Should We Use Plastic Bins?
Until last year, plastic bins were not available in the United States. This has changed. Plastic bins were shown at the 1992 Washington Tree Fruit Postharvest Conference in Yakima. During a presentation at the Postharvest Conference, Alan F. Hauff (1992) explored the use of collapsible plastic bins that could be used not only for storage but also for shipping of fruit to local markets. In his study, Hauff did extensive marketing research and a comparison of standard wood bins to plastic bins. He interviewed researchers, manufacturers and other industry representatives to arrive at strengths and weaknesses of different types of bin designs and different materials used.
Hauff concluded the major advantages of rigid wood bins are low cost, superior strength, and having been the industry standard since 1957. Wood bin kits are produced and assembled locally which minimizes transportation cost from manufacturer to users. Wood bins also have disadvantages. They are subject to weathering, resulting in rough surfaces that can harbor various disease-causing organisms. They absorb moisture and chemicals. Wooden bins with solid plywood construction allow minimum ventilation. They cannot be recycled, and old ones must be discarded.
Plastic bins have several advantages. They have smooth surfaces that do not absorb moisture or chemicals. They are easy to clean and sanitize, do not harbor disease organisms, and are resistant to weathering. They have an interlock system that provides easier and safer stacking. Plastic can be recycled and has a longer life.
However, plastic bins have a substantially higher initial cost than wooden bins. They are slippery when wet, thus requiring more careful handling.
Western Fruit Grower, June 1992, featured an article on the use of plastic bins by Fowler Packing Co., Fowler, California. This past season they were handling soft fruit in plastic fruit bins manufactured by Macro Plastics, Fairfield, CA. Comments by users indicated that there was less bruising and less surface scuffing and that they liked the smooth bin surfaces which are easier to clean than wooden bins.
As the use of postharvest chemicals is reduced or eliminated, it will become more difficult to combat postharvest diseases. Sanitation will become more important and plastic bins will make sanitation easier.
History of Plastic Bins
Outside dimensions of the bins used in Italy are 1120 mm x 1120 mm x 770 mm (44 in x 44 in x 30.4 in). These dimensions have not changed since introduction of the plastic bin. Improvements in design and manufacturing techniques have increased the inside volume from about 600 to 700 liters which increased the bin capacity from 300 kg to 330 kg of apples (660 lbs to 730 lbs). The new bins are made of a solid polyethylene plastic, which is stronger than the foam plastic. The walls are thinner and inside dimensions larger, but the weight is still only 33 kg (73 lbs). These bins are stronger and more resistant to impact. Breakage has decreased dramatically.
In Switzerland, a plastic manufacturing firm, George Utz, AG, began producing plastic bins in 1980. Switzerland has a standard that requires the bin dimensions to be 1000 mm x 1200 mm x 765 mm high (39.3 in x 47.2 in x 30.1 in). The plastic bins produced by Utz have an inside volume of 650 liters which holds 315 kg of apples (695 lbs). They are made of high density polyethylene plastic, are heavy duty and weigh 42 kilograms (92 lbs). To reduce cost and weight, Utz is now manufacturing a model with thinner walls. The largest plastic bin manufacturer is Capp-Plast located in Capalle, near Florence, Italy. The Capp-Plast bins are used mostly in Italian tree fruit production areas other than the Bolzano region.
I recently toured the major tree fruit region in Europe where plastic bins are commonly used. I talked with researchers and warehouse managers about their experiences with changing to plastic bins and the use of plastic bins in general. The goals of this tour were to:
- Visit plastic bin manufacturers and become familiar with their products.
- Visit commercial storages that are using only wooden bins, only plastic bins and those using both kinds to discover advantages and disadvantages of both, reasons for changing from wood to plastic, or reasons to stay with wooden bins.
- Obtain information from researchers and extension personnel about the use of plastic bins.
I visited three manufacturers: Utz AG, Bremgarten, Switzerland; Palbox, Egna (Bolzano), Italy; and Capp-Plast, Capalle (Florence) Italy.
I visited two small storages in Switzerland and the Swiss Federal Research Station in Wadenswil. In Italy, I visited several storages in the Bolzano area, also the Laimburg Research Station and the extension office in Terlan (Bolzano).
Considerations and Issues Regarding the Use of Plastic Bins
Two small storages in Switzerland, each with 4,000-5,000 bin capacity, are using some plastic bins. One storage uses lower height plastic bins for pears. The other warehouse would switch to plastic bins if the price difference were smaller. A larger storage in the southern section of Switzerland used only plastic bins because plastic bins are lighter and they can haul more fruit per truckload, thereby reducing transportation costs.
Higher purchase price for plastic bins was a concern for most bin users. The highest prices were found in Switzerland where the heavy duty bin cost was 250 Swiss Francs (US $200). This bin weighs 96 pounds. A lighter version weighs 77 pounds and costs 150 SFr. (US $120). These bins also have 10 percent less capacity than the ones used in Italy. Wood bins cost 100 SFr. (US $80). In Italy the plastic bins cost 70,000 Lire (US $67), and wood bins are available for 40,000 Lire (US $38). Due to an improved design, the capacity of the new Italian plastic bins is only slightly less than that of wood bins.
Why Are They Switching to Plastic Bins?
- Plastic bins are 30-40 lbs. lighter than wood bins. Less bin weight reduces tare weight, thus increasing the amount of fruit that can be transported on a truck. Lighter bins are also easier to handle or move by the pickers, for example, when moving bins into the shade before filling.
- Plastic bins all weigh the same. In the production areas visited, the growers are usually paid for the grade and weight of the fruit brought to the warehouse. By knowing the tare weight of the bins, it was easy to determine the actual weight of the fruit delivered to the warehouse. In the US, growers are paid for the grade and amount of fruit packed, therefore, this would not be important in this country. However, some of the warehouses do weigh the bins before going into storage and again upon removal at the end of the storage season. Having bins that do not absorb moisture in storage would offer the opportunity to determine the exact weight loss of the fruit in storage.
- The new solid polyethylene bin has excellent strength and will maintain its strength over its useful life. Better stability and interlocking allow the plastic bins to be stacked up to 13 bins high.
- Better sanitation is possible because plastic bins have smooth surfaces that do not harbor disease-carrying organisms. They do not weather, crack, splinter, warp or become rough with age. They resist ultraviolet light. They can be cleaned more easily and the smooth surfaces cause less bruising or scuffing of the fruit.
- Plastic bins do not absorb water or chemicals. Rapid absorption of moisture by dry wooden bins during the early storage season (Waelti et al., 1989) reduces the relative humidity of the storage air which causes more weight loss of the stored fruit.
- Plastic bins have slots in the floor and sides of bins amounting to 7-11% of the total surface area. Plywood bins have only about 1.5% open area, which greatly limits the amount of air flow through the bins. Cooling air can circulate through plastic bins and around the fruit, greatly increasing the cooling rate. Tests conducted by Patchen et al. (1962) indicate that bins with 8-10% open area cool fruit twice as fast as plywood bins with limited ventilation. Similar findings were obtained by Bartsch et al. (1984) and Waelti et al. (1992). Increased air flow through the bins results in more even cooling and reduces temperature gradients and temperature differences between various locations in a room. With better ventilated bins, the rows could be stacked close together and still have sufficient cooling air flow through the stacks. Thus, in most rooms, one more row could be added, significantly increasing the room capacity.
- Plastic bins are either in good condition or not usable. Therefore, bins that are weak and may damage fruit or cause problems with stacking cannot be used.
Disadvantages of Plastic Bins
- They hold less fruit per bin because side walls and floor are thicker due to reinforcing ribbing. This was a significant disadvantage with the older designs when foam plastic was used. The newer bins made with solid polyethylene have thinner walls and hold almost as much fruit as wood bins of the same outside dimensions.
- Plastic bins are slippery, especially when wet, thus may slide on the forks when going around corners. It takes time for forklift drivers to get used to plastic bins. The forks must be set out as far as possible so that the bins cannot slide sideways.
- Plastic bins are more expensive to buy, but they have a longer life. Plastic bins can be recycled. By trading in three old bins, it is possible to receive one new bin. When considering a longer life and a salvage value of 33.3%, the actual long-term cost of plastic bins is not much different from wooden bins.
As plastic bins become available in the United States, they will be used first by more progressive warehouses and their merits, advantages and disadvantages evaluated. Issues such as sanitation, quality and environmental concerns will be major driving forces. Change will be slow. For example, the State of Washington holds about 3,400 million pounds of apples in cold storage (Wash. Agric. Statistics, 1988). To store this crop requires 4.5 million bins. To replace only 1% of these bins per year would require a yearly production and distribution of 45,000 bins.
Patchen, Glenn O. and G. F. Sainsbury. 1962. Cooling apples in pallet boxes. Marketing Research Report No. 532. Agricultural Marketing Service, U.S. Department of Agriculture, U.S. Government Printing Office.
Bartsch, J. A. and G. D. Blanpied. 1984. Cooling rates of apples in tight and spaced stacking patterns. Staff Report No. 84-3, Agricultural Engineering Department, Cornell University, Ithaca, NY.
Washington Agricultural Statistics, 1987-88. 1988. Washington Agricultural Statistics Service, 417 West 4th Avenue, Olympia, WA 98501.
Waelti, Henry, R. P. Cavalieri and K. R. Zaugg. 1989. Reduced evaporator fan operation; effect on storage environment. Paper No. 89-1636 presented at the 1989 International Winter Meeting, American Society of Agricultural Engineers, New Orleans, LA (Dec. 12-15, 1989).
Waelti, Henry, M. Johnson and R. P. Cavalieri. 1992. Energy conservation, cooling rate and storage environment in fan-cycled rooms. Paper No.PNW92-113, presented at the Pacific Northwest Section, American Society-Canadian Society of Agricultural Engineers 47th Annual Meeting, Bozeman, MT (Sept. 16-18,1992).
Henry Waelti, Extension Agricultural Engineer
Washington State University, Pullman, WA
Tree Fruit Postharvest Journal 3(4):14-17