**2. Industrial wastes and their types**

Industrial wastes are unwanted and residual materials produced by industrial activities and may include any product discarded as useless during such manufacturing operations as metal deformation, metal casting, sheet metal forming, polymer processing, machining, finishing, assembly, foundry, steam generation, and coal-fire electrification, construction works, textile manufacture, pulp and paper mills, and mining operations to mention a few [4]. These wastes are basically generated in large quantities when compared to municipal wastes and mostly at every stage in the manufacture of products, which turns raw materials into finished goods that are sold or distributed [4]. Manufacturing processes commonly generate all forms of waste including gaseous, liquid, and solid wastes [4].

Industrial waste products have particularly dangerous properties such as toxicity, ignitability, corrosivity, or reactivity [5], can negatively impact human health and the environment [6] or pollute nearby soil, adjacent to water bodies or contaminate groundwater, lakes, streams, rivers, and coastal waters [3]. At a typical landfill site, industrial waste is often mixed with municipal waste, which makes accurate assessments of industrial waste produced difficult [2]. In the United States, for instance, an estimation gave more than 7.5 billion tons of industrial waste produced annually, as of 2017 [2]. Problems associated with generation of industrial waste have forced most countries and municipalities to enact legislation to deal with the situation [2]. While strictness and compliance with industrial waste pollution legislation may vary from place to place, enforcement of such legislation is often an issue [2]. The different types of industrial waste generated according to the industrial sector are shown in **Table 1** below.
