Edinburgh Napier University

  The increasing interest in bio-based construction materials has resulted in the emergence of the concept of “buildings as a carbon sink”. Quantifying and comparing the effects of carbon sequestration and storage in buildings from a life cycle perspective involves the evaluation of flows and processes taking place at different timescales and across ecological, technological, and economic domains. This scoping review sheds light on the heterogeneous body of approaches and results from relevant scientific literature of the past decade: 180 articles were reviewed following a systematic search and relevance-checking process. Contributions are evaluated based on the scale of interest (material, building, building stock), the sequestration mechanism (photosynthesis, carbonation) and the accounting methodology adopted to quantify global warming. The majority of works taking a life cycle perspective adopt static methods, with only a few accounting for dynamic effects over time, although more recent studies do tend to recognise the need for dynamic life cycle assessment. A characterisation of current and future carbon storage in the global building stock is still needed, and substantial work remains to be done to validate the theory of buildings as a carbon sink to mitigate the effects of climate change. Reports on carbon stored in durable construction products and buildings mostly find cumulative effects that are less than emissions from fossil fuel use in a single year (ranging from negligible to 175%). Furthermore, net gains in storage in the built environment can be offset by net losses in forest carbon, and the benefits of substitution with wood are sometimes overstated. Further adoption of bio-based construction materials can – at best – only make a substantial contribution to climate change mitigation in the context of rapid global progress in decarbonisation.