<p>The use of biocatalysts, derived from biomass, bones, fruits and vegetables, is recently investigated by researchers to overcome the energy and environmental issues posed by traditional catalysts. This research investigates the effects of three biocatalysts, derived from potato, lemon, and citrus limetta peels, for the biodiesel production from waste cooking oil (WCO) and the evaluation of engine performance and emission characteristics of the WCO biodiesel blends with or without the addition of hydrogen fuel as the secondary fuel additive. Peels of potato (BC1), lemon (BC2), and citrus limetta (BC3) were used to make the biocatalysts, which were characterized using EDX and SEM. The biodiesel was produced using transesterification of WCO by mixing methanol and biocatalyst in a biodiesel reactor. The biodiesel yield and properties were tested to meet the standards. The engine performance and emission characteristics of WCO biodiesel blends were evaluated by varying the engine load (0, 25, 50, 75 and 100% of full load) and the hydrogen flow rate (0, 3, 6 and 9 lpm) in a single-cylinder 5.2&#xa0;kW Kirloskar engine. EDX and SEM studies revealed that the potato peel catalyst exhibited the maximum biodiesel yield of 95%. Experimental results revealed that the BC1WC20 blend reduced CO emissions by 10% while reducing HC and CO₂ emissions by 8.3% and 5%, respectively. With the addition of hydrogen of 6 lpm, the emissions of HC and CO₂ further dropped by 12.8% and 7.4%, respectively. Furthermore, the hydrogen-enhanced BC1WC20 blend demonstrated a 19% improvement in BTE. Overall, the research showed that the vegetable peel biocatalysts, derived from the peels of potato, lemon and citrus limetta, have high potential to improve the biodiesel yield at reduced cost, and the biodiesel in combination with hydrogen could reduce pollutant emissions and improve engine efficiency.</p>