Kenyan teens Fredrick Njoroge Kariuki and Miron Onsarigo developed HewaSafi, an affordable vehicle exhaust filter made from agricultural and recycled waste. Tests show the device cuts particulate matter by 93.3%, reduces carbon monoxide by 42% and absorbs about 21.4% of CO2 emissions. Costing roughly $126 to produce versus about $390 for conventional filters, HewaSafi won the 2026 Earth Prize For Africa and the students plan to scale the design for public-transport vehicles.
Kenyan Teens’ Award-Winning HewaSafi Filter Cuts Vehicle Pollution Using Corn Cobs, Algae and Recycled Waste
Two 17-year-olds made a device that is helping reduce air pollution in Kenya.
When Fredrick Njoroge Kariuki of Kenya turned 12 in 2021, he began experiencing severe breathing problems. Doctors diagnosed him with bronchitis and linked his recurring cough and respiratory distress to heavy layers of vehicle exhaust in his area. Five years later, Kariuki and his classmate Miron Onsarigo — both 17 — developed an inexpensive, award-winning vehicle exhaust filter made largely from agricultural and recycled waste.
Local Problem, Local Solution
Air pollution is a pressing global issue, and it is especially acute in Kenya. A 2024 study found that Nairobi recorded particulate pollution levels 3.7 times higher than World Health Organization guidelines. Experts estimate that air pollution contributes to an estimated 400 to 1,400 premature deaths in Nairobi each year. Much of this pollution comes from the city’s matatus (shared minibuses) and boda bodas (motorcycle taxis), which dominate urban transport.
“The problem of air pollution was very personal to us, and that is why we started thinking about coming up with a solution,” Kariuki told Mongabay. “It was a passion before it became a project.”
“I did not choose this problem. It chose me,” Kariuki told Daily Nation. “Growing up in Naivasha, my bronchitis got so bad that I stopped thinking of air pollution as an environmental issue and saw it as something being committed against us.”
Onsarigo added: “Seeing people get sick as a result of fumes from vehicles has become normal back home in Kisumu County. The ‘normal’ did not feel right to me. I wanted to do something about it.”
What Is HewaSafi?
The students designed the HewaSafi vehicle exhaust filter — named from Swahili words meaning “clean air.” The prototype is built from locally sourced agricultural waste and recycled components, including steel mesh, copper, corn cobs, coconut shells, recycled battery materials and algae. Together these materials form a filter assembly that captures particulate matter and reduces certain gaseous emissions directly at the exhaust pipe.
Performance and Cost
Independent tests of the HewaSafi demonstrated strong results: it reduced particulate matter by 93.3%, lowered carbon monoxide (CO) emissions by 42%, and absorbed roughly 21.4% of the carbon dioxide (CO2) that would otherwise be released. Because many components are reused or sourced from waste, the manufacturing cost is approximately $126 per unit — far lower than comparable conventional filters, which typically cost around $390. That price gap is important for broader adoption, especially on public vehicles with tight budgets.
Recognition and Next Steps
The innovation earned Kariuki and Onsarigo the 2026 Earth Prize For Africa, a regional award that included $12,500 in prize money and international attention. The students plan to use the funds and the connections from the competition to further develop HewaSafi, refine manufacturing, and adapt the design for public-transport vehicles such as matatus and boda bodas. Their goal is to create an affordable line of emission-control products that can be widely deployed in Kenyan cities and beyond.
The HewaSafi project highlights how young people can turn personal experience and local materials into practical solutions for urgent environmental and public-health problems.
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