The adoption of the Urban Waste Water Treatment Directive requires sewage sludge to be subsequently treated and the Sewage Sludge Directive regulates the uses and properties of stabilised sludge for being either recycled or disposed. Both directives drive specific actions in two complementary ways. Reduction, Modification and Valorisation of Sludge aims at developing strategies for the disposal and reuse of waste sludge. It aims to develop several processes for reducing both amount and toxicity of sludge, with simultaneous transformation into green energy vectors such as methane or hydrogen. Mesophilic and mainly thermophilic and autothermophilic conditions are explored as classical alternatives for sludge stabilisation, assuring sanitary conditions of the treated sludge. Valuable materials are obtained from sludge, such as activated carbons, which are used in conventional adsorption processes and in innovative advanced oxidation processes. Guidelines are provided for technology selection in agreement with the geographic, economic and technical characteristics of the sewage plants, demonstration of the feasibility of new applications for the sewage sludge, manufacturing of activated carbon from sludge sewage as innovative recycling of sludge waste, and a deep understanding of the methods involved.