Stardust has disclosed details of the materials it wants to sprinkle in the atmosphere to reflect sunlight
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Geoengineering News
May 14, 2026, 3:30:42 PM (6 days ago) May 14
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14 May 2026
Stardust's papers linked below:
Paper#01: From Particles to Policy: Technical Building Blocks for Multi-State SAI Coordination
Authors: Roby Yahav, Amyad Spector, Doron Kushnir, and Matthew C. Waxman
Abstract
Stratospheric aerosol injection (SAI) is a solar radiation modification technique, proposed as an interim measure to offset warming while greenhouse gas (GHG) emissions are reduced. This paper discusses a possible SAI implementation route - an alternative to sulfate aerosols formed in situ - based on engineered solid particles having dedicated properties such as size, composition, surface chemistry, and traceable origin, supporting safety, controllability, and functionality needed for SAI systems. These engineered properties also open up options for any future multi-state coordination of SAI through two technical building blocks: (1) the SAI-induced radiative forcing (SRF) - the magnitude of the cooling effect attributable specifically to the SAI layer - as an operator-independent quantity, derivable from direct aerosol-layer measurements; and (2) particle traceability through identifying signatures embedded at production. Both could feed into a shared, publicly accessible monitoring database open to independent interrogation, addressing several governance challenges by anchoring compliance assessments in measurable parameters. Drawing on precedents from the Montreal Protocol, IAEA safeguards, and other regimes, we show that shared technical metrics have historically enabled multi-state cooperation, and we argue the same could apply to SAI. We describe a phased pathway in which the technical capabilities and coordination practices that would use them are developed and tested together, at scales orders of magnitude below operational deployment. To be clear - we regard SAI deployment as premature; the conditions under which it might be considered have not been met. The paper does not propose a governance framework; rather, it identifies technical infrastructure that could support a wide range of such frameworks.
Paper#02: Engineered amorphous silica particles with minimized heterogeneous uptake behavior for stratospheric aerosol injection
Authors: Tzemah Kislev, Alina Berkman, Gal Schwartz Roitman, Kariene Neiman, Anais Lostier, Subhadarsi Nayak, Amir Goldbourt, David Avnir, Manolis N. Romanias
Abstract
Solar radiation modification via stratospheric aerosol injection (SAI) has been proposed as a potential approach to partially offset anthropogenic climate warming. However, its feasibility is constrained by uncertainties associated with heterogeneous interactions between aerosol particles and trace gases relevant to stratospheric ozone chemistry.
Here, we develop and experimentally evaluate engineered amorphous silica particles designed for SAI-relevant functionality, with particular emphasis on minimizing heterogeneous uptake behavior under stratospheric conditions. Controlled synthesis, thermal treatment, and surface functionalization yield dense, spherical particles with reduced densities of accessible surface silanol groups, substantial hydrophobic surface functionalization, and stable hydrophobic characteristics under ultraviolet (UV) irradiation and exposure to acidic species.
Heterogeneous uptake of key trace gases, including HCl, HNO3, N2O5, and O3, was measured under low-temperature conditions relevant to the lower stratosphere. The engineered particles exhibit substantially reduced uptake compared with crystalline quartz, which is used here as a low-uptake benchmark surface, with uptake coefficients approaching experimental detection limits and interactions dominated primarily by weak surface association.
These findings extend benchmark measurements identifying amorphous silica as a low-uptake reference material and demonstrate that heterogeneous uptake behavior can be further suppressed through controlled surface engineering. The consistently low uptake observed across multiple trace gases suggests a substantially reduced potential for sustained heterogeneous gas–surface processing under representative stratospheric conditions, supporting the potential compatibility of such particles with ozone-relevant atmospheric chemistry.
Paper#03: Efficient dispersal of submicron solid particles for stratospheric aerosol injection
Authors: Yair Segev, Eitan Y. Levine, Yair Bar-Yoseph, Ori Amsallem, Yuval Dagan, Elad Laor, Shai Rahamim, Alon Luski, Eran Daniel, Eshani Hettiarachchi, Amyad Spector
Abstract
Stratospheric aerosol injection (SAI) using solid particles has been proposed as an alternative to sulfate aerosols for solar radiation modification, but practical deployment faces challenges in efficiently deagglomerating and dispersing powders as submicron particles. Here we experimentally demonstrate pneumatic dispersal of particles in optically optimal size ranges for SAI. Using spherical amorphous silica particles, we find that applying a hydrophobic surface treatment substantially improves dispersibility, with 50-85% of treated particle mass achieving submicron sizes compared to 10% for untreated particles. We compare the dispersal of treated particles of different sizes and find that 300 nm particles provide superior deagglomeration than 500 nm particles for the same air consumption. Theoretical modeling of the adhesion forces between particles, combined with surface roughness parameters extracted from atomic force microscopy, successfully predicted the relative dispersibility across different particle types. The pneumatic dispersal system achieved optimal performance at air-to-powder mass ratios of about 10:1. Using the measured dispersed particle sizes, we provide a scaling analysis suggesting that a feasibly sized fleet of dispersal aircraft could provide an aerosol layer sufficient for meaningful climate intervention. These results demonstrate that hydrophobic surface treatment and pneumatic dispersal can overcome the agglomeration challenge for SAI with solid particles.
Paper#04: Composite sub-micron solid particles engineered to enable safe, controllable, efficient, and practical SAI
Authors: Stardust Labs
Abstract
The properties of candidate particles for solar radiation management (SRM) through stratospheric aerosol injection (SAI) should comply with safety, controllability, and functionality requirements. Following the proposal in [1] of safety and controllability requirements, we define here a set of functionality requirements on the particles’ properties - optical properties, stratospheric residence time, scalable manufacturing compatibility, and aerial dispersion compatibility- that, if met, ensure the feasibility of practical implementation, providing reflection of ∼ 1% of the solar flux. We then present design principles and fabrication methods for sub-micron solid particles that may enable satisfying the combined requirements.
These requirements do not identify a unique solution, but favor sub-micron particles with tightly controlled size distributions and stable properties over their stratospheric lifetime, and motivate a composite design where the bulk core composition is selected primarily for optimal radiative properties and the outer shell surface is engineered to control atmospheric chemistry and aging, and enhance aerial dispersion compatibility. We present two specific particle designs that are viable for meeting the coupled requirements: amorphous silica spheres and calcium-carbonate cores surrounded by spherical silica shells (both with appropriate surface treatment). The former is at an advanced stage of experimental verification (described in detail in a companion paper) of meeting all requirements, provides a practical platform for surface engineering, and will enable reaching a substantial fraction of ∼1% solar flux reflection. The latter is under development and will enable reaching > 1% reflection.
Paper#05: Solid-particle stratospheric aerosol injection: a 2-D modelling exploration of the design space
Authors: Yoav Lederer, Nahliel Wygoda, Dorri Halbertal and Brian E. J. Rose
Abstract
Solid-particle alternatives to sulfate for stratospheric aerosol injection (SAI) span a broad design space: particle composition and morphology, sensitivities to agglomerate microphysics, and injection strategies in latitude, altitude, and season. Spanning this space with three-dimensional chemistry–climate models is practically prohibitive. To enable such sweeps, we present a two-dimensional (2-D) zonal-mean modelling framework for SAI with solid-particle materials. ERA5-constrained stratospheric transport is coupled with explicit aerosol microphysics and a modified RRTMG radiative transfer scheme, with each component extensively validated. Focusing on silica and calcite, we use the framework to explore SAI performance across two complementary axes: material properties together with monomer and agglomerate microphysics, and injection strategies in space and time. Tropical injection maximises radiative forcing efficacy but pays the largest in-layer heating penalty. Coagulation in the tropical confinement amplifies aggregate diameters and partially offsets the residence-time advantage. A seasonal (alternating-summer-hemisphere) schedule delivers a modest ∼ 10–30% mid-latitude cooling-efficacy gain over symmetric injection, but at a comparable mid-latitude heating-cost penalty. For IR-absorbing materials such as silica, symmetric mid-latitude injection reduces stratospheric heating with limited loss of efficacy; calcite’s negligible IR absorption keeps the heating penalty an order of magnitude lower across all injection strategies considered.
Paper#06: Uptake of stratospheric species on minerals proposed for stratospheric aerosol injection
Authors: Anais Lostier, Yair Segev, Tzemah Kislev, Gal Schwartz Roitman, Nadine Locoge, Manolis N. Romanias
Abstract
Solid mineral-based particles have been proposed as alternatives to sulfates for climate intervention by stratospheric aerosol injection, as a possible means for improving optical or chemical characteristics to thereby minimize risks and uncertainties. However, the heterogeneous reactivity of solid particles toward stratospheric trace gases, and possible implications to the ozone layer, is currently not fully constrained, particularly at stratospheric concentrations. Here we present a systematic comparative study of the uptake of nitric acid (HNO3), hydrogen chloride (HCl), and nitrogen dioxide (NO2) on four mineral surrogates, calcite, alumina, crystalline silica (quartz), and amorphous silica, using complementary Knudsen cell and flow-through reactor techniques. We find that NO2 uptake is relatively weak on all surfaces, with estimated heterogeneous removal timescales indicating negligible direct impact on stratospheric nitrogen chemistry. Conversely, measuring HCl uptake over a concentration range spanning five orders of magnitude, we find substantial uptake with a pronounced concentration dependence consistent with surface site-limited Langmuir adsorption. Extracting adsorption isotherms, we find that the surface coverage of HCl at stratospheric concentrations differs by four orders of magnitude between the surfaces, with calcite adsorbing the most and amorphous silica the least, suggesting a dominant role of surface acid-base character. Using HCl surface coverage as a proxy for the reactive uptake coefficient of ClONO2, we estimate that amorphous silica could produce substantially lower ozone depletion due to chlorine activation than calcite or alumina under equivalent injection scenarios. We also find a marked difference in uptake between the crystalline and amorphous forms of silica, underscoring the sensitivity of heterogeneous chemistry to surface microstructure and the importance of selecting particles with low-reactivity surfaces, in addition to the consideration of bulk characteristics. Our findings motivate the development of particles with surfaces tailored for minimizing SAI risks and uncertainties, including minimal reactivity with stratospheric gases and background sulfate aerosols.
Paper#07: Feasibility Study for Industrial Scale Submicronic Engineered Amorphous Silica Particle (SEASP) Manufacturing for Stratospheric Aerosol Injection (SAI)
Authors: Tamir Kuzurbardov, Avi Yaverboim, Tzemah Kislev, Eli Abramov
Abstract
A feasibility study is presented for scaling up manufacturing of Submicronic Engineered Amorphous Silica Particles (SEASP) to industrial throughput required for Stratospheric Aerosol Injection (SAI), with properties meeting safety and functionality requirements [1,2]. Manufacturing is based on wet-precipitation chemistry via a TEOS-based St¨ober sol-gel route. The goal of this study is to assess realistic timescale and cost of manufacturing at relevant scales for SAI, analyze the main risks and bottlenecks, and identify mitigation strategies for them. Scale-up is assessed across the components necessary to establish feasibility: process scalability, material availability, infrastructure, operations, energy consumption, waste and by-products, timeline, and cost.
Based on relevant available data on SEASP manufacturing and precipitated-silica scale-up benchmarks, it is assessed that scaling up manufacturing from the current specialty chemical scale of 0.1 kt/yr to a single module of 250 kt/yr is expected to be completed within approximately five years. No fundamental technology or process show-stopper was identified, provided that demand, logistics, financing, industrial partnering, and regional manufacturing hubs are developed in parallel.
Plant replication of the 250 kt/yr module to regional hub manufacturing at a climate-relevant scale of 1 Mt/yr, sufficient to offset a significant fraction of decadal warming, is expected to be completed within two additional years. An outlook is provided for further expansion toward climate-scale 10 Mt/yr manufacturing capacity, required for approximately 1% solar-flux modification. This climate-scale capacity is expected to be based on replicating the regional 1 Mt/yr hubs.
TEOS precursor availability is identified as the principal scale-up risk, and an integrated TEOSSEASP manufacturing concept is presented to address this risk. Unit economics of approximately USD 5/kg, dominated primarily by raw-material costs, appear plausible, with further reductions possible through process optimization, solvent recycling, continuous operation, and precursor-route improvements.
Source: Stardust
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