Oxford Sparks

How Do You Convert CO2 to Rock?

The Oxford Sparks podcast explores how captured carbon dioxide can be turned into solid rock through mineralization, featuring physical chemist Dr. Sheree Mao. She explains that carbon capture consists of two stages: extracting CO₂ from the air and then storing it, traditionally by pumping super‑critical CO₂ into underground cavities where it risks leaking back to the atmosphere. Mao’s research focuses on converting that liquid CO₂ into calcium carbonate, a stable mineral, by reacting it with calcium‑rich volcanic rock under controlled temperature, pressure, and confinement conditions. Laboratory proof‑of‑concept work demonstrated overnight crystal growth in basalt samples, and pilot projects such as Copfix in Iceland aim to scale the process to 40,000 tons per year by 2030. Key data points include isotopic analyses showing that 70‑95 % of injected CO₂ mineralizes within two years, and observations that mineral formation occurs within the porous channels of volcanic rock, potentially sealing or fracturing the substrate. Mao emphasizes that while the technology is not a climate‑change silver bullet, it offers a durable, low‑leakage storage solution. The significance lies in providing a long‑term, economically viable storage method that could complement broader negative‑emission strategies. Overcoming scaling hurdles—particularly cost, confinement dynamics, and monitoring—will determine whether mineralization becomes a mainstream component of global carbon‑removal portfolios.