Environmental Geochemistry with specialization to energetic puroposes. Trace elements in fosil fuels and biomass – the diference in composition and behaviour. The main differences in composition on main elements and geochemical character of ash in fosil fuels and biomass. The behaviour of alcalic elements during combustion processes. Geochemistry of energetic products from combustion and other thermal technologies. Geochemical classification of ash, trace elements in fly ash and product of pyrolysis. The index of enrichment of trace elements. The mobility of trace elements during waste leaching in different pH conditions. The concentration of main elements in relationships to the melting point temperature of ash.