Non-exhaust PM emissions from electric vehicles

Electric vehicles (EVs) are regarded as zero emission vehicles due to the absence of exhaust emissions. However, they still contribute non-exhaust particulate matter (PM) emissions, generated by brake wear, tire wear, road wear, and resuspended road dust. In fact, because EVs are heavier than internal combustion engine vehicles (ICEVs), their non-exhaust emissions are like to be even higher. While total PM emissions, including exhaust and non-exhaust PM emissions, from ICEVs and EVs have been compared based on the emission factors (EFs) listed in national emission inventories, there have been no comparisons based on experimental determinations.In this study, exhaust and non-exhaust emissions generated from a gasoline ICEV, diesel ICEV, and EV were experimentally investigated. The results showed that the EFs for the total PM emissions of ICEVs and EV were dependent on the inclusion of secondary exhaust PM, the brake pad type, and the regenerative braking intensity of the EV. When only primary exhaust PM emissions were considered in vehicles equipped with non-asbestos organic (NAO) brake pads, the total PM10 EF of the EV (47.7–49.3 mg/V·km) was 10–17 % higher than those of the gasoline ICEV (42.3 mg/V·km) and diesel ICEV (43.2 mg/V·km). However, in vehicles equipped with low-metallic (LM) brake pads, the total PM10 EF of the EV (49.2–57.7 mg/V·km) was comparable or lower than those of the gasoline ICEV (56.3 mg/V·km) and diesel ICEV (57.2 mg/V·km). When secondary PM emissions were included, the EF was always significantly lower for the EV than ICEVs. The total PM10 EF of the EV (47.7–57.7 mg/V·km) was lower than those of the gasoline ICEV (56.5–70.5 mg/V·km) and diesel ICEV (58.0–72.0 mg/V·km). Since secondary PM particles are mostly of submicron size, the EFs of the PM2.5 fraction of the ICEVs (28.7–33.0 mg/V·km) were two times higher than those of the EV (13.9–17.4 mg/V·km).

<div class="section abstract"><div class="htmlview paragraph">To pursue the target of the “net-zero” emission by 2050 and to reduce the most harmful pollutant emissions from road traffic, more specifically of particulate matter (PM), the transportation sector is subject to significant changes. A transition from internal combustion engine passenger cars (ICEVs) to hybrid vehicles (HEVs) and battery-electric vehicles (BEVs) is taking place. This transition, however, must be carefully examined from different perspectives, as hybridization/electrification may not reduce the levels of PM and CO<sub>2</sub> as much as expected. In this work, exhaust and non-exhaust PM emissions of a vehicle powered with an internal combustion engine, and of the same vehicle in plug-in hybrid and electric configurations is carried out, by using the emission factors approach. The main objective is the evaluation of the impact of vehicle weight, of percentage of regenerative braking and of energy management strategy (for hybrid configuration), on tire, wear and road surface wear, which are the most important non-exhaust PM sources. In particular, as most of the studies focus on a comparison between ICEs and BEVs, the current analysis aims at evaluating if the plug-in hybrid configuration, which is half-way between ICE and BEV, can overcome the limitations of electrification and of ICEs in terms of PM emissions. Results for gasoline engine show that a weight increase of 31% and 40% for the hybrid and electric configurations, respectively, with respect to the ICE version, contributes to increase the total PM<sub>10</sub> of about 16% and PM<sub>2.5</sub> of 9% for PHEV. For BEV, these values amount to 20% for PM<sub>10</sub> and to 4% for PM<sub>2.5</sub>. Adoption of regenerative braking significantly contributes to counteract the effects of a higher weight, so that overall, for PHEV and BEV, total PM emissions are reduced with respect to the ICE versions. In particular, total PM emissions (both PM<sub>10</sub> and PM<sub>2.5</sub>) are reduced of about 3% for PHEV and of 13% for BEV. For the diesel engine, where the weight difference between the ICE and PHEV and BEV versions are more limited (+8% for PHEV and +36% for BEV), higher beneficial effects related to regenerative braking are achieved, so that total PM emissions are reduced of 13% for PHEV and of 14% for BEV, with respect to ICE.</div></div>

Exhaust and non-exhaust airborne particles from diesel and electric buses in Xi'an: A comparative analysis

Vehicles equipped with internal combustion engines are known as important sources of particulate matter (PM) emissions. Many countries are aware of this issue. They are keen in converting internal combustion engine vehicles to electric vehicles (EV) to reduce PM problems. However, various past research works claimed that EV also emit PM like conventional vehicles due to their non-exhaust emissions from brake wear, tyre wear, road surface wear, and resuspension of road dust. In addition, strong evidence showed that there was indeed a positive correlation between the weight of vehicle and amounts of non-exhaust PM emissions.The current study is aimed to measure on-road non-exhaust PM emissions from a hybrid electric vehicle during a braking sequence at various payloads. An onboard PM measuring device is attached nearby the center cap bore of the left front wheel on the tested hybrid electric vehicle. PM1, PM2.5, and PM10 measurements are monitored during braking sequences in the electrified vehicle mode. The increase payloads that affect tendency of non-exhaust PM emissions are observed. The PM emission pattern during braking sequence is captured by the current PM measuring setup as seen in the literature. Based on this experiment, the additional payloads of 60–70 kg increase the amount of non-exhaust PM2.5 and PM10 emissions almost 25%. The effects of increasing payloads on PM2.5 and PM10 emissions can be clearly observed as a linear relationship. However, for PM1 emissions, when increasing payloads, a certain cut point is observed at the payload of 130 kg. Adding payloads more than 130 kg do not affect the amount of PM1 emissions.

The performance of an abrasive is dependent on its properties as well as the operating conditions during blasting. This study was undertaken to simulate enclosed blasting operations using steel shot and grit on rusted and painted steel panels; and collect and measure total particulate matter (PM) emissions at commonly used blast pressure and feed rate settings. U.S. EPA source sampling methods were used to sample emissions and estimate uncontrolled total PM emission factors. Regression equations expressing total PM emissions as function of blast pressure and abrasive feed rate were developed to estimate uncontrolled total PM emissions. The results of this study will be helpful in controlling emissions, developing emission inventories, developing best management practices, and selecting process parameters corresponding to minimum emissions for steel shot and grit.

Vehicles equipped with internal combustion engines are known as one of the most important Particulate Matters (PM) emissions sources. Many countries are aware of this issue and interested in employing more electric vehicles to reduce this emission. However, various past research claims that electric vehicles also emitted PM as conventional vehicles due to their non-exhaust emissions such as brake wear, tyre wear, road surface wear, and road dust resuspension. In addition, substantial evidence showed that there was indeed a positive correlation between the weight of vehicles and amounts of non-exhaust PM emissions. This study aims to measure on-road non-exhaust PM emissions from a hybrid electric vehicle during braking sequences. An onboard PM measuring device is attached to the side of the tested hybrid electric vehicle. PM measurements are monitored during the braking sequence in the electrified vehicle mode. Studies of increasing payloads that might affect the tendency of non-exhaust PM emissions are observed. The PM emission pattern during the braking sequence is captured by the current PM measuring setup as seen in the literature. The braking pattern (hard vs. soft brake) shows distinct amounts in PM emissions by a factor of two. Based on experimental data, it is found out that the additional payload of approximately 70 kg increases the amount of non-exhaust PM emissions by almost 20%.

Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV

Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV

In this work, airborne brake wear particulate matter (PM) emissions from a brake system were investigated by time-resolved and temperature-dependent measurement using a dynamometer. The measurement was performed for representative friction materials, 3 low-steel (LS) and 4 non-steel (NS), which are currently in worldwide use. The PM emission factor was found to be varied as large as by one order of magnitude depending on the composition of friction materials(pads). The airborne particle mass emissions from the LS materials ranged from 1.88 to 3.14 mg/km/vehicle, while the emissions from the NS ranged from 0.3 to 2.34 mg/km/vehicle, which is, in general, smaller than the LS. The time-resolved data imply that particle emissions in the extra-high-speed region of the WLTC cycle, where friction occurs at high temperature (Tdisk > 150 °C), is much higher than in the low-speed region, and determines the total PM mass emission factor. It was found that the friction materials containing metals such as Cu and Sn (LS-2/-3 and NS-4/-5) exhibited a lower PM emission factor. This result suggests that copper and tin, which forms an effective lubricating tribolayer in the interface between the pad and disk at high temperature, remarkably reduces PM emissions. It has been also found that the surface roughness of worn brake pads is positively proportional to PM emissions according to surface topography analysis, which is consistent with composition effect. These findings suggest that tribological engineering to provide sliding frictional behavior at elevated temperature is crucial to reducing PM emissions.

As many countries transition to electric vehicles (EVs) to reduce tailpipe emissions from internal combustion engine vehicles (ICEVs), both vehicle types continue to generate non-exhaust particulate matter (PM), including tire wear, brake wear, road surface wear, and particularly road dust resuspension. Among these, road dust resuspension is a major contributor to non-exhaust PM. While factors such as vehicle weight and drivetrain configuration have been extensively studied in fleet-level research, direct comparisons between ICEVs and EVs of the same model have not been explored. This study investigates the effects of drivetrain, vehicle weight, and payload on road dust resuspension emissions from ICEV and EV models. Two experimental approaches were employed: (1) acceleration from 0 to 60 km/h, and (2) a simulated real-world driving cycle (RDC). Each test was conducted under both light and heavy payload conditions. The results show that the EV consistently emitted more PM than the ICEV during both acceleration and RDC tests, based on factory-standard vehicle weights. Under identical vehicle weight conditions, the EV demonstrated higher PM resuspension levels, likely due to its higher torque and more immediate power delivery, which increases friction between the tires and the road, particularly during rapid acceleration. Both vehicle types exhibited significant increases in PM emissions under heavy payload conditions. These findings underscore the importance of addressing non-exhaust emissions from EVs, particularly road dust resuspension, and highlight the need for further research into mitigation strategies, such as vehicle lightweighting.

The lack of an available particulate matter (PM) PM2.5 emission factor for almond harvesting operations has become a challenge for particulate matter regulations and emissions inventory in California. Low-dust harvesters are viewed as one of the strategies to reduce PM emissions and help achieve the state’s PM2.5 attainment targets. This paper evaluates the potential emission reduction from using low-dust harvesters compared to the conventional. Orchard boundary measurements of PM concentrations were collected to back-calculate emission rates using inverse dispersion modeling. Emissions from four low-dust harvesters (Flory 850, Exact E3800, Weiss-McNair 9800 and Jack Rabbit) were compared to those from a conventional harvester (Flory 480) in two orchards, located in the Fresno County. Emissions of PM2.5, PM10 and total suspended particles were observed to be lower for all new harvesters compared to the conventional harvester. The range of reductions varies from about 40% to 77% in PM2.5 emissions based on emission factors generated. The average ratio of PM10 to PM2.5 emissions is about 12.5%. The results of these tests imply that these new low-dust harvesters are capable of reducing PM emissions without affecting product quality. Therefore, the San Joaquin Valley Air Pollution Control District should consider including the use of these new harvesters in the conservation management practices (CMP) for the reduction of PM emissions in the valley. Implications: The results of this research indicate that almond low-dust harvesters could potentially reduce PM emissions over traditional harvesters without any negative effect on product quality. Therefore, the use of these new harvesters should be considered as part of almond best management practices and updating of emissions inventory in the San Joaquin Valley.

Chapter 12 - Non-Exhaust PM Emissions From Battery Electric Vehicles

High resolution vehicular PM10 emissions over megacity Delhi: Relative contributions of exhaust and non-exhaust sources

On highways, it is commonplace to observe car-following behavior among vehicles. Unfortunately, this behavior results in significant particulate matter (PM) emissions, which greatly contribute to environmental pollution. Additionally, adverse weather conditions such as rain can negatively affect vehicles’ car-following behavior and have further influences on their PM emissions. The technology of connected automated vehicles (CAVs) offers a promising solution for mitigating these negative influences. This paper investigates the effect of various rainy weather conditions on PM emissions during car-following behavior on highways and proposes a CAV car-following strategy to reduce these emissions. Firstly, we employed a calibrated car-following model of traditional vehicles to perform simulation experiments, examining characteristics of PM emissions under four levels of rain and two simulation scenarios. Secondly, based on the relationship between PM emissions and speed fluctuations, we proposed a CAV car-following strategy by stabilizing traffic flow to smooth speed fluctuations. The proposed CAV car-following strategy was then validated through simulation experiments, and its effectiveness in reducing PM emissions under rainy conditions was assessed. The results indicate that higher speed fluctuations during car-following behavior lead to more PM emissions in rainy weather. By utilizing the proposed car-following strategy, CAVs can significantly reduce PM emissions in rain conditions, with average reductions of 41.07%, 59.46%, 49.60%, and 71.66% under very light rain, light rain, moderate rain, and heavy rain conditions, respectively. The findings of this paper facilitate the assessment of PM emissions fluctuations in different rainy weather conditions, which in turn can contribute to the development of more effective PM emissions control strategies. The proposed CAV car-following strategy can smooth speed fluctuations, and improve traffic flow stability, thus reducing PM emissions in rainy weather. It has the potential to mitigate environmental pollution from the transportation sector.

Abstract. Residential biomass combustion is a significant source of aerosol particles on regional and global scales influencing climate and human health. The main objective of the current study was to investigate the properties of cloud condensation nuclei (CCN) emitted from biomass burning of solid fuels in different cookstoves mostly of relevance to sub-Saharan east Africa. The traditional three-stone fire and a rocket stove were used for combustion of wood logs of Sesbania and Casuarina with birch used as a reference. A natural draft and a forced-draft pellet stove were used for combustion of pelletised Sesbania and pelletised Swedish softwood alone or in mixtures with pelletised coffee husk, rice husk or water hyacinth. The CCN activity and the effective density were measured for particles with mobility diameters of ∽65, ∽100 and ∽200 nm, respectively, and occasionally for 350 nm particles. Particle number size distributions were measured online with a fast particle analyser. The chemical composition of the fuel ash was measured by application of standard protocols. The average particle number size distributions were by number typically dominated by an ultrafine mode, and in most cases a soot mode was centred around a mobility diameter of ∽150 nm. The CCN activities decreased with increasing particle size for all experiments and ranged in terms of the hygroscopicity parameter, κ, from ∽0.1 to ∽0.8 for the ultrafine mode and from ∽0.001 to ∽0.15 for the soot mode. The CCN activity (κ) of the ultrafine mode increased (i) with increasing combustion temperature for a given fuel, and (ii) it typically increased with increasing potassium concentration in the investigated fuels. The primary CCN and the estimated particulate matter (PM) emission factors were typically found to increase significantly with increasing potassium concentration in the fuel for a given stove. In order to link CCN emission factors to PM emission factors, knowledge about stove technology, stove operation and the inorganic fuel ash composition is needed. This complicates the use of ambient PM levels alone for estimation of CCN concentrations in regions dominated by biomass combustion aerosol, with the relation turning even more complex when accounting for atmospheric ageing of the aerosol.