A method of injecting steam into a landfill is provided. The steam enhances methane gas production in the landfill during the anaerobic phase, accelerates decomposition/biodegradation of the organic component of the trash prism during both the aerobic and anaerobic phases, and increases the rate of settlement of the landfill. A method of introducing a gaseous anaerobic fertilizer into the landfill is also provided. The fertilizer accelerates the decomposition/biodegradation of the organic component of the trash prism. A method of reducing the volume of a plastic component of the trash prism is provided, wherein the temperature and pressure of injected steam are raised to a level sufficient to melt plastic. Finally, a method of reducing the volume of a quantity of refuse prior to placing the refuse in a landfill is provided, wherein the refuse is heated to melt a plastic component of the refuse.