TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The mixture of a biological origin is a mixture of vegetable or animal origin, preferably vegetable oils, animal fats and/or fish oils. The vegetable oils or fats are sunflower, rape, canola, palm, soybean, hemp, olive, linseed, peanut, castor, mustard, coconut oils and/or oils contained in the pulp of pine-trees. The animal oils or fats are bacon-fat, lard, tallow and/or milk fats. The vegetable oils and fats are derived from plants selected by means of genetic manipulation.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: In the process, recycled oils or fats of the food industry, of both animal and vegetable origin, are used. The process is carried out: at 80-150 degrees C and a pressure of 5-30 bar; in two phases, where the first phase is carried out at a higher temperature than the temperature of the second phase; in a single closed stirred reactor (CSTR); and in two closed reactors in series, where the first reactor operates at a higher temperature with respect to the second reactor. The first phase is carried out at 80-150 degrees C and a pressure of 5-30 bar, for 1-5 hours. The second phase is carried out at 50-100 degrees C and a pressure of 10-30 bar, for 3-10 hours. In the process: 0.02-1 meq/l of acid is used; a quantity of methyl-tert-butyl-ether, expressed as molar ratio with respect to the triglycerides contained in the mixture of a biological origin of 4:1-15:1, is used. Preferred Components: The tert-butyl-glycerols are a mixture of mono-, di- and tri-tert-butylethers of glycerin. The mixture of tert-butyl ethers (or glycerin tert-butyl ether) is a mixture of 1-tert-butylether, 1,3- and 1,2-di-tert-butyl ethers and 1,2,3-tritert-butyl ether of glycerin. The catalyst is organic or inorganic acids, solid or liquid, or a super acid including sulfuric acid, methanesulfonic acid or toluenesulfonic acid. The super acid catalyst is trifluoromethanesulfonic acid. The acid catalyst is a polymer with acid groups, a resin with acid groups, or a polymeric material with super acid groups. EXAMPLE - Methyl-tert-butyl-ether (40 g) and methanesulfonic acid (0.5 g), as catalyst, were added to olive oil (29 g, 0.032 moles of triglycerides). The reaction was carried out at 140 degrees C for 2 hours (pressure 20 bar) and, after cooling, the reaction was carried out for 6 hours at 70 degrees C (pressure 8 bar). After evaporating the excess methyl-tert-butyl-ether, the non-reacted isobutene and methanol under reduced pressure provided a final composition comprising (in wt./wt.%) fatty acid methyl esters (92.5), 1-tert-butyl ether of glycerin (3.2), 1,3- and 1,2-ditert-butyl ether of glycerin (3.7), 1,2,3-tritert-butyl ether of glycerin (0.1), glycerin (0.05) and mixed ethers (0.3).