No abstract

The efficiency of millicomposting (M, with millipedes), vermicomposting (V – with earthworms), and traditional composting (C – no invertebrates) of vegetal waste was investigated statistically. Composting took place in closed systems to avoid external interferences during the experiments and allow monitoring of the main physico-chemical parameters. The experiments were replicated six times (n = 6). Quality was assessed via analysis of variance (one-way and Welch procedures) and post-hoc comparisons. Temperature profiles were similar in the three composting types. After 92 days, the compost volume produced in V (51%) decreased more than in M (43%) and C (44%) (p = 0.001). Organic carbon, nitrogen contents, and C/N ratios were also similar (all p > 0.1). Vermicomposting produced humus of higher nutritional quality, whereas M leachates yielded higher nutritional levels and maturity degrees. The Ca content was higher in V and M, while K and Mg were higher in V. pH, Ca, Mg, P2O5, and S contents were higher in V than in C (all p < 0,05). The leachate volumes, electrical conductivity, and Na+ and PO43− contents were similar in the three composting types (p > 0.05). pH, K+ and NH4+ contents were higher while the NO3− was lower in V than in M (all p < 0.005). The only difference observed in C was lower pH when compared to those of V. Although all three composting types were efficient in producing mature, high-quality organic fertilizers, the addition of detritivorous animals improved the composting efficiency and the quality of the final products. This study also attested the potential of millicomposting in producing good-quality liquid fertilizers.