Optimized biodiesel production from Maesa lanceolata seeds and its emission analysis: A sustainable non-edible feedstock for renewable energy

The reliance on edible feedstocks for biodiesel production raises concerns about food shortages, driving the search for sustainable alternatives. This study investigates Maesa lanceolata, a non-edible and scarcely exploited feedstock abundant in East, Central, and South Africa, Madagascar, and southern Asia, as a biodiesel source. Oil was extracted using solvent techniques, achieving a yield of 32.2 %. Biodiesel was synthesized via transesterification with methanol and an alkali catalyst, and process optimization was conducted using the response surface method (RSM) with central composite design (CCD). A quadratic model predicted biodiesel yield with an adjusted R² of 0.9766, confirming model accuracy. Optimal transesterification parameters were the methanol-to-oil molar ratio of 6:1, the reaction time of 60 min, the temperature of 60 °C, and the catalyst concentration of 1.5 wt%, yielding 92.33 % methyl esters experimentally. Gas chromatography-mass spectrometry (GC-MS) identified fatty acid esters, and the biodiesel met EN 14214 and ASTM 6751 standards. Emissions tests for CO, CO₂, HC, and NO_x were conducted at variable speeds and constant load using a single-cylinder, 4-stroke, 7.5 kW compression ignition engine. The results showed that B20 performed best, with CO₂ emissions decreasing from 1.3 % to 0.8 %, HC emissions dropping from 10.5 % to 7.1 %, and CO emissions reducing between 22.8 % and 24.1 % compared to B0. However, B10 showed the smallest increase, with NO_x rising from 10.0 % to 5.1 % within the same speed range. This study highlights the potential of Maesa lanceolata biodiesel to substitute diesel fuel while diversifying feedstocks and contributing to sustainable biodiesel production.