Cassava Peel

The cassava root has a thin brown outer skin and, beneath it, a paler cortex that separates fairly cleanly from the starchy parenchyma. Both come away together in most peeling methods, whether by knife or by mechanical peeler, and the peel fraction typically carries a good deal of adhering flesh with it — how much depends on how the peeling was done and how carefully. That adhering starch is why the residue has feed value at all.

Peel volumes are substantial relative to processing throughput, and unlike a dry milling residue this one arrives wet. A processing site therefore generates, every day it runs, a large wet stream that begins fermenting immediately. Where processors cluster, the accumulation becomes a local environmental problem — leachate, odour, flies — rather than merely an unused resource.

Cassava roots naturally contain cyanogenic glycosides, and it is well established that the peel fraction carries a higher load of them than the starchy flesh does. Peel therefore cannot simply be carted from the peeling station to the trough: like the root itself, it requires adequate processing before it is fed, and it needs it more.

The established routes are drying and, in more developed forms, grating, pressing, and drying the peel into a mash or meal — the same logic as the food processing routes, applied to the residue. Sun-drying is the traditional method and is limited by the same thing that limits all sun-drying: it fails in the wet season, exactly when the peel still arrives. Work by CGIAR centres has developed faster mechanised routes intended to make peel a reliable feed ingredient rather than an intermittent one.

Processed peel goes to livestock feed, where its adhering starch makes it an energy source, and it is used across ruminant and monogastric systems in producing regions. Beyond feed, peel is composted, digested for biogas, and used as a substrate for mushroom cultivation — all of them routes that make use of a wet organic stream on the spot rather than trying to transport it.

Handling is dominated by speed and by grit. Peel must be dried or otherwise stabilised quickly, because a wet heap in a tropical climate spoils in a day or two and moulds thereafter; and because peel is what was in contact with the soil, sand and stones travel with it unless the roots were washed properly first. Grit is abrasive in feed milling and unwelcome in a ration, so washing at the front of the line determines the quality of the residue at the back of it.