The dark hands of a farmer hold open a sack full of tomatoes, with another full sack beside it.
Credit: Camille Delbos/Art In All of Us/Corbis via Getty Images
Tomatoes are a staple crop in Rwanda's Bugesera district.
Spoilage of perishable farm produce is a major challenge facing smallholder farmers in rural, low-income settings in Africa, where grid electricity is inaccessible, unreliable, or nonexistent. That’s why a team called FruiFresh, made up of students at the Rwanda Institute for Conservation Agriculture, the University of Rwanda, and the Institute of Applied Sciences–Ruhengeri, has developed a cold-room facility that helps solve the longstanding problem of postharvest losses in the region.
In June, the FruiFresh team won first place at the 2024 Wege Prize, organized by Ferris State University’s Kendall College of Art and Design. The prize, which comes with a $30,000 cash reward, is awarded every year to college or university students around the world who come up with innovative solutions to difficult problems.
The team’s effort was cited for alleviating postharvest losses for tomato farmers and retailers in Rwanda by building large, naturally evaporative, charcoal-based cooling facilities. And they did this by using affordable materials that could be sourced locally.
According to the Food and Agriculture Organisation (FAO) of the United Nations, more than one-quarter of Rwanda’s annual food production is written off because of spoilage and postharvest loss. This is particularly significant, considering that the country’s economic output comes mainly from agriculture.
Claudine Kamanzi, a young woman, smiles to the camera.
Credit: Courtesy of Claudine Kamanzi
Claudine Kamanzi is the FruiFresh team's leader.
The FruiFresh team, led by conservation agriculture student Claudine Kamanzi, started working on ways to improve these statistics. The result is a low-cost, ecologically friendly cooling system that uses the porous property of charcoal.
The design by FruiFresh passes water over layers of charcoal residue carefully placed against the clay-brick walls of a storage room. Water is passed through these charcoal layers three times a day. The hot and dry air outside is then directed through the wet charcoal residue, and the heat in the air evaporates the water, which helps to bring down the temperature in the storage room. According to the team, these facilities can reduce the temperature by 9–10 °C. But that’s not the only benefit.
The porous structure of charcoal allows it to absorb a lot of water quickly, and its high surface area makes it ideal for purifying the rainwater that the system runs on. The drainage system is a closed loop, so that water passing through the charcoal is brought back into the system to be reused.
The efficient water use is an important aspect of the design, not least in the semiarid Eastern Province of Rwanda.
According to Kamanzi, a charcoal cooler with a volume of 16 m3 can accommodate 520 kg of produce. The system has been shown to extend the shelf life of tomatoes for up to 15 days, enough to make a difference for smallholder farmers in Rwanda and reduce food insecurity in the area.
“By using evaporative cooling, we help farmers preserve their perishable produce like tomatoes, reducing spoilage and ensuring a stable food supply without relying on electricity or expensive infrastructure,” Kamanzi says.
In so doing, she says, FruiFresh is also addressing the UN’s sustainable development goals (SDGs), particularly SDG2 (zero hunger), SDG12 (responsible consumption and production), and SDG13 (climate action).
“We sought innovative solutions that could not only improve food security but reduce waste and carbon footprint,” she says.
The charcoal-based cold facilities are targeted particularly at smallholder tomato farmers in Bugesera District, in eastern Rwanda on the border with Burundi, some 44 km south of Kigali, Rwanda’s capital.
Tomatoes are a staple vegetable for people in Bugesera District. But they are also highly perishable and susceptible to spoilage without proper storage.
The concept of a charcoal-based cooling system is not new, but FruiFresh’s design meets the needs of the people of Bugesera District without being too expensive. And by utilizing clay, timber leftovers, bricks, and repurposed charcoal remnants sourced locally, the initiative supports the local economy.
For example, by replacing metal, a material commonly used in constructing cooling facilities, with 50% locally sourced timber, the FruiFresh design reduces construction costs and cuts out the carbon footprint associated with metal production and transportation.
To source the charcoal for the coolers, FruiFresh pays locals $0.10 per kilogram of charcoal left over from cooking. Community members gather this material mainly from high school kitchens and households.
When the charcoal needs to be replaced, the used charcoal can be mixed with compost to create biochar. That biochar can be used to raise soil pH, repair polluted soils, and benefit overall soil health, given its rich potassium and calcium content, Kamanzi says.
By using evaporative cooling, we help farmers preserve their perishable produce like tomatoes, reducing spoilage and ensuring a stable food supply without relying on electricity or expensive infrastructure.
Claudine Kamanzi, FruiFresh team lead
“This innovative approach aligns with our commitment to sustainability and offers a cost-effective solution for farmers,” she says, adding that using biochar reduces the need for chemical fertilizer in farms.
FruiFresh has now constructed a charcoal cooler with a 10-metric-ton food-storage capacity in Karongi District, 112 km west of Kigali. The fully operational facility was set up in collaboration with a women’s farmer cooperative, whose 50 members sell fruits and vegetables. Starting in November, the team will observe the system’s adoption for 3 months. The feedback they gather will inform their construction of other coolers in Bugesera District in phase 2 of the project.
Kamanzi says more farmer cooperatives have placed requests for cooling systems. To cover the costs, farmers are charged a fee per kilogram of produce they store in the facility per week.
The FruiFresh team estimates the cost of constructing and running a charcoal-based cold room to be $26,190 per year. But the storage fee charged to farmers for accessing the service is set to gross the team $43,200 per year.
Kamanzi explains that a charcoal-based cooling facility typically will require only about 10–15 m2. That area “accommodates the charcoal cooling structure and provides enough ventilation and access for farmers to load and unload their produce,” she says. And besides providing storage, the charcoal-based cold rooms provide a space to market smallholder farmers’ produce.
Promoting the concept of a charcoal- based cooling system in the Eastern Province of Rwanda is one of the challenges encountered by the FruiFresh team. Convincing local farmers to adopt a new technology is not easy, the group says. But team members are addressing this challenge by training agronomists on how the system works before also training farmer cooperatives and groups.
Getting funds to expand FruiFresh’s reach is another major challenge the team faces. But the group says that the demand for sustainable solutions presents an opportunity to partner with the government and nongovernmental organizations to reach populations in need.
Geoffrey Kamadi is a freelance writer based in Nairobi, Kenya.
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