The conversion of lauric acid and fatty acid mixtures to methyl esters was investigated using bismuth-containing solid catalysts obtained from Bi2O3. When the reaction was carried out at 140 degrees C for 2 h using a methanol:fatty acid molar ratio of 2:1 and 5 wt % of Bi2O3 in relation to the mass of fatty acids, conversions up to 87 wt % were achieved even after four consecutive reaction cycles. Besides the observed catalytic activity, the bismuth-containing solid catalyst was also amenable to recycling for at least four reaction cycles without significant loss of its catalytic performance. However, the analysis of the recovered solids by X-ray diffraction and Fourier transform infrared spectroscopy demonstrated that Bi2O3 was converted to layered bismuth carboxylates, which acted as the actual esterification catalyst. On the basis of these, layered bismuth carboxylates unfold as a suitable catalytic system for the esterification of fatty acids and lipid sources of high acid number.