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 we 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
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 we 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
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