This week’s publication highlights relate to natural land carbon sink, enhanced rock weathering, ocean alkalinity enhancement and marine CDR.
An Improved Approach to Estimate the Natural Land Carbon Sink
Abstract
The natural land carbon sink (SLAND) absorbs roughly 25–30% of anthropogenic CO2 emissions, thus playing a critical role in offsetting climate warming. In the Global Carbon Budget (GCB), SLAND is estimated using model simulations that isolate the carbon response of land to environmental changes (i.e. rising atmospheric CO2, nitrogen deposition, and changes in climate). However, these simulations assume fixed pre-industrial land cover, failing to represent today’s human-altered landscapes. This leads to a systematic overestimation of forest area, and thus CO2 sink strength, in regions heavily altered by human activity. We present a new process-based approach to estimate SLAND using Dynamic Global Vegetation Models. Our corrected estimate reduces SLAND by ~20% (0.6 PgC yr-1) over 2015–2024, from 3.00 ± 0.94 to 2.42 ± 0.77 PgC yr-1. We incorporate this new SLAND estimate with emissions from land-use change from bookkeeping models, to estimate a net land sink of 1.19 ± 1.04 PgC yr-1, which aligns closely with atmospheric inversion constraints. This downward revision of SLAND reduces the magnitude of the budget imbalance for 2015–2024, indicating a more consistent partitioning of the global carbon budget.
O’Sullivan, M. et al. (2026) An Improved Approach to Estimate the Natural Land Carbon Sink 29 (9) NPF Climate and Atmospheric Science.
Read the full paper here: An Improved Approach to Estimate the Natural Land Carbon Sink I NPF Climate and Atmospheric Science.
Assessing Urban Green Roofs for CO2 Removal via Enhanced Rock Weathering in Europe
Abstract
Green roofs represent a novel and promising platform for integrating enhanced rock weathering (ERW) as a carbon dioxide removal (CDR) strategy within urban environments. By utilising underused rooftop spaces, rock (feedstock)-amended green roofs for ERW could contribute meaningfully to climate mitigation targets while fitting within existing markets and policy frameworks. Despite this, a comprehensive assessment of opportunities and barriers to deployment is missing. Here, we provide a conceptual assessment, serving as a benchmark for the potential for large-scale ERW green roof deployment in Europe, examining literature from similar applications and estimating theoretical CDR potential at European and global scales, and identifying key opportunities and challenges. Our estimates suggest that, under conditions where 100% reactivity is achieved, green roofs in Europe could theoretically remove tens of millions of tonnes of CO2 via ERW (in addition to plant uptake) by 2060, assuming expanded rooftop coverage. However, these findings are based on maximum geochemical capacities rather than empirical data from real-world conditions. Globally, theoretical removal potential ranges from tens to hundreds of millions of tonnes CO2 per year, with major contributions from Central Asia, North America, Latin America and the Pacific. Beyond CDR benefits, ERW green roofs can enhance photovoltaic performance by improving energy efficiency and reducing evaporation, although weight capacity of each rooftop must be evaluated. This approach offers a promising pilot-scale research opportunity, bridging the gap between laboratory experiments and potential field-scale applications, but the feasibility and effectiveness of large-scale deployment will require further empirical investigation, especially concerning climatic conditions, infrastructure, costs and policy support.
Bullock, L. et al. (2026) Assessing Urban Green Roofs for CO2 Removal via Enhanced Rock Weathering in Europe 100708 Environmental Advances.
Read the full paper here: Assessing Urban Green Roofs for CO2 Removal via Enhanced Rock Weathering in Europe I Environmental Advances.
Alkaline Materials for Coastal Ocean Alkalinity Enhancement: A Comparative Study of Natural Silicates and Industrial Byproducts
Abstract
Coastal ocean alkalinity enhancement (OAE) is a promising ocean-based carbon dioxide removal (CDR) approach for mitigating climate change and counteracting ocean acidification. However, uncertainties persist regarding the efficacy and environmental safety of alkaline materials under realistic coastal conditions. This study comparatively investigated the CO2 sequestration potential, geochemical processes, and environmental impacts of four alkaline materials—natural silicates (olivine, basalt) and industrial byproducts (fly ash, steel slag)—through laboratory incubations with natural seawater (filtered and unfiltered) and in situ deployments off the East China Sea. Over 31-day incubations, basalt induced negligible alkalinity release, while olivine showed limited alkalinity enhancement (12 μmol/kg/day) compared to theoretical estimation, projecting a CO2 sequestration rate of 0.57 ± 0.06 Tg/month for a hypothetical coastal deployment in China. Notably, fly ash exhibited faster alkalinity release (30 μmol/kg/day) and the highest projected CO2 uptake (1.24 ± 0.05 Tg/month). In contrast, steel slag caused rapid pH increase and alkalinity consumption via secondary carbonate precipitation, representing a distinct carbon sequestration pathway. Heavy metal pollution index (HPI) assessments indicated low overall contamination risks of the materials, particularly in unfiltered seawater that better resembles natural conditions, though Ni release from olivine remains a concern. Streamlined life cycle analysis (S-LCA) highlighted fly ash’s advantages due to the avoidance of upstream carbon emissions (as a byproduct) and waste valorization potential, resulting in superior net CO2 removal efficiency. This work provides critical insights into material-specific trade-offs, suggesting fly ash as a promising candidate for short-term coastal OAE deployment that balances CO2 sequestration efficiency, manageable environmental risks, scalability, and affordability.
Li, X. et al. (2026) Alkaline Materials for Coastal Ocean Alkalinity Enhancement: A Comparative Study of Natural Silicates and Industrial Byproducts 226 (119338) Marine Pollution Bulletin.
Read the full paper here: Alkaline Materials for Coastal Ocean Alkalinity Enhancement: A Comparative Study of Natural Silicates and Industrial Byproducts I Marine Pollution Bulletin.
Manganese Oxide-Mediated Reactions with Olivine Dissolution Products: A Double-Edged Sword for Ocean Alkalinity Enhancement
Abstract
Olivine-based ocean alkalinity enhancement (OAE) is a promising carbon dioxide removal strategy, yet interactions with layered manganese oxides─ubiquitous minerals controlling trace metal biogeochemistry in marine sediments─remain poorly understood. We investigated these mechanisms using synthetic birnessite, a natural analogue of hexagonal layered Mn oxides, in controlled laboratory experiments in seawater under three scenarios reflecting different OAE deployment strategies: direct olivine-birnessite contact, exposure to simulated olivine leachate, and repeated alkaline inputs. Results revealed a dual role for birnessite. It accelerated olivine dissolution through proton-releasing cation exchange and surface-mediated Fe(II) oxidation. However, this proton generation consumed alkalinity, diminishing carbon sequestration efficiency. Regarding trace metals, birnessite efficiently scavenged Ni (>50%) and Co (>99%) but markedly enhanced Cr mobility (reaching ∼0.05 μmol kg–1), likely via oxidation to more toxic Cr(VI). Crucially, sustained Fe(II) supply mitigated this risk by reducing >50% of Cr(VI) back to Cr(III). Birnessite maintained structural stability throughout. While natural sediment systems are expected to introduce additional complexities, our findings underscore potential environmental trade-offs: Cr(VI) accumulation could exceed ecological thresholds in poorly flushed environments. This study provides foundational mechanistic insights into olivine-sediment interactions, establishing key parameters for modeling OAE safety in complex marine environments.
Zhuang, W. et al. (2026) Manganese Oxide-Mediated Reactions with Olivine Dissolution Products: A Double-Edged Sword for Ocean Alkalinity Enhancement 60(9) Environmental Science & Technology.
Read the full paper here: Manganese Oxide-Mediated Reactions with Olivine Dissolution Products: A Double-Edged Sword for Ocean Alkalinity Enhancement I Environmental Science & Technology.
Experimental Data for the Rate of CO2 Release from Seawater under Vacuum at 30°C and Ambient Pressure at 100°C
Abstract
This dataset provides experimental measurements to quantify the rate of CO₂ release from (sea)water. Two different conditions were tested: vacuum pressure and 30°C and ambient pressure and 100°C. Data were collected using 1) a vacuum setup consisting of vacuum flask, placed in a thermostat bath at 30°C connected to a vacuum pump, protected by a cold trap and 2) a beaker without vacuum setup for the atmospheric experiments. Rates were inferred by measuring pH and the total inorganic carbon (TIC) in the water. The latter was measured ex-situ using a TIC analyzer. The TIC concentrations were corrected for reduced volume of the residue to the original volume to determine the actual CO2 release after each timestep. Actual seawater samples were utilized to determine the relationship between CO₂ release and water residence time under vacuum and ambient pressure boiling circumstances. The dataset includes variables such as CO₂ release rates and pH changes over time that the sample was subject to boiling conditions, providing valuable insights for designing process equipment for marine Carbon Dioxide Removal (mCDR) applications (for example in evaporative desalination processes) in both atmospheric and sub atmospheric pressures.
Straatman, P. et al. (2026) Experimental Data for the Rate of CO2 Release from Seawater under Vacuum at 30°C and Ambient Pressure at 100°C 64(112435) Data in Brief.
Read the full paper here: Experimental Data for the Rate of CO2 Release from Seawater under Vacuum at 30°C and Ambient Pressure at 100°C I Data in Brief.