Composting Urban Biowaste: A Potential Solution for Waste Management and Soil Fertility Improvement in Dolisie, Congo

Population growth, urbanization, and changing consumption patterns are contributing to an increase in household waste production, particularly in sub-Saharan Africa. Composting of biowaste presents a sustainable solution by reducing the volume of waste sent to landfills while enriching the soil. The main objective of this study was to evaluate the suitability of solid household biowaste for composting in market garden crops in Dolisie (the Republic of Congo). Specifically, the study aimed to (i) assess the production and management practices of solid household waste in relation to socio-economic factors, (ii) analyze the chemical composition of solid household biowaste and its concentration of trace elements (TEs), and (iii) determine the potential phytotoxicity of solid household biowaste across different production seasons. In this study, wastes were collected from 40 households over a 60-day period, with daily sorting conducted during both the dry and wet seasons. Using a completely randomized design, various compost application rates were incorporated into the soil to conduct a germination test. The quality of the biowaste and compost was evaluated through physicochemical analyses. Results showed that approximately 90% of high-income households received regular waste collection services and practiced waste separation in contrast to middle- and low-income households. The composition of the biowaste was primarily composed of fruit and vegetable scraps, with slight contamination by chromium and cadmium. Temperature, pH, and humidity levels showed similar trends during compost formation in both the rainy and dry seasons. Germination rates were above 80% in all treatments across both seasons, indicating that the compost was mature. Overall, all physicochemical parameters of the compost met established quality standards, and trace element concentrations were below the recommended thresholds. The study concluded that biowaste, once converted into compost, can be safely applied to agricultural soils without posing any risk of phytotoxicity or contamination to crops.