SOURCES OF WASTE
There are two principles types of waste suitable for disposal in a power-from- waste plant: urban (primarily domestic) refuse, normally referred to as MSW, and industrial waste. Some industrial waste is broadly similar in content to MSW and this can be treated in the same way as the latter. Other industrial waste must be dealt with differently because of the hazardous or valuable materials it contains. This chapter is only concerned with MSW and it will not deal with industrial waste except where it can be burned with MSW.
The main source of MSW is an urban community. In the developed world the waste from rural communities may be handled in a similar way but this is rare in the other parts of the world. The quantity and size of such communities is growing rapidly. In the last two generations the number of people living in cities has increased by 250–500%2 and the trend is set to continue for perhaps another generation. In the United Kingdom, for example, 79% of the population already lived in cities by 1950 but this is expected to rise to 92% by 2030. In China only 13% of the population lived in cities in 1950 but by 2030 the proportion should reach 60%. Urban dwelling has grown particularly rapidly in South America and the Caribbean where, by 2025, 80% of the populations will be living in towns. But these regions are not unique. Urban communities are growing virtually every- where. In 2008, for the first time, more than half the world’s population, or around 3.3 billion, lived in cities and towns. By 2030 the number of city dwellers is expected to reach 5 billion. These towns and cities constitute the source of MSW. The amount of waste these populations produces varies from country to country and from continent to continent. In general, the city dweller in an industrialized country produces far more waste than one in a developing country. Thus, a typical Californian might produce 1.3–1.4 kg each day while a city dweller in Mexico City produces only half that. A Nigerian town dweller probably produces less than 200 g of waste each day.
According to the World Watch Institute, global municipal solid waste generation at the end of the first decade of the 21st century was around 1.3 billion tonnes. By 2025 the global annual production could double to 2.6 billion tonnes. The greatest producers were the 34 members of the Organization for Economic Cooperation and Development, which produced on average 1.6 million tonnes each day. Sub-Saharan Africa, by contrast, only produces 200,000 tonnes a day.