|LEPAK, GREGORY - Bioprocess Design Services|
|SHARP, JULIA - Clemson University|
|THORNTON, C - Clemson University|
|WALKER, TERRY - Clemson University|
Submitted to: International Journal of Sustainable Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2016
Publication Date: 11/18/2016
Publication URL: http://handle.nal.usda.gov/10113/5832878
Citation: Lepak, G.S., Moser, B.R., Bakota, E.L., Sharp, J., Thornton, C.D., Walker, T. 2016. Improved oxidative stability of biodiesel via alternative processing methods using cottonseed oil. International Journal of Sustainable Engineering. 10(2):105-114.
Interpretive Summary: This research revealed that modifications to traditional processing enhanced the oxidative stability of biodiesel prepared from cottonseed oil. Cottonseed oil contains a natural antioxidant, gossypol, that is not present in other vegetable oils. However, biodiesel produced from cottonseed oil normally does not contain gossypol because the gossypol is lost during processing. In addition, poor oxidative stability is one of the major drawbacks of biodiesel relative to conventional petroleum-derived diesel fuel. Therefore, retention of natural antioxidants would be especially beneficial in the case of biodiesel. The objective of the current study was to explore methods to retain gossypol in cottonseed oil-derived biodiesel. 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 new biodiesel production method was described that exhibits enhanced oxidative stability. 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 America.
Technical Abstract: Biodiesel from waste cooking oil (WCO) requires antioxidants to meet oxidation stability specifications set forth in ASTM D6751 or EN 14214. In contrast, unrefined cottonseed oil (CSO), containing tocopherols and gossypol, produces biodiesel of higher oxidation stability. However, only a portion of these CSO endogenous antioxidants are suspected to be retained in biodiesel. Because the economics of biodiesel manufacturing rely upon inexpensive sources of triglycerides, emphasis was placed on developing improved alternative processing methods where WCO was the main source of methyl esters (WCOME) and CSO was used as a supplemental source of triglycerides and antioxidants in a 4:1 ratio. This study compared four processing methods for their ability to produce biodiesel of increased oxidative stability prepared from a 4:1 ratio of WCO:CSO. Two novel processing methods developed for this study utilise solvent properties of fatty acid methyl esters and glycerol to avoid additional chemical inventory for biodiesel processors. This study concludes that the two new processing methods resulted in biodiesel that had statistically significant improved oxidation stability when compared to two common industrial processing methods. Another significant finding is that high-shear homogenisation during transesterification reduced reaction time from the published one hour to 16 minutes.