The technical literature on the production of used cooking oils (UCOs)-based biodiesel is already very extensive and widely covered. Consequently, UCOs turn into problematic waste that requires proper disposal. In order to estimate the world production of UCOs and their potential as oleochemical feedstock, it is necessary to understand the vegetable oils market. Generally, in all current industrial processes, there are major challenges that jeopardize biodiesel production from UCOs, even under subsidized schemes. Hydrotreated vegetable oil and some other non-ester biofuels are more diesel-like biofuels, so they are more stable and more compatible with current fuel infrastructure, and they can even improve diesel properties. While most current applications are energy-related and they will certainly represent the major end use of collected UCOs in the next years, it is expected that the waste oils will increasingly be incorporated as feedstock in the oleochemical industry in the future.