Reduce, recycle, remove: what waste management can teach us about controlling carbon emissions

Each year, the world produces around ten billion tons of trash. A significant portion of this trash ends up as litter, polluting our cities, water, and ecosystems, and resulting in significant costs to the environment and society. In response, society deploys a three-pronged strategy to fight litter: 1) reduce waste production, 2) recycle as much of the remaining waste as possible, and 3) remove the rest in sealed landfills that protect the environment from the consequences of this pollution.

 Each year, the world produces over 10 billion tons of waste.  Photo credit:  "Landfill face" by Ashley Felton - Own work. Licensed under Public Domain via Commons

Each year, the world produces over 10 billion tons of waste. Photo credit: "Landfill face" by Ashley Felton - Own work. Licensed under Public Domain via Commons

In recent decades, the same forces fighting pollution from litter have become increasingly aware of a new type of “litter:” carbon dioxide. When emitted into the air at the quantities humans produce—over 35 billion tons annually (over 3x our trash production)—carbon dioxide traps heat that would otherwise escape from the planet’s surface, in turn causing climate change. And much like the solid litter we are familiar with today, carbon dioxide litter can remain in the atmosphere for centuries (or longer) if left to natural cleanup processes.  

The good news in regards to the “carbon litter” problem facing society today is that the same reduce-recycle-remove framework that we apply to waste litter can also guide our action in regards to carbon dioxide. For one, the best way to reduce carbon litter is to not make it at all, through conservation/efficiency measures and the adoption of zero-carbon-emitting fuels. For the carbon litter that we don’t avoid, we can recycle into fuels, chemicals, and plastics (among other products). And for all of the rest, we can “landfill”—underground in geologic formations; above ground in soils, biomass, and ecosystems; and/or even potentially the ocean.

But while the reduce-recycle-cleanup framework is not controversial among supporters of the quest to end litter, this framework has surprisingly had its opponents in the climate change conversation. In particular, the idea of “landfilling” carbon dioxide (especially in underground geologic formations), has faced resistance from some in the environmental community.

What makes this opposition most strange is that the arguments from these environmental opponents to cleaning up carbon dioxide from the atmosphere contradict their arguments in support of cleaning up litter. For example, environmental groups have argued that developing carbon landfills will encourage industry to skip the “reduce” and “recycle” steps. The same is not said for litter. Take, for example, the really exciting projects to clean up litter that has accumulated in our oceans. This project is lauded by environmental groups, not opposed on the grounds that it will encourage further pollution.

 Projects like this one to clean up litter from the ocean aren't opposed on the grounds that they will encourage more litter to be dumped into the ocean--instead they are lauded on the grounds that they remedy an environmental problem. The same argument can be made for efforts to clean up carbon that has accumulated in the air. Photo credit:

Projects like this one to clean up litter from the ocean aren't opposed on the grounds that they will encourage more litter to be dumped into the ocean--instead they are lauded on the grounds that they remedy an environmental problem. The same argument can be made for efforts to clean up carbon that has accumulated in the air. Photo credit:

In addition, some environmental groups cite fears that carbon landfills will cost too much to deploy, so it isn’t worth spending scarce resources on doing so. But imagine if we were faced with the same situation that we are with carbon dioxide in regards to litter (i.e. that we had let 800 billion tons of trash accumulate in our ecosystems since the Industrial Revolution, much like we have with carbon dioxide in the atmosphere). If it was “too expensive” to cleanup this trash, environmental groups would likely be clamoring for investments in science, technology, policy, and markets for landfills—not saying that the problem is un-fixable so we should focus only on proven technology to reduce the amount of new litter. 

In fact, carbon dioxide cleanup is likely to be a big business in the future—the global market for waste is estimated at around $400B* annually, after all—as well as a clear environmental priority. And that's exactly why it is critical that we invest in efforts to unlock that potential today by support innovative efforts to build the carbon landfills of the future, so we can reduce, recycle, and remove in regards to carbon dioxide as well.


*At a $400B in annual revenue and 10B tons of total waste per year, the average cost of waste cleanup is around $40/ton of waste -- incidentally the same figure as the social cost of carbon dioxide as estimated by the US Federal Government (Social Cost of Carbon = $40/ton CO2 in 2015 at average (3%) discount rate).

Companies pay for oil spills; why not "carbon dioxide spills"?

When oil (and oil-derivative fuels) burns, the combustion process creates carbon dioxide gas as a byproduct. The vast majority of the time, the carbon dioxide molecules that result from combustion "spill" into the air, where they contribute to climate change. And while the combustion of each tank of gasoline only spills a few pounds of carbon dioxide into the air, all of these small-scale carbon spills around the globe add up: the International Energy Agency estimated that humans emitted over 11 billion tons of carbon dioxide into the air in 2012 from oil-based products. As a comparison, the Deepwater Horizon oil spill disaster released approximately 1 million tons of crude oil into the Gulf of Mexico in 2010.

 Coal power plants like the one above "spill" billions of tons of carbon dioxide gas into the atmosphere each year. Even though this volume dwarfs the amount of oil spilled each year, our response to oil spills is much more aggressive than our response to carbon emissions. Image credit:  the Guardian

Coal power plants like the one above "spill" billions of tons of carbon dioxide gas into the atmosphere each year. Even though this volume dwarfs the amount of oil spilled each year, our response to oil spills is much more aggressive than our response to carbon emissions. Image credit: the Guardian

A comparison of society's response to oil spills and to carbon spills is quite revealing. On the one hand, take the BP oil spill mentioned above. In response to this disaster, government and private sector actors rapidly mobilized a clean-up effort to contain the damage of the oil spill as much as possible. And years later, BP agreed to pay tens of billions of dollars in fines for damages caused by the spill. On the other hand, consider our response to carbon dioxide spills into the atmosphere, which is essentially non-existent. In certain markets, some of the largest carbon emitters have to pay a small fee for spilling carbon into the air, but most of the parties around the globe that are responsible for carbon spills end up paying nothing. What's more, efforts by governments and/or private companies to clean up carbon spills have only recently begun ro develop.

The fact that society makes energy companies pay for oil spills but not carbon spills is strange in many regards. For one, the damages from carbon spills affect people and environments all around the world, not just the local areas contaminated by oil spills. Carbon spills also last much longer than oil spills if left to natural process for remediation. But most importantly, the scale of damages from climate change are likely to dwarf the economic and environmental costs of oil spills.

This isn't to say that oil spills are not awful disasters -- they are. This comparison just highlights how disproportionately weak our response for carbon spills is compared to our response to an analogous environmental disaster. 

There are a number of likely reasons that explain our weak response to carbon spills. For one, oil spills have immediate, highly visible impacts that motivate us to clean them up quickly; carbon spills are invisible when they happen, and their impacts are only felt decades in the future. What's more, we have tools to clean up oil spills, so we actually can clean them up (at least to a certain degree) when we set out to do so -- as of now, solutions that can clean up carbon spills from the air are just beginning to reach commercial scale.

 This is what an oil spill looks like. In contrast, even the biggest "carbon spills" are invisible and odorless, with their damages happening years after the initial spill. Image credit:  Wikipedia

This is what an oil spill looks like. In contrast, even the biggest "carbon spills" are invisible and odorless, with their damages happening years after the initial spill. Image credit: Wikipedia

But the fact that carbon spills present a much more difficult problem than oil spills makes it all the more urgent we stop making carbon spills and start developing and deploying solutions to clean up the spills of past decades. When companies have solutions both to prevent and then clean up carbon spills, we can start seriously discussing why we don't hold them accountable for doing everything they can to avoid and remediate carbon spills in the same way we do with oil spills.

Open letter to Tim Flannery in response to "A 'Third Way' to Fight Climate Change"

The New York Times recently published an op-ed by Tim Flannery on carbon removal solutions to climate change. I commend Mr. Flannery for writing about such an important topic, but I think his article could have benefited from framing carbon removal solutions as a missing piece of the climate change mitigation portfolio, rather than as a “third way” for fighting climate change. Below is my more detailed response to Mr. Flannery’s op-ed, written as an open letter:


Mr. Flannery-

First and foremost, thank you for writing about this important idea of removing excess carbon dioxide from the atmosphere. I, along with an increasing number of climate experts, agree with you that cleaning up carbon dioxide that has accumulated in the atmosphere will prove critical for curtailing climate change, and that it is essential to accelerate the development of carbon removal solutions today. However, I think that your framing of carbon removal as a “third way” for curtailing climate change threatens to mislead key stakeholders about the appropriate role of carbon removal solutions in mitigating climate change, in turn jeopardizing the ability of carbon removal solutions to gain the support they need to flourish.

In particular, I think that the strawman of carbon removal as a “third way” – between one option of greenhouse gas (GHG) emission mitigation and another option of solar geoengineering – can mislead key stakeholders in two important ways. First, this framing draws unfounded distinctions between GHG emissions abatement and carbon removal approaches, and risks painting carbon removal as an alternative to GHG emission abatement instead of the complement that it is. And second, this framing elevates the idea of solar geoengineering as a viable climate change abatement strategy vastly above the current scientific consensus on this topic, painting carbon removal solutions in a much more radical light than do most climate experts.

Point #1: Carbon removal is climate change mitigation.

The IPCC defines “mitigation” as “an anthropogenic intervention to reduce the sources or enhance the sinks of greenhouse gases” [emphasis mine]. In other words, carbon removal is mitigation. What’s more, strategies to enhance carbon sinks are almost identical to related GHG emission abatement strategies. Take the following examples:

  • Avoided deforestation (reduce GHG emissions) and reforestation (enhance GHG sinks)
  • Fossil energy with carbon capture and storage (reduce GHG emissions) and bioenergy with carbon capture and sequestration (reduce GHG emissions and enhance GHG sinks) or direct air capture and sequestration (enhance GHG sinks)

The above examples also make it clear that carbon removal solutions are a complement – not an alternative – to GHG emission reduction strategies. Framing carbon removal as a “third way” risks even further “neglect[ of carbon removal] in political negotiations and public debate,” (as you write in the article) as policymakers might see carbon removal as a distraction to prolong business-as-usual production of GHG emissions, which it clearly is not.

Point #2: Solar geoengineering approaches provide far too radical of an anchor of comparison for carbon removal solutions.

Climate experts see solar geoengineering in a completely different light than they do climate mitigation strategies. Take the following table from the National Research Council report on “Climate Interventions”:

 Source: National Research Council, Climate Intervention reports.

Source: National Research Council, Climate Intervention reports.

Solar geoengineering is simply in a different class of climate change abatement approaches – more extreme, risky, and controversial. As a result, I have found that there is comparatively little discussion about implementing solar geoengineering proposals today: anecdotally, I would estimate that for every conversation on solar geoengineering, there are 100 conversations on mitigation approaches. As a result, framing carbon removal as a “third way” between GHG emission reductions and solar geoengineering makes carbon removal appear to be an option in the middle of these approaches, when it is in fact much closer to the mitigation activities that act as the center of gravity in the climate conversation. As an analogy, doctors do not explain exercise as a “third way” to diet and lap-band surgery to prevent weight gain, much like climate experts do not explain carbon removal as a “third way” between GHG emission mitigation and solar geoengineering to prevent a warming planet.


In conclusion, I suggest moving away from the framework of carbon removal as a “third way” and instead framing carbon removal as a critical yet largely missing piece of “Plan A” to deploy large-scale climate change mitigation strategies. Framed as a way to broaden the set of mitigation solutions, I think the conversation on carbon removal can help bring more parties to the climate negotiation table and can encourage deeper emission reduction pledges than would otherwise occur. Carbon removal solutions still face serious hurdles to reach the necessary scale to realize this promise, making it all the more critical that we explain carbon removal in as constructive and appropriate way to ensure we address these barriers effectively and swiftly.

Again, when it comes to the need for accelerating the development of carbon removal solutions, I suspect that we are in complete alignment. I write this letter in that spirit of support for this field, and I hope that I have not misrepresented any of your claims or otherwise portrayed them inappropriately. I also stand ready to be disabused of any misconceptions I have about your argument, and to be challenged on any/all of the points of contention listed above.     

Thank you again for writing about this important topic,

Noah Deich

Executive Director | The Center for Carbon Removal

Talking to kids about climate change doesn't have to be difficult. Carbon removal can help.

ThinkProgress recently posted an interesting piece on how to talk to children about climate change. The article had a number of interesting insights, and revealed just how challenging it can be for parents to teach their children about climate change. Missing from the article, however, was any mention of carbon removal -- an omission that makes climate change even more difficult to understand. This post explains why carbon removal is so important for communicating the need for climate action in a way that resonates with children and adults alike. 

As background, the term "carbon removal" is used to describe any process or system capable of cleaning the air of excess carbon dioxide -- the most prevalent of the "greenhouse gases" causing climate change. Scientists also use the term "negative emissions" for such carbon removal solutions, as they work like carbon emission source run in reverse. 

Including the idea of carbon removal enables us to explain climate change in as simple a way as possible: climate change is caused by the giant (albeit invisible) mess humans are making in the sky by emitting carbon dioxide and other greenhouse gasses. 

Climate change is caused by the giant (albeit invisible) mess humans are making in the sky

To curtail climate change, we need to clean up this mess, both by stopping the emissions that are causing the problem, and by cleaning up the emissions already in the atmosphere (through carbon removal).  

 Climate change is mess -- an idea quite familiar to children. Simply stopping making a mess worse isn't acceptable, we also have to clean up the mess that we've made.  Photo credit:

Climate change is mess -- an idea quite familiar to children. Simply stopping making a mess worse isn't acceptable, we also have to clean up the mess that we've made.

Photo credit:

Without talking about carbon removal, however, we can't explain climate change as a clean-up problem -- we can only describe it as a stop-making-a-mess-problem. Very rarely is it acceptable to simply stop making a mess while not cleaning up the one we've made -- even kids get this idea. As a result, the conversation on climate change rarely talks about climate change as the mess that it is; instead, this conversation tends to devolve into the abstractions around future damages and the pursuit of sustainable lifestyles, complicating our understanding of the climate challenge.

So let's start making it explicit that excess carbon emissions in the atmosphere have created a big mess, and that it's critical both to stop making the mess worse and to start cleaning it up. This framing enables us to communicate what actions add to this mess, and what actions -- like deploying carbon removal solutions -- help clean this mess up. 

What climate scientists talk about when they talk about carbon removal

Last week, around 2,000 climate experts gathered at the Our Common Future Under Climate Change Conference hosted by a consortium of NGOs in advance of the upcoming UN COP21 climate negotiations. The idea of removing carbon dioxide from the atmosphere to create “negative emissions” was a hot topic of conversation at the Conference. Below, I’ve summarized my key takeaways about what scientists were saying about carbon removal at the Conference:

 Discussion on the main stage at the Our Common Future Under Climate Change Conference.

Discussion on the main stage at the Our Common Future Under Climate Change Conference.

Takeaway 1: Carbon removal is increasingly embedded in projections of what we will need to do in order to curtail climate change. The consensus documents from the conference state: “to limit warming to 2°C, emissions must be zero or even negative by the end of the 21st century.” Carbon removal solutions will be necessary to transform the economy to generate negative emissions, as more traditional climate mitigation strategies (such as renewable energy, energy efficiency, avoided deforestation, etc.) can only get us to zero emissions – not below zero. And it’s not just "below zero" emissions that we need carbon removal for, as carbon removal solutions also make up a significant component of many pathways for reducing greenhouse gas emissions by 40-70% by mid-century.

Takeaway 2: But…scientists still have many untested assumptions about deploying large-scale carbon removal projects. Today, carbon removal solutions have not been deployed at large scale. As a result, projections of large-scale carbon removal deployments rely on many untested assumptions (around cost, sustainability, scalability, etc.). For example, many projections that include carbon removal solutions involve the large-scale deployment of bioenergy systems, yet critical uncertainties remain around our estimates of:

  • The sustainable supply of bioenergy crops;
  • The ability for bioenergy crops to co-exist with growing demand for food; and
  • Public acceptance about underground carbon sequestration

The scientists working on carbon removal systems are the first to admit these limitations in their models. But unless these assumptions are stress-tested promptly, we risk setting climate policy in a direction that may end up ultimately infeasible and/or unsustainable.

Takeaway 3: Scientists are focusing on a narrow set of carbon removal solutions today. Most of the talk about carbon removal at the conference focused on bioenergy coupled with carbon capture and storage (BECCS, as it is referred to in the scientific community) and forestry solutions (such as reforesting degraded lands or planting new forests altogether). But innovators are also working on other carbon removal methods: direct air capture systems, agricultural techniques with the potential to sequester carbon in soils, and mining techniques that use minerals to sequester carbon directly from the atmosphere, for example. While these latter techniques might have even more uncertainties surrounding them than do bioenergy/forestry approaches, many scientists still think that it is worthwhile conducting further research on these systems to learn how they might broaden the portfolio of feasible, sustainable, and scalable carbon removal solutions in the future.

Takeaway 4: The scientific conversation on carbon removal is an implicit call for increased R&D for carbon removal solutions.

 Carbon removal is the elephant in the room for the climate change conversation: scientists are increasingly convinced we need carbon removal solutions, yet significant uncertainties remain as to what carbon removal solutions can scale in a sustainable, cost-effective way.

Carbon removal is the elephant in the room for the climate change conversation: scientists are increasingly convinced we need carbon removal solutions, yet significant uncertainties remain as to what carbon removal solutions can scale in a sustainable, cost-effective way.

In many regards, carbon removal is the elephant in the room in today’s climate change conversation. While scientists increasingly assume that carbon removal solutions will provide a critical component in the fight against climate change, they are quick to acknowledge that we aren’t researching and building carbon removal projects nearly as fast as needed to ensure we actually can remove carbon from the atmosphere at the scale needed. Implicit in this conversation is the need for more research and development across a full portfolio of carbon removal solutions – something that is critical for policymakers and climate negotiators to make explicit as soon as possible.

We Are Family - Why Carbon Removal is a Mitigation Strategy

Carbon removal techniques, while important for fighting climate change, have faced resistance from some in the environmental community partly because they have been perceived as a threat to the deployment of other climate change mitigation techniques. Recently, these concerns have begun to fade from the debate, suggesting that the environmental community is more likely to support the emerging efforts to develop carbon removal solutions than in the past.


Throwing the Carbon Capture Baby out with the Coal Bath Water

The environmental advocacy group Greenpeace recently released a report lambasting carbon capture and storage (or "CCS") as "a false climate solution" that "[i]n no uncertain terms...hurts the climate." The Greenpeace analysis, however, made a number of assumptions that fit the conventional wisdom surrounding CCS, but when analyzed with greater scrutiny turn out to be deceptively misleading. Misleading Assumption 1: CCS requires that we prolong coal use. Can we have CCS without coal? From a technical point of view, of course. The California Energy Commission just held a workshop on natural gas power generation and CCS, a handful of companies and researchers are working on direct air capture systems that can pull carbon from ambient air, and researchers across the globe have begun thinking about carbon-negative bio-energy and CCS projects. It may be politically infeasible to start developing CCS on these non-coal resources, but a compromise could be to ensure that we phase out coal CCS in favor of non-coal CCS. Regardless, it's too early to say whether these non-coal (and even renewable!) CCS systems can play a large role in fighting climate change, because we simply have not done enough research and development to have good data on these systems. Throwing out renewable CCS today as the unrealistic dreams of "techno-optimists" is analogous to stopping the development of solar energy back in the 1970s because it was over 100 times more expensive than it is today.

(Update: presentations from CEC workshop on natural gas + CCS available here.)

Solar PV chart
Solar PV chart

Above: Data from Bloomberg New Energy Finance

Misleading Assumption 2: It is inevitable that CCS will lead to increased EOR. Can we do CCS without EOR? Yes. There are a number of demonstration plants across the world injecting CO2 underground that involve no EOR. If we don't want EOR, we simply need to regulate CCS so that it can be cost-effective without additional fuel production. Such a pathway will increase the cost of CCS, and there is a much more valid and nuanced debate than what the Greenpeace analysis provides on whether we should pursue EOR in combination with CCS that focuses on using EOR as a pathway to net-negative emissions. But if we wanted to assume that EOR was entirely undesirable, we could still have CCS -- it would just cost more than it would in conjunction with EOR.

Misleading Assumption 3: Underground storage of carbon is required for sequestration. Does carbon have to be stored underground? No. We can turn it into cement, plastics, or any number of other solid products. Will there be issues with storing large volumes of solid carbon above ground? Probably. But we can get around the geologic sequestration problem if we wanted to accomplish this goal.

So can CCS hurt the climate if done wrong? Certainly. But is Greenpeace justified in saying that "in no uncertain terms" CCS "hurts the environment?" Certainly not.

As a result, I remain unconvinced that we should throw out CCS as a climate solution today. Instead, environmental advocates should strive to make clear all of the potential pitfalls of CCS, and ensure that its development balances these environmental and social concerns with the economic considerations of the companies and regulators responsible for deploying these solutions. If you think coal is bad, fight coal. If you think EOR is bad, fight EOR. If you think geologic sequestration is bad, fight geologic sequestration. But we can make a world where coal, EOR, and geologic sequestration do not exist but where large-scale CCS still flourishes if we so choose. While this world might seem far from reality today, it might be the only world where we can prevent catastrophic climate change, as most renewable energy solutions (like wind, solar, geothermal, etc.) are not capable of generating the net-negative emissions we likely need to prevent climate change.

Carbon removal wedges
Carbon removal wedges

Above: adapted from the Climate Institute "Moving Below Zero" report 

So let's stop entangling CCS inappropriately with arguments against related energy systems, because we can decouple CCS from these system is we choose. If we keep conflating CCS with these other arguments, we risk throwing out the CCS baby with the coal bathwater.

How weight loss can put carbon removal in perspective

Six years ago, then U.S. Secretary of State Hillary Clinton compared climate change to weight loss:

"You know, oftentimes when you face such an overwhelming challenge as global climate change is, it can be somewhat daunting,"


"If we keep in mind the big goal, but we break it down into baby steps - those doable, achievable objectives - we can do so much together."

Clinton's analogy comparing fighting climate change to weight loss can be extended to help put carbon removal in context. In this analogy:

  • Conservation and mitigation: analogous to going on a diet. The no-brainer strategy for starting to lose weight is to eat fewer calories, just like the no-brainer strategy for preventing climate change is to reduce carbon emissions from activities such as burning fossil fuels, deforestation, and intensive industrial agriculture.
  • Removing carbon from the atmosphere: analogous to exercising. Sometimes diet alone isn't enough to lose weight, exercise is needed too. In the same way, simply stopping carbon emissions might not be enough to prevent climate change -- we might also need to remove excess carbon from the atmosphere and/or oceans. And even if we could prevent climate change without carbon removal, pursuing carbon removal strategies slowly and in moderation is likely to be beneficial regardless, much in the same way that moderate exercise is healthy regardless of whether it is necessary for weight loss.
  • Adapting to changes in the climate: analogous to buying new clothes. Buying new clothes does nothing to help you lose weight -- but it does make like more comfortable while you are overweight. No doctor has ever said, "it's OK to be obese -- you can adapt to this condition by planning what new clothes you should buy as you grow larger..." just like scientists largely agree that climate adaptation is no substitute for preventing climate change in the first place.
  • Albedo modification geoengineering techniques: analogous getting lap-band surgery. Lap-band surgery can have devastating side effects and so is only recommended in extreme circumstances. What's more, the procedure only works in conjunction with diet and exercise. In the same way, albedo modification geoengineering techniques are viewed as highly risky and uncertain, and require dramatic emission reductions and carbon removal for them to be phased out.

What "net-zero" emission targets means for the carbon removal field

The Carbon Brief recently published a fantastic article explaining the implications of “net zero” climate targets in the context of international climate negotiations. The Carbon Brief article does a great job of highlighting the fact that “negative emission technologies” – or carbon dioxide removal (“CDR”) approaches are critical for enabling the global economy to achieve a "net zero” commitment. The article goes on to note that, “however, there are clear limits to negative emissions and many options...remain unproven.”  The emphasis is mine, as I think this fact has enormous implications for preventing climate change.  Without proven, scalable, and sustainable CDR solutions, “net-zero” targets will prove highly challenging to meet: “net-zero emission” would become simply “zero emission” targets – certainly doable, but today looking far from certain from occurring.

A “net-zero” (let alone “below-zero”) target, then, risks being an empty goal if such targets are not accompanied by increased efforts to develop CDR technologies. A recent report on CDR from the National Academy of Sciences highlights that:

“If carbon removal technologies are to be viable, it is critical now to embark on a research program to lower the technical barriers to efficacy and affordability while remaining open to new ideas, approaches and synergies.”

The NAS study stops short of identifying details of what research is needed to develop scalable, sustainable, CDR solutions, and there is little talk in established science/technology R&D funding agencies about scaling up levels of CDR R&D. So as talk of “net zero” targets increase, so too must conversation about increased R&D funding for CDR in order to make such “net zero” targets credible.

Media coverage of carbon removal post-NAS report

In past several days, numerous media outlets have weighed in on the National Academy of Sciences ("NAS") report on "climate interventions" (including yours truly). The Carbon Brief does a great job of aggregating these responses, which reveal both positive and negative signs for future discourse on carbon dioxide removal ("CDR") -- i.e. removing and sequestering excess carbon from the atmosphere and oceans. The main negative sign is that many media outlets are still conflating CDR as “geoengineering” alongside Albedo Modification ("AM") – despite the fact that the NAS report specifically fought against this this confusion:

"Carbon Dioxide Removal and Albedo Modification (i.e., modification of the fraction of short-wavelength solar radiation reflected from Earth back into space) have traditionally been lumped together under the term “geoengineering” but are sufficiently different that they deserved to be discussed in separate volumes.”

For example, the review from the Guardian quotes Eli Kintisch from Science Magazine who describes both CDR and AM as “a bad idea whose time has come.”

The Union of Concerned Scientists response does a better job of separating CDR from AM in its coverage. But their coverage, which focuses on the conclusion that "carbon removal and sequestration are more costly than reducing emissions,” risks leaving their readers with the wrong impression that we shouldn't invest in developing CDR systems today. In fact, the NAS report highlights that it is very important to invest in developing CDR systems in addition to rapidly scaling up climate mitigation and adaptation solutions (given the importance of viable, sustainable, CDR options in the event we do not decarbonize as quickly as necessary to prevent climate change). CDR solutions are in a similar state of development as solar energy solutions were in the 1970s -- concluding that such 1970's solar projects were "expensive" misses the point that large cost reductions were possible and, if achieved, could prove transformative to our energy industry.

The best news I see from this coverage is that there seems to be little opposition from mainstream outlets to CDR (definitely not the case with AM). The only opposition to CDR comes from the Guardian article, which cites Naomi Klein and Rachel Smolker from Biofuels Watch as detractors. The overwhelming majority of leading NGOs, policy, and industry leaders have not called for CDR research and development to be limited, which is highly encouraging for the CDR field .

A graphic to help map the Carbon Dioxide Removal ("CDR") field

For the carbon dioxide removal ("CDR") field, breadth is simultaneously a blessing and a curse. On the bright side, the numerous approaches to CDR suggest the potential for deploying a diverse portfolio of CDR projects that reduces both the risks and costs of preventing climate change. But the down side of breadth is complexity, which makes the CDR field difficult to explain and envision, and can lead to confusion about how to catalyze development of CDR approaches as a result. In the graphic below, I've attempted to categorize and map the most prominent aspects of CDR in as comprehensive and clear a manner as possible:

CDR pathways
CDR pathways

It is critical to note that not all of the elements of this graphic are exclusive to CDR. For example, direct air capture ("DAC") machines can be used to create hydrocarbon fuels (instead of for carbon sequestration purposes). In a similar manner, biochar can be burned to create electricity instead of applied to soils as a carbon sink. Even more broadly, compressed CO2 can come from many places, including from fossil-fueled power plants with carbon capture and sequestration ("CCS") systems. Unpacking how each of the elements for various CDR processes fit into wider industrial systems is critical for designing effective strategies for developing various CDR approaches -- hopefully this visualization of the field can help with that process

Making progress towards separating CDR from the geoengineering umbrella?

Many leading experts (as well as this blog) have long advocated for removing carbon dioxide removal (“CDR”) approaches from the geoengineering umbrella. So it is great to see not a single mention of CDR in the recent Economist article advocating for careful, small-scale geoengineering research. Separating CDR from geoengineering techniques enables a much clearer conversation around the appropriate role for each field. And while misleading/confusing articles that conflate CDR and geoengineering continue to pop up in respected sources (such as Scientific American), hopefully articles like the recent one in the Economist become the norm, not the exception.

Problems with $17T-Save-the-Planet headlines

Bloomberg news recently ran an article on conventional Carbon Capture and Storage (CCS) technology titled "We Now Know How to Save the Planet. For $17.6 Trillion." While "saving the planet" sounds great and "$17.6 trillion" sounds absurdly large, both claims are probably incorrect and likely to generate misleading perceptions about the appropriate role that conventional CCS technology might play in the fight against climate change. For one, deploying large-scale conventional CCS is unlikely to be enough to "save the planet" from climate change by itself. Emissions from the power sector only comprise about a quarter of all GHG emissions, and conventional CCS has little ability to decarbonze other sectors that represent net sources of GHG emissions today, such as agriculture, forestry, and transportation:

Pie chart that shows different sectors. 26 percent is from energy supply; 13 percent is from transport; 8 percent is from residential and commercial buildings; 19 percent is from industry; 14 percent is from agriculture; 17 percent is from forestry; and 3 percent is from waste and wastewater.

Source: EPA website

While CCS could provide a critically important component of a broader portfolio of solutions to prevent climate change, it isn't likely that CCS alone will "save the planet."

An important caveat here is that the Bloomberg article only analyzed "conventional" CCS on stationary power sources. In fact, there are many ways to achieve "CCS" through non-conventional means: through planting more trees, managing agricultural lands using carbon sequestering approaches, and restoring wetlands/grasslands, to name a few. With this expanded view of what CCS means, CCS can have a much larger impact on preventing climate change, especially in the difficult-to-decarbonize sectors like forestry and agriculture.

But returning to the article, the second key problem is the fact that the $17T figure cited for the estimated cost of deploying conventional CCS globally is likely too high. To get this $17T estimate, the author applies the cost of a first-of-a-kind CCS project in Canada across all power plants globally. This is akin to applying the cost of a 1980s solar plant to estimate the overall cost to deploy solar across the globe: it would fail to factor in the decades of R&D and cost declines that happen as more and more projects get installed.

Solar PV chart
Solar PV chart

Source: adapted from

Energy technologies take decades to develop, but when they do, they follow fairly predictable learning curves:

energy learning curves
energy learning curves

Source: Dan Kammen, UC Berkeley (lecture notes 17)

So long as conventional CCS doesn't face the same safety/regulatory hurdles as nuclear and can benefit from some degree of economies of scale in manufacturing, the overall cost of CCS would likely be an order of magnitude less than this estimate if conventional CCS were deployed at the massive scales suggested in the article. For such a large-scale deployment of conventional CCS, even a $5T price tag spread evenly over 25 years would amount to a capital cost of about $250 billion per year -- around a quarter of a percent of global GDP and equal to what we invest annually today in clean energy. It is fair to say that CCS is an immature, costly, and unproven technology today; it is not fair to simply assume that CCS will remain this way indefinitely -- especially if we continue to invest in R&D for CCS technology in the future.

The bottom line is that the Bloomberg article creates a significantly skewed understanding of what role conventional CCS technology might play in the fight against climate change. While a more nuanced discussion around the appropriate role for CCS might be less prone to catchy headlines, it is nevertheless important to engage in today.

Are Negative Emissions a "Myth"?

In a recent column for Project Syndicate, Lili Fuhr and Niclas Hallstrom rail against carbon capture and sequestration (CCS) and carbon dioxide removal (CDR) technologies, counting them among the group of "ineffective or impossible" solutions to climate change. The sad reality is that today, Fuhr and Hallstrom's conclusion is not that far from the truth for most most CDR solutions, which are not cost-competitive and/or technically-proven compared to other GHG abatement approaches. By far the best way to deal with climate change would be to follow Fuhr and Hallstrom's recommendation "to reduce emissions fast, while developing alternative energy sources that allow us to leave fossil fuels in the ground."

But while "this imperative is almost shockingly straightforward," the reality of the situation is that we are not reducing emissions nearly fast enough:

CDR Scenarios
CDR Scenarios

Above: Adapted from "Betting on Negative Emissions." 

So what happens in the event that we don't follow Fuhr and Hallstrom's prescription for preventing climate change? Or even worse, what happens if it turns out that we need to reduce CO2 levels in the atmosphere even further than we thought to avoid dangerous climate change? The only three options we would be left with are:

1) Failing to prevent climate change

2) Implementing highly untested and risky solar radiation management geoengineering techniques (such as injecting sulfates into the atmosphere)

3) Developing cost-effective and sustainable CDR systems to remove carbon from the atmosphere in addition to decarbonizing our economy.

None of these options sound great, but option 3 (deploying CDR technologies at scale) is the only one that a) prevents climate change by dealing with its root cause, and b) doesn't introduce completely novel risks to our society in the process.

So while CDR solutions might be ineffective today, CDR solutions could prove to be an absolutely critical option to preventing climate change in the future. Fuhr and Hallstrom are also right that some CDR approaches like biomass energy with CCS (bio-CCS) could "have enormous development implications, provoking large-scale land, most likely from relatively poor people." But Fuhr and Hallstrom are wrong that these negative consequences definitely "would" happen, especially if a large portfolio of CDR approaches (spanning not just bio-CCS but also biochar, direct air capture, reforestation/ecosystem restoration, land management, and enhanced mineral weathering) were pursued to provide negative emissions.

Instead of stridently arguing against CDR deployments, then, I would recommend that Fuhr and Hallstrom advocate for appropriate research on how to do CDR effectively and sustainably alongside broader decarbonization of the economy. Because the one thing I'm sure of is this: the reality of our current political situation makes it a distinct probability that we don't decarbonize quickly enough to prevent climate change. And given this reality, investing today in an appropriate amount of R&D to develop effective CDR solutions makes a lot of sense.