United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S8-89/062 June 1990
&EPA Project Summary
Municipal Waste Combustion
Assessment: Medical Waste
Combustion Practices at
Municipal Waste Combustion
Facilities
V. J. Landrum and R. G. Barton
The EPA's Office of Air Quality
Planning and Standards (OAQPS) is
developing emission standards and
guidelines for new and existing
municipal waste combustors (MWCs)
under Sections 11l(b) and 111(d) of
the Clean Air Act. This report
provides background information on
the burning of medical waste in
MWCs. The components of medical
waste are defined, and the potential
air pollution emission impacts from
burning medical waste in MWCs are
discussed. MWCs in the U.S. which
have reported burning medical waste
are identified. The methods employed
in handling and burning the medical
waste at each facility are
summarized. Important transporta-
tion, handling, and operating
procedures which must be
considered with respect to potential
worker safety and health problems
are discussed. Finally, current
practices and regulations concerning
the incineration of medical waste in
Canada and Europe are summarized.
Additional research and field tests
are needed to fully evaluate the
impacts of burning medical waste on
the emission of acid gases,
dioxin/furans, and trace metals.
Further work is also needed to define
combustion conditions necessary for
the complete destruction of solvents,
cytotoxic chemicals, and pathogens.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering Information at
back).
Summary
The U.S. EPA is currently developing
air emission standards for new and
existing municipal waste combustors
(MWCs) under Section 111 of the Clean
Air Act. In addition, as part of the Medical
Waste Tracking Act of 1988, EPA must
prepare a comprehensive report to
Congress identifying sources, handling
procedures, transportation, treatment.
and disposal of medical waste. This
report must also include an assessment
of the present and potential threat that
medical waste represents to human
health and the environment. It was
determined in the MWC information
gathering effort that a number of MWCs
burn medical waste. The impacts of this
practice on air emissions are currently
not known. Based on these uncertainties,
a study was conducted to examine and
define the practice of incinerating
medical waste in MWCs and identify
potential air emission impacts as well as
potential worker health and safety
problems associated with this practice.
This report defines and characterizes
types of medical waste, discusses
possible impacts of burning medical
waste on combustor emissions, and
outlines important handling and operating
considerations. Facility-specific
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design,handling, and operating practices
are discussed for U.S., European, and
Canadian MWCs that reportedly accept
medical waste. The handling and
operating guidelines and philosophies of
U.S. and European MWC manufacturers
regarding medical waste incineration are
also discussed. The report concludes
with a discussion of preliminary findings,
recommendations, and research needs.
Medical waste is defined as any type of
waste generated by a biomedical
institution, including hospitals, medical
laboratories, animal experimentation
units, and clinics. Two features of
medical waste are of key importance.
First, the physical and chemical
characteristics of the waste are highly
variable. The heat content of the waste
can vary from a low of 1000 Btu/lb (2.326
x 106 J/kg) for human tissues, organs,
and body parts to a high of over 15.000
Btu/lb (3.489 x 107 J/kg) for plastic
containers and disposable equipment. In
addition to heat content, the ash,
moisture, chlorine, and metals contents
can also vary significantly from one batch
of waste to another. Second, many of the
components of medical waste require
special attention. These components are
cytotoxic chemicals, hazardous
chemicals, pathogens, toxic metals, and
radioactive materials. MWCs burning
even small percentages of medical waste
must be able to accommodate highly
variable waste compositions and heat
content as well as many of the potentially
dangerous components.
Limited information is available on the
emission impacts associated with
combustion of medical waste in MWC
facilities. However, these impacts can be
qualitatively discussed based on the
composition of medical waste and
emissions data from medical waste
incinerators. The classes of air pollutants
evaluated include acid gases, dioxins,
and metals. Acid gas emissions may
increase due to the high chlorine content
of the plastic items commonly found in
medical waste. Baseline HCI emissions
from MWCs burning municipal waste
may range from 100 to 1000 ppm. Co-
firing large amounts of medical waste
may increase baseline HCI emissions.
Medical waste incinerators have been
found to emit dioxins at about the same
concentrations as typical municipal waste
incinerators (100-2000 ng/dscm).
Although dioxin formation is more
strongly correlated with system design
and operation, dioxin emissions may also
be affected to some extent by waste
characteristics. Medical waste has a
number of characteristics that could lead
to dioxin formation. A significant amount
of aromatic compounds are present that
may serve as dioxin precursors. Medical
waste also contains a high concentration
of chlorinated plastics and is highly non-
homogeneous. Some components of the
waste have high moisture contents.
These materials may create localized low
temperature zones within the waste bed,
resulting in fuel-rich pockets that may
escape complete destruction in the
furnace.
Medical waste contains such toxic
metals as mercury, cadmium, and
arsenic. These metals are volatile and
may vaporize in the incinerator. The
metal vapors would then be carried away
in the exhaust gases. As the exhaust
gases cool, the metals would be
adsorbed on the surface of the fly ash or
would condense to form small particles
which are difficult to capture. A significant
fraction of these fine condensed particles
may be emitted to the atmosphere.
Mercury, cadmium, and arsenic have
been detected in hospital waste
incinerator exhausts.
Beyond emissions concerns, a number
of other factors must be considered when
burning medical waste in MWCs.
Transportation and handling is an
important factor when medical waste is
incinerated off-site as compared to an on-
site hospital incinerator. Precautions must
be taken, including placing the waste in
sealed, secure containers, to ensure that
none of the waste materials escape
during transportation. Storage times
should be kept as short as possible and
containers must not be opened or
breached until they are in either the
combustor or a secure environment.
Incinerator operation characteristics such
as temperature, and time at a
giventemperature are also important
factors relating to pathogen and cytotoxic
chemical destruction. Also, the medical
waste should be rendered
"unrecognizable." That is, one should not
be able to recognize body parts and
medical equipment in the residual ash.
Ash handling and disposal are important
as well due to potential pathogen survival,
radioactivity, and metals content of the
ash. Studies of the ash from hospital
incinerators indicate that relatively large
quantities of cadmium and lead are
present
There are at least 15 U.S. municipal
waste combustors that have previously
accepted or are currently accepting
medical waste including a variety of
combustor design types. The amount of
medical waste burned in these units
ranges from less than 1 to 50% by
weight. Based on the preliminary
findings, it appears that sharps pose ai
problem in MWCs with grate systems.
Sharps in the ash represent potential
safety and health problems to facility
personnel or landfill operators coming in
contact with the ash. Animal carcasses
also represent a significant problem if the
carcasses are not completely destroyed
because of poor waste burnout. Before
incineration, attention must be given to
the medical waste handling procedures to
prevent penetration of containers and
exposure of containerized wastes. For
example, many of the facilities manually
place sealed boxes of medical waste
directly into a closed overhead grapple to
avoid penetration of the boxes and
exposure of the medical waste.
Only very limited data are available on
the emission impacts associated with
combustion of medical waste in MWCs
More information is needed to full^
evaluate the potential impacts of burning
medical waste on the emissions of acic
gas, dioxin, and metals. Also, furthei
information is needed to determine th?
design and operating requirements fo
complete destruction of hazardous
solvents, cytotoxic chemicals, anc
pathogens.
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V. J. Landrum and R. G. Barton are with Energy and Environmental Research
Corp., Durham, NC 27707.
James D. Kilgroe is the EPA Project Officer (see below).
The complete report, entitled "Municipal Waste Combustion Assessment:
Medical Waste Combustion Practices at Municipal Waste Combustion
Facilities," (Order No. PB 90-186 990/AS; Cost: $15.00, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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