Solutions to achieve carbon-neutral mixtures for the U.S. pavement network

Abstract

Abstract

Purpose Several studies have evaluated GHG mitigation solutions for asphalt and concrete mixtures at the network level. However, proposed solutions usually focus on partial decarbonization; the simultaneous interactions and effects of these solutions have not been fully studied. In this study, the state-level embodied carbon attributed to the U.S. pavement network was calculated using a dynamic material flow analysis and life cycle assessment model.

Methods A pavement management system model was developed to forecast the performance and characteristics of the national pavement network using data science approaches. The annual quantity of materials required for the pavement treatment actions in each state was estimated based on budget allocation and regional decision trees. Then, multiple solutions for achieving carbon-neutral mixtures by 2050 were introduced to the state-level material flows to assess the GHG savings and abatement cost associated with the solutions.

Results and discussion The annual GHG emissions of the U.S. pavement network will increase by 19% if no change in decarbonization occurs (from 11.9 to 13.3 Mt CO2eq). Under a projected improvement scenario, concrete and asphalt pavements are anticipated to have an average 38 and 14% embodied impact reduction by 2050, respectively. Nevertheless, carbon-neutral mixtures can only be achieved if multiple solutions for reducing, avoiding, and neutralizing the embodied impact are applied simultaneously. The effectiveness of many of these solutions depends on a 100% renewable electricity supply. From a cost perspective, 41% of the GHG savings toward carbon neutrality can be achieved at a negative or almost net-zero cost.

Conclusions Carbon-neutral asphalt and concrete mixtures can be achieved if multiple solutions for reducing, avoiding, and neutralizing the embodied impact are applied simultaneously and the electricity grid is decarbonized rapidly. For future research, the scope of analysis for pavements should reach beyond embodied impacts and incorporate use phase emissions and service life alterations as part of an analysis to holistically assess carbon neutrality from a life cycle perspective.