i was drying my last batch of biodiesel and got a thick sludge like substance on top of my fuel. what is this and what caused this to occur.

I'm new to making biodiesel . I'm using mine to heat my house and after going thru the learning curve it seems to be working. While doing the drying process you got a scum on top of the biodiesel. What is the process that you use to react, wash and dry? Maybe someone with more experience can find the cause. I 'm just starting to set up my dry process ,which seems a little vague to me. I have a cone bottomed wash drum ,with a heating element in it. I guess I'm going to heat up the biodiesel in the wash drum to evaporate the water out. Hopefully the heating element will keep the bio stirred up . This will be after I drained off the rinse water, of course. MY bio after washing looks worse then before ,but I think this is common because small particles of water stick to the bio, and drying is supposed to cure this. I HOPE!

Could it be soap.

dwightq's scum on top of the drying bio puzzles me. I forget to mention that the bio I'm using in my furnace is not washed , right now I,m working on my BIODIESEL LAUNDERMAT. Are there any frogs ,or turtles in the scum?

What is the color of that SCUM? Maybe the bio isn't washed completely. Is this bio made using NaHO or KHO ? Because I had some crappy first batches using NaHO . Hey dwightq what does your bio look like after the wash?

If it floats as a thin blurry layer is is almost certainly soap.

I have found that KOH, even though it is more expensive is much easier to work with. Any soaps made with KOH tends to drop in with the glycerine layer.

If its soap it will scrape off as a complete skin. If it breaks up like ice on a pond its likely to be wax, which can be confirmed by heating it, when it will melt.

I've seen this before. When I was making BD in buckets I would get a light-brown scum on the top of the reacting BD. It is soap and I found that it was due to an incomplete reaction; either to little Methanol or too little catalyst

I've encountered this too. It is soap, If you skim it off and put it in water ,it will dissolve and leave the water milky like wash water. Wax as its called is actually chicken fat if the oil used was from cooking chicken wings etc.It will gel at a much higher temp. than the soy oil based bio.
Today I've made a 1 liter sample from bacon grease (leftover from this mornings breakfast), It made the cleanest, lightest looking bio that I have ever made. Only problem is it will gel at room temp. like bacon grease would. I will mix my bio to a B50 blend to keep it some what liquid at low temps. ( sorry i got carried away, must be the hang over) Happy New Year from The Western New York Biodiesel Co-op

Thanks for the input, soap sounds like what it is. The dark color made me think of glycerin. since glycerin is used to make soap. could my prewash have anything to do with the leftover soap that is going into my drying barrel? My fuel after it is done drying looks terrific completely see through and stays clear.

Thanks for the input, soap sounds like what it is. The dark color made me think of glycerin. since glycerin is used to make soap. could my prewash have anything to do with the leftover soap that is going into my drying barrel? My fuel after it is done drying looks terrific completely see through and stays clear.

What color is it? I've seen this before... if it is a light-brown scum on the top of the reacting Biodiesel, it could be some soap in the making due to an incomplete reaction perhaps? ... if not try a cleaner feedstock in your testing. Feel free to contact me with any question regarding clean used cooking at www.ecogreensites.com

If it has enough glycerin in it to be brown it will sink. White soap can float, or stay suspended. Some soaps are non-soluable in water such as iron soap. Is there rust in your reactor? Just food for thought.