Academic journal article Journal of Sustainable Development

Mass-Heater Supplemented Greenhouse Dryer for Post-Harvest Preservation in Developing Countries

Academic journal article Journal of Sustainable Development

Mass-Heater Supplemented Greenhouse Dryer for Post-Harvest Preservation in Developing Countries

Article excerpt


A mass-heater supplemented greenhouse dryer is shown to be an adaptable technology to post-harvest preservation problems in developing countries. Inadequate harvest preservation in these countries often leads to a cycle of bumper harvest and production cutbacks, famine, inability of famers to get their harvest to the market, low quality of exports, and low agro-processing. Drying is a preservation technique that is readily adaptable for developing countries, and the earliest form of this method, open air drying, is still predominant. Rigorous designs are not always possible or economical, but the greenhouse dryer will always outperform open air drying irrespective of the quality of its design. Greenhouse dryer design parameters are identified, and guidelines for optimizing performance are provided. Mass-heaters based on rocket or top-lit-up-draftheaters, fueled by agricultural wastes, are proposed as supplementary heat sources when the sun is not available at night or during cloudy periods.

Keywords: greenhouse dryer, mass-heaters, preservation methods, solar energy

(ProQuest: ... denotes formulae omitted.)

1. Introduction

Agricultural products are seasonal, and it is not always possible to consume, sell, or process all products at each harvest. For food, the produce is often available in excess of local demands during harvest times but is in short supply between harvests because of inadequate preservation methods. As a consequence, famine between harvests is a common problem in developing countries.

Further evidence of poor preservation methods is the low quality of export produce from developing countries. It is a major challenge to meet the more stringent quality demands of the export market. In most of these countries, the poor transportation system creates significant delays on getting the produce to market. Such delays invariably degrade the quality of agricultural products that are not properly preserved and limit their acceptability in the export market.

A recent study by the Food and Agricultural Organization (FAO) of the United Nations (Gustavsson et al., 2011) reported that the per capita food loss in Sub-Sahara African and South/Southeast Asia is 120-170 kg/year while the production per capita is about 460 kg/year (Figure 1). About 35% of the food production is wasted, and the bulk of this waste is between production and retailing, mainly at post-harvest. The corresponding losses per production are about twice that of industrialized countries where the per capita production of food is about 900 kg/year. The study corroborates earlier data (Aidoo, 1993) which estimated that losses in rice, maize, wheat, barley, millets, sorghum, legumes and non-grain staples, vegetables, and fruits range from 5 to 60%. To avoid spoilage and total loss, farmers in developing countries are forced to sell their produce at a very low price shortly after harvest. Such losses in one season are always followed by cutbacks in production in the next planting season. Loss-preventive cutbacks can sometimes be extreme and can lead to inadequate production in seasons that follow bumper harvests.

Any steady agro-processing rate requires some level of raw inventory as a cushion against inevitable fluctuations in raw material supplies or raw material prices or production disruptions. Hence, processing of local harvests is also low or non-existent in developing countries because the harvests cannot be adequately preserved as sources of raw materials for control of production inventory.

It follows from the above that post-harvest preservation of agricultural produce must be promoted to ensure food availability, high quality of exports, and sustainable agro-processing. Options for harvest preservation include drying, canning, pickling, and refrigeration, but drying is the most appropriate and flexible technology for developing countries. Among the drying techniques, solar drying is the cheapest. …

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