Enrichment and acclimation of an anaerobic mesophilic microorganism’s inoculum for standardization of BMP assays

[Display omitted] •An appropriate inoculant is crucial for accurate BMP predictions.•A method to develop mesophilic inoculum to attend VDI 4630.•Biogas efficiency ranged from 89% to 99%.•Methanosarcinales was the dominant genus in the acclimated inoculum. Appropriate enrichment of anaerobic microorganism’s consortium is crucial for accurate biochemical methane potential (BMP) assays. An alternative method to produce and maintain a mesophilic methanogenic inoculum was demonstrated. Three sources of inoculum were mixed and acclimated for 857days in order to reach steady conditions (pH=7.90±0.46; VS/TS>50%; VFA/alkalinity=0.16±0.04gAcetic Acid/gCaCO3). Biogas yield >80% was obtained after 70days of inoculum acclimation in comparison to standard cellulose (>600mLN/gVS). Methanogen community analysis based on 16S rDNA of the inoculum revealed Archaea concentration of 3×1012 gene copies/g (Methanobacteriales 8×1010; Methanomicrobiales 8×1010; and Methanosarcinales 4×1011 gene copies/g). The proposed method for development and maintenance of microorganism enrichment inoculum demonstrates consistent BMP data which is a requirement for dependable prediction of biogas production at field scale operations.