This week’s publication highlights relate to direct air capture, forestation, enhanced concrete weathering and ocean alkalinity enhancement.
Kinetic and Thermodynamic Limitations 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 Limitations in Direct Air Capture: Toward Optimized Adsorbent Design and Regeneration Strategies. Current Opinion in Chemical Engineering 51 (101219).
Read the full paper here: Kinetic and Thermodynamic Limitations in Direct Air Capture: Toward Optimized Adsorbent Design and Regeneration Strategies I Current Opinion in Chemical Engineering.
Photo-DAC: Light-Driven Ambient-Temperature Direct Air Capture by a Photobase
Abstract
Direct air capture (DAC) may reduce atmospheric CO2 concentrations to preindustrial levels, yet the high energies and temperatures involved in current DAC technologies hinder large-scale deployment. In the case of aqueous-based CO2 absorbents, a large energetic penalty is associated with heating and boiling off water, as required for thermally driven solvent regeneration. This could be avoided via photochemically driven pH swings involving photoacids or photobases, and harnessing abundant and renewable solar energy, though efficient solvent regeneration and recycling in a realistic multicycle DAC process remains challenging. Herein, we report a photochemically driven DAC process (photo-DAC) in which atmospheric CO2 capture by an aqueous glycylglycine (GlyGly) solution is enabled through a pH swing by a pyridine-substituted diiminoguanidine (PyDIG) photobase. Upon irradiation with UV light, the PyDIG photobase undergoes photoisomerization from the E,E to the Z,Z isomer, corresponding to a pKa increase of 2.8 units that activates GlyGly for DAC through deprotonation. After the GlyGly/PyDIG solvent is saturated with atmospheric carbon dioxide, leaving it in the dark under ambient conditions leads to the isomerization of PyDIG from the Z,Z back to the E,E isomer, which is accompanied by a pH drop and CO2 release. To demonstrate the recyclability of the GlyGly/PyDIG solvent, we have completed six consecutive DAC cycles, with a measured average cyclic capacity in the range of 0.21–0.26 mol CO2 per mol of GlyGly/PyDIG. These results open the prospect for energy-efficient DAC cycles completed entirely at ambient conditions, thereby avoiding the significant energy penalties associated with heating and boiling aqueous solvents.
Einkauf, J. et al. (2026) Photo-DAC: Light-Driven Ambient-Temperature Direct Air Capture by a Photobase. Journal of the American Chemical Society.
Read the full paper here: Photo-DAC: Light-Driven Ambient-Temperature Direct Air Capture by a Photobase I Journal of the American Chemical Society.
Enhanced Carbon Sinks in China Using a Spatially Optimization Strategy
Abstract
China plans expanding 49.5 million hectares of new forests by 2050 to strengthen carbon sequestration. However, estimates of the carbon benefits from this expansion rarely consider the effect of ‘forest edge’, where tree mortality increases under intensified stress from wind, drought, pests, and fire. Here we show that proximity to forest edges substantially reduces biomass carbon storage, and develop a spatial optimization strategy that prioritizes planting in areas that minimize edge effects. Our projections show that forestation optimized for edge effects results in a 51% increase in carbon gain (986 ± 22 Tg by 2060), with approximately half of the total gain driven by reduced edge effects. These findings demonstrate that ignoring edge effects can significantly overestimate carbon sink potential and highlight spatially optimized forestation as a pathway to maximize climate mitigation and ecological benefits.
Dong, Y. et al. (2026) Enhanced Carbon Sinks in China Using a Spatially Optimization Strategy. Nature Communications.
Read the full paper here: Enhancing Carbon Sinks in China Using a Spatially-Optimized Forestation Strategy I Nature Communications.
Carbon Dioxide Removal by Enhanced Concrete Weathering in Soil
Abstract
Carbon dioxide (CO2) removal from the atmosphere is necessary to reduce negative impacts from climate change, and one method could be using waste concrete for enhanced concrete weathering (ECW) a subset of enhanced weathering. When cement paste and aggregates in concrete weather in soil, CO2 can be captured and stored as bicarbonate or precipitated as carbonates. There may be environmental ramifications from the addition of concrete to soil, both beneficial and detrimental, like increased pH, increased calcium concentrations, and possible leaching of pollutants. Despite possible negative effects like the introduction of contaminants, proper screening and application of concrete could mitigate ecological harm and ensure the environmental safety ECW. ECW studies are limited; much more research is needed on carbon movement and balance in soil systems. Future longitudinal studies are needed that encompass a variety of direct and indirect measurements in varying climactic conditions that are able to fully capture C stability and permanence from ECW. A robust and consistent testing regimen is needed to evaluate the safety of concrete for ECW and to establish concrete standard contaminant thresholds. Lastly, analysis is needed to determine the choice way to scale up ECW through material supply chains and logistics as well as creating guidelines for ECW application such as particle size and application rate recommendations.
Hopkins, B. and Lal, R. (2026) Carbon Dioxide Removal by Enhanced Concrete Weathering in Soil. 6 (100068) Total Environment Engineering.
Read the full paper here: Carbon Dioxide Removal by Enhanced Concrete Weathering in Soil I Total Environment Engineering.
The Carbon Dioxide Removal Potential of Cement and Lime Kiln Dust via Ocean Alkalinity Enhancement
Abstract
Ocean alkalinity enhancement (OAE) is a proposed method for atmospheric carbon dioxide removal (CDR), and involves the addition of alkaline minerals to surface waters to elevate seawater alkalinity and enhance atmospheric CO2 storage. Cement kiln dust (CKD) and lime kiln dust (LKD) are alkaline side streams from the cement and lime industry that have OAE potential due to their widespread availability and fine particle size. Here, we evaluated the dissolution kinetics, CO2 sequestration potential, and ecological risks of CKD and LKD by means of laboratory dissolution experiments. A reactive fraction (∼ 25 % in LKD and ∼ 29 % in CKD) dissolved rapidly within 24 h, with most dissolution occurring within the first hour. Dissolution provided a concomitant alkalinity release that was higher for LKD (up to 8.0 ± 0.5 mmol alkalinity per g) than CKD (2.4 ± 0.2 mmol g−1), thus providing a sizeable CO2 sequestration capacity for LKD (297 ± 20 g CO2 per kg) and CKD (88 ± 6 g CO2 per kg). Based on current industrial production rates, this translates into global CDR potentials of up to 8.7 ± 0.6 Mt CO2 yr−1 for LKD and 25 ± 2 Mt CO2 yr−1 for CKD. These estimates suggest that both materials could be viable OAE feedstocks, although further testing under conditions that more closely mimic natural coastal conditions is needed. Furthermore, we hypothesize that the substantial residual calcite content of LKD (∼ 54 %) and CKD (∼ 37 %) may provide additional sequestration via metabolic dissolution in marine sediments. However, kiln dust deployment will generate elevated turbidity levels that may exceed environmental thresholds, underscoring the need for carefully designed application strategies to minimize local ecological impacts.
Flipkens, G. et al. (2026) The Carbon Dioxide Removal Potential of Cement and Lime Kiln Dust via Ocean Alkalinity Enhancement 23 Biogeosciences 399-420.
Read the full paper here: The Carbon Dioxide Removal Potential of Cement and Lime Kiln Dust via Ocean Alkalinity Enhancement I Biogeosciences.