Abstract: A method for easily decomposing viscous, solidified spilled fuel oil or crude oil containing sea water and other disposal inhibiting substances. Titanium dioxide particles are added to viscous spilled fuel oil recovered in drums in a weight ratio of at least 0.2 to 1 times. Fuel oil is specifically adsorbed by the adsorbent and the mixture can be suspended in water. The suspension is filtered by a coarse filter to remove substances interfering with disposal by the oil. This filtrate is passed through a high performance filter (of sufficiently fine mesh to retain the adsorbent) so that the adsorbent is recovered, and sea water and other substances are discarded.