Toxic wastes and other contaminants are removed from soil which is fed through a passage in an agitating means into a retort (10, 110) where the soil is agitated and brought into contact with the retort walls (11, 111, 111A) (at a temperature preferably above 500.degree. C.) to cause the toxic wastes or contaminates to be desorbed. The "off-gases" from the soil may be mixed with air/fuel in a combustion chamber (31, 131), to heat the retort; may be burnt in a secondary burner (40) to preheat and/or dry the soil feed; or be condensed in a condenser (41) and stored.