Embodiments herein relate to the production of alkyl esters from lipid feed stocks. In an embodiment, a process for producing alkyl esters is included. The process can include mixing a lipid feed stock with an alcohol, water, and at least one of carbon dioxide, carbon monoxide, and/or one or more acids to form a reaction mixture, and contacting the reaction mixture with a catalyst under supercritical conditions for the alcohol, the catalyst comprising a metal oxide. Other embodiments are also included herein.