Best of the Tests 
 

Tests for Finished Biodiesel

ASTM Laboratory Testing

ASTM D6751 is a battery of tests that are the accepted American Standard for testing B100 biodiesel intended for use as blend stock. A full battery of tests cost from $1000 to $3000 per sample making it too expensive for homebrewing. It is not an accepted standard for neat or pure biodiesel. Below is a table that outlines the tests that compose ASTM D6751

Property.....................................	Method............	Limits............................	Units......
Flash point, closed cup	D 93	130 min	° C
Water and sediment	D 2709	0.050 max	% volume
Kinematic viscosity, 40 ° C	D 445	1.9 – 6.0	mm2/s
Sulfated ash	D 874	0.020 max	wt. %
Total Sulfur	D 5453	0.05 max	wt. %
Copper strip corrosion	D 130	No. 3 max
Cetane number	D 613	47 min
Cloud point	D 2500	Report	° C
Carbon residue	D 4530	0.050 max	wt. %
Acid number	D 664	0.80 max	mg KOH/g
Free glycerin	D 6584	0.020	wt. %
Total glycerin	D 6584	0.240	wt. %
Phosphorus	D 4951	0.0010	wt. %
Vacuum distillation end point	D 1160	360 °C max, at T-90	% distilled

For more information on ASTM 6751 see Biodiesel Analytical Methods by the NREL

My Opinion - What can I say.... This is the only official standard we have and it's too expensive for homebrewers to use as a standard.

Back to Top

The pHLip Test

The pHLip test is a commercial test that was designed as a "Firewall" for bad fuel in the biodiesel distribution chain.  It is a simple test consisting of a vial of red liquid, to which you add your sample of biodiesel, flip end over end 10 times and wait 10 minutes.  It will tell you if your biodiesel is high quality or if it fails for total glycerine, soap content, free glycerine, oxidation and catalyst contamination.

This is the most thoroughly and analytically vetted test we have short of ASTM testing to tell if we have high quality biodiesel.  It has been compaired against ASTM testing repeatedly by dozens of firms.

My Opinion - I think it's a really good test.

Clarity Testing Finished Biodiesel for Water

This is a visual inspection of the finished biodiesel. Water free biodiesel will be clear. The common method of testing is to put a sample in a jar and if you can read a newspaper through the biodiesel then it passes the test. For larger batches, the ability to see the bottom of a drum of biodiesel clearly is often used. This is a good test, however it does not detect water that is dissolved in the biodiesel. Water dissolved in biodiesel will be evenly distributed on a molecular level throughout the biodiesel. There is some debate as to the effect of dissolved water on certain types of diesel engines. 

One important fact is that hot biodiesel will hold more dissolved water than cold biodiesel. This results in hot or warm biodiesel passing the test and cold biodiesel failing the test. It is important to pass the test when the biodiesel is slightly colder than the expected operating temperature.

My Opinion - It's the best we have, but can give false results if your biodiesel is too warm.

Back to Top

Cloud Point Testing

This test is performed by placing a sample of finished biodiesel in the freezer and watching it for cloudiness. The temperature at which the biodiesel first turns cloudy is the cloud point. This test is important for winter fuel. It is related to the "Gel Point Test". The cloud point is near the temperature at which your filter will clog from frozen biodiesel.

My Opinion - Pretty Much Mandatory for Winter Biodiesel, that is if you don't want to be changing filters on the side of the road in knee deep snow.

Back to Top

Gel Point Testing

In this test you place a sample of finished biodiesel in a freezer and record the temperature at which the biodiesel starts to gel. This is an important test for winter fuel. Simply put, you don't drive on biodiesel at temperatures below the gel point. 

My Opinion - Mandatory for winter driving on biodiesel, that is if you don't want to have your car or truck towed to a heated garage to thaw out.

Back to Top

The Dr Pepper Viscosity Test

Back to Top

The Methanol Test from JTF or the 27/3 Test

This test found on JTF suggests that dissolving finished  biodiesel into methanol is a test for quality.  As with much information on JTF, this one has good and bad information.  JTF states "The biodiesel should be fully soluble in the methanol, forming a clear bright phase. If not, there is pollution in the biodiesel. Each ml of undissolved material corresponds to 4% by volume. Is there any undissolved material at the bottom of the measuring glass? If there is, your reaction is not complete and this is causing you trouble with the water test."  Testing has found that the clarity of the methanol is effected by enough different things to make clarity of the methanol meaninless.  Also attempts at correlating the volume of undissolved material to conversion have not been successful.

There has been a good bit of validation testing performed on this test by the people posting on the infopop forum.  They found that if a portion of the biodiesel does not dissolve in the methanol then there are quality problems.  It is futher discussed on infopop after being introduced to the board by Tilly. 

Neither Triglycerides or Diglycerides are soluable in dry  methanol, but Monoglycerides and Biodiesel will dissolve in dry biodiesel. If significant Triglycerides or Diglycerides present will fall to the bottom of the test.  

To perform the test add 1 part biodiesel to 9 parts methanol, by volume.  On infopop many use 3 mL of biodiesel and 27 mL of methanol and call the test either the Jan Warnqvist test or the 27/3 test.

Triglycerides and Diglycerides will form a precipitant on the bottom.  Only a liquid precipitant that collects together to form a bead or bubble that rolls arond on the bottom of the test is significant.   If you have a liquid precipitant then your biodiesel is under converted.

Your methanol should be dry and you perform this test at room temperature, as most of the validation testing on this procedure has been performed under those conditions.

Back to Top

The Dr Pepper Reprocess Test 

The basic premise is that reprocessing quality biodiesel with even a little catalyst will cause it to gell. My expericnces with this test are that sometimes it does not give a clear go/nogo indication.  The methanol test is much easier to perform and gives solid indications.

My opinion... use the methanol test.

Back to Top

Initial Feedstock Testing

Titration Test for WVO

This titration test is used to determine the Free Fatty Acids (FFA) content of Biodiesel. It also is used to determine how much catalyst a particular oil needs in it's recipe for making biodiesel. There are a number of instructions on the internet. Almost all of them will result in the same recipe. This test is required if you desire to homebrew high quality biodiesel.

B100 Supply has all the labware you need to perform this test. The Biodiesel Titration Kit has everything you need to perform this test. The Deluxe Biodiesel Titration Kit has improved labware to make titrations fast and easy.

My Opinion - Required Test - Making high quality fuel consistantly requires the titration test.

Back to Top

The Frying Pan Test

Back to Top

The Hot Pan Test

This test is a variation of the Frying Pan Test and used to determine if water is dissolved in WVO.  In this test you heat the pan to temperature first then add the oil.  You are looking for tiny bubbles to form, indicating the presence of water.

My Opinion - It works and you need to test for water before processing.

Back to Top

Quantitative test for water 

This test is used to determine quantitatively how much water is in your WVO.  In essence you weigh a sample, boil out the water, then weigh it again.  The difference in weights is used to determine the percent water content of the WVO.


My Opinion - It works, and you need to test your WVO for water.

Back to Top

Specific Gravity of Methanol

Specific Gravity is a valid test for measuring the purity of methanol. The tool for measuring Specific Gravity is a hydrometer and can be used for measuring the purity of either methanol or ethanol. When testing the purity of methanol a special hydrometer is used that measures on the Proof scale where 200 proof = 100% methanol and 0 proof is 100% water. 

My Opinion -- Good test for methanol purity - required if you recover your methanol.

Back to Top

Mid Process Tests

Soap Test Titration

This test is used to determine how much soap is in biodiesel. It is a good test that will help you to predict how your biodiesel will wash. It is also used by those that use magnasol or synthetic magnesium silicate instead of water washing to determine how much magnasol to use. It is not part of ASTM D6751 but does provide useful information. 

This test requires an indicator called Bromophenol Blue and can be performed using the labware in either of our Titration Kits.

My Opinion - Good Test that provides useful information, but not absolutely required for making biodiesel

Back to Top

The Drying Test

To determine if your biodiesel is finished washing, draw a 1/2 cup (100mL) sample from your biodiesel and place in an open top container and place in a warm dry location.  If the sample becomes clear within an hour or two then your finished washing.  If the biodiesel remains turbid or hazy then continue washing.  

My Opinion - Undecided

Back to Top

The Rest of the Tests
 

pH Testing 

In this test the biodiesel is supposedly good if the pH is neutral (7). pH testing will tell you how strong an acid or base is. It only works in solutions that contain water. pH testing dry oil or dry biodiesel does not work. You will get erratic readings that are totally meaningless. pH testing the wash water or wet biodiesel or wet oil will work, however the a pH reading has no useful information pertaining to making biodiesel or it's quality.

The only place where pH is important is as an indicator of when to stop our titration test. In this case it is the titration number that is important not the pH.

My Opinion - Not a Valid Quality Test for Biodiesel

Back to Top

Reprocess Test from JTF

In this test you reprocess a sample batch to see if any more glycerine falls out. This test can give false indications. While glycerine does fall out if you are very badly under reacted, not having glycerine fall out does not mean the sample is anywhere near ASTM spec. The excess methanol in the reprocessed biodiesel will tend to keep any glycerine freed up by transesterification suspended in solution and undetectable to the naked eye.

My Opinion
-- Useful to identify grossly under reacted biodiesel. 
-- Not sensitive enough to identify high quality fuel.

Back to Top

Specific Gravity of Biodiesel

Specific Gravity is a valid test that is used in the petroleum distribution chain to test diesel fuel. The book From the Fryer to the Fuel Tank originally recommended this test was also valid for biodiesel. That is not the case. Biodiesel is a mixture of Fatty Acids that have been attached to methanol. More properly methyl esters of fatty acids. The specific gravity of the finished product will depend on the specific gravity of the feedstock, which varies considerably from oil to oil as well as the temperature of the sample and the amount of contaminates in the biodiesel such as methanol and soap..

My Opinion -- Not a Valid Quality Test for Biodiesel

Back to Top

The Wash Test from JTF

This test is conducted by placing finished biodiesel in a jar with water and shaking for 10 seconds or more. If the biodiesel and water separate within 30 minutes regardless of the color or clarity of either the biodiesel or the water it is supposedly high quality fuel. If an emulsion forms that does not separate out in 30 minutes you need to improve your "processing techniques"

This test can give a false results. It can separate within 30 minutes and still be loaded with contaminates. Water hardness has a big influence on the test. Using soft (rainwater) can get you a stable emulsion indicating failure, while hard water on the same sample can indicate high quality fuel.

My Opinion - Two thumbs down.

Back to Top

The Shakem Up Test

This test is widely used by home brewers to determine if their biodiesel is finished washing.  The test calls for equal parts of water and biodiesel.  Shake. If the biodiesel and/or water separate quickly and the wash water is clear then the biodiesel is finished washing.  This test does not provide enough contact between the water and the biodiesel to provide accurate information.  The water on bottom can still be clear while the biodiesel is loaded with soap and glycerine.

My Opinion - Can be misleading

Back to Top

Wash Water Clarity Test

This test is widely used by home brewers to determine if their biodiesel is finished washing.  Basically, you check the wash water and if it's clear (as in not white from soap), then you have finished washing.

My Opinion - Undecided

Back to Top

pH Testing the Wash Water

Back to Top

Smelling for Methanol

Back to Top