Life cycle assessment on construction and demolition waste recycling: a systematic review analyzing three important quality aspects

Abstract

Abstract Purpose Life cycle assessment (LCA) is increasingly being applied to construction and demolition waste (CDW) recycling. But what is the current state of LCA studies on CDW recycling? In the context of circular economy, several aspects become important in LCA, such as avoided impacts and consideration of the quality of recycled materials. The aim of this study is to identify inconsistencies and best practices, and then provide recommendations for future LCA studies focusing on CDW recycling. Methods We conducted a systematic literature review on 76 journal articles. First, a general mapping of the selected studies was performed including the temporal and geographical distribution, and a bibliometric analysis to capture the linkages between the studies. Within the LCA content-based analysis, an in-depth assessment of three important quality aspects: (1) quality of the study based on the applied LCA methodology, (2) inclusion of material quality in LCA, and (3) data quality considering sensitivity and uncertainty analyses, was carried out. Major LCA components such as functional unit (FU), software, database, system approach (attributional or consequential), allocation method, life cycle impact assessment, and interpretation were evaluated. A special emphasis was placed on avoided impacts and the inclusion of recycled material quality in the LCA. Results and discussion In this review, it was found that many essential elements of LCA were missing or not implemented correctly. For example, in the definition of FU, some studies did not mention any FU, others defined an invalid FU, and most of the studies defined a uniform FU, which was most likely confused with the reference flow. The main problem observed is the lack of transparent reporting on the different elements of LCA. Regarding avoided impacts, for instance, only 13 studies reported the avoided materials and their substitution coefficients. Also, 6 studies used the term “virgin material” for avoided impacts without further information, which is a very broad term and difficult to interpret. Furthermore, only 12 studies included the quality of recycled material in the LCA. Conclusion To obtain reliable LCA results, the practitioners should follow the principal LCA methodology and peer-reviewers should ensure the proper implementation. In CDW recycling, the differentiation between downcycling and recycling is essential; therefore, the quality of recycled materials should be included in the LCA. Considering inconsistent implementation of avoided impacts, a standardized and well-defined avoided impact framework is suggested to be developed to improve the quality and reliability of future LCA studies.