Dynamic LCA of the increased use of wood in buildings and its consequences: Integration of CO2 sequestration and material substitutions

Abstract

Wood products can have a lower impact on climate change (CC) than other building materials, and their carbon content can transform buildings into temporary carbon sinks. However, the large-scale use of wood products in buildings requires a better understanding of their consequences to support CC policies. The consequential life cycle inventory of such products contains elementary flows with values sometimes greater sometimes less than zero. Therefore, their static assessment did not show the influence of carbon uptake and release, either during or after the temporal boundary of the system. The originality lies in the combination of the dynamic modeling of tree harvesting and growth, temporary carbon storage, end-of-life (EOL) strategies, material substitution, and characterization factors in a consequential life cycle assessment (LCA). This combination highlights the extent to which material substitution, EOL strategies, and carbon sequestration can be decisive. In addition, it addresses the static and dynamic measurements of radiative forcing (W.m−2) and the carbon dioxide (CO2) equivalent (CO2eq.). In this case study, material substitution contributed the most to result, followed by post-harvest CO2 sequestration. In terms of metrics, the conventional static LCA overestimates the long-term cumulative impact on CC (tonne CO2eq.) without providing information on the short-term impact of the case study. In addition, the assessment of such a dynamic consequential life cycle inventory (LCI) with a dynamic metric provides more specific information, regardless of the temporal boundary. However, the absolute dynamic metrics (W.m−2) should support the relative dynamic metric (tonne CO2eq.1st year) to avoid misleading conclusions.