By the rise in population, the usage of non-renewable fuels is increasing. It led to the depletion of fossil fuels and other environmental issues. Reducing the usage of fossil fuel, enhancing performance and reducing emissions are the key areas in this research. In this experiment, a conventional single cylinder CI engine is used in dual fuel mode. In dual fuel mode, biogas is used as primary fuel and biodiesel (Palm oil) with various butanol blending ratios (10%, 20% and 30%) is used as pilot fuel. Various properties like flash and fire point, cloud and pour point, viscosity, density, calorific values are measured. Biogas flow rate and applied load are varied for each blending ratio. The effects of load, butanol blending ratio and biogas flow rate on BTE, BSFC, HC, CO and NOx emissions are analyzed and compared with diesel-only mode. Biodiesel with 30% butanol blend in dual fuel mode shows better brake thermal efficiency at 12 lpm flow rates. All test cases prove 12 lpm is better than 16 lpm biogas flow rates. Increase in biogas flow rate reduces NOx emissions. However, it increases HC and CO emissions. And this investigation proposes to intervene in the dual fuel biogas-biodiesel engine at 12 lpm biogas rate of flow. © Published under licence by IOP Publishing Ltd.