Microbial ecology of the leach bed anaerobic digestion of unsorted municipal solid waste

The microbial ecology of the sequential, leach-bed, mesophilic anaerobic digestion of unsorted, coarse municipal solid waste (MSW) was examined over 80 days. The methane yield was approximately 75% of the ultimate biochemical methane potential (BMP) of the waste loaded into the digesters. The operational strategy involved a sequence of two digesters containing fresh and anaerobically stabilised MSW respectively. Cell wall phospholipid fatty acid (PLFA) and ether lipid (PLEL) analysis was used to monitor changes in microbial biomass. Both Bacterial and Archaeal biomass were heavily influenced by pH during the two-week start up period. Archaeal biomass peaked just before the methane production rate reached a maximum whereas Bacterial biomass peaked at a later stage. Changes in the phylogenetic diversity of the population were monitored by denaturing gradient gel electrophoresis (DGGE). An analysis of the changes in DGGE banding patterns suggested that rapid start-up of a new reactor was effected by inoculation as well as the provision of buffering capacity from the mature reactor leachate.