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9 Incineration of MSW

Such myriads of flames I saw shine through
the gloom of the eighth abyss when I arrived
at the rim from which its bed comes into view.
Dante
The Inferno

9.1 INTRODUCTION

Incineration is defined as the controlled burning of solid, liquid, or gaseous wastes. The term con-
trolled is emphasized here in order to distinguish the technology from simple open burning or other
similarly unsound processes. Controlled conditions often include an oxygen-enriched combustion
zone under elevated temperatures, the use of auxiliary fuel, vigorous agitation of the incoming
waste, and the use of a forced air system throughout.
The primary purpose of municipal solid waste (MSW) incineration is volume reduction,
with the ultimate result of extending the lifetime of the land disposal facility. It has been
reported that reductions of 80 to 90% of the total MSW volume are possible through incinera-
tion, although reductions of 50 to 60% are more realistic. Reductions of up to 95 to 99% of the
combustible fraction (paper products, plastics, food waste, and yard waste) have been reported.
Compaction of the ash residue will result in some additional volume reduction, and recovery of
metals from the residue will further reduce volume. Therefore, MSW processed in a municipal
incinerator and then compacted in a landfill may occupy only 25% of its original volume. It is
estimated that incineration in combination with sanitary landfilling can double the life span of
a disposal facility.
A second purpose of incineration has been labeled “waste to energy”, i.e., the recovery of heat
energy from combustion for water or space heating, or electricity generation. A third, albeit unin-
tended benefit of incineration is detoxification — the destruction of microbial and other pathogenic
organisms — of the waste.
As shown in Chapter 4, MSW is extremely heterogeneous in composition; therefore, a wide
assortment of residues is produced that will require additional processing and disposal. The residues
include:

● Acidic gases such as SO ,NO and HCl
2 x
● Trace gases (e.g., chlorinated dibenzodioxins) that are hazardous at very low concentrations
● Particulate matter carried by the gas stream. Also known as “fly ash”, dust, and soot, this
can take the form of solids or liquids suspended in the air stream
● Incinerator residue (“bottom ash”)
● Process water

Current incineration capacity is estimated by the U.S. EPA to accommodate about 10 to 12%
of the total municipal waste stream in the United States. More than 100 communities are in the early
stages of planning new incinerators (NAS, 2000).

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