Abstract: In a process for burning a combustible, sulfur-containing carbonaceous material such as coal, municipal waste, or tires, recrystallized metamorphic CaCO.sub.3 is introduced into the combustion zone along with the fuel. The amount of SO.sub.2 and NO.sub.2 generated is substantially reduced as compared to conventional processes and, even with no post-scrubbing equipment, the emission levels compare favorably to the emission levels of state-of-the-art power plants using the same coal with extensive emission controls. The present process also acts to convert sulfur resident in coal into elemental sulfur and loose sulfur compounds and to reduce the particulate output.