Quality Standards for Degumming

RECOMMENDED QUALITY OF OILS FOR BIODIESEL PRODUCTION DEGUMMING

• Oil must go through degumming process
• Phosphorus (Gums) must be <20 PPM
• Low levels of heavy metals: Iron, Copper, Calcium and Magnesium

AVERAGE COMPOSITION OF CRUDE AND REFINED SOYBEAN OIL*

*The values for (ppm) total are average values for crude oils with the corresponding phosphorus numbers. Actual (ppm) may vary with crude oil quality and process conditions.

Recommended Quality of Oils for Biodiesel Production and Degumming

Learn about the recommended quality standards for degumming and biodiesel production, including key factors like fatty acid composition, free fatty acids, moisture levels, and impurities.

1. Fatty Acid Composition

The fatty acid profile of the oil directly affects the biodiesel’s quality. The ideal oils for biodiesel production should have a balanced ratio of saturated and unsaturated fatty acids.

• Unsaturated Fatty Acids: Oils with high levels of unsaturated fatty acids (mono- and polyunsaturated) such as oleic acid (C18:1) and linoleic acid (C18:2) are preferred. These acids are more readily trans esterified into biodiesel and tend to produce biodiesel with good cold flow properties and oxidation stability.
• Saturated Fatty Acids: While unsaturated oils are generally preferred, a small percentage of saturated fatty acids, like palmitic acid (C16:0) and stearic acid (C18:0), can be tolerated. However, high levels of saturated fatty acids can result in biodiesel that has higher gel points and poorer low-temperature performance.

2. Free Fatty Acids (FFAs) Content

Free fatty acids are naturally present in crude oils, especially in lower-quality or waste oils. High FFA content can complicate the transesterification process, leading to lower biodiesel yields and more soap formation, which requires additional processing steps.

• Recommended FFA Levels: It is generally recommended that oils used in biodiesel production should have an FFA content of less than 5%. If the oil contains more than 5% FFAs, the oil must be pre-treated (typically through acid catalyzed esterification) to reduce the FFA content before proceeding with transesterification.

3. Moisture Content

Excessive moisture in the oil can inhibit the catalyst’s effectiveness in the transesterification reaction. Water can also lead to soap formation, reducing the yield of biodiesel and making the separation process more challenging. Optimal moisture content yields s more Efficient Biodiesel Production.

• Recommended Moisture Levels: The oil should have moisture levels of less than 0.5%. This is typically achieved through drying or filtration processes before the oil enters the biodiesel production system.

4. Impurities (Solids, Dirt, and Free Glycerin)

Impurities such as dirt, solids, or free glycerin can negatively affect the efficiency of the biodiesel production process by causing blockages in filters, leading to slower reactions, and reducing the quality of the biodiesel produced. These are key factors in Biodiesel oil selection

• Recommended Impurity Levels: It is essential to ensure that oils used for biodiesel production are clean and free of impurities. Proper filtration or sedimentation should be performed to remove any solids or contaminants.

5. Viscosity

The viscosity of the oil influences the ease of the transesterification process and the final biodiesel quality. Oils with high viscosity tend to form thicker biodiesel, which can cause engine problems, particularly at low temperatures.

• Recommended Viscosity Levels: The ideal viscosity for biodiesel feedstocks is between 30-50 centistokes (cSt) at 40°C. Oils with higher viscosity, such as used cooking oils or animal fats, may need to be preheated or blended with lower-viscosity oils to ensure efficient processing.

6. Acidity and pH

The acidity of the oil can also influence the transesterification reaction. Oils with high acidity levels can lead to unwanted side reactions, such as the formation of soaps, which reduce the efficiency of biodiesel production.

• Recommended pH Levels: Ideally, oils should have a neutral to slightly acidic pH (around 6-7) for optimal biodiesel production. High acidity or basicity levels may require neutralization or other pre-treatment processes to optimize yield.

7. Optimizing Biodiesel Feedstock Quality

The source of the oil plays a significant role in the overall quality of biodiesel. Different feedstocks may require different processing techniques due to variations in their fatty acid composition, FFA content, and other factors.

• Common Feedstocks: Common oils used for biodiesel production include vegetable oils (e.g., soybean, canola, palm), animal fats, and waste oils (e.g., used cooking oils). Waste oils and fats often have higher FFA content and may require additional treatment steps compared to fresh vegetable oils.

8. Blending and Pre-Treatment of Oils

In some cases, oils may be blended to optimize the fatty acid profile for biodiesel production. For instance, combining waste oils (which may have high FFA content) with virgin oils can reduce the overall FFA content and improve biodiesel yields.

• Blending Recommendations: Pre-treatment methods such as degumming, deacidification, or esterification may be necessary for oils with higher FFA content, such as used cooking oils or animal fats. These oils may require additional steps, such as acid or enzymatic treatment, before they can be effectively used for biodiesel production.

9. Oxidation Stability

Oils with poor oxidation stability can lead to the formation of harmful by-products, affecting the performance of the biodiesel. Oxidation stability is an important factor for biodiesel used in storage and in cold climates, as biodiesel can degrade and form solids over time.

• Recommended Oxidation Stability: Oils with higher levels of unsaturated fatty acids (such as canola and soybean oils) tend to have better oxidation stability. Some feedstocks may need antioxidants to improve their stability before being used in biodiesel production.

Conclusion

For successful and efficient biodiesel production, feedstocks should meet the following general criteria:

• Low Free Fatty Acid (FFA) content (below 5%)
• Minimal moisture content (below 0.5%)
• Clean, free from impurities
• Viscosity and acidity within suitable limits
• Optimal fatty acid composition

By selecting high-quality oils that meet these standards, biodiesel producers can ensure the efficient conversion of oil to biodiesel with higher yields, better fuel properties, and compliance with industry specifications.

Also check out, “Quality Standards For Degumming“