How to Shell Maize

Hi everybody!

We’re working hard here at Twende to reach a reference design for the maize sheller so that we can sell a preview at Nane Nane, a big Tanzanian agricultural festival during the first week of August. We have two more shellers in the field now, both in Singe, another Babati village. Tomorrow, we’ll go check in on all three sheller owners.

On this trip, we also plan to learn more about existing methods of maize shelling. We’ve seen and heard of several other ways to shell maize and we want to characterize them with reliable numbers for speed and cost, both in time and money. Manual shelling seems to be the most common method for removing kernels from the maize cobs. If the maize is dry, you can pop kernels off with your fingers or by twisting the cob. As you can probably imagine, it takes a while to fill a gunia—the standard 100kg sack—this way.

To speed up the process, farmers will instead pile the maize in a tarp or sack and beat it with sticks. We call this the kupiga method. Kupiga means “to hit.” It’s faster, but it breaks the cobs and many of the kernels. And it’s still hard work. On every user visit, we’ve tried to nail down some sort of rate estimate for this method, but responses are all over the place. The absolute fastest quote we’ve heard is 1 gunia per hour, but most of the people we interviewed guessed lower. Kupiga shelling also usually requires multiple workers who the farmer pays either in cash or in food and drinks for a day of work.

Shelling machines do exist, but most of our target customers either can’t afford them or don’t harvest enough maize to take full advantage of them. We’ve found  motorized shellers powered by tractors or motorcycle motors in most villages we’ve visited. During bountiful harvests, some of the farmers we’ve met will pay owners of smaller motorized machines to shell their maize for a fee per gunia. We’ve heard of large tractor-powered shellers that are operated by 12 workers and can shell 30 gunia—3000 kg—per hour. Those machines sound too large to be economical for our target market, but we’re hoping to see one on our next trip to Babati. Learning about existing shelling technologies and business models will teach us more about our customers’ needs and help us assess the feasibility of our bicycle-powered sheller.

Note: I took some explanatory pictures to post here, but I've been having a bit of computer trouble. I'll try to update this entry with pictures soon.