NOVELTY - Making bio-diesel fuel (36) involves feeding tertiary alkyl ether to decomposition reaction zone (18); contacting ether with catalyst; separating alcohol and iso-olefin; feeding alcohol, vegetable oil and animal fat to trans-esterification reaction zone (14); contacting alcohol, oil and fat to form trans-esterification product; separating product to recover alkyl esters and glycerol; feeding glycerol and iso-olefin to etherification reaction zone (32); contacting iso-olefin and glycerol to form etherification product; and separating product to recover di- and tri-tertiary alkyl glycerol.    USE - For production of a bio-diesel fuel (claimed), including fatty acid methyl ester (FAME) and tri-isobutyl glycerol (TIG) used in diesel engines.    ADVANTAGE - The method provides decomposition of ethers with production of bio-diesel fuels or fuel additives provides iso-olefins and alcohols at the necessary stoichiometric ratio, thus eliminates the need to import alcohols, glycerol, and iso-olefins; provides a viable alternative use for existing MTBE production units; provides MTBE is convenient and economical way to transport the isobutylene and methanol (in the correct ratio) from the oil refinery or other MTBE producing facility to the bio-diesel plant for use as feeds to the trans-esterification and etherification processes.    DETAILED DESCRIPTION - Production of a bio-diesel fuel (36), involves: feeding a tertiary alkyl ether to a decomposition reaction zone (18) containing at least one decomposition catalyst; contacting the tertiary alkyl ether with at least one decomposition catalyst at a temperature and a pressure to decompose the tertiary alkyl ether into an alcohol and an iso-olefin; separating the alcohol and iso-olefin to recover a fraction comprising the alcohol and a fraction comprising the iso-olefin; feeding at least a portion of the fraction comprising the alcohol and at least one of a vegetable oil and an animal fat to a trans-esterification reaction zone (14); contacting the alcohol and at least one of a vegetable oil and an animal fat in the presence of at least one trans-esterification catalyst under conditions of temperature and pressure sufficient to trans-esterify the vegetable oil or animal fat to form a trans-esterification product comprising fatty acid alkyl esters and glycerol; separating the trans-esterification product to recover a fraction comprising the fatty acid alkyl esters and a fraction comprising the glycerol; feeding at least a portion of the fraction comprising the glycerol and at least a portion of the fraction comprising the iso-olefin to an etherification reaction zone (32); contacting the iso-olefin and the glycerol in the presence of at least one etherification catalyst under conditions of temperature and pressure to form an etherification product comprising at least one of mono-tertiary alkyl glycerol, di-tertiary alkyl glycerol, and tri-tertiary alkyl glycerol; and separating the etherification product to recover a fraction comprising di-tertiary alkyl glycerol and tri-tertiary alkyl glycerol.    DESCRIPTION OF DRAWING(S) - The figure shows a simplified flow diagram of a process for producing bio-diesel.    Process (10)    Flow lines (12, 16, 20, 22, 24, 26, 28, 30, 34)    Trans-esterification reaction zone (14)    Decomposition reaction zone (18)    Etherification reaction zone (32)    Bio-diesel fuel/bio-diesel fuel additive stream (36)