Physicochemical and Microbiological Properties and Humic Substances of Composts Produced with Food Residues

The consolidation of a wide and effective management system of solid residues, especially biodegradable ones, is one of the great challenges of current society. Composting was evaluated as an option of organic fertilization for soil enrichment, using raw food residues in substitution to bovine manure. The compost piles were built with 30% of biodegradable residues mixed with 70% of ground tree pruning material. The effects of different proportions of food residues (FR) and bovine manure (BM) as source of carbon were tested in 5 treatments (T1 = 15%BM + 15%FR, T2 = 20%BM + 10%FR, T3 = 10%BM + 20%FR, T4 = 30%BM and T5 = control, 30%FR), in randomized blocks, under open field conditions for 90 days. The pH, temperature and moisture content of the compost were measured weekly. The aged compost was evaluated for physicochemical and microbiological properties and carbon contents in the humic substances. The analyses of the results indicated that all studied composts reached the maturation stage with satisfactory contents of humic substances, macronutrients, and micronutrients, indicating that food residues can be used as a source of carbon in compost piles to produce organic fertilizers. The contents of the evaluated chemical contaminants were much lower than those established in the main legislation and current normative instructions and, in terms of contamination by pathogens, there was the absence of total coliforms, thermo tolerant coliforms, and Salmonellas.