Applications of sewage sludge in construction materials: a systematic review

Population growth has increased waste generation, including sewage sludge. This rise has spurred technology to revalue sludge as a resource. These efforts address environmental concerns and promote resourcefulness, especially for construction materials. However, the global use of sewage sludge in construction, the treatment methods, and its role in building materials remain poorly documented. To address this, a systematic review of 301 articles from 1994 to 2024 was conducted. The review evaluated application, treatment methods, role in mixes, sludge source, and material functionality. The analysis revealed that the majority of the articles focused on unspecified cement-based materials (32%), concrete (18%), mortar (10%) and ceramics (8%). Sewage sludge was primarily used as a binder (58%), an aggregate (20%), an admixture (12%), and a filler (8%). Thermal treatment was the most common treatment method (87%), followed by chemical treatment (9%), whereas biological treatments were infrequently utilised (2% each). Most of the sludge originated from municipal wastewater systems (76%) and industrial sewage (23%). Most studies (70%) concentrated on materials intended for structural purposes, whereas smaller segments examined applications in landfill/road construction (6%), thermal insulation (6%), infill/partition walls (2%), and decorative uses (1%). These findings underscore the potential of sewage sludge for developing innovative building materials, reflecting the growing global interest in its use. However, further research is required in underrepresented regions and regarding alternative sludge sources from septic tanks and industrial sludge.