Enzyme-treated rock particles are accelerating carbon sequestration

In a first-of-its-kind trial project, a CO₂-removal method known as enhanced rock weathering (ERW) is being combined with biotechnology to accelerate atmospheric CO₂ sequestration. FabricNano (London, U.K.; www.fabricnano.com) and Veolia (Paris, France; www.veolia.com) have embarked on a partnership wherein enzymes applied to rocks are being used to permanently store atmospheric CO₂ via ERW. This ERW trial, located near Bicester, U.K., involves large-particle basalt rock fines sourced from local mining operations. When spread over the ground, the rocks react with CO₂ in rainwater to permanently store it.

Currently, ERW processes are limited by mass transfer (CO₂ diffusion into water over rock surface area) and by the equilibrium rate of carbonic acid formation when CO₂ is dissolved in water, but immobilizing enzymes onto rocks promises to drastically shorten the timescale for carbon sequestration, and also enable the use of larger rock particles.

“Applying the enzyme to the surface of ultramafic silicate rocks (most commonly basalt) shifts the equilibrium from mostly CO₂ and water to mostly carbonic acid, which then reacts with the salt in the rock, such as calcium, magnesium or sodium, to neutralize the acid, thereby weathering the rock,” says Grant Aarons, CEO and co-founder of FabricNano. For the ERW trials, a recombinantly expressed carbonic anhydrase enzyme has been acquired as protein powder and then reformulated to optimize immobilization to silicate rocks. Aarons emphasizes that this enzyme is commonly encountered in agricultural settings, as it is naturally released into soil by microorganisms.

“We use 1-L reactors to accelerate ERW testing in the laboratory where we can feed CO₂ at higher rates than exist in the ambient atmosphere,” says Aarons. This trial is the next step in moving from the laboratory to the field. “We are planning more than ten additional trial sites with Veolia this year, where each site is 5–30 hectares in size,” says Aarons.