Changes in municipal solid waste pore structure during degradation: Analysis of synthetic waste using X-ray computed...

In solid wastes, pores provide passages for leachate and biogas flows, and room for microbial activities. In this study, the pores in the solid wastes of synthetic solid wastes were measured using X-ray computed microtomography to explore their structural characteristics during degradation. The synthetic municipal solid waste (MSW) column was inoculated with microorganisms obtained from leachate sampling and X-ray digital images of MSW were taken on the 2nd and 260th days after inoculation. The results show that the porosity dropped sharply, and the volume and path number of the connected pores reduced while those of disconnected pores increased. However, the corresponding characteristics in the blank MSWs changed only slightly. For the probability density distributions of the inoculated column, both the pore size (fitted well by y = 0.49e-0.49x, r2 = 0.96) as well as the throat area (fitted well by y = 0.54e-0.54x, r2 = 0.96) changed, depicting an exponential decay at the primary stage and a unimodal distribution at the degraded stage. The pore path length and coordination number also changed. These indicated that the pore structure of MSWs underwent considerable evolution during degradation; the changes can be attributed primarily to microbial activity instead of physical effects.