Simultaneous medium chain fatty acids production and process carbon emissions reduction in a continuous-flow reactor: Re-understanding of carbon flow distribution

Due to its wide application and high value, the production of medium chain fatty acids (MCFAs) from waste biomass has become one of the worldwide research hotspots. Increasing the carbon element participation from short-chain fatty acids to the form of MCFAs is also conductive to reduce the release of biogas from biological treatment process, because carbon is in the form of MCFAs instead of biogas which directly contribute to process carbon emissions reduction. However, many barriers limiting MCFAs production and application remain to be resolved. Aiming continuous MCFAs production from lactate-rich waste biomass, this study optimized the operation conditions and clarified the main limiting factors and possible mechanisms. The maximum caproic acid concentration of 2.757 g/L were obtained at the Upflow Velocity (ULV) of 1.15 m/h and pH 4.9–5.1. Caproiciproducens, Pseudoramibacter, norank_f_Eubacteriaceae, and Oscillibacter were identified to be the dominant microbial genus responsible for MCFAs production from lactate. The reduction of carbon emissions calculation was also studied in the present processes.