MSW is collected for disposal by urban communities in all industrialized countries, so there is no question regarding its physical availability as a waste biomass feedstock in centralized locations in these countries. The question is how best to utilize this material if it is regarded as an “urban ore” rather than an urban waste. The data in Table 5.1 show that in the mid-1990s, a large portion of the MSW generated in the United States was available as feedstock for additional energy recovery processing. As indicated above, landfilled MSW can provide energy as fuel gas for heat, steam, and electric power production over long time periods. Surface-processing of MSW can also provide energy for the same end uses when MSW is used as a fuel or a feedstock.

Energy Potential

At a higher heating value of 12.7 MJ/dry kg of MSW (Table 3.3), the energy potentially available from the MSW generated in the United States in the 1990s is in the range of 2.5 EJ/year. Presuming the total combustibles in the recovered

‘Adapted from Franklin Associates (1994). Sums of individual figures may not equal totals because of rounding. The data in this table are for postconsumer residential and commercial MSW, which makes up the major portion of typical collections. Excludes mining, agricultural, and industrial processing, demolition and construction wastes, municipal biosolids, and junked autos and equipment wastes. Based on material-flows estimating procedure and wet weight as generated. Other wastes are predominantly foodstuffs, leather, rubber, textiles, and wood.

fractions of MSW are utilizable and that the energy recovery systems in opera­tion continue to be used, the data for the United States indicate that about 60 to 65% of the MSW generated could have supplied up to an additional 1.6 EJ/year in the mid-1990s. New energy recovery plants supplied with MSW feedstock could also provide an additional benefit by increasing the life of landfills. Only the unrecyclable inorganic materials in the ash would be land­filled if thermal processing of the MSW is employed. Some of the ash itself could be used as material of construction, such as in roadbeds and other applications.