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At what titration point do you not need AE? (KOH) + small questions

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December 08, 2013, 03:33 AM
At what titration point do you not need AE? (KOH) + small questions
i saw the other person's post who's titration was 5 and it was still recommended he use AE. At what point should you just skip the acid stage and go with a regular single base method? double base recipes seem redundant.

I had a batch that titrated at 7.75 and it worked great. then i got a batch that titrated at .75 and it didn't work too well. attached is what it came out looking like after the acid stage.

with the same batch of .75, i just ran a single base and it came out great. only bad thing was what i was using to spray mist. my first shot was like a super soaker and it made some necessary emulsion :T.

Oh, i was also wondering what was the best way to dry the wvo in the beginning. Resources at school werent too great so i just boiled it out for 30m. perhaps that wasn't the best method as suspended water can't really be boiled out.

the first picture was of the low titrating WVO after the acid stage.
the second is the obligatory finished biodiesel Smile


"imagination is more important than knowledge" - Albert Einstein
December 08, 2013, 03:34 AM
ops, heres the second pic

"imagination is more important than knowledge" - Albert Einstein
December 08, 2013, 07:44 AM
well if you had a dedicated AE tank (which is the proper technique), then i'd do it everytime.

results (yield, washing) diminish greatly in the 10-15 KOH range. alot of extra soap, and if the oil is the slightest bit wet, you might not get separation.

i think i would caustic strip with glycerin below 10 KOH.
December 08, 2013, 08:06 AM
I suspect you are going to get a lot of different answers to your question because there are a lot of variables at work here, for instance what is acceptable quality? what is acceptable yield etc.

But here is my 10cents worth.
up to 1.5mlKOH single stage base.
Up to 7ml KOH 2 stage base/base
Above 7ml KOH either caustic stripping followed by 2 stage base/base.
or AE followed by single stage base.
or better still AE followed by 2 stage base/base.
December 09, 2013, 03:35 AM
acceptable quality would be to pass ASTM testing. yield i was hoping for the 95%+ range.

i also made a critical error during one of the washes on my single base reaction. i wasn't paying attention i drained a lot of the WVO lol.

I would think that it would be single base up to something like 3, and then AE at any point forward. i went to visit biodiesel hawaii ( and they use AE all the way i believe. pretty awesome operation they have at their big island processing center. all computer run and basically zero waste.

as mentioned many times in the giant Dkenny AE thread, water is the worst enemy for AE process. so drying the WVO prior to reacting is very important. it seems that there isn't a "best technique" because even after boiling the WVO at 110C for an hour, sandy brae reading was still around 8. for that reaction though, it passed 27/3.

On a scientific level though, it makes sense that you don't need AE if titration is low because you don't need to convert FFA to methyl esters if there isn't much present to begin with.

maybe for the students next semester i will recommend in my discussion section to test the different level of KOH so we could have a graph here. (we were the first semester to try it)

"imagination is more important than knowledge" - Albert Einstein
December 13, 2013, 08:09 AM
For my 5 penny's worth I'd say 5ml was the limit anything over that and you will be wasting caustic and oil to soap production. Your methanol in Glycrol out ratio will no longer be 1:1 I hate wasting my raw materials when chucking in a small quantity of acid (I know its not that simple i'm just speaking figuratively!)and a few more hours will solve the problem. Base Base is just a more efficient way of making soap.

VW Passat 2.0 TDI with a BKP engine 86,000 miles on B100 and not going strong. Bio-diesel broke oil pump drive shaft! ..No oil pressure, dead turbo.
May 10, 2014, 04:44 PM
I made a small 1 litre batch (single stage KOH catalyst), with used vegetable oil that titrated at about 8.5 KOH. I water washed, then dried it. It came out well. It seems to me that putting the sulfuric acid into the oil, then you can't get it all out in the later steps. One of the advantages to biodiesel is little or no sulfur in it. I have read that electrophillic addition may occur between sulfuric acid and double carbon=carbon bonds. So, to some extent besides acting as a catalyst, a side reaction occurs where the sulfuric acid bonds to the carbon chain of the fatty acids with double bonds in them, adding sulfur to the biodiesel fuel. Some evidence that shows this is true, was that the same oil processed with base catalysed reaction produces biodiesel that is lighter in colour than oil processed by AE. The HSO4 being bonded to a carbon being brown or dark brown in colour. Maybe Biotom knows?

This message has been edited. Last edited by: WesleyB,
May 10, 2014, 08:15 PM
Wish I could answer that question. My take is the darker color of the biodiesel is the result of the acid burning the oil. Hootep a guy who posts here from time to time, and a chemist, said that the darker color is easily removed when the biodiesel passes through an ion exchange tower. (dry wash) I think.

" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
May 11, 2014, 07:04 AM
You could be right about this Wesley, A couple of years ago I got a tour of Green Fuels biodiesel plant in New Ross. They mentioned that they did a preliminary stage using phosphoric acid not sulfuric acid because it was easier to pass fuel standards. They didnt specifically mention sulphur content but it would make sense.
July 13, 2014, 05:27 PM
generally anything over 7 titration if you're using KOH is in the AE range..
not be because KOH cannot be used at this it works fine..but the yield is way down.

if I have time, I run AE for 5KOH and up..helps the yield.


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July 14, 2014, 10:44 AM
Your titration number for which you decide to do an AE is going to depend greatly on your own circumstances..

I would say that no matter what, anything over 10 or 11 KOH must be esterified.. However, I think most would agree that a much lower value will greatly reduce the headaches involved with trying to process oil that is so degraded.

I have a variety of smaller customers who run my MM63 systems and make a batch a week.. I recommend to the majority of them to start considering AE processing at around a 7 - 8 KOH.. Those who have a problem finding enough oil will generally start around 4 KOH.. Those who are lucky enough to have more than they need will usually wait until they are above 7...

For my larger customer running our MM500 systems, I usually tell them to start AE at a few points less as it becomes an economical issue as well as a process issue.

It really depends on your own circumstances.. Processing high titrating oil causes a range of headaches that you'll need to deal with.. And while the proverbial grass may look greener on the other side of the fence, you'll find that running AE processing has its own set of problems you must also deal with.

Hope that helps,

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July 25, 2014, 06:07 PM
we general
over 7KOH is a must for AE
if time allows 5 KOH is fine for has a higher yield over all..but base only on 5KOH is fine..
yields are lower. my guess is 80ish vs 95ish range..

time vs yield and processing complexity..


'84 bluebird school bus, DD8.2L turbo( 4/2011, the bus tranny has died..Frown 8.23.11 bus driven to scrap yard Frown )
2006 Jeep Liberty CRD Smile - the wife's
99 dodge 2500 5.9l 24v..-mine Smile
everything run B100 when its warm enough Smile