Preliminary Life-Cycle Assessment of Hennepin County Bridge 27C53

Abstract

The University of Minnesota Duluth Natural Resources Research Institute (NRRI) completed a preliminary, screening cradle-to-gate life-cycle assessment (LCA) of Hennepin County, MN bridge 27C53, which was constructed on County Road 202 in the Elm Creek Park Reserve. 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 bituminous (asphalt) overlay generally accounted for the largest impact in most impact categories, ranging from 9% to 46%, while the nail-laminated deck panels contributed 18% to 24% of the impacts in five of the six impact categories. The steel hardware, structural steel, and copper naphthenate (CuNap)-treated solid timber components contributed an average of 25%, 8%, and 5% of the impacts in each impact category, respectively.