Bioactive antioxidant additives from agro‐residues: Enhancing biodiesel stability for diesel engine applications

Abstract

Biodiesel from renewable sources, such as Prosopis juliflora Methyl Ester (PJME), offers a viable alternative to fossil fuels but is limited by poor oxidation stability. This study examines that adding essential oils as antioxidants derived from agricultural waste, particularly Citrus aurantifolia L. (CA) at 4% concentration, can significantly extend the oxidation stability of PJME from an initial Induction Period (IP) of 2.64 h to 11.2 h over 60 days, ensuring the fuel to meet EN14214 standards. The antioxidant ranking at 4% showed CA as most effective, followed by TBHQ, CL, and EC. Importantly, TBHQ was only as effective as CA at higher concentrations, but less effective at the lower concentrations. This research is distinctive for investigating the influence of antioxidant‐enriched aged biodiesel‐diesel combinations in a compression ignition engine (CI), a topic that is rarely examined. Incorporating 4% CA to B10‐B40 compositions improved IP across all tested blends, with B30 + 4CA achieving good results. Detailed engine testing revealed that the aged B30 blend with 4% CA (B30 + 4CA‐60d) demonstrated a 7.6%–9.4% gain in BTE and a 9.8%–16.7% drop in BSFC when compared to aged B30 without antioxidants. Additionally, CO emissions decreased by 37.5%, while NOx emissions were reduced by 16.3% at high load. Combustion data demonstrated that B30 + 4CA maintained cylinder pressure and heat release rates similar to fresh B30, showing that the CA antioxidant effectively prevented oxidative degradation. These key results underscore the potential of agro‐waste‐derived essential oils as sustainable, cost‐effective antioxidant additives for enhancing biodiesel stability and optimizing engine performance.