Sludge valorization towards sustainable concrete: a biochar-based framework integrating life cycle assessment, and socio-economic impacts
Khadiga M. Mekky, Mahmoud Nasr, Kamal Sharobim, Manabu Fujii, Mona G. Ibrahim
Abstract
Abstract While recent studies have demonstrated that biochar supplementation to the cement mixture positively impacted the concrete mechanical properties, there is a research gap in exploring various environmental burdens, human health impacts, and resource consumption patterns accompanying biochar-concrete composite manufacturing. Hence, this study introduces a novel evaluation framework by integrating biochar-concrete properties, life cycle assessment (LCA) criteria, and economic considerations with sustainable development goals (SDGs) achievement. The control mix (C mix) was prepared using 100% cement, and the other mixtures were arranged using different sludge biochar (SB) replacement levels (5–20% w/w). A LCA model was employed to select the best sludge valorization approach, regarding two scenarios: (i) cement mixture (C mix) with sludge landfilling, and (ii) sludge biochar mixture (SB mix). The 5% SB mixture exhibited functional characteristics nearly comparable to those of the C mix, particularly in terms of compressive strength at 7 and 28 days, split tensile strength (3.5 MPa at 28 days), water penetration depth (≈ 2.8 mm), and durability. Applying this mixture in concrete maintained LCA endpoint categories of 0.005 DALY, 3.7 × 10 3 PDF m 2 yr, 7 × 10 3 kg CO 2 eq, and 70.6 × 10 3 MJ primary for human health, ecosystem quality, climate change, and resources, respectively. This mixture scenario could also fulfill 11 SDGs, including human health protection (SDG_3), resource recovery (SDG_12), climate change mitigation (SDG_13), and ecosystem preservation (SDG_14). Because the combined technical/LCA/SDG framework could maintain a sludge management approach for biochar-concrete industrialization, future work should focus on quantifying other scenarios related to energy, climate, urbanization, transport, and low-carbon cement development. Graphical abstract Graphical abstract shows a novel evaluation framework by integrating biochar-concrete properties, life cycle assessment (LCA) criteria, and economic considerations with sustainable development goals (SDGs) achievement. The control mix (C mix) was prepared using 100% cement, and the other mixtures were arranged using different sludge biochar (SB) replacement levels (5–20% w/w).