1. Effects of modified atmospheres on insects with special reference to silo-bags
Prof. Shlomo Navarro
Green Storage Ltd. Israel
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

2. Navarro - Effects of MA on insects in silo-bags
Modified atmospheres and hermetic storage take advantage of the basic fact that
Storage insects are aerobic organisms requiring oxygen for their survival
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

3. Action of modified atmospheres on insects
1- Desiccation
2- Anoxia
3- Hypercarbia
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

4. Navarro - Effects of MA on insects in silo-bags
A moth larva with spiracles along the body
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

5. What is hermetic storage?
hermetic storage is a type of biogenerated MA
It consists of generation of an oxygen-depleted and carbon dioxide-enriched interstitial atmosphere by the respiration of the living organisms in the ecological system of a sealed storage.
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

6. Organisms that contribute to the generation of MAs
Insects and mites
Aerobic microflora
Anaerobic microflora
Seed germ
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

7. Aerobic fungi, seed germ
Bio-generation of MAs in relation to the atmospheric gas composition and the humidity of their environment
Aerobic conditions
High oxygen
Low carbon dioxide
Anaerobic conditions
Low oxygen
High carbon dioxide
<65% RH
Insects & mites
65 to 85% RH
Aerobic fungi, seed germ
>85% RH
Anaerobic bacteria
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

8. First challenge in MA and hermetic storage
Maintaining a well sealed storage structure
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

9. Navarro - Effects of MA on insects in silo-bags
Night
Day
Cooled air contracts
Heated air expands
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

10. Navarro - Effects of MA on insects in silo-bags
Atmospheric pressure
October 14, 2014
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11. At high atmospheric pressure At low atmospheric pressure
External atmosphere moves in
Inside atmosphere moves out
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

12. Parameters to determine GASTIGHTNESS of the structure
1- Leaks of the structure. Can be assessed using pressure test.
2- Permeability of the membrane, particularly in flexible structures. Should be measured in a laboratory.
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

13. Second challenge in MA and hermetic storage
Preventing permeation of oxygen through the flexible liners
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

14. Navarro - Effects of MA on insects in silo-bags
Oxygen permeability requirements [mL/(m2 24 h)] of liners in relation to various storage capacities (m3) and oxygen ingress rates (%/24 h) for successful application of hermetic storage of dry grain.
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

15. Third challenge in MA and hermetic storage
Absorption and adsorption of carbon dioxide by the commodity
A – Carbon dioxide distribution
B - Exposure period
C - Aeration period
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

16. Recommended ranges for variable pressure test carried out in structures destined for gaseous treatments to control storage insects.
<
Variable pressure test decay time (min) 250 to 125 Pa
Type of gaseous treatment
Structure volume in cubic meters
95% Full
Empty structure
<500 3 1 5 .
Fumigants
500 to 2,000 4 2
2,000 to 15,000 6 3
<500 6 3
Controlled atmospheres
500 to 2,000 7 4
2,000 to 15,000 1 1 6
<500 1 5
Modified atmospheres including airtight storage
500 to 2,000 1 2 6
2,000 to 15,000 1 8 9
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

17. Navarro - Effects of MA on insects in silo-bags
Phosphine loss from an empty structure of 7.5 m3 capacity in relation to half-life pressure decay time. Phosphine loss should not exceed 100 ppm/day. 25 50 75
100
125
150
175
200
225
250
PH3 loss (ppm/day) 1 2 3 4 5 6
Minutes for half-life pressure decay
Shaded
Exposed
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

18. Fourth challenge in MA and hermetic storage
Liner durability:
Insect damage
Rodent damage
Weather damage, mainly UV.
Mechanical damage
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

19. Navarro - Effects of MA on insects in silo-bags
Low O2 ingress level, is difficult to maintain in rigid structures, but is achievable in practice using flexible liners
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

20. Navarro - Effects of MA on insects in silo-bags
Measured CO2 concentration during storage time of three silo-bags with soybeans at 11.5%, 12.9% and 14.9% m.c. and average ambient temperature (adapted from Bartosik, 2008).
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

21. Navarro - Effects of MA on insects in silo-bags
Calculated O2 and CO2 concentration in silo-bags containing wheat of initial m.c. at 12, 14 and 16% w.b. for locations at Saenz Peסat Pergamino and Balcarce. Initial temperature 25oC (adapted from Baretto et al., 2012).
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

22. Application of BIOGENERATED atmospheres on dry cereal grain
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

23. The process of hermetic storage
Residual oxygen within the hermetic storage
Critical point
Insect respiration
Oxygen ingress rate 0.05 %/day
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

24. Navarro - Effects of MA on insects in silo-bags
Modified atmosphere generated by respiration of insects in hermetic storage (calculated theoretical). Based on grain mass containing different infestation levels of insects with an oxygen ingress raאe of O.24%/day.
October 14, 2014
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25. Navarro - Effects of MA on insects in silo-bags
Calculated weight-loss from a grain mass containing initial infestation of 2 insects/kg, at different oxygen ingress rates.
Target gas tightness level
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

26. Navarro - Effects of MA on insects in silo-bags
Target gas tightness to control storage insects in dry cereals, in hermetic storage structures
Daily oxygen ingress rate:
1- Below 0.05 % O2/day prevents oscillated oxygen concentration and increased weight loss.
2- Between 0.05 and 0.24 % O2/day allows oscillated oxygen concentration and increased weight loss.
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

27. Navarro - Effects of MA on insects in silo-bags
Conclusions
MA or hermetic storage are very promising quality preservation and insect control technologies.
There are a number of challenges in the application of MA or hermetic storage:
Maintaining a well sealed storage structure.
Preventing permeation of gas through the structural membrane (by improved liners).
Consider absorption and adsorption of carbon dioxide by the commodity.
In flexible storages improve liner durability; to insect damage; to rodent damage; to weather; and to mechanical damage.
For silo-bags daily oxygen ingress rate should be below 0.10 % O2/day.
For silo-bags oxygen permeability requirements of liners should be below 400 [mL/(m2 24 h)]
October 14, 2014
Navarro - Effects of MA on insects in silo-bags

28. Thank you for your attention !!! Silobags for sealed storage of grain
October 14, 2014
Navarro - Effects of MA on insects in silo-bags