Exergy is a relatively new concept and its primary use is to analyze processes for energy inefficiencies. Further, by definition, exergy is a measure of the deviation of a system from the environmental state. By choosing an appropriate environmental state, exergy can be used to “measure” the pollution to the environment. This intuitive notion guided many researchers to propose quantitative methods that could express pollution in exergy terms for comparing pollution effects of processes. In this paper a method based on the environmental negative effect, which is an index that accounts environmental effects based on the exergies of the wastes is discussed. For the calculation of the exergy, the exergy of mixing substitutes the physical and chemical exergy conventionally used. Exergy of mixing is that portion of the chemical exergy, which is due only to material transfers or changes in composition. The method is applied in a coal (anthracite) fired steam boiler and environmental pollution is evaluated either with the use of total exergy and exergy of mixing. Results for anthracite are compared with methane as an alternative fuel and differences in pollution potentials are discussed.