Co-pelletization of Microalgae-Sewage Sludge Blend with Sub-bituminous Coal as Solid Fuel Feedstock

Microalgae have been appeared as excellent source of bioenergy recently in Brunei Darussalam due to the favorable growth conditions, while sewage sludge emerged as major threat to the environment. Therefore, the challenge of sewage sludge management and microalgae utilization has spurred the demand of developing an innovative approach to utilize these sources for commercial applications. Hence, the main objective of this study was to characterize the bioenergy properties of microalgae, sewage sludge, and different blending ratios of microalgae-sewage sludge incorporated with sub-bituminous coal. Among three different blended samples, sample mixture 1 (SM-1) combined with 25% microalgae, 25% sewage sludge, and 50% coal presented the highest calorific value of 16.57 MJ/kg and lowest ash content of 45.61%. Along with this, SM-1 also manifested the highest values for pellet density (1.23 g/cm3) and energy density (20.41 GJ/m3) that can be referred as the most favorable values among all co-pelletized samples for transportation and logistics. Besides the characterization of raw samples, this study also emphasized on elemental analysis of ash content to determine the possibility of fouling and slugging. Ash analysis of all blends represented the major inorganic components aluminum (Al) and silicon (Si). Thermogravimetric analysis of all samples demonstrated the different phases of pyrolysis and combustion within 50 to 900 °C at heating rate of 10 °C/min. It can be concluded that this study recommended SM-1 as a potential feedstock for solid fuel purpose.