Where does glycerin come from?

Up until 1889, people didn’t know how to recover glycerine from the soap-making process, so commercially produced glycerin mostly came from the candle-making industry (remember, back then candles were made from animal fats).

In 1889, a viable way to separate the glycerin out of the soap was finally implemented. Since the number one use of glycerin was to make nitroglycerin, which was used to make dynamite, making soap suddenly became a lot more profitable! I have an untested theory that you could trace the roots of most big soap-makers (and the “fall” of the small, local soap-maker) to about this time in history.

The process of removing the glycerin from the soap is fairly complicated (and of course, there are a lot of variations on the theme). In the most simplest terms: you make soap out of fats and lye. The fats already contain glycerin as part of their chemical makeup (both animal and vegetable fats contain from 7% – 13% glycerine). When the fats and lye interact, soap is formed, and the glycerin is left out as a “byproduct”. But, while it’s chemically separate, it’s still blended into the soap mix.

While a cold process soap-maker would simply pour into the molds at this stage, a commercial soap-maker will add salt. The salt causes the soap to curdle and float to the top. After skimming off the soap, they are left with glycerin (and lots of “impurities” like partially dissolved soap, extra salt, etc.). They then separate the glycerin out by distilling it. Finally, they de-colorize the glycerin by filtering it through charcoal, or by using some other bleaching method.

Glycerin has lots of uses besides being used to make nitroglycerin (note: glycerin is not an explosive substance by itself. It has to be turned into nitroglycerin before it becomes explosive, so it’s safe to work with in your kitchen). Some uses for glycerin include: conserving preserved fruit, as a base for lotions, to prevent freezing in hydraulic jacks, to lubricate molds, in some printing inks, in cake and candy making, and (because it has an antiseptic quality) sometimes to preserve scientific specimens in jars in your high school biology lab.

Glycerin is also used to make clear soaps. Highly glycerinated clear soaps contain about 15% – 20% pure glycerin. Known as “Melt and Pour” soaps, these soaps are very easy for the hobbyist to work with. They melt at about 160 degrees Fahrenheit, and solidify fairly rapidly. Because of their high glycerin content, the soaps are very moisturizing to the skin. Unfortunately, this high glycerin content also means that the soaps will dissolve more rapidly in water than soaps with less glycerin, and that if the bar of soap is left exposed to air, it will attract moisture and “glisten” with beads of ambient moisture.

These downsides, however are more than compensated by the emollient, skin loving and gentle nature of this soap which is especially good for tender skin and children.

(1) The pure chemical product is called Glycerol (which shows that it is an alcohol), while the impure commercial product is called Glycerin. This is a technical complexity, so for this article, I’m sticking to the more familiar term, Glycerin.

Chemically there are Five Grades of Glycerine

USP GLYCERIN(E) is a clear, almost colorless product for uses requiring glycerine of high purity with taste and odor characteristics desirable for pharmaceutical and food purposes. The designation USP is an abbreviation of U.S. Pharmacopeia and signifies that the glycerine thus designated meets or exceeds the standards established in U.S.

Pharmacopeia (USP XXII, 1990) monograph, Glycerin. The USP designation has official legal status in the United States since the U.S. Pharmacopeia has been incorporated by reference in various statutes and regulations governing drug and medical practices, of which the federal Food. Drug. and Cosmetic Act is the most significant. USP glycerine is commonly available commercially at anhydrous glycerol content levels of 96%.99.0% and 99.5%. Concentrations above 99.5% are also available commercially.

CP GLYCERINE or chemically pure glycerine is generally understood to be of the same quality or grade as USP glycerine,but this term is considered generic in the United States because it does not reflect compliance with any official quality requirements or specifications a s does the USP designation.

FOOD GRADE GLYCERINE in the United States meets the requirements outlined in the monograph Glycerin contained in the Food Chemicals Codex prepared by the Committee on Food Protection of the National Research Council. Food grade requirements are similar to USP standards. Within the European Economic Community, glycerine for use in food products must comply with Council Directive 78/663/EEC which specifies the standards of purity for emulsifiers,stabilizers thickeners, and gelling agents for use in foods.

HIGH GRAVITY GLYCERINE is a designation used in the United States for a commercial grade of glycerine that is clear,almost colorless and conforms to Federal Specification 0-G-491C issued November 14, 1983 by the General Services Administration. This product also conforms to Standard Specification for High-Gravity Glycerin, D-1257, issued by the American Society for Testing and Materials (ASTM). This grade must contain not less than 98.7% glycerol. It is commonly supplied at not less than 99.O% concentration.

DYNAMITE GLYCERINE in the United States meets all the High Gravity grade specifications except color, but it cannot be darker than the Federal Color Standard. In Europe, glycerine for use in explosives is defined by Specification 21D for dynamite glycerine issued by the Nobel Explosives Company Ltd. The British Standards Institution has also issued a standard specification for this grade of glycerine as British Standard Specification for Dynamite Glycerol.

What is the most important use of crude glycerine?

Glycerol / Glycerin is a major byproduct in the biodiesel manufacturing process. In general, for every 100 pounds of biodiesel produced, approximately 10 pounds of crude glycerol are created. As the biodiesel industry is rapidly expanding, a glut of crude glycerol is being created. This glycerol is expensive to purify for use in the food, pharmaceutical, or cosmetics industries, biodiesel producers must seek alternative methods for its disposal. Various methods for disposal and utilization of this crude glycerol have been attempted, including combustion, composting, anaerobic digestion, animal feeds, and thermochemical/biological conversions to value-added products. Businesses and researchers from around the globe are currently engaged in research and development projects, with the primary goal of developing Glycerin / Glycerol economically viable technologies capable of utilizing this overabundant resource.

A newly developed technology in the U.K. allows glycerin to be burned in off-the-shelf diesel generators that are used in combined-heat-and-power applications. The technology was developed by U.K.-based Aquafuel Research Ltd. According to Paul Day, Aquafuel’s chief executive officer, the technology is now commercially available.

The process uses standard diesel generators, which are altered slightly to run on a new combustion cycle, which is referred to as the McNeil cycle. “The basics of the engine, the fuel injection, the pistons and cylinder are not changed at all,” Day says. Paul Day estimates that 1 ton of glycerin will produce approximately 1.7 megawatt hours of electricity and approximately 2 megawatts of heat. In addition, the process creates few emissions.

An European company is working on a technology to use glycerin in plastics, that would use glycerin as a feedstock to produce plastics. Ireland-based Biobode Ltd. is developing this technology. Historically been difficulty to use glycerin to make plastics because the process created a cross-linked polymer with no significant commercial value. For biological conversions of crude glycerol, the glycerol serves as a feedstock in various fermentation processes.