The reuse of industrial by-products as geomaterials offers a sustainable solution for waste management and environmental protection. This study examines the chemical characterization of water treatment sludge (WTS), vegetal biomass ash (VBA), granitic mining waste (GMW), and blast furnace slag (BFS) as components in engineered liner systems for waste containment. Recycling these materials supports the circular economy and the United Nations’ Sustainable Development Goals. Chemical analysis revealed pH variations from 5.55 (WTS) to 11.1 (BFS), influencing their interactions in liners. GMW, primarily quartz and alumina, closely resembles local bedrock and poses minimal contamination risk. BFS, rich in iron and calcium oxides, shows potential cementitious properties but requires assessment for expansive behavior. VBA, transformed through incineration, exhibits pozzolanic potential due to high Si, Al, and Fe content. WTS, mainly amorphous, reduces mixture density but requires further pozzolanic activity analysis. The findings confirm the environmental viability of these by-products, with effective chemical compatibility. Optimized mixtures with soil maintain low contamination potential while preserving essential hydraulic and mechanical properties. WTS can immobilize contaminants, VBA and GMW exhibit minimal heavy metal content due to their stable composition, and BFS contributes to soil reinforcement. This research highlights the dual benefits of reducing industrial waste disposal and developing sustainable geomaterials for geotechnical applications, demonstrating their potential for improving liner performance while promoting environmental sustainability.