A major consideration with respect to solid waste incineration project economics is heat
recovery by linked district heating schemes, but such schemes are only realistic when
incinerators are in close proximity to solid waste generation, i.e., in urban environments,
and where heating is required for most of the year. Alternative approaches to solid waste
incineration are offered by using solid waste as fuel in cement kilns, although the cement
industry might not wish to add to its existing environmental problems, and, in the future,
by gasification.
Finally, in the context of thermal solid waste treatment, mention should be made of the
rendering industry, which has traditionally provided thermal treatment for slaughterhouse
waste. Rendering is an industry that has been tolerated rather than accepted. The industry’s
product is meat and bone meal, which has traditionally been used as an animal feed
ingredient. To enhance the protein quality of meat and bone meal, rendering temperatures
have been reduced, with the unfortunate effect that prions present in specified material
from infected bovine carcasses have not, in all cases, been completely eliminated from the
meat and bone meal product, causing subsequent infections in cattle that were fed
contaminated meal, but even more alarmingly, through possible cross-species transfer,
fatal infections in humans who might have consumed meat products contaminated with
specific material from such cattle.
The failure of high-temperature processes to provide absolute safety with respect to
infectious agent survival is a cause for significant concern and points to a pressing need for
studies that elucidate the fate of pathogenic agents both in treatment processes and in the
natural environment that provides the ultimate sink for residues of waste treatment
processes and to potential dangers that pathogen-contaminated residues might pose