Baobab fruit waste pellets and optimization of selected pelletization parameters

Baobab ( Adansonia digitata ) is a desert plant with very little water content in the produced fruit wastes, making their management a challenge. The aim of this study is to prepare single and co-pelletized baobab fruit waste fuel pellets, analyze their physio-chemical characteristics and study the effect of moisture content and mix ratios on pellet's bulk density, Higher Heating Value (HHV), and Pellet Durability Index (PDI). The effect of moisture content is investigated by varying the biomass moisture levels while fruit shells (FS) and press cake (PC) are mixed in the different ratios by weight. Pellets are produced using a manually-made hydraulic press pelleting machine. Proximate and ultimate analysis are used to study the physio-chemical characteristics of the pellets. Response Surface Methodology (RSM) is employed to study the combined effect of moisture content and mix ratios on pellet's bulk density, HHV and PDI. Results show that, the moisture content, volatile matter, and fixed carbon of FS, PC and their co-pellets ranged between 7.94 % and 9.89 %, 64.94 %–73.20 %, and 17.08 %–21.61 %, respectively. The ultimate analysis show that co-pelletized pellets have a higher carbon and hydrogen contents with significantly low sulfur and nitrogen contents. Increase in moisture levels has a negative impact on bulk density, HHV, and PDI of the pellets. RSM optimization showed that the optimum pellet's bulk density, HHV, and PDI were achieved as 736.70 kg/m 3 , 21.03 MJ/kg, and 99.96 %, respectively. This work reveals a great potential in baobab fruit wastes value chain addition by harnessing these waste materials for clean energy generation. • Pellets physio-chemical properties are studied via proximate and ultimate analysis. • Effect of moisture content and mix ratios was investigated. • Elevation in moisture levels impact negatively on bulk density, HHV, and PDI. • Co-pelletization of FS with PC improved the bulk density, HHV, and PDI. • RSM shows bulk density increases with increase in PC at a moisture content below 11 %.