the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Nov 2024
Measurement report: Insight into Greenhouse Gas Emission Characteristics of Light-Duty Vehicles in China Driven by Technological Innovation
Abstract. Greenhouse gas (GHG) emissions represent a pivotal driver of global climate change, with vehicular emissions, particularly from light-duty vehicles, emerging as a prominent source of GHGs. Despite extensive research on gaseous pollutants, studies on GHG emissions within the framework of carbon neutrality remain scarce. This study delves into the emission characteristics of three primary GHGs (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) from various light-duty vehicles, encompassing conventional gasoline and hybrid vehicles, and bi-fuel taxis. As anticipated, with advancements in emission standards and powertrains, vehicular GHG emissions have significantly decreased. However, our findings also revealed surprising trends. While engine technology upgrades reduced CO2, they unexpectedly increased CH4 and N2O emissions. Additionally, hot starts, beneficial for reducing CO2 and CH4 emissions, caused heightened N2O emissions, which is noteworthy under operating conditions with frequent start-stop events. Intriguingly, compressed natural gas (CNG), generally perceived as cleaner, increased CH4 emissions. Regarding the impact of Three-Way Catalysts (TWC) on GHG emissions, under “TWC failed” conditions, N2O emissions from CNG-powered vehicles were approximately three times higher than those under “TWC worked” conditions, attributed to the significant increase in NOx. Considering the global warming potential (GWP), the "TWC failure" scenario paradoxically decreased GWP values, highlighting the complex interaction between emission control technologies and their environmental impacts. This study provides crucial insights into vehicular GHG emissions, which are essential for developing effective strategies aimed at mitigating emissions and enhancing the efficiency of emission control systems.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(829 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-3095', Anonymous Referee #1, 29 Dec 2024
With the upcoming China-7 regulation is including GHG as a new creteria for the control of new vehicle emissions, this research presents good innovation and solid scientific basis, and its findings makes important contributions to addressing the gap in GHG emission factors for motor vehicles in China. Additionally, this study provides valuable data to support the estimation of total greenhouse gas emissions in the country. I recommend acceptance minor revisions. Some issues listed below need futher take-of-care.
1. It is recommended that the authors add a comparison of this study’s results with previously reported findings. For instance, incorporating a table that summarizes some of the published results would provide readers with a more intuitive understanding of GHG emissions from vehicles.
2. Line 75-76 "vehicular g GHG emissions" seems to be a writing error.
3. In this study, the vehicle with high mileage was labeled as “TWC failed”. I am contemplating whether it would be renamed as "TWC deteriorated" vehicle, as the study did not intentionally disable the TWC through removal or tampering but rather defined them based on their high mileage and correspondingly high emissions of conventional pollutants. Therefore, I suggest describing this high-mileage vehicle as "TWC deteriorated" rather than "TWC failed".
4. Why is some of the information for vehicle #3 missing in Table 1? It is advisable to include descriptions of the reasons for missing data in the notes.
5. Line 141. The GWP values of N2O and CH4 are not provided in the formula.
6. The values in the article should retain the same significant figures, for example, the significant figures of the CO2 emission factor and CH4 emission factor in line 165 need to be unified.
7. Despite the sufficient number of vehicles tested for the overall analysis in this study, the principles for selecting these vehicles were not clearly elaborated in Chapter 2.Citation: https://doi.org/10.5194/egusphere-2024-3095-RC1 - AC1: 'Reply on RC1', Yunjing Wang, 21 Apr 2025
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RC2: 'Comment on egusphere-2024-3095', Yan Liu, 02 Apr 2025
General comments:
This manuscript presents a comprehensive investigation into the characteristics of greenhouse gas (GHG) emissions from motor vehicles under various influencing factors, including emission standards, TWC operational status, cold/hot start modes, and power-train types. The study elucidates the evolving trends of GHG emissions during technological upgrades, providing critical data support for constructing GHG emission inventories while offering scientific basis for emission control strategies.
Focusing on the current research landscape where vehicular pollutant emissions have been extensively studied but GHG emissions remain under-investigated, this work makes significant contributions to complementing existing knowledge on vehicular emission characteristics. Particularly within the context of future carbon peak and neutrality goals, the findings provide crucial insights from the mobile source perspective to support continuous improvement of air quality.
However, the following comments should be addressed before this manuscript can be accepted. The English writing of this work should also be improved. As a result, I recommend a minor revision of this manuscript.
Specific comments:
- Introduction: In the third paragraph, please reorganize the research processes and results from the published papers. The current presentation merely lists the findings of individual studies without integrating them. Additionally, the authors have not explicitly identified the limitations in the existing research.
- Introduction: In the background section, succinctly summarize why it is important to test hybrid vehicle exhaust greenhouse gas emissions. Describe the unique characteristics of hybrid vehicle exhaust emissions and discuss the effects of post-treatment technologies on exhaust emissions in vehicles.
- Line 100-105: How was the determination made that the TWC failed? Does a mileage of approximately 27 km necessarily indicate failure? Are the authors referring to TWC degradation here?
- Introduction: Based on the latest 2023 data, provide an overview of the passenger vehicle ownership growth trends in China.
- Section 2: To provide a more intuitive representation of the experimental process, it is recommended that the authors include a schematic diagram of the experiment.
- Section 3.2: What is the ethanol content in Chinese gasoline? How does the ethanol content affect greenhouse gas emissions from vehicle exhaust?
- Line 315-320: The authors only mention that hybrid vehicles exhibit higher combustion efficiency but provide no experimental data to support this claim. If relevant data is available, please conduct a quantitative comparison between the combustion efficiency of hybrid vehicles and conventional fuel-powered vehicles.
Citation: https://doi.org/10.5194/egusphere-2024-3095-RC2 - AC2: 'Reply on RC2', Yunjing Wang, 21 Apr 2025
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-3095', Anonymous Referee #1, 29 Dec 2024
With the upcoming China-7 regulation is including GHG as a new creteria for the control of new vehicle emissions, this research presents good innovation and solid scientific basis, and its findings makes important contributions to addressing the gap in GHG emission factors for motor vehicles in China. Additionally, this study provides valuable data to support the estimation of total greenhouse gas emissions in the country. I recommend acceptance minor revisions. Some issues listed below need futher take-of-care.
1. It is recommended that the authors add a comparison of this study’s results with previously reported findings. For instance, incorporating a table that summarizes some of the published results would provide readers with a more intuitive understanding of GHG emissions from vehicles.
2. Line 75-76 "vehicular g GHG emissions" seems to be a writing error.
3. In this study, the vehicle with high mileage was labeled as “TWC failed”. I am contemplating whether it would be renamed as "TWC deteriorated" vehicle, as the study did not intentionally disable the TWC through removal or tampering but rather defined them based on their high mileage and correspondingly high emissions of conventional pollutants. Therefore, I suggest describing this high-mileage vehicle as "TWC deteriorated" rather than "TWC failed".
4. Why is some of the information for vehicle #3 missing in Table 1? It is advisable to include descriptions of the reasons for missing data in the notes.
5. Line 141. The GWP values of N2O and CH4 are not provided in the formula.
6. The values in the article should retain the same significant figures, for example, the significant figures of the CO2 emission factor and CH4 emission factor in line 165 need to be unified.
7. Despite the sufficient number of vehicles tested for the overall analysis in this study, the principles for selecting these vehicles were not clearly elaborated in Chapter 2.Citation: https://doi.org/10.5194/egusphere-2024-3095-RC1 - AC1: 'Reply on RC1', Yunjing Wang, 21 Apr 2025
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RC2: 'Comment on egusphere-2024-3095', Yan Liu, 02 Apr 2025
General comments:
This manuscript presents a comprehensive investigation into the characteristics of greenhouse gas (GHG) emissions from motor vehicles under various influencing factors, including emission standards, TWC operational status, cold/hot start modes, and power-train types. The study elucidates the evolving trends of GHG emissions during technological upgrades, providing critical data support for constructing GHG emission inventories while offering scientific basis for emission control strategies.
Focusing on the current research landscape where vehicular pollutant emissions have been extensively studied but GHG emissions remain under-investigated, this work makes significant contributions to complementing existing knowledge on vehicular emission characteristics. Particularly within the context of future carbon peak and neutrality goals, the findings provide crucial insights from the mobile source perspective to support continuous improvement of air quality.
However, the following comments should be addressed before this manuscript can be accepted. The English writing of this work should also be improved. As a result, I recommend a minor revision of this manuscript.
Specific comments:
- Introduction: In the third paragraph, please reorganize the research processes and results from the published papers. The current presentation merely lists the findings of individual studies without integrating them. Additionally, the authors have not explicitly identified the limitations in the existing research.
- Introduction: In the background section, succinctly summarize why it is important to test hybrid vehicle exhaust greenhouse gas emissions. Describe the unique characteristics of hybrid vehicle exhaust emissions and discuss the effects of post-treatment technologies on exhaust emissions in vehicles.
- Line 100-105: How was the determination made that the TWC failed? Does a mileage of approximately 27 km necessarily indicate failure? Are the authors referring to TWC degradation here?
- Introduction: Based on the latest 2023 data, provide an overview of the passenger vehicle ownership growth trends in China.
- Section 2: To provide a more intuitive representation of the experimental process, it is recommended that the authors include a schematic diagram of the experiment.
- Section 3.2: What is the ethanol content in Chinese gasoline? How does the ethanol content affect greenhouse gas emissions from vehicle exhaust?
- Line 315-320: The authors only mention that hybrid vehicles exhibit higher combustion efficiency but provide no experimental data to support this claim. If relevant data is available, please conduct a quantitative comparison between the combustion efficiency of hybrid vehicles and conventional fuel-powered vehicles.
Citation: https://doi.org/10.5194/egusphere-2024-3095-RC2 - AC2: 'Reply on RC2', Yunjing Wang, 21 Apr 2025
Peer review completion
Journal article(s) based on this preprint
Data sets
Insight into Greenhouse Gas Emission Characteristics of Light-Duty Vehicles in China Driven by Technological Innovation X. Yang et al. https://doi.org/10.6084/m9.figshare.27303969
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Yunjing Wang
Songdi Liao
Hang Yin
Yan Ding
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(829 KB) - Metadata XML