Solid waste is a heterogeneous mixture of discarded materials produced from human activities, and it has become a major global environmental concern due to its impact on ecosystems, human health, and climate. Environmental biotechnology plays a crucial role in managing solid waste by providing sustainable strategies for treatment, recycling, and degradation of harmful compounds. To understand how solid waste is managed, it is necessary to examine its sources, classification based on hazardous potential, content, and origin, and then explore the biological mechanisms that degrade xenobiotics, which are synthetic or natural compounds not commonly found in nature and often resistant to degradation. The sources of solid waste are diverse, originating from households, industries, agriculture, healthcare, and institutions. Municipal solid waste is generated from households and commercial establishments and typically consists of food residues, plastics, paper, textiles, glass, and metals. Industrial waste arises from manufacturing and processing industries and may include chemical residues, plastics, heavy metals, and other toxic materials. Agricultural waste comprises crop residues, animal manure, pesticides, and fertilizers. Biomedical waste originates from hospitals and laboratories, consisting of infectious materials, sharps, and pharmaceutical residues. Additionally, mining and construction activities generate debris, soil, stones, and chemically contaminated materials. The rapid urbanization and industrialization of modern society have led to an exponential increase in both the volume and complexity of waste. Classification of solid waste is essential to determine appropriate treatment methods and ensure safe disposal. Based on hazardous potential, solid waste can be categorized into hazardous and non-hazardous types. Hazardous waste poses a threat to human health and the environment due to its toxicity, flammability, corrosivity, or reactivity. Examples include pesticide containers, solvents, heavy metal residues, radioactive substances, and certain industrial by-products. Non-hazardous waste, on the other hand, includes biodegradable municipal waste such as food scraps, yard trimmings, and paper, which do not pose immediate danger but still require proper management to prevent environmental pollution. Based on content, solid waste is classified into biodegradable and non-biodegradable categories. Biodegradable waste includes organic matter such as food