Municipal Solid Waste (MSW) is the collective term for the everyday discarded material generated by the public. Commonly known as trash or garbage, MSW represents a specific, non-hazardous waste stream managed by local governments. MSW excludes regulated streams such as industrial process wastes, agricultural refuse, medical waste, or radioactive material. It is composed of the solid items that people and businesses dispose of daily, forming the central focus of municipal collection and disposal programs.
The Materials Making Up MSW
The physical composition of MSW is complex and can vary significantly based on regional factors, economic conditions, and the time of year. However, the waste stream is consistently dominated by a few major material categories that collectively represent the largest portion by weight. This composition is a direct reflection of modern consumer habits and consumption patterns.
Organic materials, specifically food scraps and yard trimmings, often make up the largest share of the waste stream, sometimes accounting for around a third of the total mass. Food waste decomposes in landfills to produce methane gas. Paper and paperboard products, including newspapers, magazines, and packaging boxes, form another highly prevalent category.
Plastics, ranging from packaging materials and bottles to durable goods, constitute a significant and growing fraction of the total MSW generated. Plastics alone can account for over 10% of the discarded mass. The remaining materials include glass bottles and jars, metals such as aluminum cans and steel containers, wood, textiles, and miscellaneous items. Categories like paper, food waste, and plastic consistently represent the majority of the total volume.
Sources of Waste Generation
MSW originates from three primary sectors within a community. The residential sector, encompassing homes and apartment buildings, is typically the largest contributor, often generating over half of the total volume. This includes household food scraps, packaging, old furniture, and yard waste.
Commercial establishments, such as retail stores, restaurants, and office buildings, account for the second major source. Their waste profile is characterized by significant amounts of packaging materials, paper, and food waste. The institutional sector generates MSW from public and private facilities like schools, universities, hospitals, and government offices. General office and cafeteria waste from these institutions falls under the definition of MSW.
Common Management and Disposal Methods
Once MSW is collected, it enters a management system that employs a hierarchy of methods. The most common disposal method is placement in a Municipal Solid Waste Landfill (MSWLF), which accounts for roughly half of the total waste stream. Modern landfills are highly engineered facilities designed to contain waste and minimize environmental impact.
These sanitary landfills utilize composite liner systems, often including a flexible geomembrane layer over compacted clay, installed to protect groundwater. A leachate collection and removal system is placed above the liner to gather the liquid that filters through the waste for treatment. The waste is compacted and covered daily to control odors, pests, and litter.
A substantial portion of MSW is managed through resource recovery methods, primarily recycling and composting, which diverts materials away from landfills. Recovery programs for paper, glass, metals, and plastics allow these materials to be reprocessed into new products, conserving raw materials and energy. Organic waste, such as yard trimmings and food scraps, is often diverted for composting, converting it into a soil amendment.
The third major management method is combustion, often referred to as waste-to-energy (WTE). WTE facilities burn MSW under controlled conditions to generate steam and electricity, reducing the volume of the original waste by 85% to 95%. While this process recovers energy, the resulting ash residue still requires final disposal, typically in a landfill.