Wastes

Waste refers to unwanted materials or residues resulting from human activity that are discarded, recycled, or recovered. They can be solids, liquids, sludges, or gases and originate from households, industry, agriculture, healthcare, construction, and mining. Management decisions depend on the material’s characteristics and potential risks to health and the environment.

Classification commonly distinguishes by source and hazard. Municipal solid waste includes everyday household and commercial refuse. Industrial solid waste comes from manufacturing and mining activities. Hazardous wastes exhibit characteristics such as ignitability, corrosivity, reactivity, or toxicity. Non-hazardous wastes include many kinds of non-toxic materials, though they still require appropriate handling. Special wastes cover medical, electronic, and construction and demolition debris, which may require separate management due to their specific risks.

Environmental and health impacts arise when wastes are improperly stored, treated, or disposed. Contamination of soil, groundwater, and surface water can occur through leaks and leachate; air emissions can affect air quality; and the decomposition of organic waste releases methane, a potent greenhouse gas. Wastes also contribute to resource depletion if materials are discarded instead of recovered.

Management approaches follow a waste hierarchy that emphasizes prevention and minimization first, then reuse, recycling, and energy recovery, with disposal as a last resort. Techniques include composting, material and mechanical recycling, energy recovery through waste-to-energy processes, and engineered landfilling. Hazardous wastes require specialized treatment and containment to prevent releases.

Regulatory and policy frameworks guide waste management, including producer responsibility schemes, pollution prevention measures, and international agreements on hazardous waste. Responses to waste generation vary by region, but the goal is to reduce generation, improve separation and collection, and maximize recovery while protecting health and the environment.