The stillage obtained in processes employing sugarcane, acid hydrolyzates of wood, or spent sulfite liquors as feedstocks can be incinerated, which offers a posi­tive energy return as well as the recovery of minerals. Before its incineration, the stillage should be concentrated up to 50 to 60% solids in 4- or 5-effect evapora­tors. Just the combustion of stillage offers the energy needed for this concentration process. The incineration ash has about 30 to 40% K2O and 2 to 3% P2O5, which converts it into a fertilizer after its dilution in water and neutralization with sulfu­ric acid (Nguyen, 2003; Olguin et al., 1995; Sheehan and Greenfield, 1980). The burners of stillage require special designs in order to support its high ash content.