technical BRIEF
BUILDING A SCIENTIFIC FOUNDATION FOR SOUND ENVIRONMENTAL DECISIONS
i
Identification and Screening of Infectious Carcass
Pretreatment Alternatives
Introduction
Managing the treatment and disposal of large numbers of animal carcasses following a
foreign animal disease (FAD) outbreak is a challenging endeavor. Pretreatment of the
infectious carcasses might facilitate the disposal by simplifying the transportation,
reducing the pathogen load, or by
isolating the pathogen from the
environment to minimize its
spread. This brief summarizes
information contained in U.S.
Environmental Protection Agency
(EPA) report (EPA/600/R-15/053)
entitled Identification and
Screening of Infectious Carcass
Pretreatment Alternatives. This
brief describes how each of eleven
pretreatment methods can be used
prior to, and in conjunction with,
six commonly used large-scale
carcass disposal options (Figure 1).
Bioreduction
Alkaline
Digestion
Hydrolysis
On-Site Size
Reduction
Burial
Burning
Sterilization
Composting
Disposal Options
Packaging
Rendering
Incineration
Freezing
Encapsulation
Physical
Inactivation
Additives/
Sorbents
Chemical
Inactivation
Figure 1. Depiction of Carcass Disposal Technologies
and Potential Pre-treatment Technologies
The six disposal options considered are:
•	rendering	• landfill
•	burial	• composting
The eleven pretreatment methods considered are:
•	on-site size reduction • alkaline hydrolysis
•	digestion	• sterilization
•	bioreduction	• addtitive/sorbent
•	encapsulation	• packaging.
•	incineration
•	burning
•	physical inactivation
•	chemical inactivation
•	freezing
The advantages and disadvantages of the pretreatment methods are listed in Table 1.
Disposal and Pretreatment Methods
Animal carcasses considered here include whole bodies or body parts of dead animals, which
could be inseparably mixed with manure and bedding or other organic materials. Regulation of
carcass management vary from state to state. Treatment and disposal can require special
permit(s) approved by federal (e.g., United States Department of Agriculture), tribal, state and
Disclaimer
The USEPA through its Office of Research and Development managed the research described here, it has been
subjected to the Agency's review and has been approved for publication. Note that approval does not signify that the
contents necessarily reflect the views of the Agency. Mention of trade names, products, or services does not convey
official EPA approval, endorsement, or recommendation.
August 2016
EPA/600/F-16/111

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local agencies. For all disposal and pretreatment methods, applicable federal, state, local, and
tribal laws and regulations must be followed.
Throughout the U.S., the disposal of animal carcasses is regulated by state laws that vary
according to animal species. While there are several methods for disposal of animal carcasses,
the most common are the following six disposal options (Figure 1):
•	Rendering for the purpose of disposal of contaminated carcasses involves a series of
processes using high temperature and pressure to treat large animal and poultry carcasses
or their by-products. The processes include a combination of blending, cooking,
pressurizing, fat melting, water evaporation, and microbial and enzyme inactivation. A pre-
rendering process involves size reduction and conveying, and post-rendering process
involves screening the protein and fat materials, sequential centrifugations for separation of
fat and water, and drying and milling of protein materials.
•	Burial refers to the placing of the infectious carcasses within the ground at the site of the
incident. Many states advise that this option should only be used based on an environmental
assessment of site characteristics as well as the implementation of proper environmental
controls to protect groundwater, surface water, and soil from leachate.
•	Landfilling involves carefully designed structures built into or on top of the ground in which
waste is isolated from the surrounding environment. There are different types of landfills,
each designed to handle particular waste streams. Generally, each landfill is permitted or
licensed for particular kinds of waste. A landfill generally cannot accept waste that falls
outside the scope of its permit.
•	Composting for the purpose of disposal of contaminated carcasses is the controlled
biological decomposition of biomass in the presence of air to form a humus-like material.
Controlled methods of composting include mechanical mixing and aerating, ventilating the
materials by dropping them through a vertical series of aerated chambers, or placing the
compost in piles out in the open air and mixing it or turning it periodically. This treatment
option is distinct from backyard composting, which is conducted by individuals on their own
property. Instead, composting, as a treatment option, is used to decompose large quantities
of waste either on a farm in association with animal disease control activities or at off-site
composting facilities. Off-site composting will trigger transportation considerations.
•	Incineration for the purpose of disposal of contaminated carcasses burn the biomass at
high temperature under controlled conditions. Different incinerators are permitted for
different kinds of waste.
•	Burning, i.e., the deliberate outdoor burning of waste, can be done in open drums, in fields,
and in large open pits or trenches. The use of this option is highly restricted; many states
and local communities have laws regulating or banning open burning. Under certain
conditions, emergency waivers may be issued.
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Review of Pretreatment Options
ON-SITE SIZE REDUCTION
On-site size reduction is the manual or
mechanical cutting, grinding, or crushing
of the carcass to decrease the
dimensions of the resultant parts for ease
of handling, to decrease volume, or to
enhance further processing. Key size
reduction processors include crushers,
shredders, and grinders (Figure 2). On-
site grinding for size reduction is
advantageous for rendering, composting,
burial, landfill, and incineration and
reduces the risk associated with transporting whole carcasses. For example, decomposition of
the carcasses can be sped up by up to 50 percent by grinding them before composting.
DIGESTION
Digestion is a process that liquefies
carcasses under acidic conditions,
either using lactic acid or phosphoric
acid (Figure 3). Lactic acid fermentation
uses bacteria to ferment the material
primarily into methane, carbon dioxide,
and water. Phosphoric acid preservation
essentially pickles the carcasses or
biomass.
Lactic acid fermentation is a process by
which lactic acid bacteria are added to ground carcasses with fermentable carbohydrates to
produce lactic acid under anaerobic conditions. These bacteria can produce volatile acids,
hydrogen peroxide, and antibiotic-like compounds that inhibit many bacteria. A variety of animal
carcasses can be treated with lactic acid fermentation, including cattle, swine, poultry, sheep,
goats, fish, and wild birds. In the phosphoric acid preservation process, phosphoric acid is
added directly to ground or small pieces of carcasses. The phosphoric acid disrupts the
membrane functions of the microorganisms, reducing their disease-causing activity.
BIOREDUCTION
Bioreduction is the biodegradation of animal by-products or whole carcasses in a partially
sealed vessel, where the contents are mildly heated and aerated. Bioreduction is a method that
simultaneously permits storage and reduction in the volume of carcasses and that relies on
internal enteric microorganisms and enzymes to drive decomposition. Carcass material is
placed in a watertight vessel, where the contents are heated (to 40 ± 2 °C) and actively aerated
with a pump. Bioreduction is also described as complete bio-digestion and liquefaction of
3
Windrows-of-composted
ground-carcassesH
Carcass-being-
lifted-intogrinderD
Figure 2. Large-Scale Mobile Carcass Grinder
Figure 3. Carcass in Digester
(Photo courtesy - Jeff Miller, University of Wisconsin-Madison)

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carcasses. The bioreduction vessels can be buried in the ground, so the overall footprint of the
operation is reduced. Transmissible spongiform encephalopathy (TSE) agents are not
destroyed at the operational temperatures of bioreduction.
ALKALINE HYDROLYSIS
Alkaline hydrolysis occurs when sodium hydroxide or potassium hydroxide is mixed with
biological materials such as protein, nucleic acids, carbohydrates, and lipids (Figure 4). Heat
can be applied (150 °C or ~300°F) to significantly accelerate the process. The result is a sterile
aqueous solution consisting of small peptides, amino acids, sugars, and soaps. As the process
is generally conducted at 150 C in a 1N potassium hydroxide (KOH) for greater than 6 hours,
the resulting effluent (pH 9-10) needs to be cooled and neutralized prior to disposal. When the
alkaline solution is properly treated, it may be safe for disposal in wastewater or sewer
systems.
Figure 4. Representative Alkaline Hydrolysis Units
STEAM STERILIZATION
Steam sterilization is the process of destroying microorganisms and infective agents with heated
water under pressure. The steam sterilization process is time-, temperature-, and pressure-
dependent. In this wet thermal treatment, the waste is first shredded and then exposed to high-
pressure, high-temperature steam. Steam sterilization has similarities to the process of
autoclave sterilization. The sequence of operations can vary from manufacturer to
manufacturer. For example, STI (Biosafe Engineering, Brownsburg, Indiana) first performs
shredding, but there is no pressure under their current STI models. The Rotoclave® rotating
autoclave (Tempico Manufacturing, Hammond, Louisiana) includes a pressurized autoclave
system, but there is no "pre-shredding" of the waste. The Rotoclave system rotates so that
cutting blades can chop up the waste while it is being steamed under pressure. Application of
steam can be with or without pressure, and with or without shredding, depending on the system.
Given a suitable temperature and contact time, most varieties of microorganism are inactivated
by wet thermal disinfection (for example, sporulated bacteria require 121 °C [249.8 °F]).
FREEZING
Freezing animal carcasses can be done in fixed facilities or mobile units. Freezer types include
chest freezers, crust freezers, mobile freezer units, and refrigerated industrial trucks. For large-
scale applications, industrial trucks can be used on-site to store and transport carcasses.
Although freezing of carcasses might have little implication for decreasing pathogens, this
method can be effective in extending the storage time and helping transportation while
eliminating or minimizing the decomposition process.
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PHYSICAL INACTIVATION
Physical inactivation is the process of eliminating pathogenic microorganisms (excluding
bacterial spores) from inanimate objects. Different inactivation methods have different target
ranges, not all methods can kill all microorganisms. Inactivation is different from sterilization,
which is an absolute condition where all the microorganisms, including bacterial spores, are
killed. Of the potential physical methods only steam was considered a potential for carcass
treatment.
Figure 5. Handling and Processing of Carcasses
CHEMICAL INACTIVATION
Chemical inactivation is the use of chemical agents to kill/destroy pathogens, including bacteria,
bacterial spores, and to inactivate viruses and prions. A wide variety of chemicals are available
and these chemicals include but are not limited to oxidizers (chlorine, hypochlorite, ozone, and
peroxide), organic acids (lactic acid, acetic acid, and gluconic acid), organics (benzoates,
propionates), bacteriocins (nisin, magainin [antimicrobial peptides]), and acidic and basic
electrolyzed water. Chemical inactivation can be used in conjunction with other carcass
treatment processes, such as size reduction. Depending on the overall treatment scheme,
chemical inactivation can be performed during size reduction by addition of chemical additives
and mixing or can be applied on the surface of the whole carcass (Figure 6). Surface chemical
inactivation would allow for increased biosafety during loading and transport of carcasses,
however, it would not serve to reduce pathogens released during decomposition while in transit.
There are numerous vendors who supply these chemicals.
5

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Type of Microorganism

Biocide
0
"V egetative
bacteria
(Gram +)
d?
Vegetative
bacteria
(Gram -)
*
Mycobacteria
(Gram +)
H,
Fungi
0
Viruses
o
Bacterial
Spores
Mode of Action
Oxidizing
Halogen containing compounds
Chloramines
0
d?
a
QQ9
0
o
Similar to hypochlorite
but less active.
Iodine
Compounds
0
d?
£

QAJJ
0

o
Attacks N-H and S-S/S-
H protein bonds.
Sodium
hypochlorite
0
d?


(W)
0

o
Oxidizer of biologic al
molecules (e.g.,
proteins., nucleic acids).
Non-halogen containing
compounds







Hydrogen
peroxide
0
d?
a
UJ
IJ
0
o
Generates hydroxyl free
radicals, which attack
biological molecules.
Non-osidizing
Cationic
surfactants
0
&
Z3
(W,
0
o
Affects proteins
metabolic reactions,
cell permeability', etc.
Formalin (37%
formaldehyde)
0
6>
a
anj)
U
0
o
Affects the cell wall
and denatures amino
proteins.
Glutar aldehyde
0
6>
£j

(W)
0

o
Affects proteins (e.g.,,
enzymes, transport of
nutrients, cell wall, etc.)
Peraclean®
(peracetic
acid)
0
d?
[j

(UJJJ
0

3
Potent oxidizer
Phenol
0
d?
£

(W)
o
o
Combines with and
denatures proteins.
J Susceptible
| | Resistant
e
Somewhat
susceptible
0
Susceptible at high
concentrations
Figure 6. Effects and Mode of Action of Selected Chemical Inactivation Agents1
(Chattopadhyay, S. et ai., 2004. Evaluation of Biocides for Potential Treatment of Ballast Water. U.S. Department of
Homeland Security, U.S. Coast Guard, Report No. CG-D-01-05.)
1 Prions may not be considered to be what are currently defined as microorganisms, but at the same time they are
transmissible and usually resistant to physical and chemical inactivation. Environ LpH (Steris Corp., St. Louis,
Missouri), a commercial disinfectant, has been effectively inactivated prions. Prion inactivation occurs with a 1
percent solution of LpH for 10 hours or with a 10 percent LpH solution for one hour. Environ LpH is not as corrosive
to surfaces as bleach or NaOH. It should be thoroughly mixed to prepare a treatment solution until uniform
consistency can be achieved. User must observe the precautions and safety requirements on the registered
product label.
6

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ADDITIVE/SORBENT
Additive/sorbent is a supplemental material mixed with or otherwise added to create a favorable
condition by keeping away insects and rodents, increase movement of oxygen throughout the
processed material, and absorb excess liquid produced by the decomposing carcass.
Additive/sorbent materials (like wood chips, corn silage, straw/manure, rice hulks, and ground
cornstalks) help keep the processed material porous, and permeable to gas. Smaller materials
(like, sawdust) help absorb the liquid due to water holding capacities and contribute more
compaction properties. These additives are also a carbon source needed to sustain the
microbes. A combination of suitable additives with appropriate water holding capacities,
porosity, gas permeability, and compaction can allow optimal oxygen passage while absorbing
any excess liquid. In addition, additives/sorbents reduce potential spread of organisms during
transport of processed or unprocessed material. Additives and sorbents are widely available
from numerous local stores and vendors.
ENCAPSULATION
On-site carcass foam encapsulation is the treatment of the carcass with cementaceous
materials (such as Portland cement, gypsum cement, pozzolanic fly ash, aluminum, and
dolomitic lime matrix), Plaster of Paris, polyurethane foam, or commercial encapsulant. These
materials, when fully reacted, will encase the carcass in a solid protective matrix.
PACKAGING
Packaging, i.e., on-site carcass packaging or wrapping, is containment of the carcass
within a flexible or rigid container. Packaging can be done by rigid, leak-proof, break-
proof packaging, or permanently closed, with sufficient absorbent material included to
sorb and retain the liquid present.
Table 1. Advantages and Disadvantages of Carcass Pretreatment Technologies
Advantages
Disadvantages
On-site Size Reduction
•Mobile on-site
•Low environmental impact
•Very high throughput capacity
• Few safety issues for operators
•Ease in handling and transport of
processed material
•Accelerated decomposition
•Cost of capital equipment
•Operating cost of machinery
•Potential aerosol production
•Groundwater contamination if untreated effluent is
released
•Soil pollution if carcasses accumulate on the ground
faster than the processing rate
Digestion
•	Long-term storage
•	Kills pathogenic bacteria
•	Cost of storage is relatively low compared
to cold storage.
•	Increased biosecurity while minimizing the
need for frequent transportation
•	Produces several co-products:
biomethane, combined heat and power,
compressed natural gas, soil amendments
•If a digester is not available on site, carcasses must
be transported, increasing risk of spreading pathogen.
•Transmissible spongiform encephalopathy agent is not
inactivated; Lactic acid fermentation fails over 10
percent of the time.
•The capacity is relatively low
•Carcass pre-processing, such as grinding, is
recommended.
• Higher capital cost than composting.
•Operation requires skilled technicians.
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Bioreduction
•	Field and laboratory results showed that
the bacterial load is significantly reduced
and some pathogens are eliminated.
•	The entire pretreatment and disposal
process could be performed on-site with
no need for transporting carcasses.
•	Provides a method for storing carcasses
thereby reducing the number of collections
and transports
•	Overall biomass is reduced.
•Only research data are available for small-scale
operations.
•Not known to destroy prions (e.g., TSE agents)
•The geographical location and/or terrain limits where
vessels can be installed
•Can require additive (wood chip) to reduce malodor
and to reduce leaching to soil/groundwater
•No commercially available units were identified.
Alkaline Hydrolysis
•	Inactivation of viruses, bacteria, spores,
and TSE agents
•	Sterilization and digestion in one unit
•	Reduction of waste volume and weight by
as much as 97%
•	No air emission
•	Relatively low capacity
•	Potential issues with disposal of effluent
•	High pH of effluent must be neutralized prior to
disposal in a sewer system
Steam Sterilization
•	Inactivates most pathogens
•	Low environmental impact
•	Few safety issues for operators
•	Facilitates safe transport
•	Creates value-added product
•	High capital cost
•	Requires pre-configured and constructed systems
•	An inadequate shredder might retard efficiency.
•	Requires fuel and water logistics more than other
technologies discussed in this report
•	Operational conditions have a pronounced influence
on the efficiency of disinfection. Might not inactive
TSE agents
Freezing
•	Mobile and on-site freezing facilities are
available
•	Increases biosecurity for transportation
•	Prolongs storage for delayed disposal
•	Low cost rental units are available
•	Allows for flexibility of choosing one or
more disposal options
•	Mobile units may not be feasible for large-scale die-
offs of large animals
•	Thawing step required before size reduction,
rendering, burning, or incineration
•	Limited bacterial reduction; surface reduction only for
some methods of freezing
•	Energy cost and overall operating cost can be high
Physical Inactivation
•	Equipment readily available
•	Moderate equipment cost
•	Moderate safety issues
•	Potential for reduction of surface
infectious agents
•	Low environmental impact
•	Some steam applications alone do not reduce surface
bacteria
•	Significant wastewater/environmental impact
•	Potential for aerosolizing infectious agents
•	Slow/labor intensive, and it only removes surface
pathogens. As decomposition progresses, internal
pathogens will also be exposed.
Chemical Inactivation
•	Commercially available
•	Ease of application with little training of
personnel
•	Flexible to apply on site or centralized
facility in combination with grinding
•	Environmental concerns on spillage and final disposal
•	Surface treatment might not be effective
•	Some of the chemicals can be harmful
•	Storage prior to use and treatment of large volume of
effluents may be required
Additives/Sorbents
Natural Organic Sorbents
• Sustainable and low environmental impact
• Does not inactivate infectious agents
8

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•	Enhances efficacies of burial, landfill,
composting, and incineration
•	Few safety issues for operators
•	Facilitates safe transport and disposition
of carcass material
•	Low to moderate cost per carcass
•	Hard materials (wood chips) might not be rendered.
•	Dependent on the amount of sorbent addition,
increase in volume of material can increase disposal
cost
Inorganic Sorbents
•	Low environmental impact
•	Enhances efficacies of burial and landfill
•	Moderately safe for operators
•	Facilitates safe transport and disposition
of carcass material
•	Moderate cost per carcass
•	Eliminates rendering as a disposal option
•	Does not inactivate infectious agents
•	Unknown impact on composting.
•	Volatile toxics, if present, may not be suitable for
incineration and burning
Commercial (Chemical) Sorbents
•	Certain active ingredients can kill
pathogens
•	Low environmental impact
•	Enhances efficacies of burial, landfill, and
incineration
•	Moderately safe for operators
•	Chemical neutralizers, if present, can negatively
impact rendering and composting
•	High cost
•	Several of these additives do not inactivate infectious
agents
Encapsulation
•	Both mobile and on-site treatment facilities
are available
•	Properly encased (stabilized and
unbreached) material can prevent disease
spread during transport
•	Pathogen inactivation possible through
lime/alkaline treatment
•	High cost per carcass
•	Low throughput
•	No significant pathogen inactivation
Packaging
•	Mobile and on site packaging are
available
•	Low environmental impact
•	Moderate throughput capability
•	Few safety issues for operators
•	Moderate cost per carcass
•	Unwrapping of carcasses may be needed prior to
certain disposal procedures
•	If not sealed properly, there might be potential for
leakage
•	It aids the transport and handling, however, it does
not reduce the infectivity
Conclusions
Each of the potential pretreatment methods was defined and evaluated based on
present status and potential applications, advantages and disadvantages, scale of
operations, environmental effects, availability from vendors and typical cost range. The
evaluation revealed that many pretreatment options are available, and research studies
are ongoing to evaluate the effectiveness of these methods and technologies to
pretreat carcasses and the impact of these treatments on the air, soil, and water
systems.
Based on identification and evaluation, Table 2 provides a qualitative ranking of eleven
pretreatment alternatives to foster proactive protection, response, and recovery to
dispose animal carcasses in the event of animal disease outbreak. Each of the eleven
pretreatment options offers unique advantages and disadvantages. None of these
treatments, individually or in combination, should be considered absolute. The
pretreatment scheme should be approached on a case by case basis. Two or more
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pretreatment/disposal methods can be selected so as not to overburden a processing
site. Parallel treatment schemes can be considered by using treatment of part of the
feed material by selected methods while treating remaining parts of the feed material
by other method(s). Table 3 highlights key attributes of each of these technologies.
Table 2. Carcass Pretreatment Options Matrix
Disposal
Option
On-site Size
Reduction
Digestion
Bioreduction
Alkaline
Hydrolysis
Sterilization
Freezing
Physical
Inactivation
Chemical
Inactivation
Additives/
Sorbents
Encapsulation
Packaging
Rendering
+++
++
++
-
++
++
++
++
++
-
-
Incineration
+++
+
+
-
+++
++
++
++
+++
+
++
Composting
+++
+++
+++
-
-
++
++
-
+++
-
-
Burial
++
+
-
+
+++
++
++
++
+++
++
++
Burning
+++
-
-
-
+++
-
++
++
+++
+
++
Landfill
++
+
-
+
+++
++
++
++
+++
++
++
Note: Several of the pretreatments may have overlapping processes. Some of the activities can be
conducted at centralized or mobile locations. +++, ++ and + denote qualitative importance of the criteria
(+++ > ++ > +), and - indicate not applicable.
Color Key
Subject to acceptability of
Ideal	characteristics of feedstock	Not Suitable
by the processing facility/plant
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Table 3. Favorable Applications of the Pretreatment Options
Pretreatment
Options
Favorable Applications
On-site Size
Reduction
Grind carcasses to reduce size for transport and to use in subsequent processes
such as composting, rendering, and digestion; high throughput applications.
Alkaline Hydrolysis
Destroys prions; reduces waste volume and weight by as much as 97%.
However, it generates significant amount of liquid waste that require additional
treatment.
Steam Sterilization
Sterilizes for shredded mass.
Encapsulation
Safe handling; protection of the immediate environment (not during process of
wrapping).
Digestion
Reduce total volume under certain conditions and may take long time.
Additives/Sorbents
Enhance or accelerate disposal processes.
Bioreduction
Reduce total volume and some bacterial pathogens; dispose of animals overtime
without the need to transport off site; effective for small quantities of biomass.
Freezing
Delay decomposition; safe transportation; large capacity transport to disposal
site(s); decontamination of freezer may be necessary.
Inactivation
Eliminates most pathogenic microorganisms for safe transport and handling.
Packaging
Safe transportation to disposal site; safe handling.
Reference
U.S. EPA. 2016. Identification and screening of infectious carcass pretreatment alternatives.
Cincinnati, OH: U.S. Environmental Protection Agency. EPA/600/R-15/053
Contact Information
For more information, visit the EPA website (http://www2.epa.gov/homeland-security-research)
Technical Contact:
Sandip Chattopadhyay, Ph.D. (Chattopadhvav.sandip@epa.gov)
Paul Lemieux, Ph.D. (Lemieux.paul@epa.gov)
General Feedback/Questions: Kathv Nickel (nickel.kathv@epa.gov)
If you have difficulty accessing this PDF document, please contact Kathy Nickel
(Nickel.Kathv@epa.gov) or Amelia McCall (McCall.Amelia@epa.gov) for assistance.
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11
August 2016
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