The extensive use of Ordinary Portland cement (OPC) in foamed lightweight concrete (FLC) contributes significantly to its carbon footprint. Concurrently, the disposal of industrial by-products carbide residue slag (CRS) and ground granulated blast furnace slag (GGBS) poses challenges. This study developed a sustainable foamed lightweight concrete system employing CRS-activated GGBS as a complete OPC substitute to address both engineering performance and environmental concerns. An optimal CRS/GGBS ratio (10/90) was determined for achieving the maximum compressive strength in the binder system. Compared to OPC, the CRS/GGBS binder exhibits remarkably low heat of hydration, enabling safer large-volume placements and effectively mitigating the risk of early-age thermal cracking. The prepared CRS/GGBS foamed concrete has much higher compressive strength than those made with cement due to refined air void structure with increased sphericity and improved flexural strength of the solid matrix. The life cycle assessment demonstrated that CRS/GGBS foamed concrete has the ability to decrease carbon emissions by as much as 80 % when compared to cement foamed concrete. This work establishes CRS/GGBS as a technically viable and environmentally superior binder for foamed lightweight concrete, offering enhanced compressive strength, lower thermal cracking risk, and a reduced carbon footprint compared to conventional cement systems in civil engineering.