The facility for analysis of chemical thermodynamics (F*A*C*T) method based on the Gibbs energy minimization principle was used for the environmental assessment of coal combustion in O-2+CO2 mixture compared with that in air. For the former case, the calculations predict higher emissions of CO and lower emissions of NOx. For both combustion media, SOx emissions are governed by O-2 concentration, whereas distribution of trace metals was unaffected when O-2 concentration in the O-2+CO2 mixture approached that in air. The effect Of O-2+CO2 mixture on the distribution of chlorine- and alkali-containing compounds in the vapor phase was minor compared with that in air. In spite of the large excess of CO2 in combustion medium, sulfation was the predominant reaction occurring in ash. (C) 2003 Elsevier Science B.V. All rights reserved.