Solid waste refers to the unwanted and discarded material generated from various human activities, which needs to be managed properly to avoid environmental and health problems. The sources of solid waste are diverse and include households, industries, institutions, agriculture, construction, and commercial establishments. Based on their hazardous potential, content, and origin, solid wastes are broadly classified to aid in effective management and treatment. The study of solid waste management has become an important aspect of environmental biotechnology, as it offers biological solutions for minimizing and recycling wastes. Moreover, the presence of xenobiotics—synthetic compounds that are foreign to natural systems—requires special attention, since their persistence and toxicity pose significant environmental challenges. Biodegradation of xenobiotics, carried out by microorganisms through various mechanisms, is crucial in reducing their harmful impact. The sources of solid waste can be divided into several categories. Municipal solid waste arises from households, offices, schools, restaurants, and public places. This type generally includes paper, plastics, metals, food scraps, yard trimmings, glass, and textiles. Industrial solid waste is generated from manufacturing and processing industries, and includes materials such as chemicals, fly ash, packaging waste, and slag. Agricultural solid waste consists of crop residues, manure, and pesticide containers, which are often generated in large volumes. Biomedical or hospital waste originates from healthcare facilities and includes syringes, bandages, pharmaceuticals, pathological waste, and discarded equipment. Construction and demolition waste is produced by building activities and consists of concrete, bricks, wood, and other materials. Electronic waste, a modern category, includes discarded electronic appliances such as computers, phones, and televisions, which contain metals and hazardous substances.