As Southern Africa struggles to recover from its worst drought in decades, farmers are seeing their crops destroyed due to El Nino weather changes. Famine afflicts millions of people. Without crops, farmers can’t eat. Without money, they can’t buy farming supplies.

To help them find low-cost pesticides and fertilizers, Mphatso Simbao, a 19-year-old from Lusaka, Zambia, has found a way to produce fertilizer and pesticide from unwanted plant material, ash, mud, water and heat.

Mphatso says his technique cuts fertilizer costs in half and saves farmers up to 80 percent of the cost of pesticides. The project won a national award at the 2016 Google Science Fair engineering competition.

We spoke with Mphatso on phone from Lusaka, Zambia.