An incinerator includes a furnace, a heat-insulating shield, an air conduit, an air blower, and a dryer. The heat-insulating shield has a top wall, a vertically extending peripheral wall that extends downwardly from the top wall and that surrounds and that is spaced apart from the furnace by a gap, and an open bottom end. The peripheral wall of the heat-insulating shield has an air outlet that is disposed adjacent to the top wall and that is in fluid communication with the gap. Atmospheric air is introduced via the open bottom end through the gap and the air conduit and into the dryer. A feed motor is used to deliver solid waste into the furnace. A control unit controls rotating speed of the feed motor based on temperature in the dryer so as to adjust the temperature in the dryer.