Biodiesel production from raw castor oil

A preliminary assessment of castor plant adaptability at Northern Portugal was performed, together with the evaluation of the extracted raw oil, without any refinement, for biodiesel production. Castor was seeded, plants grew and seeds were manually harvested after 2 years. Mechanical and chemical oil extraction procedures were evaluated. Biodiesel was produced by homogenous alkaline transesterification and experimental planning was conducted to evaluate the influence of temperature and reaction time in product yield and quality; 20 experiments were performed. A 54.1% (w/w) oil yield was obtained by Soxhlet extraction with methanol after grinding the seeds. Product yield ranged from 43.3 to 74.1% (w/w), biodiesel quality varied and the conditions that lead to the best product were established. Results indicate that, to achieve higher product yields and quality using raw oil, longer reaction times are required compared to what is generally reported for refined oil. Statistically significant predictive models were obtained to estimate product yield and quality as function of the studied reaction variables. The best temperature and reaction time to produce biodiesel from raw castor oil were 65 °C and 8 h, where models predict a product yield of 73.62% (w/w) and a purity of 83.41% (w/w).