This week’s publication highlights relate to carbon neutrality, ocean alkalinity enhancement and forestation.
Harnessing Enhanced Rock Weathering for Carbon Neutrality: Potential and Challenges in China
Abstract
The escalating urgency of global climate change underscores the need for effective strategies to manage atmospheric CO₂ concentrations. Enhanced rock weathering (ERW) has emerged as a promising carbon removal technology. By applying powdered silicate rocks rich in calcium and magnesium, such as basalt, the dissolution process can be accelerated to sequester CO₂ in the form of dissolved inorganic carbon (DIC) within soil porewater, which is ultimately transported to the ocean, achieving long-term carbon storage. Using a life cycle assessment (LCA) framework, this study evaluates the feasibility of basalt-based ERW in China, focusing on its environmental and economic implications across various application scenarios. The findings highlight that basalt particle size and environmental conditions are critical determinants of weathering efficiency. Smaller particles, elevated temperatures, and acidic soils enhance dissolution rates but also result in higher energy consumption for grinding and increased carbon emissions. China’s extensive basalt reserves, diverse climatic conditions, and vast agricultural lands create favorable conditions for large-scale ERW implementation. Nationwide application of basalt at p80 = 100 μm could sequester 0.2 Gt CO₂ by 2100, while finer particles (p80 = 10 μm) could achieve 0.5 Gt by 2060. Despite its potential, ERW faces challenges, including heavy metal release, uncertainties in long-term weathering rates, and cost constraints.
Cong, L. et al. (2025) Harnessing Enhanced Rock Weathering for Carbon Neutrality: Potential and Challenges in China 271 (105309) Earth-Science Reviews.
Read the full paper here: Harnessing Enhanced Rock Weathering for Carbon Neutrality: Potential and Challenges in China I Earth-Science Reviews.
Site Selection for Ocean Alkalinity Enhancement Informed by Passive Tracer Simulations
Abstract
Ocean alkalinity enhancement is a marine-based carbon dioxide removal strategy that involves adding alkaline material to the surface ocean to boost carbon uptake and storage. The physical circulation of ocean water exerts fundamental control on the dilution, spreading, and retention of alkaline materials, influencing carbon removal effectiveness, environmental impacts, and monitoring feasibility. Here we evaluate potential sites and timing for ocean alkalinity enhancement on the U.S. Northeast Shelf by conducting passive tracer simulations from 2009 to 2017. Monthly dye release experiments across ten locations were analyzed by quantifying dye evolution metrics such as surface spread, lateral movement, upper-ocean concentration, and gas transfer velocity. A site selection index was developed to assess site and time suitability for tracer dispersal for ocean alkalinity enhancement. Results showed strong seasonality, with optimal conditions in summer and less favorable conditions in winter. Among the tested locations, Wilkinson Basin emerged as the most favorable tracer release site due to its larger spreading area, higher tracer concentrations, and longer decay time. These findings inform a future field experiment in the region and offer a scalable framework for guiding future research on ocean alkalinity enhancement in other regions based on physical characteristics of tracer evolution.
Guo, Y. et al. (2025) Site Selection for Ocean Alkalinity Enhancement Informed by Passive Tracer Simulations 535 (6) Communications Earth & Environment.
Read the full paper here: Site Selection for Ocean Alkalinity Enhancement Informed by Passive Tracer Simulations I Communications Earth & Environment.
The Carbon and Climate Impacts of Forestation in Australia
Abstract
Forestation is a feasible and cost-effective strategy to remove CO2 from the atmosphere and store it in natural reservoirs. However, it is highly uncertain how much carbon new forests can remove, how those changes will affect the climate at the local to global scales, and how a changing climate might affect the effectiveness of forestation. Here, we use the ACCESS-ESM1-5 earth system model to perform idealised global experiments of forestation to investigate the effects of additional forest cover on the Australian climate at a range of different global warming levels. Experiments include sensitivity tests that replace various fractions of existing croplands with up to 19.3 × 106 km2 of forests globally (0.58 × 106 km2 in Australia or ~8.5 times the area of Tasmania). We find that forestation on these lands can remove 40 to 80 teragrams (Tg) of carbon per year over 100 years for Australia alone compared to a scenario without forestation. For comparison, anthropogenic greenhouse gas emissions in Australia were 121.8 Tg C-CO2e in 2024. Depending on whether these forests are harvested for long-lived wood products, forestation could achieve a cumulative carbon sequestration of 5–14 petagrams (Pg) of carbon. A coordinated global forestation effort could cool Australia’s mean climate by up to 0.1–0.4°C with respect to the investigated global warming levels. However, ACCESS-ESM1-5 also projects some regional warming due to the associated decreased albedo of forested areas. With careful consideration of land cover changes to account for potential regional warming, forestation has considerable biophysical potential to remove CO2 and contribute to meeting net-zero targets in Australia and globally.
Loughran, T. et al. (2025) The Carbon and Climate Impacts of Forestation in Australia 75 (3) Journal of Southern Hemisphere Earth Systems Science.
Read the full paper here: The Carbon and Climate Impacts of Forestation in Australia I Journal of Southern Hemisphere Earth Systems Science.
Machine Learning and Spatio Temporal Analysis for Assessing Ecological Impacts of the Billion Tree Afforestation Project
Abstract
This study evaluates the Billion Tree Afforestation Project (BTAP) in Pakistan’s Khyber Pakhtunkhwa (KPK) province using remote sensing and machine learning. Applying Random Forest (RF) classification to Sentinel-2 imagery, we observed an increase in tree cover from 25.02% in 2015 to 29.99% in 2023 and a decrease in barren land from 20.64% to 16.81%, with an accuracy above 85%. Hotspot and spatial clustering analyses revealed significant vegetation recovery, with high-confidence hotspots rising from 36.76% to 42.56%. A predictive model for the Normalized Difference Vegetation Index (NDVI), supported by SHAP analysis, identified soil moisture and precipitation as primary drivers of vegetation growth, with the ANN model achieving an R2 of 0.8556 and an RMSE of 0.0607 on the testing dataset. These results demonstrate the effectiveness of integrating machine learning with remote sensing as a framework to support data-driven afforestation efforts and inform sustainable environmental management practices.
Mehmood, K. et al. (2025) Machine Learning and Spatio Temporal Analysis for Assessing Ecological Impacts of the Billion Tree Afforestation Project 15 (2) Ecology and Evolution.
Read the full paper here: Machine Learning and Spatio Temporal Analysis for Assessing Ecological Impacts of the Billion Tree Afforestation Project I Ecology and Evolution.
The Potential of Wastewater Treatment on Carbon Storage through Ocean Alkalinity Enhancement
Abstract
Ocean alkalinity enhancement (OAE) implemented through wastewater treatment plants increases the alkalinity of the effluents and discharges them into the ocean, referred to as wastewater-based OAE. However, the alkalization capability and its carbon storage stability when adding alkaline minerals to wastewater treatment are uncertain. In this study, total alkalinity was enhanced to more than 10 millimoles per kilogram and phosphate removal was improved when we added olivine to wastewater in a laboratory setting. The alkalization rate by olivine dissolution in aerobically treated wastewater was 20 times higher than in seawater. We estimated the potential of carbon sequestration through wastewater-based OAE to be 18.8 ± 6.0 teragrams of CO2 per year globally, with notable potential in the 20°N to 60°N region.
Zheng, L. et al. (2025) The Potential of Wastewater Treatment on Carbon Storage through Ocean Alkalinity Enhancement 11 (18) Science Advances.
Read the full paper here: The Potential of Wastewater Treatment on Carbon Storage through Ocean Alkalinity Enhancement I Science Advances.