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Catalytic steam hydrogasification of coal is a direct method for methane production. Calcium looping concept is usually used in coal gasification process for in-situ carbon dioxide removal and heat supply. In this paper, a new process combining catalytic steam hydrogasification and calcium looping was proposed and investigated using a self designed instantaneously feeding reactor under high-temperature and pressurized conditions. The effects of operation conditions (including hydrogen concentration with a range of 0–50 vol%, gasification pressure with a range of 0.1–3.5 MPa, gasification temperature with a range of 700–800 °C, and gasification-calcination cycle number up to six) on the performance of the new process have been studied. The results show that: (i) increasing H2 concentration is beneficial to methane products; (ii) high temperature and low pressure are not conducive to methane production and carbon dioxide capture as well as the self-sustained heat supply in gasifier; (iii) the methane content and carbon conversion can be maintained at 30–40 vol% and 75–80% for the durability tests. According to the performance of gas products, 750 °C 3.5 MPa and Ca/C = 0.5 are suggested for the new process. In addition, the gasification reactivity can be affected by the Ca–K-Char interaction as indicated by the XRD, FT-IR and SEM-EDX analysis.

Biochar is a promising carbon dioxide removal (CDR) technology for climate change mitigation. Current procedures for its determination are lengthy, labor-intensive, and difficult to conduct. Benzene polycarboxylic acids (BPCA) are the most promising molecular markers for identification and quantification of biochar and its quality as they specifically represent the stable polyaromatic backbone of biochar. Therefore, using the BPCA method, its stability and, thus, its C sequestration potential could be used for CDR accounting. The current BPCA method relies on a specific high-pressure digestion apparatus, which is not available around the world. Therefore, the aims of the present work were (i) to compare the conventional high-pressure nitric acid oxidation with a microwave-assisted digestion technique and optimize the oxidation conditions in such a way that previous results are comparable with future ones, and (ii) to significantly reduce the digestion time of soil samples of 8 h and to develop a suitable routine method that produces comparable and reproducible results. For this purpose, soil and control sample series were prepared for different temperature–time-program. Obtained results were compared with the values of the conventional method both for individual samples and for the whole dataset separately. To ensure the representativeness of the results, in addition to various soil samples with different properties, we included two reference materials into our data set, one without biochar (wheat flour) and a biochar sample. Our results showed that conventional nitric acid oxidation in the BPCA determination at 170 °C and 8 h can be substituted by digestion in a microwave reaction system (CEM Mars6) at 190 °C and 1 h. Our results further showed that this condition needs to be strictly matched, because, otherwise, over- or underestimation of biochar quantity and/or quality will be the consequence. The goal of a less time-consuming BPCA extraction from soil samples was achieved by reducing the extraction time from 8 to 1 h using the microwave-assisted method. However, one disadvantage of the new method is that five times more sample material and chemicals are needed for further BPCA analysis, compared to the original method.

We describe a new principle - the Alkalinity Concentration Swing (ACS) - for direct air capture of carbon dioxide driven by concentrating an alkaline solution that has been exposed to the atmosphere and loaded with dissolved inorganic carbon. Upon concentration, the partial pressure of carbon dioxide increases, allowing for extraction and compression. We find that higher concentration factors result in proportionally higher outgassing pressure, and higher initial alkalinity concentrations at the same concentration factor outgas a higher concentration of CO2 relative to the feed solution. We examine two desalination technologies, reverse osmosis and capacitive deionization, as possible implementation for the ACS, and evaluate two simplified corresponding energy models. We compare the ACS to incumbent technologies and make estimates on water, land, and energy requirements for capturing one million tonnes of CO2 per year. We find that estimates for the lower end of the energy range for both reverse osmosis and capacitive deionization approaches are lower than or roughly equal to incumbent direct air capture approaches. For most conditions, we find an inverse relationship between the required energy and water processing volume per million tonnes of CO2. Realizing the ACS requires a simple alkaline aqueous solvent (e.g. potassium alkalinity carrier) and does not require heat as a driving mechanism. More generally, the ACS can be implemented through industrial-scale desalination approaches, meaning current technology could be leveraged for scale-up., 39 pages, 5 main text figures, 6 appendix figures

Patients with acute respiratory distress syndrome and acute kidney injury (AKI) treated by kidney replacement therapy may also require treatment with extracorporeal carbon dioxide removal (ECCO2 R) devices to permit protective or ultraprotective mechanical ventilation. We developed a mathematical model of acid-base balance during extracorporeal therapy using ECCO2 R and continuous venovenous hemofiltration (CVVH) devices applied in series for the treatment of mechanically ventilated AKI patients. Published data from clinical studies of mechanically ventilated AKI patients treated by CVVH at known infusion rates of substitution fluid without ECCO2 R were used to adjust the model parameters to fit plasma levels of arterial partial pressure of carbon dioxide (PaCO2 ), arterial plasma bicarbonate concentration ([HCO3 ]), and plasma pH (as well as certain other unmeasured physiological variables). The effects of applying ECCO2 R at an unchanged and a reduced tidal volume on PaCO2 , [HCO3 ] and plasma pH were then simulated assuming carbon dioxide removal rates from the ECCO2 R device measured in the clinical studies. Agreement of such model predictions with clinical data was good whether the ECCO2 R device was positioned proximal or distal to the CVVH device in the extracorporeal circuit. Although carbon dioxide removal rates from the ECCO2 R device measured in one previous clinical study were higher when it was placed proximal to the CVVH device, suggesting that such in-series positioning was optimal, the current mathematical model demonstrates that proximal positioning of the ECCO2 R device also results in lower bicarbonate (and, therefore, total carbon dioxide) removal from the distal CVVH device. Thus, the removal of total carbon dioxide by such extracorporeal circuits is relatively independent of the position of the in-series devices. It is concluded that the described mathematical model has quantitative accuracy; these results suggest that the overall acid-base balance when using ECCO2 R and CVVH devices in a single extracorporeal circuit will be similar, independent of their in-series position.

An experimental work was carried out for the recovery of carbon dioxide in monoethanolamine solution (MEA) using pilot plant of perforated sieve tray column. The effect of MEA concentration, carbon dioxide ratio in the gas phase, liquid flow rate, gas flow rate and CO2 loading in the absorption solution was investigated. The results show that the efficiency of recovery increased by increasing the concentration of MEA and better removal efficiency can be achieved by increasing the liquid flow rate and the contact time between CO2 and the absorbent and that can be happened by decreasing the air flow rate.

The presence of carbon dioxide in natural gases can lower the quality of natural gas and can cause CO2 freezing problems. Therefore, using reliable techniques for the reduction and elimination of carbon dioxide from natural gases is necessary. The aqueous diethanol amine (DEA) solution's ability to simultaneously absorb H2S and CO2 from sour natural gases makes it possible to use this solution in the natural gas sweetening process. The goal of this work was to determine the maximum amount of the removed CO2 by an aqueous DEA solution in one of the gas sweetening plants of the National Iranian South Oilfields Company (NISOC). For this purpose, based on the obtained designed experiment results using the L9 orthogonal array Taguchi method, the experiments were conducted and three levels of amine concentrations (25, 28, and 30 wt %), temperatures (40, 50, and 60 °C), and circulation rates of lean amine (220, 240, and 260 m3 h-1) were considered as the key operational parameters on CO2 removal. To evaluate the ability of the HYSYS simulation software and the Kent-Eisenberg thermodynamic model to predict CO2 absorption by an aqueous DEA solution in the gas sweetening process, the field data were compared with the results of the simulation. It was observed that the maximum removal of CO2 is achieved at a lean amine concentration of 30 wt %, a temperature of 40 °C, and a circulation rate of 260 m3 h-1. Also, the experimental results indicate that the effects of the selected process variables on CO2 absorption are not linear and the most effective parameter on carbon dioxide removal is the concentration of amine in an aqueous solution and the temperature of the lean amine has the least effect. Besides, the obtained simulation results are in the range of the unit design basis but have some deviations from field data. The findings of this study can help in better understanding of the selection of the effective variables in the natural gas sweetening process and obtaining their appropriate values to achieve the highest efficiency.

This review provides an analysis of modern process technologies for carbon dioxide removal from various gas mixtures (such as natural gas or hydrocarbon conversion gases in ammonia and syngas production facilities), as well as from flue gases generated during the combustion of carbon-containing feedstocks in power plants. The review also discusses various approaches to improve absorption/desorption processes, both in terms of extending the range of practicable amine solvents and the prospects for the implementation of a new equipment type, namely membrane contactors based on hollow fiber membranes or ceramic tubular elements. Finally, the paper describes a process configuration for the decarbonation of rich amine solvents at ≤90°C using 12% monoethanolamine (MEA) solutions to prevent the solvent from thermo-oxidative degradation.

Meeting internationally agreed-upon climate targets requires carbon dioxide removal (CDR) strategies coupled with an urgent phase-down of fossil fuel emissions. However, the efficacy and wider impacts of CDR are poorly understood. Enhanced rock weathering (ERW) is a land-based CDR strategy requiring large-scale field trials. Here we show that a low 3.44 t ha−1 wollastonite treatment in an 11.8 ha acid-rain-impacted forested watershed in New Hampshire, USA, led to cumulative carbon capture by carbonic acid weathering of 0.025–0.13 t CO2 ha−1 over 15 years. Despite a 0.8–2.4 t CO2 ha−1 logistical carbon penalty from mining, grinding, transportation, and spreading, by 2015 weathering together with increased forest productivity led to net CDR of 8.5–11.5 t CO2 ha−1. Our results demonstrate that ERW may be an effective, scalable CDR strategy for acid-impacted forests but at large scales requires sustainable sources of silicate rock dust.

Global warming due to greenhouse gases has become a serious global issue. Extensive efforts are being made to fighting this phenomenon through carbon capture as carbon dioxide (CO2) is its major contributor. This study focused on CO2 capture in packed bed column reactor using Poly-(D) glucosamine under the various process parameters such as temperature, feed flow rate and mass of the adsorbent. Statistical design of experiments was carried out in order to analysis the effect process parameters on the capacity of CO2 capture in packed bed column. The obtained results show that feed flow rate has the significant affect compared to others. The maximum of 956 mg of CO2 is captured under the following operating conditions; temperature of 40oC, feed flow rate of 30 ml/min and 0.25 g of the Poly-(D) glucosamine. The ability of Poly-(D) glucosamine to capture the CO2 in packed bed column is confirmed.

The ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim][Ac]), was used to remove carbon dioxide (CO2) from a simulated spacecraft cabin atmosphere (2 mm Hg (267 Pa)) partial pressure of CO2 w...

Natural gas based hydrogen production with carbon capture and storage is referred to as blue hydrogen. If substantial amounts of CO2 from natural gas reforming are captured and permanently stored, such hydrogen could be a low-carbon energy carrier. However, recent research raises questions about the effective climate impacts of blue hydrogen from a life cycle perspective. Our analysis sheds light on the relevant issues and provides a balanced perspective on the impacts on climate change associated with blue hydrogen. We show that such impacts may indeed vary over large ranges and depend on only a few key parameters: the methane emission rate of the natural gas supply chain, the CO2 removal rate at the hydrogen production plant, and the global warming metric applied. State-of-the-art reforming with high CO2 capture rates combined with natural gas supply featuring low methane emissions does indeed allow for substantial reduction of greenhouse gas emissions compared to both conventional natural gas reforming and direct combustion of natural gas. Under such conditions, blue hydrogen is compatible with low-carbon economies and exhibits climate change impacts at the upper end of the range of those caused by hydrogen production from renewable-based electricity. However, neither current blue nor green hydrogen production pathways render fully "net-zero" hydrogen without additional CO2 removal., Sustainable Energy & Fuels, 6 (1), ISSN:2398-4902

Governance is essential to the structure of incentives and the accounting necessary for large-scale deployment of methods for carbon dioxide removal from the atmosphere, particularly in light of the urgency to upscale carbon removal to stay below the 2°C global climate change target. A key governance challenge is operationalizing standards for the permanence of carbon sequestered in terrestrial and coastal ecosystems. There are multiple risks of reversal of carbon storage in these ecosystems and release of carbon back to the atmosphere. This paper reviews issues of permanence in four approaches for carbon removal focusing on carbon uptake and potential side-effects of long-term land commitments. Recognizing that permanence is a considerable barrier to large-scale application of land-based carbon removal, we argue that temporary carbon storage can still provide climate benefits in the short run. A multilateral governance framework should redefine permanence requirements and reflect principles of sustainability, polycentricity, and land stewardship.

Future levels of climate change depend not only on carbon emissions but also on carbon uptake by the land and the ocean. Here we are using the Earth system model (ESM1) version of the Australian Community Climate and Earth System Simulator (ACCESS) to explore the potential and impact of removing carbon dioxide (CO2) from the atmosphere through the climate and carbon cycle reversibility experiment. This experiment builds on the standard Coupled Model Intercomparison Project (CMIP) experiment, increasing CO2 at 1% per year until 4xCO2 is reached. The atmospheric CO2 levels are then decreased at the same rate which brings the CO2 back to pre-industrial levels. We then continue to run the model with constant CO2 for another 350 years. Our analysis focuses on the response of the land carbon cycle. We find that carbon stores are largely reversible at the global scale over the timescale of changing CO2. However, carbon stores continue to decrease after CO2 returns to its initial value, and the land loses another 40 Pg of carbon (PgC) with the largest change in the tropics. It takes about 300 years beyond the period of changing CO2 for the carbon stores to recover. Interestingly, we saw strong regional variations in the strength of the land response to changing CO2. Australia showed the largest increase/decrease in biomass carbon (about 40%) and the largest variability in productivity, which was strongly correlated with rainfall. This highlights the importance of assessing the regional response to understanding the processes underlying the response and the sensitivity of these processes within each model. This understanding will benefit future multi-model analyses of this reversibility experiment. It also illustrates more generally the potential to use Earth system model experiments as part of the evaluation of proposed applications of carbon dioxide removal (CDR) technologies. As such, we recommend that these types of modelling experiments be included when mitigation policies are developed.

Technology:Extracorporeal carbon dioxide removal means the removal of carbon dioxide from the blood across a gas exchange membrane without substantially improving oxygenation. Carbon dioxide removal is possible with substantially less extracorporeal blood flow than needed for oxygenation. Techniques for extracorporeal carbon dioxide removal include (1) pumpless arterio-venous circuits, (2) low-flow venovenous circuits based on the technology of continuous renal replacement therapy, and (3) venovenous circuits based on extracorporeal membrane oxygenation technology.Indications:Extracorporeal carbon dioxide removal has been shown to enable more protective ventilation in acute respiratory distress syndrome patients, even beyond the so-called “protective” level. Although experimental data suggest a benefit on ventilator induced lung injury, no hard clinical evidence with respect to improved outcome exists. In addition, extracorporeal carbon dioxide removal is a tool to avoid intubation and mechanical ventilation in patients with acute exacerbated chronic obstructive pulmonary disease failing non-invasive ventilation. This concept has been shown to be effective in 56-90% of patients. Extracorporeal carbon dioxide removal has also been used in ventilated patients with hypercapnic respiratory failure to correct acidosis, unload respiratory muscle burden, and facilitate weaning. In patients suffering from terminal fibrosis awaiting lung transplantation, extracorporeal carbon dioxide removal is able to correct acidosis and enable spontaneous breathing during bridging. Keeping these patients awake, ambulatory, and breathing spontaneously is associated with favorable outcome.Complications:Complications of extracorporeal carbon dioxide removal are mostly associated with vascular access and deranged hemostasis leading to bleeding. Although the spectrum of complications may differ, no technology offers advantages with respect to rate and severity of complications. So called “high-extraction systems” working with higher blood flows and larger membranes may be more effective with respect to clinical goals.

Extracorporeal carbon dioxide (CO2 ) removal (ECCO2 R) facilitates the use of low tidal volumes during protective or ultraprotective mechanical ventilation when managing patients with acute respiratory distress syndrome (ARDS); however, the rate of ECCO2 R required to avoid hypercapnia remains unclear. We calculated ECCO2 R rate requirements to maintain arterial partial pressure of CO2 (PaCO2 ) at clinically desirable levels in mechanically ventilated ARDS patients using a six-compartment mathematical model of CO2 and oxygen (O2 ) biochemistry and whole-body transport with the inclusion of an ECCO2 R device for extracorporeal veno-venous removal of CO2 . The model assumes steady state conditions. Model compartments were lung capillary blood, arterial blood, venous blood, post-ECCO2 R venous blood, interstitial fluid and tissue cells, with CO2 and O2 distribution within each compartment; biochemistry included equilibrium among bicarbonate and non-bicarbonate buffers and CO2 and O2 binding to hemoglobin to elucidate Bohr and Haldane effects. O2 consumption and CO2 production rates were assumed proportional to predicted body weight (PBW) and adjusted to achieve reported arterial partial pressure of O2 and a PaCO2 level of 46 mmHg at a tidal volume of 7.6 mL/kg PBW in the absence of an ECCO2 R device based on average data from LUNG SAFE. Model calculations showed that ECCO2 R rates required to achieve mild permissive hypercapnia (PaCO2 of 46 mmHg) at a ventilation frequency or respiratory rate of 20.8/min during mechanical ventilation increased when tidal volumes decreased from 7.6 to 3 mL/kg PBW. Higher ECCO2R rates were required to achieve normocapnia (PaCO2 of 40 mmHg). Model calculations also showed that required ECCO2R rates were lower when ventilation frequencies were increased from 20.8/min to 26/min. The current mathematical model predicts that ECCO2R rates resulting in clinically desirable PaCO2 levels at tidal volumes of 5-6 mL/kg PBW can likely be achieved in mechanically ventilated ARDS patients with current technologies; use of ultraprotective tidal volumes (3-4 mL/kg PBW) may be challenging unless high mechanical ventilation frequencies are used.

Supersonic separators offer a cleaner offshore processing of natural gas with carbon dioxide content from deep-water oil-gas fields. Conventional offshore gas processing comprises water dew-point adjustment via glycol-absorption, hydrocarbon dew-point adjustment via Joule-Thomson expansion, and carbon dioxide removal via membrane-permeation. Alternative processing contemplates the use of supersonic separators for adjusting gas dew-points followed by carbon dioxide capture via membrane-permeation (so-called SS-MP scheme); or for adjusting gas dew-points and also accomplishing carbon dioxide abatement (so-called SS-SS scheme). The conventional process is environmentally and economically compared with SS-MP and SS-SS for application in offshore rigs treating raw gas (44%mol carbon dioxide) to produce exportable fuel-gas (≈20%mol carbon dioxide), while dispatching carbon dioxide rich fluid (≈75%mol carbon dioxide) for enhanced oil recovery in the oil-gas field. Results show that SS-MP requires 7.8% less power than the conventional process. Moreover, implementing SS-SS deepens the advantage against the conventional operation because SS-SS produces carbon dioxide rich fluid at high-pressure, requiring much less compression power for enhanced oil recovery than the low-pressure permeate from membrane-permeation. SS-SS has lowest carbon emission (−28.3%), lowest power consumption (−21.3%) and best economic performance: lowest manufacturing cost and lowest compressor investment. Thus, SS-SS is the overall best and cleanest solution, with highest 20 years net value (+860 MMUSD) and lowest environmental impact.

Offshore gas processing presents challenges, especially when high flow rates, high-pressure and high carbon dioxide contents are involved. The present scenario comprehends offshore processing of high flow rate of high-pressure natural gas with 68%mol carbon dioxide, which results from oil production and behaves as a dense supercritical fluid. The processing goals with this fluid comprise: [A] water dew-point adjustment; [B] hydrocarbon dew-point adjustment; [C] decarbonation of a small part to 20%mol carbon dioxide fuel-gas for power production; and [D] compression/pumping of the remaining fluid enriched with carbon dioxide from decarbonation for enhanced oil recovery. For these tasks the industry considers traditional well established processes such as molecular-sieves adsorption for water dew-point adjustment, Joule-Thompson expansion for hydrocarbon dew-point adjustment and membrane-permeation for carbon dioxide removal. However, conventional technologies can become cumbersome in such awkward conditions. Thus, unconventional solutions are sought for reliability, lower equipment size/weight, and better power consumption, emissions and environmental sustainability. Recently, supersonic separators have been analyzed in proof-of-concept researches for natural gas processing. In this regard, this work quantitatively proves that goals [A],[B],[C] are achievable using only supersonic separators, attaining 33% higher net value, 40% greater oil production, 10% lower investment and economic leverage to reach lower carbon emission relatively to conventional counterparts.

The Representative Concentration Pathway 2.6 (RCP2.6), which is broadly compatible with the Paris Agreement's temperature goal by 1.5-2°C, contains substantial reductions in agricultural non-CO2 emissions besides the deployment of Carbon Dioxide Removal (CDR). Failing to mitigate agricultural methane and nitrous oxide emissions could contribute to an overshoot of the RCP2.6 warming by about 0.4°C. We explore using additional CDR to offset alternative agricultural non-CO2 emission pathways in which emissions either remain constant or rise. We assess the effects on the climate of calculating CDR rates to offset agricultural emission under two different approaches: relying on the 100-year global warming potential conversion metric (GWP100) and maintaining effective radiative forcing levels at exactly those of RCP2.6. Using a reduced-complexity climate model, we find that the conversion metric leads to a systematic underestimation of needed CDR, reaching only around 50% of the temperature mitigation needed to remain on the RCP2.6 track. This is mostly because the metric underestimates, in the near term, forcing from short-lived climate pollutants such as methane. We test whether alternative conversion metrics, the GWP20 and GWP∗, are more suitable for offsetting purposes, and found that they both lead to an overestimation of the CDR requirements. Under alternative agricultural emissions pathways, holding to RCP2.6 total radiative forcing requires up to twice the amount of CDR that is already included in the RCP2.6. We examine the costs of this additional CDR, and the effects of internalizing these in several agricultural commodities. Assuming an average CDR cost by $150/tCO2, we find increases in prices of up to 41% for beef, 14% for rice, and 40% for milk in the United States relative to current retail prices. These figures are significantly higher (for beef and rice) under a global scenario, potentially threatening food security and welfare. Although the policy delivers a mechanism to finance the early deployment of CDR, using CDR to offset remaining high emissions may well hit other non-financial constraints and can thus only support, and not substitute, emission reductions., PLoS ONE, 16 (3), ISSN:1932-6203

Carbon dioxide removal (CDR) will be required to keep global temperature rise below 2°C based on IPCC models. Greater adoption of carbon capture utilization and storage (CCUS) technologies will drive demand for CDR. Public procurement of low carbon materials is a powerful and under-utilized tool for accelerating the development and of CCUS through a targeted and well-regulated approach. The policy environment is nascent and presents significant barriers for scaling and guiding emerging technology solutions. The concrete sector has unique attributes that make it ideally suited for large-scale low-carbon public procurement strategies. This sector offers immediate opportunities to study the efficacy of a supportive policy and regulatory environment in driving the growth of CCUS solutions.

The world adds about 51 Gt of greenhouse gases to the atmosphere each year, which will yield dire global consequences without aggressive action in the form of carbon dioxide removal (CDR) and other technologies. A suggested guideline requires that proposed CDR technologies be capable of removing at least 1% of current annual emissions, about half a gigaton, from the atmosphere each year once fully implemented for them to be worthy of pursuit. Basalt carbonation coupled to direct air capture (DAC) can exceed this baseline, but it is likely that implementation at the gigaton-per-year scale will require increasing per-well CO2 injection rates to a point where CO2 forms a persistent, free-phase CO2 plume in the basaltic subsurface. Here, we use a series of thermodynamic calculations and basalt dissolution simulations to show that the development of a persistent plume will reduce carbonation efficiency (i.e., the amount of CO2 mineralized per kilogram of basalt dissolved) relative to existing field projects and experimental studies. We show that variations in carbonation efficiency are directly related to carbonate mineral solubility, which is a function of solution alkalinity and pH/CO2 fugacity. The simulations demonstrate the sensitivity of carbonation efficiency to solution alkalinity and caution against directly extrapolating carbonation efficiencies inferred from laboratory studies and small-injection-rate field studies conducted under elevated alkalinity and/or pH conditions to gigaton-per-year scale basalt carbonation. Nevertheless, all simulations demonstrate significant carbonate mineralization and thus imply that significant mineral carbonation can be expected even at the gigaton-per-year scale if basalts are given time to react.

We introduce solar geoengineering (SG) and carbon dioxide removal (CDR) into an integrated assessment model to analyze the trade-offs between mitigation, SG, and CDR. We propose a novel empirical parameterization of SG that disentangles its efficacy, calibrated with climate model results, from its direct impacts. We use a simple parameterization of CDR that decouples it from the scale of baseline emissions. We find that (a) SG optimally delays mitigation and lowers the use of CDR, which is distinct from moral hazard; (b) SG is deployed prior to CDR while CDR drives the phasing out of SG in the far future; (c) SG deployment in the short term is relatively independent of discounting and of the long-term trade-off between SG and CDR over time; (d) small amounts of SG sharply reduce the cost of meeting a [Formula: see text]C target and the costs of climate change, even with a conservative calibration for the efficacy of SG.

Carbon dioxide removal technologies, such as bioenergy with carbon capture and direct air capture, are valuable for stringent climate targets. Previous work has examined implications of carbon removal, primarily bioenergy-based technologies using integrated assessment models, but not investigated the effects of a portfolio of removal options on power systems in detail. Here, we explore impacts of carbon removal technologies on electric sector investments, costs, and emissions using a detailed capacity planning and dispatch model with hourly resolution. We show that adding carbon removal to a mix of low-carbon generation technologies lowers the costs of deep decarbonization. Changes to system costs and investments from including carbon removal are larger as policy ambition increases, reducing the dependence on technologies like advanced nuclear and long-duration storage. Bioenergy with carbon capture is selected for net-zero electric sector emissions targets, but direct air capture deployment increases as biomass supply costs rise., Carbon dioxide removal technologies such as bioenergy with carbon capture and direct air can influence power sector planning and operations. Here the authors show how carbon removal options lower costs of deep decarbonization and alter electric sector investments.

As the technical and political challenges of land-based carbon dioxide removal (CDR) approaches become more apparent, the oceans may be the new “blue” frontier for carbon drawdown strategies in climate governance. Drawing on lessons learnt from the way terrestrial carbon dioxide removal emerged, we explore increasing overall attention to marine environments and mCDR projects, and how this could manifest in four entwined knowledge systems and governance sectors. We consider how developments within and between these “frontiers” could result in different futures—where hype and over-promising around marine carbon drawdown could enable continued time-buying for the carbon economy without providing significant removals, or where reforms to modeling practices, policy development, innovation funding, and legal governance could seek co-benefits between ocean protection, economy, and climate.

The rapid growth of energy demand and consumption from fossil fuels has been of great concern since the last decade. Renewable energy, including biogas production from wastes, has been studied to ease up the energy crisis problems. This study aims to synthesize bio-cellulose acetate (CA) membranes from agricultural waste and to study its efficiency in the removal of CO2 from biogas. The bio-CA membranes were synthesized from acetylation of bacterial cellulose (BC) and obtained from coconut juice residues (CJRs). The results showed that both chemical and physical characteristics of the bio-CA membrane were compared with those of the chemical CA membranes. The CO2 removal capacity of the bio-CA membranes was tested in a membrane separation unit. The maximum CO2 selectivity of 29.53 was achieved when using the bio-CA membrane with a thickness of 0.05 mm under the feed pressure of 0.1 MPa. Thick CA membranes exhibited better CO2 selectivity performance, particularly at low operating pressure. However, the CO2/CH4 separation factor decreased in the high-pressure region, probably because of the plasticization of the gas components. Eco-efficiency was evaluated to determine the optimal process conditions. In terms of eco-efficiency, the results suggested that the optimal condition was a bio-CA membrane of 0.05-mm thickness and pressure of 0.1 MPa. The implication of this study is promoting a zero-waste environment in which the agricultural residues could be potentially used in the synthesis of high-value CA membranes for biogas purification applications in energy production.

This thesis explores recent proposals for novel carbon sinks (carbon removal) and planetary sunshades (sunlight reflection) – often treated as forms of climate engineering, or deliberate and large-scale climate interventions. I examine sunlight reflection and carbon removal as case studies of emerging sociotechnical strategies in climate governance, where imperfect projections produced by expert assessments influence political debate and planning. I explore the hidden politics of expert assessment: How knowledge is constructed, contested, and communicated by expert networks, and how these shape understandings of future climate options. My inquiries are grounded in analytical frameworks from the intersection of global environmental governance and science and technology studies, as well as stakeholder-facing technology governance frameworks such as ‘responsible research and innovation’. I ask three research questions. Firstly: How is knowledge and evidence about sunlight reflection and carbon removal created (Chapters 2 and 3)? I focus on scientific expert networks in the global North, and the aims, epistemologies, and effects of their assessment practices. Secondly: What does this knowledge do (Chapters 2, 3, 4, and 5)? I examine how assessment practices set in play resonant terms and frames of reference that actively – if imperfectly – steer climate governance in their image. Thirdly: How can this knowledge be used to bridge differences (Chapters 5 and 6)? I move from how knowledge is constructed to focusing on that construction as a form of experimentation – engaging with different expert networks and knowledge types to use assessment practices as platforms exploring new directions for research and policy. The chapters represent three directions. The first is from analytical to engagement work, using critical mappings of the knowledge economy to inform bridging activities amongst experts and stakeholders. The second is from retrospective to generative work – from analysis of how knowledge is constructed, to activities that use the future as a sandbox to generate new knowledge, and that in turn shape assessments. The final direction moves from general technological categories to specific approaches – engaging first with the wider politics of planetary interventions, and then with those of particular approaches and their expert networks. I begin with interpretive reviews. Tools of the Trade (Chapter 2) juxtaposes a mission-oriented mode of assessment prioritizing actionable evidence for policy audiences against a deliberative mode aiming for open-ended appraisal with diverse stakeholders. The Practice of Responsible Research and Innovation (Chapter 3) takes a more critical look at deliberative activities, pointing out that these, by setting themselves up against mission-oriented work, engage in the same implicit and instrumental politics of knowledge-making. Delaying Decarbonization (Chapter 4) examines the longer and wider arc of climate governance, treating sunlight reflection and carbon removal as sociotechnical strategies that draw on the same political rationales that have informed a host of antecedent strategies, from market mechanisms and carbon capture to shale gas and short-lived climate pollutants. I conclude with bridging and generative engagements on particular approaches. Is Bioenergy Carbon Capture and Storage Feasible? (Chapter 5) engages members of integrated assessment modeling groups and a multi-disciplinary group of critical experts, and finds that perspectives on how the ‘feasibility’ of novel climate options should be calculated are actually reflections on the influence of economic modeling work in climate policy. Engineering Imaginaries (Chapter 6) engages scholars invested in early conversations on the risk profiles and appropriate governance of a planetary form of sunlight reflection, and explores the value of anticipatory foresight approaches to create mutual learning amongst entrenched perspectives, and to generate governance that might be robust against many future plausibilities.

In this interview, Dominic Woolf, a senior research associate at Cornell University, describes a potential method for removing excess carbon dioxide from the atmosphere: converting biomass ...

The separation of acetylene, ethylene, and carbon dioxide is a great challenge in view of their similar sizes and physical properties. Recently, adsorptive separations using porous metal–organic fr...

Dual fluidized bed steam gasification is a well-known technology for the thermochemical conversion of biogenic fuels into a valuable product gas comprising hydrogen, carbon monoxide, carbon dioxide, and methane. Based on the dual fluidized bed gasification principle, further benefits can be obtained by considering the bed material: Limestone allows the removal of carbon dioxide from the gasification reactor and its release in the combustion reactor. Therefore, the gasification and combustion reactors must be operated at 650 °C and 830 °C, respectively. Moreover, this sorption enhanced reforming process affords hydrogen contents of ~70 vol.-%db and allows an adjustment of the hydrogen-to-carbon monoxide ratio in the range of 2–10. The circulating bed material undergoes carbonation and calcination cycles, that lead to a decrease in the carbon dioxide sorption capacity with time. This paper discusses the main reasons for this decrease as well as the positive or negative effects of steam and carbon dioxide. The major disadvantage of using limestone in the fluidized beds is its low attrition resistance. Thus, gentle separation units for the limestone as bed material are recommended to overcome this problem. Several process configurations have been published by different institutions, mainly by IFK Stuttgart and TU Wien. The most important experimental and theoretical results, including the dependence of the product gas composition on the gasification temperature and the bed material cycle rate, tar content in the product gas, and test runs in the industrial scale are summarized and discussed. Sorption enhanced reforming of different fuel types, sorption enhanced reforming with oxyfuel combustion, and performance indicating key figures of the process are also investigated.

Engineered carbon dioxide (CO2) removal technologies—such as direct air capture (DAC) and bioenergy with carbon capture and sequestration (BECCS)—require significant advancements to reduce costs and increase scale without environmental or social harm. Up until this point, advancements in BECCS and DAC technologies have progressed independently of each other, despite the ability of BECCS to provide carbon-negative heat and power to DAC processes. Here, we demonstrate synergistic integration of BECCS and DAC systems decreases costs, increases carbon removal, and extends the impact of scarce biomass resources. We estimate biomass integrated DAC systems can increase net CO2 removal by 109–119% at lower costs than standalone reference systems. If hybrid BECCS–DAC systems were deployed across the US using biomass resources co-located with geologic storage, 1.5 Gt of CO2 could be sequestered annually without long-distance biomass or CO2 transport in 2030. Innovation in the design and implementation of coupled BECCS–DAC systems would have a profound impact on CO2 removal, if realized.

Reducing CO2 emissions for addressing climate change concerns is becoming increasingly important as the CO2 concentration in the atmosphere has increased rapidly since the industrial revolution. Carbon capture and storage is the process of capturing waste carbon dioxide (CO2) from large point sources, such as fossil fuel power plants, transporting it to a storage site, and depositing it where it will not enter the atmosphere, normally an underground geological formation. The aim is to prevent the release of large quantities of CO2 into atmosphere. This paper aims at manufacturing of a simple and useful unit of capture the carbon dioxide. The air with carbon dioxide is made to flow through the reaction chamber using an axial flow fan and NaOH is sprayed using a nozzle. The NaOH reacts with CO2 and form Na2CO3, and is collected in a tray. The maximum absorption rate of CO2 is found to be at NaOH solution molar concentration of 5.

In the present work, a dynamic mass-transfer model of the microalga Chlorella vulgaris flue gas sequestration system is proposed. Rate-based model emphasizes on the flue gas utilization as an input carbon source. Model is designed to simulate carbon dioxide (CO2) mitigation in the microalgal semi-batch cultures continuously supplied with the real flue gas. Model is a mass balance based, and accounts for transport properties, thermodynamics, and absorption kinetics. Model is built-up of three equations describing the mass balances of the biomass and CO2 in the gas and liquid phases. Coupled equations of the model were solved with MATLAB and Simulink with the defined initial conditions and model parameters. Model was calibrated and validated with the experimental results from the cultured C. Vulgaris. Proposed model is an applicable tool for designing and controlling the biological CO2 fixation facilities using microalga cultures. Moreover, the model permits monitoring of the CO2 concentration in the gas and liquid phases. Proposed model shows that by manipulating the CO2 supply, the microalga C. Vulgaris culture has the potential of sequestration through the greenhouse gases on demand from source points. Keywords: Flue gas sequestration, Chlorella vulgaris, Growth rate modeling, Elimination capacity, Global warming

Carbonation of industrial wastes rich in earth-alkali oxides is found to have a significant potential for CO2 sequestration. This process opens new perspectives not only for carbon dioxide mitigation, but also for the valorization and new applications of industrial waste materials from coal-burning power plants. In this study, mineral carbonation of high–calcium fly ash is investigated under dry and moist conditions in a continuous flow reactor during up to 2 h, at temperatures ranging from 160 to 290 °C and CO2 pressures between 1 and 6 bar. A comprehensive characterization of treated and untreated samples was carried out before and after carbonation using X-ray diffraction, X-ray fluorescence spectroscopy, thermogravimetric analysis, infrared spectroscopy and scanning electron microscopy. The maximum sequestration capacity achieved was 117.7 g CO2/kg fly ash (48.14% carbonation efficiency) under dry conditions. Results showed that increasing the pressure and temperature enhances the process of carbonation, as well as the presence of moderate amounts of water vapor in the CO2 gas flow. Newly formed carbonates were always present in the treated samples. This study shows that about 21% of all CO2 emissions of a coal-burning power plant could potentially be sequestered as carbonates.

Biomass can be converted into a range of different end-products; and when combined with carbon capture and storage (CCS), these processes can provide negative CO2 emissions. Biomass conversion technologies differ in terms of costs, system efficiency and system value, e.g. services provided, market demand and product price. The aim of this study is to comparatively assess a combination of BECCS pathways to identify the applications which offer the most valuable outcome, i.e. maximum CO2 removal at minimum cost, ensuring that resources of sustainable biomass are utilised efficiently. Three bioenergy conversion pathways are evaluated in this study: (i) pulverised biomass-fired power plants which generate electricity (BECCS), (ii) biomass-fuelled combined heat and power plants (BE-CHP-CCS) which provide both heat and electricity, and (iii) biomass-derived hydrogen production with CCS (BHCCS). The design and optimisation of the BECCS supply chain network is evaluated using the Modelling and Optimisation of Negative Emissions Technology framework for the UK (MONET-UK), which integrates biogeophysical constraints and a wide range of biomass feedstocks. The results show that indigenous sources of biomass in the UK can remove up to 56 Mt CO 2 /yr from the atmosphere without the need to import biomass. Regardless of the pathway, Bio-CCS deployment could materially contribute towards meeting a national CO2 removal target and provide a substantial contribution to a national-scale energy system. Finally, it was more cost-effective to deploy all three technologies (BECCS, BE-CHP-CCS and BHCCS) in combination rather than individually.

Despite recent efforts to reduce carbon dioxide emissions, scientists still project that we will not avoid dangerous climate change. Models that calculate that we can avoid this result almost exclusively rely upon carbon dioxide removal options to stay below this level of warming. Although a number of CDR technologies are theoretically possible, they all have limitations. More germane here, they all remain far from the level of development and installation required.

Scientists increasingly agree that carbon dioxide removal will be needed, alongside deep emissions cuts, to stave off the worst impacts of climate change. A wide variety of technologies and strategies have been proposed to remove carbon dioxide from the atmosphere. To date, most research has focused on terrestrial-based approaches, but they often have large land requirements, and may present other risks and challenges. As such, there is growing interest in using the oceans, which have already absorbed more than a quarter of anthropogenic carbon dioxide emissions, and could become an even larger carbon sink in the future. This paper examines the international and U.S. legal frameworks applicable to two ocean-based carbon dioxide removal strategies—ocean alkalinity enhancement and seaweed cultivation. Ocean alkalinity enhancement involves adding alkalinity to ocean waters, either by discharging alkaline rocks or through an electrochemical process, which increases ocean pH levels and thereby enables greater uptake of carbon dioxide, as well as reducing the adverse impacts of ocean acidification. Seaweed cultivation involves the growing of kelp and other macroalgae to store carbon in biomass, which can then either be used to replace more greenhouse gas-intensive products or sequestered.

A possible approach to the carbon dioxide removal from flue gases is application of the dense composite membrane (matrix: polymer material; dispersed phase: zeolite powder). This type of membrane is based on a solution-diffusion mechanism. Carbon dioxide is dissolved in the membrane bulk, and then diffuses to the permeate side. A successful membrane should have high permeability of the carbon dioxide and low permeability for all other gasses commonly present in the combustion process (oxygen, nitrogen, hydrogen…). The main challenge is to provide good contact between long and usually hydrophobic polymer chains and relatively small, but electrically charged, zeolite particles. Two different polymers and four different zeolites were tested for this purpose. As the polymer bulk material, different co-polymers of ethylene-oxide and phthalimide were used. Five different zeolite powders in combination with two different potential additives were tested.

The rising of greenhouse-gas emissions (GHG), during the last 200 years, is associated to the well known global warming phenomena. One of the main sources of CO2-equivalent GHGs emissions are the environmental protection plants accounting for 1.57% of the global emissions and thus sustainable and effective technologies for their mitigation are strongly needed. The current paper presents and discusses the assessment of an innovative membrane photo-bioreactor (MPBR) whose aim was the promotion of CO2 capture from conveyed flows, such as those from wastewater treatment plants (WWTPs), landfill and composting plants, for production and energy valorisation of algal biomass. Chlorella vulgaris microalgae strain was selected as photosynthetic platform for the abovementioned purposes. The influence of various operating parameters has been explored, including the photosynthetic photon flux densities (PPFD) (60 and 120 μmol m−2 s−1), liquid/gas ratio (L/G = 5, 10 or 15) and CO2 concentration (5, 10 and 15%) in order to investigated their effects on carbon capture effectiveness and biomass production. The results demonstrated that the increasing of PPFD significantly enhanced the biomass production in terms of biomass productivity (P) and total dry weight (DW). The highest biomass concentration of 1.01 g L−1 was achieved at PPFD of 120 μmol m−2 s−1 with a L/G of 15. Under the aforementioned conditions, carbon dioxide removal efficiency (RE) reached values up to 80%. In addition, the novel MPBR equipped with an innovative self-forming dynamic membrane (SFDM) showed a simultaneous biomass harvesting rate of 41 g m−2 h−1.

The large majority of climate change mitigation scenarios that hold warming below 2 °C show high deployment of carbon dioxide removal (CDR), resulting in a peak-and-decline behavior in global temperature. This is driven by the assumption of an exponentially increasing carbon price trajectory which is perceived to be economically optimal for meeting a carbon budget. However, this optimality relies on the assumption that a finite carbon budget associated with a temperature target is filled up steadily over time. The availability of net carbon removals invalidates this assumption and therefore a different carbon price trajectory should be chosen. We show how the optimal carbon price path for remaining well below 2 °C limits CDR demand and analyze requirements for constructing alternatives, which may be easier to implement in reality. We show that warming can be held at well below 2 °C at much lower long-term economic effort and lower CDR deployment and therefore lower risks if carbon prices are high enough in the beginning to ensure target compliance, but increase at a lower rate after carbon neutrality has been reached., Many trajectories for reaching climate change mitigation targets exaggerate the long-term need for CO2 removal (CDR) because they assume an exponentially increasing carbon price. Here the authors analyse alternative carbon price pathways that halt warming while limiting CDR, and may be easier to implement.

The [hmim][Tf2N] ionic liquid is considered in this work to develop a model in Aspen Plus® capturing carbon dioxide from shifted flue gas through physical absorption. Ionic liquids are innovative and promising green solvents for the capture of carbon dioxide. As an important aspect of this research, optimization is carried out for the carbon capture system through a central composite design: simulation and statistical analysis are combined together. This leads to important results such as the identification of significant factors and their combinations. Surface plots and mathematical models are developed for capital costs, operating costs and removal of carbon dioxide. These models can be used to find optimal operating conditions maximizing the amount of captured carbon dioxide and minimizing total costs: the percentage of carbon dioxide removal is 93.7%, operating costs are 0.66 million €/tonCO2 captured (due to the high costs of ionic liquid), and capital costs are 52.2 €/tonCO2 captured.

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.

Carbon dioxide removal (CDR) represents a suite of pathways to remove carbon dioxide from the atmosphere and mitigate climate change. The importance of CDR has expanded in recent years as emission reductions are not at pace to meet climate goals. This CDR-themed issue brings together diverse perspectives in order to identify opportunities to integrate across CDR disciplines, create a more holistic research agenda and inform how CDR is deployed. The individual papers within the issue discuss engineered and nature-based CDR approaches as well as the broader social and behavioural dimensions of CDR development and deployment. Here, I summarize the main take-aways from these individual papers and present a path for integrating key lessons across disciplines to ensure CDR is scaled equitably and sustainably to deliver on its climate mitigation promise.

A comparison between electrochemical carbon dioxide conversion and reforestation is presented. By comparing thermodynamic and forestry data, recommendations for technology development can be made. With the global average temperature steadily increasing due to anthropogenic emission of greenhouse gases into the atmosphere, there has been increasing interest worldwide in new technologies for carbon capture, utilization, and storage (CCUS). This coincides with the decrease in cost of deployment of intermittent renewable electricity sources, specifically solar energy, necessitating development of new methods for energy storage. Carbon dioxide conversion technologies driven by photovoltaics aim to address both these needs. To adequately contribute to greenhouse gas reduction, the carbon dioxide conversion technology deployed should have a substantially higher rate of carbon dioxide removal than planting an equivalent-sized forest. Using consistent methodologies, we analyze the effectiveness of model photovoltaic-driven carbon dioxide conversion technologies that produce liquid alcohols as compared to planting an equivalent forest. This analysis serves to establish an energy use boundary for carbon dioxide conversion technology, in order to be a viable alternative as a net carbon negative technology.

We show how to determine the amount of carbon to remove to affect the cumulative emitted anthropogenic carbon dioxide in order to create Carbon Dioxide Removal (CDR) targets, additionally, compare ...