Methods for filling a container with hazardous waste are disclosed. One method includes moving the container to a position where a filling head adds solid hazardous waste to the container, coupling a lid to the container to close the container while the container is at the position, and moving the closed container away from the position. Another method includes aerating dry cementitious material in the container with a mixer, adding hazardous waste to the container, mixing the cementitious material and the hazardous waste with the mixer, and controlling the speed of the mixer.