The main objective of the present proposal is the development of a complete continuous reaction/separation process for the production of biodiesel from waste cooking oil (mainly from sunflower oil origin, which accounts for most of the edible oils consumed in Portugal) in supercritical carbon dioxide (scCO2). The production of biodiesel will be done via an enzymatic reaction which is more selective, avoids the need to neutralize the reaction mixture, and is more amenable to recycling than chemical catalysis. ScCO2 will act both as reaction medium and as the solvent for the separation and purification of biodiesel. The whole process will be carried out in a continuous mode, unlike more common processes where reaction and the various separation steps that follow are not integrated. CO2 is non-toxic, non-flammable, abundantly available, and its use is allowed in the food industry. By using only scCO2 as solvent, a cleaner, greener process is obtained. Cleaner chemical processes are both a great challenge and a great priority for European chemists and chemical engineers in the 21st century. By using waste cooking oil as starting material instead of the most commonly used virgin cooking oil, the serious environmental and economic problem of the increasing price of crops will be minimized. Through the integration of a diversity of scientific topics such as biocatalysis, supercritical fluids, high pressure phase equilibrium, continuous reaction/separation processes with compressed fluids, and computational process simulations, the present proposal can offer solutions to the problems that are found in most processes for biodiesel production, such as the low reaction yields and the difficult separation/purification of FAMEs, and can lead to an industrially viable process for the production of biodiesel that is also environmentally attractive.