The embodied carbon of mass timber and concrete buildings in Australia: An uncertainty analysis

Abstract

This research uses uncertainty analysis to determine and compare the range of embodied carbon outcomes of mid-rise mass timber and concrete buildings in Australia. In doing so, it measures the variability in inventory databases, transportation distance, lifetime of building components, biogenic carbon emissions, carbonation of concrete materials and end-of-life scenarios. Through the use of Monte Carlo analysis, the research found that the embodied carbon of a mass timber building ranged from 196 kgCO2-e/m2 to 590 kgCO2-e/m2 with a mean of 417 kgCO2-e/m2. For a post-tensioned concrete building the range was 307 kgCO2-e/m2 to 618 kgCO2-e/m2 with a mean of 465 kgCO2-e/m2. This equates to a 48 kgCO2-e/m2 reduction in mean embodied carbon for the mass timber building. Using deterministic analysis, previous research suggested a more substantive 129 kgCO2-e/m2 reduction. These results demonstrate that mass timber buildings do typically have a lower embodied carbon, compared to concrete buildings, however the significance of this depends on the assumptions made, and the input data used. For the concrete building, the variation in embodied carbon is primarily influenced by the inventory data and building products' lifetime. The greater range of embodied carbon in the mass timber building is due to variations associated with the inventory data, allocation of biogenic carbon emissions (sequestration, and forest management losses) and, different end-of-life scenarios associated with timber products. Despite this, the research suggests that with a carefully planned end-of-life strategy, mass timber mid-rise buildings have the potential to benefit from lower embodied carbon emissions, as compared to concrete buildings, across their full lifecycle.