Re: [CDR] "The Carbon removal sector needs a new story"
Michael MacCracken
Dear Robert C--I fully agree with your diagnosis that SRM is essential and its cooling effect can't be met by enough of a phasing up of CDR in the time needed. Where I would differ with you, however, is that I think that in promoting SRM/SAI, it is essential to have an exit strategy that one can offer, even if it will take through the century or more. Mitigation is not adequate as an exit strategy from higher temperatures--its main role is to keep warming from getting even warmer. And because of increasing natural emissions of CO2 due to global warming, even net zero direct human emissions may not stop warming. So, what CDR has the potential to do is to build up to become a potential exit strategy from indefinite continuance perhaps the need for further and further strengthening of SRM/SAI and adaptation. As noted, I thus think that we have to include CDR is the long-term comprehensive strategy that we argue for. If CDR can be successful faster, all the better; if not so fast, then SAI/SRM and adaptation and their limits point even further to the need for faster mitigation.
Regards, Mike MacCracken, Ph.D.
Hi all
This thread suggests that the time has come to decouple CDR from climate change policy. Whether there is a market for CDR and how it might operate is totally irrelevant to policy intended to avoid a global warming (GW) induced societal collapse. Indeed, significant investment in a forlorn attempt to give it such a role, is likely to make matters worse. Here's why.
In what follows I ignore non-CO2 GHGs. Including them makes the story significantly more complicated and only serves to make the case more strongly. If the case can be made with sufficient force without them, it makes the argument considerably more accessible. The numbers shown below come from a modified version of FaIR v2.0.0.
GW is driven by the 1100GtCO2 that remains in the atmosphere from the 2800GtCO2 emitted since industrialisation. Holding GW to +1.5oC (without SRM) assumes returning COs concentration to 350ppm. Let's for the moment assume that that's a sufficient ambition.
Let's also assume, to keep things simple, that CO2 concentration peaks at 450ppm (e.g SSP2-4.5 amended slightly so that emissions subside to 10GtCO2yr-1 by 2120 and remain there indefinitely). This would require CDR totalling 3300Gt over the next 100 years which is heavily front-loaded if we want largely to eliminate the overshoot. If we're willing to accept overshoot peaking at +2.3sC in 2060 before slowly falling to +1.5oC by 2120, we could manage with slightly less than 3000GtCO2 of CDR over the coming century.
I'd welcome correction, but I consider CDR at that scale to be utterly implausible. Data from Carbon Dioxide Removal shows CDR from af- and re-forestation flatlining at around 2GtCO2yr-1 for at least the last 25 years, and CDR from novel methods still being insignificant at little more than 1MtCO2yr-1. The economic and environmental implications of safely capturing and permanently sequestering tens of gigatonnes of atmospheric CO2, an endeavour that would be larger than the current total worldwide extractive industries, render this implausible within any useful timescale. Some believe this could be done by ocean iron fertilisation, or some similar marine based process. There is currently no evidence to support this.
As an instrument of climate policy, CDR is so far from being able to make a worthwhile contribution that its inclusion in those policy considerations should be reconsidered. Indeed, it can be argued that any investment in anything other the the lowest hanging CDR fruit, detracts from devoting financial and other resources in those policies that might have some meaningful climate impact; namely reducing emissions by a range of measures and SRM.
That said, there is no reason not to encourage a market in CDR. If entrepreneurs see an opportunity to make money, good luck to them. Some CDR technologies also have major environmental benefits that should be promoted. But let's not kid ourselves that any of that will be doing much to avert a climate catastrophe.
If we now look at whether +1.5oC/350ppm is a sufficient ambition, and how much overshoot we think might be safe, the case against CDR becomes even more compelling. The impacts of the climate change that's already emerged from GW that has only just reached +1.5oC are now manifest. These changes will not stop if we hold GW at that level. For example, Arctic amplification will mean the continuing and hastening loss of land and sea ice above 60oN and this will have increasing effects on climate elsewhere, in particular because there is every reason to suppose that AMOC will continue to slow, maybe even to a standstill. There seems a compelling risk based case to reduce warming to much lower than +1.5oC, maybe to +1oC or even below. +1oC implies CO2 of around 300ppm. Delivering that makes our plausible CDR look even more pointless. The problem here is twofold. Not only would CDR have no chance of restoring atmospheric CO2 to a safe level, but the overshoot while we were trying would be extreme and extended. Indeed, the likelihood is that the accumulated GW would soon trigger one or more of the cascading tipping points much explored by Lenton and his team.
Any sane risk focussed climate policy must now regard time as being of the essence. Like it or not that means SRM must now be regarded as necessary and financial and other resources must be invested in the R&D to derisk it to the extent possible. This has become a top policy priority.
In summary, let the entrepreneurs and environmentalists play with CDR to their hearts' content, but those with a serious interest in securing a safe climate future for humanity and the rest of life with whom we share the planet, need to focus on cooling. That means SRM because it is radiatively efficient. But retiring fossil fuels remains vital because they are the source of the problem. Sadly, their retirement can no longer be the only policy option (having discounted CDR in this regard) because CO2 is radiatively extremely inefficient and we have allowed the amount of atmopsheric CO2 to accumulate to such an extent that to make any appreciable temperature difference, truly immense amounts of it have to be removed from the atmosphere and there is currently no plausible way of doing that at the scale and speed required.
There is no so-called 'moral hazard' here because both SRM and the retirement of fossil fuels are equally important and mutually supporting; neither works without the other.
Regards
Dr Robert Chris
On 06/02/2026 23:51, Greg Rau wrote:
----Thanks Robert. You say we do need cheap, effective CDR to remove legacy CO2 "but having someone to pay for it is relatively far away". I find that illogical. We are suffering right now from excess legacy CO2 that can only be reduced (faster than on geologic time scales) via pro-active CDR, not by reducing emissions. This will only get worse by the time we ever get to zero emissions. Why shouldn't CDR have at least equal footing (in terms of investment and incentives) with emissions reduction rather than being simply view as offsetting hard to abate emissions?
This plays in to my second comment "On the other hand if emissions reduction is wildly successful, won't this present a moral hazard to CDR?" Think about it, if all people want is zero emissions and this achieved by actually reducing emissions, then by their reasoning, why do we need CDR? This again fails to appreciate that by then we may have 2000 Gts of legacy CO2 up there that will impact climate and ocean chemistry for many hundreds to thousands of years*. This can ony be remedied by CDR and SRM (the latter, just addressing the climate part (in theory)).
Bottom line, there are both near-term and long-term, multi $T risks/reasons to elevate CDR beyond just being an appendage to emissions reduction. Why is this being ignored in policy/investment circles? Isn't this a "new story" that CDR needs?Regards,Greg
On Thursday, February 5, 2026 at 06:15:59 AM PST, Robert Höglund <robert.d...@gmail.com> wrote:
Thanks for the discussion Ron and Greg!
Ron, my comment on CDR on the hype curve is for carbon removal as an aggregated topic (which is how most people talk about it), not technology per technology. If you break out biochar I agree it is growing and not on a downwards journey.
Figure 3 is not mine, but comes from the Climate change project, it only includes mitigation costs of low carbon inputs that companies have reported. CDR is not a part of it.
Greg, one of the big reasons for why we need to build CDR as a ready tool with low costs and MRV etc worked out, is so that it is ready to remove all those legacy emissions. But having someone to pay for it is relatively far away.
Not sure what you meant with this comment. "GR - One the other hand if emissions reduction is wildly successful, won't this present a moral hazard to CDR?"
best regards
Roberttorsdag 5 februari 2026 kl. 08:06:04 UTC+1 skrev rongre...@comcast.net:
Greg and list:I've been preparing a comment for the "biochar.io" community on this same report, so will just give a few comments here first.1. I see no evidence here that he is giving a report here that includes biochar - a topic he knows well His Figure 1 with a trough may now be happening with BECCS and DACCS, but certainly not biochar. Doubling times for biochar are still less than two years - no negative slope years at all.2. His Figure 2 (with about 10 boxes) doesn't include a box for agriculture, forestry or municipal wastes. Ag is the world's largest industry by some measures.3. In his Figure 3, I would draw the price range for biochar much as he has drawn top-most for "steel". Note the left -most number on the abscissa should be 1, not 0.I won't comment on your two quotes below - except to repeat that I disagree with a lot if he is including biochar in this note - which doesn't seem possible.I have good respect for everything else I have seen from Hoglund on biochar (now the leading CDR technology by some measures).Thanks for your alert on this out-of-character report.RonOn 02/04/2026 9:35 PM PST Greg Rau <gh...@sbcglobal.net> wrote:from Robert Hoglund's article (below):"Gigatonne scale CDR is conditional on success on emission reductions. That means the primary political fight is for stronger climate policy, not for scaling carbon removal in isolation."GR - One the other hand if emissions reduction is wildly successful, won't this present a moral hazard to CDR?"Finally, the biggest use case for CDR may be to remove legacy emissions to bring temperatures back down, but who will want to pay for that and if so when, are even bigger and more uncertain questions."GR - This truly is the biggest case for CDR, but no one is interested? They will be when they find out how long Earth inhabitants will suffer waiting for natural CDR to return CO2 and climate to "normal" levels on geologic time scales. But then there's always SRM in the meantime?
The Carbon removal sector needs a new story
From speed and scale to prove and learn
I think most people in CDR feel that a phase shift has happened. The old story doesn’t hold but no new clear narrative has emerged of what role CDR really will take in the real world in the decades to come. Voluntary demand is likely to continue to increase but not explode, compliance demand is slow and may be much smaller than people expect even in the long-run. To me, the new story is more prove and learn than speed and scale.
First, what is likely to happen? Starting with the next ten years
The number of companies buying durable CDR will continue to increase, but there is no reason to think it will explode. The ones buying will primarily be seeking to meet targets. Like operational net zero targets by 2030 for their Scope 1,2 and business travel. Something that would make more companies buy CDR for such operational net zero claims is validation for that practice from SBTi, ISO etc. Regardless, I expect voluntary demand for durable CDR to result in low tens of millions of tonnes delivered per year in the mid 2030s. A possible scenario is that total contracted tonnes temporarily peaked in 2025 or 2026 because of Microsoft’s forward buying spree, and that it will take a while before we reach 30 million tonnes contracted in one year again.
For compliance, the only real driver for durable carbon removal in the medium term is inclusion into the UK and EU ETS. But simple integration of CDR into UK & EU ETS would likely not lead to much, if any CDR demand in the next ten years since ETS allowance prices are lower than even cheap CDR levels. Any CDR included in that timeframe would need to be paid for by governments through contracts for difference or similar. Such government support will enable single millions of tonnes per year, maybe more, in the early 2030s but I think voluntary demand will continue to dominate durable CDR delivered for the next 5-10 years.
Now, in my book, tens of millions of tonnes delivered across multiple methods is an incredible win. That means we proved that CDR works outside of small experiments and learn a lot about how to bring down costs and about which methods have the highest potential to scale to much higher volumes. This has to me always been the primary objective of the early CDR ecosystem.
Of course it is a brutal hype adjustment as the narrative that many painted for CDR was 6-10 gigatonne by 2050 and a linear growth towards that. CDR has been traveling downwards on the hype curve for at least a year and a half. Consequently, I think venture capital investments will continue to fall, this phase favors patient capital. Maybe we’ll hit the trough of disillusionment bottom this year, readjusting expectations, and start aiming for the plateau of productivity.
My estimate for where CDR is on the Gartner hype cycle
Post 2035. What does the plateau of productivity look like?
CDR is probably the cheapest mitigation option for something like 2-5 Gt carbon dioxide per year. It’s hard to say exactly as technology development progresses and local conditions vary.
My long run macro estimate of where CDR is the cheapest mitigation option for CO₂ emissions.
But, that number only matters if the whole world is trying hard to get to net zero, and treats CDR as a valid mitigation option. Currently neither is really true.
Compliance is usually expected to be the biggest driver in the longer run, but only the EU and UK have live net zero plans that would force all CO₂ emissions down to zero. If that happened, CDR might be the cheapest option for 100-200 Mt per year of emissions in those two jurisdictions, demand that would need to be met in the 2040s. (However for aviation and shipping which are part of that number, fuel switch is currently mandated in the EU with no real role for CDR).
If the rest of the world does not follow Europe, I think it is quite likely that the EU does not push full decarbonization for heavy industry. This is driven by a need to keep industrial capacity in the union, not the least to have an industrial base in case war production needs to be ramped up. The cost for both CCS and CDR is not likely going to be able to be pushed to heavy industry. If Europe maintains net zero plans it will likely need to spread the cost of mitigating heavy industry, either through the state directly paying, or through demand side legislation making customers pay, combined with a granular and very heavily enforced CBAM.If the rest of the world is serious about reaching net zero there will be a lot more CDR demand. US ambitious individual states are things to look at for example. But there is no scenario where we build out gigatonnes of CDR if global emissions are not rapidly falling. Gigatonne scale CDR is conditional on success on emission reductions. That means the primary political fight is for stronger climate policy, not for scaling carbon removal in isolation.In the light of this, it is actually possible that voluntary demand could exceed compliance demand even in the medium to long run. CDR is cheaper than many substitution options companies have. In a couple of decades I think it is possible (but not necessarily likely) with hundreds of millions of tonnes in voluntary corporate annual demand if the narrative shifts sharply and companies feel buying CDR is expected from them. Almost all companies can afford to buy durable CDR for a subset of their emissions, and some can afford it for all. But in no case I see voluntary demand reaching gigatonnes per year.CDR is cheaper than many substitution options companies have today. From Climate Change Project companies’ mitigation cost estimates for low carbon inputs.
Finally, the biggest use case for CDR may be to remove legacy emissions to bring temperatures back down, but who will want to pay for that and if so when, are even bigger and more uncertain questions.
What is the new story then?
To me, the CDR sector has two roles. Building, proving and improving a toolkit that the world can use for gigatonne level of removals when it gets serious about reaching net zero. And, providing a way for companies, ambitious regions and countries and individuals to take responsibility for their emissions today while making credible claims. The story is not rapid scale, but proving, learning, and earning trust.If you are working on carbon removal, nothing in this text should make you put in less effort. We need to keep developing CDR, test new methods, lower costs, find out what works and build demand so that we have the best tools available for global net zero and large scale legacy emission removal. But we need to do it with realistic expectations. The road ahead is narrow.
© 2026 Robert Höglund
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robert...@gmail.com
Hi Mike
I've no problem with that. I just presented one scenario but there are obviously many alternatives.
In the scenario I used below, emissions reduced to 10GtCO2yr-1 by 2120 and remained there. You then have the question about what you do with the residual emissions. Clearly one option is to reduce them to zero but, equally, you could offset them with CDR. A lot depends on the level of residual emissions and the extent to which our successors have been successful in finding alternative energy sources. We can't know that today, so our policy decisions have to be open in that regard. Our main obligation is to keep humanity in the game so that future decision makers have the luxury of getting to screw up for themselves. Whether they would want to get to net negative emissions is a question we can leave to them but no amount of CDR that we can plausibly expect to do in the near future is likely to have much impact on their CDR decision in the future.
My argument today is that the radiative inefficiency of CO2 is such that we're better off to focus our GHG reducing efforts on retiring fossil fuels simply because it has to make more economic sense to invest in technologies to and behaviour changes that reduce energy intensity (MJ/$GDP) and/or carbon intensity (kgCO2/MJ), than to launch a gargantuan new industrial infrastructure with all its additional costs.
In the boundary case, in which we retire all fossil fuels in 2026 (obviously only a thought experiment!), ppm gradually subsides to 350 by 2300 but warming is held steady at +1.5oC having peaked briefly at +1.6oC.
So, the model suggests that the amount of CDR that might be needed is dependent on the rate at which emissions are retired, the rate and extent to which SRM is called and the amount of warming and overshoot we're prepared to tolerate. Nevertheless, as a policy choice, retiring fossil fuels should always take precedence over CDR because it just makes no sense, as anything other than an expedient short term strategy, to emit the stuff only to then have to recapture and sequester it.
But the central point I'm making is the one you endorse, that without SRM the whole house of cards collapses. And the reason, that I think is not widely appreciated, is the incredibly low radiative inefficiency of CO2. For those reading this that are not aware of this, the detail is uncontroversial and is covered in several IPCC ARs including AR6. The radiative efficiency of CO2 is 1.33E10-5 Wm-2kg-1 (it's not a fixed amount and changes with the ppm). What that means in lay terms is that to generate a forcing (whether warming or cooling) of 1 Wm-2, you have to shift about 600GtCO2, that's equivalent to 15 years' global emissions at current rates. In crude terms, 1Wm-2 will generate an equilibrium temperature difference of about 1oC (this is critically dependent on Equilibrium Climate Sensitivity but we'll not go there right now!). So from a purely practical engineering perspective, to make a significant change in surface temperature you have to reduce atmospheric CO2 by a vast amount. And as if that weren’t bad enough, because of a whole load of complex interchanges within the climate system, to reduce atmospheric CO2 by any amount, you have to remove almost twice that amount from the atmosphere. That's why cooling by trying to reduce atmospheric CO2 takes so long and is so expensive.
Robert
GRETCHEN & RON LARSON
- "DACCS: Up to $180 per metric ton of CO₂ for dedicated geologic sequestration.
- BECCS: Up to $85 per metric ton of CO₂ for dedicated geologic sequestration (classified under industrial/power source capture). "
Drop another third if CCS becomes CCUS.
On 02/07/2026 2:33 PM PST Robert Höglund <robert.d...@gmail.com> wrote:Yes its good 45Q remainsIt makes DAC and BECCS in the US be a bit more competitive with biochar, but you still need voluntary buyers that found a reason to buy.Robert
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robert...@gmail.com
Hi Ron
I'm delighted to have seen your PS abut my numbers being way out of date. That's hardly surprising because they're now much more than a decade old.
Would it be too much to ask if you could provide current values for the many variables so that the computation can be brought up to date. I'm assuming that you didn't have a problem with the methodology I adopted, but of you did, perhaps it would be best to deal with that first.
Robert
Michael MacCracken
Hi Robert--Agreed, with one comment. One reason that CO2 is a relatively ineffective GHG, at least compared to methane and the chlorinated compounds is that its concentration is much higher than for the other gases and so the central parts of the bands are already well absorbed, etc. This was actually a criticism back for Arrhenius to explain with his multi-layered model and a decreasing temperature with altitude. So, CO2 is of order 525 ppm and methane is 2 ppm and the hydrofluorocarbons are another factor of 100 or more less. So, what really matters is the influence of the existing concentration and so the relative percentage increase in the concentration.
Now, as to a comparison with water vapor, which, overall, has the strongest GH effect, there is so much more water vapor in the lower atmosphere, I'm not sure how one would make the relative effectiveness calculation. With water vapor concentration going up 7% per degree and the water vapor feedback contributing to say, half of the climate sensitivity (which we can say is 3 C), that would have a 21% increase in water vapor leading to a 1.5 C warming, and a CO2 doubling contributing, without the water vapor and other feedbacks, to maybe 1 C of warming (or does the CO2 doubling get credit for all the 3 C?). Not quite clear how to say which molecule is most or least effective.
Best, Mike
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Robert Chris
Hi Ron
Reflecting overnight on my message below, I am intrigued to know the extent to which my out-of-date computation deviates from one that is in-date. I suspect that several of the variables will not have changed materially (e.g. carbon content of biomass, carbon yield per hectare, biomass density, carbon content of biochar, available land, and size of a TEU). That just leaves the production capacity of a biochar plant and the number of trips made each year by each container.
It's not very helpful merely to comment that the schedule is 'out-of-date' without explaining the extent to which it is now misleading. Numbers please. In the absence of credible numbers that show how the biochar process has radically altered in the last decade or so, one must assume that it hasn't.
As a foreigner, I don't understand quite what 45Q is or how it works. All I know is that it's some kind of tax break to encourage investment in certain activities rather than others. However effective it might be in fomenting biochar growth in the US, I'd be interested to understand how that might have any global climate change significance.
Just to be clear, if there's money to be made and local environmental benefits to be gained from ramping up biochar production, I'm all for it. In the absence of compelling new information, I just object to it being presented as part of a meaningful response to global climate change. It simply isn't sufficiently scalable.
Robert