Waste bleaching earths from crude vegetable oil refining process contain approximately 40% of its weight as oil. Low valued oils are potential substrates for biodiesel fuel production. Vegetable oils from waste bleaching earth samples were organic-solvent extracted and identified as soybean, palm and rapeseed oil. Methanolysis was efficiently catalyzed by Rhizopus oryzae lipase in the presence of high water content, and by a single addition of methanol. R. oryzae lipase was not inactivated by methanol in concentrations lower than 4 milli-equivalents and 75% water content. Optimum conditions for methanolysis of extracted oils were 75% water content (by weight of substrate), an oil/methanol molar ratio of 1:4, and 67 IU/g of substrate with shaking of 175 rpm for 96 h at 35 degreesC. The highest conversion yield reached 55% (w/w) with palm oil after 96 h of reaction. Adverse viscosity conditions might have influenced methanolysis of extracted soybean and rapeseed oil in spite of high water or methanol concentrations. (C) 2002 Elsevier Science Ltd. All rights reserved.