High acidity of Waste Cooking Oil

[Leonardo F Biofuels Forum Newbie Find all posts View Profile Close Leonardo F]

Hi all!
I know that one problem using Waste Cooking Oil as biofuel is the high acidity value. The only way that I know for dacidify the oil is to add NaOH or KOH, that form soap (that you can easily remove by sedimentation and filtration).
I'd like to know if someone knows other ways for deacidify the oil.

Thanks in advance,
Leonardo Faggioli

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: High acidity of Waste Cooking Oil

Any alkaline substance can be used to neutralise the Free Fatty Acids i nthe oil. some work fast, some work slow. All will create a soapy byproduct which will need to be removed.

[Tim Mitchell Biofuels Forum Newbie Find all posts View Profile Close Tim Mitchell]

Re: High acidity of Waste Cooking Oil

I am not an expert on this, but from my research it seems that most of the acidity in the oil is from water soluble salts and sugars (and other food remnants) which has been deposited in the oil. When you mist wash the oil it will remove these acidic water soluble particles and as a result lower the acidity of the oil.

It is important to properly dry the oil after mist washing as a little bit of water goes a long long way to destroying your injection system.

[Guest Close David]

Re: High acidity of Waste Cooking Oil

I have been experimenting with mixing WVO with glycerin by product to lower the titration number. I have been mixing the wvo and glycerin at a ratio of 4 parts WVO to one part glycerin and so far the results have been promising.
The last tests I did lowered the titration from 9 to 6 in 24 hours with just a couple of shake up mixes. The oil did come down a little more over the next few days and mixing with a pump and heating may also help things along.

Perhaps a higher ratio of glycerin may work better but I was thinking that the 4:1 ratio was sustainable in I would always have that much glycerin left over from bio making to use on the next batch of oil.

Perhaps those just using SVO could get some glycerin from someone doing bio to lower the titration of their oil but is it at all nessacary to worry about the FFA content of the oil in the first place if you are using it in an SVO system?

[dagwill Senior Member Find all posts View Profile Close dagwill]

Re: High acidity of Waste Cooking Oil

i must admit the acid thing is a concern,but so far ive done about 88K over the last 5 yrs on filtered svo in my 1984 landcruiser.So far so good.the engine has done aprox 490K all up.IP never touched

[joe Moderator Find all posts View Profile Close joe]

Re: High acidity of Waste Cooking Oil

I have been experimenting with mixing WVO with glycerin by product to lower the titration number.

I take it you dont do a 5% prewash?

[Chris Senior Member Find all posts View Profile Close Chris]

Re: High acidity of Waste Cooking Oil

Hi All
The glycerine addition to wvo so as to lower ffa's makes good sense, however it does involve an extra step, no big issue really
Why does it make sense?
If one thinks about it, the conclusion he will have to come to is this;
What is in the glycerine from the last batch of biodiesel?
Ah! Koh, Methanol, as well as a bit of suspended biodiesel and a bit of water or a lot of water
Why then this mixture of the above, would not lower the ffa content of the oil
Of course it will, the Koh will neutralise some of the ffas, the methanol will react with some of the oil, turning a bit of it into biodiesel, the water would most likely hinder the whole process, nevertheless the step will make a bit of soap further reducing the ffa's,
All of the glycerine the soap any water and solids will settle out
When you drain the "wash" glycerine out you will have a better oil than you started off with
No doubt some of the fine solids in the waste oil will also be washed out of suspension all in all a good thing, but always with mixed results
In so far as ratios are concerned I cannot see why "the more the better" approach would not provide a "better" result for any one wishing to take this approach
It is good to know how, how much better is it when we also know Why
When we know why and something makes sense It sits better in our head

[Fitian Was here Find all posts View Profile Close Fitian]

Re: High acidity of Waste Cooking Oil

Any alkaline substance can be used to neutralise the Free Fatty Acids i nthe oil. some work fast, some work slow. All will create a soapy byproduct which will need to be removed.

Hi Tony,

What substance are you using to treat your oil please?

Thanks

Fitian

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: High acidity of Waste Cooking Oil

Hi Tony,

What substance are you using to treat your oil please?

Thanks

Fitian

I suspect these guys are posting on the incorrect board as acidity is more of concern to biodieselers who must calculate acidity in order to react the wvo with the correct amount of sodium methoxide to produce biodiesel. I have not come across of any problems experienced by WVO users.

Leonardo, you said you had a problem with the high acidity of your wvo. Can you tell us what problem this has caused if any, or are you worried about a potential problem, such as corrosion of fuel line components and engine etc.?

However, I have posted elsewhere on these forums of my trials with enzymes. (See http://www.biofuelsforum.com/svo_use...g_enzymes.html ) I'm suspecting that my inconsistent results with these trials could be due to acidity which the enzymes are sensitive to. One batch works great, the next doesn't, so this is is the area of my investigation at present.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: High acidity of Waste Cooking Oil

Fitan,
I do not treat my Used Cooking Oil as I am not making biodiesel.
Tony

[Fitian Was here Find all posts View Profile Close Fitian]

Re: High acidity of Waste Cooking Oil

Fitan,
I do not treat my Used Cooking Oil as I am not making biodiesel.
Tony

Okay Tony I thought it is needed to treat the WVO before using it in our case.

Thanks.

Fitian

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: High acidity of Waste Cooking Oil

Fitian,
The only thing I do to my oil is to filter it to 5 micron, straight into the drums I use as veggie fuel tanks. In one of my 300Ds, I pour from these drums into the custom built 70 litre veggie fuel tank.

My oil is stored indoors both of my suppliers, so I do not need to dry the oil.

Note, If you have a source of biodiesel processing byproduct, the addition of 10% of the byproduct, in relativeto the volume of oil, will effectively remove any water, convert some of the FFA into soap and allow most of the solid contaminants to settle out.

The byproduct and oil are stirred together, no need for vigorous agitation, and allowed to settle for 12 hours. The clear oil is decanted off the bottom layer, ready for filtering or processing into biodiesel.

For biodiesel production, this will lower the %FFA in the oil.
If performing an acid/base 2 stage reaction, the loss of some of the FFAs will result in a lower vield of biodiesel from the oil collected.