Assessment of the environmental impact of timber and its potential to mitigate embodied GHG emissions

Currently, the world is undergoing the biggest wave of urban growth in history. To accommodate this unprecedented growth, adding more than 230 billion m2 of new floor area to the global building stock by 2060 is expected. As embodied emissions are responsible for 11% of annual greenhouse gas (GHG) emissions globally, an increase in embodied emissions from new construction will put tremendous additional pressure on the natural environment. To investigate the environmental impact of timber and potential of mitigating the increase in embodied GHG emissions from new residential constructions, a life cycle assessment (LCA) is performed for the production stage of three low-energy modular buildings. The results suggested that by substituting reinforced concrete (RC) and masonry (M) with cross-laminated timber (CLT) in the building structure, 14.62% and 12.94% of emissions could be avoided on a building level, respectively. However, the substitution leads to a significant increase in land use impact. In order to get a sense of mitigation potential on the larger scale, the mitigation potential of embodied GHG emissions is investigated for an expected residential building stock new floor area growth predictions depending on the regional residential building structural material choice in the world key regions for periods from 2017 to 2060. Under the assumptions made, the preliminary results suggest that by 2060 a certain amount of emissions could be avoided if conventional structural materials were substituted with CLT, however, emissions from new floor area additions are still substantial. Moreover, global GHG mitigation potential raises new concerns and questions that need to be further investigated. In addition, the importance of considering the land use impact in the LCA studies of bio-based construction materials is highlighted.