CASE STUDY -- Methyl Bromide Alternative
Use of Controlled Atmosphere Treatment for Commodities
In an effort to increase the shelf life of commodities as well as to reduce the number and quantity of chemicals used to treat commodities for control of insect pests and pathogens, the Department of Defense (DoD), in cooperation with commodity experts from American President Lines, TransFRESH, and the University of California, has developed an improved controlled atmosphere technique for transporting perishable commodities overseas.
Recent technological advances have resulted in the development of modified and controlled atmosphere sea transport shipping containers used by commercial exporters to extend commodity shelf life and to kill insects and other pests. Increased use of this technology has been driven by new innovations and developments that have allowed transporters to maintain extremely low O2 and ethylene concentrations resulting in both decreased commodity decay rates and control of pests (Gay 1995a).
Benefits of Controlled Atmosphere Treatments of Commodities
- reduces or eliminates insect and
- extends commodity market life
- allows use of more economical surface
transport for shipped commodities
Adoption of Controlled Atmosphere Technology
Industry experts believe that controlled atmosphere technology may revolutionize overseas commodity transport. The technology is appealing to transporters for several reasons:
- transporters consistently attain excellent results by utilizing this technology to reduce or eliminate insect and pathogen damage and to maintain fresh produce quality longer;
- transporters are able to ship perishable commodities to nearly all locations in the world;
- the technology has resulted in substantial economic savings for the government because the use of controlled atmosphere containers has allowed DoD to switch from air to surface transport. In 1993, estimated annual cost savings for DoD totalled $2.9 million (Gay 1995a);
- commodity tolerances are predictable; mathematical modelling and commercial trials have resulted in the development of prescribed atmospheres for specific commodity transport and insect control needs (Gay 1995a, Dangyang et al. 1991, Potter et al. 1994);
- research by academia, the military, and the private sector is expected to lead to efficient methods to achieve insect control that will satisfy strict international quarantine regulations (Gay 1995a, Mueller 1994, Delate and Brecht 1989).
Controlled atmosphere technology works by reducing produce respiration, slowing ethylene production, inhibiting pathogen reproduction, and killing insects. The greatest impact on insects is achieved by maintaining low O2 concentrations for an extended period of time which leads to oxygen deprivation in insect body tissues. At exposure concentrations of 0.5 percent O2 for 96 hours, 100 percent mortality has been observed for nearly all insects tested (Gay 1995a). Graphs of atmospheric gas concentrations and arrival condition reports have been used by DoD to monitor commodity arrival conditions. DoD ships between 200,000 to 1,000,000 pounds of commodities in 160 to 240 container vans per month to overseas consumers in the Pacific Rim (Gay 1995a). To date, with the use of controlled atmosphere containers, DoD has realized a success rate of over 95% for the arrival of marketable produce (DSR PAC 1993). By comparison, DOD realized a 70 percent success rate when methyl bromide and air transport was used.
DoD has used controlled atmosphere technology to control a variety of economically important pest species including thrips, aphids, and beetles infesting commodities such as vegetables, fruits, and farinaceous products (e.g., starch, flour, dog food) (DSR PAC 1993). Controlled atmosphere treatments are most effective at preserving commodity quality while controlling insect populations when produce is not exhibiting any signs of senescence or damage from handling; field packing, purchase of physiologically younger commodities and installation of ripening rooms may reduce difficulties using controlled atmosphere treatments on some produce (DSR PAC 1993). Some commodities such as papaya, Asian pears and nectarines may be injured or develop flavor changes due to exposures of 0 to 0.25 percent oxygen for three to fourteen days (DSR PAC 1993). These commodities may be successfully shipped with further refinement of the controlled atmosphere treatment. Commodities with short shelf lives (e.g., rasberries, blackberries, blueberries) are also more difficult to ship (Gay 1995b).
Increase the Shelf Life of Valuable Commodities
Although controlled atmosphere technologies require capital investments in the hardware required for modifying container vans, DoD experience indicates that the benefits of these investments far outweigh the costs (DSR PAC 1993). Estimated costs for application of controlled atmosphere technology are presented in the Table below. Generally, controlled atmosphere containers cost approximately $1,000 more than conventionally used refrigerated containers, but costs vary according to factors such as the number of containers shipped (Gay 1995b).
If controlled atmosphere treatment becomes an approved quarantine treatment, shippers will quickly recover their investment as expensive methyl bromide treatments will no longer be required. An additional advantage associated with adoption of controlled atmosphere technology is that methyl bromide can often damage, destroy, or shorten the shelf life of perishable products. Therefore, the risks associated with inventory shrinkage caused by fumigation can partially offset the costs of using controlled atmosphere technology (Murphy 1995).
Another cost advantage is that controlled atmosphere treatments enable produce to be shipped using surface transport where before airlift transport was required (Gay 1995b). Because of the use of surface transport, DoD has reduced transport costs from $1.25 to $0.43 per pound, resulting in annual savings of nearly $5 million (Gay 1995a).
Potential Quarantine Treatment Technology
By performing a disinfestation treatment, using the controlled atmosphere technology to maintain the oxygen level at 0.1 percent and the carbon dioxide at a level determined suitable for each specific commodity for 96 hours, insects are eliminated from treated shipments prior to transport (Gay 1995b). After a disinfestation treatment, the majority of controlled atmosphere shipments do not require methyl bromide fumigation for quarantine control of pests (Gay 1995b). However, controlled atmosphere disinfestation treatments are not currently recognized by the Animal and Plant Health Inspection Service (APHIS) as a quarantine treatment, and if quarantinable pests are found on the shipment, fumigation with methyl bromide is then required for quarantine purposes (Gay 1995b). Industry, government, and academic partnerships are currently compiling data on pest control efficacy required to secure quarantine approval. If successful, controlled atmosphere technologies may become an important quarantine treatment technology for the future.
Estimated Costs of Controlled Atmosphere Shipments
Conventional refrigerated container: $4,000/container
Controlled Atmosphere container: $5,000/container
Transportation cost (air): $1.25/lb
Transportation cost (surface): $0.43/lb
Methyl bromide fumigation
(if insects are present in the shipment, fumigation may be required for either refrigerated or controlled atmosphere containers): $500/container
Sources: Gay 1995a, Gay 1995b, Murphy 1995.
Dangyang et al. 1991 (March). Physiology and prediction of fruit tolerance to low-oxygen atmospheres. Ke Dangyang, L. Rogdriguez-Sinobas and A. Kader. Journal of the American Society for Horticultural Science. Volume 116. Number 2. American Society for Horticultural Science. Alexandria, Virginia.
Delate and Brecht. 1989. Quality of tropical sweet potatoes exposed to controlled-atmosphere treatments for postharvest insect control. Kathleen Delate and Jeffrey Brecht. Journal of the American Society for Horticultural Science. Volume 114. Number 6. American Society for Horticultural Science. Alexandria, Virginia.
DSR PAC. 1993. Pacific surface initiative and produce shipment losses to Guam. Defense Logistics Agency, Department of Defense. Alameda, California.
Gay. 1995a (January 5 and 30). Personal communication. Lieutenant Commander Gay. LCDR, MSC, USN, Staff Entomologist, Quality Assurance Division, Directorate of Subsistence. Alameda, California.
Gay. 1995b (April 18 and 24). Personal communication. Lieutenant Commander Gay. LCDR, MSC, USN, Staff Entomologist, Quality Assurance Division, Directorate of Subsistence. Alameda, California.
Murphy. 1995 (April). Personal communication. Kevin Murphy, Transfresh. California.
Mueller. 1994 (December). Personal communication. David Mueller, Fumigation Services and Supply. Indianapolis, Indiana.
Potter et al. 1994 (October). Controlled atmospheres for the postharvest disinfestation of Thrips obscuratus (Thysanoptera: Thripidae). M. Potter, A. Carpenter, A. Stocker, and S. Wright. Journal of Economic Entomology. The Entomological Society of America. Volume 87. Number 5.
Please note that this publication discusses specific proprietary products and pest control methods. Some of these alternatives are now commercially available, while others are in an advanced stage of development. In all cases, the information presented does not constitute a recommendation or an endorsement of these products or methods by the Environmental Protection Agency (EPA) or other involved parties. Neither should the absence of an item or pest control method necessarily be interpreted as EPA disapproval.
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