Purpose of Grain Storage

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Grain storage and handling is the process whereby grain is received, processed, stored and shipped off. Grain storage is an early step in the food value chain, acting as a facilitator between producers and feeders/processors by providing safe and secure storage of grain.

Facilities for grain storage and handling must be adequate to ensure that no component of the grains is depleted. Grain storage and handling facility includes grain receival, grain movement, grain cleaning, reclaim, storage and possibly drying and cleaning operations. This is a major investment and the whole system must be carefully planned.

Grain storage is a component in the grain marketing supply chain that evens out fluctuations in the supply of grain from one season, usually the harvest season to other seasons, and from one year of abundant supply and releasing to lean years. Grain storage may be at farm, trader or commercial. At the farm level, storage is normally inter-seasonal and helps the household to ensure food supplies for the farmer and the family, cash or barter exchange and for seed. At the trader level, grain storage is for a very limited time – over a period of few days or weeks. The traders buy and sell quickly to make a profit. Grain storage at this level is not inter-seasonal. Commercial storage is used by millers and cooperatives to hold stock for limited periods of time to meet demands for their needs or for their urban clients.

Post-harvest losses of cereal grains during storage account for 1-2% in well-managed systems and 20-30% in poorly managed systems. During harvest, the moisture content of grain is around 20-30%, and harvest temperature is 25-50˚C depending on the growing region of the world. This harvested moist and warm grain should be dried and cooled before storage. Moisture content and temperature are the main factors that determine the length of storage time for storing grains without spoilage.

Insects and moulds are the main predators during the storage of grains and the growth of these insects and micro-organisms increases dramatically when the relative humidity inside the grain bins rise above 70% and the temperature is above 25˚C. Prevention of insect and mould growth is a better option than the control measures, and if insect and mould growth couldn’t be controlled at an early stage, there is the potential for total damage to the grain.

The safe storage time of grains decreases with an increase in storage temperature and moisture content of grains. Temperature gradients inside the grain bin lead to moisture migration and when moisture from warmer areas migrate to colder areas condensation could occur in cool grain near the top of the bin or on bin ceiling or wall due to moist warm air coming in contact with the cool surfaces. If the ventilation of the bin is poor, the moist and warm air cannot be removed from the bin and can create favourable conditions for insect and mould growth.