The effect of geographic boundaries on the results of a regional life cycle assessment of using recycled aggregate in concrete

Many life cycle assessment (LCA) studies have been conducted in the past to measure the environmental impacts of producing concrete with coarse recycled aggregate (CRA) obtained from processing construction and demolition waste (CDW) and compare them with those of concrete with coarse natural aggregate (CNA). The present work studies the influence of the choice of geographic boundaries on the results of regional LCA studies in a large and dense metropolitan area. Specifically, the study incorporates an LCA on the CDW produced, processed, and used in concrete in the five boroughs of New Yok City. The results were compared to those from a similar past study with geographic boundaries far beyond the five boroughs forming an area over 10 times larger. The comparison revealed that when the boundary is limited to the borders of New York City, the environmental benefits of replacing CNA with CRA in concrete caused by the avoided transportation of CDW to landfills are significantly (often over 100%) higher. In addition, it was found that when concrete with CNA is produced in the five boroughs the overall environmental burden of transporting raw materials to concrete plants is approximately 25% higher.