Solid wastes include domestic refuse and other discarded solid materials, such as those from commercial, industrial, and agricultural operations.
Domestic refuse includes paper, cardboard, metals, glass, food matter, ashes, plastics, wood, and other substances discarded from homes. It also includes old furniture, household appliances, and other items. Increasing amounts of paper, cardboard, plastics, glass, and other types of packaging are concomitants of improved standards of living. At the same time, the increasing use of gas, oil, and electricity for heating and cooking has resulted in a decline in the ash content of solid wastes. Thus, the proportion of paper and paper products in domestic refuse has already reached more than 50% in some countries, and this trend will continue.
Commercial refuse includes the wastes discarded by markets, shops, restaurants, offices, and similar businesses. Such refuse is growing in importance not only as a result of increasing business activity, but also because there are few opportunities to deal with it on-site.
Industrial refuse comprises a very wide variety of wastes ranging from comparatively inert materials such as calcium carbonate to highly toxic and explosive compounds. Other examples are trimmings and scrap from manufacture, sludges and slag from industrial processes, and wastes from the food processing industry. Wastes produced in large quantities by mining and some other operations are usually treated by the respective industries themselves. The natural growth and diversity of industry generally, together with rapid technological developments, have resulted in substantial increases not only in the volume of industrial wastes, but also in their complexity.
Agricultural wastes include wastes arising from the production and processing of food and other crops and from the raising and slaughtering of livestock. In many areas the practice of agriculture near urban areas is resulting in the need to consider this type of waste, which is growing in volume, as part of the general urban waste-disposal problem.
General community waste includes demolition and construction debris, street refuse, discarded motor vehicles, and refuse arising from community services such as hospitals, abattoirs, transport systems, parks, canals and harbours. Special handling is required for potentially dangerous wastes such as those from hospitals, international ports and airports, and firms using radioactive materials. As in the other classifications, the volume of material arising from these sources is increasing.
It is safe to say that everywhere the amounts of solid wastes produced each day per person are increasing as a result of social, economic and technological changes. In addition, better quantitative data are now becoming available as a result of improved surveys. For example, the initiation about 20 years ago of scientific surveys in a few cities, encompassing all types of solid wastes, revealed a surprising discrepancy between earlier 'guess estimates' and actual production of wastes. Prior to about 1945, the production of solid wastes was assumed to be 350 to 400 kg per capita per year. Improved standards of living, the building boom, the growth of packaging of consumer goods, and vast increases in the use of paper, paper products, and synthetics have all contributed to an increase in the amount of urban wastes, so that the present average in the industrialized countries is probably at least 700 kg per capita per year. The annual increase is currently between 1 and 2% per year. Furthermore, the density of refuse has been dropping, resulting in even greater increases in volume, with annual values of up to 5 cubic metres per capita not uncommon. The EEC/EU as a whole generates some 2000 million tonnes of waste annually, about 20 million of which was hazardous waste. On average, an estimated 60 of domestic waste was dumped, 33% incinerated and 7% composed (1990 figures). The UK has the highest rate of landfill: 90%, with 10% incinerated. The problem of waste disposal is a cross-border one because, until comparatively recently, Member States could find other countries who would receive and dispose of their waste more cheaply.
The above data show representative waste contributions in highly developed urban centres in industrialized countries with relatively high standards of living. Although the figures for other areas are lower at present, they can be expected to approach these figures in time. In developing countries, the amounts of solid wastes may well be very small percentages of the figures given. However, the data do not adequately reflect the additional solid wastes produced by agricultural and large industrial operations, nor do they take into account the solid pollutants increasingly being separated from gaseous and liquid wastes by improved treatment processes developed to comply with stricter environmental standards.