A global,
independentscientificassessmentof Carbon
DioxideRemoval1st EDITION
A collaboration led by Stephen M Smith(University of Oxford), Oliver Geden(German Institute for Internationaland Security Affairs, SWP), Jan C Minx
(Mercator Research Institute on Global
Commons and Climate Change, MCC)
and Gregory F Nemet (University of
Wisconsin-Madison)

The State of Carbon Dioxide RemovalThis year’s report is led by the University of Oxford’s Smith School of Enterprise and theEnvironment and has been supported by:• CO2RE, a project funded by the UK’s Natural Environment Research Council (grant
agreement NE/V013106/1);• GENIE, a Synergy Grant funded by the European Research Council under theEuropean Union’s Horizon 2020 research and innovation programme (grant
agreement 951542);• CDRSynTra, a project funded by the German Federal Ministry of Education andResearch (grant agreements 01LS2101H and 01LS2101F);• ASMASYS, a project funded by the German Federal Ministry of Education andResearch (grant agreement 03F0898E);• with financial support from Carbon Gap and philanthropic support from the Bank ofAmerica;• and with analytical support from the International Institute for Applied Systems
Analysis (IIASA).

Project team
Convenors
This project has been devised and convened by experts in the field of Carbon Dioxide
Removal (CDR), who are authors of Intergovernmental Panel on Climate Change (IPCC)
reports and currently lead major CDR research projects:
Stephen M Smith (University of Oxford)
Oliver Geden (German Institute for International and Security Affairs, SWP)
Jan C Minx (Mercator Research Institute on Global Commons and Climate Change, MCC)
Gregory F Nemet (University of Wisconsin-Madison)
Authors
Chapter leads: Oliver Gedeni, Matthew Giddenii, William F Lambiii iv, Jan C Minxiii iv, Gregory F
Nemetv, Carter Powisvi, Stephen M Smithvi

Rob Bellamyvii
Max Callaghaniii
Annette Cowieviii
Emily Coxvi
Sabine Fussiii
Thomas Gasserii
Giacomo Grassiix

Jenna Greenev
Sarah Lückiii
Aniruddh Mohanx
Finn Müller-Hanseniii
Glen Petersxi
Yoga Pratamaii
Tim Repkeiii

Keywan Riahiii
Felix Schenuiti
Jan Steinhauserii
Jessica Streflerxii
Jose Maria Valenzuelavi

German Institute for International and Security Affairs, SWP
International Institute for Applied Systems Analysis, IIASA
iii
Mercator Research Institute on Global Commons and Climate Change, MCC
iv
University of Leedsv
University of Wisconsin-Madisonvi
University of Oxford
vii
University of Manchesterviii
New South Wales Department of Primary Industries/University of New England, Armidale, Australiaix
Joint Research Centre, European Commissionx
Princeton University
xi
CICERO Center for International Climate Researchxii
Potsdam Institute for Climate Impact Research, PIK
i

ii

2

The State of Carbon Dioxide Removal
Cite as: Smith, S. M., Geden, O., Nemet, G., Gidden, M., Lamb, W. F., Powis, C., Bellamy, R.,
Callaghan, M., Cowie, A., Cox, E., Fuss, S., Gasser, T., Grassi, G., Greene, J., Lück, S., Mohan,A., Müller-Hansen, F., Peters, G., Pratama, Y., Repke, T., Riahi, K., Schenuit, F., Steinhauser, J.,
Strefler, J., Valenzuela, J. M., and Minx, J. C. (2023). The State of Carbon Dioxide Removal 1st Edition. Available at: https://www.stateofcdr.org
We extend our thanks to the following people for their invaluable inputs in reviewing earlydrafts:Chad M Baum, Aarhus University
Holly Jean Buck, University at Buffalo
Wil Burns, Northwestern University
Isabela Butnar, University College London
Sylvain Delerce, CNRS
Nicklas Forsell, International Institute for Applied Systems Analysis (IIASA)
Mathias Fridahl, Linköping University
Robin Haunschild, Max Planck Institute for Solid State Research
Robert Höglund, Marginal Carbon
Matthias Honegger, Perspectives Climate Research
Jia-Ning Kang, Beijing Institute of Technology
Tim Kruger, University of Oxford & Origen
Niall Mac Dowell, Imperial College London
Alexander Mäkelä, Carbon Gap
Christine Merk, Kiel Institute for the World Economy
Eli Mitchell-Larson, Carbon Gap & Oxford Net Zero
James Irungu Mwangi, Climate Action Platform Africa
Anne Olhoff, CONCITO – Denmark’s Green Think Tank
Pete Psarras, University of Pennsylvania
Nan Ransohoff, Stripe
Artur Runge-Metzger, MCC

Lead institutions:

Funders:

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The State of Carbon Dioxide Removal
Editing & design
Lead Editor: Roz Pidcock (Exalt Editing)Managing Editor: Kate Heath (independent)
Co-design process for visual identity & Executive Summary figures: Angela Morelli(InfoDesignLab)
Report layout design: Liliana Resende (University of Oxford)
Graphics support: Nigel Hawtin (nigelhawtin.com)
Website design and communications support: George Hope (University of Oxford)
The views, opinions, findings, and conclusions or recommendations expressed in this report arestrictly those of the authors. They do not necessarily reflect the views of funders or editors, whobear no responsibility for any errors or omissions in, or for the correctness of, the information
contained herein, nor for any use that may be subsequently made of this.

4

The State of Carbon Dioxide Removal

The State of CDR 2022 | Contents
Foreword

6

Executive Summary8

Chapter 1 - Introduction

14

Chapter 2 - Research landscape

26

Chapter 3 - Innovation

35

Chapter 4 - Public perceptions

46

Chapter 5 - Policymaking

65

Chapter 6 - Deployment

70

Chapter 7 - Scenarios

79

Chapter 8 - The CDR gap

91

Chapter 9 - Future assessments

104

References

107

5

The State of Carbon Dioxide Removal

Foreword
The science is clear. No matter which IPCC pathway humanity will
follow, holding the global average temperature increase below
1.5°C will require removing increasing amounts of CO2 from theatmosphere. Firstly, hard-to-abate greenhouse gas emissions will
have to be balanced with removals in order to achieve net-zero CO2emissions in less than thirty years. Secondly, from then onwards,
vast amounts of CO2 will have to be captured from the air for many
decades, cleaning up the atmosphere and returning atmospheric CO2
to climate-safe levels. At the latest by then, carbon dioxide removal(CDR) and the sustainable management of global carbon cycles will
have become the major focus of climate action worldwide. In thisimmense global clean-up exercise, everyone will have to assume their
historical responsibility.
However, CDR will not fall from heaven like manna. It will require
active and urgent public policies. Novel CDR, such as direct air
capture and storage, enhanced weathering and new carbon-richmaterials, are still at an early stage of development and will thus
require a significant push. Deployment at scale, even of well-known
conventional CDR on land, will require a CO2 price incentive and an
adequate regulatory framework. Without strong public governance,
CDR could be implemented in a way that undercuts emission
reduction efforts or harms the environment.
This report, the first of its kind, updates the world on the state of playon CDR: from research to policymaking to deployment, from scientificanalysis to public perception. Not surprisingly, the scientists point
their fingers at yet another yawning gap between, on one side, thescientifically assessed need and, on the other side, the lack of action
on CDR along the entire value chain. The CDR gap calls for urgent
action on all CDR fronts.
For me, this report points towards practical recommendations
which, over the coming months, will hopefully trigger domestic andinternational CDR action:
I. National climate policy frameworks will have to be expanded
to scale up CDR. Specific policy support will have to be created
to, on the one hand, incentivise CDR, and on the other,ensure that it is done well through monitoring and good public
governance.
II. At the next international climate conference in Dubai at theend of 2023 (COP28), there must be explicit acknowledgementof the magnitude of the CDR gap under the Global Stocktake,creation of a new negotiation track on CDR, clear transparency
rules for national reporting of CDR and its inclusion in

6

The State of Carbon Dioxide Removal
Nationally Determined Contributions, and identification ofinternational climate finance requirements for CDR, taking into
account the “polluter pays” principle.
III. In parallel, public and private leaders should fast-forward
practical action on CDR together – very similar to the successstory I experienced in relation to renewables. Then, thecreation of REN21 as an ambitious coalition in 2004 turned
out to be instrumental in pushing the frontiers on renewables
technology and policy, both internationally and domestically.
In the coming years, this global CDR report should continue
to regularly inform policymakers on the state of progress, bysystematically collecting and analysing the vast amount of data anddevelopments in many parts of the world.

Artur Runge-Metzger
Former Director, European Commission, Directorate-General for
Climate Action

7

The State of Carbon Dioxide Removal

Executive Summary
Scaling up Carbon Dioxide Removal (CDR) is an urgent priority, as are efforts to rapidly
reduce emissions, if we are to meet the temperature goal of the Paris Agreement. Scenarios
for limiting warming to well below 2°C involve removing hundreds of billions of tonnes ofcarbon dioxide (CO2) from the atmosphere over the course of the century. Drawing together
analysis across several key areas, this report is the first comprehensive global assessmentof the current state of CDR.
We find a gap between how much CDR countries are planning and what is needed in
scenarios to meet the Paris temperature goal. The size of the “CDR gap” differs acrossscenarios, depending on how we choose to transform the global economy towards net-zeroemissions. However, there are currently few plans by countries to scale CDR above current
levels, exposing a substantial shortfall.
CDR involves capturing CO2 from the atmosphere and storing it durably on land, in theocean, in geological formations or in products. Examples include reforestation, biochar,
Bioenergy with Carbon Capture and Storage (BECCS) and Direct Air Carbon Capture andStorage (DACCS). For the first time, this report compiles an estimate of the total amount of
CDR currently being deployed around the world.
Almost all current CDR (2 GtCO2 per year) comes from “conventional” CDR on land, primarily
via afforestation, reforestation and management of existing forests. Scenarios that limit
warming to 1.5°C or 2°C require further increasing current forest sinks, as well as minimisingemissions from deforestation. By 2050, land-based removals approximately double in 1.5°C
pathways and increase by around 50% in 2°C pathways compared to 2020 levels. In the nearterm, several countries plan to maintain or slightly increase conventional CDR on land by2030, which is on its own a huge challenge requiring dedicated policies and management.

Only a tiny fraction of all current carbon dioxide removal results from novel methods
Total current amount of carbon dioxide removal, split into conventional and novel methods (GtCO2/yr)
-2

-1.8

-1.6

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0 GtCO2/yr

Almost all current carbon
dioxide removal, 2 GtCO2/yr,comes from conventional
management of land and a tiny
fraction, 0.002 GtCO2/yr,
results from novel methods
BECCS
Biochar
Other novel CDR-0.003-0.002-0.001

8

0 GtCO2/yr

The State of Carbon Dioxide Removal
Carbon dioxide removal is a feature of all scenarios that meet the Paris temperature goal, in addition to
reducing emissions
Carbon dioxide removal (GtCO2/yr), in 2020 and in three Paris-consistent scenarios
GtCO2/yr
0

2020

2030

2040

2050

-2

-4
Virtually all current
carbon dioxide
removal, 2 GtCO2/yr,comes fromconventional
management of landand only a tiny
fraction results fromnovel methods-6

Focus on Demand Reduction
48% greenhouse gas reduction
by 2030

Focus on Renewables
31% greenhouse gas reduction
by 2030-8

Almost all Paris-relevant scenarios
feature carbon dioxide removal, but
we can limit our future reliance on it
by reducing emissions faster-10

Focus on Carbon Removals
33% greenhouse gas reduction
by 2030-12-14

There is a gap between proposed levels of carbon dioxide removal and what is needed to meet theParis temperature goal
Carbon dioxide removal (GtCO2/yr), proposed levels compared to three Paris-relevant scenarios in 2030 and 2050

GtCO2/yr-2level in 2020, -2-3

focus ondemand reduction
3.5

-4
-5
-6

focus onrenewables
7.6

2050
focus oncarbon removals
9.8

focus ondemand reduction
4.7
long-term strategies, 2.9

-1

2030
focus oncarbon removals
3.9

countries’ pledges, 2.6

0

focus onrenewables
5.4

Closing the gap requires
scaling up carbon dioxide
removal, particularly rapidly
in the next decade

-7
-8
-9
-10

9

The State of Carbon Dioxide Removal
Virtually all scenarios that limit warming to 1.5°C or 2°C require “novel” CDR, such as BECCS,
biochar, DACCS, and enhanced rock weathering. However, only a tiny fraction (0.002 GtCO2
per year) of current CDR results from novel CDR methods. Closing the CDR gap requires
rapid growth of novel CDR. Averaging across scenarios, novel CDR increases by a factor of
30 by 2030 (and up to about 540 in some scenarios) and by a factor of 1,300 (up to about
4,900 in some scenarios) by mid-century. Yet no country so far has pledged to scale novel
CDR by 2030 as part of their Nationally Determined Contribution, and few countries have so
far published proposals for upscaling novel CDR by 2050.

There is a gap between proposed levels of carbon dioxide removal and what is needed to meet theParis temperature goal
A. Conventional carbon dioxide removal (GtCO2/yr), proposed levels compared to three Paris-relevant scenarios in 2030 and 2050

GtCO2/yr-2level in 2020, -2

-3

2050
focus ondemand reduction-3.5

focus onrenewables-6.7

focus oncarbon removals-6.3

focus ondemand reduction-4.7
long-term strategies, 2.3

-1

2030
focus oncarbon removals-3

countries’ pledges, 2.6

0

focus onrenewables
-5.3

-4

Closing the gap between proposedlevels of carbon dioxide removals
and what is needed to meet theParis temperature goal requires
scaling up conventional carbon
dioxide removal on land

-5
-6
-7

B. Novel carbon dioxide removal (GtCO2/yr), proposed levels compared to three Paris-relevant scenarios in 2030 and 2050

GtCO2/yr

-2
-3

2030
focus oncarbon removals-0.9

focus ondemand reduction
0

A few scenarios involve no novel
carbon dioxide removal, but
require even more aggressive
emissions reductions which weare not on track to achieve

-4
-5
-6
-7

10

focus onrenewables
-0.9

2050
focus oncarbon removals-3.4

focus ondemand reduction
0
long-term strategies, 0.6-1countries’ pledges, 0level in 2020, 00

focus onrenewables-0.1

The State of Carbon Dioxide Removal
CDR is not a silver bullet, as scenarios that limit warming to 2°C or lower require deep
cuts to emissions in addition to, not in place of, CDR. A few scenarios do meet the Paris
temperature goal without novel CDR, but these require even more aggressive emission
reductions, which we are not on track to achieve. To help manage uncertainties and risks
associated with CDR at large scales, our dependence on it should be limited by reducing
emissions faster.
Spurring the rapid growth in CDR necessary to close the CDR gap requires urgent andcomprehensive policy support that is tailored to specific national contexts. Over 120 national
governments have a net-zero emissions target, which implies using CDR to counterbalance
residual emissions, but only a few explicitly integrate CDR into their climate policies. The next
decade is crucial for novel CDR, in particular, since the amount of CDR deployment requiredin the second half of the century will only be feasible if we see substantial new deployment
in the next ten years, novel CDR’s formative phase. Yet our assessment reveals few countries
have actionable national plans to develop CDR, particularly for novel methods.
In terms of recent growth, our assessment of trends in the scientific literature, innovation andpublic perception of CDR reveal some interesting patterns as CDR evolves. The peer-reviewed
scientific literature on CDR is growing faster than for climate change as a whole, now
consisting of over 28,000 English-language studies. Most focus on land-based biological CDR
methods such as biochar and soil carbon sequestration. Almost all are published in science andtechnology journals, with very few in social sciences or humanities publications, and only abouta third have a specific geographic focus. This indicates a potential lack of information tailored to
specific local contexts, particularly for novel CDR methods.
Innovation in CDR has expanded substantially in recent years. We see evidence of this inover $4 billion of publicly funded Research, Development and Demonstration (RD&D), a risein patents (with China the lead country and Direct Air Capture the most patented technology)
and investment in new CDR capacity totalling approximately $200 million from 2020 to2022. CDR is becoming more of a public talking point too, although awareness remains low
relative to other aspects of climate change. A growing number of scientific studies on how
people perceive CDR indicate public support for research into CDR but raise concerns about
deployment at scale. CDR methods that are familiar and often perceived as natural, such asafforestation, are viewed more favourably than others. Discussion of CDR on the social media
platform Twitter is growing fast, with a trend towards more positive sentiment for all CDR
methods except BECCS.
The primary policy implications of this first assessment of the state of CDR are thatmeeting the Paris temperature goal requires us to accelerate emission reductions, increase
conventional CDR and rapidly scale up novel CDR. Actionable policy proposals, withstandardised transparent reporting and involving societal deliberation, will support and shapethese outcomes in a manner that acknowledges both the urgency of the challenge and issues
such as policy costs, hazards and land-use conflicts.

11

The State of Carbon Dioxide Removal
We intend for this report to be the first in a series, continuing to track the CDR gap andproviding a clear, authoritative, and up-to-date snapshot and serving as an information
resource for those who are making decisions about CDR and its role in meeting climate goals.
We have identified areas on which future assessments can build, including: (1) expanding
the community of experts and data sharers to widen the knowledge, perspective andexperiences that guide development of CDR; (2) improving the availability of data on CDR
projects, plans, investment and other relevant dimensions; and (3) honing the analysis aroundmore complete, consistent and comparable definitions and methods.
Twenty years ago, renewable energy was a niche sector. Today, the picture is radicallydifferent. This rapid development was enabled in part by concerted efforts to build
institutions and communities for gathering and sharing information. CDR is at the start of asimilar journey. We, the scientific convenors, hope that this contribution, in addition to thecontributions of many others, provides similarly important guidance so that CDR too can play
an important role in addressing climate change.

12

“We define CDR as capturing CO₂
from the atmosphere and storing
it away for decades to millennia.”

The State of Carbon Dioxide Removal

Chapter 1 | Introduction
Chapter team: Stephen M Smithi, Annette Cowieii
iii

University of Oxford
New South Wales Department of Primary Industries/University of New England, Armidale, Australia

This report is the first independent scientific assessment tracking the global developmentof Carbon Dioxide Removal (CDR). This chapter sets out how we define CDR and thecharacteristics of key CDR methods.

1.1 Carbon Dioxide Removal in the context ofclimate goals
Alongside rapidly reducing emissions, we will need to remove carbon dioxide from theatmosphere to meet climate goals.
Climate change is mainly being driven by emissions of carbon dioxide (CO2) to theatmosphere. These emissions come from human activities such as fossil fuel burning, landuse changes and industrial processes. Meeting the Paris temperature goal (Box 1.1) requires
deep and widespread reductions in emissions. While such efforts to reduce emissions
prevent further CO2 and other greenhouse gases (GHGs) from going into the atmosphere,
Carbon Dioxide Removal (CDR) involves taking CO2 out of the atmosphere that is alreadythere.
CDR can fulfil three major functions, alongside emissions reductions. First, CDR can reduce
net emissions in the near term. Second, CDR can counterbalance residual emissions toachieve net-zero CO2 or GHG emissions in the medium term. Third, if removals exceed
emissions, CDR can achieve net-negative emissions in the longer term. At the global
level, net-negative CO2 emissions could reverse at least some overshoot, where global
temperature increase exceeds acceptable levels.1

Box 1.1 Climate goals
Through the Paris Agreement, countries have together set quantifiable goals to reduce (or“mitigate”) climate change. The principal goal is defined in terms of temperature:

Holding the increase in the global average temperature to well below 2°C above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5°C above
pre-industrial levels.
In support of this long-term temperature goal, the Paris Agreement further sets out a goalfor emissions and removals:

to achieve a balance between anthropogenic [i.e. human-caused] emissions by sources
and removals by sinks of greenhouse gases in the second half of this century, on the basisof equity, and in the context of sustainable development and efforts to eradicate poverty.

9The State of Carbon Dioxide RemovalThis balance of emissions and removals from human activity is often referred to as “netzero emissions”. Over 120 countries have now pledged their own domestic net zerotargets (see Chapter 5 – Policymaking), as have many companies.2
Net-zero emissions targets, including the target in the Paris Agreement, are usually applied
to a basket of greenhouse gases rather than to CO2 alone. In the case of a greenhouse gas
target, the definition of net zero requires a way to compare the emissions and removals of
the different gases. Depending on the way chosen, net zero may involve different balancesof greenhouse gases and hence may lead to global temperature decreasing, or evencontinuing to increase, over subsequent decades.
For ease of readability, in this assessment we refer to the long-term temperature goal in
the Paris Agreement (well below 2°C above pre-industrial levels, pursuing efforts to limit
the increase to 1.5°C) as “the Paris temperature goal” but use more specific terminology
where necessary.

1.2 Purpose and scope of this report
Drawing together analysis across several key areas, this report is the first step towards a
global assessment of the state of CDR.
The topic of CDR is moving rapidly up the agendas of policymakers, investors, researchersand environmental campaigners. Consequently, information about CDR is increasing, including
academic assessments3–5, introductory books6,7, data on CDR startups, purchases of carbon
removal credits8, recommendations from business groups9 and briefings from NGOs10.
Yet, to date, there are still major limitations in information regarding CDR:
• Despite growing recognition that CDR needs to be scaled, there is no current global
effort to quantify the amount of CDR currently deployed, and whether it is on track
to meet the Paris temperature goal.
• Information on CDR is highly dispersed, often gathered using inconsistent definitions
and methods, and without regular updating to keep pace with developments.
• Growing political and private sector interest in CDR makes it crucial to establish an
independent and scientific assessment of the state of CDR and the size of any gap
to be closed.
This report is the first such assessment. Based on publicly available data, we assess CDRdevelopment in several key areas. In the first three chapters we assess CDR in terms ofscientific research (Chapter 2), innovation (Chapter 3) and public perception (Chapter 4).
Then, we examine different policy approaches and commitments by governments to develop
CDR (Chapter 5). The subsequent three chapters look at the amount of CDR being deployednow (Chapter 6), the amount required in pathways that meet the Paris temperature goal
(Chapter 7) and the gap that exists between current deployment, government pledges
and these pathways (Chapter 8). Finally, we highlight future directions for improving and

10

The State of Carbon Dioxide Removal
deepening this assessment (Chapter 9).
It is our intention that this report is the first in a series: continuing to track the CDR gap,
expanding the breadth and depth of the assessment to be truly global in scope, and building
a community around making CDR data more complete, reliable, accessible and inclusive.
We intend this report to provide a clear, authoritative and up-to-date snapshot, serving
as an information resource for people making decisions about CDR and its role in meetingclimate goals. In addition, we intend that future assessments will be accompanied by a freely
available data portal for use by anyone with an interest in CDR.

1.3 What we mean by CDR
We define CDR as capturing CO2 from the atmosphere and storing it away for decades tomillennia.
For the purposes of this assessment we adopt the definition of CDR used by theIntergovernmental Panel on Climate Change (IPCC)11:
Human activities capturing CO2 from the atmosphere and storing it durably in geological, land or ocean reservoirs, or in products. This includes human enhancement of
natural removal processes, but excludes natural uptake not caused directly by humanactivities.
Our definition of CDR thus follows three key principles:
Principle 1: The CO2 captured must come from the atmosphere, not from fossil sources(see Box 1.2). The removal activity may capture atmospheric CO2 directly or indirectly, forinstance via biomass or seawater.
Principle 2: The subsequent storage must be durable, such that CO2 is not soon reintroduced
to the atmosphere (see Section 1.4).
Principle 3: The removal must be a result of human intervention, additional to Earth’s naturalprocesses.
It is important to distinguish CDR from other related terms and concepts, such as Carbon
Capture and Utilisation (CCU), and Carbon Capture and Storage (CCS). While they sharesome components with CDR, they do not necessarily result in durable net removal of CO2
from the atmosphere (Box 1.2). Examples of how different approaches meet, or fail to meet,the principles of CDR are shown in Figure 1.1.

11

The State of Carbon Dioxide Removal

Box 1.2 Differentiating CCS, CCU and CDR
To count as Carbon Dioxide Removal (CDR), a method must be an intervention which
captures CO2 from the atmosphere (Principle 1) and durably stores it (Principle 2).
Carbon Capture and Storage (CCS) is a set of industrial methods for the chemical captureof CO2, concentration of this into a pure stream and its subsequent geological storage.
Where the CO2 comes directly from fossil fuels or minerals (for example, limestone),this process does not meet Principle 1 and counts as an emissions reduction rather than
CDR. Indeed, the term CCS is sometimes reserved only for these applications. CCS can,however, be applied to CO2 streams generated using biomass or directly from the air, inwhich cases the overall process meets both Principle 1 and Principle 2, and counts as
CDR. In this assessment we refer to “fossil CCS”, where necessary, to distinguish this from
CCS as a component of CDR methods.
Carbon Capture and Utilisation (CCU) is a set of industrial methods for the chemical
capture of CO2 and its conversion into products. These products can include carbonateddrinks, fuels, plastics and aggregates. If this CO2 comes from the atmosphere, then it
meets Principle 1. Many of these products, however, last only a matter of days or months
before the carbon is released into the atmosphere. Only some involve durable storage,
thereby meeting Principle 2. Furthermore, if the captured CO2 comes from fossil ormineral sources, this again counts as a (temporary) emissions reduction rather than CDR.
Carbon Dioxide Removal (CDR) must involve both capture of CO2 from the atmosphereand durable storage, whether in a useful product or another carbon reservoir. Not all CCS
and CCU methods involve CO2 removal from the atmosphere or lead to durable storage.

CO2

CO2
Atmosphere

CO2
Atmosphere

AtmospherePrinciple 1

Principle 1

Direct air capture

Principle 2
Carbon capture and storage

Forestry

Fuel use

Principle 1

Principle 2

Principle 2
Biological storage

Geological storage
Stored carbon is extracted

CO2 stored

CO2 stored

Figure 1.1. To be defined as Carbon Dioxide Removal (CDR), a method must capture CO2 from the atmosphere(Principle 1) and durably store it (Principle 2). An example of a method which satisfies both principles, and hence
qualifies as CDR, is afforestation/reforestation (left). There are several approaches that satisfy only one of theseprinciples, and hence are not CDR, but which count as Carbon Capture and Utilisation (e.g. Direct Air Capture tofuels (middle) or as fossil Carbon Capture and Storage (right). Source: Zero Emissions Platform (2020)12.

12

The State of Carbon Dioxide Removal

1.4 Building blocks of CDR
There are different ways to capture CO2 from the atmosphere and different ways to store
it. Some means of storage are longer-lasting and less vulnerable to reversal than others.
Individual CDR methods can be thought of as different routes through the Earth’s carbon
cycle – capturing carbon from the atmosphere and transferring it to a durable carbon pool(see section below, Box 1.3 and Figure 1.2).
Routes through the carbon cycle
CDR methods encompass a range of capture processes and storage pools. Processes whichcarry out the initial capture from the atmosphere are often referred to as sinks. Between
capture and ultimate storage, carbon may be converted and transferred through a numberof carbon pools. Some methods involve multiple steps, while others combine capture andstorage in a single step.
Capture processes
Biological capture. Through the process of photosynthesis, CO2 is taken up from theatmosphere by trees, crops and aquatic biomass such as kelp and seagrasses.
Geochemical capture. A range of minerals can bind atmospheric CO2, as can alkaline wastematerials from construction and industry. The CO2 is bound in the form of solid carbonate(which can be used as a product, such as aggregates) or dissolved bicarbonate, both of which
are durable carbon pools.
Chemical capture. CO2 can be captured directly from air using chemical solvents and sorbents
designed to re-release it as a concentrated CO2 stream for use or storage.
Storage processes
Biological storage (on land and in oceans). While annual plants do not retain carbon durably,
trees can retain their carbon for decades, centuries or more. Soils and wetlands are a further
store of carbon, derived from compounds exuded by roots and dead plant matter. In theoceans, aquatic biomass may sink to the ocean floor and become marine sediment. Carbon
can be retained durably in these ecosystems, especially if managed carefully to reduce
disturbances.
Product storage. Many carbon-based products do not constitute durable storage. However,construction materials and biochar (a carbon-rich material produced by heating biomass inan oxygen-limited environment) can store carbon for decades or more. These carbon-based
products can be made from conversion of harvested biomass (in the cases of biochar andwood in construction), from concentrated CO2 streams or even from CO2 from ambient air(in the case of aggregates).
Geochemical storage. Concentrated CO2 can be stored in geological formations, using
depleted oil and gas fields or saline aquifers, or reactive minerals such as basalt. Geochemical
capture leads directly to long-term storage of CO2 in the form of carbonate minerals orbicarbonate in the ocean.

13

The State of Carbon Dioxide Removal

Atmosphere

Land

Products

Ocean

Crops

Concentrated CO2

Dissolved CO2Agri & forest residues

Fuels & chemicals

Aquatic biomass

Trees

BiocharMarine sediment

Wetlands

Aggregates

Bicarbonate

Soils

Wood in construction

Lithosphere

Depleted fossil fuelreservoirs

Saline aquifers

Minerals

Figure 1.2. The global carbon cycle consists of five main carbon reservoirs: the atmosphere,

land, products, ocean and lithosphere (geological formations). Within each reservoir there arevarious carbon pools (indicated in each reservoir) whose characteristics vary in terms of storage
capacity and durability. Carbon Dioxide Removal methods transfer CO2 from the atmosphere
into other durable pools within the global carbon cycle.
Durability
Different carbon pools have very different characteristic timescales for storage andrisks of reversal, and there is no clearly agreed definition of durability (Box 1.3). Wellchosen geological and mineral formations offer the longest and least reversible storage.
Nevertheless, choosing to include only these methods excludes others widely regarded asvalid CDR, such as those that store carbon in trees, biochar and soils.
In this assessment we choose to define CDR methods as sufficiently durable if the carbon
pool used for storage has a characteristic timescale on the order of decades or more. The
list of CDR methods that we have included in this assessment matches that used by the
IPCC13, including wood products used in construction such as panels and sawnwood (Table
1.1). These construction products characteristically store carbon for decades after having
captured it during tree growth14. Furthermore, at the end of their use as products, the carbon
could be transferred to another more durable store, for instance if used for Bioenergy with
Carbon Capture and Storage (BECCS).
It should be kept in mind that our approach to what counts as CDR is not definitive – we
expect that expert interpretations will evolve as research continues.

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The State of Carbon Dioxide Removal

Box 1.3 Defining durable storage
The temperature-raising effect of fossil CO2 emissions lasts for millennia. This is an
important consideration in any effort to balance emissions and removals. Any storage
for shorter than this very long timescale will only partially counterbalance fossil CO2
emissions15. Maintaining net-zero emissions – and hence halting the global temperature
increase – requires any residual emissions of fossil carbon to be balanced by storage on
the same millennial timescale16.
There is currently no clear scientific basis for a threshold of durability to define Carbon
Dioxide Removal (CDR), nor consensus among policymakers. Despite storage for millennia
being the gold standard, there are practical barriers to assuring projects for this long.
Furthermore, shorter-term storage still has some value for meeting climate goals, although
it is widely accepted that products which re-release carbon within a year (such as Direct Air
Capture to fuels, or biomass to food) are not CDR. Existing policies by governments andvoluntary standard-setters have various minimum thresholds for storage, ranging from 25
years up to 100 years, sometimes with discounted credits issued for shorter thresholds17,18.
Figure 1.3 shows the characteristic storage timescales of various carbon pools. The actual
duration of storage depends not only on the characteristic timescale of a pool but also
on human factors: storage in soils can be ended by a change in land use but can also be
extended through careful maintenance. Geological formations (saline aquifers, depleted
oil and gas fields, and minerals) have the longest characteristic timescales and are leastsusceptible to releasing CO2 into the atmosphere as a result of human and natural
disturbances. They are therefore most able to provide a like-for-like balance to emissionsof fossil CO2.
Trees & soils

Storage type

Wood in construction

BiocharMarine sediment

Geological formations

Minerals

1

10

100

1,000

10,000100,000

Characteristic timescale (years)

Figure 1.3. The durability of different carbon storage pools ranges from decades to tens of millennia. Note thatthese timescales are indicative, assuming no premature disturbance. Source: IPCC WG3 AR6 Chapters 7 & 1213,19.

In this assessment we define durability based on the characteristic timescale of thestorage pool used. We count a method as CDR if the characteristic timescale of storage ison the order of decades or more.

15

The State of Carbon Dioxide Removal

1.5 CDR methods in this assessment
What counts as CDR will continue to evolve as methods develop, research continues andkey definitions are agreed.
The variety of capture and conversion processes and storage options means there are manydifferent potential CDR methods. Table 1.1 provides a list of methods based largely on the
research literature summarised by the most recent IPCC assessment13. As well as providing
the method names we use throughout the report, the table summarises the specific route
through the carbon cycle that each method employs; its stage of development (or Technology
Readiness Level, TRL); its estimated costs at scale; its mitigation potential (the maximum
potential to both remove atmospheric CO2 and displace emissions in 2050 – by replacing
emissions-intensive products and processes – considering biophysical and technological limits
but not economic, environmental, socio-cultural or institutional constraints); its key potential
hazards and co-benefits; and the feasibility of monitoring, reporting and verification (MRV).
Based on this review of the research literature, aspects of many CDR methods are highly
uncertain. This is particularly true for the mitigation potential and costs of methods at lower
TRLs, as illustrated by the wide ranges provided in Table 1.1. Furthermore, MRV of the
net carbon removal can be challenging, and hazards and co-benefits can be highly contextspecific, particularly for methods involving the land and ocean.
We use this set of CDR methods as a template throughout the assessment, but two caveats
should be kept in mind:• While based on a comprehensive survey of the scientific literature, it is not a fullycomplete set, even in the present day. For instance, in our analysis of innovation(Chapter 3) and deployment (Chapter 6) we note the use of an additional method,
converting biomass to bio-oil injected into geological storage. Over time, we expect
more CDR methods to develop.
• Not all the analyses we draw from include all these methods on a consistent basis.
For instance, the methods used to analyse innovations (Chapter 3) focus on components such as Direct Air Capture, rather than on full CDR systems. This reflects thecurrent lack of consistent approaches across the expert community. In the chaptersthat follow, we make clear which are included.
Given the number of CDR methods, they are often grouped into categories for easeof reference. A common grouping is between “natural” methods and those that are“technological” or “engineered”20. This categorisation is contested, however, and blurred (athird “hybrid” category is frequently employed to cover methods in between)21. Methods
which protect, restore or manage ecosystems while delivering other benefits are termed“nature-based solutions” by some22, while methods which involve a variety of biomass uses
coupled to durable storage have been called “biomass carbon removal and storage (BiCRS)”
by others23. There are a variety of ways in which CDR methods can be grouped, and no
single agreed way – indeed, different groupings may be useful in different contexts.
In this assessment we refer to individual methods, where possible, or group them by common
measurable properties if necessary. In comparing current CDR deployment with futurecommitments and scenarios, we group CDR methods into two broad categories, “conventional
CDR on land” and “novel CDR”. This is based on a combination of their current level of readiness,the scale at which they are currently deployed, and the type of carbon storage they employ:

16

The State of Carbon Dioxide Removal

Conventional CDR on land: Methods that both capture and store carbon in the land reservoir.
They are well-established practices already deployed at scale (TRL 8–9) and widely reported
by countries as part of their Land Use, Land Use Change and Forestry (LULUCF) activities. The
methods we include in this group are: afforestation/reforestation; soil carbon in croplands andgrasslands; peatland and wetland restoration; agroforestry; improved forest management; anddurable Harvested Wood Products. While the latter stores carbon in the product reservoir, we
include it here because it is already deployed at scale and the carbon remains as biomass.
Novel CDR: All other methods, storing captured carbon in the lithosphere (geologicalformations), ocean or products. Generally at a TRL below 8–9, these methods are currently
deployed at smaller scales (see Chapter 6 – Deployment). Examples include BECCS, Direct
Air Carbon Capture and Storage (DACCS), biochar and ocean alkalinisation.
In future assessments we aim to improve the consistency of categorising methods andincorporate new methods as they develop.

17

The State of Carbon Dioxide Removal
Table 1.1. Summary of Carbon Dioxide Removal (CDR) methods, the route through the carbon cycle that they employ, their Technology Readiness Level (TRL), their costand global mitigation potential estimated for 2050, their key hazards and co-benefits, and the feasibility of monitoring, reporting and verification (MRV) of net carbon dioxide
removal. TRL ranges from 1 for a technology which exists only in terms of basic outlined principles to 9 for operationally proven systems. Costs at scale and mitigation potentials
are judgements based on the literature; these are particularly uncertain for methods with a TRL around 7 and below. MRV is assessed for both capture and storage steps, scoring
the simplicity/precision of quantifying the amount of carbon removed (low/med/high/v high, based on author judgement) and the existence or not of an MRV methodology in theIntergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories (yes/no). Hazards and co-benefits listed here are not exhaustive andare often context specific. Sources: 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories14; IPCC WG3 AR6 Chapter 12, Table 12.613, which
presents the synthesis of available literature by the IPCC authors at the time of preparation of their report, in 2021.

MethodRoute of CDR*

TRL

Cost atscale($/tCO2)

Mitigation
potential(GtCO2/yr)

MRV

Example hazards

Example co-benefits

DACCS (Direct
Air Carbon
Capture andStorage)(Chemical capture via solid
sorbent or liquid solvent) ->(Concentrated CO2 stream) ->(Storage in lithosphere)6

100 - 300

5-40

Capture: v high,noStorage: high,yes

Increased energy use can lead to greenhouse gas
emissions or competition for renewable energy.
Increased water use with some options.

Water produced (solid sorbent Direct Air Capture
designs only).

Enhanced rockweathering(Geochemical capture via
spreading crushed silicate rocks
on land or ocean) -> (Storage inminerals or as bicarbonate)

3-4

50 - 200

2-4

Capture: low, no
Storage:low, noMining impacts; air quality impacts of rockdust when spreading on land. Heavy metal
contamination, especially nickel and chromium,from some rock types.

Reduced soil acidity and increased nutrient supply,
which can enhance plant growth and soil carbon
sequestration.

Ocean
alkalinisation(Geochemical capture via
adding alkaline materials tothe ocean such as silicate or
carbonate rocks) -> (Storage inminerals or as bicarbonate)

1-2

40 - 260

1-100

Capture: low, no
Storage: low, no

Increased seawater pH and saturation states
may have local adverse impacts on marine biota.
Possible release of nutritive or toxic elements
and compounds may perturb marine ecosystems.
Mining impacts.

Reduced ocean acidification can benefit biodiversity,
especially corals and crustaceans.

Ocean
fertilisation(Biological capture via
fertilisation or enhanced
upwelling) -> (Storage in marine
sediment)

1-2

50 - 500

1-3

Capture: low, no
Storage:low, noNutrient redistribution, enhanced oxygen
consumption and acidification in deeper waters
could perturb marine ecosystems. Could
encourage toxic algae. The fraction of removed
CO2 reaching durable storage is uncertain, due tore-metabolisation.

Enhanced biological productivity, which could increase
fish catch.

Coastalwetland(blue carbon)
management(Biological capture via aquaticbiomass) -> (Storage in aquaticbiomass)

2-3

Insufficient
data

<1

Capture: low, no
Storage:med, noVulnerable to reversal through sea level rise.
Difficult to quantify CDR accurately.

Can contribute to ecosystem-based adaptation, coastal
protection, increased biodiversity.
Can reduce methane emissions. Could benefit humannutrition or be used to produce fertiliser for agriculture,
to produce a methane-reducing feed additive, or as anindustrial feedstock.

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The State of Carbon Dioxide Removal
BECCS(Bioenergy
with Carbon
Capture andStorage)(Biological capture via plant
growth -> cropping andforestry residues, organic
wastes, or purpose-growncrops) -> (Concentrated CO2) ->(Storage in lithosphere)

5-6

15 - 400

0.5-11

Capture: high,yes
Storage:high, yes

Competition for land and water resources, if
based on purpose-grown biomass feedstock. Lossof biodiversity, carbon stock and soil fertility iffrom unsustainable biomass harvest.
Use of potentially contaminated biomass residues(such as post-consumer wood waste) can pose air
pollution risks.

Bioenergy (bio-electricity, biofuel, biogas) displaces
fossil fuels and enhances fuel security. Reduction in air
pollution when engineered BECCS facilities displace
in-field biomass burning. Utilisation of residues provides
additional income and can improve crop growth andhealth. Purpose-grown biomass crops can enhancebiodiversity, soil health, water quality and land carbon.

Afforestation/
Reforestation(Biological capture via trees) ->(Storage in trees)

8-9

0 - 2400.5-10Capture:high, yes
Storage:high, yes

Reversal of CDR through wildfire, disease, pests.
Reduced catchment water yield and lower
groundwater level if species and biome areinappropriate.
Finite carbon carrying capacity of land; capacity
may be reduced under climate change.

Enhanced employment and local livelihoods, improved
biodiversity, improved renewable wood products
provision, soil carbon and nutrient cycling. Possibly lesspressure on primary forest.

Biochar(Biological capture via croppingand forestry residues, organic
wastes, or purpose-growncrops) -> (Storage in biochar)

6-7

10 - 345

0.3-6.6

Capture:high, yes**
Storage:med, yes**

Particulate and greenhouse gas emissions frombiochar production; biodiversity and carbon stock
loss if from unsustainable biomass harvest.

Increased crop yields; reduced non-CO2 emissions fromsoil; resilience to drought.

Soil carbon
sequestration(Biological capture via various
agricultural practices andpasture management) ->(Storage in soils)

8-9-45 - 100

0.6-9.3

Capture:med, yes
Storage:low, yes

Increased nitrous oxide emissions due to higher
levels of organic nitrogen in soil.
Finite capacity of soil to protect organic matter;
capacity may be reduced under climate change.

Improved soil quality, resilience and agricultural
productivity.

Peatlandand wetland
restoration(Biological capture via
rewetting and revegetation) ->(Storage in soils)

8-9

Insufficientdata

0.5-2.1

Capture:low, yes
Storage:low, yes

Increased methane emissions.

Increased productivity of fisheries, improved
biodiversity, soil carbon and nutrient cycling.

Agroforestry(Biological capture via trees) ->(Storage in trees)

8-9Insufficientdata

0.3-9.4

Capture:med, yes
Storage:med, yes

Trade-offs with agricultural crop production.

Enhanced employment and local livelihoods, variety of
products, improved soil quality, more resilient systems.

DurableHarvested
Wood
Products***(Biological capture via trees)-> (Storage in wood inconstruction)

8-9

Insufficientdata

0.2-1.3

Capture: high,yes
Storage:med, yes

Increased fertiliser use and introduced
species could reduce biodiversity and increase
eutrophication. Fire risk.

Reduced ecological toxicity, improved human healthand wellbeing and reduced duration of construction
compared with alternative building materials.

Improved
forestmanagement(Biological capture via trees) ->(Storage in trees)

8-9Insufficientdata

0.1-2.1

Capture:med, yes
Storage:med, yes

Increased fertiliser use and introduced
species could reduce biodiversity and increase
eutrophication.

Improved productivity, enhanced employment and local
livelihoods; can enhance biodiversity.

For each method’s route, the ultimate form of carbon storage is colour coded to match the carbon pools in Figure 1.2.

***The Intergovernmental Panel on Climate Change (IPCC) provides a biochar MRV methodology as an option for national inventories.
***
Data for wood in construction taken from Himes & Busby. Wood buildings as a climate solution. Developments in the Built Environment 4, 100030 (2020). doi.org/10.1016/j.dibe.2020.100030, and Mishra
et al. Land use change and carbon emissions of a transformation to timber cities. Nat Commun 13, 4889 (2022). https://doi.org/10.1038/s41467-022-32244-w

19

“Since the early 1990s, researchon CDR has grown exponentially– faster than for climate change
as a whole.”

The State of Carbon Dioxide Removal

Chapter 2 | Research landscape
Chapter team: Jan C Minxi ii, Sarah Lücki, Max Callaghani, Sabine Fussi
iii

Mercator Research Institute on Global Commons and Climate Change (MCC)
University of Leeds

Since the early 1990s, research on Carbon Dioxide Removal has grown exponentially –faster than for climate change as a whole. Most of this rapid growth has been driven bybiochar research.

Box 2.1 Key findings•

There is a vast and fast-growing scientific literature on Carbon Dioxide Removal (CDR)
of about 28,000 studies in Web of Science and Scopus alone – two of the largest
English-language bibliographic databases.

•

Studies on CDR make up less than 4% of the scientific literature on climate change but
are growing exponentially by about 19% per year (1990-2021). Annual publications
are currently doubling every three to four years.

•

Scientific studies on CDR are dominated by biochar, soil carbon sequestration andafforestation/reforestation. Such methods account for about 80% of the CDR methods
covered in the scientific literature.

•

Research on biochar is growing faster than that of any other CDR method, accounting
for about 40% of the coverage on CDR methods in the scientific literature overall andabout 50% of the studies published in 2021.

•

Bioenergy with Carbon Capture and Storage as well as Direct Air Capture and Direct
Air Carbon Capture and Storage receive comparatively little attention in the CDR
literature – despite dominating discussions on, respectively, the role of CDR in climatechange mitigation scenarios and private CDR investment.

•

Only about a third of the scientific literature on CDR has a geographical focus,
highlighting a potential lack of information tailored to specific local or regional
contexts, particularly Africa and South America.

•

Based on first author affiliation, 32% of scientific studies on CDR are written in China,
9% in the United States and 4% in Australia. This is particularly driven by a strong
dominance of biochar research in China.

•

The scientific literature on CDR is mainly published in natural science (49%),
agricultural science (25%) and engineering and technology journals (23%). Only 3% ispublished in social science journals, and a handful in the humanities.

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The State of Carbon Dioxide Removal

2.1 Overall scientific attention
The scientific literature on Carbon Dioxide Removal (CDR) is small compared with climatechange as a whole, but growing faster.
A key indicator of the state of CDR is how much scientific research is being carried out. In
this chapter, we use a machine-learning approach to identify, track and analyse the scientific
literature published on CDR since the early 1990s (Box 2.2). We find a dynamic picture of
the level of scientific attention on CDR over time, both as a general topic and at the level ofindividual CDR methods.

Box 2.2 Our methods for tracking scientific researchon CDR
We use a machine learning-based approach to measure attention to CDR in thescientific literature²⁴⁻²⁷.
First, we design combinations of search terms (“search strings”) for each CDR
method based on a comprehensive list of keywords. We then validate the searchstrings against a set of studies included in the Intergovernmental Panel on Climate
Change’s Sixth Assessment Report, ensuring that these studies are returned.
These search strings retrieve a total of 60,000 records from two large bibliographic
databases: the Web of Science and Scopus. We then manually screen the title,
abstract and keywords of 400-600 records per search string and label them with
their suitability for inclusion (relevant/irrelevant) and the specific CDR method
being studied. In total, we labelled 5,600 documents. Finally, we use this labelleddata to train a state-of-the-art machine-learning classifier²⁸ to predict relevance forinclusion and the specific CDR method for the 56,000 remaining records. Our
automated approach enables a comprehensive search for scientific literature in
bibliographic databases while still ensuring a high level of precision in terms of theidentification of relevant studies.
While the machine-learning methodology allows a more comprehensive assessmentof the state of scientific research on CDR than has previously been possible, theanalysis presented here has important limitations. First, our use of two major
bibliographic databases (Web of Science and Scopus) covers most peer-reviewed
literature, including social science studies, but excludes large parts of the non-peerreviewed literature. Second, the search methodology is limited to returning articles
with English-language abstracts. Third, we include not only studies on Direct Air
Carbon Capture and Storage but also studies on Direct Air Capture without knowing
about the fate of the captured CO2. Hence, some of those Direct Air Capture
studies might not count as CDR, as we define it in this report (see Chapter 1 –Introduction).

By the end of 2021, there were about 28,000 English-language scientific studies on CDR
in the Web of Science and Scopus – the two largest commercial bibliographic databases.
This is a vast number of publications and a much larger figure than previously indicated in
the scientific discussion or any ongoing community effort to track CDR research29,30. Based

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The State of Carbon Dioxide Removal
on estimates that the Web of Science covers about 43% of the entire scientific literature31,
and assuming that this share is representative also for the literature on CDR, there could be
about 50,000 English-language studies on CDR overall.

Number of publications

The total number of studies on CDR makes up less than 4% of the scientific literature on
climate change26,32,33, but growth has been very rapid. Since the early 1990s, the number ofstudies on CDR has grown exponentially by about 19% per year – faster than the literature
on climate change (13% per year). Right now, the number of annual publications doubles
every three to four years. This growth started from a very low level, however: in the 1990s,
publications per year reached no more than a few dozen, while almost 4,700 papers on CDR
were published in 2021 alone.

AR623,029

5000
4000
3000
2000
1000

Share of CDR
methods per year

1.0

Share of CDR
methods per AR cycle

0

1.0

AR3
439

AR2
151

AR1
22

AR5
3165

AR4
1420

1990

1995

2000

2005

2010

2015

2020

1990

1995

2000

2005

2010

2015

2020

0.5

0.0

0.5

0.0

AR1

BECCS

AR2

DAC(CS)

Agroforestry

AR3

Soil carbon sequestration

Improved forest management

Coastal wetland (blue carbon) management

AR4
Aﬀorestation/Reforestation

Biochar

AR5

AR6

Restoration of landscapes/peats

Enhanced rock weathering

Ocean fertilisation and artiﬁcial upwelling

Ocean alkalinisation
General CDR

Other

Figure 2.1. Exponential growth in the scientific literature on Carbon Dioxide Removal (CDR) over time. Total
number of scientific publications on CDR per year from 1990 to 2021 in the Web of Science and Scopus(top panel). Share of CDR methods covered in these scientific publications per year (middle panel). Share of
CDR methods covered in scientific publications released during each Assessment Report (AR) cycle of theIntergovernmental Panel on Climate Change (bottom panel). Definitions: Bioenergy with Carbon Capture andStorage (BECCS), Direct Air Carbon Capture (DAC) and Direct Air Carbon Capture and Storage (DACCS).

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The State of Carbon Dioxide Removal
The analysis presented above does not include scientific publications on Carbon Capture andStorage (CCS) nor on biomass harvested for energy without CCS – as these do not, on theirown, count as CDR (see Chapter 1 – Introduction, Box 1.2). The growth rate of the CCS
literature, however, provides an interesting contrast with that of CDR (see Box 2.3).

Box 2.3 Tracking scientific literature on Carbon
Capture and Storage
While fossil Carbon Capture and Storage (CCS) does not count as CDR (see Chapter 1– Introduction, Box 1.2), it is still instructive to also track the literature on CCS, as many
critical aspects of CCS are not comprehensively discussed in the dedicated CDR literature.

Publications
on CCS

We find approximately 16,000 scientific publications on CCS in the Web of Science and
Scopus overall (see Box 2.2), with a notably different growth pattern to that of CDR andthe different CDR methods. The literature base on CCS grew steadily during the 2000s,
peaking at about 1,500 publications annually in 2017. Annual publications subsequently
declined to about 900–1,300 publications in subsequent years. Compared with total
publications on CDR, as well as the climate change literature as a whole, there appears to
be a recent levelling out of scientific literature dedicated to CCS. This is despite the strong
reliance on CCS in climate change mitigation scenarios that are consistent with meeting
the Paris temperature goal34–36 (see Chapter 7 – Scenarios).

1000

0

1990

1995

2000

2005
Publication year

2010

2015

2020

Figure 2.2. Total number of publications on Carbon Capture and Storage (CCS) per year from 1990 to 2021.
Growth in the scientific literature on CCS appeared to peak in 2017 with around 1,500 publications per year.

2.2 Individual CDR methods, geographical focus
and scientific disciplines
Scientific studies on CDR are concentrated on particular methods and regions, with others
receiving little attention. Natural science and engineering perspectives heavily dominate
over the social sciences.

24

The State of Carbon Dioxide Removal
Individual CDR methods
Biochar accounts for almost 40% of the coverage on CDR methods in the approximately
28,000 scientific publications on CDR (Figure 2.1). Biochar is material made from harvested
biomass that has removed CO2 from the atmosphere during plant growth and has been
pyrolysed (heated in an oxygen-limited environment), with a portion of the CO2 being locked
into the char.
There is also a sizeable scientific literature on soil carbon sequestration (accounting for 26% of
the coverage on CDR methods) and afforestation/reforestation (12%). Bioenergy with Carbon
Capture and Storage (BECCS) represents only about 5% of the CDR methods covered in thescientific literature, despite being the dominant novel CDR method in most scenario pathways
for meeting the Paris temperature goal4,37,38 (see Chapter 7 – Scenarios) and having received
considerable space in high-level editorials and commentaries on CDR39–41. Three per cent is oncoastal wetland (blue carbon) management. Direct Air Capture (DAC) and Direct Air Carbon
Capture and Storage (DACCS), which have received a lot of attention in the CDR innovationand investment space, only make up about 2% of the CDR methods covered in the scientific
literature. There are several hundred studies on peatland and wetland restoration (2%), ocean
fertilisation (1%), enhanced rock weathering (1%) and improved forest management (1%).
Scientific literature on ocean alkalinisation and agroforestry in the context of CDR is still in its
infancy, with about 100–200 studies each. There are about 1,000 studies (3%) dealing with
CDR in a generic sense, without focusing on a specific method.
During most of the 2000s, only 3-5% of the discussion of CDR methods was on biochar. But
over the last decade (2011-2021), biochar research grew by about 32% annually – fasterthan any other CDR method and than the average growth across all methods (19% per year).
In 2021, biochar accounted for about 50% of the CDR methods covered in the scientific
literature (2,900 studies) – most of these being laboratory studies or field experiments.
Growth in the literature on other CDR methods has been more moderate. Research oncoastal wetland (blue carbon) management, enhanced rock weathering and soil carbon
sequestration has grown by about 25%, 23% and 21% per year, respectively. The remaining
CDR methods have developed slower than the average growth in scientific publications on
CDR as a whole: research on DAC(CS) by 14% per year and on BECCS by 6% per year.
Geographical focus
Research on CDR that is specific to a geographical location (place-specific) is important as
it can consider the local circumstances that determine the efficacy of CDR methods; theirpotential co-benefits and adverse side effects; and their equitable implementation, operationand governance. However, less than a third of the English-language scientific publications on
CDR covered here (8,900 out of 28,000 studies) mention a location in the title or abstract.
Of those 8,900 studies, 69% mention national-level locations and about 30% subnational
locations. Few studies mention broader regions or continents in their abstracts (Figure 2.3).
The distribution of study locations mentioned is very uneven across major world regions(Figure 2.4). More than 40% of all place-specific CDR research refers to locations in Asia(~3,700 studies), 24% in North America (~2,100 studies) and about 18% in Europe (~1,600
studies). Only 5-6% of place-specific CDR research focuses on South America, Oceania
and Africa (~500 studies or fewer). This indicates that there is a potential gap in sitespecific knowledge with respect to CDR methods in Africa and South America – despite
their importance for carbon storage from land-use change and the provision of biomass forvarious CDR pathways in global integrated assessment models42,43.

25

The State of Carbon Dioxide Removal

A
Number of publications
mentioning a location

4000
2690

C

2000

Aﬃliation
0

Share of literature
mentioning a location (%)

B

6062

6000

91
Sub-national

National0
EuropeNorth America

14,541

Publication
AfricaAsia

Asia

EuropeEuropeRegional50

Asia

Europe9582

Asia

Aﬃliationof ﬁrstauthorAfrica100

AfricaNorth
America
5654

South America

Oceania

North America

North America

South America
OceaniaSouth America
Oceania

Figure 2.3. Geographical locations mentioned in the abstract and/or title of Carbon Dioxide Removal (CDR)
research publications, shown by level of analysis (subnational, national or regional – for example, Western Africa,
North Africa) and by world region (panel A top and bottom, respectively). Continent in which CDR research
is produced, derived from the first author’s affiliation (panel B). How geographical locations mentioned in the
abstract/title of a CDR research publication are related to the first author affiliation (panel C).

The geographical focus of place-based CDR research also differs strongly for different CDR
methods. The vast majority of place-based CDR research is on CDR methods involving
biological storage on land or in biochar – soil carbon sequestration (32%), biochar (24%)
and afforestation/reforestation (20%) together make up more than three-quarters of placespecific CDR research. Other CDR methods such as DAC(CS) (1%; ~40 studies) feature only
marginally, partly because the overall size of the scientific literature on these methods ismuch smaller.
In general, CDR methods that involve biological storage on land are much more likely
to feature place-specific research. For example, about 50% of studies on afforestation/
reforestation have an explicit geographical focus. In contrast, only about 6% of scientificstudies on DAC(CS) have a specific regional focus. About a quarter of all research on
enhanced rock weathering is place-specific, while this is the case for only 8% of studies on
ocean alkalinisation. This may be primarily due to institutional challenges involved in setting
up experimental research in the ocean.

26

The State of Carbon Dioxide Removal

Number of publications

2000

1500

1000

500

0

Number of
publications

4000
3000
2000
1000
0

Share intechnologies

1.0

0.5

0.0

Africa

BECCS

Asia

DAC(CS)

Agroforestry

EuropeSoil carbon sequestration

Improved forest management

Coastal wetland (blue carbon) management

North
AmericaAﬀorestation/Reforestation
Biochar

OceaniaSouth
America

Restoration of landscapes/peats

Enhanced rock weathering

Ocean fertilisation and artiﬁcial upwelling

Ocean alkalinisation
General CDR

Other

Figure 2.4. The distribution of place-based Carbon Dioxide Removal (CDR) research is very uneven across major global
regions. Total number of CDR research publications that mention a geographic location in abstract or title, shown by
country (top) and world region (middle). Share of CDR methods in scientific research publication that refer to a specificgeographic location, shown by world region (bottom). Definitions: Bioenergy with Carbon Capture and Storage (BECCS),
Direct Air Carbon Capture (DAC) and Direct Air Carbon Capture and Storage (DACCS).

Analysing the affiliations of the (first) authors of English-language peer-reviewed researchon CDR, we find that Asia – and in particular China – is a hotspot in terms of producing
CDR research. This is mainly driven by high levels of research activity on conventional CDR
methods on land, as well as biochar. Overall, there are about 8,900 publications on CDR
for which the first author’s affiliation is in China, followed by the United States (2,600) andAustralia (1,200). This finding is particularly driven by a strong dominance of biochar researchin China. This is also reflected when looking at research organisations. Of the researchorganisations with the largest numbers of first-authored publications on CDR, nine of the top
ten are in China.
In general, place-based CDR research is led by research teams from the country under27

The State of Carbon Dioxide Removal
investigation. Studies led by European research organisations are the most likely to coverregions outside Europe (28% of their total publications), while research organisations basedin Asia dedicate a smaller fraction of their CDR research to other regions (13%).
Scientific disciplines
About half the CDR research is taking place in the domain of the natural sciences. About
49% of the scientific discussion around CDR is published in academic outlets that classify
themselves as natural science journals. These also include a range of interdisciplinary journals
such as Science or Nature. Two other scientific domains attract substantive CDR research:about 25% of research papers are published in agricultural science journals and 22% injournals on engineering and technology. This highlights the focus of the CDR researchcommunity to date on studying the workings of individual CDR methods.
So far, only a very small share (~3%) of CDR studies are published in social science journals,
and there are only a handful of studies in humanities journals. The social sciences andhumanities are crucial for discussions on implementation, equity and governance of CDR,
but scientific discussion in the English-language peer-reviewed literature is not yet fully
developed in these areas29.

2.3 Building understanding
Closing the evidence gap requires research on CDR methods where it is missing or scarce
as well as improvement in our understanding of local and regional aspects of deploying andupscaling CDR.
There are very large differences in scientific attention to different CDR methods. While there
is a very large amount of evidence on certain CDR methods, such as biochar or soil carbon
sequestration, a range of other CDR methods are still the subject of relatively few studies,such as peatland and wetland restoration, ocean alkalinization and DAC(CS). This suggests
great differences in the detailed understanding of the various CDR methods, which needs tobe addressed for a sound understanding of the entire portfolio of CDR methods.
Critically, place-specific research on CDR is still underdeveloped for almost all novel
CDR methods except biochar. Regional and local circumstances will determine the costs,
mitigation potentials and side effects of specific CDR methods and also relate to important
governance aspects. Place-specific research will be critical for advancing scientific evidence
on CDR, notably in regions that are typically projected to provide substantial deployments ofspecific CDR methods in global mitigation pathways that limit warming to well below 2°C37.
Finally, only a very small share of research is published in social science journals – andalmost none in the humanities. This is an indication that CDR research still mainly focuseson the development and application of CDR methods. There is a need within the scientificcommunity to give more attention to issues around policy, governance and equity.
Our results suggest that the size of the literature on CDR – already vast and fast-growing– may make it difficult to keep an overview of developments in research. This suggests theneed for tracking CDR research in quasi real time. Moreover, there is a growing need for thisevidence to be continuously synthesised and presented in an accessible format, requiringrigorous systematic review work to ensure that the best-available CDR knowledge can beconsidered in science and policy.

28

The State of Carbon Dioxide Removal“Public funding, patenting
and investment in CDR have
expanded dramatically in thepast two years.”

29

The State of Carbon Dioxide Removal

Chapter 3 | Innovation
Chapter team: Gregory F Nemeti, Jenna Greeneii

University of Wisconsin-Madison

Growing public funding, patenting and investment show that innovation in Carbon Dioxide
Removal is active. But the pace is still modest compared with what is needed to meetindustry targets and the Paris temperature goal.

Box 3.1 Key findings•

Global public investment in Carbon Dioxide Removal (CDR) Research, Development
and Demonstration (RD&D) was approximately $4.1 billion between 2010 and 2022.

•

Public RD&D funding is concentrated in a few regions. Proposed Direct Air Capture(DAC) demonstration hubs in the United States account for the vast majority oftraceable public funding ($3.5 billion).

•

Global CDR patenting activity has increased over the last 15 years, with a large andgrowing share occurring in China. In 2018 – the last year of complete data – China
accounted for 36% of all CDR patents.

•

DAC (a component of Direct Air Carbon Capture and Storage, DACCS) is dominant
in the share of total CDR patents from 2000 to 2018. Ocean-based methods makeup only a small portion of total CDR patents. The technological focus of patents has
become more diverse in recent years.

•

Investment in new CDR capacity totalled approximately $200 million between 2020
and 2022. The vast majority of announced purchases focus on DACCS, with biochar
the next most prominent method.

3.1 Measuring growth in Carbon Dioxide Removal
innovation
Innovation in Carbon Dioxide Removal (CDR) has expanded dramatically in the past
two years, as measured by publicly funded Research, Development and Demonstration(RD&D), patents and investment in new capacity.
Examining innovation is important because it provides an understanding of how CDR
methods are evolving, how fast they might become deployed and how costs are changing.
Innovation requires multiple metrics to assess, given that it consists of a sequence ofinterlinked processes (Figure 3.1)5. This chapter assesses the state of CDR innovation using
three sets of metrics44: public investment in CDR RD&D; patenting; and investment in new
capacity. These indicators assess the rates of change in different stages of the innovation
process (Figure 3.1). Public investment in RD&D measures supply factors, particularly early-

30

The State of Carbon Dioxide Removal
stage inputs in the RD&D stage of innovation.
Patenting is a measure of inventive activity that relates to supply factors (Research andDevelopment, demonstrations, and scale-up) as well as demand factors such as nichemarkets and demand pull. Investment in new capacity relates to demand factors (demand
pull towards increased adoption while establishing public acceptance). Looking ahead,
we examine the future rates of growth in CDR innovation (relating to the scale-up stage)
implied by the targets set by companies and industry groups. We note that feedbacks fromlater stages to earlier ones have been crucial for other technologies (e.g. market experience
identifies new directions for development). We expect these feedbacks to also be important
for CDR.

Supply factors
R&D

Demonstrations

Demand factors
Scale upNiche markets

Demand pull

Public acceptance

Example feedbacks

Figure 3.1. The process of innovation for Carbon Dioxide Removal consists of a sequence of interlinked stages
that feed back and build on one another. These stages are broadly split into two categories: supply factors (Research and Development [R&D], demonstrations and scale-up) and demand factors (niche markets, demand pull
and public acceptance). Source: Nemet et al.5

Box 3.2 Our methods for assessing growth in Carbon
Dioxide Removal innovation
Research, Development and Demonstration (RD&D) – Data on RD&D spending
specifically related to Carbon Dioxide Removal (CDR) is patchy, in contrast to otherclimate change mitigation methods, but it is also similar in that respect to energy
RD&D in its early years. We use publicly available data from country plans, policies andannouncements that are explicitly labelled as funding research on CDR, greenhouse gas
removal or negative emissions methods. We do not include funding for elements thatare not CDR methods in themselves but are important components (e.g. Carbon Captureand Storage [CCS] and biomass use). Nor do we include funding which is not labelled as
CDR but may still include relevant methods (e.g. tree planting, soil management). Dataon public RD&D investment is for 2010-2022. We convert currencies to US dollars forcomparison using currency values from the Federal Reserve45. For more detail on CDR
research directions, refer to Chapter 2 – Research landscape for a summary of the Englishlanguage, peer-reviewed scientific literature on CDR.

31

The State of Carbon Dioxide Removal

Patent activity – To measure patent activity for CDR methods and/or components overtime and by method we use patent family counts, and to measure country activity weuse patent application counts. We use the search methodology from Kang et al. in the
Derwent Innovations Index to gather patent data46. Patent families avoid double-counting
by grouping patents for the same invention that are filed in multiple countries or patentoffices. Analysing patent applications, on the other hand, ensures that we account for eachof the different countries where patents are filed. We use the patent application date forthe time range of 1980-2020, using the search terms from Kang et al. The search terms
for Direct Air Capture do not include storage. We do not include patents related to CCS
without a CO2 removal component, even though these patents are related to elements ofsome CDR methods (such as Direct Air Carbon Capture and Storage and Bioenergy with
Carbon Capture and Storage).
Investment in new capacity – We use the Marginal Carbon database, which collects
known announced purchases of durable CDR, including the year of purchase and CDR
method. The announced purchases are included in the database, and thus in this chapter,
if the CO2 is stored for at least 100 years. For announced purchases without a purchaseprice, we apply a cost per tonne by method47. We assess the cost per tonne from the otherannounced purchases for each method and year. The database gives an indication of thelevel and relative share of CDR methods on the market. However, it is not a complete
database and includes uncertainties. For example, the database lists “carbon dioxide fromconcrete” as a CDR method. It is unclear, however, if the CO2 in this method is from afossil origin or biogenic origin, which would classify it as fossil CCS rather than CDR (seeChapter 1 – Introduction, Box 1.2). These instances of uncertainty have been included in
the total investment calculations to capture the full scope of investments.

Public Research, Development and Demonstration
Research, Development and Demonstration that is funded by the public sector (publicRD&D) provides important information on where early-stage development is being directed
and where gaps exist45. While public RD&D is typically smaller than private RD&D at
the economy level, the former can play a much bigger role for nascent technologies andbe crucial to entraining the latter48. Using publicly available data, we find global public
investment in CDR RD&D of approximately $4.1 billion during the period 2010-2022. To put
this in perspective, global annual spending on energy RD&D in 2021 alone was $17 billion
for Organisation for Economic Co-operation and Development (OECD) countries, which
excludes China.
Global public investment in RD&D funding is concentrated in a few regions, and theoverwhelming majority of the total is $3.5 billion for Direct Air Capture (DAC) hubs in theUS, spread over multiple years. This demonstration programme is open to projects thatutilise or store the captured CO2. While not all the CO2 captured is therefore likely tobe durably stored, we include this programme within our analysis of innovation because
demonstration of the DAC components advances the Direct Air Carbon Capture and Storage(DACCS) method as a whole.
Below, we summarise the diverse sets of CDR activities covered by public RD&D funding ineight countries and regions that have accessible information on public CDR RD&D – either
data on public RD&D funding or net zero targets that will require CDR. We have not found32

The State of Carbon Dioxide Removal
RD&D programmes specifically labelled as CDR in the rest of the world. We are aware,
however, that there is further public RD&D investment in programmes that incorporate
CDR methods but that are not labelled as such, for example European Union (EU) funding
for research into CDR from agricultural/forestry management practices48,49. Like other areasof science and technology, publicly funded RD&D is overwhelmingly concentrated in highincome economies, although other countries may have unique characteristics that makethem well suited for conducting CDR research (such as energy sources and local climate)in the future. Financial flows and technology transfer between countries can aid CDR
innovation beyond the countries described below1.
Australia
In 2021, the Australian government funded an A$4 million (US$2.5 million) DACCS
demonstration project50. Although the government has funded several Carbon Capture andUtilisation projects, no large-scale funding for CDR has yet been announced.
CanadaCanada has committed to achieving net-zero greenhouse gas (GHG) emissions by 2050
through the Canadian Net-Zero Emissions Accountability Act51. While Canada hasinvested in RD&D for Carbon Capture and Utilisation and low-carbon technologies, thefederal government has not yet announced investments explicitly for CDR. The Net Zero
Accelerator Initiative and the Climate Action and Awareness Fund may both fund CDR
research in the future52,53.
China
China has established a target of carbon neutrality by 2060 that will require CDR methods54.
Total investment from the Chinese government in 2018 on forestry and grasslands totalledabout ¥140 billion ($21 billion), although only a portion of this funding is specifically focusedon carbon storage via biological methods55. Data on total RD&D expenditures for CDR in
China is not publicly available.
European Union
The European Climate Law includes a target for climate neutrality56. In April 2022, theEuropean Commission announced funding for one Bioenergy with Carbon Capture andStorage (BECCS) project worth €180 million ($180 million) via the EU Innovation Fund,which is funded by revenues from the EU’s Emissions Trading System57. The second
mechanism for funding CDR is Horizon Europe, the EU’s programme on research,development and innovation58. This supports a variety of CDR methods. An analysis from
Carbon Gap, an environmental NGO, estimates that funding from Horizon Europe will be€185 million for activities both directly and indirectly related to CDR (funding 34 projects)and €161 million for projects directly related to CDR (funding 28 projects)59. The Horizon
Europe programme includes funding for projects specifically on RD&D under the Climate,
Energy and Mobility cluster: on CDR approaches (€21 million) as of 2021 and on Negative
Emissions as of 202057,58.
Germany
Since 2021, the German Federal Ministry of Education and Research has funded two major
research missions: one on ocean-based CDR methods and marine CO2 storage methods(CDRmare) and the other on land-based CDR methods (CDRterra). CDRmare began funding six
projects in 2021 worth a total of €26 million ($26 million)60. CDRterra began funding projects
on DACCS, biochar, enhanced rock weathering, BECCS, and afforestation/reforestation
worth a total of €21 million ($21 million)61.

33

The State of Carbon Dioxide Removal
Japan
The Moonshot Research and Development Program in Japan was developed by the Council
for Science, Technology and Innovation and the Headquarters for Healthcare Policy andincludes a goal on sustainable resources62,63. The purpose of the programme is to promote“challenging R&D based on revolutionary concepts” and includes CDR in the “Moonshot
for beyond Zero-Emission Society”64. In 2022, a call for proposals for Moonshot funding
was announced with a maximum amount per project of ¥500 million ($3.6 million). Japan’s
Ministry of the Environment also provided funding for a large-scale BECCS plant in 202065.
United Kingdom
The UK has invested in RD&D on a wide range of GHG removal technologies – primarily
CDR methods but also some methane removal projects. The first GHG removal RD&D
programme ran from 2017 to 2021, funding 11 projects totalling £8.6 million ($9.7 million)66.
The UK Government’s Net Zero Strategy, published in 2021, includes CDR deployment
goals and two new RD&D programmes focused on demonstration67. The first is a precommercial innovation competition funded through the Department for Business, Energy
and Industrial Strategy68. In the first phase, 23 projects focusing on the design and feasibilityof CDR methods each received £250,000 (a total of £5.9 million, or $6.7 million). In Phase
Two, an additional £58 million ($65 million) will be awarded to pilot the 15 most promising
designs (ending March 2025)69. Afforestation and other conventional CDR methods onland are excluded from the competition, though their role in meeting the net zero target isrecognised. As the second programme, UK Research and Innovation announced over £30
million ($34 million) to investigate the viability of five GHG removal demonstration projects
and a central research hub70. The projects vary in method and include peatland restoration,enhanced rock weathering, biochar, afforestation, and biomass crops for use in BECCS71.
United States
In 2021, the US announced a target to achieve net-zero greenhouse gas emissions economywide72. The US Department of Energy (DOE) launched the Carbon Negative Shot as an
RD&D initiative for CDR focused on storing CO2 at gigatonne scales for less than $100/
net tonne73. In 2020, the US Congress appropriated $40 million for CDR Research andDevelopment (R&D), of which $15 million was specifically appropriated for DAC74. In 2021,$63 million was appropriated for CDR R&D, with $22 million specifically for DAC75. In 2021,
RD&D projects worth $18 million were announced through the DOE and the Office of Fossil
Energy and Carbon Management to fund DAC74,76. Congressional appropriation for CDR
R&D increased to $104 million in 2022, with $75 million specifically for DAC77. In 2022, theDOE announced $3.5 billion in funding under the Bipartisan Infrastructure Law’s programme
on CDR to develop the Regional Direct Air Capture Hubs programme to support four DAC
hubs75. As a part of the Carbon Negative Shot initiative, the DOE announced $30 million
to fund RD&D on DAC and ocean-based CDR methods that include “permanent storage orutilization”78. Since 2010, the US DOE and the US Department of Agriculture have funded
RD&D for land-based CDR totalling about $49 million, through “improved crops for soil
carbon sequestration” and biochar research79. The National Science Foundation has also
funded R&D ocean-based CDR methods, including iron fertilisation79.
Patenting
Patenting activity can provide a useful measure of innovation by indicating the pace of
invention. Inventive activity comes from supply-side RD&D, demonstration and scale-up
and can also be supported by demand factors such as niche markets and demand pull. Our
examination of CDR patenting activity at the global level suggests an overall increase overthe last 15 years, with a large and growing share of patenting occurring in China. The most34

The State of Carbon Dioxide Removal
prominent component in terms of growth in patents is DAC. China is also a hotspot in termsof generating scientific research on CDR – though this is driven particularly by studies on
biological CDR methods (see Chapter 2 – Research landscape). Patenting activity is one
measure of innovation, and one with accessible data, but innovation can also occur outsideof what firms choose to patent. Invention, experimentation and learning can be retained
as tacit knowledge and trade secrets. Another alternative is a transparent approach, withinventions published unprotected as research papers (see Chapter 2 – Research landscape)or as freely available data and designs (e.g. OpenAir Collective)80.

Patent count80

Truncated
data

60
40
20
0

2000

2002

2004

2000

2002

2004

2006

2008

2010

2012

2014

2016

2018

2020

2008

2010

2012

2014

2016

2018

2020

2010

2012

2014

2016

2018

2020

Percent of total
patents by country

100%

50%

0%

China

United States

2006
WIPO

Other

Percent of total
patents by method

100%

50%

0%

2000

2002

2004

2006

Aﬀorestation/Reforestation

BECCS

Enhanced rock weathering

Generic CDR

2008

BiocharCoastal wetland (blue carbon) management

Ocean fertilisation

Direct air capture (DAC)

Soil carbon sequestration

Figure 3.2. Global increase in Carbon Dioxide Removal (CDR) patenting activity. Total number of patents per yearfor 2000-2020, grouped by patent families (top). Families refer to the same invention files in multiple countries.
In 2019 and 2020, the data is truncated because of the time it takes to process the application before publishing.
Percent of individual patent applications per year by the country where the patent was filed (middle). The WorldIntellectual Property Organization (WIPO) is a centralised patent office. Percent of total patent families per year bymethod/component (bottom). Definition: Bioenergy with Carbon capture and Storage (BECCS).

35

The State of Carbon Dioxide RemovalOver the past 20 years, the number of CDR patents has increased (Figure 3.2, top panel).
This, in turn, indicates an increase in innovation in CDR. The last year of full data is 2018,
whereas 2019 and 2020 data is truncated due to the typical two-year time it takes to review
applications.
In terms of distribution of patents between different countries, China has had an increasingly
large share of CDR patents since 2004 (Figure 3.2, middle panel). In the last year of complete
data (2018), patents filed in China made up 36% of all CDR patents filed. China’s share of total
patents is very high in the truncated data for 2019 and 2020, which may, at least in part, be a
result of a faster time to approval in China’s patent offices compared with other countries, suchas the US. The US has also had a large share of all CDR patents, accounting for an average of
23% of annual applications from 2000 to 2018. However, from 2015 to 2018, the share ofpatents filed in the US decreased to 15-20% of annual patent applications, compared to 2337% from 2003 to 2014. WIPO, the World Intellectual Property Organization, is a centralised
patent office where approximately 5-10% of total CDR patents were filed during 2003-2018.
In a majority of cases in which a patent was filed with WIPO (88%), the patent was also filed
in at least one other country. All other countries are grouped into an “Other” category, whichmakes up a large portion of total annual patents during 2000-2018 (31-68%, with an averageof 48% per year). The patents represented by this category are split between many regions andcountries. By 2018, the last year of full data in the analysis, the split is about equal between
China (36%), the United States and WIPO (19% and 15%, respectively, for a total of 34%), andall other countries combined (31%).
In terms of CDR method/component technologies, DAC is dominant in the share of total
CDR patents during 2000-2018 (Figure 3.2, bottom panel). BECCS made up 33% of CDR
patents in 2000, then an average of 18% during 2006-2018. Ocean-based CDR methods
make up only a small portion of CDR patents, with 11 patents on ocean-based methods
filed sporadically during 2000-2018: coastal wetland (blue carbon) management (onepatent), enhanced rock weathering (seven patents) and ocean fertilisation (three patents).
Biochar patents began in 2008 and have continued through 2020. We observe a decline
in technological concentration in the last few years of the data (i.e. smaller shares for thelargest CDR technologies).
Investment in new CDR capacity
The ultimate manifestation of innovation is widespread adoption of a technology. This
happens when it is relatively advantageous compared with other technologies, demand pullis sufficient and the technology is publicly accepted. Using the Marginal Carbon database(see Box 3.2 on methods), we find announced purchases totalling approximately $200
million and 510,000 tonnes of CDR for 2020-2022. Some of this is for offtake agreements
for future purchases (in which the payment comes at the time of delivery) while some isfor pre-purchases, where the tonnes have been paid before the project is complete. Thisdata includes efforts to increase demand for CDR to spur innovation (demand pull) such as
the Frontier advance market commitment (a funding mechanism that involves aggregating
funding and facilitating purchases of CDR)81. Only a small fraction of purchases have actually
been delivered to customers, however (see Chapter 6 – Deployment).
The vast majority (75%, worth $150 million) of announced purchases are focused on
DACCS. This is largely driven by one announcement from 1PointFive/Carbon Engineering(two companies that work to design and deploy DAC facilities) of 100,000 tonnes per year
for four years, with a 2022 average cost per tonne of DACCS of $270. In order of value,
following this there are two announced purchases of a combined $6.4 million, which include

36

The State of Carbon Dioxide Removal
several CDR methods but do not delineate monetary or tonnage amounts per method.
Otherwise, where methods are specified, biochar features as the second most prominent
method among announced purchases.
Some method costs per tonne have gone up from 2020 to 2022 (including DACCS: $780 in2020 to $1,200 in 2021; and biochar: $250 in 2021 to $430 in 2022). This could be seen
as surprising, but the changes are largely driven by single purchases. For example, Shopify
purchased 2,500 tonnes of CO2 removed through biochar for $570/tonne from one supplierin 2022, driving up the average price. It could also be argued that there are no real market
prices for CDR at this early stage. We see that many early backers of novel CDR (by which
we mean methods other than the well-established land-based methods already deployed atscale, such as afforestation/reforestation, soil carbon sequestration, etc.; see Chapter 1 –Introduction for our definitions) are paying for the cost of production as a way of supporting
early development, rather than buying a commodity at market prices. Diffusion theory
and learning rate theories hypothesise that, over time, method costs will decrease as themethods develop and supply increases, but novel CDR methods might not have entered thephase where this starts to happen.
To put this data in perspective, Bloomberg estimates global climate-technology investments(for all mitigation technologies, not just CDR) at $170 billion in 2021 – of which only $0.3
billion relates to CDR82. That means the size of equity investments in CDR is similar toamounts of pre-purchases and offtake agreements. ​​An additional data source, ClimateTech
VC, estimates that the level of CDR equity investments in 2021 was $170 million, and in
2022 $830 million, totalling about $1 billion83. Although this data is not directly comparable
to announced purchase levels, the data is on the same order of magnitude.

3.2 Future growth targets
The novel CDR industry needs to grow by four to six orders of magnitude by mid-century
to meet its own targets and to meet the Paris temperature goal.
We provide an indication of the challenge to scale up CDR by comparing announcementsof CDR targets from companies and industry groups with the current size of the industry
and with estimates of the CDR potential of different methods by 2050. Mid-century CDR
potential is the magnitude of CO2 that can be removed and durably stored from each CDR
method by 2050, while taking into account biophysical limits, economic costs and potential
side effects of deployment.

37

The State of Carbon Dioxide Removal

Box 3.3 Our methods for assessing future growth in
Carbon Dioxide Removal innovation
Growth rates – We use publicly announced company and industry targets for Carbon
Dioxide Removal (CDR) as an indicator for growth in innovation. To calculate company
announcements and capacity for Direct Air Capture (DAC) from 2021 to 2035, we
combine the announced scale-up targets from Carbon Engineering and Climeworks,
two DAC companies84,85. Biochar estimates are from the European Biochar Industry
Consortium, a biochar industry group86. Company announcement targets for Bioenergy
with Carbon Capture and Storage (BECCS) scale-up are from Drax Global87, a UK-basedenergy company with a BECCS plant, and Stockholm Exergi88. These targets are publicly
available and, although not comprehensive of all CDR companies or industry groups,
illustrate the expectations for direction and scale of the market in the coming decades.
For the mid-century potentials of individual CDR methods (Direct Air Carbon Captureand Storage, BECCS and biochar), we use low and high estimates of sustainable global
technology potentials in 2050 from a systematic literature review from Fuss et al4.

The figure below shows the growth trajectories of three specific CDR methods, incorporating
both announced and built capacities from industry and businesses. The shaded areas show
how the last year of company capacity announcements compares with the range in the midcentury potential (the low and high data points shown for 2050) for each CDR method4.

Tonne(s) of carbon dioxide removed annually

10B t

DACCS

10B t

Biochar

10B t

100M t

100M t

100M t

1M t

1M t

1M t

10K t

10K t

10K t

100 t
2020

Build capacity
Announced capacity
2030

2040

2050

100 t
2020

2030

Year

2040

2050

100 t
2020

BECCS

2030

2040

2050

Figure 3.3. Announced Carbon Dioxide Removal (CDR) targets from industry groups and companies imply faster
growth than has been seen historically for most technologies. Squares represent built capacity in three example CDR
methods (Direct Air Carbon Capture and Storage [DACCS], biochar and Bioenergy with Carbon Capture and Storage[BECCS]). Circles represent announced plans for capacity additions. The shaded areas for each CDR method show
how the last year of company capacity announcements could grow to meet CDR socio-technical potential by midcentury: the low and high data points in 2050 represent the range of maximum potential removal, which is dependent
on biophysical limits, economic costs and side effects of deployment.

38

The State of Carbon Dioxide Removal
The figure suggests that the CDR targets of companies and industry groups are generallyaligned with achieving mid-century CDR potentials (see Box 3.3)4, particularly for DACCS
and biochar, because the slopes of the curves for those mid-term targets are steeper thanthose after. However, the figure also makes clear that the CDR industry is currently fiveorders of magnitude smaller than those mid-century potentials. In the particular case of
DACCS, for example, we assess that in mid-2022 about 8,000 tonnes of annual removal
capacity exists89, compared with a mid-range potential of 2 billion tonnes annually by 20504.
Growing from the current level to maximum mid-century potential implies an exponential
growth rate of over 50% per year. That exceeds most previous technologies, but not all (suchas the production of liberty ships in the United States during World War Two and worldwide
computing growth).

3.3 Spurring growth in innovation
There is an urgent need for comprehensive policy support to spur growth in CDR.
To achieve the growth rate in investment in new capacity indicated in our analysis of over
50% per year, there is an urgent need for comprehensive, durable policy support for CDR.
Policies can spur growth in the CDR market to achieve mid-century goals for CDR – andthese expectations are crucial for private investment in CDR innovation and deployment toreach gigatonne scale. Ensuring that data on CDR RD&D funding, patents and investment in
new capacity is comprehensive and publicly available can support the type of policies needed
for CDR scale-up.

39

The State of Carbon Dioxide Removal“Research shows that people’s
initial reactions to CDR are
usually tied to their values,
beliefs and sense of identity.”

40

The State of Carbon Dioxide Removal

Chapter 4 | Public perceptions
Chapter team: Jan C Minxi iv, Emily Coxii, Finn Müller-Hanseni, Tim Repkei, Rob Bellamyiii
Mercator Research Institute on Global Commons and Climate Change (MCC)
University of Oxford
iii
University of Manchesteriv
University of Leeds
iii

How Carbon Dioxide Removal (CDR) is perceived will play a critical role in its future
prospects. Awareness of CDR is still low in studied countries, but social media attention
is growing fast. People are generally supportive of CDR research, but they have more
complicated views about deploying it at scale, depending on the specific method.

Box 4.1 Key findings•

A systematic search of the English-language peer-reviewed literature reveals a small
but growing evidence base, with 39 papers specifically on public perception of Carbon
Dioxide Removal (CDR).

•

Only ten of these peer-reviewed publications are from outside of Western Europe andNorth America, with none covering public views in South America, Eastern Europe orWest/Central Asia.

•

Among the general public in the countries studied, awareness of CDR (as a general
topic and regarding specific CDR methods) is low. Perceptions of this nascent field arestill forming.

•

Despite low prior awareness, studies find reasonable public support for research into
CDR but more concerns about deployment at scale. These involve perceptions ofpotential adverse side effects and tampering with nature, among many other factors.

•

The number of tweets on CDR has grown rapidly over the last decade, increasing fromabout 15 tweets per day in 2010 to about 350 tweets per day in 2021. This is muchless than for climate change in general, at 10,000 tweets per day, but growing faster.

•

Of the tweets mentioning specific CDR methods, 70% involve biological storage onland and in oceans, such as soil carbon sequestration, afforestation/reforestation or
coastal wetland (blue carbon) management. There are comparatively few mentionsof novel CDR methods such as Direct Air Carbon Capture and Storage, but these are
growing rapidly.

•

Public perception research and analysis of the sentiment of tweets suggest thatfamiliar CDR methods (particularly afforestation/reforestation) are generally preferred,and ocean fertilisation is viewed as most risky.

•

Sentiments expressed in tweets on CDR methods have become more positive overtime, with the single exception of Bioenergy with Carbon Capture and Storage.

41

The State of Carbon Dioxide Removal

4.1 Understanding public perception
Two different and complementary sources – peer-reviewed scientific literature and Twitter– can offer insights into public perception of Carbon Dioxide Removal (CDR).
If CDR is to scale to several gigatonnes of removals by mid-century, the next two
decades will be critical. Alongside progress in developing and deploying the CDR methods
themselves, how CDR is perceived will play a vital role. Similarly, attention to CDR in public
discourse reflects the salience of the debate in addressing climate change. Studies show thatpublic acceptance of new technologies is crucial to their widespread adoption5,90–92, meaningthat how technology adopters and the wider public perceive different CDR methods
will influence the prospects for scaling them up5,93–95. Understanding perceptions on andengaging people with CDR, if done well, can support responsible innovation efforts.
There are three broad lines of evidence for gauging people’s perceptions: sampling of a large
group of people (e.g. surveys or survey experiments); studies that focus on individuals and/or small groups (e.g. interviews or deliberative studies); and big-data analysis of social media(e.g. sentiment analysis or stance detection). In this chapter, we take two complementary
approaches to analysing attention to and perceptions of specific CDR methods and of
CDR in general: a synthesis of the main insights from the English-language peer-reviewed
scientific literature on public perception and an analysis of Twitter activity on the topic overtime. While the scientific literature provides very detailed insights into how citizens perceive
CDR methods in different contexts, the Twitter analysis indicates how the salience and toneof communication about CDR has changed over time. As such, together these approaches
provide complementary lines of evidence on perceptions of CDR.

Box 4.2 Types of evidence for assessing (public)
perceptions
Working with multiple types of evidence (such as large sample studies, small group studies,social media analysis) is particularly useful when trying to assess perceptions towards
nascent technologies, because each method has specific advantages and limitations and isrooted in its own set of assumptions. Therefore, the context and scope of the results may
differ. Survey and participatory methods offer researchers greater control over how andfrom whom evidence is collected at a particular point in time, while data-driven analysesof social media content allow researchers to track attention to a topic and sentimenttowards it continuously over time. Surveys can understand perceptions at the time of thestudy in relation to a fixed research question, while social media analysis allows continuous
adjustment of the scope of the inquiry and re-analysis of historical data accordingly.
Who is “the public”? Different approaches to gauging public perception can define “thepublic” in different ways, and definitions such as “public” and “stakeholder” are not fixed.
People also operate from different positions at different times, for instance acting as“professional” or “civic” actors depending on the context96. Survey studies (Section 4.2) often
focus on the attitudes or opinions of a representative sample of a general population (forexample, using recruitment quotas) but may not capture the diversity of “publics” within thatsample. Communication on Twitter (Section 4.3) is dominated by experts, professionals andcorporate interests and, as such, may not represent opinions held by the general population.

42

The State of Carbon Dioxide Removal

Elicited versus non-elicited information: The benefit of surveys, experiments ordeliberative approaches for eliciting information is that these studies operate within an
artificial environment, allowing researchers to control and analyse the context. However,public awareness of many CDR methods is low, which can lead to methodologicalchallenges. For example, participants may need to be presented with a certain amountof information on the topic, on which to base their response. This can lead to responses
being influenced by the way the question is presented, known as “framing effects”.
Nevertheless, a large body of work suggests that, in general, people are competent in theirdeliberations and are capable of discussing complex and novel topics even with low priorawareness97. Analysis of social media is based on non-elicited statements by people who
already have an awareness of CDR. People may express their opinion differently online
than in more private settings or surveys, however. See Box 4.3 for further discussion of
our methodology for social media analysis.

4.2 Scientific evidence on public perceptions
Evidence on how people perceive CDR has large regional disparities, and in studied
populations awareness of CDR remains low.
Research on public perceptions of CDR is spread across a wide variety of social science
disciplines, each of which carries certain assumptions. For example, there are differences in
how researchers understand “the public”, which are reflected in the methods used (see Box4.2). However, most agree that public perceptions of CDR must be understood in relation tobroader issues around emerging technologies and the environment. This area of research ispartly driven by concerns about potential future public opposition, fuelled by past protests
against technologies that CDR sometimes grouped with, such as solar geoengineering
methods or Carbon Capture and Storage (CCS)98.
To understand the existing field of research on public perceptions of CDR, we carried out
a systematic search in February 2022 of the English-language academic databases Scopus
and Web of Science. A search for papers labelled as “public perceptions”, “attitudes” or“opinions” on CDR returned 36 papers99–114, with a further three new papers added in
September 202293,115,116. A large number of studies have been published on perceptions ofrelated techniques, such as CCS, bioenergy, forestry and ecosystem restoration. These were
only included in our review if they specifically discussed carbon dioxide removal. Thus, forexample, CCS of point-source emissions was not included, as it reduces CO2 rather thanremoving it. This may exclude a large body of work on carbon sink management, for example
forestry programmes such as REDD+ (Reducing emissions from deforestation and forest
degradation in developing countries), which may include the perspectives and experiencesof “frontline” communities. The literature we reviewed uses a number of methods forunderstanding public responses to CDR, including large representative surveys, experimental
approaches using surveys and questionnaires, and qualitative inquiries such as focus groups,
interviews and deliberative workshops. Despite low prior awareness, evidence shows thatthe general public is very capable of discussing complex and novel topics97.

43

The State of Carbon Dioxide Removal
16

Carbon Dioxide Removal (CDR) type
(number of scientiﬁc papers per year)

14
12
10

?

8
6
4
2
0

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

Year of publication
CDR

Geoengineering

Enhanced Rock Weathering

Aﬀorestation/Reforestation
Biochar

Ocean Fertilisation

Soil Carbon Sequestration

BECCS

DAC (CS)

Other

Figure 4.1. Evidence in the scientific literature on how people perceive Carbon Dioxide Removal (CDR) is growing but still small. The figure shows the number of research papers on public perception of CDR by year and CDR
method*. Total number of publications = 39. Many papers include more than one CDR method, so the total countsof publications across CDR methods in the graph adds up to more than 39. Data for 2022 includes January-September publications only. BECCS = Bioenergy with Carbon Capture and Storage, DACCS = Direct Air Carbon
Capture and Storage.

Our review found large regional disparities in the peer-reviewed research on public
perceptions of CDR. Only ten of the papers we reviewed researched public views outside ofWestern Europe and North America, of which only one was from Africa and two from East
Asia; none were from South America, Eastern Europe, or West/Central Asian regions (Figure4.2). This may be a limitation of our English-language sampling methodology, although someresearch papers also raise concerns about regional disparities117,118. Mitigation pathways thatmeet the Paris temperature goal, for instance those assessed by the Intergovernmental Panelon Climate Change (IPCC), often include scaling-up of CDR in precisely the regions wherescientific literature on public perceptions is absent.

* Studies on “geoengineering” include participant information and/or questions on both CDR and solar radiation management, meaningthat CDR is included as a component of “geoengineering”.

44The State of Carbon Dioxide Removal
Africa
(1)
East
Asia
(2)
Oceania(7)

Total numberof papers = 39*

North
America(13)

No research on public
perceptions of citizens
in Eastern Europe,
Latin America andCaribbean, or Western
and Central Asia

WesternEurope(27)*Many studies include
samples from morethan one country

Figure 4.2. Research on public perceptions of Carbon Dioxide Removal (CDR) shows large regional disparities,
with only a small proportion of studies from outside Western Europe and North America.

Public awareness of CDR
The scientific literature on public perceptions consistently finds low levels of awareness andknowledge of CDR in the populations of the countries studied, primarily Western Europe,
the US, Australia and New Zealand. Table 4.1 summarises key results from the small subsetof studies which contain quantitative awareness data. It is not possible to discern trends inthis data, due to the small number of studies and the fact that awareness is measured andreported in a wide variety of ways.

45

The State of Carbon Dioxide Removal
Table 4.1. Awareness of Carbon Dioxide Removal (CDR) is low among the general public in Western Europe, theUS, Australia and New Zealand. The table shows public awareness of CDR, quantitative findings only, by year ofdata collection and country. Where multiple statistics are reported, these correspond to the countries listed, inorder. Some studies aggregate across countries. Definitions: Bioenergy with Carbon Capture and Storage (BECCS)
and Direct Air Carbon Capture and Storage (DACCS).

Year Country

Method or CDR initiative investigated

Reported
statistic

MeasureReference

2012

Australia +BECCS + DACCS + En-

18%“Aware”

Carlisle et al. (2020)119

New Zealandhanced rock weathering

2013

Australia

Carbon Farming Initiative

39%“Aware”

Dumbrell et al. (2016)120

2013

Germany

Afforestation

60%“Heard of”

Braun et al. (2018)121

2016

United King-

Enhanced rock weathering

6.5%“Know great deal /Pidgeon & Spence

fair amount”(2017)122

dom
2018

United King-

BECCS

21.2%

“Know fair amount”

Bellamy et al. (2019)95

Afforestation

3.15 (out of 6)

6-point scale

Jobin & Siegrist

BECCS

2.22

1: “never heard of it” (2020)123

Biochar

1.68

6: “know a lot”

DACCS

2.09

Enhanced rock weathering

1.84

Ocean fertilisation

1.64

Soil carbon sequestration

2.07

Australia

BECCS + DACCS + En-

14%

New Zealandhanced rock weathering

15%

dom
2018

2018

Switzerland“Aware”

Carlisle et al. (2020)119

19%“Aware”

Carlisle et al. (2021)124

5.8%“Know great deal /Cox et al. (2020)93

9.6%

fair amount”

26%“Heard of”

United King-

16%

dom

18%

United States
2018
2019

United King-

BECCS + DACCS + En-

dom

hanced rock weathering

United King-

CDR

dom
United States
2019

Australia

Enhanced rock weathering

United King-

38%

dom

30%

Spence et al. (2021)117

United States

Risks, benefits and specific CDR methods
Research shows that people’s initial reactions to CDR are usually tied to their values, beliefs
and sense of identity. Specific factors include trust in the actors involved, beliefs about
tampering with the natural world, and perceived trade-offs against alternative approaches
for mitigating or adapting to climate change125. For novel CDR methods (see Chapter 1 –Introduction for definitions) with low public awareness, perceptions are highly susceptible
to how methods are framed by researchers. Deliberative research has shown that people
may support CDR methods provided they meet certain conditions regarding elements suchas impacts, risks, benefits and costs – for example, that they are feasible, controllable andreversible; that the side effects are minimal; and that scientific uncertainty is low93,126.

46

The State of Carbon Dioxide Removal
Perceptions of CDR also depend on the policy context. For example, support may
require a clear and joined-up approach to policymaking for climate action across sectors.
Otherwise, CDR may be perceived as simply a “band-aid” to the problem of continued highemissions115,121,127. The policy context will also need to attend to other environmental andsocial goals, because support for CDR may be lower if it creates the same harms that it tries
to avoid, for instance by damaging biodiversity or widening inequalities (see Table 1.1 in
Chapter 1 – Introduction for potential hazards associated with different methods). Anotherconcern about CDR is that it could reduce the incentive to tackle emissions128, and public
discourses around CDR are likely to evolve alongside emerging debates and concerns over“net zero” promises – in particular, whether CDR is simply a means of enabling particularsectors or sections of society to continue emitting CO2. A strong body of evidence frommultiple sectors demonstrates that attempting to overcome scepticism through campaigns toincrease public awareness, understanding or scientific literacy is likely to be ineffective andpotentially even counterproductive129,130. As innovation programmes gain pace, efforts toengage the public with CDR are vital but must go beyond notions of securing “acceptance”.
Studies find a preference among participants for CDR methods perceived or framed byresearchers as more “natural”, yet definitions of what constitutes “natural” are vague
and differ between studies. Familiar conventional land-based methods (particularly
afforestation) tend to be generally preferred over others94,120,123,131,132, and ocean
fertilisation tends to be perceived as most risky133,134. Less familiar novel CDR methods,
such as enhanced rock weathering and Direct Air Carbon Capture and Storage (DACCS),
often encounter uncertainty and a high proportion of “don’t know” responses 93,124. Landbased CDR methods encounter concerns about land use, biodiversity and environmental
impacts, although for some CDR methods such as afforestation this greatly depends on
how it is carried out. Bioenergy with Carbon Capture and Storage (BECCS) in particularappears to arouse concerns about land competition, food prices, biodiversity and thesustainability of feedstocks135,136. Research on methods involving underground CO2 storage
builds on a much larger body of literature on CCS perceptions and finds concerns aroundsafety, monitoring, leakage and earth tremors, and perceptions of the deep undergroundas unknowable and unpredictable93,135. Ocean-based CDR methods may be perceived as
most risky because of perceived uncontrollability and irreversibility, although this may also
depend on the degree to which the methods are perceived as “natural”98,123,131.

4.3 Tracking CDR on Twitter
Attention to CDR on Twitter has proliferated in recent years, growing faster than attention
to climate change in general. Some methods, such as afforestation/reforestation, arediscussed more favourably than others.
The social media platform Twitter is known for driving online political debates. Twitter datashows how communicators who are aware of CDR talk about it in public. The fact thatusers are dedicated communicators such as experts, policymakers, and media and company
representatives means that the results are not representative of general populations137–140.
Nevertheless, analysing this data allows us to track the development of communication
around CDR over time. In this chapter, we search and analyse English-language tweets inthe full Twitter archive (2010-2021). Our queries capture general CDR keywords as well as
those related to specific CDR methods (see Box 4.3).

47

The State of Carbon Dioxide Removal

Box 4.3 Method for analysing Carbon Dioxide Removal
on Twitter
We focus our analysis on ten Carbon Dioxide Removal (CDR) methods – DAC(CS)*,
coastal wetland (blue carbon) management, Bioenergy with Carbon Capture and Storage(BECCS), soil carbon sequestration, ecosystem restoration**, afforestation/reforestation,
biochar, enhanced rock weathering, ocean fertilisation and ocean alkalinisation – as wellas general CDR mentions.
For each of these, we develop and test a set of keywords in an iterative process toretrieve tweets from the Twitter full-archive search application programming interface(API) during the period 2006-2021. We download tweets separately for each set of
keywords, excluding non-English tweets and retweets. In addition, we use the Twittercount API to get estimates of the volume of all English-language tweets on Twitter, as wellas the number of tweets mentioning “climate change”.
In total, our consolidated dataset contains 471,386 unique tweets on CDR (both generalmentions and mentions of specific methods). These tweets were posted by 171,233 distinct
users, of which the most active 1% contributed 28% of the tweets. The tweets in ourdataset were retweeted 1,004,533 times and received 200,055 replies and 2,776,170 likes– which is on average 2.1 retweets, 0.4 replies and 5.8 likes per tweet. Of the tweets in thedataset, 16,587 (3.5%) were matched by more than one query. Our dataset only contains
original tweets containing at least one of the keywords from our search strings. These may
be part of a conversation but do not include all other tweets in that conversation.
For each CDR method, as well as the general CDR keywords, we (1) measure attention
by counting the number (and proportion) of tweets and (2) apply sentiment analysis tounderstand the tone of each statement, using the aggregated information as a proxyof perceptions towards CDR methods. We automatically label sentiment in our dataset
using a state-of-the-art, transformer-based classification model141 trained on public goldstandard training data142.
There are several limitations of such an analysis. First, Twitter data is not representativeof the general public, which can lead to differences in our analysis compared withrepresentative surveys. However, we argue that the data is particularly useful for new
and emerging technologies that are not yet well known among the broader population,by providing a large archive of statements by a large number of people with a generalawareness of these CDR methods119,134. Second, our search for tweets is optimised toprovide a high share (>80%) of relevant tweets (high precision), at the expense of not
retrieving everything said about CDR on Twitter (lower recall). Third, we focus on Englishlanguage tweets only. This means that considerable parts of Twitter activity with respect
to CDR are not represented here – particularly in non-English-speaking parts of theworld. Fourth, reactions on Twitter might be biased by algorithmic prioritisation of tweetsthat users are presented with, and by bots. Fifth, since Twitter was only founded in 2006,
the quantity and quality of tweets are influenced by the Twitter company’s continuous
development and growth of its user base. To this end, we exclude the early years from
our analysis and focus on the timeframe 2010-2021.
*The keywords used for this allow for mentions of both Direct Air Capture (DAC) – which does not include utilisation andstorage - as well as for Direct Air Carbon Capture and Storage. These additional steps are necessary for this to be classified
as a CDR method. We therefore refer to DAC(CS) in this section, as distinct from DACCS, and recognise that these mentions
may not necessarily refer to the entire CDR method but may only include the capture component without storage.
**The keywords used for this allow for mentions that go beyond the peatland and wetland restoration method outlined in
Chapter 1 – Introduction.

48

The State of Carbon Dioxide Removal
Overall attention to CDR on Twitter
The public Twitter debate on CDR is still young. Since the start of Twitter in 2006, about
470,000 English-language tweets on CDR-related topics have been shared on the platform(see Box 4.3). This is comparatively small given that there are tens of millions of tweets on
climate change143.

AR6 WGI release
COP26 Glasgow

COP24 Katowice

SR15 release

COP23 Bonn

COP22 Marrakech

COP21 Paris

COP20 Lima

COP19 Warsaw

800

UN Climate action summit
COP25 Madrid
Covid-19 pandemic declared

Daily tweet count (7-day moving average)

1000

COP18 Doha

However, attention to CDR on Twitter has grown rapidly in recent years – faster than thenumber of tweets on climate change overall. In the observed period from 2010 to 2021,
the number of tweets on CDR increased from about 5,500 (~15 tweets per day) to about
130,000 (~350 tweets per day) – an average growth rate of about 33% per year (Figures
4.3 and 4.4). This is faster than the growth in tweets on climate change (~10,000 per day
in 2021, with 28% annual growth) and the average increase in the total number of tweets
posted on the platform (17% per year).

600

400

200

0

Figure 4.3. Attention on Twitter is driven by events, particularly the annual United Nations Framework
Convention on Climate Change (UNFCCC) Conferences of the Parties (COPs). Number of tweets on Carbon
Dioxide Removal (CDR) per day shown as 7-day moving average (2010-2021). Attention spiked during the COPs
and the releases of the Intergovernmental Panel on Climate Change (IPCC) Special Report on Global Warmingof 1.5°C (SR15) and the Working Group I contribution to the Sixth Assessment Report (AR6 WG1). The peak in2019 is related to the release of a high-profile scientific paper on global forest restoration144.

Due to the outbreak of the Covid-19 pandemic in early 2020, attention shifted away from
CDR temporarily. However, attention quickly recovered in 2021, faster than the number oftweets on the general topic of climate change; the number of tweets was about 75% higher
than in 2020 and 62% higher than in the years before the pandemic (Figures 4.3 and 4.4).
General versus specific aspects of CDR
About 30% of all CDR-related tweets concern general aspects of CDR, responding to general

49

The State of Carbon Dioxide Removal
keywords such as “carbon dioxide removal”, “carbon removal” or “negative emissions”. Overtime, this share has increased from 3% in 2010 to 27% in 2021 and has grown faster than
all CDR-related tweets together. In 2021, there were about 46,000 general CDR tweets
discussing topics such as corporate plans to compensate emissions, the necessity of using
CDR, or carbon-neutral products. This now regular and frequent reference to general
aspects of CDR highlights the establishment of CDR as a part of the climate policy debate inits own right on Twitter.
Tweets that mention terminology related to specific CDR methods – such as afforestation/
reforestation, coastal wetland (blue carbon) management, BECCS and DAC(CS) (see Box 4.3
for the full set) – account for about 70% of tweets in our dataset.
Attention to different CDR methods varies widely. More than 70% of all method-specifictweets are about CDR methods using biological storage: soil carbon sequestration (91,000
tweets; 27%), afforestation/reforestation (81,000 tweets; 24%), and coastal wetland (bluecarbon) management (75,000; 22%) are all characterised by sizeable and continuously
growing Twitter conversations. The debate on ecosystem restoration (20,000 tweets; 4%) is
considerably smaller but is the fastest growing among these methods.
Novel CDR methods such as BECCS and DAC(CS) have received comparatively moderatelevels of attention, but the number of tweets on DAC(CS) has seen substantial growth, at
an average rate of about 57% per year over the last decade. Twitter activity on DAC(CS)tripled from 2020 to 2021, mirroring rapid dynamics in DAC(CS) investments (see Chapter
3 – Innovation). Similarly to the scientific literature (see Chapter 2 – Research landscape),
enhanced rock weathering and ocean alkalinisation still receive little attention.

50

The State of Carbon Dioxide RemovalA
CDR (general)
CDR methods

120,000

Yearly tweet counts

100,000

80,00060,00040,00020,000

0

B

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2010

2011

2015

2016

2017

2018

2019

2020

2021

Coastal wetland (blue carbon) management

2012

2013

2014

BECCS

Soil carbon sequestration

100

Yealy tweet shares (%)

80

60

40

20

0

Direct air capture (DAC)
Aﬀorestation/Reforestation

BiocharEnhanced rock weathering

Ocean alkalinisation

Ecosystem restoration

Ocean fertilisation

General CDR

Figure 4.4. Number of tweets per year on general Carbon Dioxide Removal (CDR) and method-specific CDR(panel A). Relative shares of overall CDR tweets by method (panel B). General CDR discussions that do not feature
specific CDR methods are reported under CDR (general). Definition: Bioenergy with Carbon Capture and Storage(BECCS).

Sentiments in tweets on CDR
The sentiment of tweets refers to whether the tone of the message is positive, negative
or neutral. Sentiments do not directly reflect the stance of Twitter users towards a CDR
method, for example whether they support or oppose a specific CDR method. However,sentiments reveal whether a CDR method appears more often in a rather positive or
negative context.

51

The State of Carbon Dioxide Removal
Compared with tweets on CDR methods, a smaller share of tweets on general aspectsof CDR – responding to keywords such as “carbon dioxide removal”, “carbon removal” or“negative emissions” – have a neutral sentiment, and that fraction is shrinking over time.
However, the shares of positive and negative sentiments remained mostly balanced until
a trend towards more positive sentiments emerged over the last three years (2019-2021),
perhaps pointing toward an increasingly favourable framing of CDR on Twitter.
Tweets on individual CDR methods feature higher shares of positive than negative
sentiments, except for ocean fertilisation. Ocean iron fertilisation is discussed very negatively
following some failed field experiments145. This also corresponds to widespread scepticism
found both in the scientific community and in public perceptions research with regard toits effectiveness and side effects3. The tone of tweets on afforestation/reforestation andbiochar is more positive and less negative than for other CDR methods. This is also true forenhanced rock weathering, but the small number of tweets may skew the result. Most CDR
methods show trends towards more positive tweeting over time. Only for BECCS do we findnegatively trending sentiments. This may reflect growing concerns in the public debate about
associated risks, as identified in perceptions studies (see Section 4.2).

Sentiment
Negative

Tweet countPositiveTrend in sentiment
2006–2021

CDR (general)
Ocean fertilisation
Enhanced weathering
Ocean alkaliisation
BiocharAﬀorestation and reforestation
Ecosystem restoration
Soil carbon sequestration
BECCS
Blue carbon management
DAC (CS)
-40

-20

0

20

Share of tweets (%)

40

050,000100,000

150,000

Number of tweets

Figure 4.5. Share of original tweets on Carbon Dioxide Removal (CDR) that express either a positive or negative
sentiment (2010-2021); trends in sentiment (positive - green arrow; negative - red arrow) over time; tweet counts
for different CDR methods (2010-2021). Definitions: Bioenergy with Carbon Capture and Storage (BECCS),
Direct Air Carbon Capture (DAC) and Direct Air Carbon Capture and Storage (DACCS).

52

The State of Carbon Dioxide Removal

4.4 Future needs
Engaging the public with CDR requires policymakers and investors to understand thenuances of how different methods are perceived, extending beyond English-language
scientific literature.
Meeting the Paris temperature goal will require maintaining carbon sinks from conventional
CDR on land and most likely also substantial scaling-up of novel CDR. It is well established in
the scientific literature that perceptions of CDR by investors as well as the general public caninfluence the speed and direction of innovation and deployment.
Our analysis here highlights that public awareness of CDR as reflected in English-language
social science studies is still fairly low. This may be related to low awareness amongst
policymakers, reflected in the lack of concrete plans to scale CDR in many countries
and regions of the world (see Chapter 5 – Policymaking). Analysing and understanding
the public debate on CDR-related issues, especially method-specific topics, is therefore
critical, especially in the coming years as CDR methods are deployed in response to net
zero commitments by governments and companies. There is a need to extend the analysis
of public perceptions beyond English-language and scientific literature to further specify
insights and knowledge gaps in other contexts.
Our Twitter analysis also shows that attention to CDR is growing rapidly and that these
discussions feature an increasingly positive tone. Real-time tracking of public perceptions
using social media platforms such as Twitter, Facebook, Reddit and other locally relevant
networks could provide a sort of “early warning” system for shifts in CDR debates.
However, such analysis can only contribute to robust social science alongside mixed methods
approaches that generate qualitative insights in situations where participants have low priorknowledge of the investigated CDR methods. In addition, as CDR moves from research into
deployment, local issues are likely to come to the fore, for instance around demonstrationand scale-up projects, siting proposals, and policy implementation. This will require much
more attention to spatial dynamics, perceptions of specific stakeholder groups (notably
those directly involved in and affected by CDR deployments, and frontline and “fenceline”
communities) and the existence of many diverse “publics”.

53

“While many countries havecommitted to net-zero emissions
targets, few have robust plans or
policies on how to achieve CDR.”

The State of Carbon Dioxide Removal

Chapter 5 | Policymaking
Chapter team: Oliver Gedeni, Felix Schenuiti, Annette Cowieii, Aniruddh Mohaniii, Glen Petersiv, Stephen M Smithv, JoseMaria Valenzuelav
German Institute for International and Security Affairs
New South Wales Department of Primary Industries/University of New England, Armidale, Australiaiii
Princeton University
iv
CICERO Center for International Climate Researchv
University of Oxfordiii

Where examples of dedicated Carbon Dioxide Removal governance exist, they are foundprimarily at the level of individual countries and the European Union. Guidance andincentives from the United Nations Framework Convention on Climate Change and othermultilateral initiatives are limited in comparison.

Box 5.1 Key findings•

More than 120 national governments have set a net-zero emissions target, yet onlya small minority explicitly integrate Carbon Dioxide Removal (CDR) into their climate
policy.

•Four case studies (European Union, United Kingdom, United States and Brazil) showtangible progress and policymaking dedicated to CDR. However, even in these cases
no explicit removal targets or robust plans on how to achieve them exist.

•

Policymakers’ focus to date has been on conventional CDR on land, through forestry
and agriculture. Attention on Bioenergy with Carbon Capture and Storage, Direct Air
Carbon Capture and Storage and other novel CDR methods is rising in all four cases,
especially in the UK and the US.

•

The UK and European Union mainly refer to CDR as an option to counterbalance
residual emissions in the context of a net zero target. In the US and Brazil, reducing
emissions in the short term plays a larger role. None seriously considers reaching netnegative emissions.

•

Understanding the conditions that influence upscaling of CDR will continue to requirecase studies that take into account countries’ respective political contexts.

5.1 Growing recognition of Carbon Dioxide
Removal in climate policy
More than 120 national governments have a net-zero emissions target, which implies
Carbon Dioxide Removal (CDR).
Governments’ approval of the recent Intergovernmental Panel on Climate Change (IPCC)
Working Group III report shows they recognise that alongside deep, rapid and sustained55

The State of Carbon Dioxide Removal
emissions reductions, CDR can fulfil three complementary roles1: further lowering net
emissions in the near term; counterbalancing hard-to-abate residual emissions (for example,
from agriculture, aviation, shipping and industrial processes) in order to reach net-zero CO2
or greenhouse gas (GHG) emissions in the medium term; and achieving or sustaining netnegative emissions in the long term if deployed at levels exceeding annual residual emissions(see Chapter 1 – Introduction and Figure 5.1). The global mitigation pathways assessed in
the same IPCC report show conventional CDR on land maintained throughout the century,
while novel CDR methods scale up over time (see also Chapter 7 – Scenarios and Chapter 1– Introduction for definitions of “conventional” and “novel”).

Greenhouse gas emissions (stylised pathway)

Net GHG emissions

Emissions: Non-CO2 GHGs
Emissions: Fossil CO2

Net CO2 emissions

Emissions: Managed land
Removals: Conventional CDR on land
Removals: Novel CDR methods

Gross emissions
Net zeroNet zero
Gross CO2 removals(1) Before net zero(2) Net zero CO2 or GHG

2010(3) Net negative
2100

Figure 5.1. Roles of Carbon Dioxide Removal (CDR) in ambitious mitigation strategies, applicable at national andglobal level. Basic emission and removal components of mitigation pathways, and the corresponding trajectories
for both net carbon dioxide (CO2) and greenhouse gas (GHG) emissions. (Adapted from Cross-Chapter Box 8,
Figure 2 in Babiker et al. 202213).

CDR has climbed up national policy agendas in recent years. While deploying conventional
CDR methods on land is already well established (see Chapter 6 – Deployment),
governments have now begun to envisage and specify the role of CDR in their domestic
climate strategies, either explicitly through CDR-specific policies and strategies, or implicitly
through the adoption of national net zero targets. More than 120 governments have set net
zero targets to date2.

5.2 Limited commitment to developing CDR
While few governments have actionable plans for developing CDR, some countries are
beginning to integrate CDR into their climate policy, in different ways.
While, in principle, national governments are starting to recognise the strategic role that
CDR will have to play in meeting agreed climate targets, governmental action on CDR isfalling short. For example, although setting a net-zero (rather than a zero) emissions target

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The State of Carbon Dioxide Removal
implicitly indicates that governments are counting on CDR in some form, robust plans
for CDR implementation are scarce. Reflecting a more general deficiency of net zeroannouncements146, governments usually do not express how large the contribution of CDR
should be on reaching net zero, and which CDR methods this might entail.
Examples of dedicated CDR policy and governance are found mainly on national and (in thecase of the European Union) supranational levels, and only to a very limited extent in global
multilateral initiatives and the United Nations Framework Convention on Climate Change(UNFCCC).
Governance at UNFCCC level
The Paris Agreement stipulates in its Article 4.1 that a “balance between anthropogenic
emissions by sources and removals by sinks of greenhouse gases” should be achieved “in thesecond half of this century” (see Chapter 1 – Introduction). Furthermore, all IPCC mitigation
scenarios that likely limit warming to 2°C or lower assume the use of CDR (and almost all that
limit warming to 1.5°C assume net-negative CO2 emissions) (see Chapter 7 – Scenarios). Yet
this has not so far been mirrored by corresponding UNFCCC decisions on the global needfor large-scale CDR147,148. While the negotiations of CDR-specific issues are nascent, recent
developments in the context of implementing the Paris Agreement’s Article 6 on international
cooperation indicate that the UNFCCC could play a more active role in the near term.
Additional efforts to develop methodologies for monitoring, reporting and verification (MRV)of carbon flows would be an important step towards operationalising CDR as part of mitigation
strategies (see Chapter 1 – Introduction, Table 1.1, for an overview of current MRV guidance).
Governance at the UNFCCC level extends to a request for national governments to submit
Long-term Low Emission Development Strategies (LT-LEDS). In contrast to the Nationally
Determined Contribution (NDC), submitting an LT-LEDS is not mandatory for parties to
the Paris Agreement and no requirements on format or content exist (see Chapter 8 – The
CDR gap for further details of the ambiguities of LT-LEDS). By September 2022, there were
only 53 LT-LEDS, some of which do contain considerations on preferred CDR methods andmodelling data indicating CDR at the intended time of reaching net-zero emissions. But nonecontains a target for CDR combined with a politically robust plan for how to achieve it149.
While this might be due to the long-term perspective of these strategies, this also holds true
for NDCs, which usually focus on 2030. National legislation is also often more up to datethan LT-LEDS, meaning the latter cannot be taken as a primary reference for commitments.
While the NDCs of many countries have been regularly updated since 2015, they usuallyrefer only to CDR through the UNFCCC inventory category Land Use, Land-Use Change andForestry (LULUCF). Detailed reporting on this sector is already mandatory for developed
countries and captures emissions and removals on “managed land”150,151. However, NDCs
referring to conventional CDR on land show a high degree of ambiguity (for example, on
the separate contributions of LULUCF emissions and removals) and use widely differing
accounting approaches, which is allowed under the Paris Agreement152,153.
At the level of UN climate negotiations, specific CDR methods such as Bioenergy with
Carbon Capture and Storage (BECCS) or net-negative emissions trajectories to deal withtemperature overshoot are not yet covered147,154. Only a few national long-term mitigationplans or legal acts envision achieving net-negative GHG emissions149. For example, Finland,
Sweden and Germany include such objectives in national legislation.

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National and supranational policymaking
As reporting practices under the UNFCCC currently cover only two facets of CDR
governance (target setting via NDCs and LT-LEDS, and accounting for removals via national
GHG inventories151), exploring paths to scale up CDR requires a closer look at national andsupranational policymaking. Unsurprisingly, CDR policymaking is shaped by the dominantways climate policy works in a given country155. Of particular significance are the incentive
structures for CDR deployment and the distributive effects of envisaged CDR upscaling (e.g.
who bears responsibility for delivering and paying for removals).
Only a small minority of the 120 national governments that have set a national net-zeroemissions target have started explicitly integrating CDR into climate policymaking. This
exists in various forms, such as setting explicit targets; modelling scale-up of CDR in national
mitigation pathways; increasing Research, Development and Demonstration funding for CDR(see Chapter 3 – Innovation); or implementing CDR-specific incentives and policies156,157.
Comparative case studies have identified different types of CDR policymaking157. Here,
we provide snapshots of CDR policy in practice via four illustrative case studies. Focusing
on the European Union (EU), the United Kingdom, the United States and Brazil, we cover
three Organisation for Economic Co-operation and Development (OECD) economies thathave started to govern CDR in different ways and one country projected to provide pivotal
CDR capacity in modelled global mitigation pathways158 (see Chapter 3 – Innovation forcomplementary information on public funding for Research and Development). While all
four have recently enhanced dedicated CDR regulation, these case studies reveal importantsimilarities and considerable differences in the way CDR is regulated, which are not apparent
in the reporting practices under the UNFCCC.
CDR policy in practice: European Union, United Kingdom, United States and Brazil
European Union
While the EU has been critical of the inclusion of CDR in mitigation strategies in the past,
CDR has received new impetus in the context of the European Green Deal. The adoption ofa legally binding target of net-zero GHG emissions by 2050 and net-negative GHG emissions
thereafter (as yet unquantified) codified the need for CDR159,160. In recent years, CDR has
become an integral part of the EU’s mitigation policymaking. The original economy-wide
2030 goal adopted in 2014 of achieving a GHG emissions reduction of 40% (compared
to 1990 levels) had targeted only gross emissions. The European Climate Law passed in
2021 strengthened the 2030 target to at least 55% net emissions reductions with a limited
contribution of net removals from LULUCF (225 MtCO2e). Furthermore, the European
Commission, a few Member State governments and individual Members of the European
Parliament have been pushing for the development of CDR incentives and regulation161,162.
As part of its Sustainable Carbon Cycle initiative, the Commission plans to increase
incentives for all LULUCF-based CDR methods (under the term carbon farming), expand
support for innovation in Carbon Capture and Storage (CCS)-based CDR methods such as
BECCS and Direct Air Carbon Capture and Storage (DACCS), and establish a certification
framework for a broad range of CDR methods.
The EU Member States and the European Parliament are still in the process of identifying
and agreeing on their positions on CDR. Some Member States (for example, Denmark,
Netherlands and Sweden, together with closely associated non-EU member Norway) arepushing for the rapid and full integration of CDR into the EU’s climate policy architecture,
while others have yet to articulate specific preferences. No Member State opposes CDR

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outright, and all but a few (such as Ireland, Netherlands and Denmark) have achieved
net LULUCF removals over the last decade. Since climate policy is a domain where thecompetence to act lies mainly at the supranational EU level, the development of an
overarching CDR governance structure will be based on a common approach. Yet national
differences in CDR deployment are expected to persist due to varying geographies, sociopolitical preferences and expected compositions of “hard-to-abate” residual emissions163.
The strengthened LULUCF Regulation establishes a new target of achieving 310 MtCo2e
net removals by 2030, which will likely lead to new support and incentive structures forthe implementation of conventional CDR on land in the coming years. The EU Innovation
Fund (fed through revenues from the EU Emissions Trading System) is so far the main tool
to support the development of novel CDR methods, complemented by funding through theEU’s research and innovation programme Horizon Europe (see also Chapter 3 – Innovation).
One CDR demonstration project is already co-financed through the EU Innovation Fund
(Beccs Stockholm88), in addition to projects that fall under the broader category of “carbon
management” (i.e. capture, utilisation, transport or storage of fossil CO2), which will shape thefuture expansion of CDR. Industry is beginning to advocate for the development of CDRrelated infrastructure, such as CO2 transport. Companies with large amounts of potentiallyhard-to-abate emissions are starting to call for cross-border collaboration on carbon
management, including CDR.
United Kingdom
CDR is a topic of proactive research and policy development in the UK157, where it isoften referred to as Greenhouse Gas Removal (GGR) to include potential removal of othergreenhouse gases. The most recent strategy published by the government emphasises theprimacy of ambitious decarbonisation across society, while noting that Greenhouse Gas
Removal is essential to compensate for residual emissions67.
UK climate policy is guided by legislation which requires five-year limits on net domestic
GHG emissions (known as “carbon budgets”) to be set on the path to at least a 100%
reduction in net GHG emissions (i.e. net zero) by 2050. Within these targets, CDR’s roleis not separated from emissions reduction but is accounted for as fully exchangeable withemissions. The legislation requires the government to regularly publish its plans and policies
for achieving these targets. The most recent strategy publication contains an ambition toincrease tree planting to 30,000 hectares per year from 2025 onwards, restore 280,000
hectares of peat in England by 2050, increase use of wood in construction, and remove atleast 5 MtCO2 per year by 2030 with methods like BECCS, DACCS, biochar and enhancedrock weathering67. Currently only CDR reported in the land sector is counted towards UK
targets. The government’s strategy seeks to amend the legislation to account for a wider
range of CDR methods, and explore new regulatory oversight for MRV.
The UK has generally adopted carbon pricing and market-based approaches to support
climate change mitigation. Tree planting is incentivised through a government-createdsystem of MRV and credit generation for woodland carbon164. Consultations have beenlaunched by the national government in 2022 on business models for CDR methods like
BECCS and DACCS165,166 as well as discussion in the context of developing the UK Emissions
Trading System (ETS)167. These consultations indicate that the government currently intends
to incentivise such methods through contracts guaranteeing a fixed price per tonne of CO2
removed.
CDR Research and Development is supported in the UK primarily through two programmes.
These total £100 million ($113 million) over four years and include a range of demonstration

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The State of Carbon Dioxide Removal
projects and a research hub (see Chapter 3 – Innovation for further details). A wide variety
of methods is supported in these programmes (for example, CO2 capture from seawater andcapture of methane from cattle sheds), in addition to those included for deployment in thenational net zero strategy.
Despite this relatively high level of policy ambition in the UK, progress is lagging. The
government’s official advisory body reports that tree planting and peat restoration are
significantly behind targets, while the delays to CCS development in the UK are a particularrisk to BECCS and DACCS deployment168.
United States
The US’ NDC aims to cut GHG emissions by at least 50% in 2030 compared to 2005 levels,
including LULUCF169 (annual net removals via LULUCF were roughly 10-15% of total US
GHG emissions in the past decade169,170). The Biden administration has also announced
additional targets, including achieving net-zero GHG emissions economy-wide by 2050.
There is no federal legislation with emissions reduction targets consistent with the US NDC,
nor to achieve net-zero GHG emissions by 2050. As such, the envisaged contribution of
CDR in US climate policy is unclear. Modelling analyses indicate that achieving net-zero GHG
emissions in the US will involve a significant role for CDR, on the order of 1 GtCO2 per yearby 2050171.
CDR has received bipartisan support despite the lack of consensus on climate change in US
politics157. Partly, this is because methods like DACCS and BECCS are seen as technologicalinnovation with broader economic benefits. Methods such as soil carbon sequestration
have also received bipartisan support as they may benefit more rural states, which havedisproportionately high political representation. Several recent federal bills have CDR
components. For instance, the bipartisan Energy Act of 2020, signed into law by the Trumpadministration, allocated funding for an interagency CDR research programme and set up
a technology prize competition for Direct Air Capture (DAC) (see Chapter 3 – Innovation).
In 2021, the bipartisan Infrastructure Investment and Jobs Act assigned $3.5 billion to four
DAC hubs, including connecting infrastructure such as pipelines and storage. The goal isto achieve 1 MtCO2 capture per year per hub. While these hubs are expected to catalyse
investment in subsequent DAC plants, it is unclear to what extent the initially captured CO2
will be utilised for short-lived products like synthetic fuels, rather than being durably stored.
The Inflation Reduction Act (IRA) of 2022 includes major changes to an uncapped tax
credit – 45Q – which supports CCS projects of all kinds. The credit was originally enacted
in 2008 for fossil CCS. It has undergone multiple revisions in the past decade. The valueof this directly paid credit for DAC combined with geological storage has been increased
to $180 per tonne of CO2. IRA also lowers the threshold to claim this credit from 100,000
tCO2 captured annually to just 1,000 tCO2 per year, making the credit much more attainable
for current and future DAC facilities. While IRA’s investments in fossil CCS do not count as
CDR, the associated build-up of infrastructure such as pipelines and geological storage canbenefit CDR methods such as DACCS and BECCS. There is also roughly $20 billion in the
IRA allocated to methods such as afforestation/reforestation and soil carbon sequestration.
Finally, the US Department of Energy launched the Carbon Negative Shot programme in
2021, which targets innovation across multiple CDR approaches to enable capture andstorage at gigatonne scale for less than $100 per tonne of CO273. Given that MRV withrobust standards does not currently exist for many methods – either globally or nationally– the Carbon Negative Shot also targets the development of MRV methods to “ensure
effective and permanent CO2 removal”73.

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BrazilThe deployment of CDR in Brazil is pursued through public and private sector initiatives,
particularly in agriculture and nature conservation. In April 2022, the Bolsonaro government
updated its NDC, committing to net-zero GHG emissions by 2050 without details on thebalance between emissions reductions and removals, and without an explicit CDR strategy.
Under the government of President Lula de Silva, the addition of Climate Change to the nameof the Ministry of Environment and the proposed creation of a National Climate Security
Authority (Autoridade Nacional de Segurança Climática) signal a new impetus to climate policy.
In May 2022, the Brazilian government issued a decree to establish sectoral mitigation plans
and a national registry that differentiate GHG removals and emissions reductions172. Under
the current policy trajectory, CDR actions will be subsidiary to sectoral strategies – rather
than considering CDR as a new independent sector. In the energy industry, for instance, therevised domestic fuel standard (RenovaBio) and tradable certificate system is expected toincentivise the addition of point-source carbon sequestration into biorefineries, with at least
one project already announced173,174.
Companies and NGOs have already developed reforestation and restoration programmes
as part of international voluntary emissions compensation schemes. According to the latest
inventory data, in 2020 net LULUCF emissions were 637 MtCO2e, amounting to 38% of thenational balance175. After a decade of progress, the decline of deforestation halted in 2012,
followed by a sharp rise after 2018176. Unless the deforestation trend is reversed in linewith the existing legal framework177, achieving net-zero emissions is not plausible. However,restoration and reforestation activities are scaling up in biomes affected by centuries-old
deforestation178, as in the Atlantic Forest. These are driven by priorities such as ecosystemconservation, biodiversity protection and water management, rather than CDR. Such
activities are enabled by partnerships including environmental NGOs and federal and local
governments, with financing from private sources. In these initiatives, CDR is an additionalco-benefit.
The most relevant developments have occurred in agriculture, which represents 28.5%
of national GHG emissions175. Today, business groups participating in global commodity
markets are interested in compensating for emissions occurring within the same sector.
This was preceded by a decade-old programme called the Low Carbon Agriculture Plan orPlan ABC, to finance the recovery of degraded pastures, the use of crop-livestock-forestry
integrated systems, no-till systems and biological nitrogen fixation179. In fact, restoration ofgrazing land, integrated crop-livestock systems and no-till farming were already consideredwithin Brazil’s Copenhagen Accord submission and later as part of the country’s Nationally
Appropriate Mitigation Actions (NAMAs)180,181. The convergence of the pre-existing Plan
ABC and new business initiatives is best captured by the recent development of a standard
for GHG-neutral agricultural commodities. The state-owned Brazilian Agricultural Research
Corporation (Embrapa) has developed the protocol which, for example, allows companies
to label meat as GHG neutral (Carne Carbono Neutro) when having deployed soil carbon
sequestration182,183. The results of an ongoing soil census as part of the National Soils
Program will provide a benchmark and additional information to accelerate this initiative184.
Summary of case studies
Specific policy approaches to CDR vary from country to country and are shaped byrespective climate policy paradigms and institutional architectures, by political interests,
by the relevance of different actors and by the relative importance of different economic
sectors, among other factors.

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To establish new funding and revenue streams, the US has expanded tax credits as oneof the most prominent tools to support CDR deployment, whereas the UK and the EU
are investing in innovation funds. In Brazil, there is no major funding for CCS-based CDR
methods, but the government has established large programmes to promote CDR in the
LULUCF sector. While none of the four cases has adopted an explicit target for novel CDR
yet, all are pursuing a deeper integration of CDR into climate policy, including throughadvancing MRV and standards for removal accounting to further operationalise CDR as animportant element of the mitigation toolbox.
Additionally, the different roles that CDR can play in mitigation strategies are not consideredequally in the cases presented here:• In the EU and UK, where much attention is being paid to reaching net-zero GHG
emissions, scaling up CDR is mostly seen as a means to counterbalance hard-to-abate
residual emissions. The UK has always applied the principle of full and unlimited
fungibility to its climate targets (i.e. emissions reductions and removals are treatedas interchangeable and mutual substitutes in accounting practices). The EU, on theother hand, has only recently moved to a net emissions logic for its domestic climate
targets.
• In the US, where no federal law targeting net-zero emissions has yet been enacted,
recent reforms suggest that CDR’s near-term role in reducing net emissions is alreadya key consideration.
• Brazil illustrates a development that is relevant in all four cases but is particularly
visible here: CDR policy is shaped by aspects that go beyond climate policy, and amultiplicity of possible justifications for CDR policy exist (e.g. managing interests ofimportant economic sectors like agriculture through promising additional revenue
streams).
• None of the case study countries gives any indication of planning for achieving
net-negative emissions. The EU is the only case where a formal net-negative GHG
target has been adopted, but it does not appear to drive current CDR policy development.
• Policy approaches and integration patterns also vary from method to method in thecase studies. While novel methods like BECCS and DACCS tend to be part of new
industrial policy initiatives, previous policy designs and governance structures forbiological CDR methods that do not involve CCS are shaped by different interests.
Conventional CDR on land mainly tends to be addressed by agriculture and forestry
governance185,186.

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5.3 Future action
In the near term, innovations in CDR governance and policymaking are mainly expected atnational and supranational levels. Tailoring to specific country contexts will be key.
At the UNFCCC level, the main task in terms of CDR policy and governance lies indeveloping robust accounting rules for CDR and establishing trusted MRV frameworks151,187,
strengthening rules for reporting on land-based biological removals and creating additional
guidance for methods like DACCS or enhanced rock weathering13. This will be relevant not
only for national inventory reporting but also in the context of establishing international
carbon trading under the Paris Agreement’s Article 6.4 mechanism. Yet UNFCCC inventoryrules – currently based on IPCC guidelines from 2006 and 2019 – are unlikely to change
without the explicit request of national governments, primarily those that want to havethe outcomes of DACCS or enhanced rock weathering recognised in their official national
inventories, thereby helping reduce net emissions and fulfilling pledges made in NDCs.
Beyond the UNFCCC process, action at a multilateral level can be expected primarily in fora
like the CDR Mission under Mission Innovation, established at COP26 in 2021 with an official
goal of enabling “CDR technologies to achieve a net reduction of 100 million tons of CO2
per year by 2030”188. While limited institutional capacity may hamper achievement of thisgoal, this platform co-led by the US, Saudi Arabia and Canada may contribute to enhanced
governance and policymaking through facilitating exchange of best practices and mutual
learning on technology development and MRV frameworks for novel CDR methods.
Looking closer into case studies and identifying commonalities and differences in governanceand policymaking practices will continue to be crucial to understanding the various
enabling and constraining conditions that influence upscaling of CDR, including shared
physical infrastructure (e.g. for CO2 transport and storage). This is because even in the
hypothetical case that all governments submit LT-LEDS, provide regular updates and use
more standardised formats – including more explicit information on intended volumes andtypes of CDR – there is usually a significant degree of inconsistency between climate policy
decisions and actions189. This leads to substantial implementation gaps190. Capturing realworld dynamics will therefore continue to require case studies that take into account therespective political contexts in which the enhancement of CDR emerges as a sub-domain ofclimate policy.

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“CDR from novel methods
contributes 0.1% of current
deployment. Conventional CDR
on land accounts for over 99%.”

The State of Carbon Dioxide Removal

Chapter 6 | Deployment
Chapter team: Carter Powisi, Stephen M Smithii

University of Oxford

The amount of Carbon Dioxide Removal (CDR) currently occurring around the world isroughly 2,000 MtCO2 per year, of which almost all comes from conventional methods on
land. However, accurately estimating CDR deployment is challenging.

Box 6.1 Key findings•

We estimate the amount of conventional Carbon Dioxide Removal (CDR) currently
occurring on land (for example, through afforestation and reforestation) is 2,000
MtCO₂ per year.

•

Adopting the methods used by countries to report their emissions and removals
on land increases this estimate to 6,400 MtCO₂ per year. This is because national
greenhouse gas inventories use a less strict interpretation of removals from humanactivity, including indirect effects.

•

We estimate an additional 2.3 MtCO₂ per year of CDR from novel CDR methods,
including Bioenergy with Carbon Capture and Storage, Direct Air Carbon Captureand Storage, biochar, enhanced rock weathering and coastal wetland (blue carbon)
management.

•

If all novel CDR projects currently under development are completed, the grossamount of novel CDR projects will increase to 11.75 MtCO₂ per year by 2025.

•

Currently available data for novel CDR focuses on gross removals from projects in
Europe and North America, with limited coverage of lifecycle emissions and othergeographies. This means our estimate of deployment is likely incomplete.

6.1 Our approach to estimating global Carbon
Dioxide Removal deployment
Estimating global Carbon Dioxide Removal (CDR) deployment is challenging, given
uncertainty around defining what counts as CDR, data availability and issues with reporting
approaches.
Generating an estimate of the amount of CDR currently occurring requires solving three main
challenges. The first is defining which activities should be considered as CDR. The second isgathering sufficient data on those activities. The third is developing a reporting approach that
addresses the risk of overestimating total deployment in cases where the CDR process takes
many years to complete.

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Challenge 1: Defining CDR
In this assessment, we adopt the definition of CDR used by the Intergovernmental Panel on
Climate Change (IPCC)38 (see Chapter 1 – Introduction, Section 1.3). We define CDR in thischapter, therefore, as:
Human activities capturing CO2 from the atmosphere and storing it durably in geological,
land or ocean reservoirs, or in products. This includes human enhancement of natural
removal processes, but excludes natural uptake not caused directly by human activities.
Not only does this definition rule out activities which capture fossil carbon, or which do notstore atmospheric carbon durably, it also has important implications for the measurement of
CDR generated through conventional CDR on land (see Chapter 1 – Introduction, Section
1.5 for definition) and other land management activities. Specifically, carbon removed andstored in the land reservoir can be a result of biomass growth on managed land, of direct
human intervention that enhances or creates new biomass (such as forest management orplanting trees), or of indirect climate effects (e.g. plant growth stimulation caused by elevatedatmospheric CO2, known as the CO2 fertilisation effect). According to the IPCC definition,
CO2 uptake not caused directly by human activities does not count as CDR, so an accurate
CDR deployment estimate should remove indirect climate effects from land data. For
example, the carbon impact of planting new trees should be counted, but the extra carbon
stored in those trees due to the CO2 fertilisation effect should not be.
*

Challenge 2: Finding sufficient data
Our estimate of current deployment of conventional CDR on land is based on an aggregatedand standardised National Greenhouse Gas Inventory (NGHGI) database developed by Grassi
et al. (2022)191. NGHGIs are reports submitted by countries to the United Nations Framework
Convention on Climate Change on an annual basis. They contain country-level estimates ofgreenhouse gas fluxes to and from the atmosphere from activities that occur in that country.
While globally comprehensive, these NGHGI estimates come with two complications thatmust be addressed. Firstly, NGHGI estimates of fluxes from managed land include emissions
as well as removals, meaning the gross volume of CDR is obscured. As an approximate
correction for this we removed all non-forest-management fluxes, for example the impactsof deforestation or peat fires. Secondly, NGHGI-managed land estimates include both direct
effects of human intervention and indirect effects of increased atmospheric CO2 (see above).
We estimate current CDR deployment with indirect effects removed by applying a correction
generated by the OSCAR model192. Because land-use storage fluctuates from year to year, wehave used the average managed land storage estimate for 2000-2020. For more information
on measuring land sink size, see Box 8.2 in Chapter 8 – The CDR gap.
Data availability regarding the deployment of novel CDR projects is currently very limited including for Bioenergy with Carbon Capture and Storage (BECCS), Direct Air Carbon Captureand Storage (DACCS), biochar, enhanced rock weathering and coastal wetland (blue carbon)
management. With no centralised repository of projects, information on deployment must
be drawn from fragmented data sources, including CDR sale records and contracts, carbon
offset registries, and NGO or corporate databases and reports. Here, we have systematicallycombined and cleaned 20 publicly available CDR databases and registries to develop acomprehensive view of present-day deployment of these CDR projects8,23,47,86,193–207.
* Following the approach of National Inventory reporting, for the purposes of this analysis, we consider (1) biomass growth on managed
land and (2) direct human intervention on managed land to be one and the same – in other words, we assume all biomass on managed
land is managed.

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Challenge 3: Developing an effective measurement approach
Developing an estimate of the net removal achieved through current deployment of CDR
is challenging from a reporting perspective. Firstly, most CDR projects do not report total
lifecycle emissions. Secondly, some CDR methods provide removal of CO2 over multiple
years, and approaches for reporting the carbon removed and stored by such methods
can overestimate their total impact (see Box 6.2). While the first issue is critical, it is not
one that is possible to solve here. We resolve the second by following a “stock-and-flow”
based accounting approach193. This measures CDR where and when it actually occurs bydifferentiating between two types of CDR activity: carbon sinks (carbon that is removed
from the atmosphere and stored in a non-atmospheric reservoir in a given year) and carbon
transfers (carbon that is moved between one non-atmospheric reservoir and another in agiven year).

Box 6.2 Avoiding overestimation in Carbon Dioxide
Removal deployment estimates
The climate impact of Carbon Dioxide Removal (CDR) activity is determined by removals
out of – and any emissions into – the atmosphere over the whole lifecycle of the CDR
method. This considers not only the carbon captured but also other factors, such as
emissions associated with the construction of facilities, energy use and other inputs, andthe fate of the stored carbon over time. Removals and emissions take place over different
time periods for different CDR methods, as they involve different sequences of transfers
through carbon pools (sometimes extended over multiple years), different inputs during
the process (in terms of fuels and materials) and different final storage pools with differing
durability of storage.
For this reason, there are two problems when estimating removals resulting from presentday CDR deployment. Firstly, the quantity of CDR reported by most projects is the grossquantity transferred from the atmosphere to the final carbon pool, excluding production
emissions and any re-release of previously stored carbon. As such, any estimate of climate
impact using reported data will be an overestimate of the actual net volume of CO₂ being
removed from the atmosphere on an annual basis.
Secondly, when a CDR method involves conversion of atmospheric carbon into otherforms, there may be a separation between when the CDR activity is recorded as occurring,and the actual timing of removal from the atmosphere. For example, in cases such as
Bioenergy with Carbon Capture and Storage (BECCS) or the production of durable
harvested wood products (HWP), the CDR activity tends to be reported in the year of
biomass conversion to an energy product or wood product, rather than the time thecarbon was transferred from atmosphere to plant (Figure 6.1). These will be one and thesame for BECCS when using annual crops, but not forest biomass and other perennial
crops. As such, these volumes run the risk of being double-counted if CDR methods makeuse of biomass that has also been recorded as a sink in prior years.

67The State of Carbon Dioxide Removal

Carbonsink

120

Carbontransfer

CarbonstorageTonnes of CO2

100

80

60

40

20

Harvestedwood products0

Biomass
0

20

40
60
Number of years

80

100

Figure 6.1. An illustrative carbon dioxide (CO2) removal and storage pathway for the production of harvested
wood products (HWPs). During the carbon sink phase, carbon is removed and stored incrementally bybiomass growth in forests208. During the carbon transfer phase, a portion of stored carbon is transferred fromforest biomass to HWPs, with the remainder deposited as deadwood209. During the storage phase, both the
deadwood and HWP decay to the atmosphere, though at different rates210.

While it is not currently possible to resolve the lifetime emissions reporting issue here, it ispossible to resolve the issue of double-counting by multi-year CDR processes. We do this byadopting a stock-and-flow reporting system193, which splits CDR into two complementary
but separate activities mapped onto the various pools of the global carbon cycle:•

The first activity is termed “carbon sinks” and is defined as activities which remove
carbon from the atmosphere and durably store it in a non-atmospheric pool in thesame year.

•

The second activity is termed “carbon transfers” and is defined as activities whichtransfer carbon from one non-atmospheric pool to another in the same year.

In so doing, carbon removed from the atmosphere is always recorded as a carbon sink in
the year in which it actually occurs, and activities such as the production of durable HWPs
are recorded separately as carbon transfers in the year they are produced, a sum which
is useful for tracking changes in carbon storage but which is reported separately fromcarbon sinks to avoid double-counting.
According to our estimates of current CDR deployment, all identified BECCS and biochar
projects use annual crops or forest residues as inputs. For both of these carbon sources,
the carbon sink and transfer are considered to occur in the same year. While forest
residues have, technically, grown over many years before deposition, they are commonly
assumed to behave the same way as annual crops because, like annual crops, the amountof deposition and decay in a given year is about equal, so they are neither a net source nora sink of carbon. Hence, the only current CDR method with carbon removal and carbon
transfers occurring in separate years is the production of durable HWPs.

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The State of Carbon Dioxide Removal

6.2 Current CDR deployment
Virtually all current CDR comes from conventional methods on managed land. Only a tiny
fraction results from novel CDR methods including BECCS, biochar, DACCS, enhanced rockweathering and coastal wetland (blue carbon) management.

Global managed forest sink estimates

0
-1000

Net managed forest ﬂux
less indirect eﬀect

Global managed forest sink (MtCO2/yr)

-2000
-3000
-4000
-5000
-6000

Net managed forest ﬂux

-7000
-8000
-9000

-10,000
2000

2005

2010

2015

2020

Figure 6.2. Estimates of Carbon Dioxide Removal (CDR) from managed land during 2000-2020. Storage from net
managed forest flux, including indirect climate effects, based on National Greenhouse Gas Inventory data (green).
Storage from net managed forest flux, minus indirect climate effects (orange). Shaded regions indicate the range ofmeasurement uncertainty.

We estimate society is currently generating roughly 2,000 MtCO2 per year of gross CDR(carbon that is removed from the atmosphere and stored in a durable non-atmospheric pool).
Of this total, almost all comes from managed land.
NGHGI data indicates total global removals from managed forest land of around 6,400 ±
2,800 MtCO2 per year, averaged over 2000-2020. Removing indirect climate effects, wearrive at an estimate of 2,000 ± 900 MtCO2 per year for conventional CDR on land (Figure6.2). This is smaller than a comparable estimate derived from bookkeeping models, whichputs direct forest removals at 3,300 ± 1,100 MtCO2 per year. The difference is likely due toinclusion of shifting cultivation (cutting forest for agriculture, then abandoning), which leads
to large emissions and removals within each year. We exclude this activity from our estimate.
The remaining 2.3 MtCO2 of gross carbon sinks comes from novel CDR methods. The
breakdown for different CDR methods is as follows: 1.82 MtCO2 from BECCS, 0.5 MtCO2
from biochar production and 0.01 MtCO2 the combined result of all other methods, including
DACCS, enhanced rock weathering, coastal wetland (blue carbon) management and others(Figure 6.3).

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The State of Carbon Dioxide Removal

BECCS

Biochar

Other Novel CDR

Novel CDR
0

0.5

1.0
1.5
Million tons of CO2 removed

2.0

2.5

Conventional CDR
methods on land
0

200

400

600

800

1000

1200

1400

1600

1800

2000

Million tons of CO2 removed

Figure 6.3. Estimate of current Carbon Dioxide Removal (CDR) deployment. Definition: Bioenergy with Carbon
Capture and Storage (BECCS).

Furthermore, we estimate the volume of carbon transfers currently generated each year isabout 223 MtCO2. All 223 Mt are generated through the production of durable harvested
wood products (HWPs), specifically sawnwood and wood panels, which transfer carbon fromforest stock into durable wood products (Figure 6.4).

6.3 Future CDR deployment
There are a number of CDR projects in development that will become operational over thecourse of this decade, the pace of which can be used to estimate future growth.
It is possible to forecast CDR deployment, assuming no new projects are started and all
in-development projects are completed. Under this assumption, atmospheric removals
generated using non-land-management CDR projects will grow from 2.3 MtCO2 per year
in 2022 to 11.75 MtCO2 per year by 2025, driven almost entirely by the completion of
the Summit Carbon Solutions BECCS project, which involves bringing online 30 coupledethanol-production BECCS plants and associated geological storage. By 2025, the annual
volume of atmospheric removals using methods other than BECCS, DACCS and biochar willremain well below 1 MtCO2 per year in volume.
Another way to project future CDR deployment is to extrapolate current deployment data.
This approach is informative as it is unrealistic to assume there will be no additional CDR
project development beyond 2025. To provide an approximate range of what might be
expected, we fit both linear and exponential trends to the 2020-2025 deployment data
for each CDR method as plausible upper and lower bounds. Under these assumptions, by
2030 we could see 30.5-208.5 MtCO2 per year of BECCS deployment, 7-297.5 MtCO2
per year of DACCS deployment, 1.8-65 MtCO2 per year of biochar deployment and 0.0360.061 MtCO2 per year from all other methods (see Figure 6.4). Based on a longer available
historical dataset and knowledge of the demand dynamics behind HWPs, we expect HWPs
will at most continue to exhibit linear growth moving forward. While the exponential
extrapolations used for novel CDR projects may seem large, it is important to note that
despite persistently linear forecasts, solar and wind energy deployment have exhibited
exponential trends over the past decade211, and similar dynamics for CDR methods cannot

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The State of Carbon Dioxide Removal
be ruled out. For this to occur, however, substantial acceleration in innovation pace andscope would need to take place (see Chapter 3 – Innovation).

BECCS deployment

MtCO2/yr

102

A

DACCS deployment
102

B

All other deployment

C

102

102

101

101

101

101

100

100

100

100

10-1

10-1

10-1

10-1

10-2

10-2

10-2

10-2

2020

2025

2030

2020

Harvested wood products
260

E

240

2025

104

2020

2025

2030

2020

2025

2030

F

103

200

2030

D

Cumulative stored carbon (MtCO2 )220
MtCO2/yr

Biochar deployment

Deployed CDR (lithosphere)
With linear growth in deployment
With exponential growth in deployment
Deployed CDR (biochar)With linear growth in deployment
With exponential growth in deployment

102

180
160

101

140

2000

2010

2020

2030

100
2022

2023

2024

2025

2026

2027

2028

2029

2030

Figure 6.4. (A-D) Deployment of various methods for generating carbon sinks, measured in MtCO2 per year. Grey
projections indicate a lower (linear) and upper (exponential) extrapolation of 2020-2025 deployment data. The
grey crosses indicate 2030 deployment if only currently in-development projects are completed. (E) Harvested
wood product production, measured in MtCO2 per year, with a linear projection to 2030, with 9-95% uncertainty
in grey. (F) Cumulative stored carbon by storage reservoir/pool, given observed deployment, continued linear
deployment and continued exponential deployment, measured in MtCO2. Definitions: Bioenergy with Carbon
Capture and Storage (BECCS); Carbon Dioxide Removal (CDR); Direct Air Carbon Capture and Storage (DACCS).

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The State of Carbon Dioxide Removal

6.4 Looking ahead
Improving estimates of CDR deployment requires issues around measurement, data andreporting to be resolved.
Developing an accurate estimate of CDR deployment is necessary if we want to achieve thegoals of the Paris Agreement, as without an accurate deployment baseline it is challenging
to determine if we are generating sufficient volumes of CDR (see Chapter 8 – The CDR
gap). There are three main barriers that need to be overcome to ensure we can maintain an
accurate CDR deployment estimate going forward. Firstly, agreement will need to be reachedon how to accurately measure CDR from conventional CDR methods on land and CDR
achieved through other managed land based activities. Second, a central repository for CDR
project data will need to be built. Thirdly, CDR project reporting will need to be standardised(see Chapter 9 – Future assessments).

72

“Every year of delaying rapid andsustained emission reductions
increases the requirements
for CDR deployment in the longterm.”

The State of Carbon Dioxide Removal

Chapter 7 | Scenarios
Chapter team: Matthew J Giddeni, Jan C Minxii,iv, Thomas Gasseri, William F Lambii,iv, Yoga Pratamai, Jessica Strefleriii,
Keywan Riahii
i International Institute for Applied Systems Analysis (IIASA)
ii Mercator Research Institute on Global Commons and Climate Change (MCC)iii Potsdam Institute for Climate Impact Research (PIK)iv University of Leeds

Carbon Dioxide Removal (CDR) increases in all pathways that limit global temperature
to 1.5°C and 2°C. How much we rely on CDR in the second half of the century depends
critically on how quickly we reduce emissions in the first half.

Box 7.1 Key findings•

The cumulative amount of Carbon Dioxide Removal (CDR) deployed between 2020
and 2100 varies substantially across pathways that likely limit global temperature rise
to 2°C or lower, ranging from 450 to 1,100 GtCO2.

•

All scenarios that likely limit warming to 2°C or lower involve substantial emission
reductions prior to any significant scale-up of CDR. During the second half of the 21st
century, CDR becomes increasingly important. However, near-term scale-up of CDR is
critical to achieve required deployment in the long term.

•

CDR is scaled up more quickly in scenarios that limit warming to 1.5°C with no or
limited overshoot than in scenarios that likely limit warming to 2°C, but the latter often
involve higher long-term annual CDR. Over the course of the century, both sets of
scenarios see similar total CDR deployment.

•

Scenarios that limit warming to 1.5°C with no or limited overshoot reduce annual net
CO2 emissions by 19 (14-27) GtCO2 in 2030 relative to 2020. Annual CDR increases
by 2.6 (0.8-5.4) GtCO2 over the same time period and by 9.5 (5.5-16.0) GtCO2 per year
at the point of net-zero CO2 emissions.

•

Conventional CDR on land is responsible for 99% (78-100%) of CDR in 2030 in both
1.5°C and 2°C pathways. Conventional CDR levels continue to grow thereafter –peaking around 2050, approximately doubling in 1.5°C pathways and increasing byaround 50% in 2°C pathways compared to 2020 levels. Novel CDR methods typicallyincrease throughout the century.

•

Almost all scenarios that limit warming to 1.5°C by 2100 involve some level of
temporary temperature overshoot. On average, in “high overshoot” pathways thatexceed 1.5°C by more than ~0.1°C before returning to it by the end of the century,
about 14% more CDR is used cumulatively than in scenarios with no or limited
overshoot.

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The State of Carbon Dioxide Removal•

Net-negative CO2 emissions occur when annual levels of CDR exceed annual levelsof gross positive CO2 emissions and are a feature of almost all scenarios likely to limit
warming to 2°C or lower.

•

Almost all assessed scenarios (502 of 507) contain Bioenergy with Carbon Capture andStorage. A majority of scenarios also include conventional CDR on land (407 of 507).

•

Limiting our dependence on CDR in the long term requires faster emissions reductionsin the near term by increasing shares of renewable energy, enhancing energy
efficiency, reducing energy demand and limiting or eliminating fossil fuel-based
processes.

7.1 Mapping alternative future pathways
Integrated assessment models provide possible pathways to achieve the Paris temperaturegoal.
To understand the role of Carbon Dioxide Removal (CDR) in meeting the Paris temperature
goal, it is critical to take a long-term perspective. Given that the future could unfold in very
different ways, we evaluate alternative mitigation scenarios† that limit global temperaturerise to “well below 2°C” (see Chapter 1 – Introduction, Box 1.1). Integrated assessment
models are a widely used tool to systematically map out these alternative pathways and thetechnological, economic and political choices that need to be made in the coming decades tokeep the Paris temperature goal within reach (see Box 7.2).
The Paris Agreement contains a long-term temperature goal and a mitigation goal, which it
defines in Articles 2 and 4, respectively, as:“Holding the increase in the global average temperature to well below 2°C above
pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C
above pre-industrial levels” (Article 2) by “achiev[ing] a balance between anthropogenic
emissions by sources and removals by sinks of greenhouse gases in the second half of
this century” (Article 4)212.
Aligning scenario temperature outcomes with global climate goals combines inherently
scientific and political processes. It has become increasingly common in the scientificcommunity to distinguish three classes of scenario relevant to the recent history of climate
policy – categorised as C1, C2 and C3 by the Intergovernmental Panel on Climate Change(IPCC) (see Table 7.1). There are different opinions regarding the extent to which scenarios
in different categories assessed in the recent IPCC Working Group III report reflect theincreased long-term ambition of the Paris Agreement to limit warming to “well below”
2°C213,214 relative to previous climate agreements to keep warming “below” 2°C215. In thisreport, we include in our analysis all three groups – scenarios that are “as likely as not”
to keep warming below 1.5°C throughout the century (C1), scenarios that have a “highovershoot” of 1.5°C (C2), and scenarios likely to keep warming below 2°C (C3) – as relevant
to, but not necessarily all consistent with, the Paris Agreement. Throughout this report, werefer to C1 scenarios as 1.5°C scenarios and C3 scenarios as 2°C scenarios.
† In this report, we use the terms ‘scenarios’ and ‘pathways’ interchangeably. In both cases, we refer to outcomes from scenarios as assessed by the IPCC.

75

The State of Carbon Dioxide Removal
Table 7.1. Scenario definitions likely to keep global temperature increase to 2°C or lower

Warming IPCC
Description Quantification
limit
category
label

Peak
warming
level(°C, 50%
probability)

Warming
level in
2100(°C, 50%
probability)

No. ofscenarios

1.5°C

1.3 (1.1-1.5)

97

1.4 (1.2-1.5)

133

1.6 (1.5-1.8)

311

C1

Below 1.5°C<1.5°C peak warming

1.6

with nowith ≥33% chance(1.4-1.6)

or limitedand <1.5°C end-of-overshootcentury warmingwith >50% chance.
Temperature
overshoot limited to<0.1°C.

C2

Below 1.5°C<1.5°C peak warming

1.7

with highwith ≥33% chance(1.5-1.8)

overshootand <1.5°C end-ofcentury warming with>50% chance. No
limit on temperature
overshoot.

2°C

C3

Likely below<2°C peak warming

1.7

2°C

with >67% chance.

(1.6-1.8)

Box 7.2 Methods: Climate policy scenarios from
integrated assessment models
Integrated assessment models (IAMs) are complex models which connect representationsof the global economy, energy and land-use systems. These interconnected systems are
represented as a mix of different technologies, processes and practices that are deployed
to meet the demand for energy and other services within a given set of policy targets
or constraints. Such technologies include fossil fuel installations, renewable energy
technologies, agricultural production practices and CDR methods, as well as end-use
technologies such as road vehicles and appliances.
IAM scenarios depend on a set of key assumptions²¹⁶ – such as population growth, levelof urbanisation and potential for technological progress – to evaluate the evolution oftechnologies and consumption patterns in alternative futures. Modelling teams combine
these widely used assumptions with their own estimations and quantifications of thepotential for technological change, as well as future availability and cost improvements oftechnologies, and then apply key policy constraints (such as a global temperature limit) toarrive at a pathway or scenario.

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The State of Carbon Dioxide Removal

Many IAMs use a “cost-effective” approach²¹⁷ to estimate economic and energy
transitions, in that they try to reach a given climate goal at minimal costs for the global
economy. How future costs are valued relative to today (i.e. the assumed discount rate) is
a normative assumption required for this approach that can affect key outcomes such as
total CO2 emissions until net zero²¹⁸. Most scenarios assume idealised conditions where
currently nascent mitigation technologies become available in the next decade or so, while
stringent global climate action starts immediately. However, IAMs are also used to study
scenarios in which climate policy and the low-carbon transition are delayed or in which
not all technologies are (fully) available²¹⁹. As such, IAMs are a key resource to explore theconstraints or possibilities that shape how we meet climate goals, including the key rolesof CDR methods in doing so.
We use the collection of scenarios compiled for the Intergovernmental Panel on Climate
Change’s Sixth Assessment Report (IPCC AR6) as a starting point here²²⁰. The databasefeatures 1,202 scenarios with climate assessments from 14 modelling teams²²¹. Whilescenarios provide standard data on novel CDR (mainly BECCS), conventional CDR on land
was only partially assessed in AR6 because different models used different data reporting
methodologies and approaches. Using the reduced-complexity climate model OSCAR²²²,
we develop reanalysed estimations of conventional carbon removal on land – such as
via afforestation/reforestation – following definitions of national emissions inventory
submissions to the United Nations Framework Convention on Climate Change¹⁹². We
exclude “indirect” carbon removals from environmental changes on managed land (such as
CO₂ fertilisation) from these estimates, in line with the definition of anthropogenic CDR
utilised by the IPCC, as well as in Chapter 1, and the estimates of current CDR deployment
in Chapter 6.

7.2 Scenarios that limit warming to 1.5°C and 2°C
All scenarios that limit global temperature rise to 1.5°C or 2°C feature substantial increases in
CDR in addition to sustained and deep emission reductions. Failing to deliver these emission
reductions in the short term increases scale and dependence on CDR in the long term.
All emissions pathways that limit global warming to 2°C or lower feature multiple gigatonnesof CDR annually (see Figure 7.2), making CDR a critical component of any mitigation strategy
relevant to the Paris Agreement. In assessed scenarios, CDR does not play this role in thenear term, however, as absolute emission reductions dominate mitigation activities during
the first half of the 21st century. For example, by 2030 net CO2 annual emissions decline by
19 (14-27) GtCO2 and 8 (0-17) GtCO2 relative to 2020 levels in 1.5°C and 2°C pathways,
respectively. During that same timeframe, annual deployment of conventional CDR on land
– such as via afforestation/reforestation – increases by 0.8 (-0.1 to 3.0) GtCO2, while novel
CDR – such as via Bioenergy with Carbon Capture and Storage (BECCS) or Direct Air Carbon
Capture and Storage (DACCS) – increases by 0.01 (0-0.83) GtCO2. CDR levels expand fasterin 1.5°C pathways than 2°C pathways, growing by 2.6 (0.8-5.4) GtCO2 removals annually by2030 compared with 2020 levels. Both CDR types reach their maximum deployment only
after mid-century (see Chapter 1 – Introduction for our definitions of “conventional” and“novel”). Conventional CDR on land is responsible for 99% (78-100%) of 2030 CDR in both
1.5°C and 2°C pathways. Conventional CDR on land continues to grow thereafter until its
peak around 2050, approximately doubling in 1.5°C pathways and increasing by around 50%

77

The State of Carbon Dioxide Removal
in 2°C pathways compared with 2020 levels. Novel CDR methods such as BECCS or DACCS
are typically scaled up throughout the century.
1.5°C scenarios achieve net-zero CO2 emissions by around mid-century, and the vast majority(93%) of 2°C scenarios do so on average about two decades later. CDR grows steadily inthese deep mitigation pathways. At the time of net-zero CO2, CDR levels range between
5.5 and 16 GtCO2 per year in 1.5°C pathways and between 6.8 and 16 GtCO2 per year
in 2°C pathways. During the second half of the century, after the point of net-zero CO2emissions, CDR becomes an increasingly dominant feature of climate change mitigation
efforts. All 1.5°C and most 2°C pathways feature a sustained period of net-negative CO2
emissions from enhanced levels of CDR that reduces atmospheric carbon concentrations and(often) leads to a drawdown in global mean temperatures. Almost all pathways achieve netzero or net-negative CO2 emissions through utilisation of CDR, and many achieve net-zerogreenhouse gases (GHGs) in the long term. However, as Chapter 3 (Innovation) illustrates,
new technologies can take decades to mature and reach large-scale adoption. Steady nearterm progress in deploying novel CDR – such as BECCS and DACCS – is critical to achieving
the required scale-up in the long term.
The level and composition of CDR deployed in scenarios varies widely and depends on a numberof factors within a given scenario, as discussed in Section 7.3. Table 7.2 shows cumulative
CDR deployment across the 21st century, where values for 2°C pathways range between
440 GtCO2 and 1,100 GtCO2, with a median value of 630 GtCO2. More ambitious scenariosthat limit warming to 1.5°C with no or limited overshoot show very similar levels of CDR
deployment, reaching a median value of 740 GtCO2 with a range of 420-1,100 GtCO2. To still
limit warming to 1.5°C in 2100 but with a high temporary overshoot of temperatures (>0.1°C),
the range of required cumulative CDR increases by about 110 GtCO2 on average. This is about
14% higher than in limited-overshoot 1.5°C scenarios. The additional CDR is needed to draw
down temperature levels after peaking223. As a result, every year of delaying rapid and sustained
emission reductions increases the requirements for CDR deployment in the long term4,37,224.
Scenarios to date have focused on a narrow set of CDR methods, principally afforestation/
reforestation and BECCS. This requires great care in the interpretation of the scale of CDR
methods in climate change mitigation as well as the role of individual CDR methods. In thisreport, we interpret BECCS deployments as being representative of a broader set of novel
CDR methods and afforestation/reforestation as being representative of conventional CDR
on land. Modelling teams have recently begun to incorporate other novel CDR methods,
such as DACCS or enhanced rock weathering, into their modelling frameworks225. As teams
expand their representation of CDR methods, trade-offs across the CDR portfolio havebecome more apparent.
Table 7.2 highlights the variability in the composition of CDR portfolios in existing
scenarios.BECCS is present in almost all scenarios considered (502 of 507), and deployment
levels vary widely, spanning 170-760 GtCO₂ cumulatively throughout the century.
Conventional CDR on land is also included in a majority of scenarios (407 of 507) and has aslightly smaller span of cumulative removals (130-560 Gt CO2).
In contrast, fewer than 1% of considered pathways include active contributions fromenhanced rock weathering. A range of studies have reported that including other CDR
methods in addition to BECCS might reduce not only the range of mitigation costs but also
the impact of CDR on energy use, emissions, land and water. However, contributions of thesemethods to CDR are sensitive to the rate at which they can be scaled up, which remains
highly uncertain (Box 7.3).

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The State of Carbon Dioxide Removal
A

1.5°C with no or limited overshoot

Min/max range

1.5C after a high overshoot
2°C pathways

CO2 emissions (GtCO2yr)

40

Emission reductions Mitigation activity
dominate dominated by
mitigation sustained CDR

30

20

10

0

-10

-20

2020

B

2040

2060

2080

Conventional CDR on land
25

2100

Novel CDR

1.5°C with no or limited overshoot
1.5C after a high overshoot
2°C pathways

CO2 removals (GtCO2yr)

20

Min/max range

15
10
5
0
-5
2020

2040

2060

2080

2100

2020

2040

2060

2080

2100

Figure 7.1. (A) Global net carbon dioxide (CO2) emissions in scenarios assessed in the Intergovernmental Panelon Climate Change Sixth Assessment Report and (B) upscaling of Carbon Dioxide Removal (CDR) methods under
different pathway categories, as described in Table 7.1. Shaded regions show the 5-95th percentile ranges.

79

The State of Carbon Dioxide Removal
Table 7.2. Cumulative Carbon Dioxide Removal (CDR) from 2020 to 2100 in GtCO2 in assessed pathways, highlighting the median and 5-95% range of values. “Number ofscenarios” indicates the total number of scenarios evaluated by a range of models that include the CDR method as a variable. Statistical total CDR values presented here do notequal the sum of their components, as values are calculated on a per-scenario basis. Definitions: Bioenergy with Carbon Capture and Storage (BECCS); Direct Air Carbon Captureand Storage (DACCS).

CDR method

Total (all CDR options)*

Below 1.5°C with no or
limited overshoot (C1)
Total CDR Number ofscenarios

Below 1.5°C with highovershoot (C2)
Total CDR Number ofscenarios

Likely below 2°C (C3)

Total (all pathways)

Total CDR

Number of
scenarios

Total CDR

Number of
scenarios

740

850

630 (440-231

700 (450-407

70(420-1100)
Conventional CDR on land*

370(590-1,300)
70(170-560)
Novel CDR

400
330

91

30

91

0
(0-47)

310 (110-560)

1,100)
231

500

122

460

31

110
0

390

294

(160-660)
122

407

290

24

19

289

1

0
(0-0)

330

91

29

502
146

(0-340)10(0-0)* Total number of scenarios is lower than for novel CDR because data required for the estimation of conventional CDR on land is not available for all scenarios.

80

507

(170-760)(0-250)(0-0)

400(110-790)(170-650)(0-540)2360(130-560)(230-840)(0-310)Enhanced rock weathering

106(130-860)(32-780)
DACCS

360

1,100)(160-520)(24-860)
BECCS

106

4

The State of Carbon Dioxide Removal

Box 7.3 Carbon Dioxide Removal methods inmitigation scenarios
Historically, mitigation scenarios have focused on a limited set of Carbon Dioxide Removal(CDR) methods, mostly implementing representations of Bioenergy with Carbon Captureand Storage and afforestation/reforestation. However, a portfolio of CDR methods will
most likely be deployed to achieve global and national climate targets. The compositionof the portfolio will depend on available resources, technologies and preferences, and willchange over time. Inclusion of additional CDR methods in models tends to increase thetotal CDR deployment in scenarios43. As more CDR methods are added to the portfolio,
however, a given amount of CDR can be reached with reduced deployment of individual
CDR methods, thus also limiting negative side-effects43.
As some methods show a strong regional concentration – for example, the potential forafforestation/reforestation and for enhanced rock weathering is highest in the tropics– the availability of a CDR portfolio also changes the regional distribution of CDR. This
becomes more balanced with the introduction of more CDR options.
The development of a CDR portfolio therefore hedges not only against technologicalrisks but also against institutional risks (by balancing regional deployment) and against
ecological risks (by limiting the deployment of single methods).

7.3 The role of CDR in scenarios that limit
warming to 1.5°C and 2°C
The amount of CDR differs widely across scenarios that limit warming to 1.5°C and 2°C,
depending on when and how we choose to transform the global economy towards net-zero
CO2 and GHG emissions.
The previous section highlighted that 1.5°C scenarios differ considerably from 2°C scenarios,
featuring much faster emissions reductions to net-zero CO2 emissions and a more rapid CDR
scale-up. At the same time, total cumulative CDR across the 21st century is very similar, but
within each class of scenarios there is a wide range in deployments – from a few hundred
gigatonnes to over a thousand – through the course of the century. This range is a reflectionof the different mitigation choices available and their direct implications for the level andtiming of CDR deployments.
The scale of CDR deployments in 1.5°C and 2°C pathways depends crucially on politicalresponses to climate change, alongside social and economic developments in the coming
decades. Key factors that shape CDR deployment in scenarios are (1) the stringency of thetemperature limit achieved; (2) the magnitude and duration of any temperature overshootand eventual drawdown; (3) the speed and depth of near-term emission reductions; (4) theavailability of measures to reduce energy demand; (5) the breadth of the portfolio of available
CDR methods as well as other mitigation options.
Individually, these key factors shape the level of CDR deployments in scenarios by shaping

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The State of Carbon Dioxide Removal
the risk of carbon budget exceedance (e.g. stringency, delay, demand reduction), as wellas the size of the residual emissions that need to be compensated at net-zero CO2 andnet-zero GHGs (e.g. fossil fuel dependence, demand reduction, technological availability).
Delay of GHG emission reductions tends to increase CDR requirements in scenarios that
achieve a given temperature outcome, while energy demand reductions decreases it. Moretechnological flexibility (for example, increased usage of CCS in industrial processes likecement production) limits CDR requirements by lowering residual emissions, while availabilityof more CDR options can lead to increased overall deployment by providing potentiallycheaper alternatives to some of the more expensive emission reduction options. Scenario
evidence indicates that more CDR is utilised after having initially exceeded a specific warming
level in order to draw net emissions and temperatures down at a faster pace later in the
century, such as in 1.5°C high overshoot scenarios compared with 1.5°C scenarios with no or
low overshoot.
Three focus scenarios
To show how different approaches to climate change mitigation are related to different levels
and types of CDR, we analyse three “Focus Pathways” (Figure 7.2). These three pathways
highlight strategies that focus on emission reductions mainly through demand reduction,
renewable energy or carbon removal while limiting warming to 1.5°C.
The Focus on Demand Reduction scenario displays how rapid near-term emission reductions
facilitated by radical energy efficiency improvements and lower energy demand levels canlimit dependence on CDR substantially, with a maximum yearly removal rate of 4.8 GtCO2 in
2050. Cumulative removals across the 21st century (2020-2100) of 330 GtCO2 are provided
exclusively from conventional CDR on land, showcasing that novel CDR is not strictly
necessary to meet the Paris temperature goal. However, this is one of the few assessed
scenarios that limits the cumulative CDR deployments necessary through aggressive nearterm mitigation. The Focus on Demand Reduction scenario results in an end-of-century net
emissions level of around 0.8 GtCO2e, with residual non-CO2 emissions mostly balanced by
net-negative emissions from land use, land-use change and forestry.
The Focus on Renewables scenario involves fast and deep emission reductions facilitated bya rapid expansion of renewables. In this case, cumulative carbon removals are 500 GtCO2
between 2020 and 2100, with a maximum annual rate of 8.2 GtCO2 in 2055. CDR in Focus
on Renewables is provided through a combination of conventional CDR on land and novel
CDR, notably BECCS. If CCS facilities can be scaled in time, the geological storage of CO2
this affords is more durable and less reversible than storage in trees and soils via conventional
CDR on land. The Focus on Renewables scenario achieves net-zero GHG emissions by around2090, and net-negative GHG emissions persist thereafter.
Finally, in the Focus on Carbon Removal scenario, GHG emissions reductions occur rapidly inthe first half of the century and eventually reach net-zero levels by around 2070. Emissions
remain to a large extent in the transportation, residential and commercial, and industry
sectors, and are balanced at net zero by larger levels of novel CDR methods as well as netnegative CO2 emissions from land use, land-use change and forestry. Significantly more CDR
is deployed throughout the century due in strong part to balancing remaining residual nonCO2 emissions in, for example, the agricultural sector. Cumulative removals from 2020 to2100 arrive at 690 GtCO2 and reach a maximum level of 10 GtCO2 per year in 2050. Thislevel is maintained thereafter, of which 75% is from conventional CDR on land at the end of
the century.

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While there are many scenarios – particularly those with high temperature overshoot– thatinvolve CDR deployments far beyond what is represented in these three Focal Pathways, it ishighly questionable whether such levels of CDR can be developed in a sustainable manner,which introduces strong trade-offs with other Sustainable Development Goals.

A

Focus on demand reduction

Focus on renewables

Focus on carbon removal

Annual GHG emissions (GtCO2yr)

60
50
40
30
20
10
0
-10
-20
2020

2060

2100

2020

Positive emissions: Non-CO2 GHG

Positive emissions: Non-AFOLU CO2

B

2020

At time of net-zero CO2

2060

2100

2020

Net emissions: AFOLU CO2

2060

2100

Net GHG emissions

Negative emissions: Novel CDR

Net CO2 emissions

At time of net-zero GHG

60
Uncertainty range

Annual CO2 emissions (GtCO2yr)

50

Non-CO2
Transportation

40

Residential and Commercial
Industry

30

20

10

Other sector

Focus ondemandreduction(2059)

Focus onrenewables(2068)

Focus oncarbonremoval(2048)AFOLU-CO2
Focus ondemandreduction*(2100)

Focus onrenewables(2091)

Focus oncarbonremoval(2077)

Energy supply
Novel CDR
* Pathway does not reachnet-zero by 2100

0-10Figure 7.2. (A) Emissions trajectories across Focus Pathways and (B) sectoral contributions to carbon dioxide (CO2)emissions and removals at the time of net zero CO2 and net zero greenhouse gases. Definitions: agriculture, forestry
and other land use (AFOLU); Carbon Dioxide Removal (CDR); greenhouse gas (GHG).

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The State of Carbon Dioxide Removal

7.4 Limiting future reliance on CDRGiven uncertainties about scaling up CDR, our dependence on it can be limited by reducing
emissions fast and using energy more efficiently.
Scenarios produced by the scientific community provide a wide set of possible pathways tomeet global climate targets. As such, they provide general guidance on different approaches
that can be used to limit global temperature rise, including near eliminating dependence
on fossil fuels, electrifying most sectors of the economy, halting deforestation, as well asactively developing and deploying conventional CDR on land and novel CDR. Whether new
technologies represented in models will become available at the scale assumed by different
scenarios is highly uncertain, however.
The processes and technologies necessary to enable limiting warming to 1.5°C are alreadypresently available – namely, shifting towards higher shares of renewable electricity andelectrifying energy processes more broadly while beginning to use energy more efficiently.
Current estimates of emissions from existing fossil-based extraction and infrastructure
already risk exceeding the Paris Agreement long-term temperature goal, highlighting theimportance of transitioning away from these energy sources²⁴⁵,²⁴⁶,²⁴⁷. Simultaneously, novel
CDR methods represented in pathways are either nascent, not currently deployed at scale, or
still conceptual in nature. Thus, while most scenarios show that a non-trivial amount of novel
CDR will be needed eventually, the degree to which different CDR methods will be able tosustainably achieve scale-up is highly uncertain. The most prudent approach is therefore tolimit future reliance on novel CDR by actively reducing emissions with current technologies
and enhancing regional cooperation to support countries outside of the Organisation for
Economic Co-operation and Development to avoid carbon lock-in.
Caution should be taken when trying to use scenarios to directly measure CDR needs against
emissions inventories reported by countries to the United Nations Framework Convention
on Climate Change. Modelled scenarios consider human-induced (or “direct”) emissions andreductions; countries, in their National Greenhouse Gas Inventories (NGHGIs) also consider
natural areas when accounting for their total present-day emissions (see Chapter 8 – The
CDR gap, Section 8.2). When accounting for the additional forested area considered bycountries in the NGHGIs, present-day global CO2 emissions are around 5.5 Gt lower thancalculated by scientific studies such as the Global Carbon Budget. Further, the efficacy of thisadditional forested area in continuing to remove carbon will change over time depending on
the future evolution of global mitigation. Better aligning these values and definitions between
scientists and the policymaking community is an area of active development.

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“There is a significant gap
between proposed CDR levels
and those in scenarios that limit
warming to 2°C or lower.”

The State of Carbon Dioxide Removal

Chapter 8 | The CDR gap
William F Lambi,ii, Thomas Gasseriii, Giacomo Grassiiv, Matthew Giddeniii, Carter Powisv, Oliver Gedenvi, Jan C Minxi,ii, Gregory Nemetvii, Yoga
Pratamaiii, Keywan Riahiiii, Stephen M Smithv, Jan Steinhauseriii
Mercator Research Institute on Global Commons and Climate Change (MCC)
University of Leeds
iii
International Institute for Applied Systems Analysis (IIASA)
iv
Joint Research Centre, European Commissionv
University of Oxford
vi
German Institute for International and Security Affairs (SWP)
vii
University of Wisconsin-Madisoniii

We are not on track to meet the Paris temperature goal, in terms of either current or
proposed Carbon Dioxide Removal (CDR). Closing the gap means expanding conventional
CDR on land and rapidly scaling up novel CDR at the same time as urgently cutting emissions.

Box 8.1 Key findings•

In 2030, global scenarios that limit warming to 2°C or lower indicate additional
Carbon Dioxide Removal (CDR) of 0.96 (0 to 3.4) GtCO₂ per year, compared with
2020. By contrast, countries have pledged an additional 0.1 to 0.65 GtCO₂ by 2030
in their Nationally Determined Contributions (NDCs) – a range that corresponds tounconditional and conditional NDCs. This suggests there is already an emerging CDR
gap by 2030.

•

In 2050, global scenarios that limit warming to 2°C or lower indicate additional CDR
of 4.8 (0.58 to 13) GtCO₂ per year, compared with 2020. However, countries have
only proposed an additional 1.5 to 2.3 GtCO₂ of CDR per year by 2050 in their longterm mitigation strategies. Only a minority of countries have provided transparent,
quantifiable scenarios for CDR in long-term mitigation strategies so far. This implies afar more substantive CDR gap in 2050.

•

This report distinguishes conventional CDR on land from novel CDR. The former
includes afforestation, reforestation and forest management; the latter includes
Bioenergy with Carbon Capture and Storage, Direct Air Carbon Capture and Storage,
biochar, enhanced rock weathering and coastal wetland (blue carbon) management.
Considering these separately is important to highlight the scale-up challenge.

•

Global scenarios that limit warming to 2°C or lower scale up conventional CDR on land
by a factor of 1.3 (0.95 to 2.2) by 2030 and factor of 2 (0.19 to 3.5) by 2050, comparedwith 2020.

•

Countries plan to maintain or slightly increase current conventional CDR on land
until 2030 according to their NDCs. This implies an increase by a factor of 1.1 to 1.3,
compared with 2020 (for unconditional and conditional pledges, respectively). Few
countries have submitted plans for scaling up conventional CDR on land by 2050, but
those that have imply an increase by a factor of 2.7 to 4.2, compared with 2020.

•

Global scenarios that limit warming to 2°C or lower involve scaling up novel CDR
by a factor of 30 (0 to 540) by 2030 and a factor of 1,300 (260 to 4,900) by 2050,
compared with 2020.

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The State of Carbon Dioxide Removal•

So far, no countries have pledged to scale novel CDR by 2030 in their NDCs. Longterm mitigation strategies suggest some novel CDR deployment by 2050, increasing
by a factor of about 300 compared with 2020.

•

The next decade is crucial for novel CDR. Failure to create momentum in thisformative phase will contribute to a widening gap by 2050 and beyond.

•Achieving the Paris temperature goal with only a small expansion of CDR is possible,
but moves further out of reach every year in which greenhouse gas emissions do not
fall substantially.

8.1 Components of the CDR gap
For the first time, we can compare current and proposed Carbon Dioxide Removal (CDR)
with what would be required in different scenarios that meet the Paris temperature goal.
CDR is required, alongside ambitious emissions reductions, to meet the Paris temperature
goal (see Chapter 1 – Introduction and Chapter 7 – Scenarios). But there are few dedicatedefforts to track the development of CDR policy and deployments226, 244, and none that
estimate the size of the “CDR gap”. It remains unclear to date, therefore, whether current
efforts are on course to deliver enough CDR.
There are different components of the CDR gap. Here, we present a systematic comparisonof current, proposed and scenario-based CDR to assess how on track we are to meet the Paris
temperature goal. “Current CDR” refers to current levels of CDR deployment (see Box 8.2
and Chapter 6 – Deployment). “Proposed CDR” refers to future CDR levels inferred fromcountry submissions to the United Nations Framework Convention on Climate Change(UNFCCC). These are the Nationally Determined Contribution (NDC) 2030 pledges, andscenarios in the long-term strategies through to 2050 (see Chapter 5 – Policymaking). Finally,“scenario-based CDR” refers to benchmarks of future CDR in scenarios that limit warming to
2°C or lower, drawn from the scientific literature (see Chapter 7 – Scenarios).
The aim of this chapter is to analyse the existence and size of a potential CDR gap, drawing
on strands of information from across the report and building on efforts elsewhere thatassess the ambitions and actions of countries in meeting the temperature goal of the Paris
Agreement227,228.
Current CDR
The assessment of current, proposed and Paris-consistent CDR requires a careful alignmentof different data sources (Box 8.2) and definitions. In this assessment, we have developed a
new analysis of current CDR (see Chapter 6 – Deployment). We begin with the net annual
forest land sink as reported by countries in their national inventories, including harvest,
regrowth and afforestation/reforestation, but excluding deforestation (taking the 20002020 average)191. Across the report, we refer to this as “conventional CDR on land”, and it
mainly consists of CO2 capture and storage in forests and wood products (see Chapter 1 –Introduction for definitions of “conventional” and “novel” CDR).
An important implication of using the forest sink from national inventories is that it differs

87

The State of Carbon Dioxide Removalfrom estimates derived from global bookkeeping models developed in the scientific
literature150,229,230. This is due to differences in how “anthropogenic” emissions and removals
are defined and accounted for. National inventories for land use, land-use change andforestry (LULUCF), following the Intergovernmental Panel on Climate Change (IPCC)
Guidelines231, use an area-based approach that includes all or most of the emissions andremovals occurring on land that countries consider managed. The concept of managed
land used by countries may be broad, for example including parks and protected areas.
Furthermore, national inventories, which are largely based on direct observations, typically
include the combined impacts of both direct and indirect effects on managed land. In
contrast, the bookkeeping model approach separates (1) direct emissions and removals fromanthropogenic drivers (e.g. land-use change, harvest, regrowth) and (2) indirect emissions
and removals due to changes in environmental conditions (e.g. fertilisation from risingatmospheric CO2, climate change, nitrogen deposition).
In this chapter – as well as in Chapter 6 (Deployment) and Chapter 7 (Scenarios) – weremove indirect effects, aligning our measurement of conventional CDR on land withthe bookkeeping model approach and the definition of CDR established in Chapter 1(Introduction). To remove indirect effects, we use the OSCAR Earth system model, following
conventions established in the land-use emissions literature150,222,230. This conversion reduces
the estimate of conventional CDR on land to 2.0 ± 0.9 GtCO2 per year, down from theoriginal estimate (including indirect effects) of 6.4 ± 2.8 GtCO2 per year, as reported innational inventories (Chapter 6 – Deployment). This is smaller than the comparable average
estimate derived from bookkeeping models of 3.1 ± 0.9 GtCO2232, likely owing to thosemodels’ inclusion of more detailed processes (notably of shifting cultivation) that simulate
larger overall gross emissions and removals. The removal of indirect effects has implications
for the other sources of data in the analysis, which we discuss in subsequent sections.
Conventional CDR on land is uncertain to a high degree (approximately ±50%), although fiveyear averages have been relatively stable since 2000.
Anthropogenic activity on land drives emissions from deforestation, as well as removals.
In this analysis, we isolate only the removals. Eliminating global deforestation is a criticalcondition for achieving the Paris temperature goal, but it is not discussed here233.
To the estimate of conventional CDR on land we add the gross annual storage from “novel
CDR” projects. These include Bioenergy with Carbon Capture and Storage (BECCS), Direct
Air Carbon Capture and Storage (DACCS), biochar, enhanced rock weathering and coastal
wetland (blue carbon) management. Only a small component of total current CDR is fromsuch novel CDR methods (0.002 GtCO2 per year).
The resulting estimate of total current CDR is 2.0 GtCO2 per year, of which 99% isconventional CDR on land. For comparison, total net greenhouse gas (GHG) emissions as aresult of human activity – including removals as well as emissions from deforestation in theland sector – were 59 GtCO2e in 20191.
Proposed CDR
Based on the available information, national policymaking on CDR is in its infancy, andfew countries have proposed a significant scaling of CDR in documents submitted to the
UNFCCC. This finding is based on a qualitative analysis of policy activity in leading countries(see Chapter 5 – Policymaking) and a quantitative assessment of NDCs and long-term
mitigation strategies (see Box 8.2).
The NDCs indicate that countries plan to slightly increase current levels of conventional CDR

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The State of Carbon Dioxide Removal
on land up to 2030. Unconditional pledges in the NDCs amount to approximately 2.1 GtCO2
per year in 2030, while conditional pledges amount to 2.6 GtCO2 per year (see Box 8.2 forthe differences between conditional and unconditional pledges). Many countries pledge
to reduce deforestation emissions, but only a few pledge to increase forest sinks. Together
with a few countries that project a decline in their sinks, an overall small net increased
in conventional CDR on land is implied by the NDCs. No countries pledge a significant
upscaling of novel CDR methods in their NDCs.
Nonetheless, a lack of transparency hinders assessment: many countries indicate that the
LULUCF sector is a component of their pledge, but few provide sufficient information to
fully quantify this contribution, particularly in terms of the forest sink, potentially leading toan underestimate153, 234. To date, no countries have included novel CDR in their NDCs, even
if some mention – but do not quantify – methods such as coastal wetland management orcomponents of CDR such as Carbon Capture and Storage in their qualitative description ofplanned mitigation efforts. The relative lack of attention given by policymakers to novel CDR
is further evidenced by the limited number of BECCS, DACCS and biochar projects in thepipeline. Currently announced projects will amount to just a small addition of 0.009 GtCO2
per year in 2025, on top of existing capacity (see Chapter 6 – Deployment).
Out to 2050, the long-term mitigation strategies indicate that governments are starting toconsider a wider portfolio of methods beyond conventional CDR on land. Unfortunately,
only a limited number of countries have published long-term mitigation strategies (unlike
NDCs, countries are not obligated to publish such strategies under the Paris Agreement;
see Box 8.2). Further, the strategies and scenarios in these documents are not formal
policy commitments by countries but, rather, illustrate how governments may choose to
mitigate emissions in the longer term and, in particular, how net-zero emissions could bereached. Many of those submitted contain ambiguities and lack transparency. As a result,the long-term mitigation strategies are a pragmatic, but very imperfect, starting point for anassessment of proposed removals up to 2050.
Of the 53 long-term mitigation strategies submitted by the end of September 2022, only
22 outline mitigation scenarios with quantifiable CDR levels in 2050. Taking the highest
combined estimate of CDR from these scenarios, removals total about 2.9 GtCO2 per year in
2050, of which the majority (78%) is conventional CDR on land. The lowest estimate is 2.1
GtCO2 per year, of which 70% is conventional CDR on land. The range reflects the differing
scenarios outlined by governments, which have different balances of emission reductions
versus CDR deployments.

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The State of Carbon Dioxide Removal

Box 8.2 Sources used to estimate the CDR gap andtheir uncertainties
Current Carbon Dioxide Removal (CDR) in this assessment is based on the forest land
sink in national greenhouse gas inventories, taking the 2000-2020 average of ~2.0 GtCO₂
per year compiled in Grassi et al.¹⁹¹. This is combined with a database of existing Bioenergy
with Carbon Capture and Storage, Direct Air Carbon Capture and Storage, biochar,enhanced rock weathering and coastal wetland (blue carbon) management projects (seeChapter 6 – Deployment for further details). There are large uncertainties in land-based
removals due to data limitations in inventories and complex impacts of both humanand natural drivers. Further, there are uncertainties in the number of known novel CDR
projects (limited data is available for projects in China, for instance) and their verified
levels of storage.
Proposed CDR levels are based on countries’ Nationally Determined Contributions (NDCs)
and long-term mitigation strategies, both of which are submitted by countries to theUnited Nations Framework Convention on Climate Change under the Paris Agreement.
Private sector announcements are not included here, although early indications suggest
they may be substantial (see Chapter 3 – Innovation).
A large amount of literature is dedicated to analysing the NDCs and their implications
for the land use, land-use change and forestry flux in 2030, which requires a number ofassumptions to be made¹⁵²,¹⁵³,²³⁴,²³⁵. Since this chapter focuses on the forest land sink only,
we take the 2011-2020 average forest sink from Grassi et al. (2022)¹⁹¹ as the baseline forremovals in the NDCs. We then document where countries commit to additional specificremovals or changes to the forest sink in their NDCs, using all documents available byJune 2022 following the method of Grassi et al. (2017)¹⁵³. “Conditional” pledges are thesum of pledges that would be fulfilled on the condition that stated actions are taken byother countries (e.g. some countries base their pledges on the condition that they areprovided with climate finance or assistance). “Unconditional” pledges refer to those thatwould be taken regardless of action in other countries.
Proposed CDR in 2050 is quantified using the scenarios in the long-term mitigation
strategies (also known as the Long-term Low Emissions Development Strategies, or
LT-LEDS). We build on recent efforts to summarise the 2050 CDR levels described inthese documents¹⁴⁹,²³⁶, finding that as of September 2022 such information exists formost European Union countries, the Russian Federation and the United States, but few
others. We extract levels of CDR by 2050 from the underlying scenarios in the long-term
mitigation strategies, where available, excluding all “business as usual” or “no policy”
scenarios in order to have a comparable set that incorporates climate action. Somelarge emitters such as China, India and Indonesia have submitted a long-term mitigation
strategy but do not provide sufficient information to quantify CDR efforts, while manyothers have yet to submit one.

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The State of Carbon Dioxide Removal

In their scenarios, most countries describe the net flux of emissions and removals, rather
than removals only. For simplicity, we assume that no deforestation occurs in 2050 underthese scenarios and therefore count these net fluxes as removals. This is supported by thefact that countries with high current levels of deforestation, such as Brazil, the Democratic
Republic of the Congo, and Indonesia, do not have a quantified long-term mitigation
strategy, while other countries with lower current levels of deforestation that do have aquantified scenario, such as Cambodia and Colombia, aim to achieve zero deforestation in
their long-term strategies. Of course, this likely underestimates total removals from thesecountries in 2050, as a certain baseline of emissions on land will always occur, but here
we opt for a transparent and simple approach to render the long-term mitigation strategy
data comparable with proposed and scenario-based CDR.
The NDCs and long-term strategies are oriented around national inventories and hence
include indirect anthropogenic effects, such as CO₂ fertilisation. We therefore remove
indirect effects in the NDCs and long-term strategies to render them comparable with theestimates of current and scenario-based CDR. We do this by distinguishing (1) maintained
current sinks and (2) newly proposed sinks in the NDC pledge or long-term strategy
scenario. These can be distinguished from the document texts or by cross-referencing
them with current national inventories. For (1), we apply the ratio of direct to direct andindirect removals (2.0/6.4), as identified in Chapter 6 (Deployment). For (2), we preserve
the original value, as newly proposed afforestation or regeneration implies largely direct
removals. For example, the Russian Federation’s long-term strategy proposes to expand
the current flux of ~650 MtCO₂ per year to 1,200 MtCO₂ per year; we assume a direct
current sink of ~200 MtCO₂ per year (650 × (2.0/6.4)), plus an additional 550 MtCO₂ peryear of direct removals, for a total of 750 MtCO₂ per year. We apply a global ratio of direct
to direct and indirect removals, which may obscure differing contributions of indirect
effects by region or biome (an important issue for future research).
Scenario-based CDR levels are based on scenarios drawn from the integrated assessment
model (IAM) literature. These scenarios depict alternative future pathways of how the
global energy and land-use system can evolve to limit global temperature rise to 1.5°C
and 2°C. We use the Intergovernmental Panel on Climate Change Sixth Assessment
Report (IPCC AR6) IAM scenario database, scenario categories C1-C31. These categories
have varying probabilities of limiting temperature rise, as well as different levels of peakwarming (see Table 7.1 in Chapter 7 – Scenarios). Not all the scenarios are necessarily
consistent with the goal of the Paris Agreement. Collectively, we refer to all C1-C3
scenarios as “2°C or lower” scenarios.

Scenarios that limit warming to 1.5°C or 2°C
The amounts of CDR required to limit warming to 2°C or lower are represented here using
integrated assessment model scenarios (see Box 8.2 and Chapter 7 – Scenarios). A consistentcharacteristic of these scenarios is that they all feature multiple gigatonnes of carbon
removals annually. However, the amount of CDR in scenarios varies considerably, shaped bya number of factors (see Chapter 7 – Scenarios, Section 7.3).
Table 8.1 depicts the additional CDR by 2030 and 2050 projected across all the scenarios
considered. In the second half of the century, conventional CDR on land tends to saturate
or even decline, while most of the growth then occurs through novel CDR methods such as
BECCS and DACCS (see Figure 7.1 and Table 7.2 in Chapter 7 – Scenarios).

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The State of Carbon Dioxide Removal
Table 8.1. Additional Carbon Dioxide Removal (CDR) in scenarios from 2020 to 2030 and 2050. 2°C or lower
scenarios are reported as the median and 5-95th percentiles. In the lower range of some of these scenarios,
conventional CDR on land actually decreases compared with 2020, explaining the negative numbers. The
additional conventional CDR on land in the long-term mitigation strategies(*) is based on the difference between
the land use, land-use change and forestry flux in country scenarios versus their latest national inventories in 2020,
converted to remove indirect effects.

Scenarios

Additional conventional
CDR on land from 2020
(GtCO2 per year)
2030
2050

Additional novel CDR
from 2020(GtCO2 per year)
2030
2050

Additional CDR (total)from 2020(GtCO2 per year)
2030
2050

2°C or lower

0.8 [-0.11 - 3]

0.059 [0 - 1.1]

0.96 [0 - 3.4]

scenarios
Focus on

2.5

2.7 [0.52 - 9.7][-1.8 - 6.2]

4.8[-0.58 - 13]

1

2.3

0

0

1

2.3

2.7

4.1

0.14

0.91

2.9

5.1

0.66

4.0

0.95

3.5

1.6

7.4

[0.1 - 0.65]

NA

0

NA

[0.1 - 0.65]

NANA[0.9 - 1.7]*

NA

-0.6

NA

[1.5 - 2.3]*

DemandReduction
Focus onRenewables
Focus on Carbon Removal
Nationally
Determined
Contributions(NDCs)
Long-term
mitigation
strategies

In addition to the full set of scenarios, we highlight three illustrative scenarios, which
depict different ways to meet the Paris temperature goal (see Chapter 7 – Scenarios). These
scenarios do not cover the whole range of possible scenario futures, but they illustrate thatkey mitigation choices deeply influence how much CDR will be required by mid-century.
• Focus on Demand Reduction – Global energy demand is rapidly reduced through improvements in the efficiency of end-use devices and service delivery. This scenario
limits warming to 1.5°C with a large contribution from conventional CDR on land (4.8
GtCO2 in 2050) but no additional CDR deployments from novel CDR.
• Focus on Renewables – This scenario limits warming to 1.5°C by implementing a rapid
supply-side transformation, based on the deployment of increasingly cost-competitive
renewable energy technologies. It also envisions a large contribution from conventional CDR on land (6.7 GtCO2 in 2050), but this is complemented by removals from
BECCS (0.91 GtCO2 in 2050).
• Focus on Carbon Removal – This scenario holds warming to 1.5°C but envisions a slower
transformation of the energy supply system with an incomplete phase out of fossil
fuels. This scenario also has a large contribution from conventional CDR on land (6.3
GtCO2 in 2050), but significantly more CDR from BECCS and DACCS than in the other illustrative scenarios (3.5 GtCO2 in 2050). This scenario does not feature extreme
scaling behaviour for novel CDR but is close to the median of C1 scenarios

92The State of Carbon Dioxide Removal
All three illustrative scenarios involve immediate, rapid and sustained emission reductions,reaching a peak in global net GHG emissions in 2020 or shortly after, placing them on a path tonet-zero CO2 emissions between 2050 and 2065 (see Figure 7.2 in Chapter 7 – Scenarios). Focus
on Demand Reduction reduces gross GHG emissions by 48% between 2020 and 2030, whereas
Focus on Renewables and Focus on Carbon Removal reduce them by 31% and 33%, respectively.

8.2 The CDR gap: Conventional CDR on land
Almost all scenarios that limit warming to 2°C or lower expand conventional CDR on land.
Yet even maintaining current conventional CDR on land requires dedicated policies andmanagement.
Figure 8.1 brings together estimates of current and proposed levels of CDR and compares
these with 2°C or lower scenarios. In this comparison, we observe that current levels of CDR(2.0 GtCO2 per year) need to be at least maintained in the coming decades: all scenariosthat reach the Paris Agreement goal require a baseline level of removals to counterbalance
expected residual emissions. Maintaining current levels of CDR – which, as it stands, arealmost entirely attributable to conventional CDR on land – is a precondition for limiting
warming to 2°C or lower. Yet the majority of scenarios do not just maintain current
conventional CDR on land but expand it in the coming decades (Table 8.1).
Insofar as we can infer from the NDCs, countries indeed plan to slightly increase current
conventional CDR on land. However, these increases fall short of those projected in the
scenarios. Proposed CDR from conditional NDCs reaches 2.6 GtCO2 per year in 2030, with
0.65 GtCO2 of additional CDR entirely from conventional CDR on land (the NDCs do notinclude any novel CDR). In comparison, the further expansions in conventional CDR on land in
our three focus scenarios by 2030 are quantified at an additional 0.66 GtCO2 per year (Focus on
Carbon Removal), 1.0 GtCO2 per year (Focus on Demand Reduction) and 2.7 GtCO2 per year (Focus
on Renewables). These all give rise to a potential near-term ambition gap. Our focus scenarios
characterise the range that most scenarios in the IPCC WG3 database span, but we note theexistence of scenarios with even higher deployments of conventional CDR on land by 2030.
Further, there is a clear signal in the long-term strategies that forest sinks are a key
component of net zero targets. Among those countries with quantifiable scenarios, mostplan to at least maintain current forest sinks, while there are several prominent examples ofambition to expand these removals, such as scenarios from the United States (an increase
from 0.8 GtCO2 per year in 2020 to 1.3 GtCO2 per year in 2050) and the Russian Federation(an increase from 0.7 GtCO2 per year in 2020 to 1.2 GtCO2 per year in 2050). However,these country estimates include indirect effects; when indirect effects are removed andcountry scenarios are aggregated, newly proposed conventional CDR on land is muchsmaller, at 0.9-1.7 GtCO2 per year. This compares to expansion in our three focus scenarios
quantified at 3.9 GtCO2 per year (Focus on Carbon Removal), 2.3 GtCO2 per year (Focus on
Demand Reduction) and 4.1 GtCO2 per year (Focus on Renewables). Nonetheless, a numberof countries with large land areas and potentially significant ambitions regarding other CDR
methods are absent from this 2050 data, including Brazil, China and India, whose inclusion
would very likely significantly increase proposed CDR levels for 2050.
Countries will need to implement land-use policies and forest management practices justto maintain current conventional CDR on land. These removals are sustained in managed
forests by balancing growth and harvest, shifting carbon stocks to long-lasting wood products,

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The State of Carbon Dioxide Removal
and promoting afforestation and reforestation. Forest fires, pests and other disturbances
will increasingly threaten conventional CDR on land owing to global warming, requiring
further interventions (e.g. thinning, prescribed fires) to preserve these removals237. Very highuncertainties in current (and hence future) levels of conventional CDR on land mean that it may
not be precisely known if these removals are on track to match requirements in the scenarios.
Further, countries may have to deal with a weakening of indirect effects, such as CO2
fertilisation, as atmospheric CO2 levels stabilise. In Paris-relevant scenarios, indirect effects
could be halved by 2050150. It is unclear whether such a weakening is accounted for innational long-term strategies. If not, countries may find that they cannot reach net zero under
their current plans for scaling conventional CDR on land. On the other hand, if countries
do not reduce emissions in line with the Paris temperature goal, indirect effects would bepreserved to some extent, but forest sinks would instead be threatened by climate impacts.
The future robustness of forest sinks is therefore far from guaranteed.

8.3 The CDR gap: Novel CDR
Almost all scenarios that limit warming to below 2°C require novel CDR to be scaled up,
but countries currently have few firm plans to do this.
Almost all scenarios that limit warming to below 2°C do not just increase conventional CDR
on land but also scale up novel CDR rapidly in the coming decades. In the case of Focus
on Renewables and Focus on Carbon Removal, novel CDR is already implemented by 2030,
amounting to 0.14 and 0.95 GtCO2 per year, respectively. Across all below 2°C scenarios,
there is a median of 0.059 (0 to 1.1) GtCO2 per year of novel CDR by 2030. While thesenumbers may appear small, they mean growing novel CDR deployment by a factor of 30 (0 to540), within seven years.
Although many pathways that limit warming to below 2°C highlight stark demands fornovel CDR even in the short- to mid-term, countries so far only have limited plans to scale
it up (Chapter 5 – Policymaking), and the NDCs do not include any such plans. However,
the innovation literature highlights that the early years of technology development (the“formative phase”) are consequential in determining how fast and to what level novel CDR
can be scaled in the longer term238. The extent of early deployment of novel CDR over the
next decade is therefore crucial, as a failure to create momentum in this formative phase willcontribute to a widening gap by 2050 and beyond.
Looking to 2050, the most ambitious scenarios in the long-term mitigation strategies
describe total novel CDR removals of 0.6 GtCO2 per year, mainly driven by the United States(0.5 GtCO2 per year). Again, this falls short of scale-up rates in the scenarios, which range
from novel CDR levels of 0.91 (Focus on Renewables) to 3.5 GtCO2 per year (Focus on Carbon
Removal), or 450 to 1,750 times larger than current levels. Across the entire sample of below
2°C scenarios, many scale up CDR even more by 2050 – with a median of 1,300 times (260
to 4,900) greater than today’s level.
Only 22 countries have so far submitted quantifiable long-term strategies. While it is possiblethat the shortfall of novel CDR could be made up by new countries submitting long-term
mitigation strategies with underlying scenarios, so far most country scenarios have a far
greater focus on conventional CDR on land than on novel CDR. If we include indirect effects

94

The State of Carbon Dioxide Removal(as is standard practice in reporting by countries), then just 16-21% of removals in the longterm strategies come from novel CDR. This suggests that a serious “CDR ambition gap” isemerging: few countries have developed transparent plans to scale novel CDR, leaving asignificant shortfall between proposed and scenario-based CDR by 2050.
The extent of future carbon dioxide removal depends on the scenario by which the paris temerature goal is met
2010

2020

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CDR in Paris-relevant scenarios

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Focus on renewables(31% GHG reduction
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Current and proposed levels of carbon dioxide are insuﬃcient to meet the Paris temperature goal
2020

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Figure 8.1. The CDR gap. Carbon Dioxide Removal (CDR) includes conventional CDR on land (the managed
forest land sink) plus novel CDR (gross removals from Bioenergy with Carbon Capture and Storage, Direct Air
Carbon Capture and Storage, biochar, enhanced rock weathering and coastal wetland (blue carbon) management).
Conventional CDR on land estimates exclude sinks that are treated as “natural” or “indirectly human induced” inthe global carbon budgeting literature. In the upper panel, the blue line depicts total current CDR and the shaded
blue area indicates the uncertainty. The orange shaded area depicts the 5th to 95th and 25th to 75th percentile
of Intergovernmental Panel on Climate Change C1-C3 scenarios that limit warming to below 2°C. The orange lines
depict three Focus Pathways that limit warming to 1.5°C, based on varying assumptions of action and technology
diffusion. The emission reductions described for each scenario in the top panel refer to gross greenhouse gas (GHG)
emissions. The lower panels show the contributions of conventional CDR on land and novel CDR in the Focus
scenarios, as well as the overall scenario median and ranges (as in the top panel), versus estimates of current andproposed CDR from Nationally Determined Contributions (NDCs) and long-term mitigation strategies. It also depicts
the relative scale-up of each category compared with levels in 2020. In the case of conventional CDR on land in the95

The State of Carbon Dioxide Removal
long-term strategies, this refers to the difference between the land use, land-use change and forestry flux in country
scenarios versus those countries’ latest national inventories in 2020. In the case of the scenario ranges, the medianand 5th to 95th factor change is shown.

8.4 A low-CDR world
A few scenarios meet the Paris temperature goal with only a small expansion of CDR, butthey require aggressive reductions in GHG emissions, which we are not on track to achieve.
There are some scenarios that project comparatively modest increases in current
conventional CDR on land, while avoiding novel CDR altogether. These scenarios lie at thelowest end of total CDR requirements across the 21st century and include the Focus on
Demand Reduction illustrative scenario, which slightly more than doubles current conventional
CDR on land to 4.8 GtCO2 per year by 2050. A comparison of current and proposed CDR
with these scenarios would suggest that the overall CDR gap is manageable, so long asefforts to expand current conventional CDR on land to meet these levels are successful.
However, a key feature of these low-CDR scenarios is that they involve highly ambitious andrapid emission reductions. Focus on Demand Reduction requires an immediate implementationof climate policies leading to a global emissions peak in 2020, followed by a rapid pathway to
net-zero CO2 emissions by 2059239. Total gross GHG emissions between 2020 and 2030 are
reduced by 48% (30GtCO2eq) in this scenario.
To what extent is such a pathway still within reach? According to the latest assessmentof the “emissions gap”, current policy scenarios project emissions of 58 GtCO2 in 2030,
while unconditional and conditional NDC scenarios project emissions of 55 and 52 GtCO2,
respectively240. In other words, global GHG emissions are set to remain approximately stablebetween now and 2030 if the unconditional NDCs are implemented or to slightly decrease
if conditional NDCs are implemented. Furthermore, as of 2021, global GHG emissions havebegun to grow again240,241. This suggests that key milestones for planning ambitious mitigation
pathways, implementing policies and reducing emissions are not being met, pushing a lowCDR worldfurther out of reach.

8.5 Closing the CDR gap
Closing the CDR gap requires us to rapidly reduce emissions, expand conventional CDR on
land rapidly scale up novel CDR. If novel CDR is not supported now, during the formative
phase of technology development, countries risk a widening CDR gap by 2050. For every
year that GHG emissions do not fall substantially, our dependence on CDR increases.
The scenario literature unequivocally highlights that reducing GHG emissions to a small
fraction of today’s levels is the foundation for limiting global temperature rise to 2°C or
below. The faster this happens, the better the chance we have of scaling up CDR sustainably:
lower cumulative and residual emissions will ultimately reduce the amount of CDR we require
to reach net-zero GHG emissions and to achieve the Paris temperature goal (Chapter 7 –Scenarios).
For every year in which GHG emissions do not fall substantially, our dependence on

96The State of Carbon Dioxide Removal
CDR increases and a low-CDR world is pushed further out of reach. Key milestones for
implementing policies, peaking emissions and ultimately achieving the required emission
reduction rates are being missed. As such, it is critical to redouble mitigation efforts but also
to explore opportunities for integrated, cross-sector policies that can support both emission
reductions and CDR upscaling. For instance, a food system transition to lower meat diets
would lower “hard-to-abate” emissions in the agriculture sector that otherwise must becompensated for by CDR, while potentially freeing up space for forest sink removals242,243.
Developing novel CDR is an important climate measure, given our increasing dependence onsuch technologies. The lack of comprehensive information, plans and priorities on novel CDR
from countries is especially problematic given the long time horizon needed to safely scale
up these methods (see Chapter 3 – Innovation). Scenarios already implement substantial
novel CDR levels by 2050, reflecting matured BECCS, DACCS, biochar and enhanced rockweathering industries with technologies ready for widespread adoption. Achieving short- to
medium-term milestones along the long road to these levels is therefore key, highlighting theneed for increased research, investment and policy support for novel CDR.
Pathways that limit warming to 1.5°C or 2°C start scaling novel CDR before 2030. While levelsof novel CDR may appear small, they imply substantial increases in deployments. Just 0.1
GtCO2 removed by novel CDR in 2030 implies an increase in current levels by a factor of 50 by
the end of the decade. Furthermore, the literature on technology upscaling has shown that theearly, formative phases of technology development will strongly determine what contribution
novel CDR can make to climate mitigation by mid-century238. If novel CDR does not receive
support during this formative phase, ensuring that these technologies are ready to deliversignificant removals in a few decades, countries risk a widening CDR gap by 2050.
Ultimately, this report highlights three key criteria for closing the CDR gap. First, current
conventional CDR on land needs to be expanded, likely requiring additional policies and theactive management of forest sinks to protect removals from future climate impacts. Second,novel CDR needs to be developed and scaled to meet future possible needs, which will require
active support and investment from countries. Third, and above all, our dependence on CDR
needs to be limited by implementing stringent emission reductions as soon as possible.

97

“There are gaps to close,
further areas to analyse, andopportunities to improve beyond
this first assessment.”

The State of Carbon Dioxide Removal

Chapter 9 | Future assessments
This report represents a first step towards a comprehensive scientific assessment of thestate of Carbon Dioxide Removal (CDR). It builds on and complements a growing number of
initiatives to improve the information landscape around CDR. We, the scientific convenorsof this report, believe that such an assessment has an important role to play, informing andaiding the efforts of those who seek to develop CDR as part of successful climate action.
There are, however, gaps to close, further areas to analyse, and opportunities to improve
beyond this first step. The sections below synthesise the priority areas we have identified, on
which assessments in subsequent years can build.

9.1 Expanding the community
Nearly 30 experts have contributed to this report, across three continents and a rangeof disciplines. And yet our author team is concentrated in Europe and North America,
representing only a subset of relevant contexts and perspectives for understanding andtracking CDR developments. We are keen to grow the community to make CDR information
more complete, reliable, accessible and inclusive. Specific opportunities for expanding thecommunity include:• Providing updated assessments of the state of individual CDR methods with regard
to costs, potentials, hazards, co-benefits, technology readiness, potential and otherfactors.
• Incorporating scientific literature in other languages, grey literature, and local andindigenous knowledge.
• Locating and reviewing research on public perceptions from specific stakeholder
groups (e.g. local communities affected by deployment, indigenous groups facing land
conflicts).
• Assembling a more complete picture of research and innovation across countries
and methods, similar to the process followed by the International Energy Agency forenergy Research, Development and Demonstration (RD&D) and by the International
Renewable Energy Agency for tracking renewable projects and their pipelines.
• Broadening the analysis of CDR policies and governance. This includes quantifying
CDR plans beyond those in United Nations Framework Convention on Climate
Change (UNFCCC) documents. It may also include case studies of other countries, forinstance high-income economies with different emissions profiles (such as Australia,
Finland, Iceland, New Zealand, Sweden and Switzerland), emerging economies withgrowing emissions (such as China, India, and Indonesia) and low-income countries
with low emissions levels but high CDR potential. More attention to policy instrument
design and evaluation would be valuable, including in areas such as monitoring,
reporting and verification.
• Developing local-level and up-to-date information on CDR projects. Currently, ourdata on novel CDR deployment has limited geographic coverage, with most recorded
CDR projects in Europe and North America. The data also generally provides limited
coverage of CDR methods such as biochar, which often produce CDR via a large

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The State of Carbon Dioxide Removal
number of small, independently owned plants instead of large commercial plants, asis the case for Bioenergy with Carbon Capture and Storage and Direct Air Carbon
Capture and Storage.

9.2 Improving the data
Throughout this report, we highlight a number of areas in which data is hard to assess, isincomplete or is missing. A better picture of the state of CDR is possible, particularly with thefollowing additions:• The scientific literature on CDR is vast and growing. Manual tracking and synthesising
is now intensive and inefficient. Different scientific communities are adopting “living
evidence” as a new paradigm for informing research, policy and practice. Using themachine-learning pipeline we have developed for tracking CDR research, we wantto create a “living map” of CDR evidence – an interactive, open access and publicly
available tool. Such a map can support other elements of evidence synthesis in thisassessment, such as on technology readiness, cost, mitigation potential, hazards andco-benefits.
• Our assessment of innovation could include data from RD&D programmes that
include CDR methods but that are not labelled as such (particularly land-based
methods). Innovation investments by the private sector are typically harder tomeasure but are likely to be increasingly important as the industry matures.
• Governments could provide greater consistency, transparency and detail on how
countries intend to balance sources and sinks of greenhouse gases. The Nationally
Determined Contributions provide sparse information regarding conventional CDR on
land and none on novel CDR. Long-term mitigation strategies do so in part, but only
for a limited number of countries.
• As noted in Section 9.1, data for current novel CDR deployment is limited. No single
repository exists to track all projects. Where available, information is not standardised
and is often limited. In particular, our estimates are for gross amounts of CO2
captured and do not account for the greenhouse gas balance over the full project
lifecycles. Ideally, project data should include the CDR pathway used (i.e. the carbon
pools between which carbon is moved), the location of activity, the time series ofgreenhouse gas sources and sinks during the full project lifecycle (including any rerelease of carbon back into the atmosphere), and the time series of any subsequenttransfers of carbon between non-atmospheric pools (including any fossil carbon
captured during the process).
• Long-term scenarios from modelling groups should be collected and vetted moreregularly and should include more detail on CDR. Specific outputs are needed
for conventional CDR on land, and estimates of the gross land sink should beharmonised across different land-use models, as this is a key uncertainty in assessing
and comparing the CDR levels within these scenarios. There is also scope for new
scenarios that include broader portfolios of novel CDR.

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The State of Carbon Dioxide Removal

9.3 Honing the analysis
There is further scope to clarify key concepts around CDR, develop consistent analytical
approaches and improve analytical tools. This includes:• Resolving definitional issues for CDR. In particular, durability is a key concept, but one
that is not clearly defined for practical applications. It will be important to improvedefinitions and categorisation of CDR methods in ways that are widely agreed,scientifically justified and relevant for decision-making²⁴⁸.
• Tracking emergent new CDR methods. The pace of innovation means that new
methods are being proposed and tested rapidly, through either new processes for
capture, conversion and storage or new combinations of existing processes. Suchtracking will require analysis not only of scientific publications but also of patents,
projects and companies.
• Adopting a more consistent approach to CDR methods across the analyses ofinnovation, public perception, policy, deployment and scenarios. Currently, theanalyses we draw from adopt sets of varying detail and completeness. Some focus
only on components of CDR methods (e.g. Direct Air Capture without consideringstorage) or exclude some methods (e.g. converting biomass to bio-oil injected into
geological storage).
• Tracking policy developments more thoroughly in several ways, such as through casestudies of states and cities developing CDR policies, analysis of interactions between
government action and the private sector (including voluntary markets and advancepurchase agreements), analysis of developments in the UNFCCC, evaluation ofmultilateral agreements and cooperation platforms (such as the Bonn Challenge, the4p1000 Initiative and Mission Innovation on CDR), and analysis of developments tomonitor, report and verify CDR activities.
• Encouraging inclusion and analysis of a broader set of CDR methods in integrated
assessment models. This would enable a better understanding of how different CDR
methods interact and how deployment risks can be hedged via more methods, each
deployed at more moderate scales.
• Further improving methods for calculating conventional CDR on land. Generatingcomparable estimates for current, planned and Paris-consistent levels has required
us to make assumptions about land emissions (from deforestation in particular) andindirect effects. These are a step forward but remain an approximation. Countries
could improve this by separately reporting sources and sinks as well as direct andindirect fluxes from managed land. In addition, our initial methods for estimating
indirect effects, both now and in the future as the climate changes, can be improved.

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References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.

20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.

IPCC. Summary for Policymakers. in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the
Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. et al.) (Cambridge University Press,2022).
Hans, F., Kuramochi, T., Black, R., Hale, T. & Lang, J. Net Zero Stocktake 2022. https://zerotracker.net/analysis/net-zero-stocktake-2022.
Minx, J. C. et al. Negative emissions—Part 1: Research landscape and synthesis. Environ. Res. Lett. 13, 063001 (2018).
Fuss, S. et al. Negative emissions—Part 2: Costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018).
Nemet, G. F. et al. Negative emissions—Part 3: Innovation and upscaling. Environ. Res. Lett. 13, 063003 (2018).
Bui, M. & Mac Dowell, N. Greenhouse Gas Removal Technologies. (Royal Society of Chemistry, 2022).
Wilcox, J., Kolosz, B. & Freeman, J. CDR Primer. (2021).
CDR Database. Carbon Plan https://carbonplan.org/research/cdr-database.
Energy Transitions Commission. Mind the Gap: How Carbon Dioxide Removals Must Complement Deep Decarbonisation to Keep
1.5°C Alive. https://www.energy-transitions.org/publications/mind-the-gap-cdr/ (2022).
Greenpeace UK. Net expectations: assessing the role of carbon dioxide removal in companies’ climate plans. https://www.greenpeace.org.uk/resources/net-expectations-cdr-briefing/ (2021).
van Diemen, R. et al. IPCC, 2022: Annex I: Glossary. in IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. etal.) (Cambridge University Press, 2022).
Zero Emissions Platform. Europe needs a definition of Carbon Dioxide Removal. https://zeroemissionsplatform.eu/europe-needs-a-definition-of-carbon-dioxide-removal/ (2020).
Babiker, M. et al. Cross-sectoral perspectives. in IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contributionof Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. et al.)(Cambridge University Press, 2022).
Buendia, E. et al. Refinement To the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. (2019).
Lyngfelt, A., Johansson, D. J. A. & Lindeberg, E. Negative CO2 emissions - An analysis of the retention times required with respect
to possible carbon leakage. Int. J. Greenhouse Gas Control 87, 27–33 (2019).
Fankhauser, S. et al. The meaning of net zero and how to get it right. Nat. Clim. Chang. 12, 15–21 (2022).
Australian Government Clean Energy Regulator. The Emissions Reduction Fund and permanence on the land. https://www.cleanenergyregulator.gov.au/DocumentAssets/Pages/The-Emissions-Reduction-Fund-and-permanence-on-the-land.aspx (2018).
California Air Resources Board. Carbon Capture and Sequestration Protocol under the Low Carbon Fuel Standard. https://ww2.
arb.ca.gov/sites/default/files/2020-03/CCS_Protocol_Under_LCFS_8-13-18_ada.pdf (2018).
Nabuurs, G-J., R. Mrabet, A. Abu Hatab, M. Bustamante, H. Clark, P. Havlík, J. House, C. Mbow, K.N. Ninan, A. Popp, S. Roe, B.
Sohngen, S. Towprayoon. Agriculture, Forestry and Other Land Uses (AFOLU). in IPCC, 2022: Climate Change 2022: Mitigationof Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate
Change (eds. Shukla, P. R. et al.) (Cambridge University Press, 2022).
United Nations Environment Programme. Emissions Gap Report 2017. http://www.unep.org/resources/emissions-gap-report-2017(2017).
Bellamy, R. & Osaka, S. Unnatural climate solutions? Nat. Clim. Chang. 10, 98–99 (2020).
Seddon, N. et al. Getting the message right on nature-based solutions to climate change. Glob. Chang. Biol. 27, 1518–1546 (2021).
Sandalow, D., Aines, R., Friedmann, S. J., McCormick, C. & Sanchez, D. L. Biomass Carbon Removal and Storage (BiCRS) Roadmap.
https://www.icef.go.jp/pdf/summary/roadmap/icef2020_roadmap.pdf (2021).
Berrang-Ford, L. et al. Systematic mapping of global research on climate and health: a machine learning review. The Lancet Planetary Health 5, e514–e525 (2021).
Haddaway, N. R. et al. On the use of computer-assistance to facilitate systematic mapping. Campbell Systematic Reviews 16,(2020).
Callaghan, M. W., Minx, J. C. & Forster, P. M. A topography of climate change research. Nat. Clim. Chang. 10, 118–123 (2020).
Callaghan, M. et al. Machine-learning-based evidence and attribution mapping of 100,000 climate impact studies. Nat. Clim. Chang.
11, 966–972 (2021).
Devlin, J., Chang, M. W., Lee, K. & Toutanova, K. BERT: Pre-training of Deep Bidirectional Transformers for Language Understanding. NAACL HLT 2019 - 2019 Conference of the North American Chapter of the Association for Computational Linguistics: Human
Language Technologies - Proceedings of the Conference 1, 4171–4186 (2018).
Minx, J. C., Lamb, W. F., Callaghan, M. W., Bornmann, L. & Fuss, S. Fast growing research on negative emissions. Environ. Res. Lett.
12, (2017).
Bibliography: Greenhouse Gas Removal / Negative Emissions Technologies – Climate Protection and Restoration Initiative. https://
cprclimate.org/bibliography-carbon-dioxide-removal-negative-emissions-technologies/.
Khabsa, M. & Giles, C. L. The number of scholarly documents on the public web. PLoS One 9, (2014).
Minx, J. C., Callaghan, M., Lamb, W. F., Garard, J. & Edenhofer, O. Learning about climate change solutions in the IPCC and beyond.
Environ. Sci. Policy 77, (2017).
Haunschild, R., Bornmann, L. & Marx, W. Climate Change Research in View of Bibliometrics. PLoS One (2016) doi:10.1371/journal.
pone.0160393.
Millar, R. J. & Allen, M. R. Chapter 2 Understanding the Role of CCS Deployment in Meeting Ambitious Climate Goals. in Carbon
Capture and Storage 8–35 (The Royal Society of Chemistry, 2020). doi:10.1039/9781788012744-00008.
Clarke, L. et al. Energy Systems. in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the
Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. et al.) (Cambridge University Press,2022).
Bui, M. et al. Carbon capture and storage (CCS): The way forward. Energy Environ. Sci. (2018) doi:10.1039/c7ee02342a.
Hilaire, J. et al. Negative emissions and international climate goals—learning from and about mitigation scenarios. Clim. Change(2019) doi:10.1007/s10584-019-02516-4.
Riahi, K. et al. Mitigation pathways compatible with long-term goals. in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R.

102

The State of Carbon Dioxide Removal
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.

69.
70.
71.
72.

73.
74.
75.

et al.) (Cambridge University Press, 2022).
Fuss, S. et al. Betting on negative emissions. Nat. Clim. Chang. 4, 850–853 (2014).
Anderson, K. & Peters, G. The trouble with negative emissions. Science 354, 182–183 (2016).
Galik, C. S. A continuing need to revisit BECCS and its potential. Nat. Clim. Chang. 10, 2–3 (2020).
Popp, A. et al. Land-use futures in the shared socio-economic pathways. Glob. Environ. Change 42, 331–345 (2017).
Strefler, J. et al. Carbon dioxide removal technologies are not born equal. Environ. Res. Lett. 16, 74021–74021 (2021).
Gallagher, K. S., Grübler, A., Kuhl, L., Nemet, G. & Wilson, C. The Energy Technology Innovation System. Annu. Rev. Environ. Resour. 37, 137–162 (2012).
The Federal Reserve Bank. Foreign Exchange Rate - H.10. https://www.federalreserve.gov/releases/h10/current/.
Kang, J.-N., Zhang, Y.-L. & Chen, W. Delivering negative emissions innovation on the right track: A patent analysis. Renewable
Sustainable Energy Rev. 158, 112169 (2022).
Höglund, R. List of known CDR purchases. https://docs.google.com/spreadsheets/d/1BH_B_Df_7e2l6AH8_8a0aK70nlAJXfCTwfyCgxkL5C8/edit#gid=0 (2022).
International Energy Agency (IEA). Energy Technology RD&D Budgets: Overview - Analysis. https://www.iea.org/reports/energy-technology-rdd-budgets-overview (2022).
European Commission. Soils: Why does research and innovation on soils matter? https://research-and-innovation.ec.europa.eu/
research-area/agriculture-forestry-and-rural-areas/soils_en.
Australian Department of Industry, Science and Resources. Carbon capture projects receive funding to accelerate technology andreduce emissions. https://www.industry.gov.au/news/carbon-capture-projects-receive-funding-to-accelerate-technology-and-reduce-emissions (2021).
Government of Canada. Net-Zero Emissions by 2050. https://www.canada.ca/en/services/environment/weather/climatechange/
climate-plan/net-zero-emissions-2050.html (2022).
Government of Canada. Net Zero Accelerator Initiative. https://www.ic.gc.ca/eic/site/125.nsf/eng/00039.html (2022).
Government of Canada. Climate Action and Awareness Fund. https://www.canada.ca/en/services/environment/weather/climatechange/funding-programs/climate-action-awareness-fund.html (2022).
International Energy Agency (IEA). An Energy Sector Roadmap to Carbon Neutrality in China. (2022).
China’s Voluntary National Contribution to Achieving the Targets of Global Forest Goals for the United Nations Strategic Plan for
Forests (2017 - 2030). https://www.un.org/esa/forests/wp-content/uploads/2019/05/VNC-China-May2019.pdf (2019).
Regulation of the European Parliament of the Council Establishing the Framework for Achieving Climate Neutrality and Amending
Regulations (EC) No 401/2009 and (EU) 2018/1999 (‘European Climate Law’). vol. L 243/1 (2021).
European Commission. Commission awards over €1 billion to innovative projects for the EU climate transition. https://ec.europa.
eu/commission/presscorner/detail/en/IP_22_2163 (2022).
European Commission. Horizon Europe: Funding Programmes and Open Calls. https://research-and-innovation.ec.europa.eu/funding/funding-opportunities/funding-programmes-and-open-calls/horizon-europe_en.
Carbon Gap. Feedback for Horizon Europe Interim Evaluation. https://ec.europa.eu/info/law/better-regulation/have-your-say/initiatives/13460-Orizzont-Ewropa-evalwazzjoni-interim/F3331927_mt (2022).
Bundesministerium für Bildung und Forschung (BMBF). Research mission ‘Marine carbon storage as a way to decarbonization’ of
the German Marine Research Alliance. https://www.fona.de/de/massnahmen/foerdermassnahmen/210909_Dekarbonisierung.php.
Bundesministerium für Bildung und Forschung (BMBF). Is removing carbon dioxide from the atmosphere feasible, effective andsocially desirable? The new BMBF funding measure CDRterra is researching terrestrial CO2 extraction methods. https://www.fona.
de/de/massnahmen/foerdermassnahmen/co2-entnahmemethoden-cdr.php.
Council for Science, Technology & and Innovation (CSTI) and Headquarters for Healthcare Policy. The basic approach for
the Moonshot Research and Development Program. https://www.jst.go.jp/moonshot/en/application/202002/pdf/f-policy_
en20200227.pdf (2020).
Japan Cabinet Office. Moonshot Goal #4. https://www8.cao.go.jp/cstp/english/moonshot/sub4_en.html.
MOZES Research. Moonshot for beyond Zero-Emission Society. https://mozes.jp/en/research/.
Sosuke Kudo. Toshiba, ‘carbon negative’ in biomass power generation, CO2 separation and recovery. Bikkei Business Publications,
Inc. (2020).
United Kingdom Research and Innovation. The UK Greenhouse Gas Removal from the Atmosphere Research Programme. https://www.ggrprogramme.org.uk/.
HM Government. Net Zero Strategy: Build Back Greener. https://assets.publishing.service.gov.uk/government/uploads/system/
uploads/attachment_data/file/1033990/net-zero-strategy-beis.pdf (2021).
UK Department for Business, Energy & Industrial Strategy. Projects selected for Phase 2 of the Direct air capture and greenhousegas removal programme. https://www.gov.uk/government/publications/direct-air-capture-and-other-greenhouse-gas-removal-technologies-competition/projects-selected-for-phase-2-of-the-direct-air-capture-and-greenhouse-gas-removal-programme(2022).
UK Department for Business, Energy & Industrial Strategy. Direct Air Capture and other Greenhouse Gas Removal technologies
competition. https://www.gov.uk/government/publications/direct-air-capture-and-other-greenhouse-gas-removal-technologies-competition (2020).
UK Research and Innovation. UK invests over £30m in large-scale greenhouse gas removal. https://www.ukri.org/news/uk-investsover-30m-in-large-scale-greenhouse-gas-removal/ (2021).
UK Research and Innovation. Greenhouse Gas Removal Demonstrator (GGR-D) projects. https://www.ukri.org/wp-content/uploads/2021/05/NERC-240521-GreenhouseGasRemovalDemonstratorProjects.pdf.
The White House. FACT SHEET: President Biden Sets 2030 Greenhouse Gas Pollution Reduction Target Aimed at Creating
Good-Paying Union Jobs and Securing U.S. Leadership on Clean Energy Technologies. https://www.whitehouse.gov/briefing-room/
statements-releases/2021/04/22/fact-sheet-president-biden-sets-2030-greenhouse-gas-pollution-reduction-target-aimed-at-creating-good-paying-union-jobs-and-securing-u-s-leadership-on-clean-energy-technologies/ (2021).
U.S. Department of Energy. U.S. Department of Energy’s Carbon Negative Shot - An Introduction. https://www.energy.gov/sites/
default/files/2022-03/3.25.22%20Carbon%20Negative%20Shot_0.pdf (2021).
Government of the United States. Division C: Energy and Water Development and Related Agencies Appropriations Act, 2020.
(2020).
Office of Fossil Energy and Carbon Management. U.S. Department of Energy Announces an Additional $6 Million in Funding for
Four Direct Air Capture Projects. https://www.energy.gov/fecm/articles/us-department-energy-announces-additional-6-mil-

103

The State of Carbon Dioxide Removal
lion-funding-four-direct-air-capture (2021).
Government of the United States. Division D - Energy and Water Development and Related Agencies Appropriations Act, 2021.
(2021).
77. Government of the United States. Division D - Energy and Water Development and Related Agencies Appropriations Act, 2022.
(2022).
78. US Office of Fossil Energy and Carbon Management. U.S. Department of Energy Announces $30 Million to Remove Carbon Dioxidefrom the Air and Oceans and Convert it to Valuable Products. https://www.energy.gov/fecm/articles/us-department-energy-announces-30-million-remove-carbon-dioxide-air-and-oceans-and (2022).
79. Sanchez, D. L., Amador, G., Funk, J. & Mach, K. J. Federal research, development, and demonstration priorities for carbon dioxide
removal in the United States. Environ. Res. Lett. 13, 015005 (2018).
80. A Carbon Removal Collective. OpenAir Collective https://openaircollective.cc/ (2021).
81. Frontier. An advance market commitment to accelerate carbon removal. https://frontierclimate.com/ (2022).
82. BloombergNEF. Energy Transition Investment Trends 2022. https://assets.bbhub.io/professional/sites/24/Energy-Transition-Investment-Trends-Exec-Summary-2022.pdf (2022).
83. Climate Tech VC. Climate funding abides in $19B 2022 midyear update. https://www.ctvc.co/19b-2022-midyear-update/ (2022).
84. Carbon Engineering. 1PointFive & Carbon Engineering Announce Direct Air Capture Deployment Approach to Enable Global BuildOut of Plants. https://carbonengineering.com/news-updates/deployment-approach/ (2022).
85. Climeworks. Climeworks’ DAC Summit Highlights. https://climeworkscom.cdn.prismic.io/climeworkscom/f0b37e8e-00aa-42cba06e-d6697a533af8_Climeworks+DAC+Summit+Highlights+2022.pdf (2022).
86. European Biochar Industry Consortium. European Biochar Market Report 2021-2022. https://www.biochar-industry.com/wp-content/uploads/2022/03/EU-Biochar-Market-Report_2022-03-09.pdf (2022).
87. Gardiner W & Skelton. Drax Full Year Results - 2021. https://www.drax.com/wp-content/uploads/2022/02/Drax-2021-FYR-Analyst-Presentation.pdf (2022).
88. BECCS Stockholm. Carbon Dioxide Removal. https://beccs.se/cdr/.
89. Pernot, E. & Jaruzel, M. Direct air capture is growing around the world, but more policy support is needed. https://www.catf.
us/2022/07/direct-air-capture-growing-around-world-more-policy-support-needed/ (2022).
90. Bidwell, D. Thinking through participation in renewable energy decisions. Nature Energy 1, (2016).
91. Krause, R. M., Carley, S. R., Warren, D. C., Rupp, J. A. & Graham, J. D. ‘Not in (or Under) My Backyard’: Geographic Proximity andPublic Acceptance of Carbon Capture and Storage Facilities. Risk Anal. 34, 529–540 (2013).
92. Batel, S., Devine-Wright, P. & Tangeland, T. Social acceptance of low carbon energy and associated infrastructures: A critical discussion. Energy Policy 58, 1–5 (2013).
93. Cox, E., Spence, E. & Pidgeon, N. Public perceptions of carbon dioxide removal in the United States and the United Kingdom. Nat.
Clim. Chang. 10, 744–749 (2020).
94. Wolske, K. S., Raimi, K. T., Campbell-Arvai, V. & Hart, P. S. Public support for carbon dioxide removal strategies: the role of tampering with nature perceptions. Clim. Change 152, 345–361 (2019).
95. Bellamy, R., Lezaun, J. & Palmer, J. Perceptions of bioenergy with carbon capture and storage in different policy scenarios. Nat.
Commun. 10, 743–743 (2019).
96. Cox, E., Spence, E. & Pidgeon, N. Deliberating enhanced weathering: Public frames, iconic ecosystems and the governance of carbon removal at scale. Public Underst. Sci. 31, 960–977 (2022).
97. Pidgeon, N. Engaging publics about environmental and technology risks: frames, values and deliberation. J. Risk Res. 24, 28–46(2021).
98. Bertram, C. & Merk, C. Public Perceptions of Ocean-Based Carbon Dioxide Removal: The Nature-Engineering Divide? Frontiers in
Climate 2, (2020).
99. Bellamy, R. & Lezaun, J. Crafting a public for geoengineering. Public Underst. Sci. 26, 402–417 (2017).
100. Bolsen, T., Palm, R. & Kingsland, J. T. Effects of Conspiracy Rhetoric on Views About the Consequences of Climate Change andSupport for Direct Carbon Capture. Environ.Commun. 16, 209–224 (2022).
101. Campbell-Arvai, V., Hart, P. S., Raimi, K. T. & Wolske, K. S. The influence of learning about carbon dioxide removal (CDR) on support
for mitigation policies. Clim. Change 143, 321–336 (2017).
102. Carr, W. A. & Yung, L. Perceptions of climate engineering in the South Pacific, Sub-Saharan Africa, and North American Arctic. Clim.
Change 147, 119–132 (2018).
103. Corner, A., Parkhill, K., Pidgeon, N. & Vaughan, N. E. Messing with nature? Exploring public perceptions of geoengineering in the
UK. Glob. Environ. Change 23, 938–947 (2013).
104. Corner, A. & Pidgeon, N. Like artificial trees? The effect of framing by natural analogy on public perceptions of geoengineering.
Clim. Change 130, 425–438 (2015).
105. Corner, A. & Pidgeon, N. Geoengineering, climate change scepticism and the ‘moral hazard’ argument: an experimental study of UK
public perceptions. Philos. Trans. R. Soc. London, Ser. A 372, 20140063–20140063 (2014).
106. Cox, E., Pidgeon, N. & Spence, E. But they told us it was safe! Carbon dioxide removal, fracking, and ripple effects in risk perceptions. Risk Anal. 42, 1472–1487 (2021).
107. Gannon, K. E. & Hulme, M. Geoengineering at the ‘Edge of the World’: Exploring perceptions of ocean fertilisation through the
Haida Salmon Restoration Corporation. Geogr. Environ 5, e00054 (2018).
108. Schirmer, J. & Bull, L. Assessing the likelihood of widespread landholder adoption of afforestation and reforestation projects. Glob.
Environ. Change 24, 306–320 (2014).
109. Lin, J.-C., Wu, C.-S., Liu, W.-Y. & Lee, C.-C. Behavioral intentions toward afforestation and carbon reduction by the Taiwanese public. For. Policy Econ. 14, 119–126 (2012).
110. Wibeck, V. et al. Making sense of climate engineering: a focus group study of lay publics in four countries. Clim. Change (2017)
doi:10.1007/s10584-017-2067-0.
111. Wright, M. J., Teagle, D. A. H. & Feetham, P. M. A quantitative evaluation of the public response to climate engineering. Nat. Clim.
Chang. 4, 106–110 (2014).
112. Klaus, G., Ernst, A. & Oswald, L. Psychological factors influencing laypersons’ acceptance of climate engineering, climate change
mitigation and business as usual scenarios. Technol. Soc. 60, 101222 (2020).
113. Wallquist, L., Seigo, S. L., Visschers, V. H. M. & Siegrist, M. Public acceptance of CCS system elements: A conjoint measurement. Int.
J. Greenhouse Gas Control 6, 77–83 (2012).
114. Sweet, S. K., Schuldt, J. P., Lehmann, J., Bossio, D. A. & Woolf, D. Perceptions of naturalness predict US public support for Soil
76.

104

The State of Carbon Dioxide Removal
Carbon Storage as a climate solution. Clim. Change 166, 22 (2021).
115. Carvalho, A. & Riquito, M. ‘It’s just a Band-Aid!’: Public engagement with geoengineering and the politics of the climate crisis. Public
Underst. Sci. 31, 903–920 (2022).
116. Hart, P. S., Campbell-Arvai, V., Wolske, K. S. & Raimi, K. T. Moral hazard or not? The effects of learning about carbon dioxide removal on perceptions of climate mitigation in the United States. Energy Res. Social Sci 89, 102656 (2022).
117. Spence, E., Cox, E. & Pidgeon, N. Exploring cross-national public support for the use of enhanced weathering as a land-based carbon dioxide removal strategy. Clim. Change 165, 23 (2021).
118. Buck, H. J. & Palumbo-Compton, A. Soil carbon sequestration as a climate strategy: what do farmers think? Biogeochemistry 161,
59–70 (2022).
119. Carlisle, D. P., Feetham, P. M., Wright, M. J. & Teagle, D. A. H. The public remain uninformed and wary of climate engineering. Clim.
Change 160, 303–322 (2020).
120. Dumbrell, N. P., Kragt, M. E. & Gibson, F. L. What carbon farming activities are farmers likely to adopt? A best–worst scaling survey.
Land use policy 54, 29–37 (2016).
121. .Braun, C., Merk, C., Pönitzsch, G., Rehdanz, K. & Schmidt, U. Public perception of climate engineering and carbon capture andstorage in Germany: survey evidence. Clim. Policy 18, 471–484 (2018).
122. Pidgeon, N. F. & Spence, E. Perceptions of enhanced weathering as a biological negative emissions option. Biol. Lett. 13, 20170024(2017).
123. Jobin, M. & Siegrist, M. Support for the Deployment of Climate Engineering: A Comparison of Ten Different Technologies. Risk
Anal. 40, 1058–1078 (2020).
124. Carlisle, D. P., Feetham, P. M., Wright, M. J. & Teagle, D. A. H. Public engagement with emerging technologies: Does reflective
thinking affect survey responses? Public Underst. Sci. 31, 660–670 (2021).
125. Raimi, K. T. Public perceptions of geoengineering. Curr. Opin. Psychol. 42, 66–70 (2021).
126. Bellamy, R., Lezaun, J. & Palmer, J. Public perceptions of geoengineering research governance: An experimental deliberative approach. Glob. Environ. Change 45, 194–202 (2017).
127. McLaren, D., Parkhill, K. A., Corner, A., Vaughan, N. E. & Pidgeon, N. F. Public conceptions of justice in climate engineering: Evidence from secondary analysis of public deliberation. Glob. Environ. Change 41, 64–73 (2016).
128. McLaren, D., Willis, R., Szerszynski, B., Tyfield, D. & Markusson, N. Attractions of delay: Using deliberative engagement to investigate the political and strategic impacts of greenhouse gas removal technologies. Environment and Planning E: Nature and Space(2021).
129. Simis, M. J., Madden, H., Cacciatore, M. A. & Yeo, S. K. The lure of rationality: Why does the deficit model persist in science communication? Public Underst. Sci. 25, 400–414 (2016).
130. Pidgeon, N. & Rogers-Hayden, T. Opening up nanotechnology dialogue with the publics: Risk communication or ‘upstream engagement’? Health Risk Soc. 9, 191–210 (2007).
131. Gregory, R., Satterfield, T. & Hasell, A. Using decision pathway surveys to inform climate engineering policy choices. PNAS 113,
560–565 (2016).
132. Wenger, A., Stauffacher, M. & Dallo, I. Public perception and acceptance of negative emission technologies – framing effects in
Switzerland. Clim. Change 167, (2021).
133. Bellamy, R., Chilvers, J. & Vaughan, N. E. Deliberative Mapping of options for tackling climate change: Citizens and specialists ‘open
up’ appraisal of geoengineering. Public Underst. Sci. 25, 269–286 (2016).
134. Amelung, D. & Funke, J. Laypeople’s Risky Decisions in the Climate Change Context: Climate Engineering as a Risk-Defusing Strategy? Human and Ecological Risk Assessment 21, 533–559 (2014).
135. Thomas, G., Pidgeon, N. & Roberts, E. Ambivalence, naturalness and normality in public perceptions of carbon capture and storage
in biomass, fossil energy, and industrial applications in the United Kingdom. Energy Res. Social Sci. 46, 1–9 (2018).
136. Merk, C. et al. Public perceptions of climate engineering: Laypersons’ acceptance at different levels of knowledge and intensities ofdeliberation. GAIA - Ecological Perspectives for Science and Society 28, 348–355 (2019).
137. Cody, E. M., Reagan, A. J., Mitchell, L., Dodds, P. S. & Danforth, C. M. Climate Change Sentiment on Twitter: An Unsolicited Public
Opinion Poll. PLoS One 10, e0136092–e0136092 (2015).
138. Mellon, J. & Prosser, C. Twitter and Facebook are Not Representative of the General Population: Political Attitudes and Demographics of Social Media Users. SSRN Electronic Journal (2016) doi:10.2139/ssrn.2791625.
139. Klašnja, M., Barberá, P., Beauchamp, N., Nagler, J. & Tucker, J. A. Measuring Public Opinion with Social Media Data. Oxford Handbooks Online (2017) doi:10.1093/oxfordhb/9780190213299.013.3.
140. Barberá, P. & Rivero, G. Understanding the Political Representativeness of Twitter Users. Soc. Sci. Comput. Rev. 33, 712–729(2014).
141. Twitter-roBERTa-base for Sentiment Analysis. Hugging Face https://huggingface.co/cardiffnlp/twitter-roberta-base-sentiment.
142. Rosenthal, S., Farra, N. & Nakov, P. SemEval-2017 Task 4: Sentiment Analysis in Twitter. (Association for Computational Linguistics,
2017). doi:10.18653/v1/s17-2088.
143. Effrosynidis, D., Karasakalidis, A. I., Sylaios, G. & Arampatzis, A. The climate change Twitter dataset. Expert Syst. Appl. 204, 117541(2022).
144. Bastin, J.-F. et al. The global tree restoration potential. Science 365, 76–79 (2019).
145. Low, S., Baum, C. M. & Sovacool, B. K. Taking it outside: Exploring social opposition to 21 early-stage experiments in radical climate
interventions. Energy Research & Social Science 90, 102594 (2022).
146. Rogelj, J., Geden, O., Cowie, A. & Reisinger, A. Net-zero emissions targets are vague: three ways to fix. Nature 591, 365–368(2021).
147. Fridahl, M. Socio-political prioritization of bioenergy with carbon capture and storage. Energy Policy 104, 89–99 (2017).
148. Honegger, M., Burns, W. & Morrow, D. R. Is carbon dioxide removal ‘mitigation of climate change’? Review of European, Comparative & International Environmental Law 30, 327–335 (2021).
149. Buylova, A., Fridahl, M., Nasiritousi, N. & Reischl, G. Cancel (Out) Emissions? The Envisaged Role of Carbon Dioxide Removal Technologies in Long-Term National Climate Strategies. Frontiers in Climate 3, 675499 (2021).
150. Grassi, G. et al. Critical adjustment of land mitigation pathways for assessing countries’ climate progress. Nat. Clim. Chang. 11, 14(2021).
151. Mace, M. j., Fyson, C. L., Schaeffer, M. & Hare, W. L. Large-Scale Carbon Dioxide Removal to Meet the 1.5°C Limit: Key GovernanceGaps, Challenges and Priority Responses. Global Policy 12, 67–81 (2021).
152. Forsell, N. et al. Assessing the INDCs’ land use, land use change, and forest emission projections. Carbon Balance Manag. 11, 26

105

The State of Carbon Dioxide Removal(2016).
153. Fyson, C. L. & Jeffery, M. L. Ambiguity in the Land Use Component of Mitigation Contributions Toward the Paris Agreement Goals.
Earth’s Future 7, 873–891 (2019).
154. Mohan, A., Geden, O., Fridahl, M., Buck, H. J. & Peters, G. P. UNFCCC must confront the political economy of net-negative emissions. One Earth 4, 1348–1351 (2021).
155. Dubash, N. K. Varieties of climate governance: the emergence and functioning of climate institutions. Env. Polit. 30, 1–25 (2021).
156. Honegger, M., Poralla, M., Michaelowa, A. & Ahonen, H.-M. Who Is Paying for Carbon Dioxide Removal? Designing Policy Instruments for Mobilizing Negative Emissions Technologies. Frontiers in Climate 3, 672996 (2021).
157. Schenuit, F. et al. Carbon Dioxide Removal Policy in the Making: Assessing Developments in 9 OECD Cases. Frontiers in Climate 3,638805 (2021).
158. Köberle, A. C. et al. Can global models provide insights into regional mitigation strategies? A diagnostic model comparison study of
bioenergy in Brazil. Clim. Change 170, 2 (2022).
159. Geden, O. & Schenuit, F. Unconventional Mitigation Carbon Dioxide Removal as a New Approach in EU Climate Policy. https://www.swp-berlin.org/publications/products/research_papers/2020RP08_ClimateMitigation.pdf (2020).
160. Geden, O., Scott, V. & Palmer, J. Integrating carbon dioxide removal into EU climate policy: Prospects for a paradigm shift. Wiley
Interdiscip. Rev. Clim. Change 9, e521 (2018).
161. Meyer-Ohlendorf, N. & Spasova, D. Carbon Dioxide Removals in EU Member States. https://www.ecologic.eu/sites/default/files/
publication/2022/50084-ECF-CDR-report-web.pdf (2022).
162. Meyer-Ohlendorf, N. EU Framework for CO2 Removals – Targets and Commitments. https://www.ecologic.eu/sites/default/files/
publication/2020/60003-removal_ecf_021020_final.pdf (2020).
163. Schenuit, F. & Geden, O. Carbon Dioxide Removal: Climbing up the EU Climate Policy Agenda. https://www.swp-berlin.
org/10.18449/2022WP02/ (2022).
164. UK Woodland Carbon Code: Requirements for voluntary carbon sequestration projects. https://woodlandcarboncode.org.uk/(2022).
165. UK Department for Business, Energy & Industrial Strategy. Greenhouse gas removals (GGR) business models. https://www.gov.uk/
government/consultations/greenhouse-gas-removals-ggr-business-models (2022).
166. UK Department for Business, Energy & Industrial Strategy. Business model for power bioenergy with carbon capture and storage (Power BECCS). https://www.gov.uk/government/consultations/business-model-for-power-bioenergy-with-carbon-capture-and-storage-power-beccs (2022).
167. UK ETS Authority. Developing the UK Emissions Trading Scheme. https://www.gov.uk/government/consultations/developing-theuk-emissions-trading-scheme-uk-ets (2022).
168. Climate Change Committee. 2022 Progress Report to Parliament. https://www.theccc.org.uk/publication/2022-progress-report-to-parliament/ (2022).
169. Government of the United States. Nationally Determined Contribution. https://unfccc.int/sites/default/files/NDC/2022-06/United%20States%20NDC%20April%2021%202021%20Final.pdf (2021).
170. United Nations Framework Convention on Climate Change (UNFCCC). Greenhouse Gas Inventory Data - Time Series. (2022).
171. Larson, E. et al. Net-zero America: potential pathways, infrastructure, and impacts. https://netzeroamerica.princeton.edu/img/
Princeton%20NZA%20FINAL%20REPORT%20SUMMARY%20(29Oct2021).pdf (2021).
172. Government of Brazil. Decreto n. 11.075. https://www.irib.org.br/noticias/detalhes/decreto-n-11-075-de-19-de-maio-de-2022(2022).
173. Silveira, B. H. M., Costa, H. K. de M. & Dos Santos, E. M. The benefit of the RenovaBio Programme for the BECCS market in Brazil.
Rio Oil and Gas Expo and Conference (2022) doi:10.48072/2525-7579.rog.2022.440.
174. Global CCS Institute, and CO2RE. Facilities Database - Global CCS Institute. https://co2re.co/FacilityData. (2022).
175. Ministério da Ciência, T. e. I. Estimativas Anuais de Emissões de Gases de Efeito Estufa no Brasil. https://www.gov.br/mcti/pt-br/
acompanhe-o-mcti/sirene/publicacoes/estimativas-anuais-de-emissoes-gee/arquivos/6a-ed-estimativas-anuais.pdf (2022).
176. Silva Junior, C. H. L. et al. The Brazilian Amazon deforestation rate in 2020 is the greatest of the decade. Nat. Ecol. Evol. 5, 144–145(2021).
177. Soterroni, A. C. et al. Future environmental and agricultural impacts of Brazil’s Forest Code. Environ. Res. Lett. 13, 074021 (2018).
178. Dockendorff, C. et al. Committed to restoring tropical forests: an overview of Brazil’s and Indonesia’s restoration targets and policies. Environ. Res. Lett. 17, 093002 (2022).
179. de Mello Brandão Vinholis, M., Macchione Saes, M. S., Carrer, M. J. & Meirelles de Souza Filho, H. The effect of meso-institutions
on adoption of sustainable agricultural technology: A case study of the Brazilian Low Carbon Agriculture Plan. J. Clean. Prod. 280,
124334 (2021).
180. Embassy of Brazil. Communication from Government of Brazil to UNFCCC. (2010).
181. Government of Brazil. Brazil’s Third Biennial Update Report to the UNFCCC. https://unfccc.int/sites/default/files/resource/2018-02-28_BRA-BUR3_ENG_FINAL.pdf (2019).
182. Embrapa. Carne Carbono Neutro: Um Novo Conceito Para Carne Sustentável Produzida Nos Trópicos. https://ainfo.cnptia.embrapa.br/digital/bitstream/item/203141/1/Carne-carbono-neutro-1.pdf (2015).
183. Macedo, M. C. M., Almeida, R. G. de & Alves, F. V. Low Carbon Brazilian Beef Platform. https://ainfo.cnptia.embrapa.br/digital/bitstream/item/226499/1/LOW-CARBON-BRAZILIAN-BEEF-PLATFORM.pdf (2021).
184. Serviços e Informações do Brasil. PronaSolos Platform allow access to all who produce soil data in Brazil. https://www.gov.br/en/
government-of-brazil/latest-news/2022/pronasolos-platform-allow-access-to-all-who-produce-soil-data-in-brazil (2022).
185. Carton, W., Asiyanbi, A., Beck, S., Buck, H. J. & Lund, J. F. Negative emissions and the long history of carbon removal. Wiley Interdiscip. Rev. Clim. Change 11, (2020).
186. vonHedemann, N., Wurtzebach, Z., Timberlake, T. J., Sinkular, E. & Schultz, C. A. Forest policy and management approaches forcarbon dioxide removal. Interface Focus 10, 20200001 (2020).
187. Brander, M., Ascui, F., Scott, V. & Tett, S. Carbon accounting for negative emissions technologies. Clim. Policy 21, 699–717 (2021).
188. Mission Innovation. Carbon Dioxide Removal Mission Action Plan 2022-26. http://mission-innovation.net/wp-content/uploads/2022/09/Attachment-2-Public-Facing-CDR-Mission-Action-Plan-Sept-2022.pdf (2022).
189. Geden, O. The Paris Agreement and the inherent inconsistency of climate policymaking. Wiley Interdiscip. Rev. Clim. Change 7,
790–797 (2016).
190. Lecocq, F. H. et al. Mitigation and development pathways in the near- to mid-term. in IPCC, 2022: Climate Change 2022: Mitigationof Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate

106

The State of Carbon Dioxide Removal
Change (eds. Shukla, P. R. et al.) (Cambridge University Press, 2022).
191. Grassi, G. et al. Carbon fluxes from land 2000–2020: bringing clarity to countries’ reporting. Earth System Science Data 14,4643–4666 (2022).
192. Gidden, M. et al. Policy guidance and pitfalls aligning IPCC scenarios to national land emissions inventories. Earth and Space Science
Open Archive (2022) doi:10.1002/essoar.10512676.2.
193. Powis R.C.M., Smith S., Minx J., Gasser, T. Quantifying global carbon dioxide removal deployment. In preparation.
194. Berkeley Carbon Trading Project. Voluntary Registry Offsets Database. https://gspp.berkeley.edu/faculty-and-impact/centers/
cepp/projects/berkeley-carbon-trading-project/offsets-database.
195. Verra. Verra Registry. Verra (2020) https://verra.org/registry-system/.
196. Gold Standard. Impact Registry. (2022) https://www.goldstandard.org/resources/impact-registry.
197. American Carbon Registry. Public Registry. Public Registry (2022) https://americancarbonregistry.org/how-it-works/registry-reports.
198. Climate Action Reserve. Public Registry. (2022) https://thereserve2.apx.com/mymodule/mypage.asp.
199. Stripe Climate. Carbon Removal Portfolio. https://stripe.com/en-ca/climate.
200. Microsoft Sustainability. Microsoft Carbon Dioxide Removal Program. https://www.microsoft.com/en-us/corporate-responsibility/
sustainability/carbon-removal-program.
201. Thirdway. Carbon Capture Projects Map. (2022) https://www.thirdway.org/graphic/carbon-capture-projects-map.
202. Global CCS Institute. CCS Facilities Database. (2018) https://www.globalccsinstitute.com/co2re/.
203. Massachusets Institute for Technology. Carbon Capture and Sequestration Technologies. (2017).
204. Center for International Forestry Research (CIFOR). International Database on REDD+ projects and programmes. (2022).
205. Center for International Forestry Research (CIFOR). Global database of REDD+ and other forest carbon projects. (2022).
206. Forest Trends. Mapping Ecosystem Markets Database. (2018).
207. United Nations Framework Convention on Climate Change. Clean Development Mechanism Project Activities Database. (2022).
208. Doelman, J. C. et al. Afforestation for climate change mitigation: Potentials, risks and trade-offs. Glob. Chang. Biol. 26, 1576–1591(2020).
209. Butarbutar, T., Köhl, M. & Neupane, P. R. Harvested wood products and REDD+: looking beyond the forest border. Carbon BalanceManag. 11, 4 (2016).
210. Harmon, M. E. et al. Release of coarse woody detritus-related carbon: a synthesis across forest biomes. Carbon Balance Manag. 15,
1 (2020).
211. Way, R., Ives, M., Mealy, P. & Doyne Farmer, J. Empirically grounded technology forecasts and the energy transition. Joule 6,
2057–2082 (2022).
212. United Nations. Paris Agreement. https://unfccc.int/sites/default/files/english_paris_agreement.pdf (2015).
213. Schleussner, C.-F. et al. Science and policy characteristics of the Paris Agreement temperature goal. Nat. Clim. Chang. 6, 827–835(2016).
214. Rajamani, L. & Werksman, J. The legal character and operational relevance of the Paris Agreement’s temperature goal. Philos. Trans.
A Math. Phys. Eng. Sci. 376, (2018).
215. United Nations Framework Convention on Climate Change (UNFCCC). Report of the Conference of the Parties on its sixteenth session, held in Cancun from 29 November to 10 December 2010. Addendum. Part two: Action taken by the Conference of the Parties
at its sixteenth session. https://unfccc.int/documents/6527 (2011).
216. O’Neill, B. C. et al. The roads ahead: Narratives for shared socioeconomic pathways describing world futures in the 21st century.
Glob. Environ. Change 42, 169–180 (2017).
217. IAM Consortium. The common Integrated Assessment Model (IAM) documentation. https://www.iamcdocumentation.eu/index.
php/IAMC_wiki.
218. Emmerling, J. et al. The role of the discount rate for emission pathways and negative emissions. Environ. Res. Lett. 14, 104008(2019).
219. van Soest, H. L. et al. Global roll-out of comprehensive policy measures may aid in bridging emissions gap. Nat. Commun. 12, 6419
(2021).
220. Byers, E. et al. AR6 Scenarios Database. (2022) doi:10.5281/zenodo.5886912.
221. Guivarch, C., Kriegler, E. & Portugal Pereira, J. Annex III: Scenarios and modelling methods. in Climate Change 2022: Mitigationof Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate
Change (eds. Shukla, P. R. et al.) (Cambridge University Press, 2021).
222. Gasser, T. et al. Historical CO2 emissions from land use and land cover change and their uncertainty. Biogeosciences 17, 4075–4101(2020).
223. Schleussner, C.-F., Ganti, G., Rogelj, J. & Gidden, M. J. An emission pathway classification reflecting the Paris Agreement climate
objectives. Communications Earth & Environment 3, 1–11 (2022).
224. Luderer, G. et al. Residual fossil CO2 emissions in 1.5–2 °C pathways. Nat. Clim. Chang. 8, 626–633 (2018).
225. Realmonte, G. et al. An inter-model assessment of the role of direct air capture in deep mitigation pathways. Nat. Commun. 10,3277 (2019).
226. International Energy Agency (IEA). Tracking Clean Energy Progress. https://www.iea.org/topics/tracking-clean-energy-progress(2022).
227. United Nations Environment Programme (UNEP). Trends in global emissions, new pledges for 2030 and G20 status and outlook. in
Emissions Gap Report 2021: The Heat Is On – A World of Climate Promises Not Yet Delivered 15 (UNEP, 2021).
228. United Nations Environment Programme (UNEP). Global emissions trends and G20 status and outlook. in Emissions Gap Report2020 (UNEP, 2020).
229. Friedlingstein, P. et al. Global Carbon Budget 2021. Earth System Science Data 14, 1917–2005 (2022).
230. Grassi, G. et al. Mapping land-use fluxes for 2001–2020 from global models to national inventories. (2022).
231. Intergovernmental Panel on Climate Change (IPCC). 2006 IPCC Guidelines for National Greenhouse Gas Inventories. https://www.
ipcc-nggip.iges.or.jp/public/2006gl/index.html (2006).
232. Friedlingstein, P. et al. Global carbon budget 2022. Earth Syst. Sci. Data 14, 4811–4900 (2022).
233. Gasser, T., Ciais, P. & Lewis, S. L. How the Glasgow Declaration on Forests can help keep alive the 1.5 °C target. Proc. Natl. Acad.
Sci. U. S. A. 119, e2200519119 (2022).
234. Günther, A., Gütschow, J. & Jeffery, M. L. NDCmitiQ v1.0.0: a tool to quantify and analyse greenhouse gas mitigation targets. Geosci. Model Dev. 14, 5695–5730 (2021).

107

The State of Carbon Dioxide Removal
235. Grassi, G. et al. The key role of forests in meeting climate targets requires science for credible mitigation. Nat. Clim. Chang. 7,
220–226 (2017).
236. Smith, H. B., Vaughan, N. E. & Forster, J. Long-term national climate strategies bet on forests and soils to reach net-zero. Commun
Earth Environ 3, 305 (2022).
237. International Boreal Forest Research Association (IBFRA). 2021-11 Sustainable boreal forest management – challenges
and opportunities for climate change mitigation. https://www.skogsstyrelsen.se/globalassets/om-oss/rapporter/rapporter-2021202020192018/rapport-2021-11-sustainable-boreal-forest-management-challenges-and-opportunities-for-climate-change-mitigation-002.pdf (2021).
238. Bento, N., Wilson, C. & Anadon, L. D. Time to get ready: Conceptualizing the temporal and spatial dynamics of formative phases forenergy technologies. Energy Policy 119, 282–293 (2018).
239. Grubler, A. et al. A low energy demand scenario for meeting the 1.5oC target and sustainable development goals without negativeemissions technologies. Nature Energy 3, 515–527 (2018).
240. Jackson, R. B. et al. Global fossil carbon emissions rebound near pre-COVID-19 levels. Environ. Res. Lett. 17, 031001 (2022).
241. Davis, S. J. et al. Emissions rebound from the COVID-19 pandemic. Nat. Clim. Chang. 12, 412–414 (2022).
242. van Vuuren, D. P. et al. Alternative pathways to the 1.5 °C target reduce the need for negative emission technologies. Nat. Clim.
Chang. 8, 391–397 (2018).
243. Roe, S. et al. Contribution of the land sector to a 1.5 °C world. Nat. Clim. Chang. 9, 817–828 (2019).
244. Dooley K. et al. The Land Gap Report 2022. https://www.landgap.org/ (2022).
245. Tong, D., Zhang, Q., Zheng, Y. et al. Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target.
Nature 572, 373–377 (2019). https://doi.org/10.1038/s41586-019-1364-3
246. Dhakal, S., et al. Emissions Trends and Drivers. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contributionof Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (eds. Shukla, P. R. et al.)(Cambridge University Press, 2022).
247. Trout, K. et al. Existing fossil fuel extraction would warm the world beyond 1.5°C. Environ. Res. Lett. 17, 064010 (2022)
248. Hepburn, C. et al. The technological and economic prospects for CO2 utilization and removal. Nature 575, 87–97 (2019).

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