This paper presents a topology optimization (TO) approach for multi-material active structures to reduce energy consumption and carbon footprint. The method is based on a density-based TO scheme, considering both passive and active materials in the optimization process. The objective is to minimize the environmental impact of the structure during its service life, which includes both the embodied environmental impact (material production) and the operational environmental impact (actuation energy). The approach is validated through numerical examples, showing that topology-optimized active structures can achieve significant weight savings, reduced energy consumption, and lower carbon emissions compared to equivalent passive structures. The study highlights the potential of active structures to be more environmentally friendly than traditional passive structures, as they can actively adjust their configuration and properties to reduce energy use and emissions. The proposed framework allows for the design of lightweight, efficient, and environmentally sustainable structures by optimizing the distribution of passive and active materials. The results demonstrate that the approach is effective in minimizing environmental impact while maintaining structural performance. The study also discusses the importance of considering both material properties and actuation effects in the optimization process to achieve optimal environmental outcomes.This paper presents a topology optimization (TO) approach for multi-material active structures to reduce energy consumption and carbon footprint. The method is based on a density-based TO scheme, considering both passive and active materials in the optimization process. The objective is to minimize the environmental impact of the structure during its service life, which includes both the embodied environmental impact (material production) and the operational environmental impact (actuation energy). The approach is validated through numerical examples, showing that topology-optimized active structures can achieve significant weight savings, reduced energy consumption, and lower carbon emissions compared to equivalent passive structures. The study highlights the potential of active structures to be more environmentally friendly than traditional passive structures, as they can actively adjust their configuration and properties to reduce energy use and emissions. The proposed framework allows for the design of lightweight, efficient, and environmentally sustainable structures by optimizing the distribution of passive and active materials. The results demonstrate that the approach is effective in minimizing environmental impact while maintaining structural performance. The study also discusses the importance of considering both material properties and actuation effects in the optimization process to achieve optimal environmental outcomes.