A first-time UCG modeling approach for coupled synthesis gas quality and tar production analyses is introduced.

Main UCG chemical sub-processes, operating parameters and tars down to single pollutant level are considered.

The model is successfully validated against available literature data.

Mixing of different sub-process related gas fractions and affiliated cracking leads to reduced tar yields in synthesis gas.

Best-fit future prognoses in plan regarding reachable UCG gas qualities at simultaneously reduced tar production.