The construction industry is a major contributor to global CO2 emissions, primarily due to the energy-intensiveproduction of Ordinary Portland Cement (OPC). This paper presents a comparative case study comparing the environmental,mechanical, and durability performance of OPC (Conventional) and Fly Ash-Based Geopolymer Binders (Sustainable). Using data extracted from past research, this study demonstrates the significant sustainable effect of fly ash-based geopolymer binders. These green binders offer a considerably reduced embodied carbon and energy footprint, while maintaining comparable or superior performance indicators. Fly ash-based geopolymer binders exhibit an embodied carbon of 242.87 kg CO2e compared to 552.22 kg CO2e for OPC per kg binder or m3 concrete. Furthermore, their end-of-life assessment reveals greater potential for recycling and reuse, aligning with circular economic principles. The findings strongly advocate for the increased adoption of green cement, such as fly ash-based geopolymer binders, as a key strategy for developing energy-efficient and sustainable constructions.