In the present paper, magnetic nanoparticles (Fe3O4 NPs) covered with tartaric acid (TA) have been synthesized through an "eco-friendly approach" and subsequently used for direct physical immobilization of the lipase from Thermomyces lanuginous (TLL). The immobilized lipase was used for the biodiesel production from dairy waste scum oil in a solvent-free system. The maximum yield to biodiesel of the immobilized lipase is about 90%, at the alcohol/oil molar ratio of 6:1, in the same operating conditions free lipase exhibits, after 24 h, a maximum yield of 76% with a molar ratio of 3:1. The immobilized lipase showed excellent reusability. The biodiesel properties evidence the feasibility of the dairy waste scum oil as raw material for biodiesel production.