Characteristics of co-composts produced from raw faecal sludge and organic market waste in Osun state, southwest Nigeria

Purpose Faecal sludge (FS) and organic market waste (MW) have resources that could be recovered by co-composting though not fully explored under changing climatic conditions in Nigeria. This study explored the characteristics and nutrient quality of co-composts produced from pre-treated FS and MW feedstocks in Nigeria. Methods The study was exploratory and analytical in design and co-composting was purposively selected for resource-recovery. The raw faecal sludge (FS) was harvested from septic tanks of households (50%) and institutions (50%) through mechanical evacuation service trucks and dewatered using 0.1% gradient sand filter. The biodegradable MW was sorted and used for further studies. The dewatered FS (DFS) and MW were mixed in ratios 1:3, 1:5 and 1:7, respectively with DFS and MW as controls. Each of the mixes was made into 1m3 heap and co-composted using the windrow method. The experiments were monitored for 88 days with fortnight composite sampling from each mix (13-weeks). The samples were analyzed for temperature, pH, moisture-contents, micronutrients, macronutrients and pollutants using Standard Methods. Results At maturity, N:P:K (%) indicate good composts at 9: 5: 4, 18: 7: 19 and 3: 3: 1 in the 1: 3, 1: 5 and 1: 7 mixes, respectively, while those of controls were: 19:12:12 (DFS) and 17:14:11(MW) with no significant differences between experimental and control mixes. Also, four factors extracted (pollutants, agronomic, macronutrients and micronutrients), explained 78.2% variability. Conclusion The matured co-compost satisfied nutrients and pollutants quality for agricultural use, recovered organic fertiliser from raw domestic and institutional faecal sludge and market waste.