Catalyst and method for biodiesel production from unrefined low-grade oil and crude aqueous alcohols

A catalyst for catalyzing transesterification of esters or esterification of fatty acids, the catalyst is selected from the group consisting of manganese (II) glycerolate, cobalt (II) glycerolate, iron (II) glycerolate, and any combination thereof. A method for transesterification reaction, includes: a) providing a catalyst, wherein the catalyst is selected from the group consisting of manganese (II) glycerolate, cobalt (II) glycerolate, iron (II) glycerolate, and any combination thereof; b) adding the catalyst, one or more alcohols, and a composition comprising one or more esters to a reactor to form a reaction mixture; and c) stirring while heating the reaction mixture for reaction to form transesterification products.