Biodiesel production from Jathropha curcas l. oil using chemical or enzymatic catalysts

Doutoramento em Engenharia dos Biossistemas - Instituto Superior de Agronomia - UL

Jatropha curcas L. is a tropical shrub, belonging to the Euphorbiaceae family, well adapted to marginal lands, not competing for arable land and food chain. The seeds are rich in non-edible oil, suitable for biodiesel production. In this work, variation in oil content and composition of Jatropha seeds from 12 origins, grown in Mozambique under the same edapho-climatic and agronomic conditions, was assessed. Oil contents varied from 37%-45% (d.w.). The major fatty acids identified in Jatropha oil were oleic (41.1%) and linoleic acids (38.8%). The oil presented low acidity and low levels of oxidation products, proving adequate for biodiesel production. Also high levels of gamma-tocopherol were found (69-182 mg/kg). The presence of this antioxidant may explain the high oxidative stability presented by the oil during the storage tests performed under controlled humidity and temperature, simulating tropical climate conditions. Conversely, seeds storage under the same conditions promoted the growth of fungi responsible for oil degradation. Therefore, it is better to extract the oil and store it in closed containers, than to store the seeds. Dry conditioning of seeds to be extracted by screw pressing was optimized via Response Surface Methodology (RSM). The highest extraction oil yields (88%, w/w) were obtained with seeds dried at higher temperatures for shorter periods of time (e.g., 90◦C/10-20 min; 80◦C/30 min) or at lower temperatures for longer periods of time (e.g., 60◦C/50-60 min). RSM was also applied for the optimization of fatty acid methyl esters (FAME, biodiesel) production from Jatropha oil, using sodium methoxide as catalyst. Finally, the feasibility of enzymatic production of Jatropha FAME, using recombinant sn-1(3)-regioselective Rhizopus oryzae lipase and Carica papaya lipase and Candida parapsilosis lipase/acyltransferase, immobilized on different synthetic resins, was evaluated. All biocatalysts proved to be efficient and environmentally friendly alternatives to the conventional chemical process.