Biodiesel Emulsions 101 – Preventing And Curing Them

If you’ve been making Biodiesel for any given amount of time, chances are you’ve seen an emulsion and maybe even had to deal with one yourself. They’re a royal pain in the butt, aren’t fun to see, and generally just cause more pain & heartache than they’re worth. Because it’s such a common part of making Biodiesel, we’ve decided it was high time to talk about emulsions, what they are, how to prevent them, and then how to fix them if you do get one. So, here comes Emulsions 101.

What Is An Emulsion?
In short, an emulsion is a combination of water, Biodiesel, soap,  sometimes glycerin and unreacted oil. They can be very liquid, bordering on what skim milk looks like to flat out cottage cheese looking. No matter what they look like, they just aren’t fun to have around.

For a much more in-depth explanation of what an emulsion is, check out this great article: Jack Jones Article On Emulsions Essentially, the soap binds the water and the oil together and “emulsifies” them into a big, white, goopy mess.

Here’s what an emulsion looks like:
Biodiesel Pictures Online
It reminds me of a white milk-shake. All nice, white, & frothy….
Emulsions can look like light skim milk, a dark vanilla ice cream shake, or even thick & chunky like cottage cheese or cheese curds. But, no matter how you slice it, it’s something you really don’t want to see.

How To Prevent Emulsions
The greatest way to deal with emulsions is to not get one in the first place. Here’s 5 tips for keeping them far far away from your Biodiesel.

ALWAYS check your oil for water content and if it’s wet (say higher than 5000 ppm or 0.5%) then remove the water.
Here’s why:
Water + Oil + Catalyst = Soap (and lots of it!)
Soap + Oil + Water (a.k.a. water washing) = Emulsions

So, how do you remove that pesky water? Well, heat and time and, if possible, some mixing. The more of these used, the better.

Check Out This Article on how to dry Biodiesel as it gives some great tips.
The same concept in the article also works for drying waste oil before it’s processed. In our Feb. 2009 Newsletter, we talked about tips & tricks for detecting water and tips on how to eliminated it as well. If you didn’t have a chance to read through it, we highly recommend it.

Quick Water Removal Method
Here’s a really basic method that I use in my personal BioPro 190 processorthat works really well. You can modify this to your own equipment as well.
A- Turn on the manual heat for 18-24 hours with the lid off
B- Return to unit & drain off any water plus 1-2 extra gallons
of “interface” oil
C- Then turn on the heat & stirrer for 6 hours with the lid off
D- After 6 hours, test for water content. If below 0.15%, process.

Now, for those without a BioPro, here’s basically what we’re doing and if you follow these principles, you can acheive similar results.
A- Apply heat via a heating element to bring oil up to about 130-140 F
(NOTE: If you have poly tanks, learn your upper heat limits and don’t exceed them. It’s usually about 120 deg. F)
B- Have a fan running over the top of the opening (this creates a “low pressure air system” above the tank and the moisture naturally will move from the oil to the low pressure and get blown away by the fan)
C- Circulate the oil. You can use a pump, an impeller, air bubbles, whatever you want. The goal is to just circulate the oil.

In the Feb. 2009 issue, we highlighted a system that we thought was ingenious for water removal that utilized a Dry Pro Nozzle, a fan, some heat, and a recirculating pump.

If you have a lot of unreacted oil mixed in with the Biodiesel, when you attempt to wash it the oil will get in the way & also cause an emulsion. To test for full reactions, just use the simple 3/27 Methanol Conversion Test

Basically, you add 3 mL Biodiesel to 27 mL of Methanol at 68 to 72 Deg F. Shake it, let it sit for about 5-10 minutes and check for any oil drop out. We carry a Biodiesel Conversion Test Kit that makes doing the test extremely easy (and it’s cheap too!) We even have a video available that shows how to do the test.

If your Biodiesel doesn’t pass this test, just re-react it. Doing a re-reaction is pretty simple too and can yield you much higher quality Biodiesel anyway.
Here’s the method I use:
A- Times your methanol & catalyst originally used by 30% (0.30)
B- Add this new amount of catalyst & methanol together & dissolve
C- Heat your Biodiesel back up & add this mixture to it & reprocess
D- Run the pump, impeller, processor, etc. for 2 hours, then allow the glycerin to separate again
E- Remove glycerin & retest for full reaction
F- Repeat again if necessary

When Biodiesel is made, a lot of that soap ends up down in the glycerin layer. When you drain the glycerin from your processor, be sure that you’re getting all of it. If you don’t, water can mix with the glycerin and also kick off an emulsion as well.

To be safe, I ALWAYS drain my glycerin 3 times. Here’s how I do it.
A- Drain glycerin until you see Biodiesel then close the valve
B- Let the processor sit for AT LEAST 5-10 minutes
C- Come back & drain again (you’ll be AMAZED at how much glycerin will sometimes come out)
D- Let it sit again for another 5 minutes
E- Drain again, but this time drain AT LEAST a 1/2 gallon of Biodiesel out as well

By doing this, you ensure that you get all the glycerin out (unless you’re draining from an Appleseed/water heater style processor…but that’s a whole other issue that we’ll cover in another newsletter later).

Another trick to keep emulsions at bay is to add about a gallon of vinegar to your reacted Biodiesel before washing it. This mild acid works to keep soap from forming between the oil and water. In some cases it can even help break emulsions too.

Before washing your batch of Biodiesel, be sure to heat it back up to at least 80 to 90 deg. F. Cold Biodiesel and water don’t really do too well together and the chances of getting an emulsion go up quite a bit the cooler the Biodiesel is.

Also, if it’s at all possible, wash your Biodiesel with hot water. The hotter the better. It’s the same concept as washing a greasy pan after you’ve cooked a couple hamburgers. The grease will wash out of the pan much faster if you use hot water.

How To Fix An Emulsion

Breaking emulsions is pretty simple. You just have to understand what got you there in the first place and then back out of it.

If you remember from above, an emulsion is just a mixture of oil and water. They aren’t chemically bound together, they’re just really well mixed. To break this mixture, you can use the following methods

This method is BY FAR my favorite method because it works so well and so fast.

Here’s how to do it.
A- In a 5 gallon bucket, add about 1-2″ of rock salt (ie. water softner salt)
–NOTE: ANY salt will do, but Sodium Chloride seems to work the best
B- Fill the bucket the rest of the way up with hot water
C- Dissolve the rock salt into the water
D- If possible, heat the emulsified Biodiesel back up to about 90-100 deg. F
E- Slowly add the salt-water mix to the emulsified Biodiesel
F- Using a stick or a stirrer (DO NOT USE A CIRCULATION PUMP) gently mix the salt water into the Biodiesel for about 30-45 seconds. (If using a BioPro, hit the manual stir for about 15-20 seconds)
G- Allow the mixture to sit for at least 3 hours but overnight is best
H- Return and drain off water
I- If there’s still an emulsion, repeat this process.

Here’s a link to some pictures of how well it works:

And, here’s a link that explains why it works so well:

This method has been tried by others and found to be effective at times.

The Method:
A- Heat the Biodiesel back up to about 90-100 deg. F
B- For every 50 gallons of emulsified Biodiesel, add 1 Gallon of Vinegar
C- Gently mix in the Vinegar
D- Let the mixture set for several hours

I’ve seen limited success with this method, but others have indicated that it works.

This method was discovered by Jack Jones, the person that taught me to make Biodiesel years ago. It involves adding glycerin from a previous batch of Biodiesel to the emulsified mess.

The Method:
A- Heat up the emulsified Biodiesel to about 90-100 deg. F
B- Add half of the glycerin from your previous batch to the mix & stir
C- Let sit for at least 2-3 hours
D- If it hasn’t broken yet, add the rest of the glycerin and stir again
E- Let sit for another 2-3 hours

If this method doesn’t break the emulsion, consider using the Salt Method as it seems to be the most effective.

And there you have it!
1- What Emulsions Are
2- Why They Happen
3- How To Break Them

Here’s wishing you an emulsion free brewing session!

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13 comments on “Biodiesel Emulsions 101 – Preventing And Curing Them

    • About 1 gallon of vinegar for every 50 gallons of Biodiesel being washed.
      When the temperature in the room falls below 65 deg. ambient, or if you titrated REALLY high, then vinegar is a good candidate for use.
      To add it, you can either mix it in with the wash water (if you have a fresh water container you draw from) or you can also just dump it right into the Biodiesel and start washing.
      Emulsions are most likely to occur on the first wash so that’s why you can dump it right in on the first wash.
      If you want, you can even add some to the fuel for the second wash as well. Just be sure to wash with pure water on the final wash.

      • Vinegar works well but don’t forget that acidifying the soap (emulsion) releases ffa into the bio diesel. Adding 7ml of vinegar per ltr of wash water will keep the emulsions at bay!

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  5. This has been the year of the emulsion. Every batch from June until my last batch emulsified. I tried draining off all the glycerin, adding vinegar first, heating up the bio first, etc. to no avail. I wound up having to use the salt water fix for every batch. I’m using oil from the same places, chemicals from the same places. My oil titrates @ 2.5 with NaOH. Any ideas? Hoping for better luck next year.

    • I would check a couple things:
      1) Make sure the oil is dry before starting. We recommend getting it under 2000 PPM (0.02%). You can learn how to perform a water test here:

      2) Check that your titration level isn’t too high (I consider anything over 9 fairly high). You can do an acid esterification if it is that high
      Or, just go easier on washing

      3) Perform a 5% pre-wash prior to washing the Biodiesel. This will drop a TON of soap out before you start washing the Biodiesel and can really help prevent the emulsions from occuring

      4) Ensure the Biodiesel is warm when washing (I recommend 90-100 deg F) and that the wash water is luke-warm (about 70-85 deg F). If the water is too hot and especially if you’re using KOH to react, it can exacerbate emulsions.

      5) Check the purity of your catalyst. Are there clumps in it? Has it been exposed to air? Is it over a year old? If so, try replacing it & seeing if the emulsions are reduced

      6) Change your titration solution. As titration solution ages, it weakens resulting in artificially higher titrations. This translates to adding more catalyst than you really need, which ends up making more soap, which can cause more emulsions. We recommend changing titration solution every 90 days to be safe

      7) Check the purity of your methanol. If it’s become contaminated with water that can add to the soap production during the reaction, which can lead to more emulsions too. We sell a kit for measuring the purity of methanol. It should be at least 98.7% pure or purer.

      8) Check your misting nozzles. If they’re starting to gum up, you may not be getting an even spray pattern, which can also lead to emulsions. Also, check the water pressure. If the water is being sprayed too aggressively onto the Biodiesel, that can cause issues as well. Back down on the pressure & see if it helps.

      Hope those tips help.
      Utah Biodiesel Supply

  6. could be that the byproduct is not sufficiently settled from the bio diesel before washing. A 5% pre wash is always a good way to prepare the bio diesel for the wash cycles, also the amount of water you use in the wash cycle plays a big part in the emulsion story. As stated in the write up above an emulsion (think colloid) is a combination of soap water and bio diesel. The conditions must be right or you will not create an emulsion. I find that restricting the water amount to 7% of the volume of oil in the tank does wonders at eliminating this horror! look at the 5% pre-wash, the bio diesel at that stage is contaminated with lots of byproduct but emulsions do not happen at that step.
    As for water temperature/softness, hot water will pick up more soap than cold water, soft water will also pick up more soap than hard water so if you use hot soft water be very careful (gentle) during your first couple washes. (a good experiment , heat some rain water then wash a test batch by shaking in a jar, guaranteed emulsion) after that most of the soap will be gone and with it the chance of creating an emulsion.

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