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Incineration of MSW 279
and the coal second. Such uneven burning will cause fluctuations in steam production. This segre-
gation problem can be partly alleviated by mixing the fuels in the field, immediately before burn-
ing (Figure 9.16).
The RDF may cause problems in storage. It is fibrous, carbonaceous, and of relatively low density.
Contact with rainfall will rapidly alter the physical and chemical properties of the RDF. Pelletized RDF
will decompose and lose its physical strength and will no longer be easily handled. Second, a wet mate-
rial will rapidly undergo anaerobic reactions. The RDF has many fine pores which will tenaciously
retain moisture. Foul odors will be produced and the RDF will cause the growth of mold and other
undesirable organisms. The best precautions against this scenario are to store it indoors or in a covered
facility in the field. Furthermore, storage of RDF should not be prolonged; ideally, it should be burned
within 24 h of its production. Poslusny et al. (1987) found that addition of a Ca(OH) binder to the pel-
2
lets during initial processing was successful in lengthening the storage lifetime of the pellets.
Dust production is inevitable with storage and handling of dry RDF; therefore, dust control
equipment must be provided within both the combustion and storage areas. Forced ventilation com-
bined with air filters are strongly recommended.
It should be clear by now that mechanical separation of MSW components is by no means 100%
effective; therefore, contamination by food and yard waste, and other undesirable components will
occur. As a result, odor production is inevitable in stored RDF, particularly in the warmer months.
The RDF must therefore not be stored in a boiler building for extended periods; rather it should be
loaded into the building daily for combustion.
In a study by Fiscus et al. (1978), total airborne bacteria concentrations were measured in a
number of waste handling facilities including a RDF plant, incinerator, landfill, transfer station,
waste collection vehicle, and wastewater treatment plant. The highest airborne bacterial concentra-
tions were found in the RDF plant. Mahar (1999) studied the atmospheres in several locations
within two RDF facilities. The data for particulate matter appear in Table 9.9, and that for total
bioaerosols and endotoxins are in Table 9.10. The particulates detected were primarily in the non-
respirable size range. Biologically derived particulates were found to a greater extent in areas where
the waste had been processed as opposed to stored.

9.8.5 GASEOUS EMISSIONS AND CORROSION ISSUES
When combusting a fuel containing 100% RDF, emissions of acid gases and hydrocarbons were
consistently lower compared with bituminous coal alone (Pichtel, 1991). Oxides of sulfur and NO x
3
3
measured approximately 700 and 200 mg/m compared with 1600 and 550 mg/m , respectively, for

TABLE 9.9
3
a
Particulate Comparisons (mg/m ) in Different Areas of an
RDF Plant
Location Inhalable Particles Total Particles Respirable
Particles
Floor 2.24 (7) 1.15 (6) 0.09 (7)
Loadout 0.52 (2) 0.15 (2) 0.04 (2)
Lunchroom 0.13 (3) 0.06 (3) 0.07 (3)
Magnetic separator 3.06 (4) 1.26 (4) 0.10 (4)
Processing 0.73 (4) 0.38 (3) 0.16 (4)
a Geometric mean, n
Source: Mahar, S., Waste Manage. Res., 17, 343–346, 1999. Reproduced with
kind permission of the International Solid Waste Association.