Integrating Bio-Based Materials and Alternative Fuels in Flexible Pavement Life Cycle Assessment

The transportation sector’s relatively large greenhouse gas (GHG) footprint highlights the need for low-carbon strategies at every stage of the flexible pavement life cycle. This study performed a comparative life cycle assessment evaluating alternative options in the materials, construction, use, and maintenance and rehabilitation (M&R) stages. Conventional asphalt binder was replaced with bio-binder derived from wastewater-grown algae. In the construction and use stages, diesel used in construction equipment was substituted with 100% renewable diesel (RD100), biodiesel, hydrogen, electricity, and compressed natural gas. The use stage emissions were quantified across a spectrum of alternative fuel uptake scenarios. The analysis compared three M&R treatments: mill-and-overlay, full-depth reclamation (FDR), and cold in-place recycling (CIR). A sensitivity analysis examined trade-offs between increasing bio-binder substitution and the accompanying reductions in pavement service life. The results showed that replacing conventional binder with bio-binder lowered material-stage emissions from 116 to 47 tnCO 2 eq at 50% dosage and turned net-negative beyond ∼85% substitution. Switching equipment fuel from diesel to RD100 cut GHG emissions by 80%. Hydrogen and electricity achieved 91.1% and 44.5% savings, respectively. The benefits of using electric powertrains in equipment highly depended on the source of electricity. In the use stage, high electric vehicle adoption on a renewable-heavy grid lowered total emissions by 53%, but the same scenario on a coal-based grid increased them by 25%. Among M&R options, CIR had the lowest GHG burden and FDR the highest. The study demonstrated that every pavement life cycle stage offers clear potential to lower overall GHG emissions when low-carbon alternatives are used.