Man. Scientists and engineers love their acronyms. We just can't help it. There's a joke among engineers that if you don't create at least two acronyms on a project, you failed. So, today we deep dive into one of the most commonly misunderstood acronyms in the biofuels/ rendering/ oleochemical industry. - The famous (or infamous) M.I.U.
Most Fats Oils and Greases (FOG) are traded as commodities in the feed and biofuels markets. One of the most important properties affecting the price of a commodity in the marketplace is a the level of contaminants in the grease. In almost every situation you will hear about material being traded on a "2% MIU Basis". So what does this mean? MIU is an acronym which stands for three of the principal quality control tests used to determine common contaminants in FOG. The method by which these tests are conducted are governed by the American Oil Chemists Society (AOCS) www.aocs.org. The acronym stand for:
M) - Moisture and Volatiles
I) - Insoluble Impurities
U) - Unsaponifiables
So lets break these down:
M) - Moisture and Volatiles This test takes a sample and dries it in an oven or on a hotplate under vacuum to determine the amount of water and other volatile liquids that may be present in the oil.
I) Insoluble Impurities - This test is meant to detect the presence of finely divided solids in the oil or grease. The test is conducted by dissolving the grease in a solvent, and filtering it through a glass fiber filter. The contaminants trapped in the filter are then weighed to provide the amount of insoluble impurities in the oil or grease.
U) Unsaponifiable Matter - This test detects the presence of substances in an oil are grease which cannot be converted to soap. Natural fats and oils and their associated free fatty acids can be converted to soaps. This is an older test that was designed when most fats and greases were used as feedstock for making soaps. In modern trading it is used to detect gross contamination by petroleum oils or other contaminants which are liquid and not volatile. In this test, the sample is saponified with sodium hydroxide, then extracted with petroleum ether and water. The portion that is extracted in petroleum ether is dried in an evaporator and drying oven and is then weighed to provide the unsaponifiable residue.