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Mango Drying for Export Income
Solar Dryers make the difference between waste and value of surplus mango-fruits in Uganda. They create new possible exports to Europe.
By Youssef Arfaoui, Forum for Energy and Development, INFORSE, Denmark
Good Export Income with a Good Solar Dryer
Fruits and vegetables are abundant in Uganda. They can provide farmers with a good income, with the right processing. They can be dried using a solar dryer, then transported and sold in the big cities, exported, or saved to be used during the dry season’s food shortages.
Solar Dryers Developed from Local Materials
Solar drying is well known in Uganda, but the drying techniques are unsafe and inefficient. The solar drying is done in the old traditional way by spreading the fruits/vegetables on a carpet /sheet and exposed to the sun in free air. The food is exposed to various risks, such as termites, ants, birds, chickens, and dust. Drying takes a long time.
MS - Uganda (Danish Association for International Cooperation), together with Hoima Nursery Schools Development Association (HNSDA), Gukvatamanzi Farmers’ Association and its other partners in Uganda, has introduced locally made solar dryers to small-scale and community-based farmers to help them to create income. The solar dryers are now produced by HNSDA. The solar dryer that has been developed has been proven to dry mango fruits efficiently.
Mango trees are abundant in many parts of Uganda, but the fruits are not seen as important by rural communities. Due to the poor keeping qualities of the fruits, the long distance to big cities, and the conditions of roads, it was impossible for the farmers to make use of the mango as a source of income. Very often it is also not possible to use all the fruits for private consumption.
The dried fruits processed in the dryers have been tested and exported to the UK. It is now known that they have a big market in the UK and all over Europe.
After the introduction of the dried mangoes to the UK, the farmer groups could not meet the increased demand of a UK-based importer and still guarantee the same high quality. Presently, a small-scale export trade has been established. The dried fruit is now produced and exported from Kampala by several farmer groups like the Gukwatamanzi Farmers Association, which has 60 members, the Christian Rural Services of Nebbi West Nile, which has 40 members; and the Uganda National Farmers’ Association.
Affordable Price for a Solar Dryer Makes a Difference
Low prices, affordable for the small farmers and community groups, have helped the use of solar dryers to increase considerably in the last few years. The dryers are now used by a number of farmers to produce cash-crops. The second-quality selection of the dried fruit, which can not be exported, can be stored for later private consumption. School children are also able to have dried fruit as part of their lunches during the school hours. A large number of fruits and vegetables can be dried, including peas, corn, cabbage, broccoli, peppers, herbs, melon, plums, beets, onions, squash, tomatoes, asparagus, celery, bananas, and, of course, mangoes.
The use of solar dryers is still not widespread in Uganda. They have to be introduced to all parts of the country, especially to community-based farmers/groups.
Problems for Uganda’s Farmers
Uganda’s favourable soil conditions and climate have contributed to the country’s agricultural success. Technological improvements have been delayed by economic stagnation, and agriculture still uses mainly unimproved methods of production on small, widely scattered farms, with low levels of capital outlay.
Other problems facing farmers include the disrepair of the nation’s roads, the nearly destroyed marketing system, increasing inflation, and low producer prices. These factors contribute to low volumes of export of the traditional cash crops, as well as to a decline in per-capita food production and consumption. The production of the cash crops cotton, tea, and tobacco virtually collapsed during the late 1970s and early 1980s. In the late 1980s, the government encouraged diversification in commercial agriculture that would lead to a variety of non-traditional exports.
Despite serious problems, agriculture continues to be a significant source of income. Roughly 20 % of regular wage earners work in commercial agricultural enterprises. An additional 60 % of the work force earns some income from farming. Agricultural output is generated by about 2.2 million small-scale farmers with an average of 2.5 hectares of land each.
Fruits like mango, bananas, pineapple, oranges/ clementines and other crops, such as peanuts, tomato, pepper, and squash, are very common in the country. All can be dried to generate income.
The Basic Design
The fruit dryer is designed from basic material found in the community and is constructed by local craftsmen.
The sun shines through the clear glazing onto the fruit, heating up the air space under the glazing. The distance between the shelves provides air spaces under the screen in which the warm, moist air can move. The air moves passively upward along the slope, carrying away the moisture from the trays of fruits.

The dryer consists of:
1-Wooden frame, constructed as a box with shelf for the fruit trays.
2-Trays, wooden frame with chicken net of plastic materials, which allow the air circulation.
3-Transparent plastic (acrylic glazing), used as glazing, keeping and increasing the heat capacity.
4-Used oil around the dryer’s legs to protect the wood from being eaten by termites and to prevent access of ants and termites to the fruits.

Deluxe Super Solar Dryer
Using a PV-powered vent
A solar-powered fan is built into the dryer, so as to provide a steady, gentle air flow in a small food dehydrator. This style lends itself to very large units. This type of solar dryer has been tested by the research unit of The Ministry of Health -Health Technology Development Centre (HTDC), Kampala.
Youssef Arfaoui , more information
Youssef Arfaoui received his M.Sc. in Mechanical Engineering in Denmark in 1990.
Youssef has been a Project Consultant at the Forum for Energy and Development (FED), Denmark, since January, 2000. He has prepared renewable-energy training materials/programs for FED and for INFORSE members, e.g., in Grenada, Ethiopia, Somalia, Nepal, and Tanzania. He speaks Danish, Arab, French, English, and some German.
Between 1996-99 he was MS energy advisor at the Engineering Unit of the Ministry of Health in Uganda. Between 1984-96 he had a wide range of construction-engineering and teaching experience in Denmark.

Photo texts:
- Local fruit market in a village in Uganda. Photo by Youssef Arfaoui.
- The new solar dryers just arrived. It opens up export opportunities in the community in Uganda. Photo by Youssef Arfaoui.

More information:
- MS Uganda, 54 B, Kira Road,
PO Box 6331, Kampala, Uganda.
Ph:+256 41530764, fax +256 41530765
- On the Delux dryer: HTDC,
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