Environmental regulations are getting more restricted related to landfilling of biodegradable waste. The solution to these problems is using the biodegradable portion of sludge waste for agricultural or thermal utilization. This paper is based on the physico-chemical analysis of different proportions of sludge with coal and rice husk for co-combustion to optimize the parameters like sulfur, ash, and gross heating value (GHV). A significant increase in GHV of secondary sludge with different combinations of coal and rice husk was observed as compared to primary sludge combinations representing 13.55-21.80 Mj/kg and 11.52-19.12 Mj/kg, respectively. The combination RSSC-1 (50% sludge and 50% coal) is highly significant with p < 0.01 and can be utilized as fuel because of the high GHV and low sulfur content. This study concludes that co-combustion of sludge in an eco-friendly manner, using modified thermal methods, may turn into a valuable fuel like traditional biomass.