When garbage goes to a waste-to-energy plants, the truck depositing it is weighed, then enters an enclosed tipping area where the waste is unloaded into a concrete storage pit. Cranes move and mix the waste, and remove bulky processable items that are too large for the furnace. (Those are removed for landfilling.)
Cranes then feed the waste into furnace hoppers, where it travels along moving metal grates. The furnace is so hot (a minimum of 1800 degrees F.) that complete combustion of materials takes place.
As the process continues, hot gases are carried up from the grate area through boiler tubes where steam is produced from heat absorption. The gases pass from the boiler to a scrubber where they are mixed with a water mist containing lime. The gases are cooled and a chemical reaction neutralizes any acids and produces particles that can be collected.
The materials then pass through a baghouse, which works like a large vacuum cleaner, collecting particles produced in the boiler and scrubber. The cooled and cleaned gases are vented through a stack flue that is 200 feet above the ground.
The entire process is guided and monitored by operators in a central control room. All processing activities take place indoors to control dust odors, and prevent rain water from coming into contact with waste or ash. Metals in the ash are removed and recycled, and the remaining ash is landfilled in areas adjacent to the plants, called monofills. The monfills have multiple liners to prevent groundwater contamination. The water retained by the monofill liner is used in the plants, or sent to a sewage treatement plant for disposal. Waste that cannot be recycled or processed at the plants is landfilled.