Proper and effective utilization of biomass wastes, couple with efficient conversion into useful energy have made the study of biomass wastes and finding solution to ash deposition during thermal conversion crucial. In this work, Alum Sludge (AS) was used to regulate ash deposition in Palm Oil Decanter cake (PODC). AS and PODC were characterized using Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM-EDS), Thermogravimetric analysis (TGA), Advance X-ray diffractometer (XRD) while Ash fusion test (AFT) was used to determine the ash fusion temperature. SEM-EDS revealed the presence of Aluminum (13.50 wt), Potassium (1.46 wt), Iron (2.43 wt) and Silicon (14.95 wt) in AS while Potassium (1.19 wt), Silicon (1.41 wt), Calcium (2.16 wt) and Chlorine (0.67 wt) in PODC. TGA revealed that fixed carbon, volatile matter and ash content in AS are 8.94 wt, 3.60 wt and 86.72 wt while PODC are 7.13 wt, 51.84 wt and 38.15 respectively. The total weight loss of AS and PODC was 13.29 and 61.86 respectively. XRD revealed the presence of Kaolinite and Quartz/ Zeolite in AS while Whewellite, Quartz, Potassium Chloride in PODC. AFT revealed 1215� and above 1400� as the sintering temperature for PODC and AS respectively. At 50 and above of AS addition, low slagging tendency of PODC was attained. This study provides a new insight on how AS and PODC wastes can be properly managed and utilized in clean energy production. © 2023, Association of American Publishers. All rights reserved.