This week’s publication highlights cover a wide range of issues related to enhanced rock weathering, ocean alkalinity enhancement, carbon sequestration, ocean iron fertilization and direct air carbon capture and storage.
Larger Rock Extraction Sites Could Improve the Efficiency of Enhanced Rock Weathering in the United Kingdom
Abstract
Large-scale removal of carbon dioxide from the atmosphere is required to meet net-zero targets. Enhanced rock weathering, in which crushed silicate minerals are spread on cropland soils, is a promising approach, but the logistics of its supply chain are poorly understood. Here, we use a numerical spatio-temporal allocation model that links potential rock extraction sites in the United Kingdom with croplands, modelling deployment pathways over the period 2025–2070. We find that expanding individual quarries (up to 20 times larger than the current average) and prioritising supply timing and location can increase carbon-removal efficiency by 20%, cut transport demand by 60% and reduce the number of operating quarries four-fold, while enabling up to 700 million tonnes of carbon dioxide removal by 2070. However, these large sites may face stronger local opposition and planning challenges, underscoring the critical role of policy in enabling feasible deployment.
Madankan, M. et al. (2025) Larger Rock Extraction Sites Could Improve the Efficiency of Enhanced Rock Weathering in the United Kingdom 666 (6) Communications Earth & Environment.
Read the full paper here: Larger Rock Extraction Sites Could Improve the Efficiency of Enhanced Rock Weathering in the United Kingdom I Communications Earth & Environment.
Effects of Ocean Alkalinity Enhancement on Plankton in the Equatorial Pacific
Abstract
Ocean alkalinity enhancement is a potential strategy for gigatonne-scale atmospheric carbon dioxide removal. It uses alkaline substances to convert seawater carbon dioxide into (bi)carbonate, enabling uptake of additional carbon dioxide from the atmosphere. A critical knowledge gap is how ocean alkalinity enhancement could influence marine plankton communities. Here we conducted 19 ship-based experiments in the Equatorial Pacific, examining three prevalent alkaline substances (sodium hydroxide, olivine, and steel slag) and their effects on natural phytoplankton populations under realistic and moderate alkalinity enhancements (16–29 μmol kg−1). Results demonstrate that sodium hydroxide had a negligible effect on phytoplankton while providing predictable alkalinity. Conversely, olivine disrupted plankton, especially cyanobacteria, heterotrophic bacteria, and picoeukaryotes while only providing 0.06 mmol alkalinity g−1 olivine. Steel slag moderately changed phytoplankton communities and fertilized growth while delivering 8 mmol alkalinity g−1 slag. Our study helps to determine which alkaline substance could be suitable for application in the Equatorial Pacific.
Guo, J. et al. (2025) Effects of Ocean Alkalinity Enhancement on Plankton in the Equatorial Pacific 6 (270) Communications Earth & Environment.
Read the full paper here: Effects of Ocean Alkalinity Enhancement on Plankton in the Equatorial Pacific I Communications Earth & Environment.
Carbon Sequestration and Soil Responses to Soil Amendments - A Review
Abstract
The recent increase in climate change that results in varying weather conditions and climate change scenarios has necessitated an urgent need to address the situation using a nature-based solution approach. Soil is a major source and sink of carbon, and any approach that could enhance its carbon sequestration potential could aid in climate change control through reducing carbon emissions. One of these nature-based solutions is the use of organic amendments. Most organic amendments serve as a source of beneficial microbes, nutrients, and carbon for replenishing soil carbon stock and enhancing soil biological and biochemical processes. Thus, they are essential in maintaining soil biodiversity, promoting crop yield, and contributing to soil carbon sequestration. Harnessing organic amendments in soil carbon sequestration has led to using various organic materials such as biochar, animal manure, plant litter, coal gangue, and straw to enrich soil carbon stock. However, there are limitations regarding their consistency and efficacy under field and laboratory conditions. In this review, we explore soil organic carbon sources and compositions, soil amendments, priming and carbon sequestration, soil amendments in microbial selection and carbon sequestration, soil amendments in driving below-and-aboveground soil carbon sequestration processes, and the limitations of soil amendments to carbon sequestration. We further discuss the research gaps that will enhance our understanding of carbon sequestration and soil responses by leveraging a nature-based approach for controlling soil carbon emissions and improving soil carbon sinks.
Enebe, M. et al. (2025) Carbon Sequestration and Soil Responses to Soil Amendments - A Review 18 (100714) Journal of Hazardous Materials Advances.
Read the full paper here: Carbon Sequestration and Soil Responses to Soil Amendments - A Review I Journal of Hazardous Materials Advances.
Techno-Economic Analysis of Ocean Iron Fertilization
Abstract
This study provides an updated, comprehensive framework for conducting a techno-economic assessment (TEA) of novel carbon dioxide removal approaches. Specifically, the framework is applied to a scenario involving ocean iron fertilization (OIF) in the Southern Ocean. The study investigates whether cost elements, such as administrative and support labor, are accurately included in standard methodologies and proposes solutions for characterizing prospective cost elements and uncertainty in novel CDR TEAs. The first-of-a-kind (FOAK) levelized cost of carbon (LCOC) for OIF deployment is approximately $200 per tonne of CO2. Learning rates are applied, and prospective nth-of-a-kind (NOAK) costs decrease to approximately $180 per tonne of CO2. A local sensitivity analysis indicates that oceanographic parameters, such as the export efficiency of carbon biomass to the deep ocean, have a greater impact on the LCOC compared to engineering parameters like the cost of equipment or materials. Nevertheless, large capital engineering expenditures of approximately $120–160 million also significantly affect the levelized cost. The effect of these high-impact parameters on the LCOC is demonstrated by a cost range from $25 per tonne of CO2 to $53,000 per tonne of CO2 for best- to worst-case scenarios when varying values for monitoring, reporting, and verification (MRV) processes, losses due to nutrient robbing, equivalent carbon (CO2e) losses from N2O production, CO2 ventilation losses to the atmosphere, net increase in primary production, and export efficiency are considered. Additionally, the effect of learning rates on determining prospective costs is shown through a sensitivity analysis to have a less significant impact on the overall costs of deployment and, in turn, future cost reductions when large parameter input uncertainties are present. Based on these results, it is recommended that oceanographic parameters be better characterized through additional research and development to reduce uncertainty in cost estimation. Methods of OIF deployment, including MRV processes, should also be investigated to minimize capital costs. Additionally, the proposed framework, including the bottom-up business cost analysis, should be applied to other CDR approaches to provide consistent and comprehensive comparisons for companies and decision-makers, underpinning informed funding decisions in the CDR space.
Ward, C. et al. (2025) Techno-Economic Analysis of Ocean Iron Fertilization 7 Frontiers in Climate Change.
Read the full paper here: Techno-Economic Analysis of Ocean Iron Fertilization I Frontiers in Climate Change.
Low-Cost Negative Emissions by Demand-Side Management for Adsorption-based Direct Air Carbon Capture and Storage
Abstract
Limiting anthropogenic climate change to below 2 °C requires substantial and rapid reductions in greenhouse gas emissions. Additionally, carbon dioxide removal technologies are essential to compensate for hard-to-abate emissions and counteract overshooting the earth’s carbon budget. One prospective technology is direct air carbon capture and storage (DACCS), but its energy intensity and costs limit large-scale deployment. Flexible DACCS operation seems promising for cost reduction but yet remains underexplored. This study explores the economic benefits of flexible operation of adsorption-based DACCS, considering fluctuations in both electricity prices and greenhouse gas emissions from the electricity supply. To increase the feasibility of flexible DACCS operation, the typical steam-assisted temperature vacuum swing adsorption cycle is enhanced by introducing two break phases and variable air and steam mass flows during adsorption and desorption. The benefits of flexible operation are comprehensively evaluated using a DACCS system model integrating a detailed dynamic process model with life-cycle greenhouse gas emissions and economic data. The flexible operation allows each cycle to be adjusted to optimally address the time-varying greenhouse gas emissions and costs from electricity supply. A rolling horizon algorithm combined with particle swarm optimization is used to optimize the DACCS cycles in flexible operation mode over one week. The case study focuses on the future German power grid and a DACCS system using amine-functionalized sorbents. Results indicate that flexible DACCS operation can significantly reduce net carbon removal costs by up to 20 % compared to a steady-state operation. These findings highlight the potential of flexible DACCS operation to support carbon neutrality efforts by enabling cost-effective carbon dioxide removal through integration with volatile renewable energy systems.
Postweiler, P. et al. (2025) Low-Cost Negative Emissions by Demand-Side Management for Adsorption-based Direct Air Carbon Capture and Storage 4 (9) Carbon Neutrality.
Read the full paper here: Low-Cost Negative Emissions by Demand-Side Management for Adsorption-based Direct Air Carbon Capture and Storage I Carbon Neutrality.