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Pathways for achieving the 1.5–2 °C global temperature moderation target imply a massive scaling of carbon dioxide (CO2) removal technologies, in particular in the 2040s and onwards. CO2 direct air capture (DAC) is among the most promising negative emission technologies (NETs). The energy demands for low-temperature solid-sorbent DAC are mainly heat at around 100 °C and electricity, which lead to sustainably operated DAC systems based on low-cost renewable electricity and heat pumps for the heat supply. This analysis is carried out for the case of the Maghreb region, which enjoys abundantly available low-cost renewable energy resources. The energy transition results for the Maghreb region lead to a solar photovoltaic (PV)-dominated energy supply with some wind energy contribution. DAC systems will need the same energy supply structure. The research investigates the levelised cost of CO2 DAC (LCOD) in high spatial resolution and is based on full hourly modelling for the Maghreb region. The key results are LCOD of about 55 €/tCO2 in 2050 with a further cost reduction potential of up to 50%. The area demand is considered and concluded to be negligible. Major conclusions for CO2 removal as a new energy sector are drawn. Key options for a global climate change mitigation strategy are first an energy transition towards renewable energy and second NETs for achieving the targets of the Paris Agreement.

Biomass-based combined heat and power (CHP) generation with different carbon capture approaches is investigated in this study. Only direct carbon dioxide (CO2) emissions are considered. The selected processes are (i) a circulating fluidized bed boiler for wood chips connected to an extraction/condensation steam cycle CHP plant without carbon capture; (ii) plant (i), but with post-combustion CO2 capture; (iii) chemical looping combustion (CLC) of solid biomass connected to the steam cycle CHP plant; (iv) rotary kiln slow pyrolysis of biomass for biochar soil storage and direct combustion of volatiles supplying the steam cycle CHP plant with the CO2 from volatiles combustion escaping to the atmosphere; (v) case (iv) with additional post-combustion CO2 capture; and (vi) case (iv) with CLC of volatiles. Reasonable assumptions based on literature data are taken for the performance effects of the CO2 capture systems and the six process options are compared. CO2 compression to pipeline pressure is considered. The results show that both bioenergy with carbon capture and storage (BECCS) and biochar qualify as negative emission technologies (NETs) and that there is an energy-based performance advantage of BECCS over biochar because of the unreleased fuel energy in the biochar case. Additional aspects of biomass fuels (ash content and ash melting behavior) and sustainable soil management (nutrient cycles) for biomass production should be quantitatively considered in more detailed future assessments, as there may be certain biomass fuels, and environmental and economic settings where biochar application to soils is indicated rather than the full conversion of the biomass to energy and CO2.

Negative emission technologies (NETs) are a set of technologies that could retrieve greenhouse gases from the atmosphere. NETs could dramatically contribute to maintaining the temperature increase to within the limit of 2 °C or even 1.5 °C. Bioenergy with carbon capture and storage (BECCS) is one of the most studied NETs. BECCS captures carbon dioxide (CO2) emissions coming from a bioenergy plant—e.g., electricity, biofuels, and hydrogen—and stores those emissions in a geologic reservoir, typically a saline aquifer. The purpose of this article is to investigate whether a research community exists on BECCS, and whether it is aligned with research priorities. To do so, a bibliometric analysis is conducted based on author collaborations on BECCS in academic journals between 2001 and 2017. The co-authorship network shows that BECCS research is largely based on the integrated assessment model (IAM) research community. These models analyze how power and transportation systems evolve under a climate constraint in the long run, e.g., until 2100. Such a focus has advantages and drawbacks. On the one hand, it helps to build a common vision of the technology and possible roadmaps. On the other hand, I highlight that the implementation features of BECCS in the near future are insufficiently assessed, e.g., techno-economic analyses, business models, local-scale assessments, and comparison with other NETs. These issues are marginal in the network, whereas long-term analyses are at its core. Future research programmes should better include them to avoid a considerable disappointment about the real potential of BECCS.

To combat climate change, carbon dioxide must be prevented from entering the atmosphere or even removed from it. Biochar is one potential practice to sequester carbon, but its climate change mitigation potential depends on a multitude of parameters. Differentiating areas of low and high climate change mitigation through biochar addition is key to maximize its potential and effectively use the available feedstock for its production. This study models the realistic application of 1 metric tonne (t) per hectare (ha) of forest harvest residue derived biochar over the climatically and pedologically diverse agricultural area of British Columbia, Canada, and provides a framework and assumptions for reproducibility in other parts of the world. The model accounts for the direct (input of organic carbon) and indirect (enhanced plant biomass) effects of biochar on soil organic carbon stock, its impact on nitrous oxide emissions from soils, and the avoided emissions from the reduced lime requirement due to biochar's alkalinization potential. Impacts are modelled over 20‐year time horizon to account for the duration and magnitude variation over time of biochar effect on plant biomass and nitrous oxide emissions from soil and conform to the IPCC GWP 20‐year time horizon reporting. The results show that a single application of 1 t of biochar per ha−1 can mitigate between 3 and 5 t CO2e ha−1 over a 20‐year time frame. Applied to the 746,000 ha of agricultural land of British Columbia this translate to the mitigation of a total of 2.5 million metric tonnes (Mt) CO2e over a 20‐year time frame. Further, the results identify agricultural areas in the Lower Mainland region (the southwestern corner of British Columbia) as the area maximizing climate change mitigation potential through biochar addition due to a combination of relative high temperature, high precipitation, and crops with high nitrogen requirement. This study models the application of 1 t ha−1 of forest harvest residue derived biochar over the agricultural area of British Columbia, Canada, and offers a framework for reproducibility. It accounts for the direct (input of organic carbon) and indirect (enhanced plant biomass) effects of biochar on soil organic carbon stock, its impact on nitrous oxides emissions from soils, and the reduced lime requirement due to biochar's alkalinization potential. The results show that a single application of 1 t of biochar can mitigate between 3 and 5 t CO2e per hectare.

Either increasing C input to or reducing C release from soils can enhance soil C sequestration. Afforestation and reforestation have great potential in improving soil C sequestration. Long-term observations about the impacts of biochar on soil C sequestration are necessary. Climate change vigorously threats human livelihoods, places and biodiversity. To lock atmospheric CO2 up through biological, chemical and physical processes is one of the pathways to mitigate climate change. Agricultural soils have a significant carbon sink capacity. Soil carbon sequestration (SCS) can be accelerated through appropriate changes in land use and agricultural practices. There have been various meta-analyses performed by combining data sets to interpret the influences of some methods on SCS rates or stocks. The objectives of this study were: (1) to update SCS capacity with different land-based techniques based on the latest publications, and (2) to discuss complexity to assess the impacts of the techniques on soil carbon accumulation. This review shows that afforestation and reforestation are slow processes but have great potential for improving SCS. Among agricultural practices, adding organic matter is an efficient way to sequester carbon in soils. Any practice that helps plant increase C fixation can increase soil carbon stock by increasing residues, dead root material and root exudates. Among the improved livestock grazing management practices, reseeding grasses seems to have the highest SCS rate.

Climate change is defined as the shift in climate patterns mainly caused by greenhouse gas emissions from natural systems and human activities. So far, anthropogenic activities have caused about 1.0 °C of global warming above the pre-industrial level and this is likely to reach 1.5 °C between 2030 and 2052 if the current emission rates persist. In 2018, the world encountered 315 cases of natural disasters which are mainly related to the climate. Approximately 68.5 million people were affected, and economic losses amounted to $131.7 billion, of which storms, floods, wildfires and droughts accounted for approximately 93%. Economic losses attributed to wildfires in 2018 alone are almost equal to the collective losses from wildfires incurred over the past decade, which is quite alarming. Furthermore, food, water, health, ecosystem, human habitat and infrastructure have been identified as the most vulnerable sectors under climate attack. In 2015, the Paris agreement was introduced with the main objective of limiting global temperature increase to 2 °C by 2100 and pursuing efforts to limit the increase to 1.5 °C. This article reviews the main strategies for climate change abatement, namely conventional mitigation, negative emissions and radiative forcing geoengineering. Conventional mitigation technologies focus on reducing fossil-based CO2 emissions. Negative emissions technologies are aiming to capture and sequester atmospheric carbon to reduce carbon dioxide levels. Finally, geoengineering techniques of radiative forcing alter the earth’s radiative energy budget to stabilize or reduce global temperatures. It is evident that conventional mitigation efforts alone are not sufficient to meet the targets stipulated by the Paris agreement; therefore, the utilization of alternative routes appears inevitable. While various technologies presented may still be at an early stage of development, biogenic-based sequestration techniques are to a certain extent mature and can be deployed immediately.

Abstract Tree-ring time series provide long-term, annually resolved information on the growth of trees. When sampled in a systematic context, tree-ring data can be scaled to estimate the forest carbon capture and storage of landscapes, biomes, and—ultimately—the globe. A systematic effort to sample tree rings in national forest inventories would yield unprecedented temporal and spatial resolution of forest carbon dynamics and help resolve key scientific uncertainties, which we highlight in terms of evidence for forest greening (enhanced growth) versus browning (reduced growth, increased mortality). We describe jump-starting a tree-ring collection across the continent of North America, given the commitments of Canada, the United States, and Mexico to visit forest inventory plots, along with existing legacy collections. Failing to do so would be a missed opportunity to help chart an evidence-based path toward meeting national commitments to reduce net greenhouse gas emissions, urgently needed for climate stabilization and repair.

Direct Air Capture with Carbon Storage (DACCS) technologies represent one of the most significant potential tools for tackling climate change by making net-zero and net-negative emissions achievable, as deemed necessary in reports from the Intergovernmental Panel on Climate Change and the European Green Deal. We draw from a novel and original dataset of expert interviews ( N = 125) to distil ten recommendations for future DACCS policy. After providing a literature review on DACCS and explaining our methods of data collection, we present these recommendations as follows: (a) follow governance principles that ensure ‘negative’ emissions; (b) prioritize long-term carbon storage; (c) appreciate and incentivize scale; (d) co-develop with capture, transport, and storage; (e) phase in a carbon price; (f) couple with renewables; (g) harness hub deployment; (h) maintain separate targets; (i) embrace certification and compliance; and (j) recognize social acceptance. All ten recommendations are important, and all speak to the urgency and necessity of better managing and shaping the potentially impending DACCS transition.

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.

PurposeThis paper aims to explore three operations and supply chain management (OSCM) approaches for meeting the 2 °C targets to counteract climate change: adaptation (adjusting to climatic impacts); mitigation (innovating towards low-carbon practices); and carbon-removing negative emissions technologies (NETs). We suggest that adaptation nor mitigation may be enough to meet the current climate targets, thus calling for NETs, resulting in the following question: How can operations and supply chains be reconceptualized for NETs?Design/methodology/approachWe draw on the sustainable supply chain and transitions discourses along with interview data involving 125 experts gathered from a broad research project focused on geoengineering and NETs. We analyze three case studies of emerging NETs (biochar, direct air carbon capture and storage and ocean alkalinity enhancement), leading to propositions on the link between OSCM and NETs.FindingsAlthough some NETs are promising, there remains considerable variance and uncertainty over supply chain configurations, efficacy, social acceptability and potential risks of unintended detrimental consequences. We introduce the concept of transformative OSCM, which encompasses policy interventions to foster the emergence of new technologies in industry sectors driven by social mandates but lack clear commercial incentives.Originality/valueTo the best of the authors’ knowledge, this paper is among the first that studies NETs from an OSCM perspective. It suggests a pathway toward new industry structures and policy support to effectively tackle climate change through carbon removal.