Sustainability of co-compost products from FS and OSW (Tanzania)

This study assessed the environmental and socio-economic sustainability of co- composting faecal sludge (FS) and organic solid waste (OSW) in Shinyanga. The study focused on evaluating the health risks associated with consuming Amaranthus mangostanus grown in co-compost soil. This work also compared its productivity with conventional fertilizers, and assessed the overall sustainability of co-composting. The study’s findings indicated that consuming Amaranthus mangostanus sp. from various soils presented negligible carcinogenic risks for both adults and children, with carcinogenic risk factors below 10-6. However, children aged 6-12 showed increased susceptibility to certain toxic elements, nearing the 10-6 limit. Additionally, the study found a high amount of fecal coliform (E. coli) in organic fertilizers, with the highest concentration detected in soil mixed with mature compost at 106 counts/gram, exceeding the limit set by the US Composting Council, which is 103 counts/gram. Soil with immature compost facilitated the growth of Amaranthus mangostanus sp., outperforming all other soils. Immature compost-enriched soil displayed higher nitrogen levels of 7 ppm, resulting in improved soil structure, water retention, aeration, and drainage. The social survey revealed high awareness and acceptance of co- compost derived from fecal sludge and market waste. It was concluded that co- composting offers a promising waste management solution in Shinyanga.