Optimization of spark-ignition engine characteristics fuelled with oxygenated bio-additive (triacetin) using response surface methodology

Biodiesel, as an alternative fuel, has gained wide interest in recent years. However, despite the countless benefits, the enormous generation of glycerol-waste and higher production costs have been causing severe challenges to both the environment and the biodiesel economy’s survival. With the focus on maintaining its sustainability, the proper valorization of the crude glycerol is of vital importance. The objective of the present study is to harness and transform glycerol (a by-product of biodiesel) to triacetin and utilize it further as a fuel additive for spark ignition (SI) engine. Triacetin is a valuable compound of bio-based origin, having good anti-knock properties and higher oxygen content. Test fuels containing different blends of gasoline, methanol and triacetin were prepared and compared with neat gasoline. The Response Surface Methodology (RSM) based multi-objective technique was selected to optimize the engine output parameters like BTE, CO, CO₂, HC and NOx emissions. The results indicate that the engine operating at 1.17 kW brake power and containing 90.73% gasoline, 4.94% methanol and 4.31% triacetin (by vol.) were found to be the optimum input parameter combinations which shows maximum BTE and lowest engine exhaust emissions as compared to other fuel blends. The estimated economic analysis of small-scale plants was also carried out, revealing that about 4.2% of revenue per kg of triacetin selling can be generated by running biodiesel and triacetin production analogously. Among various alternatives probed, the acetylation of glycerol to triacetin appears to be the ideal solution. It can serve the multiple purposes of reducing vehicular emission and improving the economic viability of burgeoning biodiesel industries and creating new opportunities, livelihoods, and jobs for humanity.