A process for utilizing bio-based oils and/or fats for producing biofuels includes the steps of: mixing alcohol with a raw material for forming a reaction mixture; pumping the reaction mixture to a reactor; mixing biogas as a catalyst with the reaction mixture in a selected process step either before or after the supply of the reaction mixture to a high-pressure pump, the biogas including methane and carbon dioxide; adjusting a temperature and pressure of the reactor so that the reaction mixture achieves a supercritical state; esterifying the reaction mixture to produce liquid biofuel and by-products; separating the by-products including methane and alcohol from the liquid biofuel; and recovering separated methane. An equivalent system for utilizing bio-based oils and/or fats for producing biofuels is also disclosed.