Enhancing the economic potential of organic waste by co-composting using optimized mixing ratios toward a circular economy

This study successfully applied co-composting to municipal organic waste, faecal sludge and chicken manure feedstocks using optimized mixing ratios to yield high-end organic fertilizers. Nine (9) compost piles with different mixing ratios were prepared. Composting was monitored against physicochemical and nutritive parameters for 13 weeks. At curing, pH values and organic matter for piles were 5.5 to 9.0 and 15–45%, respectively. C/N ratio, nitrogen, phosphorus, and potassium levels of piles were satisfactory. Heavy metals Ni, Zn, Cu and Pb, met the EU standards except for Cd whose concentration was 12.9 to 73.2 mg/kg. Self-heating test results were comparable to the ambient temperature, and respiration tests showed values < 2 mg CO 2 •C/g organic carbon/day, indicating the cured compost is very stable. Although pathogens were present in the compost piles, the piles passed the phytotoxicity test with a minimum of 80.09%. Germination Index values were greater than 80% making the compost mature and phytotoxin-free. The variations between the cured compost piles were statistically significant, with a p-value < 0.05.