What are Free Fatty Acids?
Again, vegetable or animal oils and fats — what we make biodiesel from — are triglycerides, composed of three chains of fatty acids bound by a glycerine molecule. (See above, How the process works.) Free fatty acids (FFAs) are fatty acids that have become separated from the triglycerides, leaving diglycerides, monoglycerides and free glycerine. This is caused by heat, water in the foods cooked in the oil, or oxidation. The hotter the oil gets and the longer it’s cooked, the more FFAs it will contain. As glycerine is an alcohol (glycerol), a fatty acid attached to it (a glyceride) forms an ester. A “transesterification” is the conversion (switching) of one ester into another — a glyceride ester into an alkyl ester in the case of biodiesel, where methanol (or ethanol) replaces the glycerine. An “esterification” is the conversion of a non-ester into an ester. FFAs are non-esters. FFAs are converted into esters by acid esterification in the first stage of the two-stage acid-base biodies
