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Food Storage System: Solar Dryers & Metal Silos

Silo Image

(Source: Household Metal Silos, 2010)

One main reason why food is not distributed equitably is that so much is wasted. It is estimated that 25%-30% of all the food produced is wasted due to inadequate storage. Particularly, in India about 7% of grain and 30% of fruit and vegetables produced annually are wasted due to lack of proper storage systems (Murthy, 2010). A large percentage of the grain waste in India occurs while it is collected in governmental buffer stock. The government stores massive amounts of food to distribute to the people, but this system is highly inefficient and much of the food is not used or spoils in storage. However, an Indian government representative claims that the grain wasted in buffer stock is too little to deserve any attention (Bhattasali, 2008). More waste is due to the transportation of food from farms to the centralized storage warehouses and then to markets, which increases the price of the food significantly.

The major objective of storing food is to ensure local food security. However, food security is not the only advantage. Grain storage on small farms is a form of saving that can later increase farmers’ incomes. It helps stabilize the crop’s market price.  Food prices are extremely volatile due to a large number of factors, including seasonal shifts, commodity speculation, and trade.  If farmers can store their goods, they can sell them over a longer period of time, reducing the cycles of surplus and scarcity connected to the seasons. Farmers get higher prices in the off-seasons and so the ability to store their crops would increase their income.

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. 

Solar Dryer Image

A study was done in 4 regions of India by the All India Women's Conference, an organization dedicated to improving the lives of women and children in India. This organization gave solar dryers to groups of 50 women who used them to make products for the local school lunch program.  Because the solar dryers are so flexible, the women could choose from a wide variety of products to make that are marketable and so maximize their income.  The dryers cost about $1700 for a 50kg unit and the organization estimated that the women would be able to pay it off in 10 years based on the income it generated. This study also incorporated education programs on how to use the solar dryer, packaging, business, and other topics (Balakrishnan, 2006).

(Source Balakrishnah, 2006)     

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).

The plan is to introduce the storage facilities to farmer cooperatives instead of individual farmers. Each cooperative will own solar dryers and silos that will be shared among its members. This way, it becomes easier to purchase the units because the farmers pool their resources. With more labor and raw crops available, they can be used at their full capacity, thus generating the most income as opposed to a family who might only use them a few times a week.  Each cooperative should have greater access to both needed capital and markets and thereby increase the efficiency of each solar dryer or silo. 

Drying Image







(Source: Household Metal Silos, 2010)

As demonstrated by the case study in rural India, the solution to food storage needs to be a bottom up approach. Communities need to be identified where the people have access to fresh food that is currently wasted and who are willing to put in the time to store it properly. Farm cooperatives are potential candidates. A group would also need to be formed to actively promote the storage technology, provide the education necessary, as well as help with financing. This group could be local or a central NGO or government agency (Balakrishnan, 2006). A major task of this group will be an in-depth study in each region they want to implement these in to determine what the local crops are, what the market value for the crops are, and how large a dryer can be effectively used by the available people.  Without this research the machines would not be used effectively and might cause farmers to go in greater debt.

According to the FAO, a 500-kilogram metal silo costs between $30 and $100 initially and very little to maintain (2008).  Generally silos lasts about 20 years, and a well-maintained one can last up to 30 years. Based on the dryers used by the case study (Balakrishnan, 2006), solar dryers cost about $34 per kilogram of space (the study used 50 kg dryers at $1700 a unit) (Enolar Systems, 2003).  The way to finance it would be through microloans, possibly slightly subsided by the World Bank or other organizations.  Kiva is a successful program that lets developed nations loan money to individual entrepreneurs who request capital.  In this model, the people are invested in the project and will use the facilities to its advantage more than if they were simply given it by foreign aid. Kiva has many loans that are near this amount ($1700) so it would be an ideal microfinance system once the information is out to farmers and interest is generated in using dryers and silos (Kiva).  The agency responsible for promoting these technologies will also be responsible for assisting the farmers or cooperatives with securing a loan from Kiva by partnering with the local banks.  This partnership will be expanded when new technologies become available, and may even serve as a testing method for new innovations.

Kiva is a microfinance system that searches for interested entrepreneurs who will maximize the usefulness of the system.  A large fund might also be needed to partially subsidize costs to make it easier for farmers to pay back the loan.  This could come from a wide number of organizations like the World Bank, IMF, a NGO or charity organization. The amount needed depends on the area and what funds the farmers typically have available as well and their ability to pay off the loan.  A new group would need to be set up to coordinate these funding sources with the companies producing storage systems with the farmers or cooperatives in need.

 Fishermen in Northern India 

(Photo courtesy of Heather McDonald)

This is a short term plan that will have positive impacts in the long run.  The Solar Dryers case study mentioned above was over a year-long period. Once the dryers are received or the metal silos are constructed, they provide income at the first harvest. The limiting factor is that it might take a while to generate interest depending on the culture and how much education is available; that time depends greatly on the region and the people who are promoting the solution. This is therefore a short and long term solution because it is extremely sustainable and increasingly scalable with increasing technology and interest. Estimated, it would take between 5-10 years once an advocacy group is formed.

Farmers’ attitudes to storage and the long term value of the investment in capital need to change. The wastage of food is partly due to farmer’s priorities. They may not see storage as a beneficial investment with their limited funds and will not be looking for innovative ways to process food. This is why there is such a lack of storage in the developing world and why there are few efforts to increase storage technology and reduce waste.  Rural farmers have very little money to spend are are often heavily in debt and cannot invest in storage systems, and so much of their crop is wasted.  Reducing this waste by providing low-cost means of storing food will increase the amount of food in the world and increase farmers' incomes.  

Works cited: 

Balakrishnan, L., & Banerjee, M.  (2006). Solar Dryers – An Income Generation Option for Poor Women.  Energia, 9(2), 16-17. Retrieved November 20, 2010, from

Bhattasali, A. (2008, July 4). India Food Grain Waste Revealed. BBC News. Retrieved  November 19, 2010, from

Heinz, G. (1995). Preservation and Processing Technologies to Improve Availability and Safety of Meat and Meat Products in Developing Countries. World Animal Review, 8180,  Retrieved November 29, 2010, from

The Food and Agriculture Organization of the United Nations. (2008). Household Metal Silos. Retrieved November 14, 2010, from

Kiva is a site that presents the details of the Kiva program, a microfinance program aims to relieve poverty in developing countries (

Murthy, R. (2010, July 21). India outsources food-waste woes. Asia Times. Retrieved November 29, 2010, from

Proctor, D. L. (1994). Alternative storage technology at farm/village level. In Grain Storage techniques - Evolution and trends in developing countries. Retrived November 29, 2010, from storage technology at farm/village level

Enolar is a site that presents technical information and detailed prices of solar dryers (

World Food Programme. (2009). World Hunger Series Hunger and Markets. Retrieved November 29, 2010, from,com_docman/task,doc_view/gid,1477/Itemid,98/