J Am Oil Chem Soc (2007) 84:963–970 DOI 10.1007/s11746-007-1119-4 ORIGINAL PAPER The General Applicability of in Situ Transesterification for the Production of Fatty Acid Esters from a Variety of Feedstocks Michael J. Haas Æ Karen M. Scott Æ Thomas A. Foglia Æ William N. Marmer Received: 29 January 2007 / Revised: 11 July 2007 / Accepted: 24 July 2007 / Published online: 23 August 2007 Ó AOCS 2007 Abstract We previously described a method for fatty presented here indicate that in situ transesterification is acid methyl ester (FAME) production wherein acylglycerol generally applicable to lipid-bearing materials, which transesterification was achieved by reacting flaked full fat could substantially increase the supply of biodiesel. soybeans with alkaline methanol to create a product that met ASTM specifications for biodiesel. In the present work Keywords Biodiesel Á Distillers dried grains Á we explore the general applicability of this approach, Fats and oils utilization Á Fatty acid ester Á termed in situ transesterification, to feedstocks other than In situ transesterification Á Meat and bone meal Á soybeans. Materials investigated were distillers dried Transesterification grains with solubles (DDGS), which is a co-product of the production of ethanol from corn, and meat and bone meal (MBM), a product of animal rendering. For both feed- Introduction stocks, reaction conditions giving maximum lipid transesterification were predicted by statistical experi- The production and use of fatty acid esters, particularly mental design and response surface regression analysis, methyl esters (FAME), as a fuel for compression ignition and then verified experimentally. Successful transesterifi- (diesel) engines is a rapidly growing technology that has cation was achieved at ambient pressure and 35 °C. For penetrated the transportation fuels sector in much of Eur- DDGS, partial drying markedly reduced the methanol ope and is in the process of doing so in the United States requirement to achieve a high degree (91.1% of maximum and other countries. Compared to petroleum-derived diesel theoretical) of transesterification. Elevated reaction tem- fuel, the use of biodiesel offers advantages of reduced peratures (to 55 °C was explored) caused little or no engine emissions of pollutants, domestic sourcing, and shortening of the time to completion. Protein was not renewability. removed from the DDGS during this treatment. For MBM, It is estimated that the United States produced and drying was not required to achieve a high degree (93.3%) consumed approximately 30 million gal of biodiesel in of transesterification. The remaining meal retained 2004 [1]. European consumption exceeded this value by at approximately 90% of the protein originally present. least tenfold. Biodiesel production is growing rapidly with Coupled with the previous work with soybeans, the data 2006 US production estimated to be 245 million gal and expected to exceed 700 million gal in 2015 [2]. A majority of biodiesel is produced from edible vegetable oils, soy- Mention of brand or firm names does not constitute an endorsement bean oil in the United States, and presently accounts for by the US Department of Agriculture over others of a similar nature not mentioned. approximately 10% of annual US soybean oil production if all was made from that feedstock. There is concern that at M. J. Haas (&) Á K. M. Scott Á T. A. Foglia Á W. N. Marmer anticipated future production levels the use of edible oils US Department of Agriculture, Agricultural Research Service, for fuel will compete significantly with food uses. This Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA would result in undesirable increases in both food and e-mail: [email protected] biodiesel costs, a particularly damaging occurrence in the 123 964 J Am Oil Chem Soc (2007) 84:963–970 case of biodiesel, which even at current prices, has diffi- through a 20-mesh screen and 24% passed through a 50- culty competing with petroleum fuel on an economic basis. mesh screen. Oven drying (77 °C) the DDGS to constant Feedstock expense is the major contributor to the cost of weight indicated 8.7 wt% moisture. Extraction with hexane biodiesel production [3]. for 4.5 h in a Soxhlet apparatus followed by HPLC analysis Alkali-catalyzed transesterification of fats and oils in the (below) of the resulting oil indicated a 8.8 wt% triacyl- presence of a simple monohydroxy alcohol, usually glycerol (TAG) content. methanol, is the predominant technology used for FAME MBM, obtained from a commercial rendering facility, synthesis. For vegetable oils this requires the prior recovery was provided by Dr. Rafael Garcia of our facility. It con- of the lipid by pressing or solvent extraction, and the partial sisted of particles with a size range such that 74% of the purification of this oil. We have previously described an mass passed through a 20-mesh screen, and only 2% passed alternate method of FAME synthesis from soybean oil, through a 50-mesh screen. The moisture content, deter- termed in situ transesterification, which does not require mined by oven drying as described above, was 2.0 wt%. the extraction and purification of the oil prior to FAME Soxhlet extraction with hexane followed by HPLC of the synthesis. Rather, thinly flaked soybeans are themselves the resulting oil indicated 9.1 wt% triacylglycerol content. feedstock for this process, and alkali-catalyzed transeste- DDGS and MBM were stored at 4 °C. rification takes place directly within the flakes during As required, feedstocks were incubated in a convection incubation in alkaline alcohol [4]. This process operates at oven (77 °C) until the desired moisture levels were high efficiency, and under optimum reaction conditions attained. achieves maximum theoretical conversion of the acylgly- Soygold brand biodiesel, produced from refined soybean cerols of the feedstock into FAME. Furthermore, the oil, and used as a chromatography standard was the product resulting ester preparation meets the ASTM specifications of Ag Environmental Products, Lenexa, KS, USA. Soybean for biodiesel [5]. oil TAG and FFA for use as chromatography standards The desirability of ensuring future supplies of biodiesel were obtained from Sigma-Aldrich. Palmitic, stearic, oleic, feedstocks, while at the same time minimizing economic linoleic, and linolenic acids, mixed in amounts proportional pressures on high quality lipids, has led to the develop- to their mass abundance in soybean oil [6], served as the ment of methods to use low quality lipids, such as waste FFA standard. A mixture of FAME, whose composition greases and soapstock for biodiesel production. Other low- reflected the fatty acid content of soy oil (RM-1), was the value lipid sources exist, but have received little or no product of Matreya, Inc. (Pleasant Gap, PA, USA). Organic TM attention in this regard. One of these is Distillers Dried solvents were B&J Brand High Purity Grade (Burdick & Grains with Solubles (DDGS), a co-product of the fer- Jackson, Inc., Muskegon, MI, USA). Other chemicals were mentation of corn to produce ethanol via the dry grind Analytical Reagent grade quality or better. process. Another is Meat and Bone Meal (MBM), a product of the animal rendering industry that is composed of the inedible portions of animals slaughtered in meat Conduct and Optimization of in situ Transesterification production. Both are produced in substantial quantities, have low economic value, and contain 5–10% lipid, which The lipid-bearing material (5.00 g for MBM, and an could be converted to FAME. These materials are not amount equal to 5.00 g of dry matter in the case of DDGS, suitable for the recovery of their lipid by hexane extraction for which multiple moisture levels of substrate were or yield preparations of poor quality. In the present work examined) was mixed with methanol in which sodium we report the results of an investigation of the ability of hydroxide had been previously dissolved (‘‘alkaline alco- in situ transesterification to convert the lipids in DDGS hol’’) in screw-capped bottles of a capacity at least five and MBM to FAME. times the reaction volume. These were mixed by orbital shaking at a speed sufficient to keep the solids well sus- pended. Reactions were conducted in heated chambers at Experimental Procedures the desired reaction temperatures. Central Composite Response Surface design methods Chemicals [7] were employed to investigate coordinately the effects and interactions of the amount of alkaline methanol, its DDGS was the product of an industrial corn-to-ethanol NaOH concentration, and reaction time on the yields of fermentation plant, and was provided by Dr. Vijay Singh, FAME, FFA and unreacted TAGs in the liquid phase. Department of Agricultural and Biological Engineering, Preliminary studies (data not shown) were conducted to University of Illinois, Urbana, IL, USA. It consisted of focus the statistically designed work in the region of var- solid particles with a size range such that 88 wt% passed iable space giving greatest FAME production. 123 J Am Oil Chem Soc (2007) 84:963–970 965 For the final optimization of the reaction conditions for Identification of the fatty acids in the FAME product 5-g reactions of DDGS, the amounts of alkaline methanol was achieved by GC, with flame ionization detection. The tested were 12, 14, 18, 22, and 24 mL; NaOH concentra- column was a Hewlett–Packard Innowax fused-silica cap- tions were 0.20, 0.25, 0.35, 0.45, and 0.50 N; and reaction illary, 30 · 0.53 mm (internal diameter) run as previously times were 0.5, 1.5, 2.5, 3.5, and 4.5 h. This series of described [9]. FAME assignments were made by compar- variables was tested at DDGS moisture levels of 2.62, 6.86, ison with known FAME. and 8.7 wt%. Each series involved 20 reactions at various Nitrogen contents (wt%) were determined using a combinations of these levels.