Outdoor storage of grain in plastic enclosures in the humid tropics

• National Postharvest Institute for Research and Extension, Philippines

Between 1983 and 1988, ACIAR Project No. 8307 researched the use of sealed plastic enclosures for the storage of bagged grain. The result was a successful method for storing bag-stacked grain indoors. The system has now been adopted in Indonesia and Singapore for long-term storage of grain, and is being introduced into Australia by industries that store high-value grains and other commodities in bags. However, because long-term indoor storage is expensive, it is generally not attempted by smaller operators.
This new project, identified and requested by potential collaborators in the Philippines, has been set up to design and test a complementary outdoor storage method for grain. Because the outdoor environment can lead to severe problems, such as the movement of moisture in containers, it is not possible to use existing indoor methods outside the shelter of a permanent warehouse. Available methods for outside storage are applicable only to dry grain, the stores are usually of large size, and all are expensive or have high management requirements.
Smaller operators would benefit most from a suitable method of outdoor storage with low capital and running costs. Such a method would also give larger organisations flexibility to deal with, for example, peaks in commodity production and periods of low prices.
The project will be carried out by scientists from the Stored Grain Research Laboratory, CSIRO Division of Entomology, in conjunction with colleagues from the Philippines National Post Harvest Institute for Research and Extension (NAPHIRE). The collaborators aim to develop a storage container:
that is weather, rodent, and insect-proof;
that can be fumigated, and be suitable for use with controlled atmospheres;
in which moisture migration is controllable;
that will facilitate handling and allow little loss of grain during grain transfer; and
that is capable of storing damp grain and maintaining quality during holding periods before drying.
The CSIRO Division of Entomology is well qualified to lead these studies. As well as having played a major role in researching grain storage systems in Australia, the Division has extensive experience in collaborative activities in developing countries.
The Australian wheat industry in conjunction with CSIRO has successfully developed `bunker storage' for large-scale storage of dry bulk grains outdoors. The same general principles apply to the type of storage to be investigated in this proposal. The major difference is that environmental factors have a greater impact on smaller-scale storages and cause many more problems with commodities with a higher moisture content.
There are several solutions to the problems of outdoor storage, all with a high probability of technical success, but which are not necessarily economical. These include bunkers, air warehouses, flexible silos, underground sealed storage, the Capatainer system , and a number of bag-stack systems. This project will identify and develop a method that has the most appropriate balance of cost, manageability and reliability.
The work will be divided into three phases, each of around 1 year duration. Phase 1 will involve the design and assessment of prototype sealed enclosures, ventilated enclosures and flow-through enclosures. This will be done in Canberra, where the diurnal temperature range greatly exceeds that of the moist tropics. The scientists will apply models developed earlier for large-scale storages and refine them for the smaller storage requirements being investigated. Selected successful prototypes will then be field tested in the Philippines. During Phase 2, the most successful enclosures will be selected from the results of field trials and assessed in both Australia and the Philippines. The long-term field trials will continue into Phase 3, during which the selected system will be refined.
Postharvest research has a high national priority in the Philippines to ensure that the maximum amount of grain harvested is available for consumption. The Philippines and the whole ASEAN region will benefit from a low-cost outdoor storage system. This will have a significant economic impact throughout the grain industry by enabling greater turnover of grain and therefore profits for all operators, as well as cheaper and higher quality grain for consumers. In addition, once a system is developed and demonstrated, there is every chance that small local industries in developing countries will produce and market the plastic components as a profitable enterprise.