Combustion characteristics for seasonal sewage sludges have been studied for thi. understanding of stable operating conditions, the requirement of auxiliary fuel and flue gas conditions in fluidized bed (O.5m ID x 3.35m H and O.lm ID x O.85m H, respectively). The combustor was stable at the conditions of excess airlratio 1.5-1.7 and 7-8% 02 in flue gas. The concentration of NOx in flue gas was stable under 150ppm and the concentration of SO • of the digested sludge was higher than that of the nondigested sludge because the sulfur content of the sludle was higher in itself. The auxiliary I fuel was required over kerosene 100 I to incinerate the sewage sludge with 80% water content. Therefore, it was recommended to utilize the lower cost fuel such as refuse derived fuel, which could tre the fuel cost as It was made from sohd waste.