CO2 Removal Research Articles

Life cycle assessment of carbon dioxide removal and utilisation strategies: Comparative analysis across Europe

Anthropogenic climate change necessitates urgent implementation of carbon dioxide (CO2) removal and utilisation strategies. While the CO2 removal efficiency of such strategies is commonly evaluated, their environmental impacts beyond CO2 emissions needs consideration to avoid burden shifting. This study performs a life cycle assessment of CO2 removal and utilisation strategies in ten specific European locations. The study considers strategies such as direct air carbon capture, permanent storage, the production of fuels and polymers. The energy source, CO2 transport distances, transport mode (pipeline and ship) and the CO2 storage medium vary between the locations. Results indicate that seven of the ten considered locations have a CO2 removal efficiency greater than 95%. In addition, the hotspot analysis indicates CO2 capture and its transport contribute to between 0.3% and 13.1% of global warming impacts of polymer production and between 0.4% and 16.5% for fuel production (varies based on the polymer and fuel type).

Hysteresis of Northern Hemisphere permafrost to carbon dioxide emissions

Abstract Carbon dioxide removal (CDR) is proposed to limit the level of global warming and minimize the impacts of climate crises. However, how permafrost may respond to negative carbon emissions remains unknown. Here, the response of near-surface permafrost in the Northern Hemisphere is investigated based on idealized carbon dioxide (CO2) ramp-up (284.7–1138.8 ppm) and symmetric ramp-down model experiments. The results demonstrate that the timing of the minimum permafrost area lags the maximum CO2 concentration for decades, which is also observed in soil temperatures at different depths and active layer thicknesses. When the CO2 concentration is reversed to the preindustrial level, the permafrost area decreases by ~12% relative to the initial conditions, together with additional warming in the ground temperature at the top of the permafrost, indicating the hysteresis of permafrost to CO2 removal. The most profound hysteretic responses occur at high latitudes for soil temperatures owing to Arctic amplification, while at the southern margins of the permafrost zones for permafrost and active layer thickness that largely linked to the climate state. Moreover, the sensitivity of permafrost and the associated thermodynamic factors to CO2 change is generally lower during the CO2 ramp-down phase than during the ramp-up phase, likely due to the release of stored heat on land. The results reveal the behaviour of permafrost in response to negative carbon emissions, which is informative for the projections of permafrost towards carbon neutral targets. In addition, the results may provide a reference for permafrost-related tipping points (e.g., releasing long-term stored greenhouse gases and destabilising recalcitrant soil carbon) and risk management in the future.

(Invited) Electrochemical Marine Carbon Dioxide Removal (mCDR)

Ebb Carbon is developing an electrochemical system to safely remove carbon dioxide from the atmosphere and store it in the ocean as dissolved inorganic carbon. The core process uses bipolar electrodialysis (BPED) to process incoming seawater into aqueous acid and alkaline seawater. The acid is kept on land and used for beneficial purposes that result in its neutralization. The alkaline seawater is returned to the ocean, shifting the carbonate buffer system toward carbonate, resulting in the removal of CO2 from the air into oceanic bicarbonate as air-sea equilibration is restored.For the mCDR system to be impactful on a global level, it must reach gigaton scale while being energy efficient and cost effective.The BPED stack dominates the energy demand of the system and is a prime design task for Ebb Carbon. The stack and system are undergoing development and testing in Ebb Carbon’s labs as well as at the labs of institutional partners. Combining all of these system elements requires a multitude of scientific and engineering disciplines to work together. In this talk, I will discuss the potential for improving the energy and Faradaic efficiencies of these systems, including the opportunity for collaboration with the electrochemical research community.

Continuous Direct Air Capture and Electrochemical Conversion of CO2 and H2O into Ethylene and Oxygen in Solid Electrolyte Reactor

Chemelectronics LLC has developed economical approach to use solar energy to convert CO2 directly captured from air using carbon dioxide capture conductive sorbent materials coated on carbon foam electrodes into chemical products (ethylene) and oxygen from nick foam electrodes separated with solid polyelectrolytes. We take advantage of commercial off-the-shelf solar panels as electricity to supply the electrochemical reduction of CO2 directly captured from air into chemical products with zero carbon emission.Based on the life cycle analysis, there is no CO2 emission from CO2 capture and conversion. The energy will be produced from solar panels.

Design and Implementation of Iron-Based Electrochemical System for Simultaneous Carbon Capture and Hydrogen Gas Recovery

The catastrophic results of climate change and energy crisis, such as the rise in wildfires, floods, and ecosystem disruptions highlight the critical need of urgent and innovative global-scale solutions for carbon dioxide (CO2) removal (CDR). Ocean-based CDR methods, leveraging the ocean's capacity as a large sink to sequester up to 30% of emissions, offer a great promise. Yet, implementing and testing marine CO2 removal (mCDR) techniques such as ocean iron fertilization (OIF) or ocean alkalinity enhancement (OAE) face significant challenges. To overcome these challenges, a novel self-operating electrochemical technology is designed and presented in this work. The proposed technology, namely electrochemical OIF (EOIF), does not only combine OIF and OAE, but also recovers hydrogen gas (H2) from seawater, offering a promising solution for achieving quantifiable and transparent large-scale mCDR. The EOIF design s focused on employing Fe/Fe-producing anodes to eliminate the production of acids at the anode in traditional electrochemical OAE systems and replace it with Fe release, where the cathode can be made from naturally abundant cost-effective materials, such as carbon. The obtained results show that the EOIF system can be implemented to increase both the concentration of ferrous iron (Fe+2) by 0-0.5 mg/L, and the seawater pH by 8% (i.e., 25% decrease in the hydrogen ions concentration). It also offers the flexibility to optimize the release of iron (Fe+2/Fe+3) by adjusting the magnitude of the electric current in the systems, as well as by optimizing the electrode material and geometry. In certain ocean regions, enhanced iron concentrations stimulate the naturally occurring biological carbon pump (BCP), leading to increased phytoplankton growth, CO2 uptake, and subsequent export of carbon to the deep ocean. Simultaneously, the system increases seawater alkalinity and the buffer capacity, enhancing CO2 solubility and storage in the shallow ocean through the solubility pump. The techno-economic assessment shows that the combined advantages of the EOIF system can lower the mCDR cost by more than 95% compared to the traditional methods. The obtained measurements demonstrate the scalability of EOIF and its ability to operate using solar energy at a lower cost. Overall, the proposed EOIF technology offers a practical, effective, and sustainable solution for addressing climate change and energy recovery on a large-scale.

CO2 Uptake and Stability Enhancement in Vinyltrimethoxysilane-Treated SBA-15 Solid Amine-Based Sorbents.

Silica-supported amine absorbents, including materials produced by tethering aminosilanes or infusion of poly(ethyleneimine), represent a promising class of materials for CO2 capture applications, including direct air and point source capture. Various silica surface treatments and functionalization strategies are explored to enhance stability and CO2 uptake in amine-based solid sorbent systems. Here, the synthesis and characterization of novel vinyltrimethoxysilane-treated Santa Barbara Amorphous-15 (SBA-15) supports and the corresponding enhancement in CO2 uptake compared to various SBA-15-based control supports are presented. The relationship between CO2 diffusion and amine efficiency in these systems is explored using a previously reported kinetic model. The synthesized materials are characterized with CO2 and H2O isotherms, diffuse reflectance infrared Fourier transform spectroscopy, 1H T1-T2 relaxation correlation NMR, and rapid thermal cycling experiments. The novel support materials are shown to enable high amine efficiencies, approaching a fourfold improvement over standard SBA-15-supported amines, while simultaneously exhibiting excellent stability when cycled rapidly under humid conditions. As the poly(ethyleneimine) loadings are held constant across the various samples, enhancements in CO2 uptake are attributed to differences in the way the poly(ethyleneimine) interacts with the support surface.

Observing Electrochemical Performance Trends with the Physical Scaling of Bipolar Membrane Electrodialysis for the Capture and Concentration of Atmospheric CO2

Bipolar membrane electrodialysis (BPMED) is a proven technology for separating ionic species driven by electrochemical potential through ion conductive membrane separators. When using a bipolar membrane (BPM) as the separator, a pH gradient is created by the generation of acid and base via water dissociation at the internal interface of an anion conductive and a cation conductive membrane. BPMED can been used for the capture and concentration of atmospheric CO2, for example when using a liquid alkaline capture sorbent, where the acidification of the capture stream can be used to regenerate pure CO2 while further basification of the remaining effluent regenerates the alkaline capture sorbent to be re-used in the direct air capture process. Current commercial BPMs require high overpotentials to drive water dissociation and can only operate at low to moderate current densities. While considerable work has gone into the development of efficient, electrochemically active BPMs through improved membrane polymer chemistries and high-activity water dissociation catalysts, little work has been done to physically scale up these materials and use them in electrodialysis-driven carbon capture and concentration systems beyond lab scale (i.e., >1 cm2).In this presentation, we will report a scalable BPMED cell that can sense the resistive contributions of the individual membrane components (i.e., the anion exchange and cation exchange membranes, and the water dissociation at the internal BPM interface) with increasing membrane active area from 1 cm2 to 25 cm2. With this BPMED cell, changes in the BPM and water dissociation catalyst compositions and structures are related to electrochemical performance metrics (overpotential and CO2 recovery efficiency) at increasing physical scales. Electrochemical impedance spectroscopy (EIS) was used to reveal resistive contributions to the cell at increasing active area, while the inlet and outlet pH were measured to confirm the overall acidification and basification of the dialysis cell to promote carbon capture and conversion, as well as sorbent regeneration. This study aims to build a bridge between the necessary improvements in the membrane and water dissociation catalyst compositions with industrially relevant energy efficiency and conversion performance, accelerating the development of high performance BPMs.

(Invited) EDAC Labs: Carbon Removal via Acid-Base Electrochemistry

EDAC Labs(https://edaclabs.com/) uses the electrochemical production of acid and base to decarbonize the world through conventional direct air capture, enabling carbon-negative mining, and by providing technology for other applications such as direct ocean capture, ocean alkalinity enhancement, and enhanced weathering. EDAC Labs’ electrosynthesizer device creates acid and base at reduced energy cost of conventional processes. For conventional direct air capture developers, EDAC Labs provides technology that is low cost and operates at ambient temperature and pressure. For direct ocean capture and ocean alkalinity enhancement developers, EDAC Labs supplies electrochemistry solutions to developers that lower project costs. For metal mines, EDAC Labs provides technology that extracts valuable metals while sequestering carbon to achieve carbon-negative mining. The acid is used to start the recovery of valuable metals from mine tailings, and the base is used to capture CO2 from air. The acid and base streams are then combined to extract metals that can be sold for applications such as batteries, and to create solid carbonates, which permanently store CO2. Figure 1

Minimize Energy Consumption of CO2 Release in a Flow Electrolyzer By Optimizing Direct Air Capture Solvents

Under the 2015 Paris Agreement, almost 200 nations have committed to the global goal of limiting the rise in average temperatures to 2.0 °C above preindustrial levels, with an even more ambitious aim of striving for 1.5 °C. Achieving the 1.5 °C objective requires a 45% reduction in global greenhouse gas emissions by 2030, ultimately reaching net-zero emissions by 2050. Numerous industries are increasingly making commitments to combat climate change by minimizing their CO2 emissions. However, certain sectors face challenges due to the current high costs associated with emissions reduction through available technologies, though these costs are expected to decrease over time. Moreover, in specific industries like cement production, there are emissions sources that cannot be entirely eliminated, such as those arising from the inherent calcination process. Given these constraints, realizing the emissions reduction pathway to the 1.5 °C target requires the adoption of negative emissions processes, including technologies like direct air capture (DAC), to actively remove CO2 from the atmosphere.The operational concept of the DAC process explored in this study is based on the utilization of both the solvent-based method and alkaline water electrolysis. This involves regenerating the solvent through pH fluctuations generated by a carbonate electrolyzer. As depicted in Figure 1, the consumption of OH- ions during O2 evolution leads to a decrease in pH at the anolyte loop, while the production of OH- ions through water splitting causes an increase in pH at the catholyte loop. Consequently, the lowered pH environment facilitates the release of CO2 gas from dissolved carbon species such as CO32-, while the heightened pH environment promotes the formation of alkaline hydroxides for carbon capture in an air absorber.In this work, we will aim to analyze the energy consumption per mole of CO2 released from the anolyte loop of a flow electrolyzer. Utilizing a combination of theoretical predictions and experimental validations, significant insights were obtained for optimizing the DAC solvent. This optimization involves minimizing energy consumption by adjusting alkalinity levels and incorporating supporting electrolytes. Figure 1

Carbonate Electrolysis for Energy Efficient Direct Air Capture of CO2

Yearly global energy related CO2 emissions continue to increase, reaching a record breaking 37 billion metric tons in 2022. As a major greenhouse gas, CO2 levels need to be reduced by 10s of gigatons to prevent the worst of climate change, something that is no longer feasible with net-zero emissions alone. Removing atmospheric CO2 is therefore of critical importance for the future of our planet. While major improvements have been made in CO2 capture from large point sources, a significant portion of CO2 emitted each year from the United States comes from distributed sources such as cars and smaller factories. Due to the dilute concentrations of CO2 in ambient air, Direct Air Capture (DAC) needs to be highly selective to preferentially absorb CO2 to collect useable amounts. These challenges have made current DAC systems quite costly, both energetically and economically, and require vastly different strategies than carbon capture from concentrated sources.At Giner, we are developing a novel process for the capture and regeneration of CO2 from air into a purified, concentrated CO2 stream that can be redirected as a feedstock for a wide range of applications, including chemical manufacturing and syngas formation. This process involves the capture of CO2 in a concentrated KOH solution using a high-surface area air contactor to form potassium carbonate. The potassium carbonate is then efficiently electrolyzed in a hydrogen-assisted process to regenerate the CO2 at a low operating potential, increasing the electrical efficiency of the process while producing concentrated and purified CO2. In addition, water, hydrogen, and KOH are also regenerated as byproducts that can be recycled back into the CO2 capture and electrolysis processes, reducing both overall energy and chemical consumption.Giner has developed a unique 3-compartment carbonate electrolysis flow cell. Using our electrolyzer, we have seen operating voltage as low as 1.2 V at 100 mA/cm2 in a 5 cm2 cell for potassium carbonate conversion to CO2 with H2 assisted electrolysis. Significant improvements in operating voltage have come from optimization of gas-diffusion layers (GDLs), cell geometry, and membrane selection. Furthermore, we have achieved >97% pure CO2 formation in the internal flow-through compartment. Currently, scale-up is in progress to apply these developments to approach comparable conditions in a 50 cm2 multi-cell stack. Further developments will enable pairing with an in-house, carbonate based, air contactor allowing for capture and regeneration of over 1 ton CO2 per year. Acknowledgement: The project is financially supported by the Department of Energy's ARPA-E Office under the Grant DE-AR0001495

Understanding Electrochemical and Mechanical Durability of Bipolar Membranes Used in Electrodialysis

Using renewable energy to drive direct carbon capture systems is a powerful way to contribute to net negative emissions. When using liquid alkaline sorbents for CO2 direct air capture, it is critical to reduce the energy demand for CO2 concentration and sorbent regeneration. Electrodialysis is an ideal candidate technology to integrate renewable energy into this process, however, to enable this ion-exchange membrane separators that can operate at high ion flux and low voltage are needed. Bipolar membranes (BPMs), that generate protons and hydroxide ions from the dissociation of water when operated in reverse bias, are the enabling component to generate acid and base in electrodialysis systems. Bipolar membrane electrodialysis (BPMED) uses a BPM to create acidifying and basifying chambers which are well suited to concentrate and release CO2 and concentrate the remaining alkaline effluent to cycle back to the capture process. Current BPM durability, however, sufferers at high current density (ion flux) and physical scale. BPMs have several known degradation mechanisms including chemical breakdown of ion exchange polymers, loss of junction adhesion, or physical breakdown due to shearing force and pressure swings in an electrodialysis cell.To assess the electrochemical and mechanical durability of BPMs under operational conditions, we investigated how fabrication conditions (including preconditioning, hot pressing, and catalyst loading) impact the adhesion of custom made BPMs. T-peel studies were performed ex-situ to quantify adhesive forces of BPMs made of different compositions and prepared under different conditions, and BPMED experiments were performed to assess the electrochemical performance of the corresponding BPMs. The BPMED results show that, while adhesion is necessary to physically maintain the BPM junction, mechanical adhesion alone cannot overcome poor ion and water transport management at the water dissociation junction. The results of this systematic comparison indicate that in order for BPMs to operate at high current densities, high adhesion forces made during fabrication of BPMs will need to be balanced with water dissociation kinetics and ion/water transport through the individual membrane layers.

Optimizing Air Contactor Design for Efficient Carbon Capture in Direct Air Capture Systems: A Multi-Disciplinary Approach

As carbon dioxide (CO2) emissions continue to rise, direct air capture (DAC) has emerged as an important technology for removing CO2 from ambient air to combat climate change. The air contactor design is a critical factor impacting DAC system performance and costs. This research describes a strategy for improving the design of a single air contactor unit to increase CO2 capture flux while minimizing costs using optimization techniques grounded in experimental data .The research focuses on a 100 m2 slab air contactor modeled utilizing cooling tower and scrubber principles. The system includes the chemical, mechanical, and structural engineering disciplines. The mass transfer coefficient, air velocity, packing depth, and capital cost per frontal area are four major design characteristics that were maximized.The model integrated requirements for low air velocity, pressure drop, and energy consumption, as well as adequate gas-liquid interaction via structured packing selection and depth.The design space was explored using a multi-objective optimization strategy based on gradient-based and heuristic methods. Initial sampling via a design of experiments methodology demonstrated response surface trends in the objective function across the design space. The response surfaces mapped the optimization objective as a function of the design variables. Using gradient information, sequential quadratic programming efficiently located an optimal design vector that met all constraints on the design variables and feasibility requirements. The constraints included bounds on mass transfer coefficient, air velocity, packing depth, and capital cost per frontal area. The optimized air contactor design achieved a CO2 capture flux of 10,440 kg/m2-yr at a cost of $ 0.068 per kg CO2 captured. The developed optimization framework maximizes contactor performance while decreasing operational costs. A multi-objective genetic algorithm approach was used to identify the trade-offs between the two competing objectives of maximized CO2 capture and minimized cost by expanding the formulation. The Pareto-optimal front of the optimization results offered numerous optimized solutions with specific DAC system setups. This methodology, as well as the optimum configurations identified, serve as the foundation for constructing larger-scale DAC systems, in future. Ongoing research aims to improve solution approaches by including advanced optimization software packages such as DAKOTA, which offers global optimization algorithms, as well as to boost model accuracy via integrating additional choice variables. Future optimization and modeling studies will include contactor interactions and the modeling of a full DAC facility to boost confidence that a globally optimal design has been established.Overall, this study illustrated an efficient optimization strategy for air contactor design and contributes to the improvement of sustainable carbon capture technology, which is crucial to controlling rising global CO2 levels. Contactor configuration optimization enables superior DAC system designs at lower costs, hence promoting the urgent deployment of negative emissions solutions.

A digital-twin for rapid simulation of modular Direct Air Capture systems

There has been tremendous recent interest in Direct Air Capture (DAC) systems. A key part of any DAC system are the multiple air intake units. In particular, the arrangement of such units for optimal capture and sequestration is critical. Accordingly, this work develops an easy to use model for a modular unit system, where an approximate flow field is computed for each unit and the aggregate flow field is developed by summing the fields from each unit. This allows for a modular framework that can be used for rapid simulation and design of an overall DAC system. The rapid rate at which these simulations can be completed enables the ability to explore inverse problems seeking to determine which parameter combinations can deliver the maximum sequestration of tracer plume particles for the minimum amount of energy input. In order to cast the objective mathematically, we set up an inverse as a Machine Learning Algorithm (MLA); specifically a Genetic MLA (G-MLA) variant, which is well-suited for nonconvex optimization. Numerical examples are provided to illustrate the framework.

From carbon neutral to carbon negative: a theoretical bioenergy and CO2 removal retrofit at Ngāwhā geothermal power station

ABSTRACT For countries like New Zealand with high renewable electricity generation (≥80%) but large emissions per capita, traditional decarbonisation methods are limited or costly. However, carbon dioxide removal (CDR) technologies can drive multiple sectors of the economy across the net-zero barrier through negative CO2 emissions. We argue that the key to scaling up CDR begins with the preponderance of New Zealand’s geothermal and biomass resources. New Zealand has a proud and innovative history with geothermal energy, currently producing ∼20% of the country’s electricity. Modern advances in geothermal energy have demonstrated that it is peerless amongst renewable energy-sources in the ability to facilitate onsite CDR by repurposing existing wells. We examine a theoretical bioenergy retrofit at the Ngāwhā geothermal plant to increase capacity by 1 MWe, with as much biogenic CO2 as permissible dissolved in reinjectate. Forestry residues are the feedstock of choice due to their abundance in the Far North. We show that up to 15.9 ktCO2/year can be removed effectively from the atmosphere. Only 6% of the Far North’s forestry residues are required to achieve this. Under 2024s emissions trading scheme (ETS), the annual revenue of CDR ($0.79 million) could exceed that of new electricity ($0.47 million).

Relevance of surface albedo to forestry policy in high latitude and altitude regions may be overvalued

Abstract Forest restoration and improved forest management are seen as options to enhance terrestrial carbon dioxide removal in many regions, yet concerns surrounding their potentially adverse surface albedo impacts exist, particularly in high latitude and altitude regions. Such concerns are often based on generalized conclusions rooted in analyses carried out over broad spatial extents at coarse resolutions. The impacts of surface albedo change are highly sensitive to local environmental factors governing both the surface albedo and solar radiation budgets, and many previous assessments either do not sufficiently deal with such sensitivities or do not qualify the conditions under which they are relevant. Using the country of Norway with its diverse gradients in topography and climate as an ideal case study region, we seek clarity to the question of whether surface albedo is relevant to consider in forestry planning, and if so, what are the important factors determining it. We find that the adverse impact of a forest’s albedo outweighs its carbon cycle benefit on only ∼4% of Norway’s total forested area, reducing to <∼1% when future climate changes are considered. Our findings challenge the common perception that surface albedo concerns are highly relevant to forestry planning at high latitudes and emphasize the importance of carrying out albedo impact assessments at spatial scales aligning with those of local forestry planning.

Policy support for BECCS and DACCS in Europe: the view of market participants

Abstract Carbon dioxide removal (CDR) is the essential ‘net’ in net zero. However, a thriving CDR industry will not come into being without government intervention. As governments start to devise CDR support policies, this paper solicits the views of market participants in two of the most prominent CDR methods: bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS). We survey 47 BECCS and DACCS project developers and financiers active in Europe, conducting in-depth interviews with 27 of them to identify their key challenges and preferred policy interventions to address them. We find that participants prefer compliance markets, such as links to emissions trading systems, to generate demand but seek government support to cushion early market risks. They acknowledge the need for stringent monitoring and regulation to ensure environmental integrity. Bearing industry expectations in mind, policymakers face five key challenges in developing CDR: reaching scale, striking a balance with emissions cuts, safeguarding integrity, ensuring fairness and accelerating the speed of deployment.

Influence of RED‐II Calculation Rules on the Carbon Footprint of Methanol E‐Fuel

AbstractThe carbon footprint of methanol from cradle‐to‐grave is evaluated using three process concepts to capture CO2, i.e., one using CO2 from direct air capture (DAC) and the other two utilizing CO2 from a steel mill's blast furnace gas (BFG). Hydrogen is supplied by onsite electrolysis, or from a German offshore wind park, or an Australian solar park with ammonia as hydrogen carrier. The study is of interest to life cycle assessment (LCA) practitioners, policymakers, and industries’ management who are involved in regulating, planning, implementing, and operating projects which aim to produce fuels using hydrogen from electrolysis (so‐called ‘e‐fuels’). The influence of assumptions in the RED‐II delegated act regarding recycled carbon fuels and renewable liquid and gaseous fuels of non‐biological origin on the carbon footprint results is examined. The RED‐II assumption regarding the credits for captured CO2 after 2041 indicate that DAC‐based concepts are advantageous with respect to BFG, although the LCA results indicate the opposite. Using green hydrogen from nearby locations reduces carbon footprints more than faraway locations due to transport‐related emissions.

Physiological effects and safety of bed verticalization in patients with acute respiratory distress syndrome

BackgroundTrunk inclination in patients with Acute Respiratory Distress Syndrome (ARDS) in the supine position has gained scientific interest due to its effects on respiratory physiology, including mechanics, oxygenation, ventilation distribution, and efficiency. Changing from flat supine to semi-recumbent increases driving pressure due to decreased respiratory system compliance. Positional adjustments also deteriorate ventilatory efficiency for CO2 removal, particularly in COVID-19-associated ARDS (C-ARDS), indicating likely lung parenchyma overdistension. Tilting the trunk reduces chest wall compliance and, to a lesser extent, lung compliance and transpulmonary driving pressure, with significant hemodynamic and gas exchange implications.MethodsA prospective, pilot physiological study was conducted on early ARDS patients in two ICUs at CHU Clermont-Ferrand, France. The protocol involved 30-min step gradual verticalization from a 30° semi-seated position (baseline) to different levels of inclination (0°, 30°, 60°, and 90°), before returning to the baseline position. Measurements included tidal volume, positive end-expiratory pressure (PEEP), esophageal pressures, and pulmonary artery catheter data. The primary endpoint was the variation in transpulmonary driving pressure through the verticalization procedure.ResultsFrom May 2020 through January 2021, 30 patients were included. Transpulmonary driving pressure increased slightly from baseline (median and interquartile range [IQR], 9 [5–11] cmH2O) to the 90° position (10 [7–14] cmH2O; P < 10–2 for the overall effect of position in mixed model). End-expiratory lung volume increased with verticalization, in parallel to decreases in alveolar strain and increased arterial oxygenation. Verticalization was associated with decreased cardiac output and stroke volume, and increased norepinephrine doses and serum lactate levels, prompting interruption of the procedure in two patients. There were no other adverse events such as falls or equipment accidental removals.ConclusionsVerticalization to 90° is feasible in ARDS patients, improving EELV and oxygenation up to 30°, likely due to alveolar recruitment and blood flow redistribution. However, there is a risk of overdistension and hemodynamic instability beyond 30°, necessitating individualized bed angles based on clinical situations.Trial registration ClinicalTrials.gov registration number NCT04371016, April 24, 2020.

Assessment of the Potential of Electrochemical Steps in Direct Air Capture through Techno-Economic Analysis.

Direct air capture (DAC) technologies are proposed to reduce the atmospheric CO2 concentration to mitigate climate change and simultaneously provide carbon as a feedstock independent of fossil resources. The currently high energy demand and cost of DAC technologies are challenging and could limit the significance of DAC processes. The present work estimates the potential energy demand and the levelized cost of capture (LCOC) of liquid solvent absorption and solid adsorption DAC processes in the long term. A consistent framework is applied to compare nonelectrochemical to electrochemical DAC processes and estimate the LCOC depending on the electricity price. We determine the equivalent cell voltage needed for the electrochemical steps to achieve comparable or lower energy demand than nonelectrochemical processes. The capital expenses (CapEx) of the electrochemical steps are estimated using analogies to processes that are similar in function. The results are calculated for a range of initial data of CapEx and energy demand to include uncertainties in the data.

Comparative assessment of biochar produced from waste biomass in laboratory furnace and industrial screw reactor systems

Biochar is rapidly gaining traction as a commercially viable carbon dioxide removal (CDR) technology that can be applied globally at various scales. However, the vast majority of published research studies have involved laboratory experiments conducted in an inert environment under well-controlled conditions of heating rate, maximum temperature and residence time. To expand the biochar industry within the next decade as a CDR platform, there is a need to understand differences between biochar produced under “ideal” laboratory conditions versus those generated using the same feedstocks in continuous, industrial scale systems. In the present work, biochar was produced from widely available organic waste feedstocks, including mixed cafeteria food waste, blended coffee grounds and chaff, grape pomace and wood pellets, using both a laboratory furnace operated in a nitrogen environment, and a continuously operated commercial system capable of processing up to ∼1 t/day of dry feedstock. High quality biochar (H:C < 0.7) was obtained for all feedstocks converted by both systems, however high variability in volatiles and decomposition rates was observed in the thermogravimetric analysis (TGA) results for industrial scale biochar. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) showed similar morphologies and surface chemistries in both laboratory and industrial scale samples, in agreement with reported literature data. Based on this initial comparative assessment, we conclude that commercially available thermochemical systems have potential as localized organic waste valorization technologies to produce high quality biochar. We identified important control variables that have the greatest effect on the resulting biochar. Despite the reported differences between biochar materials derived from the same feedstock, key properties critical for soil amendment and remediation applications (i.e., H:C, surface area, %Corg, etc.) are reasonably consistent between laboratory and continuously fed equipment typical of commercial-scale systems. Thus, biochar materials obtained from well-controlled laboratory experiments conducted in a pure nitrogen atmosphere can be reasonably representative of biochar produced from the same feedstocks using industrial scale equipment.