How Much CO₂ Can Enhanced Weathering Really Remove? - Derry

Cornell University geochemist Louis Derry joins @geoengineering1 to discuss a fundamental question for enhanced rock weathering: how much of the alkalinity generated in soils actually makes it through watersheds to the ocean? Derry argues that many studies and commercial MRV approaches focus on the top 10-30 cm of soil, potentially missing critical processes along the full flow path, including ion exchange in acidic soils, secondary clay formation, acidity generation and carbonate precipitation, which can reduce alkalinity export before it reaches streams.He highlights hydrological constraints, arguing that limited runoff and realistic alkalinity concentrations make proposed removal rates of 5-10 tonnes of CO₂ per hectare per year difficult to achieve across typical row-crop regions. Drawing on natural basaltic catchments and experimental systems, he points to estimates of global basalt weathering of ~0.1-0.2 Gt CO₂/yr, suggesting gigaton-scale enhanced weathering projections are overoptimistic, with co-benefits more credible than large-scale CDR. Paper Discussed: Derry, L. A., Maher, K., & Chadwick, O. A. (2026). Critical zone processes limit alkalinity export from natural basaltic systems. Nature, 1–6. https://doi.org/10.1038/s41586-026-10936-3Related article: Limitations on carbon dioxide uptake by enhanced weathering - Springer Nature Research Communitieshttps://communities.springernature.com/posts/limitations-on-carbon-dioxide-uptake-by-enhanced-weathering

@geoengineering1 interviews Claudia Elisabeth Wieners and Meike de Nooij about extratropical cyclones, the winter storm systems that drive much of the weather variability and many extreme wind and precipitation events in the midlatitudes, and how stratospheric aerosol injection (SAI) could alter their tracks and associated weather extremes.They discuss what makes extratropical cyclones different from tropical cyclones, why SAI could affect storm tracks, and what their high-resolution modelling reveals about changes in the North Atlantic and North Pacific. The conversation explores why SAI is not simply an “undo button” for global warming, with regional shifts in storm tracks and different responses in precipitation and wind extremes even when global temperatures are brought closer to present-day levels.Claudia and Meike also discuss the uncertainties surrounding their findings, the need for further high-resolution modelling, and the broader challenges of assessing and governing SAI. They argue that governments and policymakers need to take SAI seriously by supporting rigorous research and considering how any future deployment should be carefully governed.Paper discussed: de Nooij, M., de Jong, J., Baatsen, M. L., & Wieners, C. E. (2026). Extratropical Cyclone and Storm track Responses to Stratospheric Aerosol Injection in High-Resolution CESM Simulations. EGUsphere [preprint], 1-26. https://doi.org/10.5194/egusphere-2026-4133

Could reducing sunlight to cool the planet also affect mental health? @geoengineering1 interviews Shinsuke Tanaka about new research examining the link between sunlight and suicide and what it could mean for solar radiation management (SRM).Using nearly three decades of U.S. county-month data, Tanaka and colleagues find that sustained reductions in sunlight significantly increase suicide rates. They estimate that a 1.5°C SRM scenario could result in around 3,810 additional U.S. suicides between 2030 and 2100 from reduced sunlight alone, or 16,320 when temperature effects are included.The conversation also covers the difference between seasonal correlations and causal effects, possible biological and behavioral mechanisms, and the challenges of applying U.S.-based findings globally.Paper Discussed: Tanaka, S., & Matsubayashi, T. (2026). Clouding the mind? Assessing the suicide impacts of solar radiation management in the United States. The Japanese Economic Review, 1-21. https://link.springer.com/article/10.1007/s42973-026-00273-5

How much carbon can enhanced rock weathering actually remove? In this episode, @geoengineering1 talks with Tyler Kukla of CarbonPlan about how assumptions about rock surface roughness can dramatically change enhanced weathering estimates.They discuss why surface area is critical to weathering rates, how commonly used roughness calculations can overestimate available surface area, and what this means for modeled CO₂ removal. The conversation also explores the differences between surface-area- and water-transport-limited weathering, the challenges of scaling enhanced weathering, and why better measurements are needed to constrain models.The discussion is based on Tyler Kukla et al.’s CarbonPlan article, How Surface Roughness Scaling Can Mislead Enhanced Weathering Predictions. https://carbonplan.org/research/modeling-bytes-02-roughness

@geoengineering1 interviews Taveen Kapoor about his study [preprint] showing that purely scattering stratospheric aerosols can produce positive shortwave radiative forcing, and localized warming, over high-albedo surfaces such as snow, ice, and deserts. They discuss how diffuse light reflected from bright surfaces travels farther through the aerosol layer, increasing the likelihood of backscattering toward the surface.They also discuss why multi-angle radiative-transfer calculations reveal stronger positive forcing than the standard two-stream approximation, particularly in tropical and extratropical regions, while daily averages can obscure intense daytime forcing peaks.The conversation explores implications for SAI, including potential effects on snowmelt and regions such as the Tibetan Plateau and Sahel, as well as the growing burden of alumina aerosols from spacecraft reentry. They also discuss uncertainties and related research on alumina-based stratospheric aerosols.Paper Discussed: Zhang, L., Kapoor, T. S., Upadhyay, P., & Chakrabarty, R. K. (2026). Purely light-scattering aerosols could induce positive shortwave radiative forcing over high-albedo surfaces. EGUsphere, 2026, 1-17. https://doi.org/10.5194/egusphere-2026-3947

In this episode, @geoengineering1 speaks with Ahmed El-Sayed of Viridas Technologies, a company aiming to revolutionize Direct Air Capture (DAC) by redesigning the process from the ground up, including the fan system itself.The conversation explores why DAC remains expensive, largely due to the extremely low concentration of CO2 in ambient air. While most research focuses on developing new solvents and materials to reduce energy use, Ahmed argues that the thermodynamic limits of capture efficiency may already have been reached. Instead, Viridas is pursuing a different strategy i.e. increasing the volume of air processed.Their proposed high-pressure system reduces contactor size by 70x while delivering more than 3100x better performance through major gains in absorption capacity and absorption rate. Ahmed also discusses the use of scalable, oxygen-resistant solvents derived from widely produced industrial chemicals, and why the future of DAC may depend on breakthroughs in turbomachinery and membrane technologies to drive costs down to ultra-low levels and enable gigaton-scale deployment.Paper Discussed: Elsayed, A., & Alawadh, T. (2026). Scaling Carbon Removal to Gigaton Capacity using Pressurized Direct Air Capture. https://doi.org/10.26434/chemrxiv.15002130/v1Viridas Technologies: https://www.viridastechnologies.com/

@geoengineering1 interviews Rudolf Wessels, Director of Technology and Innovation at Avantium R&D Solutions in the Netherlands (founded in 2000 as a Shell spin-out). The discussion examines Avantium’s contribution to advancing Direct Air Capture (DAC) through high-throughput experimentation platforms designed to accelerate the discovery and optimization of sorbent materials, enabling rapid, parallel testing under controlled conditions.Wessels also discusses the company’s recent collaboration with the U.S. National Institute of Standards and Technology (NIST) Carbon Dioxide Removal Consortium, focused on improving measurement protocols, benchmarking practices, and validation in DAC systems. The episode highlights how standardized testing, process optimization, and material innovation can support the scale-up and credibility of carbon removal technologies.Links: https://rds.avantium.com/products/direct-air-capture-solutions/https://rds.avantium.com/avantium-joins-nist-to-accelerate-dac-innovation/To stay updated on all things geoengineering-related, subscribe to:Carbon Removal Updates Substack: https://carbonremovalupdates.substack.com/Solar Geoengineering Updates Substack: https://solargeoengineeringupdates.substack.com/

@geoengineering1 interviews Cory Sanderson, CTO and co-founder of Sustaera, a North Carolina-based Direct Air Capture (DAC) startup focused on low-cost carbon capture, separations chemistry, and process scale-up.Sanderson traces his journey from Air Products, where he worked on vacuum swing adsorption CO₂ capture for an SMR hydrogen plant and encountered economic and infrastructure constraints, to founding Sustaera. He also explains the company’s shift from CO₂-to-methane materials, which depended on costly clean hydrogen, to a pure DAC approach.He then outlines Sustaera’s system, which utilises a fixed, cartridge-based monolithic contactor with laminar-flow channels and a conductive, structured sorbent that integrates resistive (Joule) heating directly into the material, thereby improving efficiency, stability, and regeneration speed.He highlights the novelty of the design, noting that Sustaera has achieved over 90% heating efficiency in lab tests, 20-30 minute adsorption cycles, and multi-year sorbent lifetimes. With a modular, catalytic-converter-style manufacturing approach, the company is currently at TRL 5, has pre-sold removals at $700/ton to Stripe and Shopify, and is raising $8.6M to build its first outdoor commercial unit.For more details, visit: https://www.sustaera.com/To stay updated on all things geoengineering-related, subscribe to:Carbon Removal Updates Substack: https://carbonremovalupdates.substack.com/Solar Geoengineering Updates Substack: https://solargeoengineeringupdates.substack.com/

@geoengineering1 interviews Paolo Piffaretti, co-founder of ClimeFi (https://www.climefi.com/), on how durable carbon dioxide removal (CDR) credits are verified and delivered for corporate buyers.ClimeFi acts as a buyer-side agent, helping organizations define contribution vs. compensation goals, run reverse-auction RFPs, build diversified portfolios, conduct due diligence, negotiate contracts with risk-mitigation clauses, and monitor suppliers through delivery.They also unpack how CDR deals work in practice, covering offtakes, pre-purchases, and newer call options for flexibility, along with what is changing in the market and how buyers manage risk in a space where many projects fail.ClimeFi has also recently opened its Beyond 2030 request for proposals (RFP) on behalf of multiple buyers. It is the company’s most ambitious procurement to date, targeting 100,000 to 500,000 tonnes of durable carbon removal. All pathways are eligible, provided permanence of 200+ years. Submissions close on Wednesday 8 April. Details: https://www.climefi.com/blog-posts/climefi-launches-beyond-2030-rfp-for-durable-carbon-removalTo stay updated on all things geoengineering-related, subscribe to:Carbon Removal Updates Substack: https://carbonremovalupdates.substack.com/Solar Geoengineering Updates Substack: https://solargeoengineeringupdates.substack.com/

In this episode, @geoengineering1 is joined by Britta Clark, a postdoctoral researcher at Harvard University, to unpack why solar geoengineering is increasingly compared to opioids. They discuss how this framing casts SRM as temporary “relief” from climate warming and why it raises concerns about potentially slowing emissions cuts. The conversation focuses on how climate models, policy debates, and public discourse can quietly shift expectations about how fast emissions reductions should happen once solar geoengineering is considered, even when people say it should not delay the energy transition. Together, they explore why this tension matters and what it could mean for future climate decisions.Paper: Clark, B. (2025). Solar geoengineering, delay, and addiction. Climatic Change, 178(11), 209. https://doi.org/10.1007/s10584-025-04059-3Open access version: https://philpapers.org/rec/CLASGD-2To stay updated on all things geoengineering-related, subscribe to:Carbon Removal Updates Substack: https://carbonremovalupdates.substack.com/Solar Geoengineering Updates Substack: https://solargeoengineeringupdates.substack.com/