” drew attention to carbon capture projects that were reducing CO2 emissions by only 11%. Watchdog group Global Witness published a report on the Shell-owned carbon capture plant, stating the “massive carbon capture facility in Canada emits far more than it captures.” And many have noted that after $1.1 billion in DOE investments from 2009-2018, there are only 3 working CCS projects in the US: one capturing carbon from a coal power plant, and two projects capturing industrial emissions. After being plagued with technical problems, the coal-with-CCS project shut down indefinitely in May 2020, when the price of oil dropped so low that the CO2 couldn’t be economically sold for enhanced oil recovery, the primary source of revenue for CCS projects (Episode 46). (Enhanced oil recovery, or EOR is the process of putting CO2 back underground to help push up more oil.)

It is reports like these that give weight to opponents of CCS development. But, if you look past the headlines of these stories, the devil is in the details. The carbon capture projects that the Stanford study focused on were limited to carbon capture and utilization (CCU), not carbon capture and storage. CCU projects use captured CO2. That is, they sell it as a product – to food and beverage industries, agriculture, and – mostly – to the oil and gas industry to be used for enhanced oil recovery. Nascent CCU applications also include developing biofuels, hydrogen, chemicals and building materials. But the many of these projects will release the CO2 into the atmosphere after use, such that for the most part, CCU is not actually a negative emission technology. It is simply recycling the CO2 so that more emissions are not produced. In reference to the second headline, the carbon capture facility in Canada from the Global Witness report is not emitting more than it is trapping as the report suggests. It is trapping ~40% of the emissions that would otherwise be released into the atmosphere at that plant, which is consistent with the scale of carbon capture that facility was designed to do.

When it comes to the low success rate of DOE CCS projects – the department was hobbled by requirements from the research grant source. Most of the project funding came from the Clean Coal Power Initiative, a cost-shared collaboration between the federal government and industry to develop low-emission coal technologies. This only allowed the DOE to fund CCS projects that were related to coal and certain types of chemical industries. 8 of the 11 DOE-funded projects were coal power plants, which are among the most expensive applications of point source carbon capture (Video 2.5). The projects did not fail on the grounds of technological limitations. They could sequester CO2. They were simply not economical, even with support from the DOE grants. And that gets to the heart of why CCS – and other NETs – are still only sequestering a fraction of a percent of our annual emissions. If there was more of a financial incentive to capture and sequester carbon, it would become economical.


How do you pay for an industry with no product?

“Firms that emit CO2 when they produce things like gasoline through refining, or steel through some production process, do not have an incentive to adopt these carbon capture technologies … in the absence of some kind of external incentive, like a price on carbon emissions.” – Dr. Sheila Olmstead, University of Texas, Austin, Episode 46

When it comes to negative emissions technologies, there is no technical challenge preventing this from working (Episode 17). Growing more trees will absorb more CO2 (Episode 20). No-till agriculture will increase the carbon storage of soils (Episode 53). We can use reactors to chemically bind CO2 into mineral structures (Episode 31). And we have had scrubbers that can remove more than 90% of CO2 from smokestack emissions since the 1970’s (Episode 8). But carbon capture in particular and other negative emissions technologies where the sole aim of the technology is removal of atmospheric carbon dioxide, present a distinct economic challenge in comparison to development of other green technologies, like renewable energy or electric cars. Those technologies produce a product for which there is consumer demand. Subsidizing them early on until they found their footing, and then letting the market drive their further development made sense. But when the aim is to bury CO2 where it can’t escape, there is nothing for consumers to consume, which puts this type of technology firmly in the utilities category, not the marketplace. Carbon capture and storage technologies are providing a public good. They are the sewage systems that regulate our atmosphere rather than our drinking water. And ultimately, like any public good – whether regulated by the private sector or the government, this will be paid for by the public.

If a carbon tax were introduced, companies would find the least-cost method to decarbonize. In some, but not all, cases that could be through CCS or through a (hopefully well-regulated and working) carbon marketplace employing a variety of NETs. But regardless of the pathway, those companies will pass the costs of decarbonization onto the consumer. If governments choose to subsidize clean technologies through policies like the 45Q tax rebate for CCS, then costs are covered by taxpayer dollars coming from the consumer.

It is certainly reasonable to debate which of those avenues is more fair, and will impact the highest-risk members of our communities the least. And of course, both sides have been lobbying to pass the buck – businesses don’t want to hike up prices and lose customers any more than politicians want to increase taxes and lose voters (Episode 30). But the reality is that we will pay for this CO2 sooner or later – either by investing in these technologies now, or suffering the trillions of dollars in damages that will occur when we do nothing (Episode 5).


Conclusion: we need the mop.

Rather than a distraction from the hard work of reducing our emissions through renewables and increased efficiency, making everyone pay to clean up the CO2 we are putting in the atmosphere might just be the wake up call needed to ramp up our efficiency, embrace behavioral change, build the renewable electricity grid, and decarbonize as fast as we can.

At the end of the day, we need to do as much as we can to reduce emissions by transitioning to renewables, building out the grid, increasing efficiency, and electrifying everything, and what’s left over, we should be prepared to mop up with NETs, including CCS.


Update: January 2023.

Since the publishing of this article, the U.S. Inflation Reduction Act has been enacted into law, providing an enlarged federal incentive program for Negative Emissions Technologies, particularly CCUS. To learn more about the Inflation Reduction Act, listen to our interview with Dr. Jesse Jenkins of Princeton University, who led an independent impact analysis of the bill before its passage (Episode 68).

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