AgTech: Solar Dryers and Metal Silos

Of the many means of storing food looked at, the two most efficient and economical ways were metal silos and solar dryers. Metal silos are used to store grain so it is not left uncovered, reducing the amount of grain spoiled by rain exposure and pest penetration (Proctor, 1994). Solar dryers, on the other hand, help process meat, fruit, and vegetables that would otherwise rot quickly. Dryers will reduce the need for complex storage by making food last longer. Simultaneously, they increase food safety by removing the water content so that bacteria and bugs cannot contaminate it as readily (Heinz, 1995). They will also enable farmers or other people to create value-added goods (such as fruit bars or jerky) that are easier to transport and are export quality, thereby increasing their incomes. Implementing solar dryers and metal silos will help in many ways including higher quality storage, food safety, and increasing agricultural income.

Metal silos, though usually considered too expensive for small individual farmers to buy and thus only valid for storing large quantities, have been proved useful on small scales (<1 ton to 10 ton) in many places. Swaziland and Bolivia are examples that have had long-term success with metal silo storage. In Bolivia, 96% of the farmers who received silos improved food security, reduced waste, and maintained the quality of the grain. The Food and Agriculture Organiazation of the United Nations (FAO) also succeeded in introducing household metal silos in 16 countries across Asia, Africa, and South America (Household Metal Silos, 2010).

Of the several ways to process food which were analyzed including canning, smoking, salting, fermentation, cooking, etc, solar dryers were particularly attractive because they can be used with all types of food (grain, fruit, vegetables, meat, and even cash crops) and they do not require extra energy from an engine or battery. Drying in general is a fairly common practice in many areas, but it is typically done by spreading out the crop on the ground. This method has many problems such as spoilage due to rain, wind, dust, insects, etc.

The solar dryer consists of a large chamber with metal walls and a glass top at an angle proportional to the latitude at which the device will be used. There is a small photovoltaic cell that powers a fan to increase the air flow and to charge a battery for use on non-sunny days (Enolar Systems, 2003). Solar dryers dry food in a clean, hygienic environment that reduces space and labor. They require very little labor (about one hour a day or less) and yet can greatly increase the amount of high-quality food available. The women can put in a load to dry and then go about their other tasks, so it is ideal for rural workers who have many tasks (Balakrishnan, 2006).

Both metal silos and solar dryers can be adapted to fit a variety of local conditions. Metal silos can be constructed locally, similar to water tanks. Sheet metal and other materials needed for construction should be provided and subsidized by government agencies or the local private sector. Solar dryers require very little infrastructure beyond the cost of the dryer, and can be beneficial to farms of any size. They are also suitable in many climates, although there are certain areas with inconsistent or too little sunlight that would make them not profitable for farmers. India is a promising place for these, as it could be used at least 250 days of the year (Balakrishnan, 2006).

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