Purpose. To conduct an ecological estimation of calorific value for two alternative energy sources: traditional coal combustion and heat recovery from geothermal modules. Methodology. The methods of comparative analysis for environmental impact of energy production due to coal use in comparison with the alternative of using geothermal modules and heat pumps are used. The technique for gross emissions estimation from coal combustion processes for the conditions of Donbas mines and equivalent volumes of potential energy from heat pumps is applied. Findings. The ecological estimation of geothermal modules as alternative sources of thermal power on a territory of liquidated mines of Donbas is performed. A comparative estimation of the potential for thermal energy production by coal combustion and using geothermal modules is performed based on the analysis of average characteristics of coal in the Donetsk basin, as well as a calorific value of fuel. The parameters necessary for technical and economic estimation of the efficiency of implementing geothermal modules for providing alternative heat supply are calculated. Originality. For the first time, a comparative estimation of the potential for thermal energy production by coal combustion and using geothermal modules has been performed based on analysis of average coal characteristics in the Donetsk basin, as well as a calorific value of fuel. Equivalent mass of coal, which can be preserved due to the operation of geothermal modules for conditions of liquidated mines of Donbas and mines of Selydove group, is calculated according to the values of additionally obtained thermal power of geothermal modules Pth. Practical value. According to the calculations, the amount of geothermal power Uth from mine water in terms of equivalent mass of coal during the heating season is estimated as 7.63 1061.76 108MJ for open geothermal systems based on mine water discharge in Donbas; 0.49 1060.57106MJ for modules of geothermal circulation of Selydove group of mines. It is proven that the implementation of geothermal modules for thermal energy production in operating and closed coal mines is a promising environmentally friendly technology with long-term technological potential, economic and social benefits.