The Universal Nut Sheller (UNS; formerly called the Malian Peanut Sheller) is a simple hand-operated machine based on a Bulgarian Peanut sheller, capable of shelling 50 kilograms (110 lb) of raw, sun-dried peanuts per hour.
It requires less than $50 USD in materials to make, and is made of concrete poured into two simple fibreglass molds, some metal parts, one wrench and any piece of rock or wood that might serve as a hammer. It accepts a wide range of nut sizes without adjustment. Operators can make necessary adjustments quickly and easily. It is estimated that one Universal Nut Sheller will serve the needs of a village of 2,000 people. The life expectancy of the machine is around 25 years.
The Full Belly Project is working to establish local, sustainable businesses that manufacture and distribute appropriate technologies such as the Universal Nut Sheller.
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The user loads the desired crop in the space at the top. The user turns the handle, which rotates the rotor continuously. This creates centrifugal force, which pushes the nuts towards the gap at the exterior wall of the machine. There, the nuts fall through a gradually narrowing gap. The shell of each nut is broken at the point where the gap is sufficiently narrow and the rotor motion causes sufficient friction to crack open the shell. The tapered gap allows a range of nut sizes to be shelled. The kernels and shell fragments fall into a basket and are later separated by winnowing. The device works best for Jatropha curcas, shea, dried coffee, and peanuts (ground nuts).
The Full Belly Project has developed a Pedal Powered Agricultural Processor.[1] The Pedal Powered Agricultural Processor places the Universal Nut Sheller onto a pedaling chassis. In addition to the shelling method described, the pedaling apparatus is connected to a fan. The fan automatically winnows the harvest (separates the shells from the nuts). The pedal powered versions are capable of shelling the same variety of crops as the hand crank powered versions. The processor also provides access for the winnowing section to be used independently from the sheller. This allows winnowing of crops that are not shelled, such as rice, maize, sorghum etc.
The Universal Nut Sheller has been less than successful in Ghana. First hand accounts relate almost universal breakage. Users can mitigate this breakage by pouring the nuts through initially at very broad settings and only later at finer settings, this practice does not eliminate the breakage and destroys the efficiency aspect. Groundnut shelling tends to be a social activity everyone engages in during their down time and there is rarely a need for a peanut sheller.
The Universal Nut Sheller proved incapable of shelling shea nuts in a manner useful for shea butter extraction for the shea nuts of Ghana. However, there are reports that it works for shea nuts from trees in Uganda.
The cost also proved a significant barrier. It simply cost far more to produce (even excepting the cost of the mold, transport of materials to the village, travel to the nearest town to find someone capable of welding the metal parts, etc.) than individual growers were able to pay. However, growers unions who made the investment have been successful.