Valorization of faecal sludge and organic waste in Bobo-Dioulasso, Burkina Faso to improve sanitation, enhance soil and improve agricultural productivity

Abstract

Burkina Faso is one of the countries in Africa that has problems managing organic waste such as faecal sludge. These problems are mainly related to the lack of sanitation infrastructure in most cities in the country. This study was, therefore, designed to assess the potential of sustainably managing faecal sludge and other organic wastes in Bobo-Dioulasso through biogas technology to recover energy and organic fertilizer for agricultural production. Samples of faecal sludge from nine different trucks in one-litre plastic bottles, a two-litre abattoir waste and 1 kg of fruit and vegetable waste were also collected and their physicochemical parameters were analysed at ONEA Laboratory. The laboratory results reveal that 100% faecal sludge (FS) introduced into the digester after 25 days of mesophilic digestion at 37 °C produced 4.37 l/kg of biogas, with 23% of CH4 and 1.3% and 44.2% of Total Solids (TS) and Volatile Solids (VS) respectively. A faecal sludge of 90% with slaughterhouse waste of 10% introduced yielded 17.3 l/kg of biogas with 44.4% of CH4 content and 2.38% and 61.42% of TS and VS respectively. A combination of 90% faecal sludge with 10% of fruits and vegetables waste produced 29.4 l/ kg of biogas with 42% of CH4, 4.72% of TS and 72.18% of VS. However, it was found that the settled sludge and semi-solid material collected for the same tests with respective TS (8.62%) and VS (69.1%) produced a good yield of 54.4 l/kg of biogas with 51% of CH4. The study also revealed that decantation of the waste material was more profitable for energy recovery from faecal sludge. Field surveys to assess social impacts showed that 82.8% of the households were in support of a biogas production plant and are willing to pay for biogas for cooking. The study concludes that the valorization of faecal sludge into biogas is a good solution to solving sanitation problems and contributes to energy supply as well as improving agricultural production in Bobo-Dioulasso and beyond.