Evaluation of dominant parameters in lipase transesterification of cottonseed oil

Authors: ANDERSON, STANLEY - Clemson University; WALKER, TERRY - Clemson University; Moser, Bryan

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2019
Publication Date: 2/28/2019
Citation: Anderson, S.T., Walker, T., Moser, B.R., Drapcho, C., Zheng, Y., Bridges, William. 2019. Evaluation of dominant parameters in lipase transesterification of cottonseed oil. Transactions of the ASABE. 62:467-474.

Interpretive Summary: This research revealed that crude cottonseed oil can be directly converted into biodiesel in one step using a lipase catalyst as opposed to the conventional two step procedure. Typically, crude vegetable oils must be pretreated before they can be converted into biodiesel because they contain components that are incompatible with the conventional catalyst. In this work we demonstrated that high yields of biodiesel (>98%) can be obtained from crude cottonseed oil containing high amounts of moisture and free fatty acids using enzymatic catalysis. Ordinarily, crude cottonseed oil must be dried to remove moisture and pretreated with sulfuric acid and methanol to lower the free fatty acid content to a level acceptable for subsequent alkaline-catalyzed transesterification. These results will be important to cottonseed producers, biodiesel producers, distributors, and end-users (customers), as well as petroleum companies and manufacturers of diesel engines because a biodiesel production method was described that avoids feedstock pretreatment. This research may ultimately improve market penetration, availability, and public perception of domestically produced alternative diesel fuels, thus affording greater independence from imported petroleum-based fuels while simultaneously enhancing economic opportunities across rural America.

Technical Abstract: Eversa Transform was used as an enzymatic catalyst to transform glandless and crude (heavy pigment) cottonseed oils into biodiesel. The oils were reacted with methanol at a 6:1 molar ratio with modified amounts of water, lipase, and temperature. Reactions were conducted in the presence of lipase and water at doses of 2, 5, and 8 wt% and 1, 3, and 6 wt%, respectively. Product composition and conversion were determined using the gas chromatography method of ASTM D6584. Oxidative stability was determined following EN 15751. The conversion to fatty acid methyl esters averaged 98.5% across all samples. Lipase and water dosages did not affect conversion, while each had an effect with temperature that was significant across the difference between 3 and 1 wt% water content and between 8 and 5 wt% enzme content between the two temperatures (p = 0.0018 and 0.0153), respectively. Induction periods (oxidative stability) of the glandless and crude cottonseed oils were significantly different, but there was no difference between the two oil conversions based on oil type.