Most existing carbon-dioxide removal (CDR) approaches have focused on air, but the volumetric concentration of dissolved inorganic CO2 in surface water is much higher (150X) than its concentration in the atmosphere. Removing CO2 from water could prove to be a more effective approach, because of the ocean-atmosphere equilibrium — decarbonized water can pull CO2 from the atmosphere.
Among those pursuing the approach is CarbonBlue (Haifa, Israel; carbonblue.cc), a company focused on reducing industrial costs while also lowering carbon footprint. CarbonBlue has installed the world’s first pilot plant for removing carbon dioxide from water at a desalination facility in Ma’agan Michael, Israel (photo).
With its proprietary reactor, CarbonBlue has shown the ability to convert dissolved carbon dioxide into precipitated calcium carbonate (PCC), a widely used industrial material, using calcium hydroxide (slaked lime). The process removes carbonate and bicarbonate ions from the seawater and increases its pH, prolonging the lifetimes of the reverse osmosis membranes and lowering desalination costs. Simultaneously, the formation of PCC sequesters CO2 from the water, allowing the seawater to pull CO2 from the atmosphere.
The company’s technology is a novel take on the process of lime-softening of water, in which calcium cations combine with dissolved carbonate anions to form CaCO3 as a solid. “The chemistry of the lime-softening process has been understood for quite some time,” explains CarbonBlue co-founder Dan Deviri, “but the problem has been that the precipitation occurs much too slowly to be industrially useful.”
“What we have been able to design is a fluidized-bed reactor in which the CaCO3 precipitation reaction kinetics are increased dramatically,” Deviri says. To speed the reaction, CarbonBlue has engineered a way to introduce a multitide of nucleation sites for solid CaCO3 to form, and grow on, as it precipitates out of solution. This speeds the reaction to a point that it is industrially viable, Deviri continues.
Now, using 10% of the desalination plant’s intake water, the pilot plant can produce 80 ton/yr of PCC. CarbonBlue plans to scale up to using 100% of the intake water next year, producing upwards of 800 ton/yr. Depending on its purity, PCC can be sold into several important industrial markets, including paints, plastics manufacturing and pharmaceuticals.
“Our goal is for the reactor to be financially viable even without the CDR benefit. We want to help industries grow and improve, while also decarbonizing,” Deviri says. The reactor can also be used at power plants and other industrial facilities where water is used.