Three principal variables, molar ratio of methanol to oil, amount of catalyst, and reaction temperature, affecting the yield of acid-catalyzed production of methyl ester (biodiesel) from crude palm oil were investigated. The biodiesel was then used as an extractant in batch and continuous acetone-butanol-ethanol fermentation, and its fuel properties and that of the biodiesel-ABE product mix extracted from the batch culture analyzed. The optimized variables, 40:1 methanol/oil (mol/mol) with 5% H2SO4 (vol/wt) reacted at 95 degreesC for 9 h, gave a maximum ester yield of 97%. Biodiesel preferentially extracted butanol, and enhanced its production in the batch culture from 10 to 12 g l(-1). The fuel properties of biodiesel and the biodiesel-ABE mix were comparable to that of No.2 diesel, but their cetane numbers and the boiling points of the 90% fractions were higher. Therefore, they could serve as efficient No. 2 diesel substitutes, The biodiesel-ABE mixture had the highest cetane number.