A large collection of well-characterized coals, documented in the Center for Applied Energy Research's (CAER) database, was used to estimate the CO2 content of maceral concentrates from Kentucky and Illinois high volatile bituminous coals. The data showed no correlation between CO2 versus coal ranks and between CO2 versus maceral content. Subsequently, eight sets of low-ash density-gradient centrifugation (DGC) maceral concentrates from five coal beds were examined, spanning in the high volatile rank range. Heating value was not determined on the concentrates, but instead was calculated using the Mott-Spooner formula. There was a good correlation between predicted CO2 and maceral content for the individual iso-rank (based on vitrinite reflectance, analyzed on whole (parent) coal) sets. In general, the predicted CO2 increases from liptinite-rich through vitrinite-rich to inertinite-rich concentrates (note: no "concentrates" are absolutely monomaceral). (C) 2003 Elsevier Science B.V. All rights reserved.