Cassava processing
Practical Action
Settling is used to separate the starch from the contaminants and fibre. The quality of the
product is dependent on effective separation starch and water. Successive settling tanks or
modern separators can be used. Each operation can be used alone or carried out in different
combinations. The duration of settling process should be as short as possible as fermentation can
start if left for too long. In modern processing methods the period between rasping and drying is
kept to about one hour.
Traditionally, separation takes place in large vats that are difficult to handle and may involve
significant starch loss. A more modern approach is to use channels which curve with a slight
incline. Very high quality starch can be produced in these settling tables. Solar drying of starch is
increasingly being replaced by artificial drying systems but it is reported that this can affect the
swelling property of the starch.
Contamination of local water resources with high volumes of dilute liquid waste is a major
consideration in the production of starch.
Animal Feed
Cassava is widely used as a feed for pigs, cattle, sheep, poultry and rabbits. Whole roots can be
peeled, chopped and given to pigs. Dried root peel can be fed to sheep and goats.
Dried cassava roots contain a similar amount of energy to grains so can used as a substitute for
maize or barley but the roots lack protein so should not be used on their own. They should be
supplemented with other feeds that are rich in protein and vitamins.
Raw or boiled roots can be mixed into a mash with protein rich materials such as maize, sorghum,
groundnut, and oil palm kernel meal along with minerals to provide a balanced feed.
Cassava leaves can also be incorporated into feed. Although the leaves have a higher protein
content than the roots it can only be used as part of the feed. If the amount is too high then the
pigs will not fatten. The leaves need to be processed or left to wilt for a few hours to lower the
cyanide level before feeding.
This commercial use of cassava as a feedstock has only become established in recent years but is
increasing. In Europe the animal-feed industry uses dried cassava roots as an imported ingredient
Industrial uses
Research on the industrial use of starch is continuing to expand the market demand for cassava.
Paper
Starch from cassava, along with maize and potato, can be used in the production of paper.
Different types of starch are used in various stages of paper production. An important new
application of starch is in the coating of magazine paper.
Textiles
Starch is used in three main activities in the textile industry areas: sizing, finishing and printing.
The majority, approximately 80%, of it is used in sizing, where individual fibres of yarn are
formed into a warp that passes through a sizing solution to coat its surface. It is then heated and
when dry the yarn is ready for weaving. Particular properties are required for the starch, which
needs to be able to penetrate and bond with the fibres, resistant to abrasion and flexible.
Adhesives
Cassava, along with potato and maize, is a common source of starch for adhesive pastes. It is a
popular base for adhesives, particularly those designed to bond paper in some form to itself or to
other materials such as glass, mineral wool, and clay. Starch can also be used as a binder or
adhesive for non-paper substances such as charcoal in charcoal briquettes, mineral wool in
ceiling tiles and ceramics prior to firing.
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