Summary of Titration Methodologies
We receive a lot of questions regarding “grease quality” and we’ve discovered that people titrate their oil in a number of different ways. As a result, Springboard Biodiesel, LLC always refers to the Free Fatty Acid (FFA) percentage of the oil, and we don’t encourage people to try and process oil in excess of 5% FFA (we also don’t encourage people to eat at restaurants that allow their grease to reach 5% FFA – and we’re not gourmands).
However, in order to clarify the various titration techniques and, importantly, results, we’ve put together the following cheat sheet.
FFA
Self explanatory. You’re looking for less than 5%. The lower the better.
Typical KOH titration
This will tell you how much KOH (in grams of KOH per liter of waste oil) you will need to completely neutralize the FFA of your oil. Thereafter, you will add a “base” amount to turn the fully neutralized grease into ASTM-compliant biodiesel (in a BioPro™, of course, we have taken care of you by supplying an exact recipe for all BioPro™ batches assuming 5% FFA or less oil)
Typical NOH titration
As with the method above, this reveals how much NaOH (again In grams of NaOH per liter of waste oil) you will need to completely neutralize the FFA of your oil. Thereafter, you will add a “base” amount to turn the fully neutralized grease into ASTM-compliant biodiesel (in a BioPro™, of course)
KOH titration + base
Here the titrator is adding the base amount needed to turn his/her grease into ASTM-compliant biodiesel (If you subtract 7 – the KOH base number – from all of the results you will see the same number as listed under “Typical KOH Titration”). While 7 grams is somewhat subjective, it represents a solid average for small-scale biodiesel producers)
NaOH titration + base
Results reflect the addition of 5.5, the base number. Same methodological rationale as above – same “solid average” for 5.5 grams
Remember that the water content of all oils is key. The less water, the better the reaction!
Frequently asked questions
How do I convert a KOH or NaOH titration number to percent FFA?
First subtract the base amount: 7 from a KOH result or 5.5 from an NaOH result. Then divide by 1.8 for KOH or by 1.3 for NaOH. The result is the approximate free fatty acid (FFA) percentage of the oil. For example, a KOH titration of 16 equals about 5% FFA.
To go the other direction, use (%FFA × 1.8) + 7.0 for KOH, or (%FFA × 1.3) + 5.5 for NaOH.
What is the difference between a KOH titration and an NaOH titration of waste oil?
Both tests measure how much catalyst is needed to neutralize the free fatty acids in waste oil. The difference is which catalyst you use. A KOH titration gives grams of potassium hydroxide per liter of oil, and an NaOH titration gives grams of sodium hydroxide per liter.
Because the two chemicals differ in strength by weight, the numbers are not interchangeable. For example, the typical base amount added for making biodiesel is about 7 grams per liter for KOH and 5.5 grams per liter for NaOH. Always note which catalyst a titration number refers to.
What does the base amount of 7 grams KOH or 5.5 grams NaOH mean in titration?
The base amount is the catalyst needed to convert fully neutralized oil into ASTM-compliant biodiesel. It is added on top of the catalyst consumed in neutralizing the oil's free fatty acids. The standard figures are about 7 grams per liter for KOH and 5.5 grams per liter for NaOH.
Some people report titration results with the base amount already included, and others report only the neutralization amount. Subtracting 7 (KOH) or 5.5 (NaOH) from a “titration plus base” number gives the typical titration figure. These values are somewhat subjective but are solid averages for small-scale producers.
Do I need to titrate used cooking oil before making biodiesel in a BioPro?
For typical used cooking oil, no. The BioPro runs an acid-catalyzed esterification before the base reaction, and each batch follows an exact recipe designed for oil at or below 5% free fatty acids (FFA). This removes the need to titrate typical used oil.
If you are unsure about a batch of oil, a Go/No-Go kit can show within seconds whether its FFA is below 5%. Water content also matters: the drier the oil, the better the reaction.
Why does Springboard Biodiesel describe oil quality as percent FFA instead of a titration number?
Percent free fatty acids (FFA) is an unambiguous measurement, while titration numbers depend on the method used. People titrate waste oil in different ways: some use KOH, some use NaOH, and some include the base amount in their result while others do not. The same oil can therefore produce several different titration numbers.
Stating quality as percent FFA avoids that confusion. For BioPro processing the target is simple: less than 5% FFA, and the lower the better.
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