Asphalt pavement service life emissions: An overlooked pollution source

ABSTRACTAmid rising concerns over infrastructure environmental impacts, VOCs emissions from asphalt pavements represent an important area of research. While production-phase emissions have been extensively documented in existing literature, service-life releases remain poorly quantified despite several critical factors: pavements' extensive cumulative surface area, continuous solar irradiation, and direct exposure to atmospheric oxidants (O3, OH·, NOx). Consequently, in-service asphalt pavements function as persistent diffuse emission sources contributing to urban air quality degradation throughout their multi-decade operational lifespans. It is understanable that emission rates are governed by binder composition, mixture design, temperature, solar radiation, humidity, and aging. As bio-modified binders derived from waste cooking oil (WCO) gain increasing adoption in pavement applications, understanding their service-life emission profiles becomes critical to comprehensively evaluate their environmental performance and identify potential compositional effects on urban air quality. This study quantified emission factors (μg/m2·h) from conventional asphalt and waste-cooking-oil-modified bioasphalt at 30, 50, and 70°C. Results show substantial temperature-dependent increases, with bioasphalt exhibiting notably higher releases dominated by carbonyl and aromatic compounds—particularly hexanal, pentanal, heptanal, nonanal, octanal, decanal, and furan 2-pentyl. These WCO-derived fatty acid degradation products constitute the primary emission class from bioasphalt, while conventional asphalt released substantial alkane species. Both materials demonstrate persistent VOC emissions under field-relevant thermal conditions, though compositional differences significantly influence emission speciation and atmospheric reactivity potential. Current knowledge gaps include absence of standardized measurement protocols and validated emission factors suitable for air quality inventories and life-cycle assessment frameworks. Given extensive urban roadway networks and continuous population exposure, comprehensive life-cycle assessments incorporating service-phase emissions are essential for accurately evaluating pavement contributions to urban air quality. This includes their role in tropospheric ozone formation and secondary organic aerosol generation and guiding sustainable infrastructure development under changing climate conditions.