Innovative valorization of biomass waste-derived sodium silicate for geopolymer concrete synthesis: Sustainability assessment and circular economy potential

Abstract

Exorbitant greenhouse gas emissions associated with commercial sodium silicates (SS) have curtailed the large-scale practical implementation of geopolymers and have also led to discrepancies related to their sustainability. As a result, the extraction of SS from silica-rich biomass/agricultural waste ashes (AGWA) have gained the attention of researchers. This process involves heat treatment of AGWA with sodium hydroxide in addition to the calcination to produce the ash itself, thus requiring a systematic study to justify its sustainability. Therefore, this study presents an integrated techno-economic analysis (TEA) and life cycle assessment (LCA) to determine the economic and environmental feasibility of AGWA-derived activators for geopolymer concrete synthesis. The LCA results showed a 60–62% reduction in the greenhouse gas emissions of commercial SS-based geopolymer. A significant improvement was also observed in photochemical ozone formation, wherein the emissions were lesser from binders using AGWA based SS as compared to binders produced with commercially available SS. The TEA indicated that although the AGWA-derived SS reduced the cost of the activator by 50–70%, the overall cost of geopolymer concrete with these activators was still higher than OPC based concrete. The hydrothermal process was found to have a lower CO2 emissions and production cost as compared to the thermochemical method to prepare AGWA-derived SS. All in all, the innovative valorization of biomass-waste-derived sodium silicate in geopolymer concrete has a lot of potential to foster a circular bioeconomy by closing the loop of agricultural waste and also promote circular construction by repurposing of waste materials in concrete.