recirculated via the gas recirculator 3 and the outlet 5 entrained water or methanol removed from the volume is condensed by passing the vapour laden air stream through a heat exchanger 8 to condense the vapour to be collected in a graduated tank 9 the collected methanol is recovered from the graduated tank 9 via an outlet valve 10 the apparatus therefore provides a closed system for the batch preparation of biodiesel from a source of oil or fat the apparatus is fitted with additional inlet and outlet valves 11 12 and 13 to permit introduction and recovery of the agents and products for each step of the general method all steps in the general method may be performed using the apparatus with consequential reduction in costs for establishing production facilities a weighed volume 15580 kg of tallow containing approximately 0 1 w w water was delivered to the reactor tank 4 and heated by means of the heating coils 6 to a temperature of 60 u00b0 c the volume of tallow was maintained at this temperature with operation of the gas recirculator 3 for 21 hours a volume of 8 liters of water collected in the graduated tank 9 the dehydrated tallow was determined to contain approximately 0 04 w w water a volume of dehydrated and transesterified tallow containing approximately 3 w w of methanol was aerated for 40 hours by operation of the gas recirculator 3 at a temperature of 60 u00b0 c a volume 450 liters of methanol was collected in the graduated tank 9 the methanol content was determined to be reduced to 0 2 w w it will be.