Cradle-to-grave life cycle assessment of wood ash–NaCl stabilized soils: service-life-adjusted environmental, economic, and circular economy performance

Decarbonizing soil stabilization is essential for sustainable infrastructure, particularly in developing regions where conventional lime and cement binders impose high environmental and economic burdens. This study presents an ISO 14040/14044–compliant cradle-to-grave life cycle assessment of soils stabilized with a wood ash–sodium chloride (WA–NaCl) system, benchmarked against lime and cement. A service-life–adjusted functional unit (1 tonne of stabilized soil delivering equivalent bearing performance over 15 years) integrates mechanical durability into the environmental assessment. Regionalized modeling incorporates Nigerian-specific energy mixes, transport logistics, and material sourcing. WA–NaCl stabilization achieves an 85–90% reduction in embodied greenhouse gas emissions (5–15 kg CO₂-eq per tonne) relative to lime (80–100 kg) and cement (70–90 kg), driven by waste valorization, low-energy processing, and avoided landfill impacts. Material circularity exceeds 95%, and monetized externalities—including a social cost of carbon of ~ 190 USD per tonne CO₂-eq—reduce total societal costs to 28–51 USD per tonne, compared with 62–94 USD for lime-based stabilization. Sensitivity and uncertainty analyses confirm the robustness of these advantages across variations in transport distance, energy intensity, and carbon pricing. Enhanced mechanical durability, underpinned by pozzolanic and chloride activation mechanisms, further amplifies long-term sustainability. The findings demonstrate that WA–NaCl stabilization constitutes a net-positive, circular alternative for road subgrades and geotechnical applications, offering substantial climate mitigation, cost savings, and resource efficiency. This study supports the integration of waste-derived binders into low-carbon infrastructure policies and performance-based procurement frameworks.