Published on July 8, 2015
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
15. What if you need to go Large Scale? – dumpsters, trucks, or larger chambers or pits
16. Turnkey vaporizer for large scale use of CO2 $$$$ - $120,000 + trailer? 60 Kw generator - $25,000 +
17. 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
18. CO2 vapor collection reservoir (Ag-Bag)
19. CO2 vapor collection reservoir (Ag-Bag)
20. Assembly Guide: Mass Swine Depopulation System Utilizing Carbon Dioxide
21. System Schematic (Details provide in subsequent slides)
22. 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
23. 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
24. 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
25. 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.
26. 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
27. 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.
28. 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.
29. Venturi with common parts Two 6”x4” PVC reducers with standard PVC pipe sections….
30. Reading the differential pressure in inches of water (H2O)
31. 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
32. 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.
33. 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
34. 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
35. 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.
36. Jobs, Innovation, Growth, Stability www.ies.ncsu.edu Planning Tools for Mass Depop Events David Cornejo Ph.D. Candidate in Operations Research
37. 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
38. 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
39. 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
40. 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
41. 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
42. 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
43. 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
44. Computer Animation of process 50
45. Computer Animation(2) 51
46. 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
47. Jobs, Innovation, Growth, Stability www.ies.ncsu.edu Planning Tools using Simulation 53
48. 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
49. Web App Screen Shot 55
50. Web App (1) 56
51. Web App(2) 57
52. Web App Output Page 58
53. 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
54. The information and tools will be available online in the near future. If you have questions; please contact me. Mark Rice Email: [email protected] Phone: 919-515-6794 60