Recommended Quality Tests
by Graydon Blair of Utah Biodiesel SupplyINTRODUCTION
When making Biodiesel, there are several tests that you can do to ensure you produce high quality Biodiesel.
This page will cover several tests that we believe are great to integrate into your Biodiesel production routine.
If followed, they will help you not only make great Biodiesel, but will also help you understand
what is happening at all stages of the Biodiesel production process and how to deal with any problems that may arise.
The page is structured into stages of the production process to make the tests easy to follow.
QUALITY TESTS INDEX PRODUCTION STAGE: OIL COLLECTION & PREPARATION
- WATER CONTENT
- BIODIESEL TITRATION
QUALTY TEST: WATER CONTENT | BACK TO TOP Recommended Limit: Below 2500 PPM (or 0.25 % By Volume) Reason For Test:
This test looks for water content in the oil. If extremely wet is used to make Biodiesel, the water
will mix with the catalyst (Sodium or Potassium Hydroxide) and begin forming soap out of the oil.
When soap is formed it robs the catalyst from being able to fully react the oil into Biodiesel resulting in poorly converted fuel.
Excess soaps in Biodiesel can also potentially lead to unwanted emulsions during the washing process.
Description Of Tests:
There are three common ways to test for water in oil.
Each one listed below gets progressively more accurate.
Test #1: HOT PAN TEST (Accurate To Approximately 500 PPM, 0.05%)
Place about 30 mL of oil to be tested in a heated pan.
If the oil bubbles, crackles, or produces steam, it likely contains water. Additional Test Information: Hot Pan Test Method
Test #2: QUANTITATIVE WATER TEST (Accuracy Dependent On Measuring Devices)
Weigh 300 to 400 mL of oil using a scale accurate to at least 0.1 gram.
Heat the oil up to at least 250° F.
Allow oil to cool for about 10 minutes.
Reweigh the sample of oil and compare the weights.
Calculate the total water content. Additional Test Information: Quantitative Water Test Method
Test #3: SANDY BRAE WATER TEST (Accurate To 50 PPM, 0.005%)
Using a Sandy Brae Water Test Kit, test a sample of oil for water content.
Record gauge reading.
Calculate the total water content. Additional Test Information: Sandy Brae Water Test Kit Description
QUALTY TEST: BIODIESEL TITRATION (Testing Oil For Acid Content) | BACK TO TOP Recommended Limit: NaOH Titrations - <= 6, KOH Titration - <=9 Reason For Test:
When making Biodiesel, it's important to know what the acid level in the oil is.
This is because when Biodiesel is produced, one of the chemicals used will be a strong base.
Typically Sodium or Potassium Hydroxide. If the oil is very acidic, you'll need to compensate for this by adding more base than
normal to make the reaction occur. This is because part of your base chemical will be neutralized by the acid in the oil.
By knowing the acid content you'll be able to add enough extra base chemical so that there's enough left over after
neutralizing the acid to still make Biodiesel.
The method used to measure the acid content in the oil is called a Titration.
It's performed by taking a sample of oil, adding it to some pH neutral alcohol, typically isopropyl alcohol, adding a pH indicator to
the mixture and then slowly adding measured amounts of a solution of water with a small amount of the strong base chemical
that you'll be using to produce your Biodiesel with.
Once the basic solution neutralizes the acid in the oil, the pH will go higher (low pH = acidic solution, high pH = basic solution),
indicating that it's been neutralized. The pH indicator will then turn a different color to let you know that you've neutralized the acid.
There are several types of pH indicators that can be used to do a Biodiesel titration, but the most common is
Phenolphthalein. Phenol Red and Turmeric can also be used as well.
Description Of Test:
Create Titration Solution by adding 1 gram catalyst (either NaOH or KOH) to 1 Liter of water
Add 1 mL Oil sample to 10 mL Isopropyl Alcohol
Add 2-3 drops pH Indicator (Phenolphthalein, Phenol Red, or Turmeric Powder)
Add measured amounts of Titration Solution to oil sample
Record total mL added when mixture turns color
QUALTY TEST: METHANOL PURITY | BACK TO TOP Recommended Limit: 99.5% Pure Or Better Reason For Test:
Occasionally if methanol sits for long periods of time it can absorb moisture from the air.
If your methanol has been sitting for a while or if you've recovered the methanol, we recommend testing it for purity.
Usually, the impurity in Methanol is water. As in the case of oil, having water in the process can potentially lead to soap production
and potentially poorly reacted Biodiesel.
Description Of Test:
Fill testing vessel up to 1 liter mark with methanol
Measure & record temperature of methanol in vessel
Place hydrometer in vessel
Take measurement of hydrometer
Calculate methanol purity Click Here For Step By Step Instructions
QUALTY TEST: 27/3 BIODIESEL CONVERSION TEST | BACK TO TOP Recommended Limit: No Fallout Reason For Test:
This test is used to identify how well reacted the Biodiesel is. It helps to let you know if the chemical reaction
worked the way it was supposed to. If the fuel isn't well reacted, then it may need to be reacted again. Also,
poorly reacted Biodiesel can be the cause of emulsions when water washing Biodiesel.
This test has been well tested against the ASTM equivalent test (ASTM D6584) and found to correlate extremely well when performed
correctly. We highly recommend this test be performed on every batch. This test can also be run after washing as well.
Description Of Test:
Add 3 mL of Biodiesel to 27 mL of Methanol
NOTE: Both the Biodiesel and Methanol should be between 68° to 72° F
Shake for about 30 seconds & allow to sit for 5 minutes
The Methanol should completely absorb the Biodiesel
No fall out should be visible
Example Tests:
Vial On Left=Pass, Vial On Right=Failed
QUALTY TEST: SOAP CONTENT | BACK TO TOP Recommended Limit: NaOH Reacted Bio <=41 PPM, KOH Reacted Bio <= 66 PPM Reason For Test:
When Biodiesel is produced, a certain amount of soap gets produced right along with it.
When the Biodiesel is properly washed, soap levels should be greatly reduced. To ensure the Biodiesel
is finished being washed, we recommend testing the soap content of your Biodiesel. If soap levels are still high, the Biodiesel
can be rewashed.
Special Note If You Dry Wash Biodiesel
If you utilize dry washing in your Biodiesel production, we strongly recommend testing for soap content both before and after dry washing your Biodiesel.
This will let you know two things:
1) If the soap levels are being reduced enough and 2) If your dry wash media is ready to be replaced or regenerated.
Without testing for soap, the final Biodiesel product can look deceptively clean. A simple soap test will let you know
for sure.
Description Of Test:
Add 10 mL Biodiesel to 100 mL Isopropyl Alcohol
Add 15-20 drops Bromophenol Blue
Add measured amounts of Hydrochloric Acid until it turns yellow
Record the number of milliliters (mL) used
Calculate soap content
QUALTY TEST: WATER CONTENT | BACK TO TOP Recommended Limit: Below 500 PPM (or 0.05% By Volume) Reason For Test:
This test looks for water contet in the oil. If oil that is extremely wet is used to make Biodiesel, the water
will mix with the catalyst (Sodium or Potassium Hydroxide) and begin forming soap out of the oil. When soap is formed
it robs the catalyst from being able to fully react the oil into Biodiesel resulting in Biodiesel that may not be
completely reacted. Also, excess soaps in Biodiesel can potentially lead to unwanted emulsions during the washing process.
Description Of Tests:
There are three common ways to test for water in oil.
Each one listed below gets progressively more accurate.
Test #1: HOT PAN TEST (Accurate To Approximately 500 PPM, 0.05%)
Place about 30 mL of oil to be tested in a heated pan.
If the oil bubbles, crackles, or produces steam, it likely contains water. Additional Test Information: Hot Pan Test Method
Test #2: QUANTITATIVE WATER TEST (Accuracy Dependent On Measuring Devices)
Weigh 300 to 400 mL of oil using a scale accurate to at least 0.1 gram.
Heat the oil up to at least 250° F.
Allow oil to cool for about 10 minutes.
Reweigh the sample of oil and compare the weights.
Calculate the total water content. Additional Test Information: Quantitative Water Test Method
Test #3: SANDY BRAE WATER TEST (Accurate To 50 PPM, 0.005%)
Using a Sandy Brae Water Test Kit, test a sample of oil for water content.
Record gauge reading.
Calculate the total water content. Additional Test Information: Sandy Brae Water Test Kit Description
ASTM LABORATORY TESTING (D6751 Panel) | BACK TO TOP Reason For Test:
The Biodiesel ASTM Testing Panel (ASTM D 6751) is required to be performed on Biodiesel
if it is going to be sold as a fuel for use in on-road vehicles. Results from these tests are required to be
submitted to the EPA before a certificate to produce and sell Biodiesel commercially will be issued.
The IRS also requires proof that your Biodiesel passes these tests before they'll allow you to take certain tax credits as well.
Because the ASTM D6751 is the standard against which Biodiesel is tested (and must pass)
before it's allowed to be sold commercially, many people that produce their own Biodiesel like to see
"just how close" they are getting to this standard. In many cases, if good Biodiesel production
techniques are practiced and the tests laid out above are used, it's possible to easily pass these tests.
Description Of Tests:
These tests are typically performed by an independent testing laboratory. The test procedures are specified by a series of
ASTM standardized tests that are included in the D6751 testing panel using extremely accurate testing instruments. Fuel is tested
for a wide range of characteristics and contaminants. Such things as methanol content, water content, gel point,
cetane value, cloud point and more are all tested for. Click here to learm more about each ASTM test.
We have partnered with a lab that is capable of performing these tests.
We've created several test packages that most people like to have performed before they run the full ASTM D6751 panel.
Everything from a simple conversion test (ASTM D6584) to a package containing the most commonly failed tests to
the full ASTM D6751 test panel. Our customers have found this a great way to see "just how close" they really are to the commercial standard. To learn more about this testing service and the test packages available, click here
ADDITIONAL QUALITY TESTS | BACK TO TOP
There are actually quite a few additional tests that are used by Biodieselers in their quest to make great Biodiesel.
While not all the tests we've seen are required specifically to make high quality Biodiesel, these additional tests can help you further understand
what it is you've produced and possibly help you fix problems along the way. This list was complied by our good friend
Rick over at B100 Supply. Click here to see a full list of tests
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