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SOLID-WASTE CHARACTERISTICS
The sources of solid waste include residential, commercial, institutional, and industrial activities. Certain types of wastes that cause immediate danger to exposed individuals or environments are classified as hazardous. Hazardous-waste management deals with the collection, treatment, and disposal of waste material that, when improperly handled, can cause substantial harm to human health and safety or to the environment. Hazardous wastes can take the form of solids, liquids, sludges, or contained gases, and they are generated primarily by chemical production, manufacturing, and other industrial activities. They may cause damage during inadequate storage, transportation, treatment, or disposal operations. Improper hazardous-waste storage or disposal frequently contaminates surface and groundwater supplies. All non-hazardous solid waste from a community that requires collection and transport to a processing or disposal site is called refuse or municipal solid waste. Refuse includes garbage and rubbish. Garbage is mostly decomposable food wastes, rubbish is mostly dry material such as glass, paper, cloth, or wood. Garbage is highly putrescible or decomposable, while rubbish is not. Trash is rubbish that includes bulky items such as old refrigerators, couches, or large tree stumps. Trash requires special collection and handling.
Solid-waste characteristics vary considerably among communities and nations. American refuse is usually lighter, for example, than European or Japanese refuse. In the United States paper and paperboard products make up close to 40 percent of the total weight of municipal solid waste; food waste accounts for less than 10 percent. The rest is a mixture of yard trimmings, wood, glass, metal, plastic, leather, cloth, and other miscellaneous materials. In a loose or uncompacted state, municipal solid waste of this type weighs approximately 200 pounds per cubic yard (120 kilograms per cubic metre). These figures vary with geographic location, economic conditions, season of the year, and many other factors.
Waste characteristics from each community must be studied carefully before any treatment or disposal facility is designed and built. Rates of solid-waste generation also vary widely. In the United States, for example, municipal refuse is generated at an average rate of approximately 4.4 pounds (2 kilograms) per person per day. Japan generates roughly half this amount, yet in Canada the rate is almost seven pounds per person per day. In some developing countries (e.g. India) the average rate can be lower than one pound per person per day. These data include refuse from commercial, institutional, and industrial sources, as well as from residential sources.
The actual rates of refuse generation must be carefully determined when a community plans a solid-waste management project. Most communities require household refuse to be stored in durable, easily cleaned containers with tight-fitting covers in order to minimize rodent or insect infestation and offensive odours. Galvanized metal or plastic containers of about 30-gallon (115 litres) capacity are commonly used, although some communities employ larger containers that can be lifted mechanically and emptied into collection trucks. Plastic bags are frequently used as liners or as disposable containers for curbside collection. Where large quantities of refuse are generated - such as at shopping centres, hotels, or apartment buildings - dumpsters may be used for temporary storage until the waste is collected. Some office and commercial buildings use on-site compactors to reduce the waste volume.
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