Focus on negative emissions

SSRN Electronic Journal

Process Safety and Environmental Protection

The paper summarises a global assessment of around 30 prospective negative emissions techniques (NETs) found in the literature. Fourteen techniques including direct air capture, BECCS, biochar, and ocean alkalinity enhancement are considered in more detail. The novel functional categorisation of NETs developed in the course of the assessment is set out and a comparative quantitative summary of the results is presented, focusing on the relative readiness, global capacity, costs and side-effects of the prospective NETs. Both technology specific and more generic potential limitations are discussed, notably those arising from energy requirements, from availability of geological storage capacity and from sustainable supply of biomass. Conclusions are drawn regarding the overall scope of NETs to contribute to safe carbon budgets, and challenges arising in the future governance of NETs, with particular reference to the potential role of carbon markets.

Nature Climate Change, 2015

Energies, 2024

Carbon dioxide, the leading contributor to anthropogenic climate change, is released mainly via fossil fuel combustion, mostly for energy generation. Carbon capture technologies are employed for reducing the emissions from existing huge point sources, along with capturing them from direct air, to reduce the existing concentration. This paper provides a quantitative analysis of the various subtypes of carbon capture technologies with the aim of providing an assessment of each from technological, social, geo-political, economic, and environmental perspectives. Since the emissions intensity and quantity, along with the social-political-economic conditions, vary in different geographic regions, prioritising and finding the right type of technology is critical for achieving ambitious net-zero targets. Four main types of carbon capture technology were analysed (adsorption, absorption, membrane, and cryogenic) under four scenarios depending on the jurisdiction. The Technique for Order of Preference by Similarity to Ideal Solution (also known as the TOPSIS method) was used to establish a quantitative ranking of each, where weightages were allocated according to the emissions status and economics of each depending on the jurisdiction. Furthermore, forecasting the trends for technology types vis à vis carbon neutral targets between 2040 and 2050 was carried out by applying regression analysis on existing data and the emissions footprint of major contributing countries. The study found the membrane score to be the highest in the TOPSIS analysis in three of the four scenarios analysed. However, absorption remains the most popular for post-combustion capture despite having the highest energy penalty per ton of CO 2 capture. Overall, capture rates are well short of projections for carbon neutrality; the methodology put forward for prioritising and aligning appropriate technologies and the region-by-region analysis will help highlight to technocrats, governments, and policymakers the state of the art and how to best utilise them to mitigate carbon emissions-critical in achieving the net-zero goals set at various international agreements on climate change.

Journal of Tropical Forestry and Environment

In accordance with the Paris Agreement, to which Sri Lanka is a Party to, global temperature rise must be kept well below 2°C relative to pre-industrial levels and efforts to limit the temperature increase to 1.5oC above pre-industrial level must be pursued. In response to this, countries who signed the UNFCCC, including Sri Lanka, submitted their Nationally Determined Contributions (NDCs) in 2016 which will come into force during 2021-2030. However, according to Emissions Gap Report 2021 (UNEP 2021), climate pledges combined with other mitigation measures put the world on track for a global temperature rise of 2.7°C by the end of the century which is above the goals of the Paris climate agreement which intended to keep the global temperature rise well below 2°C. Therefore, in order to address this alarming situation, many countries including Sri Lanka have given pledges to become carbon neutral by 2050. This means that the emissions from economic sectors will be reduced as per th...

Frontiers in Climate

Climate change mitigation strategies informed by Integrated Assessment Models (IAMs) increasingly rely on major deployments of negative emissions technologies (NETs) to achieve global climate targets. Although NETs can strongly complement emissions mitigation efforts, this dependence on the presumed future ability to deploy NETs at scale raises questions about the structural elements of IAMs that are influencing our understanding of mitigation efforts. Model inter-comparison results underpinning the IPCC's special report on Global Warming of 1.5 • C were used to explore the role that current assumptions are having on projections and the way in which emerging technologies, economic factors, innovation, and tradeoffs between negative emissions objectives and UN Sustainable Development Goals might have on future deployment of NETs. Current generation IAM scenarios widely assume we are capable of scaling up NETs over the coming 30 years to achieve negative emissions of the same order of magnitude as current global emissions (tens of gigatons of CO 2 /year) predominantly relying on highly land intensive NETs. While the technological potential of some of these approaches (e.g., direct air capture) is much greater than for the land-based technologies, these are seldom included in the scenarios. Alternative NETs (e.g., accelerated weathering) are generally excluded because of connections with industrial sectors or earth system processes that are not yet included in many models. In all cases, modeling results suggest that significant NET activity will be conducted in developing regions, raising concerns about tradeoffs with UN Sustainable Development Goals. These findings provide insight into how to improve treatment of NETs in IAMs to better inform international climate policy discussions. We emphasize the need to better understand relative strength and weaknesses of full suite of NETs that can help inform the decision making for policy makers and stakeholders.

2016

This paper focuses on the risks associated with "negative emission" options for drawing carbon dioxide from the atmosphere through photosynthesis and storing it in landbased sinks. It examines what these risks mean for near-term actions and long-term mitigation strategies, including the 1.5°C and 2°C temperature limits. Negative emissions options have increasingly appeared-sometimes transparently and sometimes only implicitly-in analyses and discussions of society's options for addressing the challenge of climate change. Deployed later in the century, negative emissions could allow society to "undo" emissions that occurred earlier, enabling us to honor a given carbon budget in the long run, even after having grossly exceeded it in prior decades. We identify three types of risks associated with using negative emissions in such strategies: (i) the risk that negative emission options do not prove feasible in the future when they are ultimately required; (ii) the risk that unacceptable ecological and social impacts are unavoidable for large-scale deployment; and, (iii) the risk that the reversal of emission reductions is caused by human or natural forces, including climate change. In light of these three types of risks, we examine four main land-based negative emissions options: ecosystem restoration, mosaic-landscape restoration, reforestation, and bioenergy with carbon capture and sequestration (BECCS). Of the mitigation pathways presented in the literature as "likely" to comply with a 1.5°C or 2°C goal, many assume the future availability of a very high volume of negative emissions (e.g., 1000 GtCO2), despite the absence of reasonable confidence that negative emissions at the required scale will be available from options that are technically and biophysically feasible, ecologically and socially acceptable, and reliably permanent. It is necessary to question whether a pathway can be considered "likely" to comply with a specified goal if it relies on negative emission options that themselves may not have a "likely" chance of proving feasible and providing reliable reductions at the needed scale. Embarking on such pathways could strand us at a later date with an insufficiently transformed energy economy, an exceeded carbon budget, and a carbon debt that cannot be repaid. However, the literature also presents pathways (those that most rapidly reduce emissions from fossil fuels and deforestation) that rely on a significantly lower level of negative emissions for the 1.5°c pathways, or none at all for 2°c pathways. At this lower level, it is possible for ecosystem restoration and reforestation to provide the required volume of negative emissions. This avoids the need to rely on other options (BECCS, in particular) that pose higher risks of technical infeasibility and unacceptable ecological and social impacts.

Environmental Research Letters

Intentionally removing carbon from the atmosphere with negative emission technologies (NETs) will be important to achieve net-zero emissions by mid-century and to limit global warming to 2°C or even 1.5°C (IPCC, 2018). Model scenarios that consider NETs as part of mitigation pathways are still largely restricted to afforestation and bioenergy with carbon capture and storage (BECCS), while the "[f]easibility and sustainability of [NETs] use could be enhanced by a portfolio of options deployed at substantial, but lesser scales, rather than a single option at very large scale" (IPCC 2018, p. 19). Here, we show the results from an anonymous expert survey, including 32 Earth-System-Model (ESM) experts and 18 Integrated-Assessment-Model (IAM) experts, about the role of NETs in future climate policies and about how well the various technologies are represented in current models. We find that they strongly support the view that technology portfolios are requires to achieve negative emissions, however, the responses show that the number and range of NETs that can be assessed in IAMs is small and that IAMs and ESMs are rather applied to analyze technologies separately than in combination. IAM experts in particular consider BECCS as part of a future NETs portfolio; but at the same time, all experts judge the constraints BECCS would face regarding future overall feasibility and more particularly regarding resource competition to be the highest. Regarding the assessment of constraints the ESM experts are much more skeptical than the IAM experts; they also think that the BECCS carbon removal pathways are less sufficiently represented in ESMs compared to what the IAM experts thinks about the representation in their models. Despite the perceived need for NETs portfolios, the range of NETs which can be assessed in IAMs is rather small and ocean NETs have, so far, mostly been overlooked by the IAM experts.

This papers aims to explore future policy challenges and promises of carbon dioxide removal (CDR) technologies. The investigation is motivated by needs to drastically reduce CO2 concentration levels in order to mitigate future harms caused by global warming. Here the focus is on the potential of using CDR as a global solution. By applying general public policy theories and by using analogues drawn from solar radiation management and its policy challenges, the paper explores both ethical and practical obstacles to the mass implementation of CDR. Some of the analysis looks at cost-benefit analysis frameworks, the precautionary principle, the Collingridge dilemma, concerns surrounding research, regulatory mechanisms, and issues relating to funding and resource allocation. The findings show that while there are clear challenges, CDR technologies show enough promise to warrant further research and eventual implementation, especially within the context of current and worrying CO2 concentration trends.

2007