Unreported VOC Emissions from Road Transport Including from Electric Vehicles

Measurementsshow that screenwash application dominatesvehicular VOC emissions and is missing from road transport inventories. There are widespreadpolicy assumptions that the phase-out of gasolineand diesel internal combustion engines will over time lead to muchreduced emissions of Volatile Organic Compounds (VOCs) from road transportand related fuels. However, the use of real-world emissions measurementsfrom a new mobile air quality monitoring station demonstrated a largeunderestimation of alcohol-based species in road transport emissionsinventories. Scaling of industry sales statistics enabled the discrepancyto be attributed to the use of ancillary solvent products such asscreenwash and deicer which are not included in internationally appliedvehicle emission methodologies. A fleet average nonfuel nonexhaustVOC emission factor of 58 +/- 39 mg veh(-1) km(-1) was calculated for the missing source, which is greaterthan the total of all VOCs emitted from vehicle exhausts and theirassociated evaporative fuel losses. These emissions are independentof the vehicle energy/propulsion system and therefore applicable toall road vehicle types including those with battery-electric powertrains.In contrast to predictions, vehicle VOC emissions may actually increasegiven a predicted growth in total vehicle kilometers driven in a futureelectrified fleet and will undergo a complete VOC respeciation dueto the source change.

Automated summary

Measurements reveal that screenwash application is the main source of vehicular VOC emissions, which is not included in road transport inventories. The assumption that phasing out gasoline and diesel engines will reduce VOC emissions from road transport is undermined by real-world emissions measurements showing a significant underestimation of alcohol-based species. This discrepancy is attributed to the use of ancillary solvent products like screenwash and deicer, which are not included in internationally applied vehicle emission methodologies.