Effect of electron donors on CO(2) fixation from a model cement industry flue gas by non‐photosynthetic microbial communities in batch and continuous reactors

The aim of this work was to evaluate the effect of different inorganic compounds as electron donors for the capture of CO(2) from a model cement flue gas CO(2)/O(2)/N(2) (4.2:13.5:82.3% v/v) using a non‐photosynthetic microbial community. The inoculum obtained from a H(2)‐producing reactor was acclimated to CO(2) consumption achieving 100% of CO(2) removal after 45 days. Na(2)S, MnCl(2), NaNO(2), NH(4)Cl, Na(2)S(2)O(3), and FeCl(2) were used as energy source for CO(2) fixation by the acclimated microbial community showing different efficiencies, being Na(2)S the best electron donor evaluated (100% of CO(2) consumption) and FeCl(2) the less effective (28% of CO(2) consumption). In all treatments, acetate and propionate were the main endpoint metabolites. Moreover, scaling the process to a continuous laboratory biotrickling filter using Na(2)S as energy source showed a CO(2) consumption of up to 77%. Analysis of the microbial community showed that Na(2)S and FeCl(2) exerted a strong selection on the microbial members in the community showing significant differences (PERMANOVA, p = 0.0001) compared to the control and the other treatments. Results suggest that the CO(2) fixing pathways used by the microbial community in all treatments were the 3‐hydroxypropionate‐4‐hydroxybutyrate cycle and the Wood‐Ljungdahl pathway.