Assessing the Carbon Balance for Mass Timbers Beyond the First Life

Abstract

Forests are an important carbon sink in the global carbon cycle and the carbon they store can be transferred into the built environment via wood products to maximize the forests’ carbon storage potential and mitigate global climate change. Mass timbers, specifically cross-laminated timber (CLT) and glulam, are engineered wood products of growing interest regarding their carbon storage benefits, due to their long lifespan. However, given that CLT is a relatively new product, there is a limited understanding of how CLT can be treated at the end-of-life (EOL) phase to maximize its carbon storage potential. This research focuses on (a) determining the proportions of mass timber in a building to be allocated to four EOL scenarios (reuse, recycle, incinerate, and landfill) (b) evaluating the climate benefits of each EOL scenario, and (c) determining the substitution effects associated with the products created in each scenario. Reusing and recycling demolition mass timber demonstrated the best net climate impacts due to the low embodied emissions and large amounts of temporal carbon storage. Conversely, substitution effects were highest for the bioenergy products created from incineration and landfilling; however, this benefit can only be realized once while the benefits of the products created from reuse or recycling can occur multiple times if a cascading recycling approach is considered.