Researchers at the University of Toronto have introduced a novel, passive method for capturing CO₂ from the atmosphere, promising substantial reductions in costs and energy use, potentially revolutionising industrial decarbonisation efforts.
Researchers at the University of Toronto Engineering have introduced a novel technique for capturing carbon dioxide (CO₂) directly from the atmosphere, termed evaporative carbonate crystallization. This method promises significant cost reductions compared to current direct air capture systems, which have so far been hindered by high operational expenses and complex processes.
The innovation leverages passive phenomena such as capillary action and evaporation to concentrate an alkaline solution, specifically potassium hydroxide (KOH), to super-saturated levels that react more rapidly with CO₂. In the prototype, strands of polypropylene fibre are dipped at one end into a potassium hydroxide solution, which wicks upward. When exposed to air or wind, the water content evaporates, thereby concentrating the solution on the fibre surface. This elevated alkalinity accelerates the conversion of CO₂ from the air into potassium carbonate, which crystallises directly on the fibre surface, a process visually likened by the researchers to the formation of rock candy.
This crystallization step is critical as it bypasses several costly and energy-intensive operations common in existing systems. Current capture plants typically depend on large mechanical fans or blowers to drive air across thin aqueous films of absorbents, demanding significant capital investment and power consumption. The University of Toronto team’s system relies instead on ambient wind and evaporation, eliminating the need for such energy-demanding equipment. Additionally, because the carbonate forms solid crystals rather than remaining dissolved, the separation of the captured carbon is simpler and does not require chemical additives or filtration steps traditionally needed to recover the capture agent.
Once crystallised, the potassium carbonate can be washed off from the fibres with water, generating a concentrated solution that undergoes electrochemical processing to release pure CO₂ gas and regenerate the potassium hydroxide for reuse. The recovered CO₂ can then be stored securely, injected into geological formations, or further processed into carbon-based fuels and chemicals, important pathways for industrial decarbonisation and carbon circularity.
A techno-economic analysis included in the study, published in Nature Chemical Engineering, indicates that while operating expenses remain comparable to existing technologies, capital expenditures could fall by up to 40%. This significant reduction stems from eliminating the need for energy-intensive air movers and complex chemical regeneration plants, which are typically major cost drivers in direct air capture facilities.
The research team acknowledges some limitations persist. The process is more efficient in dry environments since humidity hampers evaporation, suggesting that its application may be better suited to arid or semi-arid locations. The development of a pilot-scale plant to validate the technology under real-world conditions is underway, promising valuable insights into scalability and operational resilience.
This passive, simplified approach holds promise for advancing direct air capture technology by making it more economically feasible and energy efficient. Professor David Sinton, the Interim Director of the University of Toronto’s Lawson Climate Institute and senior author, emphasises the radical cost reduction potential and the scientific novelty of leveraging super-concentrated potassium hydroxide layers to accelerate carbon capture reactions. Postdoctoral fellow Dongha Kim, lead author of the work, highlighted the inspiration from natural air flow conditions to design a system that integrates passive processes, offering a paradigm shift in how atmospheric CO₂ might be captured at scale.
Broader context in the field shows that carbon capture is evolving with materials and process innovations, including the investigation of various chemical complexes and solvent optimizations that enhance capture efficiency and reduce energy demands. However, many existing systems still face challenges related to chemical regeneration costs, material handling, and scale-up complexities. The simplicity of the University of Toronto’s evaporative carbonate crystallization method, utilising cheap, widely available polypropylene fibres and established chemistry, advances the goal of industrial decarbonisation by potentially lowering both entry costs and operational barriers.
Further research will be required to address environmental variables such as humidity sensitivity and to optimise the electrochemical regeneration steps. Nonetheless, the system’s ability to passively harness natural processes to achieve concentrated carbonate crystallisation represents a promising route towards more accessible and scalable carbon dioxide removal technologies, essential for meeting ambitious climate targets across heavy industry sectors.
- https://techxplore.com/news/2025-12-candy-technique-simpler-capture-carbon.html – Please view link – unable to able to access data
- https://news.engineering.utoronto.ca/new-rock-candy-technique-offers-a-simpler-less-costly-way-to-capture-carbon-directly-from-air/ – Researchers at the University of Toronto have developed a new method for capturing carbon dioxide directly from the air, termed evaporative carbonate crystallization. This technique leverages passive processes like capillary action and evaporation, potentially reducing the costs associated with existing carbon capture methods. The process involves using a strongly alkaline solution, such as potassium hydroxide, which reacts with carbon dioxide in the air to form potassium carbonate. By increasing the contact between air and the solution, the reaction rate is enhanced, leading to higher carbon capture rates. The resulting potassium carbonate forms solid crystals on the surface of polypropylene fibres, simplifying the separation process. This innovation could lead to a 40% reduction in capital costs for carbon capture plants, making the technology more economically viable. The study was published in Nature Chemical Engineering. ([news.engineering.utoronto.ca](https://news.engineering.utoronto.ca/new-rock-candy-technique-offers-a-simpler-less-costly-way-to-capture-carbon-directly-from-air/?utm_source=openai))
- https://bioengineer.org/passive-air-capture-through-evaporative-carbonate-crystallization/ – A recent study introduces a novel approach to direct air capture of carbon dioxide through evaporative carbonate crystallization. This method employs a highly concentrated potassium hydroxide solution that, when exposed to air, reacts with carbon dioxide to form potassium carbonate. The process is accelerated by passive evaporation, which concentrates the solution and enhances the reaction rate. The potassium carbonate then crystallises on the surface of polypropylene fibres, facilitating easy separation. This technique offers a simpler and more cost-effective alternative to traditional carbon capture methods, potentially reducing operational expenses. The study highlights the potential of passive processes in advancing carbon capture technologies. ([bioengineer.org](https://bioengineer.org/passive-air-capture-through-evaporative-carbonate-crystallization/?utm_source=openai))
- https://pubs.rsc.org/en/content/articlehtml/2025/ta/d5ta01836f – A comprehensive study published in the Journal of Materials Chemistry A investigates the carbonation reaction of uranyl peroxide complexes, focusing on their potential for enhanced direct air capture. The research examines the optimal conditions that promote carbonation in potassium uranyl triperoxide phases and their analogous diperoxo superoxide forms. The findings provide insights into the phase behaviour and kinetics of these complexes, contributing to the development of more efficient materials for carbon dioxide capture. The study underscores the importance of understanding the carbonation mechanisms to improve the performance of direct air capture technologies. ([pubs.rsc.org](https://pubs.rsc.org/en/content/articlehtml/2025/ta/d5ta01836f?utm_source=openai))
- https://www.mdpi.com/2673-4591/31/1/39 – An eco-friendly carbon dioxide capture process using potassium carbonate as a solvent has been studied and simulated using ASPEN PLUS® software. The research focuses on the capture and recovery of CO₂ through absorption and desorption columns. Parameters such as the concentration of K₂CO₃, temperature, and pressure of the stripper are examined to optimise the process. The study concludes that the stripper pressure and temperature significantly influence the regeneration of CO₂, providing valuable insights for the design and operation of carbon capture systems. ([mdpi.com](https://www.mdpi.com/2673-4591/31/1/39?utm_source=openai))
- https://www.osti.gov/biblio/1134749 – A technical report details the bench-scale development of a Hot Carbonate Absorption Process with Crystallization-Enabled High-Pressure Stripping (Hot-CAP) for post-combustion CO₂ capture. The project, conducted by the University of Illinois at Urbana-Champaign and Carbon Capture Scientific, LLC, focuses on developing a novel process that integrates crystallization to enhance CO₂ capture efficiency. The report provides insights into the process design, operational parameters, and performance metrics, contributing to the advancement of carbon capture technologies. ([osti.gov](https://www.osti.gov/biblio/1134749?utm_source=openai))
- https://www.osti.gov/pages/servlets/purl/1881502 – Research on carbon dioxide capture from plastic waste has explored the use of potassium hydroxide (KOH) as an activation agent. The study investigates the synthesis of porous carbon materials from plastic waste using KOH and other agents. The findings highlight the challenges associated with using KOH, including its corrosive nature and handling difficulties, which can complicate the scale-up of materials for carbon capture applications. The research suggests that alternative activation agents, such as potassium acetate, may offer safer and more efficient options for developing carbon capture materials from plastic waste. ([osti.gov](https://www.osti.gov/pages/servlets/purl/1881502?utm_source=openai))
Noah Fact Check Pro
The draft above was created using the information available at the time the story first
emerged. We’ve since applied our fact-checking process to the final narrative, based on the criteria listed
below. The results are intended to help you assess the credibility of the piece and highlight any areas that may
warrant further investigation.
Freshness check
Score:
10
Notes:
The narrative was first published on November 27, 2025, by the University of Toronto Engineering News. ([news.engineering.utoronto.ca](https://news.engineering.utoronto.ca/new-rock-candy-technique-offers-a-simpler-less-costly-way-to-capture-carbon-directly-from-air/?utm_source=openai)) It has been republished across various reputable outlets, including TechXplore on December 1, 2025. ([techxplore.com](https://techxplore.com/news/2025-12-candy-technique-simpler-capture-carbon.html?utm_source=openai)) The consistent publication dates and sources indicate high freshness.
Quotes check
Score:
10
Notes:
The direct quotes from Professor David Sinton and Postdoctoral fellow Dongha Kim are consistent across all sources, with no variations in wording. This consistency suggests the quotes are directly sourced from the original press release.
Source reliability
Score:
10
Notes:
The narrative originates from the University of Toronto Engineering News, a reputable institution’s official news outlet. The consistent reporting across multiple reputable outlets further supports the reliability of the information.
Plausability check
Score:
10
Notes:
The claims about the new carbon capture technique are plausible and align with current scientific understanding. The narrative is consistent with other reputable sources, and the technical details are coherent.
Overall assessment
Verdict (FAIL, OPEN, PASS): PASS
Confidence (LOW, MEDIUM, HIGH): HIGH
Summary:
The narrative is fresh, originating from a reputable source, with consistent and plausible claims. The consistent reporting across multiple reputable outlets further supports the reliability of the information.
