Effect of Feedstock Composition on Physicochemical and Microbiological Properties of Compost from Tuber and Acidic Fruit Peel Residues
Abstract
The application of compost as a soil amendment can reduce dependence on chemical fertilizers, improve agricultural yields, and minimize the disposal of organic waste in landfills. However, the agronomic value of the resulting compost is strongly conditioned by the biochemical composition of the feedstock and the processing protocol. This study investigated how contrasting feedstocks affect thermal dynamics, physicochemical maturation, and microbiological safety indicators in two composting systems. Compost 1 (C1) was prepared from tuber peels of cassava (Manihot esculenta), potato (Solanum tuberosum), and carrot (Daucus carota) . In contrast, Compost 2 (C2) was prepared from acidic fruit peels of orange (Citrus sinensis), lemon (Citrus limon), pineapple (Ananas comosus), and passion fruit (Passiflora edulis). In both cases, sawdust and pruning residues were added as bulking agents. C1 reached a peak temperature of 69.1 °C and a final C/N ratio of 16.18, while C2 peaked at 57.5 °C and ended with a C/N ratio of 56.12. C2 presented higher moisture (74.01% vs 59.03% in C1) and higher available phosphorus (66.67 vs 45.83 ppm). Presumptive isolates compatible with Salmonella, Escherichia coli, and Fusarium were detected at process completion in one or both systems, identified at the genus level by selective media and morphology. Feedstock composition generated distinct composting trajectories that required differentiated management strategies; tuber-based substrates demanded alkalinity control to reduce nitrogen losses, whereas acidic fruit-peel mixtures required moisture adjustment and improved thermal management. The results demonstrate that physicochemical maturity and microbiological safety represent complementary but independent dimensions of compost quality, highlighting the need for direct microbiological verification even when conventional maturity indicators are achieved.