To avoid competition with food production, residual materials such as straw have come to the attention of several biofuel manufacturers. Straw is largely composed of lignocellulose fibres, which have a high potential for energy conversion. A process in which waste biomass, such as wheat straw, is used as a raw material to produce microbial oils for advanced biofuels has been developed. Through a fermentation process with special oleaginous yeasts, straw is being converted into these microbial oils, with a defined chemical composition. The process consists of two steps: an initial saccharification, which transforms the cellulosic component of the raw materials into simple sugars (glucose), and a subsequent fermentation in which yeasts metabolise the sugars and accumulate up to 70% of microbial oils into their cells. Such oils are then extracted and sent to biorefineries for the production of advanced biofuels, such as Eni’s Greendiesel.