Production of biodiesel via the in situ transesterification of grain sorghum bran and DDGS

Authors: Wyatt, Victor; Jones, Kerby; Johnston, David; Moreau, Robert

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2018
Publication Date: 6/1/2018
Publication URL: https://handle.nal.usda.gov/10113/6472305
Citation: Wyatt, V.T., Jones, K.C., Johnston, D., Moreau, R.A. 2018. Production of biodiesel via the in situ transesterification of grain sorghum bran and DDGS. Journal of the American Oil Chemists' Society. 95:743-752.

Interpretive Summary: To increase global production of biofuels, many alternative feedstocks are needed. Additionally, the economics of many of the processes by which biofuels are made, particularly biodiesel, need to be improved to make the fuels affordable to the general population. Biodiesel is a renewable fuel that is becoming widely accepted as a replacement or additive for petroleum-based diesel fuel. The in-situ transesterification method is potentially a cost and energy-saving process by which biodiesel can be produced directly from oil bearing feedstocks rather than from extracted oils. This study was performed to test the applicability of the in situ transesterification method on two alternative feedstocks: grain sorghum bran and grain sorghum distillers dried grains and solubles (DDGS). Sorghum bran is a coproduct that is removed before ethanol fermentation and DDGS is a coproduct produced after fermentation of grain sorghum seeds. Both feedstocks contain approximately 10% oil. This study proves that the in-situ transesterification process can successfully produce biodiesel from the oil in sorghum bran and sorghum DDGS. Successful utility of this process will benefit both, the ethanol and biodiesel industries, and grain sorghum farmers.

Technical Abstract: The acylglycerides in sorghum bran and distiller’s dried grains and solubles (DDGS) from sorghum post-fermentation stillage have been converted to fatty acid methyl esters (FAMEs) using an in-situ transesterification (IST) method. The reactions were conducted at 25 deg C or 40 deg C in the presence of 2.4 or 4.8 mmol of NaOMe dissolved in 6.4 or 12.8 mL MeOH. The experimental results confirmed that reducing the moisture to approximately 2% (w/w) within the feedstock was necessary for the reaction to proceed. All of the reactions were monitored by HPLC and all performed better at 40 deg C than 25 deg C. The most successful reactions used 4.8 mmol NaOMe dissolved in 12.8 mL MeOH producing up to 98.3% FAME when sorghum bran was used as the feedstock. When DDDS from sorghum stillage were used as the feedstock, the yield averaged 32.2% under the previously established optimal conditions.