Environmental Impact Comparison Analysis between a Traditional Hot Mixed Asphalt (HMA) and with the Addition of Recycled Post-Consumer Polyethylene Terephthalate (RPET) through the Life Cycle Assessment (LCA) Methodology

Abstract

The present study presents a cradle-to-built life cycle assessment (LCA) for a road pavements structure of hot mixed asphalt (HMA) with recycled post-consumer polyethylene terephthalate (RPET) addition through the “dry” process using a comparison analysis between declared units equivalent of 1 ton of produced mix and functional units equivalent of 1 m2 pavement variants under the Brazilian “National Design Methodology” (MeDiNa), in contrast with a conventional mix variant. The Tool TRACI 2.0 for reducing and assessing chemical and other environmental impacts was applied for each alternative, assessing the impacts into categories such as acidification, eutrophication, freshwater ecotoxicity, global warming potential, human health, ozone depletion, and smog formation. The life-cycle impact assessment results were interpreted through an internal normalization criteria and weighting rule, obtaining an environmental score for each alternative and allowing an easy stakeholder interpretation. Considering the better mechanical properties and overall functional performance of the HMA + RPET mixes, the functional unit comparison on LCA methodology results in savings in all environmental impact categories for each square meter of pavement constructed and ready to use. For the functional units, the HMA + RPET pavement structures (FU 2 and FU 3) resulted in lower environmental scores (ES) with 49.2 and 47.1, respectively, representing a difference of 26.9 and 29 score points in comparison to the conventional pavement structure (FU 1 − C), with an ES of 76.1. It represents 38% of environmental savings in terms of the environmental score in favor of sustainable pavement alternatives. Focusing on the impact in global warming potential, the use of RPET in the HMA mixes for pavement design can result in savings up to 47.44% of impact decrease (20.4 ES) in comparison with the conventional-mix pavement structure proposal. This result supports the environmental sustainability of the HMA + RPET mixes and is a precedent for future research on new geotechnical and pavement alternative materials.

A Review on Life Cycle Assessment of Pavements in Brazil: Evaluating Environmental Impacts and Pavement Performance Integrating the International Roughness Index

“…They demonstrated significant variations from one study to another. Asphalt, a material known for its significant contribution to energy consumption in asphalt mixture construction [49], demonstrated varying transportation distances in the range of 98 km [44] and 750 km [53], as reported in separate studies. The broad distances can be attributed largely to the vast territorial expanse of the country.…”

“…The average global warming emissions were found to be 50.59 kg of CO 2 eq per square meter of pavement, with a standard deviation of 6.86 kg of CO 2 eq. What was also intriguing was that, in the quantitative comparison, every study analyzed, except Osorto et al [53], had used the Ecoinvent database to some extent. Furthermore, five out of the seven case studies commonly employed the CML method for LCIA, and four out of the seven utilized the SimaPro software.…”

“…LCA research conducted in Brazil does not adequately support the claim that the use of recycled materials, such as post-consumer plastic and tire rubber, and WMA techniques in the construction of pavements is environmentally sustainable. The only existing study in this specific area was conducted by Osorto et al [53]. A comparative analysis was performed between a traditional HMA pavement and one that integrated RPET via the dry process.…”

A Comparative Study of the Effect of Moisture Susceptibility on Polyethylene Terephthalate–Modified Asphalt Mixes under Different Regulatory Procedures

“…Rivera et al developed a study on the environmental impact assessment of plastics and polymer recycling from virgin use to post-consumer recycling as fibre or composites in the paving industry, applying the life cycle assessment (LCA) methodology. The study concluded that the use of PET in asphalt mixes results in a decrease of up to 38% in the overall environmental savings in terms of environmental score in favour of sustainable pavement alternatives [17].…”