District heating in Ljubljana is based on as great use of combined production of heat and electric power in TE-TOL as possible. Different coal varieties are used for fuel. Being given that an enormous part of production uses this source of energy, coal variety of utter importance for environment pollution. The following two diagrams clearly show the influence of various coals on air pollution with SO2, the ratio between sulphur contents in Trbovlje coal and that from Indonesia is as much as 9:1; a different coal variety in itself decreases air pollution with SO2 by 9-times. Similar ratios apply for ash contents, which also has influence on the decrease of dust particles in air as well as on the decrease of ash tips and transport in city streets.