Waste

Waste is materials or substances that are discarded after use or deemed of no further value. It includes solids, liquids, and gases, with municipal solid waste drawing particular public attention. Waste is typically defined by its potential for recovery, recycling, or safe disposal rather than by its source.

Common categories include municipal solid waste from households and businesses; industrial waste from manufacturing and power generation; construction and demolition waste; hazardous waste such as chemicals and solvents; medical waste; electronic waste; and agricultural or wastewater by-products.

Global waste generation has risen with population growth, urbanization, and rising consumption. Economic development, packaging, and short product lifespans increase waste streams. Effective management depends on infrastructure, regulation, and public participation.

Waste management follows a hierarchy: reduce at the source, reuse, recycle, and recover energy where feasible, with disposal as a last resort. Techniques include sorting and collection, composting and anaerobic digestion, material recovery facilities, incineration with energy capture, and landfilling. Hazardous and medical wastes require special handling and containment.

Environmental and health impacts arise from pollution, methane emissions from landfills, leachate, and toxic exposures. In many regions informal recycling sectors perform collection and sorting but face occupational hazards and variable safety. Electronic waste poses particular risks from heavy metals and persistent pollutants.

Policy approaches include extended producer responsibility, landfill bans, recycling targets, and investments in sorting and treatment infrastructure. The concept of a circular economy emphasizes keeping materials in use and reducing waste generation, with data-driven metrics guiding progress.