Evaluation of anaerobic digestion process for derived-MBT organic solid wastes

Semi-continuous and batch system bench-scale reactors, at mesophilic temperature, were set-up to investigate the performance of anaerobic digestion treating mixed waste from municipal solid collection, derived from two large-scale mechanical biological treatment (MBT) plant, in the UK. The biogas yield using the semi-continuous reactor was determined to be between 300 and 410 mL/gVS with average methane content of 51% and average volatile solid destruction of 70%. During the batch system, the biogas yield was determined to be between 200 and 220 mL/gVS, with average methane content of 54% and volatile destruction of 70%, at the end of the digestion trial. Heavy metal analysis indicated accumulation of some elements during the treatment; however, final values were lower than risk limits. Microbial community profile through phospholipid fatty acids (PLFA) analysis was investigated to determine structure shifts between different treatment and over time; although no statistical significance (p>0.05) was detected, PLFA peaks presented a shift in the community profile when comparing two different treatment applied. The community structure was demonstrated to be stable and resilient, able to cope with different parameters and stress. The results of this study indicate that mixed municipal solid waste is favourable to be treated in anaerobic digestion plants with mechanical biological treatment (MBT) with regards to its biogas yield and waste size reduction through volatile solid destruction.