Due to environmental protection, the recycling of fractions < 10 mm from waste incineration bottom ashes is inevitable in the future and at the same time a source for metal resources, which may help Germany to get more independent in metal feedstock supply. Caused by the inhomogeneity of bottom ashes, random sampling does not provide reliable concentration average values. Therefore, only a long-time study based on dissolution provides appropriate data about the potential of bottom ashes. Thus, not the concentration of the solid material is used for evaluation of the potential, but the amount of metals (Al, Fe, Cu, Zn), which are dissolved upon bioleaching from the bottom ashes.