Equatic, an American cleantech company founded in 2021, develops an electrolytic process for atmospheric carbon dioxide (CO₂) removal that leverages the size and scale of the oceans. The process stabilizes CO₂ permanently in the form of dissolved bicarbonate ions (CO₃²⁻) in seawater, and in the form of solid mineral carbonates (CaCO₃ and MgCO₃). Equatic's technology has the potential to combat climate change commercially and power the green economy by coupling carbon dioxide removal from the atmosphere with the generation of green hydrogen at the lowest costs.
(This article contains 3 diagrams and 1888 words.)
Challenges: climate change and carbon removal
CO₂ 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.
The Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The average global temperature has already risen by between 0.8 ºC and 1.2 ºC. 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.
Ocean carbon sequestration
The oceans cover more than 70% of the earth's surface. They store a lot of CO₂. At its current average pH of 8.1, seawater contains 150 times more CO₂ than an equal volume of the air. The seawater captures atmospheric CO₂ and lock it in the form of ions (HCO₃⁻ and CO₃²⁻) and solid precipitates (CaCO₃ and MgCO₃) according to the following reversible chemical reactions:
CO₂ + H₂O ⇆ H₂CO₃
H₂CO₃ ⇆ H⁺ + HCO₃⁻
HCO₃⁻ ⇆ H⁺ + CO₃²⁻
CO₃²⁻ + Ca²⁺ ⇆ CaCO₃↓
CO₃²⁻ + Mg²⁺ ⇆ MgCO₃↓
The ocean is the largest carbon sink on the planet, absorbing about 40% of the CO₂ emitted by human activities. The oceans are an important buffer in climate change.
As the atmospheric CO₂ concentration rises, the ocean absorbs more CO₂. As the oceans absorb more CO₂ than they can handle, it could lead to several potential consequences, such as ocean acidification and its negative impacts on marine life and ecosystems.
Ocean Alkalinity Enhancement is one of the important Negative emissions technologies (NETs) to accelerate this natural ocean carbon capture process. NETs are important because they can help companies, sectors, or countries remove more CO₂ from the atmosphere than they emit. According to climate models, a significant deployment of NETs will be needed to prevent catastrophic ocean acidification and global warming beyond 1.5 ºC.
Ocean Alkalinity Enhancement involves the addition of alkaline substances, such as NaOH, to seawater to enhance the ocean's natural carbon sink and helps to deacidify the ocean. The process transforms dissolved CO₂ into bicarbonate ions (HCO₃⁻) at a high pH according to the chemical reaction:
CO₂ + OH⁻ → HCO₃⁻
Equatic Technology
Equatic has developed a transformative electrolytic method for CO₂ removal that leverages the high concentration of CO₂ in seawater and the enormous abundance of Ca²⁺ and Mg²⁺ cations. The in-situ alkalization of seawater in electrolytic flow reactors forces CO₂ mineralization via reactions between dissolved CO₂ and Ca²⁺ and Mg²⁺ to permanently lock CO₂ as stable carbonate solids and/or as aqueous bicarbonates. The process also produces green hydrogen (H₂) that can be used to fuel the process during intermittency or sold to generate revenue.
Equatic carbon removal system
The diagram below depicts the carbon removal system with the electrolytic flow reactor.
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