Biodiesel Tutorial

Intro To Biodiesel
Drying WVO
Biodiesel Recipes
Biodiesel Safety
Appleseed Reactor
Eco-System Processor
More Processors
Processor Upgrades
Methanol Recovery
Dry Washing Biodiesel
Water Washing
Drying Biodiesel
Fuel Dispensing
Dealing with Byproducts
Biodiesel Chemistry
Quality Testing
Conversion Tests
Water Tests
The Important Tests Print E-mail

Written by Rickdatech


Clarity Testing Biodiesel

1) Testing finished biodiesel for water.

Water in our biodiesel will make it cloudy or turbid. If the biodiesel is clear enough to read a newspaper through a sample then conventional wisdom is that it's dry enough to use in a vehicle.

The test is temperature dependent since hot biodiesel can hold more water without going cloudy than cold biodiesel. To make sure you have your biodiesel dry enough to use, put it in the refrigerator and chill it down below the coldest temperature your batch of biodiesel is likely to see. If it's going to be used right away then look to the nightly lows. If it's going to be stored long term, then look to the historical lows for the period you expect to store it. If the biodiesel gels up before going turbid then you have dry biodiesel.

The problem with this test, is that ASTM requires less than 500 ppm of water in biodiesel that is to be blended with diesel and biodiesel will hold 1500 ppm of water before going cloudy. So we can pass this test and fail for ASTM water levels. To Make sure your fuel meets the ASTM standards, use the Carbide Manometer or Sandy Brae test.


2) Cloud Point Testing

As biodiesel cools it will start forming crystals of frozen biodiesel. This is different in appearance from wet biodiesel. A little experience at freezing biodiesel will give you the experience to tell the difference. When biodiesel starts to crystallize, it will also start to clog filters, so it's important to know when to take the gasser and when it's warm enough to use the diesel. To perform the test stick a thermometer in the biodiesel and check it every so often recording the temperature at which the crystals start forming.

3) The 3/27 Test

This test will give you an indication of how well you converted your WVO into biodiesel. WVO (Triglycerides) will not dissolve in methanol, but biodiesel will. To perform the test, add 3 ml of biodiesel to 27 ml of methanol and swirl it around a bit. Any unreacted oil will quickly fall to the bottom of the methanol. Partially converted biodiesel can fallout as well over time. It will usually fall out in about five minutes, but can take longer.

The ratio of biodiesel and methanol is important. The original test, as reported by Jan Warnqvist on the Journey to Forever web site, used 25ml of biodiesel and 225ml of methanol. The original recipe should be used if you are seeking ASTM level conversions. With less than 25ml of biodiesel your eye may not be able to detect the fallout at near ASTM levels.

Temperature is important with this test. It should be conducted with both the oil and the methanol at or near 70°F. If either are too hot then you can get a false pass. If either is too cold, you can get a false fail.

Read More on the 3/27 Test

4) Testing WVO for Water

Biodiesel and SVO used as a fuel need to be very dry, with less than 0.05% or 500 ppm of water.  Quantitatively testing down to that precision calls for a precision test like the Carbide Manometer or the Sandy Brae test. However when testing feedstock oil for making biodiesel we do not need to be so precise. Oil with more than aobut 3% water will be difficult to process. The higher the titration, the more sensitive the oil is to water content. Springboard Biodiesel has posted a chart that they developed showing how water content and FFA levels interact when useing the Acid Esterification process they recommend for use with the BioProTM. Basically with low titration oils water content below 1% is suitable for use as biodiesel feedstock. We can reach this level of precision quantitatively using the weigh/heat/weigh method of testing for water in biodiesel.

The test is not hard. It can be dangerous if you don't pay attention. The test simply calls for weighing an oil sample, then heating that oil sample to 250°F and weighing again. The difference in weights is the weight of the water in the original sample. To get the percent water content of the WVO divide weight of the water by the weight of the original sample and multiply by 100.

Biodiesel WarningsNow to explain the dangerous part. When the oil reaches 212°F, the boiling point of water, it can boil violently throwing boiling hot oil dozens of feet in every direction. The water in the bottom of the pan will be pressurized by the weight of the oil on top of it. As we heat it under pressure it becomes superheated. Superheated water only needs a little jar or bump and it all becomes steam in a flash. That sudden expansion of the water under the oil is like a little explosion. It will send the hot oil everywhere. So keep the oil stirred up to prevent water from collecting on the bottom and keep the pan covered when not stirring.

Read More on Testing Water for Oil


5)Titration Testing WVO

In this test we determine how much catalyst is needed to make a specific batch of WVO into biodiesel. There are actually two reactions taking place when we make biodiesel. The first is that we convert the bad WVO or Free Fatty Acids (FFA) into soap. In this reaction our lye is consumed in the process of making soap. The second and slower reaction is converting good WVO or Triglycerides into biodiesel. For the second reaction our lye acts as a catalyst and is not consumed. We titrate our WVO to find out how much lye will be consumed in the first reaction. That way we can build our recipe with just enough lye to ensure both reactions take place as they should.

Since this test is the one that beginners find the most intimidating, I have dedicated a whole post to Titrating WVO.



0 #1 robertcoogan 2012-10-12 02:59
For water testing I do something a bit more basic - I have an electric skillet about 10 inches wide that I will heat up to about 130° F. Then I pour about a couple of tablespoons' worth of filtered WVO in the pan. If it bubbles, it is useless. If it splatters, it may be salvageable (I have about a 75% success rate with making this into viable biodiesel). If there is no reaction, the WVO is perfect for processing. Simplistic, but it works very well.


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Making Biodiesel requires the use of flammable, toxic liquids and strong caustics to make a fuel. No matter what safety precautions are put in place or what equipment you use, making biodiesel will never be a safe hobby and can place you, your property, and your family at risk of injury or even death. Make Biodiesel at your own risk.


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