Assessing the Techno-Economic Feasibility of Waste Electric and Electronic Equipment Treatment Plant: A Multi-Decisional Modeling Approach

Round 1

Reviewer 1 Report

In this study, the authors assessed the techno-economic feasibility of a waste electrical and electronic equipment treatment facility: a multi-decision modeling approach.

The introduction provides sufficient background and include all relevant references and all the references listed are relevant to the research. The research design is appropriate and the methods are adequately described. The manuscript can accepted for publication with minor revisions.  Here are several comments need the authors attention. This paper can be accepted after the authors further clarify some  issues in the paper that reader can easily understand it.

1. The authors have obtained a large amount of data but the analysis is very superficial and the authors are advised to analyse and discuss it in the context of the literature.

2. The methodology is well, but we do not have enough information about the electronic waste treatment plant. I suggest to give a technological scheme so that the readers have an insight into the processing process.

3. Also, the basic processing parameters on which the economic analysis was later based are missing.

4. The conclusions are not supported by the results. The chapter on conclusions requires reformulation. Additionally, attention should be paid to the results included in the paper.

 I suggest that the paper be accepted with minor revision.

Author Response

Reviewer 1

In this study, the authors assessed the techno-economic feasibility of a waste electrical and electronic equipment treatment facility: a multi-decision modeling approach.

The introduction provides sufficient background and include all relevant references and all the references listed are relevant to the research. The research design is appropriate and the methods are adequately described. The manuscript can accepted for publication with minor revisions.  Here are several comments need the authors attention. This paper can be accepted after the authors further clarify some  issues in the paper that reader can easily understand it.

1. The authors have obtained a large amount of data but the analysis is very superficial and the authors are advised to analyse and discuss it in the context of the literature.

Response: We thoroughly revised our manuscript considering all reviewer comments. In particular, we improved the analysis and discussed more in detail the results, critically comparing our outcomes with the scientific literature.

2. The methodology is well, but we do not have enough information about the electronic waste treatment plant. I suggest to give a technological scheme so that the readers have an insight into the processing process.

Response: The technological scheme of the WEEE treatment plant is already reported in Fig. 3. However, we improved the explanation in the text, to give a deeper insight to the reader as well as the clarity of the figure. We hope that now the process scheme is more comprehensible.

3. Also, the basic processing parameters on which the economic analysis was later based are missing.

Response: The section related to the description of the conducted economic analysis has been revised, providing more information about how capital and operating costs were calculated. In addition, some considerations about the calculation of plant revenues were added as well. More references regarding the catalogues utilized as data source for the processing parameters have been reported.

4. The conclusions are not supported by the results. The chapter on conclusions requires reformulation. Additionally, attention should be paid to the results included in the paper.

Response: We revised the results section improving the discussion and giving a critical perspective on the obtained outcomes. The conclusions were revised as well to provide a clear insight to the reader, summarizing the most important results and their usefulness for a wide scientific audience.

 I suggest that the paper be accepted with minor revision.

Author Response File: Author Response.docx

Reviewer 2 Report

1. For MCDA, other factors including social assessment could have been included where different classes in society can acquire or dispose E-waste. Currently authors only conducted economic analysis which did not include societal aspects. How do you justify it? 
2. Fig 4 should be rescaled using scientific notations. E07 E08 should be replaced with 10X7 for wider readership and understanding of the article. 
3. Case studies should be mentioned in abstract which can give clear sight of the study. 

English language can be improved. 

Author Response

Reviewer 2

1. For MCDA, other factors including social assessment could have been included where different classes in society can acquire or dispose E-waste. Currently authors only conducted economic analysis which did not include societal aspects. How do you justify it?

Response: We agree that social aspects are important as the economic and environmental indicators. In the specific case, it was not possible to conduct a social assessment, but we wish to deepen the present study with the addition of social indicators in the future. Anyway, the economic and environmental aspects, to our perspective, are sufficient to preliminary evaluate the financial and environmental sustainability of the WEEE treatment plant. According to (Anandh et al., 2021), the social aspects of WEEE flow focus on consumer awareness and behaviour in storing the used EEE, return practices or participation in product take-back, and the consumption behaviour/service lifetime. Our study focuses on the treatment side, so what happens to WEEE prior to its treatment is beyond the scope of our work, as are the social aspects involving consumers.

References:

Anandh, G., PrasannaVenkatesan, S., Goh, M., Mathiyazhagan, K., 2021. Reuse assessment of WEEE: Systematic review of emerging themes and research directions. J. Environ. Manage. 287, 112335. https://doi.org/10.1016/j.jenvman.2021.112335

Fig 4 should be rescaled using scientific notations. E07 E08 should be replaced with 10X7 for wider readership and understanding of the article.

Response: The software utilized for the production of this image does not allow for the suggested modification. However, the authors believe (and would like to reassure the kind reviewer), that the readiness and understanding of the article will not be penalized, since this kind of notation has been already utilized in highly cited papers (https://doi.org/10.1016/j.energy.2019.03.104, https://doi.org/10.3390/en13184780).

2. Case studies should be mentioned in abstract which can give clear sight of the study.

Response: The abstract was revised to clearly define the scope of the study, the main results and the applicability to a wide scientific audience.

Author Response File: Author Response.docx

Reviewer 3 Report

Introduction: Begin by briefly explaining the increasing global concerns about waste management and the specific challenges associated with WEEE. Objective Statement: Clearly state the main objective of your work. 

Parameter Definitions: Define and explain the meaningful economic and environmental parameters used in your assessment. 

Market Analysis: Offer a brief overview of the current WEEE market, including its production and composition in the Friuli-Venezia Giulia Region.

Discussion: Provide a detailed discussion of the results, focusing on the variations in plant investment costs, pay-back time, and recovery rates under different economic conditions. Explain the implications of these variations.

Conclusion: Summarize the main findings of your study, emphasizing the feasibility and sustainability of establishing a local WEEE treatment plant.

References: Ensure proper citation of sources and references throughout the text.

Clarity and Conciseness: Review the text for clarity and conciseness. 

Some issues：

-What are the specific environmental and economic impacts of exporting waste electric and electronic equipment (WEEE) out of the Friuli-Venezia Giulia Region, and how do these impacts compare to the potential establishment of a local treatment plant?

-How can multi-objective engineering optimization and decision support systems (DSS) be applied to address the growing challenges associated with WEEE management and sustainability?

-What are the key parameters that drive the feasibility and cost-effectiveness of establishing a WEEE treatment plant, and how do these parameters change under different scenarios and market conditions?

-What is the projected growth in WEEE production and composition in the future market, and how does this impact the cost and benefits of local treatment?

-How do the pay-back time and investment costs of a WEEE treatment plant vary based on changing economic conditions, such as fluctuating conferral fees and subsidies for recovered materials?

-What are the critical considerations and legal requirements for the fraction of recovered materials, and how do they align with current EU legislative standards?

-What are the potential reductions in CO2 emissions that can be achieved by recovering materials from treated WEEE, and how do these reductions contribute to sustainability goals?

-How transferable is the developed DSS system to other regions, and what innovative resource recovery techniques and process details can be integrated to further improve environmental and economic sustainability?

Moderate editing of English language required.

Author Response

Reviewer 3

Introduction: Begin by briefly explaining the increasing global concerns about waste management and the specific challenges associated with WEEE. Objective Statement: Clearly state the main objective of your work.

Response: Thanks for your valuable comments. We thoroughly revised the introduction, beginning with some global consideration regarding waste management and then focusing on WEEE. We tried to better depict the state-of-the-art of WEEE management and the critical aspects; finally, we better stated the main aim of the work.

Parameter Definitions: Define and explain the meaningful economic and environmental parameters used in your assessment.

Response: We revised materials and methods to provide a clearer overview of the economic and environmental parameters used in the model, explaining how they were calculated and which were the main assumptions.

Market Analysis: Offer a brief overview of the current WEEE market, including its production and composition in the Friuli-Venezia Giulia Region.

Response: Current WEEE market in Friuli-Venezia Giulia, including its production and composition, was already reported in Table 3, in terms of waste shares (expressed through European Waste Catalogue EWC codes) divided for each province of the region. However, some more references to the current Italian situation were made throughout the text, considering the most recent available report (dated 2022). Also, we discussed more in detail the current situation in the region, speculating about possible market evolution.

Discussion: Provide a detailed discussion of the results, focusing on the variations in plant investment costs, pay-back time, and recovery rates under different economic conditions. Explain the implications of these variations.

Response: We improved the discussion regarding how the economic parameters are affected by a variation in the market conditions. Also, we improved the discussion in the text regarding the overall plant sustainability for different potentialities in terms of treated WEEE.

Conclusion: Summarize the main findings of your study, emphasizing the feasibility and sustainability of establishing a local WEEE treatment plant.

Response: Again, we thoroughly revised the Conclusions section, focusing on the key results to be delivered to the reader, including not only the techno-economic and environmental sustainability of the plant, but also on the general applicability of the developed DSS. We gave some critical perspective to the reader to further improve the quality of the section.

References: Ensure proper citation of sources and references throughout the text.

Response: We added more relevant citations throughout the text to better describe the state-of-the-art of WEEE management in the scientific literature.

Clarity and Conciseness: Review the text for clarity and conciseness.

Response: We agree with this comment. We shortened the most descriptive sections, especially the materials and methods, and we added more detailed and quantitative data to improve the overall quality of the work.

Some issues：

-What are the specific environmental and economic impacts of exporting waste electric and electronic equipment (WEEE) out of the Friuli-Venezia Giulia Region, and how do these impacts compare to the potential establishment of a local treatment plant?

Response: The negative impacts are mainly related to the transportation of the material outside the region, with the associated costs and emissions, while the main advantage in building a local WEEE treatment plant is related to the possibility to achieve circular economy in the sector within the region. However, considering that a plant treating only the amount of locally produced WEEE is not financially sustainable, proper incentives must be given, or, in alternative, a higher potentiality must be supposed.

-How can multi-objective engineering optimization and decision support systems (DSS) be applied to address the growing challenges associated with WEEE management and sustainability?

Response: This is a key point. When considering the realization of plants like waste treatment plants, the project performances cover several aspects, so different and often conflicting objective functions are taken into account. Multi-objective engineering optimizations allows for accounting different and conflicting objectives: in the specific case-study, the economic sustainability is linked to favorable market conditions and the treatment of fractions with high conferral costs, while the environmental sustainability is connected to an increase in the amount of recovered materials and the CO2 emission reduction.

-What are the key parameters that drive the feasibility and cost-effectiveness of establishing a WEEE treatment plant, and how do these parameters change under different scenarios and market conditions?

Response: The financial sustainability of the plant is mainly related to the market conditions for conferral fees of the input WEEE, on one hand, and for the economic subsidies provided for the recovered materials, on the other hand. These aspects are strongly affecting the overall plant cost-effectiveness, as better detailed in the revised manuscript.

-What is the projected growth in WEEE production and composition in the future market, and how does this impact the cost and benefits of local treatment?

Response: Currently, a stable WEEE production has been observed in the last few years, both in Friuli-Venezia Giulia region and more generally in Italy. A slow increase in the total WEEE amounts to be treated can be expected in the next years, to improve the overall situation concerning recycling ratios, which are still low when compared to current EU legislation thresholds. This observation has been added throughout the discussion in the revised manuscript

-How do the pay-back time and investment costs of a WEEE treatment plant vary based on changing economic conditions, such as fluctuating conferral fees and subsidies for recovered materials?

Response: The financial sustainability of the plant is mainly related to the market conditions for conferral fees of the input WEEE, on one hand, and for the economic subsidies provided for the recovered materials, on the other hand. These aspects are strongly affecting the overall plant cost-effectiveness. The effects that these parameters have on the economic objective function are already reported in Figure 6, in terms of variation of Pay-Back time. For clarity sake and to facilitate the interpretation of the figure, a more detailed description of the charts has been added in the text

-What are the critical considerations and legal requirements for the fraction of recovered materials, and how do they align with current EU legislative standards?

Response: It is required that 80% of the material in WEEE should be recovered. An interesting point is that the different WEEE fractions show a lower or higher fraction of materials that can be recovered: e.g., PCs normally show a lower resource recovery possibility than other fractions, such as fridges or washing machines. This observation has been added to the results and discussion to improve the overall quality of the work, providing useful insight to the reader.

-What are the potential reductions in CO2 emissions that can be achieved by recovering materials from treated WEEE, and how do these reductions contribute to sustainability goals?

Response: The CO2 reduction considered in the present work is related to the recovery of valuable materials, that substitute analogous amounts of materials from primary sources. This can establish local circular economies and contribute to the overall sustainability of the production chains.

-How transferable is the developed DSS system to other regions, and what innovative resource recovery techniques and process details can be integrated to further improve environmental and economic sustainability?

Response: We tried to focus more on this aspect in the manuscript revision. The proposed DSS can be exported to any location to preliminary evaluate the techno-economic sustainability of installing a WEEE treatment plant, if the proper boundary conditions (plant potentiality, economic market conditions, specific WEEE composition) are specified. The most important process detail that could be added to improve the model is the incineration of the non-recoverable fractions, such as mixed plastics and wood; we added this consideration throughout the manuscript for better comprehension. Moreover, the developed model is highly flexible and applicative, and can be tailored to different locations and scenarios by simply modifying the input parameters and the boundary market conditions.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The abstract and conclusion of the paper need to be further condensed to highlight the innovative points of the paper.

The References in the introduction section are not systematically cited, and it is necessary to summarize and highlight the lack and shortcomings of literature work, in order to introduce the research significance of this article.

Author Response

Dear editor and reviewers, thanks for your kind comments that allowed us to improve the quality of the manuscript. We tried to thoroughly address all the comments and modify the manuscript accordingly. In this file, you can find the detailed response to each comment.

Reviewer 3

The abstract and conclusion of the paper need to be further condensed to highlight the innovative points of the paper.

Response: We further condensed the abstract and the conclusions, better highlighting the most relevant aspects to be delivered to the reader. However, we believe that both sections are already concise and clear after the previous thorough revision.

The References in the introduction section are not systematically cited, and it is necessary to summarize and highlight the lack and shortcomings of literature work, in order to introduce the research significance of this article.

Response: We tried to better highlight the novelty of the present work compared to the existing literature in the last part of the Introduction section. However, we already improved the references in the first revision by adding more papers and clearly depicting the general literature framework.