Large amounts of the world's food grain are wasted because of inadequate handling and storage at various stages between production and consumption. If grain is stored in unsuitable and primitive ways, the storage losses (caused by germination, microbes, rodents, birds and insects) can be as much as 20 to 40% while at the same time the quality of the rest may be badly impaired. The problem is especially difficult in tropical developing countries where there the extremely high temperatures coupled with widely fluctuating humidity facilitate every type of wastage from insect infestation to mould growth. Even in developed countries, the growth of fungi in existing storage facilities gives rise to the production of substances toxic to man and to farm animals.
The variability of foodgrain losses from season to season, between different crops, from country to country and under different kinds of treatment, makes accurate measurement of their extent very difficult. Reasonable average estimate of wastage is at least 10% of the total grain production of the world, amounting to 75 million tons per year, or a calorie loss sufficient to supply the needs of 250 million people. Some estimated losses per crop year are: India, 25%; tropical Africa, 30%; USA, $500 million.
The most significant losses frequently occur towards the end of the storage season (when small scale farmers, at least, will be short of food) and tend to arise at the farm level when the traditional capability to conserve grain is disturbed with the introduction of new improved varieties or multiple cropping. The traditional handling, drying and storage systems may be inadequate to cope with the increased yield. Furthermore, the characteristics of the crop may be changed so that the grain is more susceptible to insect or fungal attack, or the timing of harvest may be changed from the usual dry season to the less favourable wet season.