Experimental investigation on drying options of potential urban biowaste for char productiona case study of Dar es Salaam

This dissertation report presents the experimental investigation on drying options of potential urban biowaste for char production in Dar es Salaam. The focus was to identify and assess their pre-treatment needs for char production. Preliminary survey was conducted to identify potential biowastes which were further assessed and ranked for their suitability for char production, using smart criteria. The criteria were categorized into i) availability and accessibility aspects, and ii) physical-chemical suitability criteria. Data for the former criteria group were obtained from surveys and observations, whereas the data for the later on was generated through laboratory experiments. The result from Multi Criteria Decision Analysis revealed that sawdust, coconut husks, packaging leaves and cardboards can viably be converted to char. Furthermore, a prototype drying unit was developed and tested in order to investigate simple drying effectiveness for wet biowastes. The drying tests revealed that, exhaust fan increase the drying efficiency as compared to natural draft. The tests also showed that the dryer operating in a hybrid mode (charcoal stove and solar) met the requirement of drying the biowastes in one day as compared operating the dryer with solar only.