Biological Stability of Organic Fraction of Municipal Solid Wastes During Composting Processes

The article shows results of monitoring of a Sicilian composting plant (southern Italy). In particular, the biological stability of the organic fraction of municipal solid wastes has been monitored. Two experimental periods have been carried out: (1) plant start-up and (2) first operation period. The biological stability has been evaluated throughout the dynamic respiration index (DRI). This index was determined at different stages of process, for each phase. To our knowledge, no work has been previously published on the monitoring of composting plants in southern Italy. This work has the originality of using the DRI measured data for improving operation of a full-scale composting plant, rarely adopted in literature. Results show that storage time of the untreated matrix strongly influences performance of the composting process in terms of biological stability. At high value of storage time (>4 to 5 days) the pH decreased due to acetic acid production. Consequently, inhibition of the aerobic stabilization process takes place. Indeed, after treatment the DRI value was still quite high: 1,709 and 2,650mgO(2)/(kgVS.h) during start-up and start-up and first operation period, respectively. Results also reveal the need of using all operational parameters as reference for regulation of ventilation systems.