Wood as a carbon mitigating building material: A review of consequential LCA and biogenic carbon characteristics

Abstract

Buildings can potentially be carbon sinks by use of wood under correct circumstances because wood sequesters CO2 i.e., biogenic carbon, from the atmosphere by photosynthesis during growth. Consequential life cycle assessment (CLCA) works as a decision support tool to assess consequences from a change in demand by including only the processes that are affected by this demand through market-based modelling. This study aims to review current research about CLCA on wood in buildings. First, by examining methodological approaches linked to CLCA modelling and biogenic carbon accounting of wood in buildings. Second, to evaluate conclusions of studies using CLCA on wood in buildings. We conducted a literature review of 13 articles that fulfilled the criteria of stating to conduct a CLCA concerning either buildings, components, or materials where wood is one of the materials. The application of the reviewed studies include: method development, reuse, testing end of life aspects, CLCA inventory modelling, and comparison of ACLA and CLCA. The CLCA inventory of small-scale studies comprise a wide spectrum of methods ranging from simplistic to advanced methods, often retrospective. All large-scale studies integrate sophisticated modelling of prospective analysis. Dynamic time-dependent biogenic carbon accounting and indirect land use change (iLUC) are rarely represented. Although, both aspects have an impact on whether wood buildings respectively work as carbon sinks or provide net GHG emissions. Wood multi-storey buildings generally perform environmentally better than concrete and steel buildings due to wood displaces these materials and residues substitute fossil energy. End of life scenarios, choice of substituted production, retro- and prospective data, and the share of recycled steel further influence carbon mitigating potential of wood in buildings. Research of CLCA on wood in buildings are many-fold. Some studies partially evade inclusion of some CLCA aspects i.e., market delimitation, market trend, affected suppliers, and substitution. A simultaneously high integration of both CLCA, time-dependent biogenic carbon accounting, and iLUC in the same study is almost absent. Consequently, more empirical and methodological CLCA studies are needed while including dynamic time-dependent biogenic carbon accounting to improve understanding of implications of policy decisions in transitions towards increased use of wood in buildings.