grain storage

Reduce grain storage risk with drying bags

Werner Swart, along with his partners, has developed a portable drying system for grain storage which allows him to rapidly and successfully dry grain and oil seed in silo bags.

By drying and storing grain and oil seed in polyethylene silo bags, farmers are able to harvest sooner and thereby reap the rewards of risk management.

“Consider what happens to crops such as beans and wheat if it rains during the harvest period. With this bag system, farmers can take advantage of earlier planting dates for succession crops, overcoming the problem of frost by using supplemental burners”

grain storage
Werner Swart with one of his polyethylene silo bags.

This is the view of Werner Swart, who developed the system using his engineering and business knowledge. It is marketed by a South African company, Drylobag International. The bags are black on the inside and white on the outside, with a protective UV-layer.

Werner got the bright idea of adapting his silo bags three years ago when he saw bags of peanuts standing on his lands.


The silo drying bag
This is a silo bag with an air ventilation pipe along the one side of the bag. The pipe is separated from the bag by a permeable membrane which allows air to pass evenly through the contents of the bag to dry it. An outlet pipe is located on the other side, also separated by a permeable membrane, through which the moist air is expelled.

Dryer (De-humidifier)
The dryer is set according to the type of grain and its moisture content. The unit will turn on and off automatically to facilitate drying. Extra heat can be supplied via a built-in gas burner. A diesel engine-driven fan has also been developed which constantly blows heat at 5°C for use on those locations where electricity is not available.

Filling of bags and out-loading of soft crops
Machines that fill the bags by means of gravity and not by means of an auger conveyer were specifically tested for the filling of bags of groundnuts or other products that can get damaged in the mechanical process. Groundnuts can thus be dried in bulk which means a cost saving and simplifies the production process. The out-loader or de-bagging machines use a scoop system which doesn’t damage the grain.

grain storage


Maize, peanuts and wheat have all been successfully dried, says Werner.

Two groups, Vita Nova and Roba Foods, from Bloemhof and Setlagoli respectively, have dried peanuts commercially in bulk in this manner. “Doors Kruger of Silostrat, a grain merchant from Welkom in South Africa, was involved with the development of the drying bags, and ran a trial of about 1000 tons of maize with a moisture content of 18%,” says Swart. “The grain was dried without gas initially, with great success, but heat was later applied to shorten the drying time.”

In another trial, wheat with a moisture content of 24% was dried by Johan Pienaar of Bultfontein. “What was notable was the improved grain grading compared to the wheat harvested on the lands,” says Swart. There is naturally a price benefit as the products are delivered to market earlier. This can improve the farmer’s cash flow.

The bags are easy to use and can be utilized almost anywhere. This keeps transport, drying and storage costs down in the delivery period because it can now be done economically right on the farm.

grain storage
The dryer attached to a Drylobag. The drying process can be done with air aloin if it is warm and dry enough, or with artificial heat generated by a fan driven by a diesel, petrol, or electrical motor.


The price of a de-humidifier in South Africa varies from R65 000 (K50 000) to R95 000 (K70 000) and the single-use bags with a capacity of 200 tons cost approximately R12 600 (K9500) each. Self-regulating dehumidifier-units are also now available – it swiches itself on and off and are diesel powered. The cost of importing to Zambia will still have to be added to this.

If the capital costs are amortized over five years, then the cost per ton for drying and storage of grain over a period of one year works out to R60 to R70 (K44-K52) per ton.

The system was developed and tested over a period of three years. Up until now the bags have been manufactured by hand at Bultfontein, but plans are progressing well to establish a facility in Welkom to produce the bags on a larger scale for the local market.

Enquiries: Werner Swart – 002782 886 7404 or

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