Characterisation of ammonia emissions from gasoline and gasoline hybrid passenger cars
Naomi J. Farren, Jack Davison, Rebecca Rose, Rebecca L. Wagner, David C. Carslaw · 2021 · 22 citationsRead the paper
Recent evidence suggests NH3 emissions from road vehicles play an important role in the formation of fine particulate matter, especially in urban areas. However, there is little data available for NH3 emitted from road vehicles under real driving conditions, in part due to its lack of regulation in vehicle emission legislation. In this study, we use 210,000 vehicle emission remote sensing measurements to evaluate the complex mix of factors affecting NH3 emissions from gasoline and gasoline hybrid passenger cars. The influence of vehicle model year and manufacturer on NH3 emissions is considered, as well as the effect of vehicle deterioration. It is found that the amount of NH3 emitted increases as vehicle mileage increases. A comparison of cold start and hot exhaust NH3 emissions reveals that on average, cold start emissions are a factor of 1.7 times higher. New NH3 emission factors are developed, in addition to speed-emission curves that are potentially useful for national inventories. A new application of remote sensing data is reported, whereby the proportion of failed CO2 measurements for hybrid vehicles provides unique insight into the real world battery use of both conventional hybrid electric and plug-in hybrid electric vehicles, which is used to refine the NH3 emission factors for these vehicles.
What the full text shows
Tested in real conditions- Gasoline passenger cars (2000-2019) exhibit fuel-specific NH3 emissions ranging from 0.42 to 1.11 g kg-1. — 0.42-1.11 g kg-1 (Gasoline passenger cars, 2000-2019 model years)
- Hybrid electric cars (2005-2018) exhibit lower NH3 emissions than gasoline cars. — 0.21-0.42 g kg-1 (Hybrid electric cars, 2005-2018 model years, adjusted for battery use)
- Plug-in hybrid electric vehicles (PHEVs, 2015-2017) exhibit the lowest NH3 emissions among the studied groups. — 0.15-0.26 g kg-1 (PHEVs, 2015-2017 model years, adjusted for battery use)
- Cold start NH3 emissions are significantly higher than hot exhaust emissions. — 1.7 to 2.5 times higher (General average (1.7x); Euro 5 and 6 vehicles (2.5x))
- NH3 emissions increase as vehicle mileage increases. (Gasoline passenger cars)
- NH3 emissions gradually decrease with increasing Euro class. (Gasoline passenger cars, accounting for vehicle mileage)
- Setup
- 210,000 gasoline and hybrid vehicle measurements across 37 sites in the UK (2017-2020).
- How
- Used vehicle emission remote sensing (FEAT and RSD5000 instruments) to measure exhaust plumes of passing vehicles. Adjusted hybrid emission factors by using the proportion of failed CO2 measurements as a proxy for battery usage (utility factor).
- Limitations
- Instrumentation is not weatherproof (no measurements during rain) · Remote sensing cannot distinguish battery mode from engine mode without CO2 proxy · Cold start measurements relied on site-specific assumptions (campus entry/exit)
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it