Utilization of waste plum stones as a source of oil and catalyst for biodiesel production

Possibilities of using waste plum stones in biodiesel production were investigated. The plum kernels were used as a source to obtain oil by the Soxhlet extraction method, while the whole plum stones, the plum stone shells that remained after the crashing, and the plum kernel cake that remained after the oil extraction, were burned off to obtain ashes. The collected ashes were characterized by elemental composition, porosity, and base strength and tested for catalytic activity in transesterification of esterified plum kernel oil. Dominant elements were potassium, calcium, and magnesium at different contents in the three obtained ashes. The most active catalyst was the plum stone shell ash, so the effect of temperature (40, 50, and 60 degrees C) on the reaction rate was investigated. The reaction rate constant increased with the reaction temperature with the activation energy value of 58.8 kJ mol-1. In addition, the plum stone shell ash can be reused as a catalyst after recalcination.