NOVELTY - Esterification of free fatty acids (3) contained in raw materials (1), comprises: (a) separating the free fatty acids from residual raw materials; (b) optionally reacting the residual raw materials in the form of a transesterification obtained fatty acid alkyl ester; (c) reacting the fatty acids with an alcohol; (d) optionally separating water and optionally together with at least a part of the alcohol; (e) optionally further reacting the dewatered product, optionally under addition of further alcohol; and (f) mixing the reaction product with the residual raw material and/or fatty acid alkyl ester.    USE - The process is useful for the production of biodiesel (claimed).    ADVANTAGE - The process is carried out in an inexpensive manner and esterifies the free fatty acids with high space-time yield.    DETAILED DESCRIPTION - Continuous process for esterification of free fatty acids (3) contained in raw materials (1), comprises: (a) separating the free fatty acids from residual raw materials by deacidification process; (b) optionally reacting the deacidified, residual raw materials in the form of a transesterification obtained fatty acid alkyl ester; (c) reacting the free fatty acids with an alcohol under use of at least an acid catalyst in a fixed bed, in the form of an esterification reaction; (d) optionally separating water, which is formed as byproduct in step (c) and optionally together with at least a part of the alcohol, which is not reacted in step (c); (e) optionally further reacting the dewatered product obtained from step (d), optionally under addition of further alcohol and use of at least an acid catalyst in a fixed bed, in the form of an esterification reaction; and (f) mixing the reaction product obtained from step (c) and/or the reaction product obtained optionally from step (e) with the residual raw material obtained from step (a) and/or the fatty acid alkyl ester obtained from step (b).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the process for esterification of free fatty acids contained in raw materials.    Raw material (1)    Free fatty acid (3)    Alcohol stream (4)    Product stream (5)    Apparatus. (10)