44.01, a UK company founded in 2020, has developed a technology for permanently removing CO₂ from the atmosphere by mineralizing it in peridotite rock. By injecting CO₂-saturated water into an underground peridotite layer, the technology shortens the peridotite CO₂ mineralization process to 12 months. Once CO₂ has been mineralized, there is no need for high-pressure underground storage or risk of leaks. Peridotite is abundant across America, Europe, Asia, and Australasia, making the solution scalable.
(This article contains 4 diagrams and 2073 words.)
Challenges: carbon emissions and carbon mineralization
Carbon emissions
Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.
This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security, and ocean acidification.
To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC.
Carbon mineralization
Natural weathering process converts atmospheric CO₂ into rocks, providing reliable, long-term storage. It has been found that the rate of natural carbonation of peridotite is surprisingly fast compared to other types of rock.
Peridotite rocks primarily consist of the silicate minerals olivine and pyroxene. They are the most common rock found in the Earth's mantle and are especially abundant in Oman. They react with CO₂ and H₂O near the Earth's surface to form hydrous silicates (serpentine), Fe-oxides (magnetite), and carbonates (calcite, magnesite, and dolomite) via the following chemical reactions:
Mg₂SiO₄ (olivine) + 2CO₂ → 2MgCO₃ (magnesite) + SiO₂ (quartz);
2Mg₂SiO₄ (olivine) + Mg₂Si₂O₆ (pyroxene) + 4H₂O → 2Mg₃Si₂O₅(OH)₄ (serpentine);
Mg₂SiO₄ (olivine) + CaMgSi₂O₆ (pyroxene) + 2CO₂ + 2H₂O → Mg₃Si₂O₅(OH)₄ (serpentine) + CaCO₃ (calcite) + MgCO₃ (magnesite)
One ton of mantle peridotite could solidify up to 500 kilograms of CO₂, whereas one ton of basalt could only solidify 170 kilograms. Therefore, peridotites are considered as promising reactants for converting atmospheric CO₂ to solid carbonate to mitigate climate change.
Mantle peridotite is typically found beneath the Earth's crust, > 6 km below the seafloor and 40 km below the land surface. It is out of equilibrium with air and water at the Earth's surface. The natural weathering of peridotite is slow and may take thousands of years to convert a considerable amount of CO₂ into carbonate rocks.
Accelerated weathering methods
Accelerated weathering aims to speed up chemical reactions between rocks, water, and air, thereby removing CO₂ from the atmosphere and storing it in solid carbonate minerals. There are two primary approaches to enhanced mineralization: in situ and ex situ mineralizations.
The in situ mineralization method drills deep wells and injects CO₂-rich fluids into suitable rock formations. The injected CO₂ reacts with rocks to form solid carbonate species, realizing underground geologic sequestration.
The ex situ mineralization methods mines fresh rocks, grind them into fine particles, and mineralize CO₂ at elevated pressure and temperature via industrial processes. Ex situ mineralization can be more expensive, costing as much as $600 per ton of CO₂, because it requires lots of fresh rock and energy to power the mineralization reaction.
44.01 Technology
44.01 has developed an in situ mineralization system to mineralize CO₂ into peridotite rock formations in a controlled and efficient manner, thus removing carbon permanently from the atmosphere. 44.01’s CO₂ mineralization system shortens the peridotite CO₂ mineralization process to 12 months. Powered by renewable energy, the system uses CO₂ gas from Direct Air Capture methods and mixes it with cold water to form a CO₂-rich solution. The CO₂-rich water is injected into peridotite rock formation and efficient mineralization reaction occurs by conversion peridotite into magnesite (MgCO₃) and calcite (CaCO₃).
44.01 CO₂ mineralization system
The diagram below depicts the in situ CO₂ mineralization system of 44.01.
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