Incineration

Incineration is a waste treatment process that reduces the volume and mass of waste by combustion, converting it into ash, flue gases, and usable heat. It is applied to municipal solid waste, healthcare waste, and certain hazardous wastes, and is often paired with energy recovery.

In modern plants waste is fed into a combustion chamber—grate-fired or rotary kiln—where the material burns at high temperature. The primary chamber operates roughly 800-900 C; the secondary chamber maintains about 850-1100 C to ensure complete combustion and destruction of organic contaminants. The resulting hot flue gas passes through heat exchangers to generate steam or electricity.

Flue gas cleanup is essential to control air pollutants. Multistage systems remove acid gases, particulates, mercury and other heavy metals, and dioxins/furans. Techniques include scrubbers, fabric filters or electrostatic precipitators, activated carbon injection, and selective catalytic reduction. Emissions are regulated by national or regional standards.

Residues include bottom ash and fly ash; bottom ash can be reused as construction material in some cases after stabilization, while fly ash is typically treated as hazardous waste and disposed of in specialized landfills. Energy recovery and residue handling are subject to local permits.

Advantages of incineration include substantial reduction of waste volume and potential energy recovery, while disadvantages include high capital and operating costs, complex emissions controls, and public health concerns when poorly managed. It is commonly used alongside recycling and composting, for the non-recyclable fraction and for certain waste streams such as medical waste.

The practice began in the 19th century and expanded in the 20th century, with modern designs focusing on environmental controls. Regulation varies by country, but most jurisdictions require permits, performance standards for emissions and ash, and reporting of energy recovery.