Assessing the Feasibility of Zeolite-Based Dual-Function Aerosols for Stratospheric Carbon Capture and Solar Radiation Management

Abstract

Stratospheric aerosol injection (SAI) is a prominent candidate for solar radiation management (SRM), with growing interest in combining it with in-situ carbon dioxide (CO?) capture. This study evaluates the feasibility of using zeolite-based aerosols in dual-function SAI systems—providing both radiative forcing and CO? adsorption. Using Langmuir isotherm-based adsorption modeling and thermodynamic simulations under representative stratospheric conditions (~0.05atm, low temperatures), it is found that zeolite performance degrades by over 99.97% relative to ground-based direct air capture (DAC) scenarios. Additionally, achieving significant radiative impact would require the deployment of over 10? micro-scale delivery units. These findings indicate that zeolites are fundamentally unsuitable for airborne CO? capture and limited in their SRM potential as currently conceived. While the dual-function concept proves infeasible in its present form, the results contribute to atmospheric engineering research by identifying critical constraints and informing future pathways for climate intervention design.

Introduction

1. Background and Motivation

• Solar geoengineering, specifically Stratospheric Aerosol Injection (SAI), is being explored as a response to rapid global warming.

• Traditional sulfate aerosols enhance planetary albedo but do not capture CO? and cause environmental issues like ozone depletion and acid rain.

• Zeolites, especially ZSM-5, are proposed as dual-function particles that could reflect sunlight and capture CO? due to their:

  • High surface area and CO? affinity

  • UV and thermal stability

  • Potential to function in the stratosphere

2. Research Objective

• To test the feasibility of zeolite-based aerosol pods for simultaneous solar radiation reflection and carbon dioxide removal in the stratosphere (~20 km altitude).

• Stratospheric conditions (very low pressure and CO? partial pressure) challenge CO? capture functionality.

• A conceptual pod was designed and modeled using OpenSCAD, with simulation of gas adsorption and thermal dynamics.

3. Key Findings

• Reflectivity of zeolite particles remains effective for scattering solar radiation.

• However, CO? adsorption in the stratosphere is thermodynamically negligible due to extremely low partial pressures.

• The study rejects zeolite-based CO? capture in SAI and advises early elimination of such impractical strategies.

4. Material Selection and Evaluation

Selection Criteria:

• Albedo (reflectivity), thermal and UV stability, CO? adsorption under low pressure, mechanical integrity, and environmental safety.

Materials Evaluated:

Why ZSM-5?

• Good reflectivity and thermal durability.

• Low water affinity, UV stability.

• Environmentally benign and structurally stable in the stratosphere.

5. Pod Design and Engineering

• The pod, made of CFRP, is lightweight and thermally resilient.

• Designed for deployment at 18–22 km altitude via balloons or UAVs.

• Features:

  • Programmable dispersal mechanism.

  • Sensor integration for real-time environmental feedback.

  • Modular layout for payload containment and aerodynamic stability.

• CAD modeled using OpenSCAD, enabling parametric, script-driven, and reproducible design.

6. Simulation and Modeling

• Langmuir isotherm modeling showed negligible CO? adsorption at stratospheric pressures.

• A planetary energy balance model estimated global cooling potential from reflective zeolite particles.

• Design validated through cross-sectional 3D visualizations and component testing logic.

Conclusion

This study evaluated the feasibility of a zeolite-based aerosol injection system for dual-purpose climate intervention, combining radiative forcing and CO? capture objectives in the stratosphere. A custom-designed deployment pod was modeled and simulated, and environmental performance was assessed using quantitative methods. Key findings include: • CO? adsorption by ZSM-5 is negligible at stratospheric pressure, with modeled capacity dropping below 0.001 mmol/g. • Reflective surface deployment requires unrealistically large areas to produce any significant change in global surface temperature. • Balloon-based delivery to the stratosphere is mechanically feasible, but the material deployed must justify its operational and environmental cost. These findings indicate that zeolites, while effective in terrestrial DAC systems, are fundamentally unsuitable for airborne CO? capture and limited in their SRM utility at high altitudes. However, this negative result contributes to the refinement of climate intervention strategies by eliminating nonviable material pathways and informing the atmospheric science community about the physical constraints of high-altitude aerosol design. Future work should focus on alternative sorbents optimized for low-pressure environments and the decoupling of SRM and carbon removal functions into distinct system architectures.

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Copyright

Copyright © 2025 Vaishanavi Kurup. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.