Life-Cycle Greenhouse Gases and Energy Consumption for Material and Construction Phases of Pavement with Traffic Delay

Abstract

This paper discusses an approach to life-cycle assessment (LCA) for pavement construction applications. The scope of the study included the material production and construction phases pertaining to the upper layers of pavement; the aim was to quantify energy consumption and greenhouse gases. Life-cycle inventory data were taken from literature sources and questionnaires, with system boundaries including upstream processes for the production of major materials and fuels. The use of regionalized data was necessary to ensure proper application of LCA. Thus, for the material production phase, this LCA included preliminary data collected from regional surveys and incorporated a localized life-cycle model for asphalt binder production. The impact of traffic delay was modeled in the construction phase with the U.S. Environmental Protection Agency's Motor Vehicle Emission Simulator. A case study was performed for a simulated two-lane reconstruction of an existing Interstate in northern Illinois. The energy consumption in the material phase [5,425 million (M) Btu/lane mile] was significantly higher than that of the construction phase (137 MBtu). The same pattern held for global warming potential [405 versus 12.0 tons of carbon dioxide equivalent (CO2e)]. With respect to traffic delay, the values of global warming potential (between 2.0 and 9.9 tons of CO2e) and energy consumption (between 22.5 and 116.8 MBtu) were comparable to those from the construction phase.