Slow pyrolysis of selected urban biowaste for char production in Dar es Salaam

Most of urban households in Dar es Salaam use charcoal as their main source of energy for cooking. The households in Dar es Salaam use about 70 % of charcoal from the forests which accelerates deforestation. About 4200 tonnes of MSW are generated in Dar es Salaam with high organic fraction. Slow pyrolysis system can be used as treatment of biowaste from MSW to produce char for making charcoal briquette. Slow pyrolysis experimental unit was designed, constructed and tested with selected feedstock. Pyrolysis gas was recovered and burnt in fire chamber to provide additional heat for process. Four best substrates from urban biowaste were selected for carbonization during testing of slow pyrolysis system. Input feedstock and output char were characterized by using proximate analysis method to determine Fixed Carbon, Volatile Matter and Ash Content. Calorific values of material were determined by bomb calorimeter and by empirical formula for estimating High heating Value (HHV) from proximate analysis. It was found that wood waste char has greater HHV of 29 MJ/kg. Char yield and fixed carbon were calculated from full carbonized batch. Maximum char yield of system was 36% from package grass. Energy balance in terms of chemical energy and kiln performance were determined. The emerged major challenge was determining energy loss in exhaust gas and loss due to CO content in exhaust gas. Future work should be done to improve the performance of system and full account the energy balance of the system to determine performance of the system.