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Free Fatty Acids or FFA's in WVO How do they get there?

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  • Free Fatty Acids or FFA's in WVO How do they get there?

    Hi all
    Thought that it may be useful to go into a bit of a discourse in regards to free fatty acids what they are as well as how they are involved or effect biodiesel production
    A bit of a layman’s explanation of the composition of vegetable oils or fats’ for a simpler understanding without the necessity of having a deep understanding of chemistry or chemical reactions
    So here we go
    Oils and fats as we know them for biodiesel production are called Triglycerides
    Triglycerides are natural compounds that have a back bone of Glycerol with three fatty acids attached to them
    Glycerol has a branched structure with three places where the fatty acids are attached to
    They get they name from the backbone that has three branches in which they are attached, Tri = three, Glycerides from the glycerol back bone
    There are a variety of those acids in different oils they are known as Carboxylic acids, also known as Lipids
    There is no need here to go to the whole chemical make up of different acids a particular oil is comprised of, only a few will be mentioned, such as oleic acid, palmitic acid, stearic acid, linoleic etc
    These fatty acids are all made up of even numbers of carbons from 8 to 18
    When all of these fatty acids are attached to the Glycerol back bone, we have an ideal situation which we can deal with very easily,
    Of course this means there will be no "free" acids in the oil
    However this is not the case, there is always some fatty acids that are not attached to the Glycerol backbone, even if the oil is new, they are called free fatty acids,
    This comes about from the processing of the seeds so as to produce oil This is done in an oil expeller The expeller will take most of the oil out in the process, what remains is called expeller meal
    Since there is a fair amount of oil in this meal, solvents are used so as to extract any oil remaining in the meal produced as a result
    The expelling as well as the solvent extraction will produce more free fatty acids
    Since most oils we use for biodiesel in this country are produced for human consumption they have to meet certain standards
    These oils go through a further process, refining deodorising and bleaching, they are then commonly called RDB oil’s in the industry
    RDB stands for Refined Deodorised and Bleached
    Further free fatty acids are generated during the above process of the oil, it is not done deliberately as it lessens the value of the oil but this is what really happens
    Even straight out cold pressed oils have some free fatty acids, a very small amount is always present, however for the production of biodiesel with any new oil this low amount is usually ignored
    So here in summary we have a basic understanding of what is a free fatty acid, as well as how they come about in new oils
    Now here is our situation in regards to WVO
    When it comes to used oil as in WVO, the fatty acids, will get detached due to heating as well as cooling of the oil on a continuous basis
    The shop heats up the oil when it opens and turns off the heat when it shuts, the thermostat in the fryer doing its trick as well as oxidation of the oil as it is in the open
    Besides, there is food cooked in the oil which will further break down the bonds of the fatty acids from the back bone they are attached to
    So quite a lot of the fatty acids can, and they do, become unattached from the backbone. They become free
    We now want to turn this WVO into biodiesel so we have to learn certain things about this batch of oil before we attempt to do it
    We know the qty of lye we need to do a conversion with perfect oil, in other words Zero or an extremely low amount of free fatty acids
    This is a known quantity based on the weight or volume of the material better still on a molar basis
    We already know that this WVO consists of an unknown mixture of fatty acids as well as free fatty acids
    In other words we do not have the exact amount of attached or free fatty acids
    We need to find the exact amount of catalyst we need to mix in so as to deal with the free fatty acids since we know what amount we need to catalyse a perfect oil
    We have to do a titration to establish the qty of base required to deal with those free fatty acids
    Titration is an indirect way of measuring the “acid value of the oil”
    This is how we find out the extra amount of base we need to add
    Again w
    e do know what quantity we need in an oil without them
    This amount obviously will have to be On Top of what is required to do the reaction with perfect or ideal oil, devoid of any free fatty acids
    We than calculate out what qty we need to do the job for our particular batch we are dealing with at the time
    Add the two together so we have our total qty of lye to take care of the attached fatty acids as well as the free fatty acids contained in the amount of oil we want to convert into biodiesel


    This extra amount of base will be “wasted” in the free fatty acids, we have to do it so as to make sure there will be enough remaining base to do the job for us, we must add the excess amount of base on top of the amount necessary to do the reaction
    So accuracy in calculating out the amounts of base is an absolute necessity so we don’t finish up with goop or soap
    It has to be done with every batch of used oil we want to turn into biodiesel
    Of course that is after we get rid of any foreign matter as well as any water in it, In other words well filtered and 100% dried out
    There is a post of mine that explains the basics of titration, as well as that, Tilly, has defined it on a later post
    That is the biggest issue facing the biodiesel producer either home based or commercial, dealing with unknown w v oils
    It is where most of the failures in the production of biodiesel originate or come from judging by the amount of post's on the subject

    Finally I will be more than happy to have any corrections on this post if some one out there spots something that should not be included
    4
    it is of great help
    75.00%
    3
    It is of some help
    25.00%
    1
    Cheers
    Chris
    Never give up :)

  • #2
    Re: Free Fatty Acids or FFA's in WVO How do they get there?

    Hi Chris
    Wander full explanation "Man with the Tongs".Cool stuff mate.Wander why I cant place any more reputation after clicking the scale CYBOR Legend Nerd.This definetly needs one.
    Heaps ahppening here to Chris.Will keep you posted.

    We can only do it together.
    Keep smiling and Shining
    Cheers
    Sauman

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