Consequential Life Cycle Assessment of Nature-based Solutions for Land Restoration in Turin (italy) and First-Belt Municipalities

Urban and peri-urban soils are increasingly degraded by land consumption and surface sealing, with adverse consequences for ecosystem functioning, climate regulation, and human health. Nature-based Solutions (NbS) combining reconstructed soils with urban tree and shrub planting have emerged as promising strategies for land restoration, yet their system-wide environmental and health implications at metropolitan scale remains poorly understood. This study develops an ex-ante, time-dependent Consequential Life Cycle Assessment (CLCA) to evaluate a large scale technosol-based NbS programme in Turin (Italy) and its first-belt municipalities, covering ~200ha of degraded land. The intervention was modelled through a 15-year phased roll-out followed by a 60-year operational lifetime, explicitly accounting for marginal material supply activation, capacity-constrained supplier switching, transport dynamics, and end-of-life activities. Environmental impacts on human health were balanced against the benefits associated with carbon sequestration and air pollution removal. Results show that NbS implementation entails substantial environmental burdens during the deployment phase, primarily driven by technosol production and material handling. These impacts peak within the first 15 years, after which a growing supply of ecosystem services generate net annual climate and air quality benefits. Carbon break-even is reached after approximately 45 years, while air pollution-related impacts become net negative after about 61 years. This study demonstrates the long-term benefits for human health and the material-related tradeoffs associated with large scale technosol-based NbS, advancing the methodological foundation for policy-relevant urban land restoration assessment.