"The Carbon removal sector needs a new story"

[Greg Rau]

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?  

Forwarded this email? Subscribe here for more The Carbon removal sector needs a new story From speed and scale to prove and learn Robert Höglund Feb 4   READ IN APP   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

[GRETCHEN & RON LARSON]

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.

 

Ron

 

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[Robert Höglund]

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
Robert

[Bruce Melton -- Austin, Texas]

Not one single word about incentives... t-Rump has not only preserved IRS 45Q, but enhanced it. The message is clear. The regime cares only about money. They could give a hoot about climate change, they just want to eliminate pollution regulation to increase profits and give our taxpayer money to big business. Paying $180 ton for CO2 sequestration is huge and industry is ramping up as fast as they can to get in on the upcurve of 45Q incentives - that have no pay cap, either individually or cumulatively.

The future of carbon removal is in new revenue streams from taxpayer funded incentives. Voluntary incentives are how we have doubled the amount of climate pollution in our atmosphere in the last 35 years when we were supposed to be lowering to 1990 levels. 

Steep trails and thanks for the link Greg,

Bruce

Bruce Melton PE
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
8103 Kirkham Drive
Austin, Texas 78736
(512)799-7998
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[Bruce Melton -- Austin, Texas]

Robert. Thanks for replying. I posted to this thread a couple hours ago but it seems to have been frozen by the internet vortex.

I would like to hear what you have to say about IRS 45Q. This is the future of carbon removal in my opinion, with industry falling all over themselves to design and build for the lucrative cash pay that is three times or more the cost of mining or refining CO2. And the bonus points are;  the regime not only did not nuke 45Q, they enhanced it because it is big money to their favorite players with no individual or cumulative cap on cash pay.

Steep trails,

Bruce

Bruce Melton PE
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
8103 Kirkham Drive
Austin, Texas 78736
(512)799-7998
ClimateDiscovery.org
ClimateChangePhoto.org
MeltonEngineering.com
Face...@Bruce.Melton.395
Inst...@Bruce.C.Melton
The Band Climate Change
Twitter - BruceCMelton1 

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[GRETCHEN & RON LARSON]

Robert and CDR list:

 

    Thanks for the clarifications.  

     One more question:    In your first figure you show CDR (on average, not including biochar) is today in a declining position.   I was not aware of this, but also not too surprised..   Certainly both BECCS and DACCS literature worries a lot about moving CO2 around (and down).  But I had thought both were still in a growth phase.  

      What is scary (from your response) is the possibility that biochar itself will also grow slower because other CDR options are now in the downward phase of your first figure.   Is there anything the biochar industry can and should be doing to overcome this "slowdown phase defect" - which they don't share?

 

    one more below.

On 02/05/2026 6:15 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. 

      RWL.  Today's new  concern about biochar being part of a new negative CDR world is that biochar is making sense independent of CDR.  In many cases, biochar is paying off in 2 or 3 years for soil, not climate, reasons.  Greg's first question (see below) includes your word "conditional".  I feel that biochar should not be in any "conditional" example.

     Stated differently,  CDR options are almost universally shown only as costs.   CDR rankings could also have a row showing investment character.  Could be done by showing an IRR (if one exists).  So hope you can find a way to add this investment character to future CDR comparison lists.   I've seen this accomplished with biochar having a negative cost, but I'd prefer one more row.

 

    Again, thanks for today's clarifications.

 

Ron

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[Robert Höglund]

sales are up for CDR in total, but mostly due to Microsoft. The HYPE is down though pretty clearly. The idea that we were going to do 6-10 Gt by 2050 and grow linearly from today up until that number is a story that is going away. 

Biochar will probably do best of all the CDR methods

best

Robert Höglund
marginalcarbon.com  

marginalcarbon.substack.com
linkedin.com/in/roberthoglund 

+46 73 727 1660 (WhatsApp)

[GRETCHEN & RON LARSON]

Robert and  (now) 2 lists

 

    Thanks.  No more comments from me.   Your last comment is welcome news.   And expected.

 

Ron

 

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[Greg Rau]

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 

*https://climatemodels.uchicago.edu/geocarb/archer.2009.ann_rev_tail.pdf

https://groups.google.com/d/msgid/CarbonDioxideRemoval/ab3d78b0-2f61-45c4-aea1-284434e43f32n%40googlegroups.com

.

[Robert Höglund]

The short answer is that because there is a finite amount of money going to climate, CDR going to reduce legacy emissions compete with emissions reductions. Since most reductions are cheaper they take precedent. 

Ideally the world opens up a second budget for CDR to address legacy emissions, not connected to the budget to reach net zero. I don't see this as likely and very hard to advocate for, but maybe this is the way still

Best

Robert Höglund
marginalcarbon.com  

marginalcarbon.substack.com
linkedin.com/in/roberthoglund 

+46 73 727 1660 (WhatsApp)

[Anderson, Paul]

Robert and Greg,

 

Regarding the  statement:  “…there is a finite amount of money going to climate,”    

(My comment here is “in general”, there can be many exceptions)

 

A factor on pricing of emission reductions (ER) versus carbon removal (CDR) is that many (most?) ER require efforts that directly impact people’s life-styles (food, heating, transportation, construction, entertainment, etc.) while CDR that is paid for voluntarily by people / businesses is done by someone else (DACS, Biochar, tree planting, etc.), often far away.   Out of sight, out of mind.

 

ER relates to “current lifetime CO2e where we live” while CDR relates to “legacy CO2e in the shared atmosphere and oceans.” 

 

Maybe???? we people should pay per tonne CO2e more for ER and pay less for CDR?  

 

That is really TWO separate questions that are not required to be combined:

1. pay  more per tonne for ER    (how to stimulate ER actions)      
2. pay  less per tonne for CDR    (price could come down with technology breakthroughs, such as less expensive faster biochar production      (which is what I am working on).

 

Both ER and CDR must happen or else global warming destroys our environment in a few generations.  

Note:  America is 250 years old this year, but will not exist 250 more years (to 2276) if climate is not fixed.

 

Paul                        (for private direct contact, write to   p...@woodgas.com  )

 

Doc / Dr TLUD / Paul S. Anderson, PhD

Email:  psan...@ilstu.edu       Skype:   paultlud     Mobile & WhatsApp: 309-531-4434

Website:    https://woodgas.com see Resources page for 2023 “Roadmap for Climate Intervention with Biochar” and 2020 white paper, 2) RoCC kilns, and 3) TLUD stove technology.                       

 

From: carbondiox...@googlegroups.com <carbondiox...@googlegroups.com> On Behalf Of Robert Höglund
Sent: Saturday, February 7, 2026 1:00 AM
To: Greg Rau <gh...@sbcglobal.net>
Cc: Carbon Dioxide Removal <carbondiox...@googlegroups.com>
Subject: Re: [CDR] "The Carbon removal sector needs a new story"

 

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[GRETCHEN & RON LARSON]

Robert,  Greg, list

 

     I apologize in advance, but feel biochar's position still needs to be considered as being a pretty important and successful part of CDR.  See inserts below.

On 02/06/2026 10:59 PM PST Robert Höglund <robert.d...@gmail.com> wrote:

RH1: " The short answer is that because there is a finite amount of money going to climate, CDR going to reduce legacy emissions compete with emissions reductions. Since most reductions are cheaper they take precedent. "

RWL1:    Both sentences are true, except your "reductions" (solar and wind mostly) are intermittent.   The needed storage backup is affordable until you get down to the last few percent of fossil.  Then biomass (biochar in the CDR world) has a potential place (not yet needed).  

      BECCS can make the same case, but it is always a cost, not an investment.  (Repeating here my previous emphases on out-year carbon and economic returns.)

 

RH2: " Ideally the world opens up a second budget for CDR to address legacy emissions, not connected to the budget to reach net zero".

RWL2:  Hmm.   Not quite following here.  Biochar seems to now be doing both - with ease.

    But likely that biochar proponents would agree to anything "ideal".

 

RH3: " I don't see this as likely and very hard to advocate for, but maybe this is the way still."

RWL3:  Agreed.  But if there were two budgets, biochar would be eligible in both.   Some biochar should be seen as a cost - but lower cost than what it is replacing.

 

Ron.   (Still agreeing with Robert that some competitors aren't able to make a compelling economic argument today - (but could in the future).  For biochar - no need to wait.

     (I am helping with a biochar application where payoff is measured in weeks - and is also an investment.   Not a cost.)

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[Bruce Melton -- Austin, Texas]

Robert,

We have a second budget for CDR already, and a third: IRS 45Q and California Low Carbon Fuels Sequestration Incentive.

The new story is that without CDR, Earth systems fail because tipping is active. The results are natural feedback emissions that dwarf humankind's.

The story goes on that, if we do not stop tipping by the point of no return suggested for most already activated tipping elements to be mid-century, we experience these natural feedback emissions dwarfing humankind's, from permafrost, coastal, peat, tropical/boreal/high altitude forests, and more. At risk are more than 10 trillion tons of greenhouse gases, much of which would be released in decadel time frames, vastly compounding mandatory emergency cooling and CDR to stop tipping before the point of no return.

The story ends with emissions reductions alone cannot cool in time frames that matter to tipping, they can only reduce the amount of CDR and emergency temporary cooling by a small amount. 

You did not mention these positive incentives at all in your article. Why? 

IRS 45Q is particularly encouraging because it has no pay cap either individually or cumulatively and it made it through tRump's cuts unscathed (it was actually enhanced).

Steep trails,

Bruce

Bruce Melton PE
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
8103 Kirkham Drive
Austin, Texas 78736
(512)799-7998
ClimateDiscovery.org
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MeltonEngineering.com
Face...@Bruce.Melton.395
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[robert...@gmail.com]

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 +1.5^oC (without SRM) assumes returning CO_s 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 +2.3^sC in 2060 before slowly falling to +1.5^oC 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 +1.5^oC/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 +1.5^oC 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 60^oN 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 +1.5^oC, maybe to +1^oC or even below.  +1^oC 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

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[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.

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[Robert Höglund]

Yes its good 45Q remains

It 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 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 +1.5^oC having peaked briefly at +1.6^oC.

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 1^oC (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.

Regards

Robert

[GRETCHEN & RON LARSON]

Hi again Robert Hoglund and others:

 

     The current allowable  "payment" for DACCS and BECCS  sequestration was given to me just now by my Google AI helper:

• "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.

If these two CDR options are in trouble, my guess is that the low 45Q support levels are the cause of their trouble - not a future solution.

 

    Biochar tried to get into 45Q (at any level) - but has been excluded.  Maybe why biochar is succeeding so well?

 

Ron

 

     ps  Robert Chris' implementation numbers for biochar below are way out of date.

 

 

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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.

Regards

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.

Regards

Robert