Reusing Heavy-Section Steel in Buildings: Carbon Reduction Potential and Material Availability

Abstract

Designing with salvaged structural steel is a beneficial alternative for structural engineers to reduce embodied carbon in the built environment. However, there are still many regulatory and sectoral barriers to reusing hot-rolled steel sections in buildings at scale, including establishing its embodied impact reduction potential and minimizing the uncertainty regarding element availability. This paper first contextualizes structural steel and steel scrap supply chains throughout building construction and use. Next, a carbon equivalent analysis of reused steel and recycled steel was carried out, which considered the life cycle phases included in Environmental Product Declarations. These quantities were then amalgamated with industry and literature values and assessed for varying parameters, including geometric characteristics, transportation distances, and electric grid factors. From a cutoff, bottom-up life-cycle analysis, a 60%–83% reduction in greenhouse gas emissions was estimated from steel reuse instead of recycling, depending on the element and project. A high-level material flow analysis was conducted for the structural steel market in the United States, which indicated at its upper bound that the quantity of the existing steel heavy-section scrap could cover 80% of total consumed heavy-section steel and 140% of heavy-section imports. In short, this paper demonstrates the intrinsic carbon reduction value and scaling potential of steel reuse. Building with salvaged structural steel is a sustainable design strategy for structural engineers and architects to reduce embodied carbon in the built environment and to implement life-cycle oriented design of steel structures. This paper presents the case for steel reuse, and its intrinsic carbon reduction potential. It also aims to establish more certainty about the supply of steel elements and explains the implications that steel reuse has for stakeholders in the structural steel industry, through a discussion of real reuse projects and literature review. A robust understanding of the nature of available and projected heavy-section scrap stock helps engineers and architects discern which elements are available for reuse in their building projects. Understanding the benefits of reuse from the carbon reduction perspective will further incentivize reuse and increase circular adoption across the entire steel value chain.