Conference PaperPDF Available

Qualitative comparative assessment of Negative Emission Technologies

Authors:

Abstract

An assessment framework including a set of impact categories, criteria, and indicators was created in order to analyse a broad set of factors affecting the feasibility of Negative Emission Technologies (NETs). Each criterion was addressed in terms of the best available literature. The analysis has shown clearly that uncertainties surrounding NETs are significant, publications use a variety of metrics and assumptions which complicates comparison between studies and that the feasibility of individual NETs varies significantly depending on national or regional context. Further top-down assessments of NETs will do little to satisfy the need to understand the difference between the technical potentials and practical feasibility of individual NETs. Regional bottom-up studies are needed, focusing on the potential to deliver on sustainable development objectives to better understand potentials in real-world conditions.
Selection and peer-review under responsibility of the scientific committee of the 12th Int. Conf. on Applied Energy (ICAE2020).
Copyright © 2020 ICAE
International Conference on Applied Energy 2020
Dec. 1 - Dec. 10, 2020, Bangkok / Virtual
Paper ID: 704
Qualitative comparative assessment of Negative Emission Technologies
Kenneth Möllersten1,2*, Raza Naqvi 1,3, Jinyue Yan1
1 Future energy center, Mälardalen University, Box 883, 721 23 Västerås, Sweden
2 IVL Swedish Environmental Research Institute, Box 210 60, 100 31 Stockholm, Sweden
3 Karlstad University, 651 88 Karlstad, Sweden
ABSTRACT
An assessment framework including a set of impact
categories, criteria, and indicators was created in order
to analyse a broad set of factors affecting the feasibility
of Negative Emission Technologies (NETs). Each criterion
was addressed in terms of the best available literature.
The analysis has shown clearly that uncertainties
surrounding NETs are significant, publications use a
variety of metrics and assumptions which complicates
comparison between studies and that the feasibility of
individual NETs varies significantly depending on national
or regional context. Further top-down assessments of
NETs will do little to satisfy the need to understand the
difference between the technical potentials and practical
feasibility of individual NETs. Regional bottom-up studies
are needed, focusing on the potential to deliver on
sustainable development objectives to better
understand potentials in real-world conditions.
Keywords: Negative emissions, carbon dioxide removal,
comparative technological assessment
NOMENCLATURE
Abbreviations
AM
Accelerated Mineralization
A/R
Afforestation and Reforestation
BC
Biochar as soil additive
BECCS
Bioenergy with Carbon Capture and
Storage
CDR
Carbon Dioxide Removal
CO2
Carbon Dioxide
DACCS
Direct Air Carbon Capture and
Storage
EW
Enhanced Weathering
GHG
Greenhouse Gas
NET
Negative Emission Technology
OF
Ocean Fertilization
SCS
Soil Carbon Sequestration
WR
Wetland Restoration
Symbols
a
year
t
ton
1. INTRODUCTION
The objective of this work has been to contribute to
a more comprehensive understanding of Negative
Emission Technologies (NETs) including costs, benefits
and risks in order to enable a more comprehensive
assessment of their potentials to contribute to climate
change mitigation.
The term NETs refers to a set of technologies for
actively removing carbon dioxide (CO2) and/or other
greenhouse gases (GHG) from the atmosphere. Should
the scale of NETs eventually exceed residual emissions of
GHGs, the increase in atmospheric GHG levels could even
be reversed as first put forward by Obersteiner et al. [1].
The IPCC [2] presents scenarios that illustrate how
warming could be limited to 1.5°C. Future scenarios,
however, show great difficulty of reaching the long-term
temperature targets only by reducing emissions. This is
due to the lack of mitigation action so far as well as the
inadequacy of currently planned mitigation measures.
2
Copyright © 2020 ICAE
Consequently, the scenarios also incorporate significant
contributions from NETs that remove CO2 from the
atmosphere. In principle Carbon Dioxide Removal (CDR)
has two functions: (i) to enable a balance between global
carbon emissions and removals to be reached sooner
and (ii) to compensate for an over-spent carbon budget.
Accumulated CDR deployment over the 21st century
is substantial in most of the scenarios, and deployment
levels cover a wide range, on the order of 1001000 Gt
CO2 in 1.5°C pathways with no or limited overshoot. As
a point of reference, the global energy-related CO2
emissions in the year 2019 reached approximately 33 Gt
[3]. Even higher CDR deployment appears in high
overshoot pathways while the low end is found for
emission pathways with no or limited overshoot. These
are pathways with very low energy demand facilitating
the rapid phase-out of fossil fuels and process emissions
and/or pathways with rapid shifts to sustainable food
consumption freeing up sufficient land areas for
afforestation/reforestation.
Analysis of the readiness, feasibility and realistic
potential of NETs is key for their implementation, in
order to address issues of climate change. This paper
assesses the major classes of NETs, including (i)
bioenergy with carbon capture and storage (BECCS); (ii)
direct air capture and storage (DACCS); (iii) large-scale
afforestation and reforestation (A/R) (also considering
the improved forest management); (iv) soil carbon
sequestration (SCS); (v) Biochar as soil additive (BC); (vi)
Enhanced Weathering (EW); (vii) Accelerated
Mineralization (AM); (viii) Wetland Restoration, and (iix)
Ocean Fertilization (OF) and identifies priority NETs on
the basis of a number of performance indicators to be
selected for further analysis in the continuation of this
research initiative.
2. MATERIALS AND METHODS
In order to systematically analyze a broad set of
factors affecting the feasibility of NETs, the following
steps were taken (i) technologies were categorized and
(ii) an assessment model was developed. Identification
and categorization of proposed NETs (see section 1) was
carried out based on a review of relevant literature. The
detailed assessment model, including as set of impact
categories, criteria, and indicators is presented in Table 1.
Each criterion is addressed in terms of the best available
literature.
Category
Criterion
1
Technical and
economic
feasibility
Technological
readiness
Economic
viability
Permanence
2
Global climate
change
mitigation
potentials
CDR potential
Interaction
with other
emissions
reductions
mitigation
potentials.
3
Social and
socio-
economic
implications
Strain or added
resilience for
local/regional
energy
systems
Health
implications
Jobs and local
revenue
generation
Implications
for other
sectors
4
Environmental
impacts
Local
temperature
impact of
albedo change
Air quality
Surface and
ground water
quality and
availability
Biodiversity
5
Political
feasibility
Expected
societal
acceptance or
acceptability
3
Copyright © 2020 ICAE
Institutional
challenges and
opportunities
Table 1 Multi-criteria assessment framework.
3. THEORY
There is an increasing scientific basis to make the
argument that CDR planning will have to consider a
broad array of factors including socio-economic and
environmental, technical barriers and lead-times, market
barriers, interaction with other policy areas, political and
governance uncertainties, and ethics to name a few [4]
[5] [6]. In this work we have applied an interdisciplinary
framework for comparing NETs using the set of
categories and criteria introduced in section 2. This
framework includes a broader set of criteria than
representative previous assessments [7] [8] [9].
The assessment model aims to provide an initial
factual basis concerning NETs for a coherent
interdisciplinary discussion in selecting strategies best
suited to specific national or regional contexts.
4. RESULTS AND CONCLUSION
The outcome of applying the multiple criteria to the
selected NETs is presented in Table 2. The presentation is
simplified due to space constraints. A comprehensive
representation of the results can be found in [10].
The literature review carried out for this work has
shown clearly that uncertainties surrounding NETs are
significant. Moreover, publications use a variety of
metrics and assumptions when analyzing individual
parameters (such as cost etc.) which complicates
comparison between studies. It has also become clear
that the feasibility of individual NETs varies significantly
depending on national or regional context.
Further top-down assessments of NETs will do little
to satisfy the need to understand the difference between
the technical potentials and practical feasibility of
individual NETs. Instead there is a need for regional
bottom-up studies, focusing on the potential to deliver
on sustainable development objectives to better
understand potentials in real-world conditions. This
applies particularly to regions attributed with high
potentials for NETs.
ACKNOWLEDGEMENT
This project has received funding from the Swedish
Energy Agency. Helpful inputs to the design of the
research work by Adrián Lauer, Axel Michaelowa,
Hailong Li, Matthias Honegger, and Sonja Butzengeiger
are gratefully acknowledged.
REFERENCE
[1] Obersteiner M. Azar C. Kauppi P. Möllersten K. Moreira J.
Nilsson S. Read P. Riahi K. Schlamadinger B. Yamagata Y.
Yan J., van Ypersele J-P. Managing climate risk. Science
2001;294:786-87.
[2] IPCC. Global warming of 1,5 °C. Intergovernmental Panel
on Climate Change; 2018.
[3] International Energy Agency. Global CO2 emissions in
2019. 2020. [Online]. Available:
https://www.iea.org/articles/global-co2-emissions-in-2019.
[Accessed 10 11 2020].
[4] Lenzi D., Lamb W., Hilaire J. Weigh the ethics of plans to
mop up carbon dioxide. Nature 2018;561:303-05.
[5] Cox E., Edwards N. Beyond carbon pricing: policy levers
for negative emission technologies. Climate policy
2019;19:1144-56.
[6] Fuss S., Canadell J., Ciais P., Jackson R., Jones C.,
Lyngfeldt A., Peters G., van Vuuren D. Moving toward net-zero
emissions requires new alliances for carbon dioxide removal.
One earth 2020:145-49.
[7] European Academies Science Advisory Council. Negative
emission technologies: What role in meeting Paris Agreement
targets?; 2018.
[8] Fuss S. Lamb W. Callaghan M., Hilaire J., Creutzig F.,
Amann P., Beringer P., de Oliviera Garcia W., Hartmann J.,
Khanna T., Luderer G., Nemet G., Rogelj J., Smith P., Vicente
Vicente J., Wilcox J., del Mar Zamora Dominguez M., Minx J.
Negative Emissions -Part 2: Costs, potentials and side-effects.
Environmental Research Letters 2018;13.
[9] Smith P., Adams J., Beerling D., Beringer T., Calvin K.,
Fuss S., Griscom B., Hagemann N., Kammann C., Kraxner F.,
Minx J., Popp A., Renforth B., Vicente J., Kesstra S. Impacts
of land-based greenhouse gas removal options on ecosystem
services and the united nations sustainable development goals.
Annu. Rev. Environ. Resour 2019;44:1-32.
[10] Möllersten K., Naqvi R. Qualitative assessment of classes
of negative emission technologies (NETs). Mälardalen
university, Västerås; 2020.
4
Copyright © 2020 ICAE
Technology
readiness
level
Economic
viability
(USD/tCO2)
Perma-
nence
Global
potential
CO2
removal
(GtCO2/a)
Social and socio-
economic
implications
Environmental
impact
Political feasibility
Biochar
3 - 7
Low to
moderate
cost
40-130
Reliable but
depending
on char
quality and
environ-
mental
conditions
2-4,5
May be
partly
offset by
albedo
decrease
(-) Large land
requirement
biomass production
(+) Improved
agriculture yields,
job creation, Co-
generates energy
services
(-) Impact on
biodiversity if
monoculture
plantations
Experience from
early pilot activities
indicates high
acceptance
Bioenergy with carbon capture and storage
Bioenergy 6
- 9
CCS
4 - 7
Highly case
specific.
20-100+
Highly
stable
5
May be
partly
offset by
albedo
decrease
on
northern
latitudes
(-) Large land
requirement for
(+) Job creation, Co-
generates energy
services
(-) Impact on
biodiversity if
monoculture
plantations
Long-term
monitoring to
prevent CO2 leakage
requires well-
developed
technological and
regulatory capacity.
Public acceptance
uncertain.
Direct air carbon capture and storage
Supported
amine 3-5
Na or Ca
scrubbers
4-6
40-300
165-600
Highly
stable
10+
(-) High energy
demand
(+) Job creation
High CO2 penalty
if fossil-based
energy supply
Same as BECCS
Afforestation/reforestation
A/R 7,
Forest
mgmt. 9.
Low-
moderate
cost
0-100
Sensitive in
case of
policy
changes,
lack of
enforce-
ment, or
natural
disasters
3-3.6
May be
partly
offset by
albedo
decrease
on
northern
latitudes
(-) Large land
requirement
(+) Potential
ecosystem services,
job creation,
Generates biomass
available for energy
purposes
(-) Impact on
biodiversity if
monoculture
plantations
Acceptance
challenge due to land
requirement and
reversibility.
Requires methods for
socially and culturally
responsible
implementation and
governance to
monitor and
maintain carbon
stock
Wetland restoration
5 - 7
Low-
moderate
cost.
Sensitive to
land use
policies and
1.7
(-) Large land
requirement (+) Job
creation
(+) Multiple
ecosystem
services
Politically feasible in
many cases
5
Copyright © 2020 ICAE
Unclear
how much
is CO2
removal vs
avoided
emissions
climate
change
Soil carbon sequestration
5-7
Low-
moderate
cost
0-100
Highly
sensitive.
Reversible
upon
changes in
soil
treatment
practices
2.3-5
Partly
offset by
Trace GHG
(N2O)
emissions
(+) Potential for
synergies with
agricultural
production
Need for
addition of N
and P to
maintain Soil
organic matter
Acceptance as
Negatvie Emission
Technology is a
callenge due to
reversibility.
Enhanced weathering
3-5
Low-
moderate
cost 20-40
(50-200)
Highly
stable
1-5
(-) Human health
risks associated
with fine particles.
(+) Improved
agricultural yields,
job creation
Air pollution,
extensive
mining and
extraction,
ground/water
pollution
Acceptance
challenging due to
extensive mining and
transport
requirement.
Human health issues
need to be addressed
Ocean fertilisation
2 - 5
Uncertain
Uncertain
Unknown
(-) Potential impact
on fisheries
Potential
disruption of
entire
ecosystems
Acceptance a
substantial
challenge.
Regulatory
uncertainty
Accelerated mineralisation
4-7
20 -130
Highly
stable
0.5-1
(-)Energy required
for pre-treatment
of feedstock
(+) Job creation
Large mineral
requirement
(large-scale
mining)
Low-medium
acceptability
Table 2 Characterisation of NETs based on multi-criteria assessment framework.
... Considering the current state of the art, HyBECCS approaches can be combined with three different storage options: (1) mineral carbonation, also known as mineralization or enhanced weathering, (2) geological underground storage, for instance in depleted oil/gas reservoirs or saline aquifers, and (3) in long-term CCU application, such as in the built environment in low-carbon concrete (Azapagic et al., 2018, p. 21;IPCC, p. 39). Mineralized carbon is safely stored in the long term, whereas geological underground storage is estimated to be safe for over 1000 years when best practice is applied (IPCC, 2005b; Möllersten et al., 2020;Poralla et al., 2021, p. 21). The third storage option for biogenic CO 2 from HyBECCS, long-term CCU applications, has a higher risk of reversals, insecurity concerning the time horizon of storage, and further challenges such as monitoring the permanence due to the dispersed places of use (Otto et al., 2017). ...
... Due to missing data from real HyBECCS plants, the LCNE for HyBECCS is only an assumption for illustration purposes and not based on real values. The values of the alternatives are based on actual data from Poralla et al. (2021) and Möllersten et al. (2020). For HyBECCS, the purple bar represents the internal LCNE before GHG internalization. ...
... Here, the LCNE of negative emissions from an exemplary HyBECCS plant is compared to the costs of BECCS and DACCS. For both alternatives, the striped bars represent cost ranges gathered from studies (Möllersten et al., 2020;Poralla et al., 2021). As long as no GHG internalization for process emissions is undertaken for DACCS and BECCS, those cost ranges represent the internal LCNE. ...
Article
Full-text available
In order to achieve greenhouse gas neutrality, hydrogen generated from renewable sources will play an important role. Additionally, as underlined in the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), new technologies to remove greenhouse gases from the atmosphere are required on a large scale. A novel concept for hydrogen production with net negative emissions referred to as HyBECCS (Hydrogen Bioenergy with Carbon Capture and Storage) combines these two purposes in one technological approach. The HyBECCS concept combines biohydrogen production from biomass with the capture and storage of biogenic carbon dioxide. Various technology combinations of HyBECCS processes are possible, whose ecological effects and economic viability need to be analyzed in order to provide a basis for comparison and decision‐making. This paper presents fundamentals for the techno‐economic and environmental evaluation of HyBECCS approaches. Transferable frameworks on system boundaries as well as emission, cost and revenue streams are defined and specifics for the application of existing assessment methods are elaborated. In addition, pecularities concerning the HyBECCS approach with respect to political regulatory measures and interrelationships between economics and ecology are outlined. Based on these considerations, two key performance indicators (KPIs) are established, referred to as levelized cost of carbon‐negative hydrogen (LCCNH) and of negative emissions (LCNE). Both KPIs allow deciding whether a specific HyBECCS project is economically viable and allows its comparison with different hydrogen, energy provision or negative emission technologies (NETs).
... A key feature -and challenge -of CDR is that the storage of CO 2 needs to be 'durable' (overnmental Panel on Cli, 2018, p. 544) or permanent. The innate permanence of CO 2 stored in biological systems (soil-and plant biomass or biochar) is much lower than the innate permanence of CO 2 stored deep underground and/or in mineralized form (Möllersten and Naqvi, 2020). While permanence may overall be achieved in both cases through suitable measures, permanence of chemically stable compositions is dramatically higher. ...
... Projections for long-term costs of DACCS operation vary greatly with a lower limit at around USD 40/tCO 2 and the upper limit at around USD 600/tCO 2 (Möllersten and Naqvi, 2020), or even between USD 20/tCO 2 and USD 1000/tCO 2 (overnmental Panel on Cli, 2018). DACCS technology providers envisage long-term operating costs to stabilize on the order of 100 USD/tCO 2 . ...
Article
Full-text available
Carbon dioxide removal (CDR) poses a significant and complex public policy challenge in the long-term. Presently treated as a marginal aspect of climate policy, addressing CDR as a public good is quickly becoming essential for limiting warming to well below 2 or 1.5°C by achieving net-zero emissions in time – including by mobilization of public and private finance. In this policy and practice review, we develop six functions jointly needed for policy mixes mobilizing CDR in a manner compatible with the Paris Agreement's objectives. We discuss the emerging CDR financing efforts in light of these functions, and we chart a path to a meaningful long-term structuring of policies and financing instruments. CDR characteristics point to the need for up-front capital, continuous funding for scaling, and long-term operating funding streams, as well as differentiation based on permanence of storage and should influence the design of policy instruments. Transparency and early public deliberation are essential for charting a politically stable course of action on CDR, while specific policy designs are being developed in a way that ensures effectiveness, prevents rent-seeking at public expense, and allows for iterative course corrections. We propose a stepwise approach whereby various CDR approaches initially need differentiated treatment based on their differing maturity and cost through R&D pilot activity subsidies. In the longer term, CDR increasingly ought to be funded through mitigation results-oriented financing and included in broader policy instruments. We conclude that CDR needs to become a regularly-provided public service like public waste management has become over the last century.
... Biochar as soil additive, may potentially be scaled at reasonably fast rates in developed countries. However, biochar is, in contrast to BECCS, also an appropriate technology in a developing country context [32]. Rapid scale-up in developing countries in developing countries would, however, have to build on high adoption rates of biochar practices by smallholders, which is likely to be challenging, as noted in section 4.3.1. ...
Conference Paper
Full-text available
The paper presents a review of technology readiness, costs, impacts, and practical limitations of the Carbon Dioxide Removal (CDR) methods Biochar as soil additive and Bioenergy with Carbon Capture and Storage (BECCS). TRLs, costs, practical limitations, and impacts of the considered CDR methods vary greatly depending on contextually appropriate technology choices and assumptions. The analysis shows that the CDR methods should be considered as classes of CDR methods with considerable variation rather than as two homogenous CDR methods.
... The current report builds on previous work in which an assessment of the major classes of NETs was carried out (Möllersten, et al., 2020a;Möllersten, et al., 2020b), including (i) bioenergy with carbon capture and storage (BECCS); (ii) direct air capture and storage (DACCS); (iii) large-scale afforestation and reforestation; (iv) soil carbon sequestration; (v) Biochar as soil additive; (vi) Enhanced Weathering; (vii) Accelerated Mineralization; (viii) Ocean fertilization and priority NETs were selected for further analysis on the basis of a number of performance indicators. A comprehensive literature review was carried out in accordance with the broad NET categories identified as outlined above resulting in a substantial amount of data on all identified NET categories. ...
Technical Report
Negative emission technologies (NET) can be used to remove greenhouse gases (GHG), primarily CO2, from the atmosphere and store them durably. However, they also lead to a number of other impacts, both positive and negative. This report maps environmental impacts of the two biomass-based NETs (i) bioenergy with CO2 capture and storage (BECCS) and (ii) biochar as soil additive. Impacts relevant for the enhanced greenhouse effect and other environmental impacts of the two NETs are mapped along their respective value chains. Each impact is given a brief description of the scientific background and, in addition, categorized to give an idea of how reliably it can be estimated, whether the impact is positive or negative, and if it is relevant for climate change. The analysis shows that, although both studied NETs contribute with carbon withdrawal on a net basis, impacts along the value chain of both biochar and BECCS contribute positively and negatively to the climate and other environmental aspects. Out of the two, biochar is more complex to assess, both with respect to durable carbon removal and other environmental aspects.
... The current report builds on previous work in which an assessment of the major classes of NETs was carried out (Möllersten, et al., 2020a;Möllersten, et al., 2020b), including (i) bioenergy with carbon capture and storage (BECCS); (ii) direct air capture and storage (DACCS); (iii) large-scale afforestation and reforestation; (iv) soil carbon sequestration; ...
Technical Report
Full-text available
In view of the magnitude of assumed future deployment of Negative Emission Technologies (NETs), technical, socio-political and economic challenges will arise and may impose serious constraints. Analysis of the readiness, feasibility and realistic potential of NETs is therefore key for improving the understanding of a realistic potential for their implementation. The current report builds on previous work in which an assessment of the major classes of NETs was carried out , including (i) bioenergy with carbon capture and storage (BECCS); (ii) direct air capture and storage (DACCS); (iii) large-scale afforestation and reforestation; (iv) soil carbon sequestration; (v) Biochar as soil additive; (vi) Enhanced Weathering; (vii) Accelerated Mineralization; (viii) Ocean fertilization and priority NETs were selected for further analysis on the basis of a number of performance indicators. A comprehensive literature review was carried out in accordance with the broad NET categories identified as outlined above resulting in a substantial amount of data on all identified NET categories. On the basis of a qualitative assessment, Accelerated Mineralization (AM), BECCS; Biochar as soil additive; DACCS; and Wetland Restoration (WR) were shortlisted for further analysis. This report presents an in-depth technology readiness and cost assessment and an analysis of practical deployment barriers for the selected NETs along with an analysis of related knowledge gaps and research needs. The report is divided into sections in accordance with the selected NETs and concluded with a summary and conclusions.
Article
Full-text available
This paper explores policies for Negative Emissions Technologies (NETs), in an attempt to move beyond the supply-side focus of the majority of NETs research, as well as the current dominance of carbon pricing as the main NETs policy proposal. The paper identifies a number of existing policies from four key areas – energy/transport, agriculture, sub-soil, and oceans – which will have an impact on three NETs: Bioenergy with Carbon Capture and Storage (BECCS), Direct Air Capture (DAC), and terrestrial Enhanced Rock Weathering (ERW). We propose that non-climate co-benefits may be valuable in terms of the policy ‘demand pull’ for NETs; in particular, we find that ERW may provide multiple co-benefits which can be mandated through existing policy structures. However, interaction with numerous policy areas may also create barriers, particularly where there is tension between the priorities of different government departments. On the basis of existing and analogous policies from a range of geographical contexts and scales, this paper proposes four options for NETs policy that could be reasonably implemented in the near-term. We also argue that ERW demonstrates the importance of scale and framing, because the policy environment depends on whether it is framed as a soil amendment at local scales or as a climate stabilization technique at international scale. Key policy insights • Co-benefits may assist the ‘demand pull’ for novel technologies by providing multiple policy angles for incentivisation rather than relying on a ‘fix-all’ policy such as a high carbon price. • DAC with storage might be overly reliant on a high carbon price, because it only provides one core benefit – that of atmospheric carbon reduction. • ERW may provide multiple co-benefits which can be mandated through existing policy structures, but should focus on using waste rock rather than mining virgin material. • We propose four near-term options for NETs policy: funding for small-scale BECCS demonstration and an international biomass certification mechanism; small-scale loans for ERW on farms and promotion of locally-sourced rock residues; amendment of fertilizer subsidy schemes to include silicate rock; and a clearer framework for licensing sub-soil access for CO2 storage.
Article
Full-text available
The most recent IPCC assessment has shown an important role for negative emissions technologies (NETs) in limiting global warming to 2 °C cost-effectively. However, a bottom-up, systematic, reproducible, and transparent literature assessment of the different options to remove CO2 from the atmosphere is currently missing. In part 1 of this three-part review on NETs, we assemble a comprehensive set of the relevant literature so far published, focusing on seven technologies: bioenergy with carbon capture and storage (BECCS), afforestation and reforestation, direct air carbon capture and storage (DACCS), enhanced weathering, ocean fertilisation, biochar, and soil carbon sequestration. In this part, part 2 of the review, we present estimates of costs, potentials, and side-effects for these technologies, and qualify them with the authors' assessment. Part 3 reviews the innovation and scaling challenges that must be addressed to realise NETs deployment as a viable climate mitigation strategy. Based on a systematic review of the literature, our best estimates for sustainable global NET potentials in 2050 are 0.5–3.6 GtCO2 yr⁻¹ for afforestation and reforestation, 0.5–5 GtCO2 yr⁻¹ for BECCS, 0.5–2 GtCO2 yr⁻¹ for biochar, 2–4 GtCO2 yr⁻¹ for enhanced weathering, 0.5–5 GtCO2 yr⁻¹ for DACCS, and up to 5 GtCO2 yr⁻¹ for soil carbon sequestration. Costs vary widely across the technologies, as do their permanency and cumulative potentials beyond 2050. It is unlikely that a single NET will be able to sustainably meet the rates of carbon uptake described in integrated assessment pathways consistent with 1.5 °C of global warming.
Article
Full-text available
We conclude that a system of climate risk management is practicable and necessary. Increasing deployment of sustainable bioenergy with carbon removal and sequestration, together with structural shift toward low carbon-intensive fuels, will turn out to be instrumental for such a risk-limiting regime and might offer ancillary benefits for sustainable development.
Article
The 1.5°C target will require removing at least some of the carbon dioxide (CO2) previously emitted. Knowledge on how this can be done has been increasing, though barriers remain concerning governance, policy, and acceptability. For the 26th session of the Conference of the Parties (COP26) to move beyond an academic debate on CO2 removal (CDR), a broader alliance of research and policy communities, industry, and the public is needed.
Global warming of 1,5 °C. Intergovernmental Panel on Climate Change
  • Ipcc
IPCC. Global warming of 1,5 °C. Intergovernmental Panel on Climate Change; 2018.
Weigh the ethics of plans to mop up carbon dioxide
  • D Lenzi
  • W Lamb
  • J Hilaire
Lenzi D., Lamb W., Hilaire J. Weigh the ethics of plans to mop up carbon dioxide. Nature 2018;561:303-05.
Impacts of land-based greenhouse gas removal options on ecosystem services and the united nations sustainable development goals
  • P Smith
  • J Adams
  • D Beerling
  • T Beringer
  • K Calvin
  • S Fuss
  • B Griscom
  • N Hagemann
  • C Kammann
  • F Kraxner
  • J Minx
  • A Popp
  • B Renforth
  • J Vicente
  • S Kesstra
Smith P., Adams J., Beerling D., Beringer T., Calvin K., Fuss S., Griscom B., Hagemann N., Kammann C., Kraxner F., Minx J., Popp A., Renforth B., Vicente J., Kesstra S. Impacts of land-based greenhouse gas removal options on ecosystem services and the united nations sustainable development goals. Annu. Rev. Environ. Resour 2019;44:1-32.