This paper presents a topology optimization (TO) approach for designing multi-material active structures to reduce energy consumption and carbon footprint. The study aims to develop a general TO framework that considers both passive and active materials to minimize the environmental impact of the structure during its service life. The environmental impact is defined as the energy consumption or greenhouse gas (GHG) emissions caused by the structure, which is treated as the objective function to be minimized under displacement constraints. The proposed method is based on a density-based TO scheme and uses a three-field approach to parameterize the material distribution and actuation effects. Numerical examples demonstrate that the topology-optimized active structures can achieve significant weight savings and reduce energy consumption and GHG emissions compared to equivalent topology-optimized passive structures. The results indicate that the developed approach has the potential to design novel structural systems with lighter weight, larger span, and reduced environmental impact.This paper presents a topology optimization (TO) approach for designing multi-material active structures to reduce energy consumption and carbon footprint. The study aims to develop a general TO framework that considers both passive and active materials to minimize the environmental impact of the structure during its service life. The environmental impact is defined as the energy consumption or greenhouse gas (GHG) emissions caused by the structure, which is treated as the objective function to be minimized under displacement constraints. The proposed method is based on a density-based TO scheme and uses a three-field approach to parameterize the material distribution and actuation effects. Numerical examples demonstrate that the topology-optimized active structures can achieve significant weight savings and reduce energy consumption and GHG emissions compared to equivalent topology-optimized passive structures. The results indicate that the developed approach has the potential to design novel structural systems with lighter weight, larger span, and reduced environmental impact.