The current experimental study is an effort to reduce the engine out emissions from compression ignition (CI) engines powered by a combination of renewable liquid and gaseous fuels. Hydrogen (H2) is a clean burning fuel and seems a very popular gaseous fuel for CI engine applications as it can replace large amount of liquid-injected pilot fuels in dual fuel (DF) engines. The study investigates the effect of hydrogen fuel flow rate (HFFR) along with honge biodiesel (BHO) or cotton seed biodiesel (BCO), fuel injection timing (IT) and exhaust gas recirculation (EGR) on engine performance, engine out emissions and combustion of a OF engine. In the first part the maximum possible HFFR was obtained for smooth operation of DF engine. In the second part the liquid fuel IT for better brake thermal efficiency (BTE) was obtained. In the third part the effect of EGR on the performance of DF engine was studied. The study showed that the maximum possible HFFR was 0.22 kg/h with a knock free operation. The fuel IT of 27 before top dead center (bTDC) at a fuel injection pressure (IP) of 240 bar yielded better results. When EGR of 15% was inducted, 23-24% lower BTE, 22-28% higher smoke, 38-40% higher hydrocarbon (HC), 31 -38% higher carbon monoxide (CO) were noticed with biodiesel fuels (BDFs) at optimum operating conditions for 80% load. But the oxides of nitrogen (NOx) emissions from the engine decreased by 26-28% with BDFs at optimum operating conditions for 80% load as compared to the CI mode. (C) 2018 Elsevier Ltd. All rights reserved.