Emission characteristics of a diesel engine in diesel alone and dual mode (with producer gas) at different load conditions are presented in this paper. Concentration of pollutants such as carbon monoxide (CO), oxides of nitrogen (NOx), sulphur dioxide (SO2), hydrocarbons (HC) and particulates in the flue gas were monitored and emission factors have been derived. In addition to the emission characteristics, diesel replacement rate at different loads has been estimated. It was observed that the emissions increase at low-load conditions. It has been found that CO content in the flue gas increase in dual fuel operation, more so at part loads. NO, and SO2 concentration decrease in dual fuel mode. (C) 2004 Published by Elsevier Ltd.