A thin film vortex fluid device (VFD) is effective in the room temperature continuous flow conversion of sunflower oil to biodiesel. Optimised VFD operating parameters affords high purity biodiesel, with no saponification, without the need for the otherwise conventional use of a co-solvent or the use of complex catalysts, with improved green chemistry metrics for biodiesel production. The biodiesel, glycerol byproduct and catalyst also spontaneously separate post-VFD processing, and the catalyst can then be readily recycled three times without the need for further complex down-streaming processing.