Rock-Candy Carbon Capture Could Sweeten Environmental Management

A new carbon sink on the horizon.

STARTER STATS

• Direct air capture currently costs $600–$1000 USD per tonne of CO₂ removed at commercial scale.

• Earth's atmosphere holds ~420 ppm of CO₂, making capture energy-intensive.

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Cheaper Carbon Capture with Passive Crystallization

Researchers have unveiled a new direct air capture method that doesn’t rely on giant fans and industrial blowers. The method developed by an engineering team at the University of Toronto uses evaporative crystallization to passively pull carbon dioxide from the air and form solid carbonate crystals. Their findings could potentially reduce capital costs for capture plants by up to 40%.

"Because we have a very thin layer of extremely concentrated potassium hydroxide, the rate at which it reacts with carbon dioxide speeds way up. We can capture carbon at a much higher rate than with the more dilute solutions used in today’s systems."

— Dongha Kim

The Method: It All Comes Down to Evaporation

The new system looks a lot like making rock candy. Long polypropylene fibres draw a potassium hydroxide solution upward by capillary action. As air flows past, water evaporates, and the CO₂-rich solution concentrates until potassium carbonate crystals form on the fibres.

The team avoids complex liquid regeneration steps typically used in conventional direct-air capture. The carbonate precipitates as a solid salt rather than remaining dissolved, simplifying operations and reducing material input.

The Core Findings: Removing Economic Barriers

The captured carbonate can be processed electrochemically to release pure CO₂ for storage. It can be reused or converted into other fuels and chemicals.

Early analysis suggests that operating costs currently align with existing approaches. However, the new method’s simplified hardware could significantly reduce upfront plant costs, which pose a barrier to industrial-scale deployment.

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