Systems and methods for performing anaerobic digestion of biomaterials using a clarifier, a batch reactor, andor a digester are disclosed. In the present invention, in order to accomplish the above-described object, there are provided a method and a device for determining the position for detection of charged particles by making the comparison between a stained optical microscope image and an elemental mapping image formed based on X-rays detected by irradiation with the charged-particle beam. Preferably, the memory is partitioned into the non-overlapping regions either by using address interleaving or by using address range registers to identify address ranges for said regions. Lastly, an MOS calculation is carried out in order to obtain a result comparable with human evaluation.