complete assessment management methods of fly ash and selects as method the chemical stabilization using phosphate ions.
The costs of the various filter ash treatment options have been estimated on the basis of published data and are given in Table 4. The costs of technical processes should be comparable in most industrialised counties whereas the disposal fees will change from country to country. Table 4 reveals that the specific costs of the technical measures are rather high, especially for thermal processes, but due to the small residue streams the expenses per ton of waste are low and similar for all disposal strategies. Hence the economy will not be the decisive factor for the selection of a specific process and local conditions like access to adequate disposal sites will be more important. In Germany the underground 'utilisation' looks economically promising as the gate fee has dropped down to approx. 40 - 70 € per ton of material. As a consequence, dry scrubbing processes may be promoted which is in contradiction to the legislative demand for residue minimization. If the strategy gains wide application, however, it will change the management of residues from APC systems in future at least in Germany, where a great number of old mines is waiting to be filled (Vehlow, 2002).