AbstractThe aim of this research was to study the physical and chemical properties of fly ashes from combustion process and carbon residue from gasification process whilst comparing the results between these two types of solid residues, as well as against literature values. Ashes from the combustion process and carbon residue from gasification process are formed in different conditions, and it can be assumed that they will be best suited to contrasting utilization applications. The most notable differences between these types of solid residues were that the carbon content and loss-on-ignition value was higher for gasification carbon residue, and the liming capacity was higher for combustion ashes. The calculated liming capacity for combustion ashes and the fact that these ashes were strongly alkaline, together with high nutrient concentrations, indicate that combustion ashes can provide a liming effect. As a result, these ashes could potentially be utilized as a soil conditioning agent to substitute for commercial lime. The carbon content in gasification carbon residue was high which indicates, together with high porosity, that carbon residue would be an ideal sorbent and it could also be used as a fuel.