The population growth and the new consumption models contribute significantly to a greater generation of waste, which is generally incorrectly managed because a large percentage of the waste generated is sent to landfills. Waste-to-energy (WtE) plants play a fundamental role in managing and treating municipal waste because they reduce the amount of waste sent to landfills and reduce dependence on imported fossil fuels. WtE is a key issue of a waste management system. From the perspective of the energy system, WtE will contribute to the development of a low-carbon society.
Waste management has become an increasingly crucial issue because of the large quantities of municipal solid waste and its multiple negative impacts on the environment and society if inappropriately disposed of. Meanwhile, sustainable development requires an adequate supply of clean and affordable renewable energy sources. Waste-to-energy (WTE) contributes significantly to the circular economy by generating energy and promoting sustainable development.
Waste-to-energy plants burn municipal solid waste (MSW), often called garbage or trash, to produce steam in a boiler, and the steam is used to power an electric generator turbine. The most common waste-to-energy system in the United States is the mass-burn system. In this system, unprocessed MSW is burned in a large incinerator with a boiler and a generator to produce electricity (see illustration below). A less common type of system processes MSW to remove non-combustible materials to produce refuse-derived fuel (RDF).
The process of generating electricity in a mass-burn waste-to-energy plant has seven stages:
1. Waste is dumped from garbage trucks into a large pit.
2. A giant claw on a crane grabs waste and dumps it in a combustion chamber.
3. The waste (fuel) is burned, releasing heat.
4. The heat turns water into steam in a boiler.
5. The high-pressure steam turns the blades of a turbine generator to produce electricity.
6. An air-pollution control system removes pollutants from the combustion gas before it is released through a smoke stack.
7. Ash is collected from the boiler and the air pollution control system.