Co-composting, a circular economy approach to waste management, has economic potential and environmental benefits through nutrient recycling and waste minimization. This research is based on the hypothesis that co-composting municipal organic waste, chicken manure, and faecal sludge feedstocks using ratio modelling will yield compost with economic potential. The study therefore investigated the quality of compost produced by co-composting municipal organic waste, chicken manure, and faecal sludge via ratio modelling in terms of the compost nutrient levels, microbial activities, compost maturity and heavy metals as a cheaper alternative for farming purposes. Nine compost piles of different substrate ratios were prepared. The pristine moisture content of feedstocks was maintained, however, moisture content of the piles was adjusted during the composting process to obtain optimal levels. Compost maturity was 91 days. pH and organic matter ranged from 7.7 to 8.4 and 19.75 to 28.10% respectively. C/N ratio, N, P, and K levels were satisfactory. Micronutrients such as Ni, Zn, Cu, and Pb were within acceptable European Union standards. Germination indices were > 80% implying that composts were mature and phytotoxin free. Respiration rate was 0.2 to 1.2 mg CO2∙C/g organic carbon/day and acceptable. Self-heat was at 30 °C ambient temperature. Although the optimum moisture content of 50 to 60% was not achieved, the overall compost quality was satisfactory. The contribution of moisture content, organic matter, organic carbon, C/N ratio, germination index, respiration rates, and self-heat to variations in compost quality was statistically significant at p < 0.05. Three principal components (PC) explained 71.5% of the variations in compost quality. PC1 explained 33.3%, PC2 23.9%, and PC3 14.3%. The substrate ratios applied through ratio modelling, suggest the feasibility of large-scale production and safe use of co-compost from organic waste, chicken manure and faecal sludge. It is recommended that further studies should explore varying the moisture content to achieve the optimum range.
