The increasing demand for alternative energy feedstocks is pushing many stakeholders toward the development of new processes, technologies, regulations, as well as new production and economical models. Waste oils represent a consolidated source of valuable raw materials for many industries and, as in the case of used vegetable oils, fit well with the medium- and long-term sustainability objectives of industrialized countries. Waste oils are transversal to many value chains, such as food, the plastic industry, and fossil fuel extraction; thus, they could represent precious raw materials if properly exploited.

In this context, a state of the art is provided, which covers technical, regulatory, and research aspects of the topic.