AbstractBiogas has great potential as a clean alternative fuel for dual-fuel diesel engines. The present work is aimed at investigating the operating parameters such as compression ratio (CR) and injection timing (IT) for a dual-fuel diesel engine run on biogas and rice-bran biodiesel. The motivation behind this investigation is to obtain a diesel equivalent performance together with a reduction in emission. To achieve this, a single-cylinder, direct-injection, variable-compression-ratio diesel engine is modified into a dual-fuel diesel engine by incorporating a venturi gas mixer at the inlet manifold. A set of combinations composed of CRs of 17, 17.5, and 18 and ITs of 23°, 26°, 29°, and 32° before top dead center (BTDC) at different loading conditions are considered. The combination of IT=32° BTDC and CR=18 is found to produce a maximum brake thermal efficiency of 25.88% and a liquid fuel replacement of 82.75% at 100% load. On average, there is a reduction of carbon monoxide as well as hydrocarbon emiss...