Deconstruction for selective reuse of structural building elements – a case study to identify opportunities and challenges

Abstract

The construction industry accounts for roughly 70% of global natural resource consumption (United Nations Environment Programme, 2017) and is responsible for roughly 39% of global greenhouse gas emissions (World Green Building Council, 2019). Due to a lack of consideration for waste management in early design stages (Esa et al., 2017), 50% of all construction and demolition waste is created during the End-of-Life (EoL) stage. A proposed solution to these issues is selective reuse. It is hypothesised that selective reuse in the construction industry can potentially target 3 billion tons of raw materials globally, promoting emissions reduction, waste reduction, energy savings and raw materials preservation (Cai and Waldmann, 2019; Bertin et al., 2020). However, the feasibility of reuse of structural elements is reliant on its deconstruction methodology as well as its condition prior to reuse. Furthermore, the process to assess this feasibility (accounting for time, cost and emissions) has only been considered theoretically, focussing on hypothetical structures. The aim of this study is to investigate a process to evaluate the extent of benefit of deconstructing for selective reuse. By considering a real structure with input from relevant professionals, the study considers the sensitivity of various steps in such a process. Through the development of a structural condition assessment system, digital twin and material inventory, the study investigated the extent of benefit of deconstructing for selective reuse, comparing various extents of reuse using a Life-cycle Assessment based evaluation and cost quantification process. The study considered the emissions and costs associated with the structure’s End-of-Life, namely deconstruction or demolition and subsequent transport and disposal. Furthermore, a quantification of costs and emissions associated with the refurbishment of reused items was made. During the Life-cycle Assessment calculations, Embodied Carbon Factors from various data sources and databases were included, including data from relevant professionals. It was found that increased reuse is associated with decreased equivalent carbon dioxide emissions and decreased costs, but a certain degree of reuse is required for the emissions and costs associated with deconstruction to be justified. It was found that the choice of Embodied Carbon Factor database had little influence on the overall trends and conclusions established. Moreover, the study investigated the sensitivity of various assumptions made. The equivalent emissions calculated from the Life-cycle Assessment were found to be insensitive to the Embodied Carbon Factors and factors chosen for demolition and construction emissions as well as the Embodied Carbon Factors and factors chosen for waste processing and disposal of steel and timber. Aside from raw materials and their associated emissions, the transportation emissions’ assumptions (specifically its Embodied Carbon Factor and assumed distance) are most influential to total embodied carbon. Furthermore, the equivalent emissions were found to be sensitive to the assumptions and Embodied Carbon Factors used to account for waste processing and disposal of concrete. The assumed transportation related assumptions and the waste disposal for a material in which a high quantity is present, have been shown to require careful consideration.