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Biodiesel Quality Testing
Best of the Tests
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| 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 |
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.
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.
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.
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.
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.
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."
Neither Triglycerides or Diglycerides are soluable in dry methanol, but Monoglycerides and Biodiesel will dissolve in dry methanol. 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. Testing has shown that for the test to appromimate ASTM level conversions the original 25ml of biodiesel and 225ml of methanol need to be used.
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 after about 5 minuites, then your biodiesel is under converted.
Your methanol should be dry and you perform this test at room temperature, The test has been found to be temperature sensitive. Hot biodiesel straight off the processor can give false readings as can using cold methanol stored outside in winter.
The basic premise is that reprocessing quality biodiesel with even a little catalyst will cause it to gell. This is a functional test. It is a bit complicated and some have had trouble getting and intrepreting the results. The methanol test is much easier to perform.
My opinion... use the methanol test.
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.
My Opinion - Required Test - Making high quality fuel consistantly requires the titration 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.
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.
Specific Gravity is a valid test for measuring the purity of methanol. The tool for measuring Specific Gravity is a hydrometer. It 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.
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 HCL acid..
My Opinion - Good Test that provides useful information, but not absolutely required for making biodiesel
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 - A good test
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 this test is proposed on JTF as a quality test for finished dry biodiesel.
A case can be made for using pH to test wet biodiesel as an indication on when to stop washing, But even in that case you would be using a second rate test when better tests are avilable.
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
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.
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. It can be used to identify a sample as either biodiesel or vegetable oil. It can also be used to tell the difference between grossly undreacted fuel and high quality fuel. It can not be trusted to tell you the difference between fuel that is 95% converted and fuel that is 98% converted.
My Opinion -- one thumb down for using this to accurately measure conversion, one thumb up for using it to tell if that drum is wvo or bio.
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.
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. The results of the test depends on the water you are using. If you always use the same water, then you may be able to adjust the test to fit your needs.
My Opinion - Can be misleading
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. This tests works for some people and not for others depending on the hardness of your water. If you have soft water, you can wash forever and it will never get clear.
My Opinion - works for some, does not work for everyone.
