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BioDiesel Class 101

Class # 6 - Washing BioDiesel

    Some people claim that washing BioDiesel is not necessary, however the ASTM D6751 standard calls for BioDiesel to be washed. If it is not washed, it may contain contaminates such as soaps, methanol, glycerol & perhaps sterates. Unwashed BioDiesel is not considered ASTM grade BioDiesel. By washing these contaminates get removed. Please note that certain Bosh brand Injector Pumps are known to be susceptible to internal damage when exposed to even minor amounts of alcohol. This is due to the type of adhesive Bash used internally in the injection pump to hold certain critical parts in place. Bosh has stated they will deny warranty coverage if alcohol is determined to be the cause of the damage. We strongly recommend washing your BioDiesel as we do, besides it only takes a little longer so why take unnecessary chances. Official position statement from Cummins & Bosch regarding alcohol in diesel fuel.

    The reason that some people shy away from washing is because they either want to shortcut the process because they are lazy or are in a hurry. Some people claim that residual water will damage your Fuel System components which is true but what they don't say or don't know is just how easy it is to Dry BioDiesel & test for water content. What they fail to mention or are ignorant about in regards to not washing BioDiesel is the damage caused by residual alcohol left in the fuel & the tendency for particulates to later fall out of suspension resulting in clogged up fuel filters or injectors. While soaps can be burnt, they do not burn well & result in excessive ash which tends to remain in the combustion chamber condensing on the cooler surfaces such as the injection nozzles later building up & obstructing them.

    ASTM is the "American Society for Testing and Materials", ASTM is a not-for-profit, non-governmental organization committed to the development of voluntary standards for materials, products, systems and services. They have no ax to grind and are a non-biased third party of made up of mechanical engineers. If they say BioDiesel should be washed (Which they Do), then that is good enough for us. Choose to wash or not, that is your choice, we highly recommend washing, drying & then testing BioDiesel for water content before filtering & use.

    If using our "All in One" low fume BioDiesel processor design as detailed in our PGB book you can wash the fuel in the same processor that you made it in.  If you desire to increase through put you can use a dedicated "Standpipe Wash Tank" such as we have detailed in our PGB book. The "All in One" processor design we offer gives a person with very little space the benefit of having a way to Process, Wash & Dry his or her BioDiesel all in the same processor which results in a nice compact footprint. While a dedicated BioDiesel Wash Tank such as the "Standpipe Wash Tank" as detailed in our PGB book is nice because it gives the benefit of more rapid BioDiesel through put since you can be washing a batch of BioDiesel in the wash tank while you are making another batch in your processor, however does take up extra floor space.

    Washing is done using regular tap water & is really very simple. First insure you have allowed all if not most of any remaining glycerol to settle out of your BioDiesel, this makes washing go faster. Usually letting it settle overnight will settle out enough of it to allow washing. The reason for this is that when water is added to  BioDiesel containing glycerol, it can cause problems with emulsions if the washing is too aggressive.

The Washing Process

  1.     Use a short suction dip tube & pump the 40 gallons of BioDiesel from your settling tank into your CLEAN wash tank which preferably should have a stand pipe. Read the PGB book for an explanation of stand pipes & short dip tubes and how to use them.
  2.     Measure the distance from the top lip of the wash tank down to the surface of the BioDiesel & make note of this measurement. BioDiesel will later float on the water & this measurement will let you know when you are getting close to the BioDiesel/Water layer interface as you empty out the wash water from the bottom of the tank.
  3.     The first few washings are touchy, never begin with a bubble wash as it is way too aggressive. Start by washing the BioDiesel with a very fine Fog of water. To do this you can use an array of water Fog nozzles arranged around the top of the tank. An array of them works well because the flow rate of an individual fog nozzle is usually very low but you can get a fairly decent flow rate if you use an array of nozzles around the top of the tank as we suggest in our book. Be sure to put a lid on the tank, the lid does not need to seal the tank. it just keeps the wind from blowing the water fog out of the tank. Note: Use the nozzles we suggest because other nozzles form a much larger droplet size, that can easily start an emulsion to form if the BioDiesel contains very much glycerol or soap.
  4.     Fog wash the BioDiesel until you get around 7 gallons of water in the tank, this may take a number of hours which is dependent on the number of Fog heads & rate of flow. Note that the rings on a 55 gallon steel drum each represent approximately 18 gallons so 7 gallons would be a little less than 1/2 a ring. You will likely notice that after Fog washing the BioDiesel it now looks kind of opaque like Orange Juice, do not worry, this is normal & simply indicates that the BioDiesel contains water. The BioDiesel will start to clear up a bit after more washing has removed the soaps, remaining glycerol & alcohol which tend to hold onto the water. Drying it later will clear it up until it is crystal clear. Note: The natural color of washed dry BioDiesel is not clear but it is very transparent the color is a natural function of the base oil it is made from & will vary. 
  5.     Carefully drain out the wash water taking note of the distance we measured earlier in step #2. If you begin to see either BioDiesel or a cream come out, you want to change the container you are draining wash water into & slow down the rate of flow. If creamy, collect most all of the cream into this container & set aside for now. This is an emulsion & it will usually break apart on it's own if left in the sun. Once this emulsion breaks you can siphon out the wash water from the container & put the BioDiesel back into the wash tank. Sometimes this emulsion can take days or weeks to break apart, usually it will do so in under a week. You can shorten the separation time by using the methods we suggest in our book. By the way, it is far easier to siphon out the water from underneath than siphoning out the BioDiesel on top, the reason for this is that you will get water or emulsion along with the BioDiesel if you try to siphoning from the top.
  6.     Repeat steps #4 - 5 as required until the wash water comes out looking translucent like a thinned milk & water mixture. Save a bit of this water in a clear glass jar for comparing with the next wash water.
  7.     At this point, do one last Fog Wash but do not drain it out this time, instead turn on your air pump & sink a Bubbler ring down to the bottom of the wash tank to bubble air up through the wash water & BioDiesel. Bubbling air carries minor amounts of wash water up through your BioDiesel & washes it. Monitor your bubble wash periodically to make sure you are not bubbling too aggressive, if you are you will see what looks like yellowish white bubbles that don't quite ever break the surface & instead magically sink back down! These are actually little emulsion pockets & they will sink back down to form an emulsion layer on top of the wash water. If you see these, turn down your Bubbler air flow or revert back to doing another mist wash. If all looks good, bubble for a period of a 3 to 4 hours then Drain the wash water. You will notice that the wash water comes out a bit milkier white looking than your last Fog Wash. Save a bit of this water in a clear glass jar for comparing with the next wash water.
  8.     Repeat step #7 this time plan to Bubble wash overnight but check on it after a few hours or so to insure that it isn't forming an emulsion. Next morning, drain the wash water. If it looks like very thin translucent milk water which is more transparent than your last Fog Wash water was, then you are done. If not, then repeat Step #7 until it does. Try the shake test to see if it is done, Put some BioDiesel in a clear 2 Liter pop bottle, add some clean water, put the cap on the bottle & shake it up. If the BioDiesel separates rather rapidly from the water then it is clean enough & your done. If the BioDiesel forms an emulsion with the water & takes a long time to separate then you still need to do some more washing before going on to Drying the BioDiesel.

    One last note, you can save the water from the last bubble wash & use it if you desire for your next bubble wash. Personally we believe this is more trouble than it is worth but some people do it.


And you thought we forgot.....

  1. What method of washing should you begin with?

  2. How long should you allow BioDiesel to settle out the glycerin before starting to wash?

  3. What is the shake test?

  4. Should BioDiesel pH be slightly acidic or base & why?

  5. What can cause a pH shift in your BioDiesel while washing?

  6. What purpose would you put a jar full of saved used wash water?

  7. What contaminates does unwashed BioDiesel contain?

  8. Will Bosch cover an Injector Pump under warranty that they determine was damaged by alcohol?

  9. How expensive is a replacement Injector Pump + Labor to install it for your vehicle? Hint... call your local vehicle dealer for a quote.

  10. What should your wash water look like before starting aggressive Bubble washing?

  11. What is happening if you notice yellowish white looking bubbles come up but never break the surface before sinking back down?

  12. How long does it take for an emulsion to break on it's own?

  13. If you are recovering BioDiesel from a broken emulsion by siphoning, which should you siphon out first the water or the BioDiesel & why?

  14. When draining out the wash water, how do you know when you are nearing the BioDiesel Wash water interface?

  15. What type of wash technique should you use first?

  16. Always start out with a bubble wash (True or False), why ?

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Last modified: 11/26/16