Influence of CeO₂ nanoparticle addition on engine performance, combustion, and emissions of ethiopian podocarpus falcatus biodiesel

Abstract

The identification of region-specific, non-edible biodiesel feedstocks is critical for expanding sustainable fuel use without competing with food resources. This study reports the first comprehensive evaluation of engine performance, combustion behavior, and emissions of Ethiopian Podocarpus falcatus biodiesel enhanced with low-dose cerium oxide (CeO₂) nanoparticles in a compression ignition engine. Biodiesel–diesel blends containing 10–30% biodiesel was tested with and without 80 ppm CeO₂. Increasing biodiesel content alone reduced brake thermal efficiency from 54.7% for diesel to 49.2% for B30 and decreased brake power from 4.44 to 3.86 kW at full load. The addition of CeO₂ effectively mitigated these penalties, increasing brake thermal efficiency by up to 11.7% and restoring brake power by 3–10% across all blends, while brake specific fuel consumption decreased by 54–56% relative to untreated fuels under identical conditions. Combustion analysis showed higher peak cylinder pressure up to 71.2 bar, enhanced premixed heat-release rate reaching 130.2 J per °CA, advanced combustion phasing by 2–3 °CA, shortened ignition delay by about 2 °CA, and reduced combustion duration by 3–4 °CA. Emission measurements indicated substantial reductions in carbon monoxide by 7.5–16.7%, unburned hydrocarbons by up to 70.2%, and smoke opacity by 9–10%, accompanied by a moderate increase in NOx emissions of approximately 7% at full load due to higher combustion temperatures. Overall, the results demonstrate that low-dose CeO₂ nanoparticles can effectively offset biodiesel-induced performance losses while enhancing combustion and emission characteristics, highlighting Podocarpus falcatus as a promising and sustainable biodiesel feedstock for high-efficiency compression ignition engine operation without hardware modification. © The Author(s) 2026.