Feasibility study for developing bacteria-based carbon-neutral mortar-Evaluation of bacterial CO2 capture performance

This study explores the feasibility of a novel bacteria-based mortar and concrete capable of capturing atmospheric CO2 throughout their service life without additional facilities. Isolated bacterial strains–Rhodopseudomonas palustris, Sphingobacterium multivorum, and Lysinibacillus sphaericus–were immobilized on porous expanded vermiculite to preserve viability under the extreme conditions of hardened concrete. The immobilized bacteria exhibited robust CO2 uptake under diverse exposure conditions, including light/dark cycles, relative humidity from 60 % to 99 %, and temperatures ranging from 5 °C to 35 °C. Even at 5 °C, CO2 capture performance was maintained at more than 42 % of that achieved at 20–35 °C. The bacteria-immobilizing expanded vermiculites outperformed biochar specimens, exhibiting significantly higher CO2 capture capacities and a much faster rate of CO2 sequestration, even at the exposure temperature of 5 °C. Viable cell counts confirmed bacterial populations increased by 2.3–3.3 times after CO2 exposure, indicating continued growth and activity. These findings establish a scientific basis for integrating living bacterial systems into construction materials as a pathway toward carbon-neutrality. Future research will focus on developing biological mortars, evaluating their mechanical and durability properties, and ensuring environmental safety. The proposed approach offers a promising direction for transforming concrete into a sustainable material capable of active CO2 capture, potentially revolutionizing the construction industry’s role in climate change mitigation.