Industrial scale-up of flue gas bio-mitigation with chemolithotrophs in packed bed reactors: Exploring metabolite synthesis, mass transfer, and techno-economic analysis

Abstract

Elevated emissions of flue gases deteriorate the quality of air, impacting both terrestrial and aquatic ecosystems through their contribution to acid rain and eutrophication. This study examines the bio-mitigation process in a packed bed reactor and its capacity to concurrently decrease the environmental consequences of industrial flue gases (CO2, NO, and SO2) and wastewater by employing mixed bacterial consortia. The highest biomass productivity achieved during the growth phase was 0.002 g L−1 h−1 in the aqueous medium and 0.006 g L−1 h−1 in the PU foam. The highest level of CO2 removal efficiency was 86.60%, while for NO and SO2, it was 77.03% and 82%, respectively. The comprehensive nutrient balance analysis revealed that the flue gas was primarily utilized for biomass assimilation. The FT-IR and GC-MS analysis detected metabolites, including carboxylic acids, esters, and fatty alcohols, that were produced during the process. The NMR study examined alterations in the concentration of metabolites within the cell, indicating metabolic pathways such as the TCA cycle, alanine, pyruvate, butanoate metabolism, and glycolysis. The mass transfer coefficient estimated for the gas-liquid-solid phase was ∼2.0 m s−1 for the flue gases. The scale-up of the reactor based on the mass transfer coefficient up to 20,000 L gives a net present value of $2,66,116.13 with a benefit-to-cost ratio of 1.47. Therefore, this study suggests that employing bacteria is a viable and energy-efficient approach to mitigate the adverse effects of flue gas on air quality. Additionally, it aids industries in minimizing waste and repurposing it for advantageous purposes, thereby diminishing their environmental footprint.