Toward Economically Efficient Carbon Reduction: Contrasting Greening Plastic Supply Chains with Alternative Energy Policy Approaches

Round 1

Reviewer 1 Report

This paper discusses the relative merits of various (recycling) schemes to reduce the carbon emissions from plastic production. It compares a number of schemes and plastic types with each other, as well as other decarbonization policies, such as encouraging renewable electricity or decarbonized transport.

The information in this paper has potential to be very valuable, since the authors have worked hard to collate information from various sources. It can serve as a valuable source for further work. I have a number of concerns about how this information is presented, which I would like to see addressed.

 

General comments:
- Main value of research paper seems to be collation of previous research as described in Table 2. This is very valuable. However, please provide more details on how the sources were compared, in case that their methodlogy may not be the same. For example, do we know whether the LCA parameters (e.g. whether to consider transport of materials, or which emission intensity was assumed for electricity) differ in sources 77-95?
- Figure 5 provides processed information, including rescaling values to lie between 0 and 100, and weighting of different factors. Can you provide a raw table with, for each plastic, the GWP, cost, quality and recyclability in raw values? It is not clear what unit is being used for each, and what value each plastic has. This would be very helpful for further research, and to little details is currently given to understand how the scores are created.
- The description of how Figure 5 is created is not clear. Please provide details as requested below.
- You provide a lot of detail on schemes unrelated to plastics, e.g. FIT and transport electrification. Is the reason to do this to compare their costs per kg CO2 removed to those from plastics? If so, please do this directly. For example, you could combine Figure 2 and the costs from Figure 3.
- Section 5 is not clear; the third paragraph is almost a page long and there is too much text. Can you distill a number of key messages into bullet points?
- The paper misses somewhat a discussion on the feasibility of recyling in temrs of materials. For example, if all plastic is recycled, is that enough to produce all the plastics required? Or can e.g. only 50% of plastics be recycled, meaning we could decarbonise at most 50% of production (assuming constant total production)?

- Please add a conversion of each currency to either dollars or yen: e.g. 31.55 USD (XX yen) per kilowatt hour. The rest of the paper is in yen; please translate all other values to also be in yen, to compare easily.
- "The impacts of retailer's revenue and cost sharing, and how they may affect a manufacturer's 127 efforts to reduce carbon emissions when both consumer environmental awareness and a carbon tax are present were 128 assessed, suggesting that the government should charge the highest carbon tax level under revenue sharing, a moderate 129 carbon tax under cost sharing, and the lowest carbon tax level under neither of the two schemes to increase the 130 manufacturer's incentive to reduce emissions [34]": it is not clear to me what "revenue sharing" and "cost sharing" are; can you make this clear and rephrase this sentence to explain more clearly?
- Figure 4: The x-axis is not clear. What is this showing? Is the deviation of assumed oil price to current oil price? Or something else?
- Figure 4: can you make the x-axis (y=0) more prominent? Maybe a darker black line? Currently is it not easy to see where each technology swaps from positive to negative value.
- Figure 5: this appears to be the main figure that summarises most of the paper. A few comments:
  - It is not clear to me how the scores (0-100) are created, for G, C, Q, R, G&C and Q&C are created. Please add bullet points for each category. For example, for G, do you take the carbon emissions, rescale to lie between 0 and 100 (via (value - min) / (max - min))? How about the others?
  - Wih the current setup, it is easy to compare HDPE, PC, ABS, POM, PP and PMMA with each other. Is this what we want? In my mind, what we want to see is how virgin v R10 v R20 v R50 v Bio compare, correct? Does it make sense to have one color for each of these, with HDPE, PC, etc. as points along the circumfrence? Then we can easily compare how e.g. Virgin compares to Bio on all the dimensions.
  - The weightings are a bit arbitrary (50/16.7/16.7/16.7). Is there a reason not to have just four (G,C,Q,R), each with 100% weighting? This simplifies the plot (four categories instead of 7). This makes the plot simpler, and allows users to create their own weighting. Right now, it's not clear the relative rankings for e.g. G, as it contains 0% of GWP but 50% of other contributions.
- Section 6 (Patents): why is this section called "patents"? Is it different from a standard "conclusions" section?

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Title: Toward Economically Efficient Carbon Reduction: Contrasting Greening Plastic Supply Chains with Alternative Energy Policy Approaches. The paper is significant work, as it deals with a timely problem.

Overall, the title, abstract, and keywords give the readers a good idea of the paper.

Subsections have to be numerous, for example, 2.1 Feed in Tariffs and Premiums.

The year in line 156 is missing.

The methodology applied in the study is adequate to answer the research question.

The Discussion emphasizes the contribution to understanding the reallocation of subsidies from less effective carbon reduction policies toward supply chain greening. The conclusion is presented in the same section as the Discussion and should be polished.

Data is available on request due to restrictions. In section 6, named Patent, technical information about the invention must be disclosed to the public.

There are some errors in your reference list. Please check and fix it. The first reference needs the exact DOI as doi:10.2866/982743, or the second reference regular cite such as CO2 Emissions in 2022, IEA 2023, Paris. Available online: https://www.iea.org/reports/co2-emissions-in-2022 (accessed on Day Month Year).

or

CO₂ and Greenhouse Gas Emissions: CO₂ emissions. Our World in Data 2020. Available online: https://ourworldindata.org/co2-and-greenhouse-gas-emissions (accessed on Day Month Year).

or

Japan Buys Its Way to Kyoto Success. Nikkei Asia 2014. Available online: https://asia.nikkei.com/NAR/Articles/Japan-buys-its-way-to-Kyoto-success3 (accessed on Day Month Year).

or

Japan’s Plastic Waste Management – Challenges and Potential Solutions. Institute for Global Environmental Strategies Plastic Atlas Asia 2022. Available online: https://www.iges.or.jp/en/publication_documents/pub/reportchapter/en/12341/PlasticAtlasAsia2022_en_WEB_1.pdf (accessed on Day Month Year).

or

An Introduction to Plastic Recycling 2022. Plastic Waste Management Institute 2022. Available online: https://www.pwmi.or.jp/ei/plastic_recycling_2022.pdf (accessed on Day Month Year).

Certain links in references are not accessible.

After minor corrections, the paper recommends for publication in Sustainability.

A thorough editorial check and English improvement are needed. Please kindly proofread the entire manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Paper's Objective:

This study seeks to identify the economic and carbon reduction potential of the greening of plastic supply chains com-13 pared to existing carbon reduction regimes.

We assessed this study and there is our review report as follows:

1. The abstract must be edit according this methodology:

- Backround (2lines)/ Aim ( 2lines)/ Method used (2 lines)/ Findings ( 3 lines)/ Original value of this study and implication policy.

- 4.5% of global emissions:  this percentage is according to any reference?

2. Introduction: decompose in clair and coherent paragraphs (5 lines max / parapgraph). Edit all the text with this fomat. 

3. Literature review: 

* Recent research papers can provide more quality to this study: You can check thoses databases e.i. Sustainbaility MDPI, Energy, Economie; Springer Nature, Elsevier, Sage and Emerald journals).

4. Research hypotheses : Missed?

5. Methodology used : The methodology of this study consists of three parts.

 - Carbon Reduction Regimes for Japan ( Table 1)

- Plastic Types and Environmental and Economic Analysis 

-  GWP, quality and recyclability

All those recycling regimes must be analyzed according empirical models. Also, you must provide cited reference for all thoses regimes. Your study missed this important and significant models.

6 . Findings: Very poor results. Authors must conducte empircal analysis and provide thoses results as follow:

* Existing and Under Consideration Carbon Reduction Regime Costs 

* Plastic LCA and Economic and Environmental Assessment of CO2 Reduction Options

* Multicriteria Analysis for Plastic Selection

7. Limitations section: is missed?

8.  Discussion section : Edit this section with the new empirical results.

9. Conclusion and recomandations : is missed this section

10 References: all cited reference must join the DOI.

-

Revise in clear way and prepare your empirical analysis with your reaserch hypotheses.

Good luck

 

 

 

 

Moderate Editing English language is required.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thanks for addressing my comments; I think this has been done to a good degree. I have a few last concerns. Other than that, I think the authors have made all the changes I would recommend.

- "Main value of research paper...": thanks for adding these details, but they are a bit
- "Figure 5 provides...": the table in the Appendix is very useful, thanks for adding it. I have two comments on it:
  - Since these are not your own calculated values, please add a source to each one indicating where it came from, as in Table 2.
  - Can you explain the ways of calculating the "quality" and "recyclability" scores? These are described somewhat in lines 250-257, but the actual formula for the score I could not find.
- "You provide a lot...": thanks for explaining this; I had indeed seen this incorrectly. Thanks for clarifying.
- "Figure 4: the x-axis": The dark line makes things more clear. I'm still a bit unsure what "Oil price sentitivity for Virgin Plastic" means; does it mean e.g. "pct increase in oil price used for virgin plastics over base value?" if so, can you write this in the plot?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Is our point of view : After the 1st peer-review round

This study can be more significant if authors used empirical model to mesure the statistical real impact  of the Greening Plastic Supply Chains to the reduction of the CO2.

But it is just a simple comparative study,  'as the authors mentioned in the revised responses'.

Spelling to check along the text.

Author Response

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Author Response File: Author Response.pdf