Advanced thermal treatment technologies utilizing pyrolysis or gasification, as well as a combined
approach, are introduced as sustainable methods to treat wastes in Singapore. Eight different technologies
are evaluated: pyrolysis–gasification of MSW; pyrolysis of MSW; thermal cracking gasification of granulated
MSW; combined pyrolysis, gasification and oxidation of MSW; steam gasification of wood; circulating
fluidized bed (CFB) gasification of organic wastes; gasification of RDF; and the gasification of tyres.
Life cycle assessment is carried out to determine the environmental impacts of the various waste conversion
systems including global warming potential, acidification potential, terrestrial eutrophication and
ozone photochemical formation. The normalization and weighting results, calculated according to Singapore
national emission inventories, showed that the two highest impacts are from thermal cracking gasification
of granulated MSW and the gasification of RDF; and the least are from the steam gasification of
wood and the pyrolysis–gasification of MSW.
A simplified life cycle cost comparison showed that the two most costs-effective waste conversion systems
are the CFB gasification of organic waste and the combined pyrolysis, gasification and oxidation of
MSW. The least favorable – highest environmental impact as well as highest costs – are the thermal cracking
gasification of granulated MSW and the gasification of tyres.