Abstract: A method is presented for producing biodiesel from a triglyceride feedstock. The feedstock is pretreated by thermal cracking or rapid pyrolysis to form a middle distillate fraction rich in fatty acids. The middle distillate fraction is then treated by vapour phase esterification under vacuum and in the presence of an alcohol and a solid acid catalyst to produce a biodiesel stream. The biodiesel stream can be treated with a basic solution to convert residual free fatty acids to non-foaming metallic soaps, which are separated by known means. A method is also provided for producing a biodiesel/naphtha mixture, in which a triglyceride feedstock is pretreated by thermal cracking or rapid pyrolysis to produce a middle distillate fraction, a naphtha stream and a gas stream. The naphtha stream and the middle distillate fraction are then treated by vapour phase esterification under vacuum and in the presence of an alcohol and a solid acid catalyst to produce a mixed biodiesel/naphtha stream.