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The 3/27 Conversion Test
by Maria "Mark" Alovert of Local B100
Over the past year, there's been a quiet revolution in biodiesel homebrewing quality control. On July 7, 2006 a new test was introduced, with experiments to support it, to the infopop forum community - the Jan Warnquist or 3/27 test. This test can tell you a great deal about the degree to which your oil (triglyceride) is converted into biodiesel (fatty acid methyl ester). The degree of conversion is probably the single most important factor in determining biodiesel quality. Prior to the introduction of the test, we had the choice of GC (gas chromatograph) testing which was too expensive to be useful to homebrewers, or viscosity and reprocessing tests that gave us only a crude measure of conversion and are far from quantitative
What can the Warnquist 3/27 Test Tell Us?
Good fuel, or bad fuel? The results from this test correlate closely with GC test results on many samples of fuel made by homebrewers. If the test is performed properly, and a batch of fuel passes, (there is no visible precipitate) then the fuel is likely to be converted very close to the ASTM standard for conversion of .24% total glycerides or better. Improving your process: When you want to find out if a change to your process has improved the result, this test allows you to compare batches and determine which is more converted. Monitoring your process: The test can be used in mid process to determine how long to run your reactor, or monitor your conversion at different stages in the process. Not Quantitative: While there must be some relationship between the amount of fallout and the degree of conversion, so far the test is not quantitative. We can’t say that a 1mm bead of oil fallout means “x percent” conversion and if you see a 2mm bead it's twice as impure.
How the test works:
The test relies on the fact that biodiesel is quite soluble in methanol, while triglyceride has a very low solubility in methanol. It is believed that diglycerides are partially soluble, but less so than monoglycerides. In essence, if any more than a trace of Triglyceride (unreacted oil) is present, it can be seen with this test. If Triglyceride is there, so are diglycerides and monoglycerides. The amount of remaining glycerides is a direct reflection the degree to which the oil was converted to biodiesel.
How to perform the test:
In a clear vial or test tube with a lid, measure 27 ml of room-temperature (68 f +/- 2 degrees for most accurate, repeatable, comparable results) methanol and dump exactly 3 ml of room-temperature, water-free biodiesel on top, then shake, and let settle. If you see oily material settle out in the next 30 minutes, then the fuel contains more than trace amounts of triglycerides, and therefore mono and diglycerides as well. If nothing settles out, you have made highly converted fuel.
The test can be performed on washed and dried fuel, or unwashed fuel. There have been very few discrepancies between washed and unwashed results of the same batch of fuel. Where there has been a difference, the washed (water wash) fuel tests slightly better. If you are testing unwashed fuel, allow it to settle at least until there is a clear separation of glycerine layer at the bottom. See next section for possible issues with unwashed fuel.
This can be done in any ratio of 9 parts methanol to 1 part biodiesel (for instance 25 ml biodiesel to 225 ml methanol is a more accurate volume to measure). Using syringes to measure small amounts is often more accurate than using graduated cylinders.
The spent test material can be re-used as your next batch of methanol/lye for production- the trace of BD, oil and intermediaries won't affect the results of your next batch.
If the ambient temperature is much different than 68f, use a water bath to control the temperature of the sample during the 30 minute test period.
Clean the vial well with isopropyl to remove all clinging oil droplets before using the vial for the next test.
Keep in mind:
It is very important to keep the methanol from being contaminated by water (such as water vapor in the air). Water getting in can cause a false fail. Many in the USA use Heet (in the yellow bottle) brand gas line antifreeze from auto parts stores. If you use your production methanol, keep the container it's stored in tightly sealed. You can test your production methanol and see if it gives the same result as Heet does. Purity of production methanol can vary.
It's important to keep the methanol from evaporating in the test vial or you'll get a false failure. Use a vial with a lid or a tube with a stopper, rather than an open container.
This test is sensitive to temperature, so doing it at warm temperatures can give a false pass, and doing it at cold temperatures can yield a false fail.
This test is fairly reliable and accurate but there are always exceptions and there are sometimes unexpected results. The results of the test may not compare exactly from one type of oil to another. The developer of the test stated that it would not work with fish oils due to differences in the carbon chain lengths.
The test is most accurate and consitent on washed, dried fuel. When testing unwashed fuel, other variables are being introduced into the test. Very high levels of soap may interfere with the test on unwashed fuel. More testing under a wider variety of conditons would be helpful to establish the limits of testing unwashed fuel.
It seems that it's important to add the biodiesel to the methanol and not the other way around- it sometimes does not mix well the other way around.
Introduction to conversion and why it is important:
Biodiesel quality is partially measured in terms of conversion- the extent to which oil becomes biodiesel rather than it’s unconverted state, triglycerides, or remaining in an intermediate state, in the form of monoglycerides or diglycerides.
Monoglycerides and diglycerides have properties of both oil and glycerin, and this makes them interact with water in ways that can cause problems in storage, causing rare conditions where contaminated fuel can burn poorly and clog injectors with carbon and clog filters with contaminated fuel. While these problems seem rare, poor conversion is a common element believed to be at the root of those few cases when problems do arise.
Monoglycerides and diglycerides can also remain liquid and in that state they seem to burn like biodiesel. They're impossible to detect visually under most conditions, until storage problems happen (when it's too late), so having an easy test for their presence has been a vital need for homebrewers. In the lab there are several expensive methods for finding them, and the ASTM specification for commercial biodiesel fuel quality stipulates the use of a gas chromatograph for detecting the exact percentage of monoglycerides, diglycerides, or unreacted oil in the biodiesel. The ASTM standard is expressed in terms of total glyceride and is .24%. This reflects only the glyceride portion of the tri, di and mono glycerides present in the final product.
Collaborative Biodiesel Tutorial - Copyright 2005