Effect of initial bulk density on high-solids anaerobic digestion of MSW: General mechanism.

Initial bulk density (IBD) is an important variable in anaerobic digestion since it defines and optimizes the treatment capacity of a system. This study reveals the mechanism on how IBD might affect anaerobic digestion of waste. Four different IBD values: D1 (500-700kgm-3), D2 (900-1000kgm-3), D3 (1100-1200kgm-3) and D4 (1200-1400kgm-3) were set and tested over a period of 90days in simulated landfill reactors. The main variables affected by the IBD are the methane generation, saturation degree, extraction of organic matter, and the total population of methanogens. The study identified that IBD >1000kgm-3 may have significant effect on methane generation, either prolonging the lag time or completely inhibiting the process. This study provides a new understanding of the anaerobic digestion process in saturated high-solids systems.