Fredrick Njoroge Kariuki and Miron Onsarigo, both 17 and from Kiambu county, Kenya, built HewaSafi — Swahili for "clean air" — an exhaust filter made from coconut shells, maize cobs, copper, steel mesh, and spirulina algae. Tested on Nairobi minibuses, it cuts PM2.5 particulates by 93.3% and costs $126, versus $390 for existing filters. They just won the Africa region Earth Prize.
(c) Garvin St. Villier

Kenyan teens build exhaust filter from maize and coconut that cuts emissions by 93%

MONGABAY

Fredrick Njoroge Kariuki and Miron Onsarigo, both 17 and from Kiambu county, Kenya, built HewaSafi — Swahili for “clean air” — an exhaust filter made from coconut shells, maize cobs, copper, steel mesh, and spirulina algae. Tested on Nairobi minibuses, it cuts PM2.5 particulates by 93.3% and costs $126, versus $390 for existing filters. They just won the Africa region Earth Prize.

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