Dear friend Abdelhalim Balouli

The formula commonly used to calculate biodiesel yield, as you mentioned, is:

Y = (mass of obtained biodiesel) / (mass of oil used)

However, it is important to note that this formula provides an estimate of the biodiesel yield and has some limitations. To address your specific questions:

1. The "mass of obtained biodiesel" typically refers to the mass of the upper phase obtained after settling in the separation funnel. This phase is expected to contain the biodiesel product along with other components such as unreacted oil, diglycerides (DGs), and monoglycerides (MGs).

2. It is true that the upper phase obtained after settling may contain unreacted oil, DGs, MGs, and other co-products that are inter-soluble with biodiesel. Weighing the upper phase alone may not accurately determine the true biodiesel yield since it does not differentiate between biodiesel and other co-products.

To obtain a more accurate measurement of biodiesel yield, additional steps may be necessary, such as:

- Transesterification reaction completion: Ensure that the reaction is allowed to proceed to completion by optimizing reaction conditions such as time, temperature, and catalyst concentration.

- Washing and drying: Perform washing steps to remove impurities and residual catalyst, followed by drying to remove any remaining water content.

- Purification: Employ techniques such as vacuum distillation or column chromatography to separate biodiesel from co-products and impurities.

By implementing these additional steps, the purity of the obtained biodiesel can be improved, providing a more accurate measurement of biodiesel yield.

Regarding references, here are a few articles that discuss biodiesel yield calculation and related considerations:

1. Freedman, B., Butterfield, R. O., & Pryde, E. H. (1984). Transesterification kinetics of soybean oil. Journal of the American Oil Chemists' Society, 61(10), 1638-1643.

2. Canakci, M., & Van Gerpen, J. (2001). Biodiesel production from oils and fats with high free fatty acids. Transactions of the ASAE, 44(6), 1429-1436.

3. Kusdiana, D., & Saka, S. (2004). Kinetics of transesterification in rapeseed oil to biodiesel fuel as treated in supercritical methanol. Fuel, 83(11-12), 1517-1522.

These references provide insights into biodiesel production, including discussions on reaction kinetics, optimization, and measurement of biodiesel yield. They may serve as valuable resources for your research on biodiesel production and yield calculation.

My own articles like Chapter Future Direction of Biodiesel in the Next Decade

Conference Paper A Review of Biodiesel Policy around the Globe

can also be a good read

Dear Kaushik Shandilya ,

I appreciate your fast answer and I agree with you, but in most articles where they work on optimization, they mention having yields for example equal to 40% which is impossible to find with the simple dividing the upper phase's mass by the oil's, you'll get more than 90% everytime.

So without further advanced analysis such as gas chromatography, biodiesel yield can't be determined.

Thank you again for your answer and the recommended articles

!

Dear friend Abdelhalim:

My contact information is provided in my profile. We can discuss the issue at your convenience.

the obtained biodiesel should be taken as the amount of refined biodiesel produced along the entire reaction/refining/separation sequence. This is yield, conversion is defined as esters converted.

Most papers are wrong because of this as this obviously yields higher conversion, and even higher than 100%. More correct formula would be:

Y=biodiesel/maximum theoretical biodiesel (assuming all the oil was reacted)

what you have specified is not yield, but efficiency

Andras Kovacs Let's say the yield's formula is correct, how can you find a 60% yield for example if you are weighing the upper phase which contains the unreacted oil, you'll always find the mass of the upper phase = the mass of initial oil.

Ferenc L. Martinovic You mean by the mass of biodiesel the sum of all esters analyzed by GC or other methods, right?

No, biodiesel means fatty acid methyl ester, ie, cannot contain not converted parts! so the yield is: amount of (standard) fatty acid methyl ester (others excluded, and nt the oil phase!) related to the amount of feedstock, whatever the composition of this.

Andras Kovacs So the common formula that everyone is using is wrong, because they measure the mass of the upper phase (which may contain unreacted oil) and they divide it by the initial mass of feedstock.

So unless we use analytical methods such as GC and HPLC, we can't really measure the real yield.

You have to wash all unreacted MG and DG and any other impurities and byproducts. Once you obtain the pure biodiesel (FAME) then you can follow that formula.

Venkatesh Mandari How to wash the unreacted oil and DG and MG, using water? the oils aren't soluble in water are they?

Dear friend Abdelhalim Balouli

It seems that you are asking about washing or polishing off excess glycerin or soap in freshly separated biodiesel to meet the ASTM specification. You can take the soap/glycerin out by washing it with water or mixing the biodiesel with magnesium silicate and using specialty soap-absorbing chemicals (https://biodieselmagazine.com/articles/8477/the-final-treatment). Whether one is washing or polishing, the step is extremely critical¹. However, it is important to note that purification using wet washing method requires 60-80% of total production cost hence this method is not suitable for large scale biodiesel production (https://pdfs.semanticscholar.org/9059/1c26075117ca0703a546283ac1d7efa958d4.pdf).

It is difficult for me answer more precisely as I dont know what DG and MG is.

Source:

The Final Treatment | BiodieselMagazine.com. https://biodieselmagazine.com/articles/8477/the-final-treatment.

Effect of Extraction Time on Unreacted Oil Removal in Biodiesel .... https://pdfs.semanticscholar.org/9059/1c26075117ca0703a546283ac1d7efa958d4.pdf.

4.7: Reaction Work-Ups - Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_%28Nichols%29/04%3A_Extraction/4.07%3A_Reaction_Work-Ups.

Dear Kaushik Shandilya ,

Let me be clarify from the beginning, we have a quantity of raw oil l that react with methanol in presence of a catalyst to obtain biodiesel (FAME) and glycerol as a byproduct.

When the reaction occurs intermediate products such as Diglycerides (DG) and Monoglycerides (MG) are obtained and we don't know if they're converted to esters or not, and they are all intersoluble (oil+DG+MG+FAME) and they are very less soluble in glycerol which is the lower phase.

So if 100 grams of oil is the initial mass, we will obtain approximately always 100grams in the upper phase (excluding the little amount of excess methanol which can be present in both phases), so my question, how can we eliminate or quantify the amount of unreacted oil?

Thank you!