Preliminary Life-Cycle Assessment of St. Louis County Bridge SLC 516

Abstract

The University of Minnesota Duluth Natural Resources Research Institute (NRRI) completed a preliminary, screening cradle-to-gate life-cycle assessment (LCA) of St. Louis County, MN bridge 516, which was constructed approximately 7.4 miles W/SW of Babbitt, MN over the Embarrass River. The LCA utilized data from the bill of materials (BOM) and construction drawings, which were provided by Dr. Brian Brashaw of the USDA Forest Service, Forest Products Laboratory (FPL). The system boundary included material and fuel consumption for timber and structural steel materials fabrication; material and fuel consumption for fabrication of steel hardware, bituminous overlay, and related components; and transport of materials to the construction site. Because this preliminary screening LCA study was cradle-to-gate, use phase activities and disposal/recycling of the timber bridge were excluded. The majority of the life-cycle inventory data was secondary data from the DATASMART life-cycle inventory (LCI) database. This study also used the cut-off approach method for recycling and utilized the LTS 2019 method to translate the LCI data into environmental impacts; this method combines the ReCiPe Endpoint (H) v1.03 method with three endpoint categories (Human Health, Ecosystems, Resources) and the Cumulative Energy Demand, Climate Change, and Water Use impact categories. It was found that the steel beam supports account for the largest portion of total impacts in each impact category, ranging from 32% to 77%, while the glulam deck panels contribute 24% to 36% of the impacts in four of the six impact categories. The galvanized steel components and asphalt contribute an average of 12% and 7% of the impacts in each impact category, respectively.