Planning for Emergency Mass-Depopulation of Swine in Response to a Foreign Animal Disease Outbreak - Mark Rice, North Carolina State University, from the 2015 World Pork Expo, June 3 - 5, 2015, Des Moines, IA, USA. More presentations at http://www.swinecast.com/2015-world-pork-expo

1. 1
Planning for an emergency
depopulation of swine in response
to a foreign animal disease outbreak
• WE Morgan Morrow, RE Meyer, JT Whitley, CS Whisnant,
• LF Stikeleather, CL Baird, JM Rice, BV Halbert, HS Byrne, JA
Lavin, D Cornejo, DK Styles
• Mississippi State University
• North Carolina State University
• USDA-APHIS Veterinary Services
• Department of Homeland Security
• Murphy Brown LLC

2. Outline
•Define the problem
•Propose a possible approach
•Introduce some planning tools
2

3. I am not here to convince you that I
have all the answers but rather to get
you to:
•Start thinking now about what you would
do if the situation arises
•Be prepared
•Every situation is different
3

4. What is Mass Depopulation?
As defined by the AVMA:
“methods by which large numbers of animals must
be destroyed quickly and efficiently with as much
consideration given to the welfare of the animals
as practicable, but where the circumstances and
tasks facing those doing the depopulation are
understood to be extenuating”
• Includes: disease outbreaks, contamination with
chemicals (eg, dioxin) or radionuclides (eg, cesium 137),
and situations severely limiting feed deliveries and animal
movement.

5. Why CO2?
• Readily available, low cost, nonflammable
• Anesthesia due to ↓pH
• Produces unconsciousness and kills over wide range of concentrations
• Exposure to 60% to 90% CO2 causes unconsciousness
in 14 to 30 seconds, with unconsciousness occurring
prior to onset of signs of excitation.
• Conc < 30% not aversive to pigs (Raj & Gregory 1995)
• AVMA- , AASV-approved for humane killing of swine
• Reversible should personnel be exposed

6. Our Objectives
Recognized the benefit of getting the pigs out of the
buildings
Easier to manage their disposal once outside
• Figure out how to do mass-depop in the field
• Focused on gassing
• Develop alternatives for:
• Containment….corrals
• low pressure CO2 (head space vs liquid)
• Gas containment….bladders

7. Our Objectives (cont.)
• Understand CO2/O2 dynamics in the
containers.
• Computer simulations/CFD analyses.
• How to deliver CO2, manifolds.
• Temperature, avoid freezing pigs
(evaporators/earth tubes).
• Time to 30% CO2 (non aversive).

8. Our Objectives (cont.)
• Time to loss of righting reflex (LORR)
unconsciousness.
• Time to death….cycle time is very important.
• Simulate cycles to better understand effects of
limiting inputs (labor, gas, containers, pig
movement).
• Generally to better understand the process and
develop alternatives.
The devil’s in the details!

9. Ideally…
•Equipment and supplies readily available
(Home Depot/Lowes) or stockpiled
ahead of time
•Well-documented methods
• Easy to apply by field personnel
•Scale-able to large numbers/throughput
• Efficiency benchmarked by time-motion
studies
•As humane as possible under the
circumstances

10. 10
CO2 Mass Depopulation
- What you need and how to do it.

11. When using CO2 for euthanizing
animals - size/scale does matter
•CO2 is generally delivered as a pressurized
liquid
•For low flow rates – draw off head space
gas
•For high flow rates – will require releasing
high pressure liquid – when liquid CO2 is
released approximately 54% is released as
a gas, the remaining (46%) forms dry ice
To meet AVMA recommendations – must replace chamber volume
within 5-minutes

12. Small scale - bleed directly from
CO2 pressurized cylinder into
chamber
For: nursery pigs and small chambers such as
hand carts or bins

13. Intermediate scale – bleed from a
high pressure CO2 cylinder to low
pressure tank
• Suitable for small trucks or dump trailers
• Liquid CO2 flow rate is low enough to avoid
line and regulator freeze up
• At low flow rate, CO2 gas in the low pressure
tank will approach ambient temperature
• Orifice is sized to control flow from the low
pressure tank to chamber

14. Low pressure CO2
tank
High pressure CO2 cylinder
Euthanasia Chamber
(Trailer)
CO2 pressure
regulator 1
1 Regulator would maintain preset pressure in the
low pressure tank between application events.
2 Relief pressure setting should be slightly above
required low pressure CO2 tank pressure but well
below the maximum tank pressure rating.
Safety
pressure
relief valve2
Orifice plate
Ball valve

17. What if you need to go Large Scale? –
dumpsters, trucks, or larger
chambers or pits

21. Turnkey vaporizer for large scale use
of CO2
$$$$ - $120,000 + trailer?
60 Kw generator - $25,000 +

22. Low-cost vaporizer system to capture and
sublimate dry ice produced during the
application of liquid CO2 and also temper gas
temperature
< $2,500 including heaters
3.5 kw generator – approximately $500

24. CO2 vapor collection reservoir
(Ag-Bag)

25. CO2 vapor collection reservoir
(Ag-Bag)

26. Assembly Guide:
Mass Swine Depopulation System
Utilizing Carbon Dioxide

27. System Schematic (Details provide in subsequent
slides)

28. Vaporizer Chamber – should be a gas tight
vessel capable of withstanding 500-600 degree
Fahrenheit and with a pressure relief valve
installed to prevent pressure buildup. We have
utilized 55-gallon metal drums as well as 250
and 500 gallon, used propane tanks

29. Heat Enclosure – designed to improve heat transfer to
the vaporizer chamber. It should be exhausted to
prevent excess backpressure on the heaters.
Concrete block can
be stacked without
mortar to create an
enclosure around
the vaporizer tank

30. The liquid CO2 connection is critical. Check with
your CO2 supplier to make sure you have the
correct connects available to enable their trucks
to connect to your system. A pressure drop valve
is necessary near the inlet of the tank to prevent
dry ice formation in the feed hose or truck valve.
Liquid CO2
connection
to truck
Needle valve
used to drop
the liquid CO2
pressure

31. Heat Exchanger – to prevent cold CO2 gas from being
introduced into the chamber the CO2 gas temperature sho
be increased to near ambient temperature. This can be
accomplished by adding a metal heat exchanger coil inside
the heat enclosure.

32. CO2 gas to
heat
exchanger
CO2 gas
by-pass
valve
valve
Valves can be adjusted to regulate the flow of CO2 gas
through the heat exchanger to provide the appropriate
CO2 gas temperature to the chamber.
Heat Exchanger Plumbing Diagram

33. CO2 Gas Accumulation (optional) – a gas
collect/temporary storage bladder will help provide a
more consistent flow of gas to the depopulation
chamber. Bladders can be constructed with plastic
sheeting by taping the seams or Ag Bag silage storage
bags by folding/clamping the ends.

34. Flow Regulation – To meet the AVMA requirement the
depopulation chamber volume must be filled over a 5-
minute period. A blower can be used to move the CO2
gas from the accumulation bag to the chamber. To
ensure proper flow rates, a field constructed venturi
and monometer can be assembled.

35. Venturi with common parts
Two 6”x4” PVC reducers with standard
PVC pipe sections….

36. Reading the differential pressure in
inches of water (H2O)

37. Flowrate of CO2 (0-60°F) as function
of Inches of water differential
pressure
0
1
2
3
4
5
6
7
8
100 200 300 400 500 600
InH2O
Cubic feet per min. (CFM) of CO2 when at 0 -60°F
Inches H2O vs. CO2 Flowrate @ 0-60°F with 6x4 PVC venturi
CFM of CO2 at 0F
CFM of CO2 at 60F

38. Depopulation Chamber – Sized to accommodate the
farm needs and the capabilities of the vaporizer unit.
Deliver CO2 to the floor of the chamber. Since CO2 is
heavier than air the lower part of the chamber must gas
tight. Earthen pits or sealed truck bodies could be
utilized as chambers.

39. The heat capacity and number of heaters will be
determined by the desired CO2 flow rate. Each
cubic foot of chamber capacity will require about
600 btu/hr heat capacity. Heat input can be
supplied from several sources but kerosene,
torpedo style heaters are readily available and
provide more consistent output than propane
fueled heaters.
Kerosene heaters
positioned into
openings in block
walls

40. Planning for Mass Depopulation
1) Decide on chamber size, i.e. trucks, corral, pit.
2) Determine volume of chamber (length x width x depth)
3) Determine required flow rate (volume/5 minutes)
4) Size components according to required flow rate. To
prevent dry ice accumulation and raise the temperature of
the CO2 gas to near ambient temperature, for each cubic
foot of chamber capacity will require approximately 600
btu/hour of heat capacity

41. Planning for Mass Depopulation
Example:
1) Decide to use a pit that is 10’ wide, 40’ long, and 3’ deep
2) Determine the volume: 10’ x 40’ x 3’ = 1,200 cu. ft.
3) Determine required CO2 gas flow rate: To fill the chamber
volume in 5 minutes: 1,200 cu.ft./5 min. = 240 cu. ft./min.
4) Heat requirement: 1,200 cubic feet chamber capacity x 600
btu/hr capacity = 720,000 btu/hour (If 125,000 btu/hr
heaters are available, it would require 6 of them.

42. Jobs, Innovation, Growth, Stability www.ies.ncsu.edu
Planning Tools for Mass Depop
Events
David Cornejo
Ph.D. Candidate in Operations Research

43. Goals
•Strategic(Before)
• Develop basic estimates of resource
requirements before disaster.
•Tactical(During)
• Assist in identifying resource savings/need
during event.
•Delivery via Web application
43

44. System Overview
•4 Distinct Stages
• Moving pigs from house to loading chute
• Loading pigs onto available trucks
• Preparing trucks and gas application
• Disposal of carcasses
•METRIC: Time to complete process.
44

45. Moving Pigs from house to truck
• Influenced by following user inputs
• Pigs: Number, Weight class
• Houses: Number, Size, Loading chute length
• Workers: Number available
• Variables affect Travel Time of run.
45

46. Load Truck
• Pigs Loaded onto truck
• Capacity of trucks from pig weight class
• Details
• One or more loading chutes available
46
Class Name Space Requirement(sq. ft./pig)
Nursing (<50lbs) 1.09
Weaning (50-100lbs) 2.635
Finishing (100+lbs) 3.48
Breeding Boar/Sows 5.55

47. Preparing Trucks for Gas
•Before each application of gas some
preparation (check tarp, attach hose etc.)
•Assumed to take between 5 and 10 mins
• May physically take place at gas location.
47

48. Administer Gas
•Correct Flow rate(20-30% of volume of
container/min) applied for minimum of 5
minutes.
•Applying gas consumes available stock.
• Process halted when no more gas
• Gas can be delivered on intervals.
• Sublimation a way to extend gas stock
48

49. Dispose of Carcasses
•“Dwell Time” of 10 minutes accounted
for in minimum travel time to Disposal
Site.
• Ability to travel immediately after gas
•Trucks take time to return to loading
chute
49

50. Computer Animation of process
50

51. Computer Animation(2)
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52. Parameters and Control Variables
• Farm Parameters
• Size of House
• Size of Pin
• Number/Length of Load Chutes
• Truck Controls
• Truck Size
• Number of Trucks
• Handler Controls
• Number of Handler
• Handler Efficiency
• Special Process Parameters
• Dry Ice recovery process option
52

53. Jobs, Innovation, Growth, Stability www.ies.ncsu.edu
Planning Tools using Simulation
53

54. Web App Solution
• Best resource solution form a large array of
scenarios batch run in simulation model.
• Results stored in database.
• Web application exposes relevant controls to
decision maker and calculates resource
requirements based on stored simulation
results.
• Web app runs fast (seconds) and requires no
specialized software.
54

55. Web App Screen Shot
55

56. Web App (1)
56

57. Web App(2)
57

58. Web App Output Page
58

59. Summary
• CO2 is a viable option
• Able to meet AVMA recommendations for
dump truck size chambers as well as
3’x12’x80’ pit using a storage bag to
accumulate CO2
• Progressively refining the process – working
through the obstacles
• Needed supplies can be purchased locally
• Minimal number of people involved
• Safe method

60. The information and tools will be
available online in the near future.
If you have questions; please contact me.
Mark Rice
Email: mark_rice@ncsu.edu
Phone: 919-515-6794
60