Combustion

Combustion is the controlled burning of substances in an enclosed area, as a means of treating and disposing of hazardous waste.

There are two categories of combustion units for solid and liquid hazardous wastes:

• Incinerators - used primarily for waste destruction. 
• Boilers and Industrial Furnaces (BIFs) - used primarily for energy and material recovery. 

The regulations affecting hazardous waste processed in BIFs include the general TSDF facility standards, standards for the direct transfer of waste from a transportation vehicle to a unit, and regulation of residues. BIFs are required to comply with strict air emissions standards to ensure adequate protection of human health and the environment.

Incinerators

Incinerators are used to burn hazardous waste primarily for waste destruction/treatment purposes; however, some energy or material recovery can occur. When performed properly, incineration destroys the toxic organic constituents in hazardous waste and reduces the volume of the waste. Since metals will not combust, incineration is not an effective method for treating metal-bearing hazardous wastes. Resource Conservation and Recovery Act (RCRA) regulations governing incinerators can be found at TN Rule Chapter 0400-12-01-.06(15) - Incinerators.

Boilers and Industrial Furnaces (BIFs)

BIFs are typically used to burn hazardous waste for the significant energy and material recovery potential, with waste treatment being a secondary benefit. Boilers typically combust waste for energy recovery, while industrial furnaces burn waste for both energy and material recovery.

A boiler is defined as an enclosed device that uses controlled flame combustion to recover and export energy in the form of steam, heated fluid, or heated gases. An industrial furnace is a unit that is an integral part of a manufacturing process and uses thermal treatment to recover materials or energy. 

RCRA regulations governing boilers and industrial furnaces can be found at TN Rule Chapter 0400-12-01-.09(8) - Hazardous Waste Burned in Boilers and Industrial Furnaces.