Furnace oil is atomized with air in the burner and fired, which produces hot flue gases that pass into the boiler tubes to generate steam. The furnace oil fired boilers contribute to greenhouse gas emissions and secondary pollutants. Briquette as a fuel to address these problems is a better alternative. This book comprises of a case study carried out to evaluate and compare the performance and emissions of furnace oil and briquette boilers. This work deals with the fuel system conversion of an existing fire tube boiler running with furnace oil to saw dust briquettes. Further the boiler capacity is increased by mounting a water wall assembly. The efficiency of this combined fire tube and water tube boiler is determined by using indirect method approach also called as heat-loss method as per Indian Standard for boiler efficiency testing IS - 8753 as well as by American Society of Mechanical Engineers, Power Test Code ASME PTC 4.1. The emission measurements are carried out by portable flue gas analyzer.