Cassava in the Classroom


Cassava has visited Ellen Su in her dreams on at least three separate occasions since she began her final semester at Yale. The edible root is somewhat of a ticking time bomb; it produces toxic levels of cyanide just 48 hours after harvesting. Nevertheless, cassava is a staple crop for nearly one billion in the developing world. And this semester, it’s taken Yale’s Center for Engineering Innovation and Design by storm.

The potentially deadly crop has consumed the lives of Su and 20 other students since they were admitted to a course called Appropriate Technology for the Developing World (MENG 491) in January. Officially, the class is part of the mechanical engineering department. But with a mix of global affairs, economics, art, and engineering majors, it blurs disciplinary lines with the goal of finding a solution to a real-world problem. This year, the students were challenged to make cassava safer and more valuable to the hundreds of millions of people who grow it every year. Professors Joe Zinter and Robert Hopkins—whom the students call Joe and Bo—don’t start out with any idea of what the “right” answer is, nor do they believe there is such a thing. “The only thing we know for sure on day one,” the duo said, “is that we have 15 weeks to do it.”

Appropriate Technology for the Developing World is the brainchild of Zinter and Professor John Morrell, who left Yale last year to work for Apple. The two were working on a Bill Gates funded development project in sub-saharan Africa when the idea for the course began to take shape.

Yale is notorious for its theory based courses and liberal arts bent. In a school where obscure and esoteric class names often become punchlines, Zinter said they wanted to start a course that would “introduce students to the process of complex and multidimensional real-world problem salving.”

For many students, the course is more of a calling than just another credit. “I’ve been working up to it,” said Su. “I took a lot of classes just so that I would be able to contribute it.” The kids are remarkably motivated. For them, the idea that their work could amount to more than just a letter on a transcript is an exciting one. “There’s a strong sense that the outcome is a product of your effort,” said Charlotte McCurdy, a former student of the class who is now the teaching fellow. “You’re not going to be carried along. And if you fail—which is exciting.” The hope is that the class will be able to design a product that will outlive the short semester.


On one of the first sessions of the course, students walked into a classroom outfitted with hot plates, knives, graters, and a box of water. “Today we’re going to figure out what cassava is,” said Zinter. “Go grab one and make it edible.” For the better part of an hour, the students played around with the food in order to get familiar with it. That first exercise set the tone for the rest of the class, which Hopkins and Zinter say is all about “learning by doing” and “becoming comfortable with being uncomfortable.”

After getting some hands-on experience with cassava, the students dove headfirst into weeks of rigorous research. They wanted to understand the crop from every possible angle: “societal, economic, and scientific,” said Levi DeLuke, an engineer. The group eventually came to a shared understanding of where an innovation might be both possible and exciting. They split up into two teams: tech—which was in charge of building the physical prototype— and commercialization—which devised a plan for bringing the product to market.

But in an unconventional course like this one, figuring out what the next step should be isn’t always an easy task. “You don’t have it all planned out,” said Su. “You can only say where you hope to be. Dealing with frustration and not being completely sure of what you’re doing is something the class teaches you.” Part of the challenge, is that the students not able to get on the ground and talk to people who have experienced the dangers of cassava firsthand. They must design a product for farmers halfway across the world from the comfort of Yale’s Center for Engineering Innovation and Design. “We do our best,” said one SOM student in the course, “but we’re limited.”

Spring break came and went, and the students began to ask themselves what they were actually going to build. “We were talking about things and drawing things and talking about more things,” said DeLuke, “but at a certain point you have to be like, ‘we’re going to do this because talking about it isn’t getting us anywhere.'” The group had drawn up a laundry list of ideas—from making cassava cosmetics to using the crops hydrogen cyanide for low power batteries—but none of them stock. Feeling desperate, the students hopped in a car and drove to Home Depot for inspiration one mid-semester weekend. They dropped several hundred dollars on various materials and supplies in hopes of kickstarting the prototyping process.

The next, week MENG 491 took over Yale’s Center for Engineering Innovation and Design. Filled with 3D printers, laser cutters, arduinos, and power tools, the open floor plan center is an inventor’s paradise. The wall facing the street is made entirely of glass and from the outside in, it looks like an aquarium of engineers.

The surprisingly low-tech MENG 491 calendar hangs from a table in center of the room. It’s nothing more than a giant poster covered in Sharpie scribbles, but so far it’s kept them on track. Some say creativity can’t be scheduled, but Joe and Bo think otherwise. To them, the students’ breakthroughs are a product of their constraints. “Innovation comes in these structured moments. It’s not eureka bathtub time,” said McCcurdy. “And no matter how they think about it, their first prototype is going to be wrong,” she added with a smirk.

The problem with cassava is that farmers have only two days to process it before it becomes toxic. They must peel it, grate it, and wring the water out of the leftover pulp. This “waste” water contains starch that is ten times more valuable by weight than the cassava itself, but it is often lost to the ground.

The MENG 491 decided they’d engineer a device that would streamline the processing of cassava, increase its shelf life by weeks, and preserve the valuable starch water. “It’s not like you’re taking value away from other people or shift ing it,” Su  explained. “You’re actually creating value from what was previously a waste product.”

Just one week after their impromptu Home Depot trip, the students had already built a semi-functional prototyping.”We went from a pile of nothing to this in four days,” Zinter said as his students crowded around him. “That’s a labor of love.” But McCurdy was right—their first prototype was far from perfect. Several of the parts were not working properly and the design was a little rough around the edges.

Members of the tech team had spent long nights in the Center for Engineering Innovation and Design testing the pH of rancid cassava water, baking starch, and refining their prototype. It wasn’t at all uncommon for tech team to have marathon work days on weekends. They were dedicated to making their product come to life. The commercialization team was, as Zinter put it, a different form of chaos. They grounded the sometimes high-flying engineers in the pragmatics of people and markets.

With only a few weeks left in the semester, the tech team was ready to show off a final version of their contraption. Zinter called the commercialization students over to the workshop area and both teams circled around the device, flashing each other looks of nervous excitement through their safety goggles.


The MENG 491 class and their contraption, which is made up of a cylindrical grater, two belts, and a tensioning mechanism. It grinds the cassava into a paste and dehydrates it by squeezing it between the two rolling belts.

DeLuke handed a cassava to Zinter, who inserted an electric screwdriver into a notch on the side of the device (a temporary hack that kept the grater continuously turning). He powered it on and the grater began to rotate at high-speed. After a few seconds, Zinter slowly lowered the cassava to the metal. On contact, the contraption buzzed, a fountain of cassava pulp sprayed onto the roller, and the valuable starch water dripped into a bowl below. The students clapped and cheered, excited by what they’d managed to create. The machine, may seem rudimentary. But to millions of farmers in the developing world, it could mean the solution to


It’s a shame there aren’t more classes that take the hands-on approach of Appropriate Technology for the Developing World. The education system today often seems to overemphasize disciplinary divides and dismiss the value of learning by doing. Of course, not every school has the resources to make this sort of thing happen but the class is a testament to the value of experiential education in the coming age of the MOOC. It’s not clear whether the device, dubbed SAVA, will ever make it into the hands of farmers overseas. For various reasons, many of the students can’t commit to the project. But if nothing else, they will have left the semester equipped with the tools to create and commercialize the technologies of the future.

Aaron Lewis is a junior in Saybrook and a Cognitive Science major. Outside of the Yale Entrepreneur Magazine, Aaron is a studio leader for Design for America and a writer for the Yale Daily News. He loves to longboard and play the classical guitar, and sometimes does both at the same time.

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