Sponsored by USAID Farmserve Program and OIC International
Larry Plesent – Volunteer
This solar shea nut drier, or drying tunnel, is based on the original work pioneered by Dr. Peter Lovett PhD., of Tamale, Ghana. Dr. Lovett is the world’s foremost technical expert on shea trees and shea butter, and I am grateful for his help and support on this project. Special thanks to USAID (your tax dollars at work) for contributing to our mission, and to OIC International, the local NGO that took care of us in Ghana. Many thanks go out to WATH; the West African Trade Hub for sponsoring a 2 day educational seminar on shea butter that we attended in Accra.
After a long and hot dry season, the rains bring renewed life to the sub Saharan Region. Shea trees flower during the dry season, and the first early rains bring up the leaves. The fruit of the shea tree sets early in the Rainy Season, and continues for up to four months. Some trees fruit up earlier than others, and the season also varies across the broad swath of the sub Sahara. Fungi thrives in this environment. If the nuts get wet at any stage of the drying process (remember we are drying during the Rainy Season), fungal infections of the nuts will follow.
All shea butter looks good when fresh, but breaks down within 6 to 14 months typically. If there is to be a strong export market of shea butter for natural cosmetic purposes, a 3 to 7 year shelf life is required. It is only by paying close attention to every step of the process, starting with the gathering of the fresh shea fruit, that this kind of long shelf life is theoretically possible.
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The solar shea nut drier we built costs about $225USD in 2005. We used welded rebar (1/2″ iron rod), and used 10.5mil double UV coated woven greenhouse plastic for our glazing. Many thanks to Tammie Espinosa of “A Gardener’s Resource” ; (www.AGardenersResource.com, email firstname.lastname@example.org) for her guidance in choosing this durable glazing surface. A Gardener’s Resource is the US distributor of this particular woven greenhouse plastic cover, rated for up to 75mph winds. They can supply special attachment clips for affixing this, or any other glazing surface to the frame. We used 3/4″ black plastic spring line split the long way to make our own clips. This type of hose is hard to find in West Africa. The homemade clips can be difficult to attach and are not as of yet a proven commodity. Eyelets, permanent grommets, and staking options can also be used to affix the glazing surface. The stronger the better.
Our solar drier is more a prototype commercial model, as it is cost prohibitive for most farmers and co-ops in this region. Research is being conducted on various models of low cost “Local Driers”, which have not been tested as of this writing. My goal was “durability on a budget”, assuming that an extended working life for the unit will provide the best cost/benefit ratio over time. One 20′ long by 5′ unit will dry enough nuts to make (at minimum) 1 drum of butter. A busy village co-op in West Africa could use 10 to 20 of these units per harvest season.
Other agricultural crops such as okra and chilies can also be dried in the unit. Early experiments have produced superior results to traditional drying techniques..
The basic elements of the solar drier are the shelf, hoops and glazing surface. The shelf must sit at least 6″ off the ground, away from flooding rains, and allowing air flow underneath the drier. A reed or split wood mat (not grass if possible), or removable trays made of the same, or alternatively netting and wood, hold the nuts themselves. 100sqft of shelf will need to hold 1,500 lbs of wet nuts.
Hoops may be wood, iron or plastic pipe. Wood must be worked smooth to avoid tears in the glazing surface. Plastic pipe must be reinforced (possibly with sand or wood) as it will soften in the 170F+ heat of the unit. We covered our rebar rods with split plastic pipe as a precautionary measure, to protect against chafing and heat absorption by the metal weakening the plastic. Hoops can be affixed to the shelf, as in our model, or secured into adobe bricks. Shea butter residue can potentially be used to prevent termites from eating wooden components, if this becomes a problem.
Glazing surfaces may vary, depending on cost and availability. We used one of the more expensive options, with single season translucent poly (not recommended) and vinyl sheeting as other options. The clear vinyl (also called rubber or carpet here) is generally available in Ghana, and holds up well to the sun. It is used by taxi drivers to cover seats. We paid 280,000 cidis (about $30USD) for 2 pieces that could be sewn together to make another unit. We left this with the Nasia Women’s Co-op, with instructions on developing their own “local drier” version. We used the “rubber” to seal the ends of the unit against rain, and at night. During use the ends remain open to air flow. Rats have been known to eat the “rubber” so store carefully.
The drier must be oriented so that the prevailing winds sweep moisture out of the unit. Think of it as a solar tunnel. Fans or chimneys may also be used in commercial models to assist in moisture removal, subject to cost/benefit ratio issues. It is critical that moisture is not allowed to build up in the drier. Someone must take direct responsibility for running and maintaining the solar drier.
In conclusion, much testing and experimenting has yet to be done. It is my hope that the solar drier, along with other modifications to the shea butter process, will bring extended shelf life, increased quality, and a small measure of prosperity to the hard working women of the sub Sahara.