This week’s publication highlights relate to direct air capture, ocean cdr and enhanced rock weathering.
Kinetic and Thermodynamic Limitation in Direct Air Capture: Toward Optimized Adsorbent Design and Regeneration Strategies
Abstract
Direct air capture (DAC) faces significant kinetic and thermodynamic challenges due to the ultra-dilute CO2 concentration in the atmosphere (∼0.04%). Narrowing these gaps is essential for enhancing the efficiency and viability of DAC as a negative emissions technology. This review systematically explores three strategies to address these challenges: (i) optimizing the pore structure of adsorbents, (ii) incorporating surfactants, and (iii) optimizing the regeneration process. By focusing on the above strategies, this study highlights recent advancements in improving adsorption equilibrium and kinetics, and energy efficiency under DAC conditions, which provides insight for guiding future research and advancing DAC technologies.
Jia, X et al. (2026) Kinetic and Thermodynamic Limitation in Direct Air Capture: Toward Optimized Adsorbent Design and Regeneration Strategies 51 (101219) Current Opinion in Chemical Engineering.
Read the full paper here: Kinetic and Thermodynamic Limitation in Direct Air Capture: Toward Optimized Adsorbent Design and Regeneration Strategies I Current Opinion in Chemical Engineering.
Weather-Dependent Direct Air Capture Process Modeling for Techno-Economic Assessments
Abstract
Adsorption-based Direct Air Capture (DAC) is crucial for achieving negative emissions but faces significant challenges due to high energy demand and operational costs. While recent research has highlighted that weather conditions significantly affect DAC energy demand and cost, current DAC systems are typically optimized under steady-state conditions, overlooking the impact of ambient weather variability on the optimal operating point. This study addresses that gap by investigating whether dynamically adjusted adsorption and desorption durations based on hourly weather conditions can improve energy efficiency compared to static operation. Therefore, a process model incorporating co-adsorption effects was optimized for real-world weather conditions and the results are utilized as an input for a techno-economic assessment. Dynamic operation of the optimized process model was evaluated using hourly weather data from four possible DAC locations, revealing potential reductions in electrical and thermal energy demands of up to 8.8 % and 0.9 %, respectively. Additional analyses show that simplified day–night and seasonal operating strategies achieve nearly the same energy savings as hourly adaptation, substantially reducing control complexity. Integration of the optimized process model into a techno-economic assessment reveals weather-driven cost variations of up to 72 €/tCO2 and demonstrates strong sensitivity of DAC costs to renewable energy intermittency. By providing detailed data on the optimized process model, including energy consumption and productivity across diverse climatic conditions, the study supports more refined and location-specific future assessments.
Jajjawi, A. (2026) Weather-Dependent Direct Air Capture Process Modeling for Techno-Economic Assessments 351 (1211003) Energy Conversion and Management.
Read the full paper here: Weather-Dependent Direct Air Capture Process Modeling for Techno-Economic Assessments I Energy Conversion and Management.
Ocean Carbon Dioxide Removal and Storage
Abstract
The ocean, Earth’s largest carbon reservoir, exerts a central role over atmospheric CO2 through its capacity to store carbon primarily as bicarbonate ions. Direct observations indicate that the global ocean has a net carbon uptake of 2.6–3.0 petagrams of carbon annually, representing nearly 30% of anthropogenic CO2 emissions. This review examines two principal domains of oceanic carbon cycling. The first concerns the natural uptake and storage of anthropogenic CO2, with emphasis on the response of the marine carbonate system and the spatial distribution of absorbed carbon. The second addresses emerging marine CO2 removal strategies, especially ocean alkalinity enhancement and macroalgae-based approaches. Ocean alkalinity enhancement aims to increase seawater buffering capacity to facilitate greater CO2 uptake, whereas macroalgae-based strategies rely on photosynthetic fixation and the subsequent storage of organic and inorganic carbon in various reservoirs. Effective implementation of these approaches necessitates rigorous monitoring, reporting, and verification frameworks to ensure their quantifiable efficacy and environmental integrity.
Lee, C. et al. (2026) Ocean Carbon Dioxide Removal and Storage. Chemical Reviews.
Read the full paper here: Ocean Carbon Dioxide Removal and Storage I Chemical Reviews.
Carbon Fixation of a Temperate Plankton Community in Response to Calcium-and Silicate-based Ocean Alkalinity Enhancement Using Air-Sea Gas Exchange Measurements
Abstract
Ocean Alkalinity Enhancement (OAE) is a carbon dioxide removal strategy that aims to chemically sequester atmospheric CO2 in the ocean while potentially alleviating localized effects of ocean acidification. Depending on the implementation approach, OAE can considerably alter seawater carbonate chemistry, resulting in temporarily reduced CO2 partial pressure (pCO2) and elevated pH before re-equilibration with the atmosphere or mixing with unperturbed waters. To investigate the effects of OAE on biogeochemical processes and organisms under close-to-natural conditions, a large-scale mesocosm experiment was conducted in a temperate fjord ecosystem near Bergen, Norway, during late spring. A non-CO2-equilibrated OAE approach was chosen, simulating OAE with calcium- and silicate-based minerals. A gradient of five OAE levels was achieved by increasing total alkalinity (TA) by 0–600 µmol kg−1. The added TA remained relatively stable over the 47 d experiment and measured CO2 gas exchange rates reached up to −15 mmol C m−2 d−1. We estimated that full equilibration (95 %) by air-sea gas exchange for a ΔTA of 600 µmol kg−1 would take ∼1050 d. Furthermore, various mineral-type and/or pCO2 pH effects were found. Coccolithophore calcification followed an optimum curve response along the pCO2 gradient, consistent with findings from single-species laboratory cultures. In contrast, in-situ net community production (NCP) was higher in the silicate-based treatments, but was not modified by changes in pCO2. Zooplankton respiration, estimated from in-situ NCP and in-vitro NCP incubations, was lower for the silicate-based treatments and negatively correlated with pCO2. These complex findings suggest both direct and indirect effects of mineral type and OAE level and provide a valuable foundation for designing future OAE field trials. For a safe application of OAE, non-equilibrated alkalinity additions must balance efficiency and environmental impact.
Schneider, J et al. (2026) Carbon Fixation of a Temperate Plankton Community in Response to Calcium-and Silicate-based Ocean Alkalinity Enhancement Using Air-Sea Gas Exchange Measurements 23 (1) Biogeosciences.
Read the full paper here: Carbon Fixation of a Temperate Plankton Community in Response to Calcium-and Silicate-based Ocean Alkalinity Enhancement Using Air-Sea Gas Exchange Measurements I Biogeosciences.
Review and Syntheses: Carbon vs. Cation based MRV of Enhanced Rock Weathering and the Issue of Soil Organic Carbon
Abstract
We discuss the “monitoring, reporting and verification” (MRV) strategy of Enhanced Weathering (EW) based on carbon accounting and argue that in open systems such as arable land, this approach is ill-suited to close the balance of all carbon fluxes. We argue for total alkalinity (TA) as the central parameter for the carbon based MRV of EW. However, we also stress that tracking alkalinity fluxes using a systems-level approach is best done by focusing on charge balance maintenance through time. We start by explaining the concept and history of alkalinity conceptualization for the oceans. The same analytical method first proposed for the oceans – titration with a strong acid – is now commonly used for porewaters in agricultural soils. We explain why this is an accurate analysis for ocean water and why it is unsuitable to record TA for porewaters in agricultural soils. We then introduce an alternative MRV based on cation accounting and finally discuss the fate of cations released from the weathering of basalt, soil cation dynamics and close by suggesting open research questions.
Bijma, J. et al. (2026) Review and Syntheses: Carbon vs. Cation based MRV of Enhanced Rock Weathering and the Issue of Soil Organic Carbon 23 Biogeosciences.
Read the full paper here: Review and Syntheses: Carbon vs. Cation based MRV of Enhanced Rock Weathering and the Issue of Soil Organic Carbon I Biogeosciences.