The Carbon Removal Blended Tonne Whitepaper

Published on June 23, 2023

This whitepaper is also published on GitHub, where we are collecting feedback. We invite you to view comments and add your own thoughts here.


Currently, most durable carbon removals, like direct air capture, are sold out or very nearly so.¹ Many durable carbon credits on the market today are pre-selling future vintages that will not be delivered for several years.² This means that although the carbon removed will be stored for 1,000+ years, it won’t actually be removed from the atmosphere until a future date. Less-durable carbon removal, like soil carbon and forestry, is available now, and in greater quantities. But, as it stands, on their own, neither option satisfies the net-zero requirements that so many purchasers would like to qualify for.

The more durable carbon removals lack immediacy and could only be used to qualify for emissions that happen after the carbon is actually removed, while the less-durable options don’t store carbon dioxide long enough to compensate for fossil fuel emissions, which linger in the atmosphere for hundreds of thousands of years.³ To solve this issue Nori is proposing a ‘blended tonne’ that brings together the strengths of both —immediacy and durability — to offer a net-zero solution. By combining immediately available soil carbon credits with future available durable carbon removals, Nori is creating a product that sequesters carbon today while meeting the permanency requirements of net-zero standards.

By pairing each highly durable carbon removal asset with a less durable one that is immediately available and has an overlapping timeline, purchasers may credibly claim to be taking net-zero-qualifying climate action now while they fund and await the delivery of their high-durability carbon removal.⁴


Carbon removal is the process by which carbon dioxide is taken out of the atmosphere and stored for some duration of time in a medium. According to the UNEP Emissions Gap Report, by 2050 the world needs to sequester approximately 8 gigatonnes of carbon dioxide annually per year.⁵ ⁶ One of the most relevant axes for evaluating carbon removal is its durability: how long does it stay stored after it is removed from the atmosphere?⁷

The durability of carbon removal methodologies can be defined through the type of carbon storage — biological versus geological carbon storage.⁸

Biological carbon removal and storage lasts within the timespan of organic life cycles, and is generally a component of the "fast carbon cycle". In this cycle, carbon is exchanged between living organisms that retain carbon while alive and then release it upon death, allowing it to be taken up by other organisms. While the biological cycle can last anywhere from days to thousands of years, the expected storage period for most forestry and soil carbon removal projects ranges between 1 and 100 years. Anything within this range is considered to be relatively low durability.

Geological carbon removal lasts on the civilizational time scale or longer, and is a part of the “slow carbon cycle”. It involves the exchange of carbon between Earth's atmosphere, oceans, and crust through processes like weathering, erosion, deposition, and burial. Carbon in the slow carbon cycle is often mineralized or otherwise stored in a stable form unlikely to be cycled back into the atmosphere on human timescales.⁹ The storage period for these is generally accepted to be a minimum of 1000 years or functionally permanent. This is considered highly durable.

The dominant framework for companies and others wishing to credibly claim negated carbon emissions is called net zero. Though not defined by any single standard at the moment, the Science Based Targets Initiative (SBTi) standard is often referenced.¹⁰ SBTi, and others, have designed net-zero standards to be strict, as previous attempts by companies making environmental claims have often been overstated or otherwise improper. Net-zero commitments imply that if a tonne of carbon dioxide is mobilized (emitted), an equivalent amount of carbon needs to be immobilized (removed and stored) in a permanent way, or at the very least, in a similar way.¹¹

Since fossil fuel emissions come from carbon that was released from geological storage where it would likely have remained were it not for human intervention, the release should be addressed by removing and fixing carbon in permanent storage.¹² That means that a tonne of carbon dioxide emitted through the burning of fossil fuels can not be offset to result in ‘net zero’ by removing a tonne via fast-cycle carbon removal alone, nor by any type of reduction or avoidance offset.

(While beyond the scope of this paper, less durable fast-cycle carbon removal like regenerative agriculture or afforestation/reforestation could potentially be used to cancel out land-use emissions on a one-for-one basis.)

The problem is twofold:

  1. Nearly all durable carbon removal available for purchase today represents future carbon removal, with delivery several years out.
  2. New emissions begin causing damage as soon as they enter the atmosphere — so you can’t achieve net zero by addressing current or past emissions retroactively with future carbon removals.

Since most durable carbon removal purchases possible today are, by necessity, commitments to buy carbon removed in the future, a current or past vintage is required to make a net zero status claim credible in the present.

The solution we propose is combining a tonne of fast-cycle (biological) carbon removal with another tonne of slow-cycle (geological) carbon removal to create a hybrid credit, where currently-available but impermanent (fast) soil carbon rolls over into a future high-permanence (slow) carbon credit to be delivered within the lifespan of the soil credit. Typically we expect the slow carbon to be delivered before the expiration of the fast carbon, thus resulting in substantial overlap during which the climate impact may be even higher than the absolute tonnes purchased.¹³

Technical Considerations

To ensure that the bundled hybrid credits meet the highest standards, Nori follows rigorous criteria for credit quality. The standards for soil carbon NRT (Nori Carbon Removal Tonne) quantification and issuance are described in detail in the Nori US Croplands Methodology.¹⁴ These standards include conservative, ex-post quantification, which ensures immediate impact and minimizes the risk of overestimating the amount of carbon removed. The standards also require third-party verification of practices, which guarantees that an independent entity has reviewed and confirmed that the carbon removal activities have been performed in accordance with the established guidelines.

Slow-cycle carbon credits will only be accepted from Nori-approved suppliers that meet some set of common standards for carbon credits upon delivery, such as the ICROA (International Carbon Reduction and Offsetting Accreditation) principles,¹⁵ or the ICVCM (Integrity Council for the Voluntary Carbon Market) core carbon principles.¹⁶ Nori’s approval for the high-durability credits requires that when delivered, the credits are real, additional, measured, verified, unique, permanent, and sustainable. This will ensure that the credits are genuine, not double-counted, and that the carbon removal projects have a lasting, positive impact on the environment and society. In addition, Nori will provide robust, transparent governance through the Nori marketplace and registry. Improved standards that are developed with the aim of helping the CDR industry scale while ensuring scientifically robust methodologies and market integrity will be incorporated into Nori’s approval process as appropriate.

Moreover, the quantification and MRV (Monitoring, Reporting, and Verification) process for slow-cycle carbon removals must be transparent and comply with all applicable regulatory requirements. This transparency will help maintain trust and enable accountability of projects. Nori will evaluate additional standards for potential introduction in future methodologies to further strengthen the quality and integrity of the credits.

Nori recognizes vintages for carbon removal credits, which designate the year in which a carbon removal project achieved the verified removal. To be eligible for bundling, the NRT storage lifetime (the vintage year plus ten years) must overlap with the expected delivery date of the high-durability credit by a minimum of one year. This conservative criterion will ensure that the purchased credits have no gaps in their intended impact and buyers can rely on the carbon removals over the long term.


Ensuring that a buyer of a blended tonne purchases the full carbon removal credit, i.e. both the less durable fast-cycle credit available immediately and the more durable slow-cycle credit available in the future, is essential if companies are going to use this product for net-zero claims. While Nori has not determined the exact mechanism to ensure the complete purchase of a blended tonne, there are a few options being considered—research into the legal and financial aspects needs to be conducted before a final mechanism is chosen. Additionally, further user research of buyer and supplier needs is required. Further, Nori expects iteration in collaboration with market participants on these mechanisms as the CDR industry matures and grows.

We are currently considering the following mechanisms:

  1. The buyer pays for the full amount of the carbon removal credit upfront. In this scenario, if a blended tonne is worth $520 (plus a transaction fee) — $20 for the NRT would be paid immediately to the soil carbon (fast-cycle) supplier and the appropriate percentage of the transaction fee would be paid to Nori; $500 (plus the remaining transaction fee to Nori) would be placed into a savings or escrow account available to the slow-cycle carbon removal supplier upon delivery of the carbon credit at which time the remaining transaction fee would be paid to Nori.

  2. The buyer pays for some portion of the carbon removal credit upfront. In this scenario, if a blended tonne is worth $520 (plus a transaction fee) — $20 for the NRT would be paid immediately to the soil carbon (fast-cycle) supplier and the appropriate percentage of the transaction fee would be paid to Nori; a percentage of the remaining $500 (plus a corresponding percentage of the transaction fee) would be placed into a savings or escrow account available to the slow-cycle carbon removal supplier (and the transaction fee to Nori) as specific contractually-required milestones were met. Once the supplier delivers the carbon removal credit the remaining balance (and the remaining transaction fee balance) would be paid to the slow-cycle carbon removal supplier and Nori respectively.

  3. The buyer pays only for the NRT upfront. In this scenario, if a blended tonne is worth $520 (plus a transaction fee) — $20 for the NRT would be paid immediately to the soil carbon (fast-cycle) supplier and the appropriate percentage of the transaction fee would be paid to Nori; $500 (plus the remaining transaction fee to Nori) would be paid to the slow-cycle carbon removal supplier upon delivery of the carbon removal credit to the buyer. The buyer would be under a contractual obligation to purchase the carbon removal credit but there would be no exchange of money until the credit is delivered from the slow-cycle carbon removal supplier to the buyer.

Nori must consider the situation where a supplier does not meet its obligation of delivering the slow-cycle carbon removal credit. This could be for a range of reasons such as the supplier’s technology failing or being delayed or the supplier going out of business. Nori is soliciting feedback on the best way to mitigate this risk and we are open to exploring various ways to approach this issue including insurance provided by third parties.


By combining less-durable fast-cycle carbon removal that is available now with the promise of highly-durable slow-cycle carbon removal in the future, this new product will offer both immediate and lasting impact. The blended tonne would contribute to the funding of future, more durable carbon removal solutions and slow-acting carbon techniques (like enhanced rock weathering) while allowing a credible process by which ecosystem restoration and temporary carbon storage can support proper carbon accounting and removal. Furthermore, this new type of carbon removal asset makes it both possible and easy to address this year’s emissions and, assuming proper accounting, support robust claims of ‘carbon neutrality’ or ‘net zero’.


  1. Biochar producers may disagree with this, but for the purpose of this paper we are going to consider biochar to be somewhere in-between the duration of the slow and fast carbon cycles.
  2. See split between tonnes sold vs. tonnes delivered on
  3. See
  4. See
  5. See
  6. Also see which provides a range of carbon dioxide removal scenarios ranging from 4.7 gigatonnes to 9.8 gigatonnes.
  7. This of course intersects directly with the means of carbon removal and storage.
  8. One potentially cheeky way to conceptualize biological and geological carbon removal is that biological carbon removal is hitting the pause button, but geological carbon removal is truly hitting rewind.
  11. One paradigm for carbon accounting here is colloquially referred to as “like-for-like”, e.g. if a tonne is emitted through land use change, then land use change sequestration is an appropriate negation for carbon accounting purposes. If fossil fuel emissions occur, negating those emissions requires returning an equivalent amount of those emissions into durable and likely lithospheric storage. See:
  12. There are various ways of trying to make fast carbon cycle removals equate to slow carbon cycle removals, or to use fast carbon cycle credits achieve specific temporal goals like avoiding climate tipping points. While there is merit in trying to make this approach work, and we’re open to credible scientific ways of making this a credible and ethical pathway for emissions negation, we are not currently comfortable equating the two carbon cycles for purposes of carbon accounting.
  13. This depends upon which measure is being used, but seems more useful if thinking about avoiding climate tipping points.


Radhika Moolgavkar, Head of Supply and Methodology, Nori
Rick Berg, Carbon Removal Methodology R&D Lead, Nori
Ross Kenyon, Co-founder and Creative Editor, Nori


The authors would like to acknowledge the contributions and feedback of the following individuals:

Holly Jean Buck, University at Buffalo
Margriet Kuijper, Carbon management consultant
Na’im Merchant, Carbon Removal Canada
Patrick Tsao, Nori
Robert Höglund, Marginal Carbon / Milkywire
Wil Burns, American University
Zeke Hausfather, Stripe

👋 Feedback and Comments

Embodying Nori's commitment to transparency, we've chosen an open-source approach for feedback. We invite you to contribute your thoughts, questions, relevant insights, and suggestions to refine the product concept further. Instructions on how to do so can be found here.

🎧 Mixing Fast and Slow Carbon on Reversing Climate Change

Nori's Head of Supply and Methodology, Radhika Moolgavkar, joined Ross Kenyon on Reversing Climate Change to discuss how the CDR industry has changed over time and how Nori is evolving with the net-zero-friendly "blended tonne" concept. Listen here.

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