The first commercial production of cassava starch in South Africa has begun at CS Manufacturing’s new R28-million factory in Pietersburg in the Northern Province.

Cassava has its origins in South America, with Thailand being the largest producer of the plant at present, exporting five-million tons to six-million tons a year to Europe in the form of animal-feed pellets.

In Africa there are four-million hectares of cassava, all of which are grown in small quantities and used for staple food.

CS Manufacturing MD Jim Casey tells Engineering News that the new factory will produce 60 t of starch a day, which will be used mostly for animal feed and in the manufacture of paper and corrugated cardboard.

South Africa uses about 90 000 t of maize-based starch every year, mainly in paper, corrugated cardboard and food products.

“The estimated value of the starch market is about R150-million a year,” says Casey.

The company currently holds 25% of the local paper and board market.

He adds that it has not only proved that cassava can grow successfully in South Africa, but it has achieved greater yields than the Far East, South America, and other parts of Africa.

Imported cassava product, which secured 15% of the local starch market, will now be supplied locally.

Half of the factory’s capacity is being satisfied by the cassava grown on the company’s surrounding farmland.

Additional cassava is being produced by commercial farmers on the company’s behalf, explains Casey.

The company plans to encourage small-scale farmers to begin growing the root vegetable over the next few years.

“This is one of our main goals for this year: we will supply planting material free of charge, provide agronomic assistance, and guarantee to purchase the entire harvest at predetermined prices, as agreed with the growers,” he says.

Technical director Siegfried Eggers explains to Engineering News that cassava has several advantages over potatoes and grain in that it is a drought-resistant crop, it can be harvested after nine growing months, and can be processed within 24 hours.

“Furthermore, it does not deplete nutrients in the soil, and farmers could grow the plant in the intermediate periods between potato planting,” says Eggers.

The process of manufacturing starch from the root of the cassava plant at the factory begins with the receipt of tubers.

Incoming tubers are weighed, and samples are analysed for starch content to calculate the price payable to the growers. This process is quick, and is conducted at the factory gate.

Thereafter the tubers are offloaded at the dry-peeling and washing section of the operation.

In the dry-peeling process, tubers are fed from the main bunker by conveyor to a rotating-bar screen to remove loose dirt, sand, gravel and skin.

Peeled tubers are conveyed over an inspection table to a rotating washing drum from where the raw material is transported by an inclined belt to a precutter before feeding the rasps.

Rasping is the first step in starch extraction and, in this process, all tuber cells are opened so that all starch granules are released.

Raspers are high-speed machines for optimal starch recovery with dual-rotation operation for extended rasper life.

Two raspers ensure continuous operation during the exchange of blades.

Disintegrated roots are collected in a pit below the raspers, and pumped by a special vertical-shaft centrifugal pump to the extractors.

In the extraction process, starch granules in the disintegrated roots are extracted in a series of rotary screens in a countercurrent process.

Washed fibres are discharged by special built-in pumps to a pulp dewatering screen, and the starch slurry is pumped to the concentration section.

Extractor screens are equipped with high-quality sieve plates made from stainless steel, and which can withstand abrasion and harsh chemicals.

The sieve plates have long perforations with a diameter of about 125