Enzyme-accelerated CO capture and storage (CCS) using paper and pulp residues as co-sequestrating agents.

In the present work, four CaCO-rich solid residues from the pulp and paper industry (lime mud, green liquor sludge, electrostatic precipitator dust, and lime dregs) were assessed for their potential as co-sequestrating agents in carbon capture. Carbonic anhydrase (CA) was added to promote both CO hydration and residue mineral dissolution, offering an enhancement in CO-capture yield under atmospheric (up to 4-fold) and industrial-gas mimic conditions (up to 2.2-fold). Geological CO storage using olivine as a reference material was employed in two stages: one involving mineral dissolution, with leaching of Mg and SiO from olivine; and the second involving mineral carbonation, converting Mg and bicarbonate to MgCO as a permanent storage form of CO. The results showed an enhanced carbonation yield up to 6.9%, when CA was added in the prior CO-capture step. The proposed route underlines the importance of the valorization of industrial residues toward achieving neutral, or even negative emissions in the case of bioenergy-based plants, without the need for energy-intensive compression and long-distance transport of the captured CO. This is a proof of concept for an integrated strategy in which a biocatalyst is applied as a CO-capture promoter while CO storage can be done near industrial sites with adequate geological characteristics.