Ash material, discharged from power plants, contains various amounts of unburned carbonaceous matter (UCM) depending on their operating conditions. Due to its extremely oxidized state the UCM has an increased reactivity to release a variety of organic impurities upon disposal while it represents a recyclable source of energy. In the current work, separation of the UCM from the bottom ash of a power plant has been studied using the Jameson cell flotation technique. The influence of operating parameters such as superficial gas velocity, bias factor, percent solids, dosage of reagents and conditioning time on the recovery of the UCM was systematically examined. As a difficult-to-process material, the UCM can be separated from the bottom ash with a recovery of 67.5% and reduction of the ash content from about 90% to 44%. The product has a calorific value of 3740 kcal kg(-1), which can be useful as a recycled energy. (c) 2008 Elsevier B.V. All rights reserved.