A safe and clean way of reducing the rate at which farm produce deteriorate after harvest

Abstract

Most of the food crops harvested in Ghana during the growing season of that particular crop are abundant and so there is the need to device a means of storing the food to prevent them from deteriorating in order to prevent hunger and scarcity of crop after the growing season. In general, farmers have a problem in having their crops dried fast, efficiently, economically and environmentally well. Drying on the ground by the sun is recently the most used method. Most farmers cannot afford to import expensive mechanical drying equipment, which is either electricity or diesel engine driven, with the additional financial burden of maintenance, fuel, electricity and other running expenses. Apart from the environmental problems. Many more farmers will be able to increase their output if a relatively cheap solar dryer for crops is made available with the additional benefit of relatively low running expenses. The success of such equipment would depend upon the final cost of the solar dryer, each farmer’s financial situation, on the bank and the manufacturer, and in some cases, donor agencies would become some of the important aspects of farming. A very large proportion of the food products in developing countries like Ghana is destroyed before they are shipped to the market. Some food products are dried before they are shipped to the market some food products are still being put out on the ground and in the sun. This is however, a very slow method of drying and often take many days and also the products are not uniformly dried. Food products are exposed bacteria attack which may make them dangerous to consume. Crops are exposed to insects and fungus attack and polluted by dust. Based on preliminary investigations under controlled conditions of drying experiments, a natural convection solar dryer was designed and constructed to dry mango slices. These considerations helped in realizing the importance of designing and manufacturing after presenting the results of calculations of the design parameters. A minimum of 16.8m2 solar collector area is required to dry a batch of 100kg sliced mango (195.2kg fresh mango at 51.22% pulp) in 20hours (two days drying period). The initial and final moisture content considered  were 81.4% and 10% wet basis, respectively. The average ambient conditions are 30oC air temperature and 15% relative humidity with daily global solar radiation incident on horizontal surface of about 20MJ/m2/day. The weather conditions considered are of Khartoum, Sudan. A prototype of the dryer is so designed and constructed that has a maximum collector area of 1.03m2. This prototype dryer will be used in experimental drying tests under various loading conditions. [1] (Solar drying in Ghana final report Soren Ostergaard Jensen: Danish technological institute July 2002).