Optimizing the Extraction of Oils from Date Seeds for Biodiesel Production

Abstract

Increasing attention has been recently focused on producing biodiesel from non-edible organic materials to avoid competing on food sources. The focus of the present work is to assess the possibility of extracting oils from date seeds (DS), which is a waste biomass that can then be used in biodiesel production. Two cultivars of local date seeds, namely, Khalas and Allig, have been used. Oil was extracted by Soxhlet and Folch methods from DS particles in five size ranges (300 nm, 0.1–0.3 mm, 0.3–0.85 mm, 0.85–1.18 mm, and > 1.18 mm) and compared to ungrounded DS. The size of the DS particles was found to have a clear effect on the oil extraction yield percentage (OEYP), which increased with the decrease in the particles size, excluding the nano-particles at which the OEYP reduced. The maximum OEYPs were achieved from Allig DS in the size range of 0.1–0.3 mm, which were 9.0 and 10.4%, using the Folch and Soxhlet extractions, respectively. The same size range, the maximum OEYPs, was also achieved from Khalas DS and was very close to those achieved from the Allig DS. The Soxhlet extraction was generally more effective than the Folch extraction in all size ranges. The difference in the effectiveness was minimum in the size range of 0.1–0.3 mm, and increased as the particles’ size increased. In the Folch process, the effects of the duration of main steps, namely, the ultra-sonication, orbital shaking, and centrifugation, on the OEYP, were evaluated. Using Allig DS in the size range of 0.1–0.3 mm, the effects of the times of ultra-sonication, above 1 min, and centrifugation on OEYP were insignificant, whereas the orbital shaking time had a slight negative effect. This work provides important information of the extraction process of oils from DS, and brings their use for biodiesel production closer to commercialization.