A simple method to estimate the fuel ratio ( = (Fixed carbon)/(volatile matter)) as a combustion index of char obtained from the pyrolysis of municipal waste (MW) by a waste disposal facility was developed, based on the data for the pyrolysis of cellulose (CE), polyethylene (PE), polypropylene (PP), polystyrene (PS) and poly(vinyl chloride) (PVC). Pyrolysis reactions involved were explained by thermal analysis. Interactions during the pyrolysis were confirmed to take place only between CE and PVC. The mechanism for the pyrolysis of CE with PVC was studied by using TG-MS, FT-IR and results from other studies. The pyrolysis of MW was conducted using a rotary kiln (20 t MW/day). The fuel ratio of char was estimated by thermal analysis using a PVC/CE mixture to represent biomass, and PE, PP and PS to represent plastics, with consideration to the elemental composition of MW. The fuel ratio was found to depend on biomass and plastics quantities in MW as well as on pyrolysis temperature, and was in agreement with the theoretical estimation. (C) 2004 Elsevier Ltd. All rights reserved.