An Approach for Performing Life Cycle Impact Assessment of Pavements for Evaluating Alternative Pavement Designs

摘要

Life Cycle Assessments (LCA) of pavements is currently used to compare alternate designs by appraising the environmental impacts. Life Cycle Impact Assessment (LCIA) is a key step in LCA, which models the emissions inventory into meaningful environment and human impacts. Although LCIA consists of four steps (classification, characterization, normalization, and weighting), most of the pavements LCA have been performed without normalization and weighting steps due to subjectivity involved. Normalization aims to associate impacts of a design to a set of reference values that is recognizable and understandable by the decision makers. The decisions made without considering normalization may lead to least sustainable pavement design. The objective of this study is to expand pavement LCA by including normalization and weighting in the process by proposing normalization and weighting approaches that will help in selecting sustainable pavement structure. To achieve objective of this study, LCA was performed on four equivalent pavement designs by estimating emissions for each pavement design for 30 years using various LCA datasets. The estimated emissions were further classified and characterized into various impact categories. External and internal normalization were performed on the characterized data. External normalization was performed using two reference systems US per capita emissions in 2008 and an average passenger car emissions. External normalization helps in understanding the magnitude of impacts due to a pavement as well as in differentiating the alternatives. Internal normalization assists in only comparing alternatives and needs no reference system. Based on the evaluation, it is proposed to use normalization and weighting for performing LCA of pavements.