Thermal treatment of waste differs significantly from the combustion of regular fuels due to the fluctuating and unpredictable composition of the fuel. It is therefore necessary to develop processes with safe process engineering technology that guarantee the treatment of waste in accordance with ecological and economic constraints in addition to complying with international legal requirements. Various important factors have to be considered: not only the reduction of the volume and mass of waste and the destruction and separation of pollutants, but also the efficient energy production (electricity and district heating) and the guaranteed treatment of all waste. In order to comply with strict Japanese regulatory policies, particularly with regard to residue quality and overall output of organic substances, grate technology was modified by means of downstream melting processes that are intensive in terms of maintenance, energy and resulting costs. While vitrification of bottom ash and fly ash does improve quality and provide additional recycling possibilities, it has not proven sustainable. Conversion technologies using separated high-temperature processes make integrated production of granulated slag possible. Large market shares in Japan were gained as a result. However, practical experience in largescale plants has shown serious drawbacks with regard to availability, profitability and process safety. The use of alternative waste conversion technologies failed on the German market due to massive technical problems and considerable financial losses for all those involved.
