Co-composting of Green Waste Mixed with Unprocessed and Processed Food Waste: Influence on the Composting Process and Product Quality

Green waste (GW) represents a large fraction of municipal solid waste (MSW) and has increased significantly with the rapid development of urban green areas in some countries. Composting is an appropriate method for the treatment and recovery of these wastes. However, the high content of lignocellulosic substances in GW is known to slow down the decomposition process. This research evaluated the effect of introducing processed food waste (PFW) and unprocessed food waste (UPFW) on composting of GW, it monitored the process itself and assessed the end-product quality. A field-scale experiment was developed using three treatments: Treatment A (100%GW), Treatment B (40%UPFW + 60%GW) and Treatment C (50%GW + 30%UPFW + 20%PFW). Treatment C reached thermophilic temperatures in a shorter time than the other treatments and maintained those temperatures for longer periods. In addition, treatment C reached ambient temperatures during curing in a shorter time compared to treatments A and B. An improved product quality was observed in treatment C compared to other treatments. For example, products from treatment C had lower ash content, higher concentrations of TOC and PTotal and lower EC values compared to treatments A and B. The final fertility index of the end-product from treatment C was 4.8–5.0, which indicates that the product can be suitable for agricultural use.