Experimental Investigation of Adding Antioxidants into the Algae Biodiesel Blend as a Diesel Engine Fuel

This study investigates the use of a blended fuel composed of 20% microalgae-based biodiesel and 80% conventional diesel (by volume) as a sustainable alternative for compression ignition (CI) engines. While this biodiesel-diesel blend offers environmental benefits, it results in slightly increased emissions of nitrogen oxides (NOₓ) compared to pure diesel. To address this issue, antioxidants were incorporated into the fuel blend to reduce NOₓ emissions and enhance storage stability. Pure biodiesel is prone to thickening in cold climates and can promote oxidative degradation of metal storage tanks; the addition of antioxidants helps mitigate these challenges by improving oxidative resistance.Experimental evaluations were conducted using standardized testing procedures defined by the American Society for Testing and Materials (ASTM) under varying engine loads. Performance and emission characteristics—specifically carbon monoxide (CO), nitrogen oxides (NOₓ), and brake thermal efficiency (BTE)—were analyzed. Results showed significant emission and performance improvements: NOₓ emissions were reduced by 1070 parts per million (ppm) at a retarded injection timing of 20 degrees before top dead center (BTDC) using 250 ppm of butylated hydroxytoluene (BHT) and 500 ppm of pyrogallol (PY). CO emissions decreased by 0.02% at a normal injection timing of 20° BTDC without antioxidants. Additionally, a 35% increase in BTE was observed at normal injection timing of 23° BTDC with 500 ppm of antioxidants, under full-load conditions with the B20 blend. These findings highlight the combined effectiveness of antioxidant additives and optimized injection timing in enhancing both engine performance and emission control.