Methods and devices are disclosed for converting predominantly organic waste materials, such as sludge, into useful byproducts. The computer 10 makes a request to the identified target device TD for attachment of the logical device LDEV that stores the snapshot files for which access is requested. The centre point between the locking rings forms the centre for the movements of the spindle. The predetermined frequency is substantially consistently lower than \xbd of a reference frequency of a recording clock for creating the pits or the recording marks and is higher than a response frequency of a PLL for generating a reproduction clock for reproducing the main information.