Incineration
Description
High temperatures, 870 to 1,200 ¡C (1,400 to 2,200 ¡F),
are used to volatilize
and
combust halogenated
and other organics
in hazardous
wastes. Auxiliary fuels are used to initiate and sustain
combustion.
Incinerator designs are geared towards different waste streams and
different
end products, and operating temperatures vary with the different
designs. The
destruction and removal efficiency for properly operated incinerators
is 99.99%
for most waste. Off-gases
(emissions) and combustion residuals
generally require treatment. Air pollution-control systems are employed
to
remove particulates, as well as to neutralize and remove acids.
Incineration is different from other thermal technologies in that it
oxidizes bulk quantities of waste that may be in liquid and solid phase. Pyrolysis,
which
is described separately, uses heat in the absence of oxygen to destroy contaminants.
Thermal
and
Catalytic Oxidation treats only the vapor
phase of
contaminants.
Limitations and Concerns
Incinerators may release
carcinogenic and toxic chemicals from their stacks, including heavy
metals,
partially-burned organic material such as polyvinyl chloride (PVC), herbicide
residues, and other organic chemicals, including polycyclic aromatic
hydrocarbons
(PAHs), dioxins
and furans.
When chlorinated hydrocarbons are incinerated, products of
incomplete
combustion are formed. These may include dioxins and furans. Several
PAHs,
dioxins and furans are known or suspected human carcinogens. Dioxins
are toxic
in the parts per trillion range. Even with the best practices,
formation of
these products may take place as gases leave the stack.
Only one off-site incinerator is permitted in the United States to
burn
wastes that contain polychlorinated
biphenyl (PCB) and dioxin. It reportedly achieves 99.9999%
destruction
efficiency.
Wastes with heavy metals can produce a bottom ash with high
concentrations
of hazardous substances. The ashes may require disposal
and/or
stabilization. Some heavy metals, including lead, cadmium, mercury, and
arsenic
may partially vaporize and leave the combustion unit with the flue
gases. This
may require gas-cleaning systems for removal.
Metals can react with other elements in the feed stream, such as
chlorine or
sulfur, forming compounds that are more volatile and toxic than the
original
species. Most of these compounds are short-lived reaction intermediates
that
can be destroyed.
If an off-site incinerator is used, the potential risk of
transporting the
hazardous waste through the community must be considered.
A British study conducted recently found statistically significant
increases
for all cancers combined among people living within 7.5 kilometers of
an
incinerator.
Three French solid waste incinerators were closed in January, 1998
because
milk from cows on nearby dairy farms was contaminated with excessive
levels of
dioxins. A municipal incinerator near Maubeuge in northern France has
contaminated cows' milk at levels of 22 parts per trillion (ppt)
in milk fat.
Applicability
Incineration is used to remediate soils contaminated with explosives
and
hazardous wastes, particularly chlorinated hydrocarbons. One
incinerator in the
U.S. treats soils contaminated with PCBs and dioxins.
Technology Development Status
Incineration is a commercial technology. It has been selected or
used as the
remedial action at more than 150 Superfund
sites.
Web Links
http://www.frtr.gov/matrix2/section4/4-23.html
http://www.clu-in.org/download/remed/incpdf/incin.pdf
Other Resources and Demonstrations
See the technology descriptions for Thermal
Desorption,
Oxidation,
Flameless
Thermal
Oxidizer, and Pyrolysis.
See Julia G. Brody and Terry Greene, "Incineration: Decisions
for the 1990s"
(Boston, Mass.: Tellus Institute and JSI Center for Environmental
Health
Studies, 1994). Available from JSI Center for Environmental health
Studies, 210
Lincoln St., Boston, MA 02111; telephone (617) 482-9485.
See International Agency for Research on Cancer (IARC), "Monographs
on
the Evaluation of Carcinogenic Risk to Humans: Volume 69,
Polychlorinated
Dibenzo-Para-Dioxins and Polychlorinated Dibenzo-furans," Lyon, France,
February, 1997.
See http://www.clu-in.org/download/contaminantfocus/dioxins/Dioxin-Treatment-Technologies-OTA-9116.pdf
for dioxin treatment, including incineration.