SRA

Anaerobic digestion (AD) for biogas production is a resource-efficient and sustainable method to treat organic wastes and obtain renewable energy and an organic fertiliser. High-solid digestion (HSD) provides an opportunity for anaerobic digestion of high-solid materials with less dilution than in the more common wet digestion process. This study examined the performance of an HSD process in plug-flow (PFR) type reactors (PR1 and PR2), developed for continuous HSD processes, compared with that of an HSD process in completely stirred-tank reactors (CSTRs) (CR1, CR2 and CR3) commonly used for wet AD. The HSD process was run in thermophilic conditions (52oC) and with a mixture of household waste, garden waste and agricultural residues (total solids content 27-28%). Results from 16S rRNA gene sequencing showed a significant difference in the bacterial community between reactor types. Samples were collected at six time-points from the CSTRs and five time-points from the PFRs. Samples were sequenced in duplicates. In addition, samples were taken from two different positions along the PFRs (sections S1 and S3) during three of the sampling time-points to evaluate if separation of the microbial population was obtained across the plug-flow.