Book - School of Science and Technology

316 Fuels, storage and handlingTable 11.14 Composition of municipal wasteWastecomposition Biodegradable Recyclable Reject ratePaper/card 32% 100% 65% 5%Putrescible 21% 100% 90% 5%Textiles 2% 50% 95% 5%Fines 7% 60% 0% 0%Misc. combustible 8% 50% 0% 0%Misc. non-combustible 2% 0% 0% 0%Ferrous metal 6% 0% 95% 5%Non-ferrous metal 2% 0% 95% 5%Glass 9% 0% 90% 5%Plastic dense 6% 0% 33% 5%Plastic film 5% 0% 0% 5%equipped with accessible heat exchangers, and most importantly effective flue gas cleaningmethods. The characteristics of such waste material vary so widely that no sensiblegeneralisations are of use.The data given in Table 11.14 illustrate the composition of municipal waste drawn fromnational statistics*. These should be treated as no more than a representative mixture,since there will be considerable seasonal and regional variations. Earlier work has indicatedthat municipal waste may have a gross calorific value of the order 6±8 mJ/kg, butthis was based upon statistics from the early 1980s which have since changed reflectingour lifestyle habits over the period.In contrast to urban waste, various sources of biomass are being investigated and insome cases trialled as a source of boiler fuel, of which boiled straw, pelletted turkey wasteand forestry products are a few examples.* Waste Strategy 2000 for England and Wales, DETR, May 2000.