TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method further comprises: heating the glycerol-rich portion to a temperature of 65-90 degrees C before reacting the glycerol-rich portion with the acid to remove a portion of the methanol from it; and mixing the reacted product with one or more base compounds to produce a neutralized product (133) having a pH of 6-8, and removing one or more inorganic mineral scales by contacting the inorganic mineral scales with the reacted product or neutralized product, lowering a freeze point of water by adding the reacted product or neutralized product to the water, deswelling clay particles and/or polymer particles by contacting the clay particles and/or polymer particles with the reacted product or neutralized product, introducing the reacted product or neutralized product to a wellbore as a drilling fluid or as a component of a drilling fluid, removing corrosion from a metal by contacting the corrosion with the reacted product or neutralized product, reducing a formation of hydrates in a fluid containing one or more hydrate-forming constituents by contacting the fluid with the reacted product or neutralized product, or demulsifying an emulsion by mixing the emulsion with the reacted product or neutralized product. The step of decreasing the pH of the biodiesel byproduct comprises mixing the biodiesel byproduct with a second acid. Preferred Components: The mixture has a pH of 6-13, where separating the mixture comprises decreasing the pH of the mixture to 2-5. The pH of the mixture is greater than 9, where the pH of the reacted product is 2-3.5. The water and one or more second acids is added to the mixture having a pH of 6-13 to decrease the pH of the mixture to 2-5, where a mole ratio of the glycerol in the mixture to the second acids is 5:1-20:1, and a ratio of water to the second acids is 1:1-10:1. A molar ratio of the glycerol in the glycerol-rich portion to the acid comprising phosphorus is 5:1-1:5. The reacted product has a flash point of 66-200 degrees C and a freeze point of -25 degrees C to -65 degrees C. The first acid and/or the second acid comprise orthophosphoric acid, phosphorus pentoxide, one or more polyphosphoric acids and/or one or more metaphosphoric acids.