The aim of the study is to reduce the environmental impact of ash deposits. Ash from coal and biomass combustion, containing uranium and thorium from Yatagan-Silopi and Tuncbilek coal; cesium-137 from forests in northeastern Turkey and central Sweden. Turkey is dependent on coal for power generation and huge volumes of ash (>15 Mton/yr) are produced every year. Because of that certain coals, in particular Yatagan, with known problems from Mo and U leaching to the ground water, and Silopi oil shales/asphaltites were studied. Biomass ash comes from branches, bark and other unused parts of the trees and plants. This ash has low concentration of environmentally hazardous metals, but {sup 137}Cs is a problem in certain regions and it is of interest to investigate the possibilities to leach this metal from the ash. Washing ash through rapid chemical leaching at low pH reduces the slow release of metals from ash due to precipitation and besides it may lead to metal recovery from the ash. Initial experiments were done in batch form, in which the neutralizing capacity at pH 1-1.5 was measured by adding sulfuric acid to maintain pH for mixtures of ash and water. Subsequent experiments were done in bench scale. The process also reduced the metal content of the ash, due to chemical leaching of metal oxides and ion exchange at the surfaces of stable oxides. This means that treated ash will not release further metals and, eventually, relaxes the requirements on depositories and allows the ash from coal to be used as an admixture in cement, and to be used as a fertilizer following after treatment of ash from biomass