Many third world countries are turning to well-designed agricultural storage structures to address post harvesting losses, which threatens food security. Following is an overview of the types, design process and resources used in developing a farm-level storage structure in Kenya.
Post harvesting losses are one of the most widely discussed problems in African Agricultural systems. Practitioners in the field have taken up the role of addressing the losses by focusing on specific areas such as storage. For example, in the maize value chain in Kenya, people have come up with a wide range of storage options that have been subject to numerous research over the years
For effectiveness, agricultural storage structures have to be designed following an engineering design criteria. The process of designing a storage structure will start by gathering information on the type of crop one intends to store. Specific information that is relevant here includes the equilibrium moisture content of the crop during drying. The equilibrium moisture content is derived from the humidity and temperature of an area and describes the optimum moisture content under which grains can be stored.
Usually, the equilibrium moisture content values are used alongside storage temperatures to determine the allowable storage time for the crop. In that regard, for a given value of equilibrium moisture content of a grain obtained after drying, and stored at a given temperature, there is a finite number of days that the grains can remain stored without going bad. This information is captured in the allowable storage time for the specific grain under different conditions.
Another important piece of information when designing storage structures is the bulk density of the dried product and the type of material that one intends to use when constructing the structure. Common materials used include metals, wood and concrete, all of which have different structural properties that have to be considered when designing a structure. For reference purposes, Agricultural engineers use the Farm Structures Manual by FAO, which gives a detailed guide on how to construct rural structures.
Solar is one of the technologies that is slowly finding its way into grain storage in Kenya. The technology has improved from the traditional open sun drying approach to more advanced systems such as solar drying cribs. Again, these kinds of structures have to be designed and tested before full adoption. Important design considerations will include the amount of solar radiation in an area, the moisture content of the grain after harvesting and the load imposed by the grains during storage