Demystifying Carbon Removals in the Context of Sub-Global Net-Zero Targets

doi:10.21203/rs.3.rs-3034367/v1

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Demystifying Carbon Removals in the Context of Sub-Global Net-Zero Targets

https://doi.org/10.21203/rs.3.rs-3034367/v1

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The concepts of net-zero greenhouse gas (GHG) emissions and GHG-neutrality are emerging as fundamental principles for initiatives to address climate change ranging from the global to the corporate scale. Offsetting emissions by using carbon credits features in many sub-global net-zero and GHG-neutrality claims and pledges. This paper shows that regardless of whether a sub-global entity offsets its emissions using carbon credits based on GHG emission reductions or removals, the outcome in terms of impact on net global GHG emissions is the same. Despite this, assertions that the use of carbon credits based on emission reductions is insufficient in the context of offsetting emissions for net-zero claims at sub-global scales are gaining acceptance. This article argues that such assertions are based on an incorrect setting of assessment boundaries and related misconceptions. Path choices for the share of carbon credit demand from emission reductions versus removals have important implications for the possibility to reach global climate goals and should be guided by the robust application of relevant GHG accounting principles. The results presented in this article have fundamental implications for what kind of GHG mitigation action may be considered adequate in relation to entities’ claims concerning making no contribution to net accumulation of GHG in the atmosphere.

Earth and environmental sciences/Climate sciences/Climate change/Climate-change mitigation

Earth and environmental sciences/Environmental sciences/Environmental impact

Through the adoption of the Paris Agreement, the signatory countries agreed to reach global peaking of greenhouse gas (GHG) emissions as soon as possible and to thereafter undertake rapid reductions to achieve a balance between anthropogenic emissions by sources and removals by sinks of GHGs by the second half of the century¹. Achieving a balance between emissions and removals on a global level is key to stabilising atmospheric GHG levels and attaining the long-term temperature goal of limiting global warming to well below 2°C and pursuing efforts to limit warming to 1.5°C compared to pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) has shown that reaching global net-zero emissions around mid-century is necessary to achieve this goal. The IPCC further states that deployment of carbon dioxide removal (CDR) to counterbalance “residual emissions” (i.e., hard-to-abate emissions that would be very expensive or impossible to eliminate) is unavoidable if net-zero emissions is to be achieved².

The origin of the concept of net-zero emissions is from physical climate science³. At a global scale, the definitions of net-zero GHG and CO₂ emissions are undisputable – any residual emissions must be counterbalanced by removals. The terms net-zero GHG (net-zero CO₂) emissions and GHG neutrality (CO₂ neutrality) are equivalent at a global scale². In only a few years, however, net-zero emissions has evolved from a physical climate science formulation into a central principle for climate action by entities on several levels, ranging from global to sub-national and corporate⁴. For example, 130 nations and 849 out of the largest 2000 publicly traded companies by revenue have set net-zero targets⁵. Among these groups, however, the term “net-zero” is used more or less interchangeably alongside several other terms such as “carbon-neutral” and “climate-neutral”, reflecting the lack of a universally adopted taxonomy for climate change mitigation targets on the sub-global scale.

On the sub-global scale, net-zero is not clearly defined. Traditionally, GHG neutrality or carbon neutrality has been achieved with limited – if any – internal emission reductions and instead relied entirely on offsetting. This has led to criticism since such practices are incompatible with pathways fulfilling the Paris Agreement’s goals⁶. In response, guidance on corporate net-zero has emerged to emphasise the role of reducing own value chain emissions. Current sub-global net-zero targets are heterogeneous in crucial aspects such as value chain coverage and use of carbon credits for offsetting purposes⁴. Offsetting refers to the use of carbon credits based on mitigation outcomes (MO, i.e., GHG emission reductions or removals) achieved outside of an actor’s value chain or relevant system boundaries, and making a unique claim of the MO, to counterbalance the climate impact of specific emissions, such as the carbon footprint of an actor, activity or product⁷. Attempts to distinguish between net-zero emissions and GHG neutrality on a sub-global scale have yet to reach consensus. In this article, the terms “net-zero emissions” and “GHG-neutrality” are used synonymously to denote a state in which an entity – across its full value chain – does not contribute to net accumulation of GHGs in the atmosphere.

Net-zero and GHG-neutrality standards and guidelines applicable at a sub-global scale are emerging^7–13. However, the meaning of net-zero emissions on the sub-global scale is still an ongoing discussion that needs to be resolved for entities to truly align their climate policies and actions to the goals of the Paris Agreement^14,15. There is a broad consensus that entities aiming for net-zero should prioritise deep and rapid emission reductions within their value chain, for example by following a 1.5 or 2°C-aligned emissions reduction pathway^{7–13, 15}. There is also a consensus that eliminating all emissions will be extremely challenging or impossible in many cases, and that there will thus be residual emissions that need to be offset^{7–13, 15}. Furthermore, there will be “remaining emissions” (i.e., emissions that are yet to be reduced and residual emissions) while on the transitional pathway towards the residual level. The use of carbon credits for offsetting remaining or residual emissions to achieve net-zero is an area where opinions diverge. Most agree that carbon credits need to fulfil certain quality criteria by, inter alia, being additional, quantified against a credible baseline, permanent and verified, and need to be issued within a carbon crediting programme^{7–9,11−13,15,16}. However, positions diverge on the roles of carbon credits emanating from activities that lead to GHG emission reductions versus removals as well as the need to avoid double claiming of the underlying MOs towards both corporate climate goals and countries’ climate targets¹⁴.

Some recent peer-reviewed publications on the topic of sub-global net-zero and the role of carbon credits from emission reductions versus removals argue that sub-global scale entities using carbon credits to deliver net-zero would need to purchase and use exclusively carbon removal credits (CRCs), and that emission reduction credits (ERCs) cannot deliver net-zero^3,4,17−19. Stakeholders engaged in emerging markets for CRCs have widely adopted this view^20–32. Some authors have argued the opposite view outside peer-review literature, namely that carbon credits have equal value towards net-zero claims on the sub-global scale, regardless of whether they originate from emissions reductions or removals. In addition, this literature argues that the notion that only CRCs can be used is based on an incorrect translation of the net-zero concept from the global to sub-global scales^14,33−35. This article analyses these opposing arguments on the roles of ERCs versus CRCs in sub-global scale entities’ strategies to align with the Paris Agreement target of achieving net-zero GHG emissions globally.

Accounting for GHG reductions and removals

Consequential GHG accounting can be used to answer to what extent a mitigation action reduces emissions. To evaluate a change in net GHG emissions, the boundary-setting principle of consequential accounting is to include “all and only” sources and sinks that are impacted by the choice of mitigation action³⁶. The requirement “all and only” recalls an important principle of GHG accounting which is completeness, meaning that omissions of relevant sources and double counting should be avoided³⁷. Only when the assessment boundary has been appropriately determined can the effect of a specific intervention be estimated³⁸. The GHG Protocol Policy and Action Standard (GHGPPAS) is a consequential accounting standard that provides a standardised approach for estimating the change in GHG emissions and removals resulting from interventions such as laws, standards, voluntary agreements and implementation of new practices³⁸. Figure 1 below illustrates the application of GHGPPAS to estimate the effect on GHG emissions to the atmosphere of an intervention that calls for exclusively offsetting remaining emissions in sub-global entities via CRCs, including mapping the casual chain and establishing the assessment boundary.

Considering a case in which a sub-global entity can choose to offset its remaining emissions using carbon credits emanating from GHG emission reductions or removals, the correct application of consequential accounting and applying the “all and only” principle, shows that the two options have the same limiting impact on the net accumulation of GHG in the atmosphere as compared to business as usual (BAU) (Fig. 2). This is because whichever option the entity choses, it simultaneously deselects the other option and the associated MO. Note the principle that only the offsetting entity has the right to claim the underlying MO of a carbon credit used in order to avoid double claiming. This principle applies to all examples in this paper.

Where things go wrong

The perception that sub-global scale net-zero targets must be achieved through offsetting remaining emissions with CRCs is widely represented in peer-review and grey literature^{3,4, 17–19,39}, and quite often accompanied by misleading graphics. Our literature review indicates that it is based on an inaccurate translation of net-zero requirements on the global scale to the sub-global scale and incorrect application of GHG accounting principles. The right-hand side of Fig. 3 below is commonly used to argue the superiority of CRCs compared to ERCs (occasionally referred to as the “math problem” since 1 + 0 = 1 and 1–1 = 0, which presumably attests to why CRCs are needed to deliver sub-global scale net-zero emissions)^{20–24, 30}. The left-hand side of Fig. 3 shows the error in setting the assessment boundary that results in such incorrect claims.

The Science Based Target initiative (SBTi) corporate net-zero standard requires residual emissions to be balanced by removals⁸. The same methodological error addressed in the previous paragraph leads the SBTi to conclude that offsetting residual emissions using ERCs is inconsistent with the criteria of no net accumulation of GHGs in the atmosphere, whereas offsetting using CRCs fulfils this criterion⁴⁰. This principle is adopted in the SBTi corporate net-zero standard, which requires residual emissions to be “neutralised” by removals to back up net-zero claims⁸. The flawed GHG accounting applied by the SBTi⁴⁰ is illustrated in Fig. 4, in which net emissions are affected by CRCs but not at all by ERCs. Figure 5 presents the correct comprehensive boundary, and shows that both the use of ERCs and CRCs are consistent with the criteria of no net accumulation of GHGs in the atmosphere. It is worth noting that several sub-global scale net-zero standards and guidelines similarly require that residual emissions shall be counterbalanced exclusively with CRCs^7,8,12,13, for net-zero claims. Versions of the “math problem” over time as illustrated in the right-hand side of Fig. 4 also appear in other grey literature^30,31,41.

In a net-zero or net-negative world

Some experts have argued that, once global emissions reach net-zero, there will be no scope to compensate for ongoing emissions by paying a third party to reduce their emissions^9,42. While the scope for using ERCs will gradually decrease as the potential for emission reductions decrease, that does not imply that 100 percent of offsetting must be based on CRCs even in a net-zero world (i.e. a world where only residual emissions remain which are counterbalanced by removals) or even in a net-negative world. The conclusion from the previous sections – that the impact on the net flux of GHGs to the atmosphere is the same regardless of whether one unit of GHGs is reduced or removed – is relevant in principle as long as there are any emissions.

Figure 6 illustrates that there can be a scope for offsetting based on ERCs even in a net-zero or net-negative world. In Case 1, the residual emissions from entities A and B are both counterbalanced by removals in entity C. MOs must be uniquely claimed, and therefore entity C must give up the right to claim the removals when selling CRCs to entities A and B. In Case 2, entity A purchases ERCs from entity B and uniquely claims them. Since entity B cannot claim the same MO, entity B purchases CRCs from entity C and uniquely claims the removal from entity C to uphold its net-zero status. The rationale behind entity A’s decision to purchase ERCs from entity B might be that entity A has a significantly higher marginal cost of reducing its own emissions than entity B, and that entity A is prepared to pay a price premium for “exclusive” ERCs compared to CRCs which enables the emission reduction in entity B. Currently, the opposite situation is true; some entities are prepared to pay a significant price premium for “exclusive” CRCs emanating from technical carbon removals⁴³, thereby contributing to the development and commercialisation of CDR methods. If CDR methods scale up massively and turn out to have significant trade-offs with other sustainability goals such as energy security and food production^44,45, there is a real possibility that buyers could consider paying a price premium for ERCs to reduce the quantity of CDR required globally.

What are considered residual emissions is likely to be a moving target⁴⁶. Limiting sub-global scale entities to offset residual emissions only using CRCs for making net-zero claims is not necessary and would effectively hinder potential benefits that could be delivered by a demand for and use of ERCs.

We have shown that offsetting remaining emissions via ERCs and CRCs to deliver sub-global scale net-zero has the same impact on net GHG emissions to the atmosphere. There are indeed, however, some inherent differences between the activities leading to emission reductions and removals. Clearly, only removals can deliver the neutralisation of residual GHG emissions that is necessary to reach net-zero on a global scale and, furthermore, enable globally net-negative GHG emissions in the second part of the century which will very likely be necessary to attain the Paris Agreement long-term temperature goal. Accumulated CDR deployment over the 21st century is substantial in most of the Paris Agreement-compliant scenarios, and deployment levels vary from hundreds to over a thousand gigatonnes in 1.5°C pathways². There is, however, very limited experience with CDR methods at significant scale and low confidence in their capability to remove several billion tCO₂ annually^47,48. Policies and funding are to date inadequate in relation to the future need for the multi-billion-ton scale of CDR. While governments, potentially inspired by strong coalitions of climate leaders, have to take responsibility for funding CO₂ removal at scale^49,50, carbon markets have the potential to create early market signals and support diffusion of CDR technology, thereby supporting development and deployment of CDR^9,51. Voluntary use of CRCs can contribute to that end⁵².

There are important challenges with prioritising CDR over emission reductions. Firstly, there is currently significantly more accessible potential for mitigation through emission reductions that can be realised at low cost compared to a substantial share of predicted CDR potentials^{34,35,53−54}. In other words, offsetting using ERCs can contribute to more mitigation per dollar spent compared to spending the same budget on CRCs. This is critically important given limited public and private climate finance flows, as well as the strain that war, pandemics and energy supply disruptions have placed on global progress towards climate goals. The faster and earlier that emissions are reduced on a global scale, to which the purchase of ERCs can contribute, the less total CDR will be required to reach the Paris Agreement goals^2,55. Limiting the future need for CDR is beneficial compared to relying on uncertain CDR methods⁵⁶, including trade-offs with other sustainability goals⁴⁴.

There are pros and cons associated with both ERCs and CRCs but both are needed. Identifying an appropriate balance between the two is an area that needs further research to provide guidance for actors on voluntary carbon markets (VCM). According to one estimate, the VCM could reach 50 billion US$ in 2030 and may thus make a sizable contribution to global decarbonization⁵⁷. Whatever balance between ERC and CRC transactions on the VCM might be most optimal, decisions by VCM actors should be guided by robust and comprehensive GHG accounting. In a recent public consultation and corporate road test for the Provisional Voluntary Carbon Markets Integrity Initiative (VCMI) Claims Code of Practice, 75 percent of respondents wanted claims to be differentiated based on credit types because of perceived different MOs associated with removal and reduction credits⁵⁸. This illustrates the importance and urgency of communicating relevant and accurate GHG accounting principles and the equivalent impact of ERCs and CRCs.

The methodology used for this paper is based on a review of existing literature and current guidelines and practices and the development of an assessment model, based on best available knowledge, which was subsequently used to assess greenhouse gas (GHG) accounting principles applied in current guidelines and practices. On the basis of the comparison, inconsistencies in the assessed current guidelines and practices were identified and, finally, improvements were suggested.

The literature review was performed in three stages. In the first stage, a comprehensive analysis was carried out of publications addressing net-zero (GHG) emissions and GHG-neutrality conceptually, including definitions, on the global and sub-global scales. In the second stage, a review was performed of literature covering GHG accounting which explicitly considers both GHG emission reductions and removals, including frameworks addressing global and sub-global scale net-zero and carbon neutrality goals and claims. These two stages of the literature review were complemented by a third stage, a review of literature covering general GHG accounting principles. In all stages of the literature review, particular attention was paid to definitions used and key elements of GHG accounting, such as scope and boundary setting, methods for calculating GHG balances, and reporting, in particular in the context of addressing GHG reductions and removals.

In the first stage of the literature review the focus was on broader international assessments and reports from multi-stakeholder initiatives. The aim of the review was to establish areas of broader international consensus concerning concepts and terminology that are relevant to the scope of the study as well as areas where international consensus has not been established. Literature to be included in the review was selected on the basis of expert solicitations as well as a stakeholder dialogue. Preliminary findings regarding concepts and terminology were reported in previously published reports.^14,15

In the second stage of the literature review, a keyword search was performed using the search engine Google Scholar and the keyword strings “corporate net zero” and “offsetting residual emissions”. Criteria for inclusion were: publication date 2018-2023 and that the publication addresses sub-global scale net-zero targets and offsetting practices to reach such targets. A total of 17 papers were covered. Furthermore, an online search for grey literature covering offsetting practices for sub-global scale net-zero targets was conducted to investigate stakeholder perspectives. International standards for sub-global scale carbon neutrality/net-zero targets were also considered. The literature review was terminated at the end of march 2023. Some of the publications covered are not included in the reference list of this article as they generated similar findings to other papers.

In the third stage of the literature review a keyword search was performed using the search engine Google Scholar and the keyword strings “greenhouse gas accounting”, “GHG accounting”, “carbon accounting”, “greenhouse gas accounting principles”, “GHG accounting principles”, “carbon accounting principles”. A total of 10 papers were covered. The stage three literature review resulted in three publications that provided a foundation for a science-based assessment model appropriate for the scope of our analysis.

An assessment model for adequately analysing the impact of GHG reductions and removals on the net accumulation of GHG in the atmosphere, in the context of sub-global scale GHG accounting, was developed on the basis of the best available knowledge, as identified through the literature review.

The assessment model was used to evaluate approaches used to analyse the impact of GHG reductions and removals on the net accumulation of GHG in the atmosphere, in the context of sub-global scale GHG accounting and net-zero targets and claims, as identified through the second stage of the literature review. On the basis of the evaluation, deviations from the assessment model were identified. Implications of the identified deviations were analysed in order to arrive at proposals how inadequate approaches may be improved.

In conclusion, the methodology described above provided an adequate and comprehensive approach to developing principles for GHG accounting that address GHG reductions and removals in the context of net-zero targets and claims on the sub-global scale. The principles provide a practical framework for GHG accounting that can be used by organisations of all sizes and sectors.

Data availability

Model documentation of the GHGP Policy and Action Standard can be found online [ref³⁸].

Acknowledgements

K.M. discloses support for the research of this work from the Swedish Energy Agency [grant number P2021-00016] and the Nordic Council of Ministers [grant number NKL 2128]. M.P discloses support for the research of this work from the Swedish Energy Agency [grant number P2021-00016]. H.M.A and R.S.F disclose support for the research of this work from the Nordic Council of Ministers [grant number NKL 2128]. The authors thank Stefan Grönkvist for his comments.

Author contributions

Möllersten, K. conceived and designed the analysis, performed the analysis and wrote the paper. Pehrs, M. collected the data, performed the analysis and wrote the paper. Ahonen, H-M. performed the analysis and wrote the paper. Spalding-Fecher, R. performed the analysis and wrote the paper.

Competing interest declaration

The authors declare no competing interests.

Correspondence

Correspondence and requests for materials should be addressed to Möllersten, K.

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Demystifying Carbon Removals in the Context of Sub-Global Net-Zero Targets

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Accounting for GHG reductions and removals

In a net-zero or net-negative world

Discussion

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References

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