A new framework for assessing the environmental impacts of circular economy friendly soil waste-based geopolymer cements

Portland cement is one of the principal constituents used as a building material and is responsible for high energy consumption and greenhouse gas (GHG) emissions. Any attempt to reduce cement usage would make savings in energy usage and GHG emissions. A case study of Portland cement (CEM-I) replacement using alkali activated soil filter cake as a geopolymer mortar is presented to demonstrate application of a three-stage GHG emission estimation and comparison methodology using a process-based life cycle assessment (LCA) study, with a focus on benchmarking environmental sustainability. Results indicate that the alkali activated soil filter cake reduced total GHG emissions by 31% compared with CEM-I, which equates to 110 kgCO2-eq/m3. Transportation by rail was found to be more sustainable compared with by road, with an overall higher GHG emission reduction of between 5 and 10%. For road transport, heavy goods vehicles (HGV) of between 3.5t and 5.7t recorded the highest GHG emissions whilst articulated lorries recorded the lowest GHG emissions. Furthermore, the results also demonstrated that a bulk carrier is the most environmentally sustainable option for overseas raw material transportation. Monte-Carlo simulations signified the likelihood of achieving lowered GHG emissions when considering commercial production and inventory changes across different countries varies from 18% to 71%. These results highlight the importance of critical analysis of several factors which contribute towards overall environmental sustainability, prior to decision making on sustainable materials. Further research is encouraged on developing processes and methodologies to prioritize selection of sustainable materials to optimize sustainable benefits.