For more than 10 years, Denis Matembe had been roasting chicken over a charcoal stove in Kampala’s Wandegeya suburb. His work starts at 4pm, when he lights the stove and ends late in the night. For years, he used up one sack each week, depending on the quality of the charcoal. Quality charcoal takes a long time to reduce to ash and therefore depends on the kind of tree it is produced from such as mvule, mango, and shea nut. However, the government has now banned the felling of these tree species for charcoal. In 2016, Matembe’s boss, Joseph Kalema, heard of something called “wonder rocks.”