Developing a Benchmarking Methodology for Concrete Global Warming Potentials in North America

Abstract

The objective of this paper is to develop a methodology for estimating the statistical distributions associated with cradle-to-gate (A1–A3) concrete global warming potentials (GWPs) within the United States. When applied, this methodology serves as a framework for identifying benchmarks for product-level GWP. Cement production contributes to approximately 90% of the GWP for concrete mixtures. In this study, publicly available environmental product declarations for Type I/II, Type IL, and Type III cements were collected and the best fitting distributions for the cement GWPs were established and used in Monte Carlo simulations for analyzing the impact of cement on concrete GWP benchmarks. The distribution parameters for GWPs of concretes incorporating each of the three cement types were calculated and applied to determine 20th percentile, 40th percentile, and average GWP reference values. Additionally, the concrete GWP results were compared to the national industry-average GWP for the same concrete class. While this paper focuses on exploring the statistical distributions to develop a benchmarking methodology for concrete A1–A3 GWPs, this methodology can be expanded to explore the distributions of other products, product classes, life cycle inventory modules, and environmental impact indicators. The cement and concrete industries, particularly infrastructure owners developing sustainability metric thresholds, may use the benchmarking methodology and distribution results herein to develop reference values for cement and concrete global warming potentials (GWPs) of similar classification. This benchmarking methodology and the results are particularly relevant to state departments of transportation applying to the Low Carbon Transportation Materials Grant Program and entities like the US General Services Agency, who are currently using benchmarking methodology to implement sustainable procurement of pavements. This methodology is additionally relevant for the Environmental Protection Agency, which is looking to set thresholds as part of their green labelling program. The concrete industry and producers in addition can use these insights to compete by differentiating their mixes as low carbon. The concrete materials industry can use this analysis to assess how their industry is performing as a whole in developing cement and concrete. If desired, members of the industry could use these benchmarking results to make plant and production modifications that allow for further competition toward sustainable concrete mixtures. The benchmarking methodology can additionally be employed by owner agencies to develop greenhouse gas emission reference values for a specific state or region. This methodology can be applied to other products, product classes, regions, and midpoint environmental impact indicators.