The present work describes the preparation of producer gas and biogas from waste biomass material and its application in a twin cylinder dual-fuel diesel engine to study their performance and emission characteristics by the fractional replacement of fossil diesel in dual-fuel mode. Experiments are carried out both in diesel mode as well as dual-fuel mode operation under different engine loads. Comparative outcomes of performance and emission parameters for both modes of operations are presented. The study reveals that dual-mode operations show lower performance characteristics but better control of emission parameters like nitric oxide (NO) and smoke opacity compared to diesel mode. The hydrocarbon emission of producer gas-diesel and biogas-diesel was found to be 65.8% and 109.7% respectively, higher than diesel mode at the optimum load of 8 kW. Similarly, brake thermal efficiency of dual-mode operation of producer gas-diesel and biogas-diesel was 2.47% and 1.67%, respectively, lower than diesel mode. The pilot fuel savings percentage achieved was 85.5% in biogas-diesel and 83% in producer gas-diesel operation at the same loading condition. Further, comparing biogas with producer gas, it was observed that some of the emission parameters like carbon monoxide CO and NO were better controlled by biogas than producer gas whereas, HC and smoke emissions were better controlled by producer gas than biogas. © 2020, The Brazilian Society of Mechanical Sciences and Engineering.