Municipal solid waste (MSW), often called trash or garbage in the United States and rubbish in Britain, is a type of waste made up of everyday items that people throw away. The word "garbage" can sometimes mean food waste, such as when using a garbage disposal. In some cases, food waste is collected separately from other types of waste. In the European Union, this type of waste is called "mixed municipal waste" and is given the code 20 03 01 in the European Waste Catalog. Even though the waste may come from places not managed by a local government, the term "municipal" comes from the traditional role of local governments in collecting and managing this waste.

Composition

The types of waste in cities and towns can change a lot. This change happens over time. In cities with strong recycling programs, most waste includes hard-to-handle materials like plastic film and packaging that cannot be recycled. At the start of the 20th century, most household waste in the UK (53%) was coal ash from open fires. In areas with less recycling, waste mostly includes food scraps, garden waste, plastic containers, packaging, and other solid waste from homes, businesses, schools, and factories. Most definitions of municipal solid waste do not include industrial waste, farm waste, medical waste, radioactive waste, or sewage sludge. Waste collection is handled by the local government in a specific area. Residual waste refers to leftover waste from homes that was not sorted or sent for processing. Waste can be grouped in different ways. A typical classification includes:

• Biodegradable waste: food scraps, kitchen waste, garden waste, and paper (most paper can be recycled, but some plant materials may not be suitable for composting)
• Recyclable materials: paper, cardboard, glass, bottles, jars, tin cans, aluminum cans, aluminum foil, metals, certain plastics, clothing, tires, and batteries
• Inert waste: construction and demolition waste, dirt, rocks, and debris
• Electrical and electronic waste (WEEE): items like televisions, computers, washing machines, light bulbs, mobile phones, and alarm clocks
• Composite waste: items like old clothing, Tetra Pak cartons, and plastic items such as toys and garden furniture
• Hazardous waste: materials like paints, chemicals, tires, batteries, light bulbs, electrical appliances, fluorescent lamps, aerosol cans, and fertilizers
• Toxic waste: substances like pesticides, herbicides, and fungicides
• Biomedical waste: expired medicines and similar materials

For example, typical municipal solid waste in China includes 55.9% food waste, 8.5% paper, 11.2% plastic, 3.2% textiles, 2.9% wood waste, 0.8% rubber, and 18.4% non-combustible materials.

Components of solid waste management

The municipal solid waste management system includes four main parts: recycling, composting, disposal, and waste-to-energy through incineration. No single method works for all types of waste, so the Environmental Protection Agency (EPA), a U.S. federal government agency, created a ranking system to guide waste management. This system, called the waste management hierarchy, lists four levels from most preferred to least preferred based on how environmentally safe they are: reducing waste at the source and reusing items; recycling or composting; recovering energy from waste; and treating or disposing of waste.

The collection process includes gathering solid waste and recyclable materials and then transporting them to a location where the collection vehicle is emptied. This location may be a processing facility, a transfer station, or a landfill.

Handling and separating waste involves managing waste until it is placed in containers for collection. This includes moving filled containers to the collection point. Separating different waste types is an important step in managing waste at the source.

Waste that has been separated at the source is often recovered using methods like curbside collection, drop-off centers, or buy-back centers. Separating and processing waste that has been sorted at the source or waste that is mixed together usually happens at facilities such as materials recovery centers, transfer stations, combustion plants, or treatment plants.

This process has two main steps. First, waste is moved from a smaller collection vehicle to a larger transport vehicle. Then, the waste is transported over long distances to a processing or disposal site.

Today, landfills or land spreading are the final destination for most solid waste, whether it is residential waste sent directly to a landfill, leftover materials from recycling centers, waste from burning solid waste, compost, or other materials from processing facilities. A modern sanitary landfill is not a simple dump; it is a carefully designed facility that safely stores solid waste without harming public health or the environment, such as by preventing insect problems or groundwater contamination.

In recent years, organizations like Freegle or The Freecycle Network have grown in popularity because they help people reuse unwanted items online. These groups create a global list of items that would otherwise be thrown away, allowing individuals and nonprofits to reuse or recycle them. This service helps reduce landfill pollution and supports the reuse of items.

Landfills are created by dumping waste into a designated area, often a hole or a slope. After waste is placed, large machines compress it. When the area is full, it is covered with a plastic sheet and several feet of dirt. This method is common in the United States because of the low cost and availability of unused land. Landfills are regulated by the EPA, which enforces rules like requiring liners and groundwater monitoring to prevent pollution. Landfills can pollute groundwater, but signs of pollution are often hidden by disposal companies. Landfills are usually surrounded by walls or fences, and chemicals are sprayed to mask the smell of decaying waste.

Municipal solid waste produces large amounts of methane, a powerful greenhouse gas. However, nearly 90% of these methane emissions could be prevented using current technology.

Municipal solid waste can be used to create energy because of the lipid content in it. Many materials from solid waste can be turned into clean energy if the lipid content is accessed and used. New technologies have made processing solid waste for energy cleaner and more cost-effective. These include capturing landfill gas, burning waste, pyrolysis, gasification, and plasma arc gasification.

Older waste incineration plants released many pollutants, but recent rules and new technologies have greatly reduced this issue. EPA regulations from 1995 and 2000 under the Clean Air Act have cut dioxin emissions from waste-to-energy facilities by over 99% compared to 1990 levels, and mercury emissions have dropped by more than 90%. In 2003, the EPA stated that waste-to-energy is a power source "with less environmental impact than almost any other source of electricity."