Waste heat in industrial processes refers to thermal energy that is generated during operations but not used for the primary purpose of production and is instead released into the environment. This heat commonly escapes through exhaust gases, cooling systems, hot surfaces, or discharged liquids. Processes such as furnaces, boilers, kilns, dryers, compressors, and thermal oxidizers all produce significant amounts of excess heat that often goes unused.

Waste heat can exist at different temperature levels. High-grade waste heat comes from exhaust streams and combustion processes, while medium- and low-grade waste heat may come from cooling water, lubricating oils, or equipment casings. Even warm air exhausted from ventilation systems can be considered waste heat if it carries recoverable energy.

Rather than allowing this energy to dissipate, waste heat recovery systems are intend to preserve and reuse it for practical applications such as preheating combustion air, generating steam, heating process water, or supporting space heating. By identifying where heat is lost and matching it with a usable demand, facilities can turn waste heat into a valuable energy resource, improving efficiency and reducing overall energy consumption across industrial operations.