From Laboratory to Industry: Feasibility Assessment of Industrial Production of Waste- Based Geopolymers

Abstract

The construction industry is one of the largest contributors to environmental degradation, accounting for 40% of global carbon emissions (Onat and Kucukvar, 2020). The production of materials like steel and Ordinary Portland Cement (OPC), the primary binder in concrete, is a significant source of these emissions (United Nations Environment Programme, 2020; International Energy Agency, 2021). OPC manufacturing is particularly problematic due to its high energy demand and CO₂ emissions, with around one ton of CO₂ emitted per ton of cement produced (Scrivener et al., 2018). Additionally, the industry depletes natural resources, contributes to deforestation, and generates pollutants like sulfur dioxide (SO₂) and nitrogen oxides (NO₂), exacerbating environmental and health issues (Schuhmacher et al., 2004; Wang et al., 2020; Elahi et al., 2020). Efforts to reduce these impacts include the use of supplementary cementitious materials (SCMs), carbon capture, utilization, and storage (CCUS) technologies, and alternative binders like geopolymers. Geopolymers, composed of aluminosilicates, offer substantial environmental benefits, including reduced CO₂ emissions and lower energy demands, compared to OPC (Davidovits, 2015; Kumar and Kumar, 2014). Furthermore, their ability to incorporate industrial byproducts like fly ash and slag supports a circular economy by reducing landfill waste and raw material consumption (Provis & Bernal, 2014; Amar et al., 2024). Despite their potential, geopolymers are primarily studied in laboratory settings, and their large-scale production remains underexplored. Laboratory results demonstrate their low carbon footprint, strong mechanical properties, and chemical resistance (Singh and Middendorf, 2020; Irum and Shabbir, 2024). However, scaling up geopolymer production introduces complexities such as material and energy flow management and economic constraints which are absent in controlled laboratory environments (Islam and Alengaram, 2021). Existing Life Cycle Assessments (LCAs) often oversimplify these challenges, limiting their applicability to industrial scenarios (Turner and Collins, 2013; Shi et al., 2021). This thesis aims to bridge this gap by developing a comprehensive framework to evaluate the environmental, economic, and technical feasibility of large-scale geopolymer production. Specifically, the study investigates the role of geopolymer materials in reducing CO₂ emissions, promoting a circular economy through the reuse of different industrial wastes (such as paper mill waste, spent coffee ground and red mud), and addressing the challenges of scaling up from laboratory to industrial production (Segura et al., 2023). The research is structured around the following three research questions: • RQ1: Which industrial waste is the most promising for industrial scale-up of geopolymer production? • RQ2: What are the environmental and economic performances of waste-based geopolymer production at industrial and supply chain levels? • RQ3: What are the necessary procedural steps for developing a structured framework to assess the large-scale production feasibility of waste-based geopolymers? By answering each research question, the following outcomes were achieved: RQ1: The analysis of various industrial wastes identified Red Mud (RM) as the most promising material for large-scale geopolymer production. Laboratory studies evaluated formulations based on RM, Spent Coffee Grounds (SCGs), and Paper Mill Waste (PMW). RM outperformed others due to its high mechanical strength, low water absorption, and good thermal insulation properties. Using a multi-criteria decision-making approach (VIKOR), the formulation with 10% RM was selected as the optimal choice, offering the best balance of mechanical performance, physical stability, and environmental sustainability. RQ2: Economic and environmental analyses revealed that RM-based geopolymers could reduce CO₂ emissions by up to 62% compared to OPC. A cradle-to-gate Life Cycle Assessment (LCA) highlighted the following advantages: • SCG-based geopolymers: 43.3% reduction in carbon footprint, with high organic integration and minimal use of alkaline activators. • PMW-based geopolymers: Greater conservation of natural resources, low water absorption, and high durability. • RM-based geopolymers: Maximum reduction in Global Warming Potential, leveraging RM’s availability and composition. Economically, using industrial byproducts reduced waste management costs and improved supply chain efficiency. RQ3: The developed structured approach systematically guides users from initial material selection through to industrial production and supply chain optimization. By integrating each critical stage – including MCDM-based selection, standardized scale-up procedures, and environmental and economic assessments – this framework provides a robust model for industries looking to adopt waste-based geopolymers on an industrial scale. This framework thus offers an invaluable tool for practitioners and researchers alike, advancing the field of sustainable construction materials by enabling informed, scalable production of waste-based geopolymers.