Performance and emission analysis of sterculia foetida biodiesel enhanced with butanol: Combustion efficiency and emission mitigation

• Enhanced oxidative stability and fuel quality, meeting ASTM D6751 standards. • Significant reduction in CO, UHC, and smoke emissions with butanol-enriched blends. • Slight increase in NOx emissions due to higher combustion temperatures from oxygen-rich butanol. • Optimization needed to improve brake-specific energy consumption for better fuel efficiency. This research endeavors to explore the viability of Sterculia foetida biodiesel (SFB) as a renewable feedstock for biodiesel synthesis, accentuating the novel application of butanol as a co-solvent to optimize engine functionality and emission profiles. The biodiesel was produced through a bifurcated catalytic method encompassing acid esterification to diminish free fatty acids (FFAs), succeeded by alkaline transesterification, which accomplished a conversion efficiency of 95.2%. Mixtures of SFB incorporating 10% and 20% butanol (SFB90B10 and SFB80B20) were assessed within the operational parameters of diesel engine functionality. The elevated oxygen content and energy density of butanol augmented combustion efficacy, with SFB80B20 exhibiting a 4% enhancement in brake thermal efficiency (BTE) alongside a 3.5% decrease in brake-specific fuel consumption (BSFC). Emission assessments indicated a reduction of 6.2% in carbon monoxide (CO), 7.1% in hydrocarbons (HC), and 5.5% in smoke opacity for SFB80B20, countered by a slight increase in nitrogen oxides (NOx) of 2.2%. These results address significant deficiencies in biodiesel scholarship by demonstrating the potential of Sterculia foetida as a feedstock and elucidating the contribution of butanol in improving performance and sustainability. This investigation plays a pivotal role in the progression of biodiesel formulations aimed at more environmentally friendly and efficient diesel engine applications.