Turning sludge into fertilizer is not a big ask, technologically — but it’s hard to make a profit because market prices are cheap. Many wastewater treatment plants worldwide, including in the United States, where biosolids are a common by-product of treated sludge, give it away to avoid disposal costs. In Tema, a city east of Ghana’s capital Accra, however, a new plant just sold its first few 50-kilogram bags. The operation should turn a profit within three years, says business economist Solomie Gebrezgabher, who works in the Accra office of the International Water Management Institute (IWMI).