Construction and Use of a Simple Solar Drier to Preserve Food for Off-season

Table of Contents
Recommendations for construction: Recommended dimensions of a Drier: Why are we promoting a Drier: Use of dried crops: The link to household energy Related topics External links and references Contributors

Pictures and Instructions from IFSP, Malawi

1: construction under way with local material

2: similar technology to the driers for dishes

3: completed drier with greenhouse plastic

4: inside: sweet potato, cassava and vegetables

5: preserving vegetables and tomatoes

6: drying grated sweet potato and cassava

7: drying of banana chips

8: drying cassava: grated and in pieces

[top] [end]Recommendations for construction:

The construction of the Drier is based on a structure which is commonly used by Malawian households to dry their dishes after washing. Materials used in the construction vary by area in Malawi, depending on the offers of mother nature (e.g. bamboo, trees, palm trees, eucalyptus, elephant grass etc.). Starting from there, only small additions and modifications are required to build a suitable structure for drying crops.

The roof should be the same width as the greenhouse plastic, the table for the drying should be slightly smaller, so that rain runs off the plastic cover and does not enter the Drier from the side. Ideally the supports to the roof are fixed to the drying table. In order to fix the greenhouse plastic roll it around a stick at both ends. The stick should be slightly longer than the width of the plastic and tied firmly to the plastic. This will prevent the plastic to be blown away and it enables the user to lift the plastic up when accessing the Drier from the sides. Having the sticks fixed to the plastic also makes it easier to take the plastic off and roll it up nicely in times when the Drier is not in use.

The Drier should be constructed on the house plot for safe guarding. The use of black plastic (1.5 metres) on the table and greenhouse plastic (3 metres) above enhances the drying process, but the Drier can also be used without plastic (then use a mat or clean cloth to cover the table where your food items are laid out). The total cost for this type of solar Drier depends on the availability of materials: in some areas not even nails are needed as there are enough plants to provide strings to tie the construction. The only 'outside input' is the plastic, where market prices vary. In a normal case the black plastic is locally available on the markets at a cost of ca. 0.25 US $ per m, the greenhouse plastic is more or less the same price, but sometimes more difficult to source. The total cost for the Drier should usually not exceed 2 US $.

[top] [end]Recommended dimensions of a Drier:

Height: about 1 m, to be a comfortable working height and high enough to be safe of children and animals

Width: about 2 m, as the greenhouse and black plastic usually are available in a standard width of 2m

Depth: about 1.5 m (= two arm-lengths, as all parts of the Drier table should be easily accessible)

[top] [end]Why are we promoting a Drier:

In our area in South-East Malawi people's preferred staple food is maize, although it used to be cassava and sweet potato some years back. These crops are now being stigmatised as being 'old people's food'. The situation here is that sweet potatoes are growing like weeds in some areas but people don't consume them. Instead they sell them at very low prices (because of the high supply) and then use the money to buy maize. The trade is not very favourable for them, as they sometimes give away 50 kg of sweet potato for the value of 5 kg of maize-flour, so we encourage the people to consume more sweet potatoes themselves. The biggest constraint on the high yielding varieties of sweet potato is their limited storage time.

We are promoting the drying of sweet potato as a method to conserve them and have them available in the off-season. The sweet potatoes are either cut into pieces or grated with a normal household grater which is available in most parts of the country at a cost between 1-2 US $.

The advantage of using a Drier instead of drying food items on the ground: it is more hygenic (no disturbance by chickens, dogs, goats, children etc.) and more efficient (no moisture from the ground going through).

[top] [end]Use of dried crops:

The dried foodstuff can then be used by soaking and cooking it or by pounding it into flour.

The latest 'creation' is to promote nsima (which in this area is mainly made out of maize flour, in other regions called ugali or pap) out of mixed flour, e.g. 50% maize, 25% cassava and 25% of sweet potato. Considering the limited maize production, the improved ability to store sweet potatoes and cassava enables the food insecure households in our area to have food from own production more or less all year round and not only for 6 months, like it is the case for most of them at present.

[top] [end]The link to household energy

In our project approach we have linked the food processing and energy issues as the saving of firewood is more an aspect of household economy than environmentally driven. Saving firewood for the people here means saving cash and having more resources available to purchase additional food or other items. This is the most fundamental and convincing argument for the people to use the firewood saving stoves, as the deforestation is such that people mostly have to buy firewood in our densely populated impact area.

Household Energy includes all aspects of energy in the household - the drying of food is just one aspect of the energy needs of householders.

All pictures were taken by Christa Roth, Advisor for Food Processing and Biomass Energy Conservation in the Integrated Food Security Programme (IFSP), Mulanje, Malawi. The IFSP programme is commissioned by the German Ministry of Economic Co-operation and Development and implemented by the German Technical Co-operation (GTZ). IFSP started 1996 and is operating currently in 185 villages in Mulanje District in south-eastern Malawi. Since June 1999 , it has been co-operating with ProBEC (Programme for Biomass Energy Conservation in Southern Africa).

More than 15.000 stoves are in use in the Mulanje area. The stove design was advised by expertise from Tanzania and Kenya (e.g. ITDG Kisumu, Kenya). The training of producers and awareness campaigns were carried out mostly by the home economics of the Ministry of Agriculture.

[top] [end]Related topics

Tools and techniques

[top] [end]External links and references

[top] [end]Contributors

For any further inquiries please don't hesitate to contact the authors. We are happy to share our experiences.

Christa Roth and Christoph Messinger c/o Integrated Food Security Programme Mulanje P.O. Box 438 Mulanje (Malawi) Phone + 265 - 1- 466 279, Phone/Fax 466 435, cell +265- 8-860 936 email: messinger.roth@...

Categories: GTZ| Malawi| Food preservation

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Page created: 18 November 2003; Last edited: 26 April 2007; Version: 1
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Pagename: SolarDrier