This perspective article aims to identify key research priorities to make the waste-to-energy sector compatible with the societal goals of circularity and carbon neutrality. These priorities range from fundamental research to process engineering innovations and socio-economic challenges. Three focus areas are highlighted: (i) the optimization of flue gas cleaning processes to minimize gaseous emissions and cross-media, (ii) the expansion of process control intelligence to meet targets for both material recovery and energy recovery, and (iii) climate neutrality, with the potential for negative emissions via the removal of atmospheric carbon dioxide across the full cycle of the waste resource. For each area, recent research trends and key aspects that are yet to be addressed are discussed.