Anaerobic degradation of municipal organic waste among others composting techniques improves N cycling through waste-soil-plant continuum

This study aimed to examine the effect of composting techniques of municipal organic solid waste (MSW) for (i) total carbon (C), nitrogen (N) losses, and changes in its chemical characteristics during composting phase and (ii) value of the composted materials as fertilizer when applied to vegetables. Treatments included: aerobic composting (AC), anaerobic composting (ANC), co-composting (CC) and open dumping (OD) for 4 months. During the composting phase, about 61, 50, 35, and 13% of the initial N was lost from CC, AC, OD, and ANC, respectively. The respective values in case of total C loss were 17, 13, 14 and 11%. After field application, about 41% of the applied organic N was mineralized from ANC material, whereas the respective values for OD, CC and AC were 25-26, 15-16, and 12-19%. Consequently, dry matter (DM) yield and vegetable N uptake from the resultant compost were in the order ANC>OD>CC>AC. Moreover, vegetable apparent N recovery (ANRf) was the highest from ANC (spinach: 36 and carrot: 45%) followed by OD (26 and 34%), CC (18 and 26%) and AC (18 and 24%) material. When composting N losses were taken into account during calculations, about 31-39, 17-22, 9-10, and 7-12% of the N collected from filth depots ended up in plants from ANC, OD, CC and AC, respectively. We concluded that ANC results in least C and N losses during the composting phase and greatest N mineralization in the soil, which enhances vegetable yield, N recovery and thereby the N cycling through waste-soil-plant continuum.