An evaluation of Korean food waste composting, with a fed-batch operation, was conducted using the properties of the exhaust gas condensate. The traditional indices, as well as condensate properties, showed the same patterns of variation over each reaction time in the batch cycles during fed-batch composting. Trends for the variation in the pH of the condensate (pH(cn)) corresponded to those of the traditional indices. such as pH of the compost (pH(cm)) and CO2 evolution in the exhaust gas. In addition, the carbon chemical forms in the condensate would indirectly represent the gaseous metabolites, such as CO2, NH3, and VFA, which are generally emitted from aerobic composting processes. The patterns and quantities of NH3 gas evolution in the exhaust gas, especially, could be effectively estimated by their correlations with the NH4 and NH3 concentrations in the condensate or the pH(cn) in each cycle of fed-batch composting. Therefore, it was considered that the measurement of the condensate properties might serve as more useful and convenient operating indices than the analysis of solid and gas samples. during the composting process. (C) 2003 Elsevier Ltd. All rights reserved.