Research Methodology
The research was conducted in three distinct phases. The first phase focused on data collection; the second phase focused on analysis of the data and assessment of the established carbon footprints and the third phase focused on the development of this bench marking tool.
Phase I: Data collection phase
Data was collected from 14 pavement construction and maintenance project sites to develop comprehensive inventories of material and equipment use for each project. The 14 projects included HMA and concrete reconstruction, maintenance and rehabilitation projects.
Emission factors were collected from existing literature in the field, and historical databases to identify impacts during the material aquisition and manufacturing, pavement construction, maintenance and rehabilitation, and use phase of pavements.
Information pertinent to emissions during the service life of the pavement – including but not limited to increased traffic delay times and reroutes during construction and rehabilitation operations were considered using the MOVES simulation package.
Phase II: Inventory Development
Detailed inventories were developed by organizing the data collected into material and equipment categories. Careful attention was paid to count materials for each construction payitem. All equipment usage on site was considered.
Phase III: Assessment
An assessment tool was prepared that allows further investigation and benchmarking of highway construction projects based on inventories developed. It allows the consideration of using alternative designs and materials, and long-term pavement performance. The tool will support ways of identify standards that help reduce greenhouse gas emissions during the life-cycle of pavements.
Life Cycle Assessment
The prevalent approach to calculating greenhouse gas emissions of products or processes is to systematically account for the different stages through the life cycle, consisting of the materials extraction phase, manufacturing/production stage, the use phase and the ultimate end-of-life/disposal phase. Such an approach is called the Life Cycle Assessment (LCA).
The collected data was analyzed using state-of-the art LCA techniques to develop integrative assessments of the economic and environmental impacts of different types of pavement materials. Environmental impacts can be assessed using approaches such as Economic Input Output Life-cycle Assessment (EIO-LCA) (Hendrickson et al. 1998, Cicas et al. 2007), and SimaPro. The PI has conducted previous research in assessing environmental and economic impacts of pavements and green-building components using EIO-LCA (Mukherjee et al. 2006, Muga et al. 2008, Muga et al. 2009). The life-cycle assessment illustrates major contributors to environmental emissions in units of carbon emissions.