Assessing the GHG Emissions and Savings during the Recycling of NMC Lithium-Ion Batteries Used in Electric Vehicles in China
Round 1
Reviewer 1 Report
The manuscript presents a topic on quantifying GHG emissions and savings during the recycling of a type of lithium-ion battery used in electric vehicles. It can be of great interest to readers especially given the agendas of carbon neutrality. A significant and essential part of this study is the modeling and the data collected from other sources, which determines whether the conclusions are valid and adequately supported. The limitations of the study are of my concern and should be stated. Below the detailed comments are listed.
- The title should be revised, to be much more specific and relevant to the study. For example - Assessing the GHG emissions and savings during the recycling of NMC lithium-ion batteries used in electric vehicles…
- Abstract – more detailed results should be given in the abstract.
- What is the state of the art of this area, i.e. using models and data to measure GHG during battery (or other secondary metal resources) recycling? Are there any other studies that can be discussed in introduction? What model did they use? What limitations do they present?
- Many wordings and particular terms are confusing and not specific. Such as:
- Power battery – does that mean lithium-ion battery used to power vehicles? Then use “lithium-ion battery”.
- New energy vehicle –Use “electric vehicles” if that’s what you meant.
- The authors should pay attention to the appropriate use of terms used to describe battery recycling activities. They are but not limited to: remanufacturing (e.g. line 47, page 2), pre-treatment (Figure 2), pre-processing (process) (e.g. line 164, page 4), recovery/recovery utilization.
- 6 in Section 3.2.1 – what if the vehicles used to transport LIBs are also electric vehicles?
- Line 217, Eq 10 – missing r(a)?
Have you considered the difference in life span between the LIBs put into cascade utilization and brand-new battery?
- Tables should be checked in format.
- The model, data, and conclusions presented in this study have lots of limitations, which are already briefly mentioned in the Conclusion section. However, the reviewer suggests putting them in 5.3 Discussion in a much more detailed manner.
- The study greatly relies on data from other sources, i.e. a battery recycler in China and some published journal papers. Instead of just putting a reference number, the authors are suggested to present more details that can validate the data. For example, how the data were calculated, what they represent, what conditions used to generate them? These may be mentioned in the Introduction or Section 4.
Author Response
Thank you for your sincere advice. I have made many modifications in the paper to deal with the problems you mentioned.
Point 1: The title should be revised, to be much more specific and relevant to the study. For example - Assessing the GHG emissions and savings during the recycling of NMC lithium-ion batteries used in electric vehicles…
Response 1: According to your suggestion, we have changed the title to Assessing the GHG emissions and savings during the recycling of NMC lithium-ion batteries used in electric vehicles in China. It can be seen from lines 2 to 3 of the article.
Point 2: Abstract – more detailed results should be given in the abstract.
Response 2: We have revised the abstract and analyzed the results of the paper from three aspects. It can be seen from lines 22 to 27 in the text.
Point 3: What is the state of the art of this area, i.e. using models and data to measure GHG during battery (or other secondary metal resources) recycling? Are there any other studies that can be discussed in introduction? What model did they use? What limitations do they present?
Response 3: In order to describe the latest art of this area in detail, we have added some literature to describe the latest research progress in section 1. This can be seen in lines 58 to 85 of the text.
Point 4: Many wordings and particular terms are confusing and not specific. Such as:
Power battery – does that mean lithium-ion battery used to power vehicles? Then use “lithium-ion battery”.
New energy vehicle –Use “electric vehicles” if that’s what you meant.
The authors should pay attention to the appropriate use of terms used to describe battery recycling activities. They are but not limited to: remanufacturing (e.g. line 47, page 2), pre-treatment (Figure 2), pre-processing (process) (e.g. line 164, page 4), recovery/recovery utilization.
Response 4: We modified some terms in the article to make the terms more accurate, for example, "power battery" was changed into "lithium ion battery", and "new energy vehicle" was changed into "electric vehicle".
We also describe the process of lithium-ion battery recycling in more detail, which can be seen from lines 130 to 144 in Section 3.1. At the same time, we changed some of the language, such as "pre-processing" to "pre-treatment" (line 201 on page 5).
Point 5: 6 in Section 3.2.1 – what if the vehicles used to transport LIBs are also electric vehicles?
Response 5: This problem is explained in line 186 to 189 of section 3.2.1. As EVs have little impact on the environment during the stage of transportation, it is not con-sidered in this paper. The type of vehicles transporting lithium batteries listed in the following is petrol vehicles.
Point 6: Line 217, Eq 10 – missing r(a)?
Have you considered the difference in life span between the LIBs put into cascade utilization and brand-new battery?
Response 6: We added r(a) to the description after formula (10) on line 234.
In the meantime, we explained the difference between the LIBs put into cascade utilization and brand-new battery in line 141 to 143 of section 3.1. According to the standard of remanufactured products, the remanufactured battery product’s life span is required to be same as the brand-new battery’s.
Point 7: Tables should be checked in format.
Response 7: To address this problem, we have modified the format of Table 1 and Table 8 in the paper.
Point 8: The model, data, and conclusions presented in this study have lots of limitations, which are already briefly mentioned in the Conclusion section. However, the reviewer suggests putting them in 5.3 Discussion in a much more detailed manner.
Response 8: In Section 5.3, we have made a more specific analysis of the limitations of the paper from three aspects. This can be seen in lines 367 through 377.
Point 9: The study greatly relies on data from other sources, i.e. a battery recycler in China and some published journal papers. Instead of just putting a reference number, the authors are suggested to present more details that can validate the data. For example, how the data were calculated, what they represent, what conditions used to generate them? These may be mentioned in the Introduction or Section 4.
Response 9: In Section 4.1, we have added a more specific description of the data sources in this paper. This can be seen in lines 249 to 259.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper has a well-organized structure, the research design is appropriate. The aim and research gap are clear, the practical implication is justified. The figures and Tables are adequate for the paper. Overall the manuscript is well written. However, the study has two weaknesses. Firstly, the methodological background of the model developed by the author is not clear from the text of the paper. Secondly, the model has not received proper discussion in the light of existing approaches.
Author Response
Thank you for your sincere advice. I have made a few modifications in the paper to deal with the problems you mentioned.
Point 1: Firstly, the methodological background of the model developed by the author is not clear from the text of the paper.
Response 1: As for that, we have added a literature to describe the methodological background of the model developed in this paper in lines 78 to 85 of section 1.
Point 2: Secondly, the model has not received proper discussion in the light of existing approaches.
Response 2: In section 3.1, we have added a discussion of three methods used to measure carbon emissions. This can be seen in lines 147 through 154.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
None
Author Response
Thank you for your sincere advice.
