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As the ethanol industry in the U.S. continues to progress, the industry continues to use advanced technologies to maximize efficiency and profit. 

In the ethanol production process corn oil can be extracted from the co-product stream by centrifugation other extraction.  The corn oil extracted is similar to that of food grade oil and can be used as for animal feed but corn oil is also more than ever becoming a viable option as a feedstock for biodiesel.  Currently extracted crude corn oil sells for ~$0.59/lb, but if the corn oil is left un-extracted EPA estimates the value is only ~$0.05/lbs.  Additionally extraction of the corn oil also reduces the mass of DDG that has to be dried, reducing the energy input for the production of the DDG, and reducing the fat content which improves the flow characteristics’ of the DDG.

In 2010 it was estimated that approximately 20% of ethanol plants were extracting corn oil. Current estimates indicate approximately 40% of plants are extracting oil and that number will grow to 75-80% by the end of 2012. Traditionally Corn oil has not been a primary feedstock for biodiesel due to its high Free Fatty Acid (FFA) content which requires pretreatment, but because of increased RFS2 requirements for advanced biofuels the demand for corn oils is rising. Methods for removal of the corn oil vary resulting in variability of the quality from producer to producer. For example some producers have marketed their products as having <5% FFA.

Extraction of the corn oil brings up additional questions of quality control of the final DDG product. It becomes even more important to have regular, standardized testing of the co-product streams and final DDG to monitor extraction efficiency of the corn oil while maintaining a consistent nutrient profile of the DDG product.  An additional panel of analyses must also then be applied to the corn oil co-product to ensure its quality. 

Key parameters for quality analysis of corn oil for feed stock:

Oil AnalysisTypical Corn Oil SpecificationIdeal Specification
Moisture 0.15% 0.05% or less Excess moisture in feedstock can react with catalyst during transesterfication leading to soap and emulsion formation. There fore feedstock with high moisture must have heat/vacuum applied to remove excess. Corn oil average moisture content is ~0.15%
Insolubles Impurites 0.25% Lower value better Measures solid impurities such as sand, dirt, and left over seed fragments
Unsaponifiable Matter 1.7% Lower value better Measures organic compounds present that do not react in transesterfication and may remain in biodiesel product
Free Fatty Acids 12% 0.5% or less Feed stock with high FFA like moisture can react to form emulsions.  Corn oil has high FFA and requires pre-treatment.
Sulfur 10.5ppm <15ppm Final biodiesel sulfur content must be below 15 ppm
Phosphorus (Ca, Mg) <0.1ppm (also <0.1ppm) <10ppm, <5ppm Final biodiesel sulfur content must be below 10 ppm.  Combined Calcium and Magnesium must be below 5ppm
Oxidation Stability Index (OSI) 8.6 hours Higher number, more resistant to oxidation Measurement of the oxidation stability of a feedstock and predictor of if oil will meet biodiesel OS requirements.

Angela Carlson
Analytical Lab Manager
t: (605) 692-7611, ext. 5

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