Fatty acid esterification pretreatment process

A process for reduction of free fatty acid concentrations in a fatty acid feedstock by enzymatic esterification with alcohol thereby reducing free fatty acid concentrations to levels compatible with a base-catalyzed biodiesel production process, or as a crude oil product suitable as fuel for ships, or as a feedstock oil for hydrotreated vegetable oil (HVO) production comprising steps of:

• (a) providing fatty acid feedstock comprising more than 1 wt % Free Fatty Acids (FFA);
• (b) contacting said fatty acid feedstock with a composition comprising an esterase and at least one component selected from the group consisting of alcohol, alcohol and glycerol, alcohol and water, alcohol and water and glycerol to form a mixture;
• and
• (c) incubating the mixture of step (b) under conditions allowing the esterase to catalyze esterification of FFA until FFA levels are reduced either:
• i) below 10 wt % if a neutralization step follows the enzymatic esterification reaction;
• ii) below 2 wt % if a base-catalyzed transesterification follows the enzymatic esterification reaction without further FFA reduction;
• or
• iii) below 10 wt %, below 5 wt %, such as below 2 wt % if neither neutralization nor base catalyzed transesterification follows the esterification step c).