Quantifying the environmental impact of structural timber across multiple future lifecycles

Abstract: The pressing challenge of reducing human-induced environmental and climate impacts requires a massive transformation in the construction sector, a major contributor to energy consumption and CO 2 emissions. The potential for implementing circular strategies in construction is increasingly supported by current standards and reports. Emerging technologies, like cross-laminated reclaimed timber, render cascading options potentially comparable to direct reuse. Simultaneously, wood possesses a high heating value, meaning that incineration remains a competitive alternative to recycling seen from a contemporary market perspective. This study seeks to identify the most environmentally beneficial end-of-life strategy for structural timber elements under diverse future scenarios, taking into account systemic changes occurring over time. It introduces novelty by combining elements that are relevant to this context: (1) the circular economy of timber; (2) structural calculations accounting for material quality and losses; (3) dynamic prospective life-cycle assessments (LCAs); and (4) matching different circular-economy strategies with compatible future scenarios suggested by the Shared Socioeconomic Pathways (SSPs) mentioned in the IPCC’s sixth assessment report. The results indicate that the reuse of timber is beneficial only when there is no need for additional steel brackets, underscoring the importance of a meticulous definition of the unit with all adjoining structures to ensure accurate and appropriate results. Furthermore, the cascading options are valuable primarily in preserving the high performance of the element during its subsequent use.