Technical and Environmental Comparison among Different Municipal Solid Waste Management Scenarios

Round 1

Reviewer 1 Report

The title should be more specific. Readers can expect almost everything to be in the paper.
Do not use acronyms in the title - MSW.
Define all acronyms at the first occurrence - e.g. GHG, WtE,...
Line 130, page 3 - "adavtages", "disadvatanges" - check spelling.
The meaning of MSW - municipal solid waste - has to be defined - do not be mistaken with MMW - mixed municipal waste. Please specify, which you mean and treat at each occurrence.
The composition of waste varies a lot and it has a direct impact on energy production and operational conditions of the plant. Comment on this, where applicable.
Describe CO_2 equivalent - why is the unit in t_CO_2 and not in t_CO_2e at each occurrence?
Table 1 - add also a country of each plant, please use dots and commas according to international standards regarding the numbers.
More information on each treatment plants needed - input stream of waste, technology, gas capture for landfills, flue gas cleaning etc.
SCR - no need for the acronym, when used only once.
Overall, the novelty of the paper is not clear. Conclusions on the best treatment options were already published. Some additional comparisons are needed, it could reveal new insights.
The environmental and cost evaluation is not compact, inconsistencies need to be addressed.

Author Response

REVIEWER 1

The title should be more specific. Readers can expect almost everything to be in the paper

Thanks a lot for you comment, we modified the title. The new title is: “Technical and environmental comparison among different Municipal Solid Waste management scenarios”.

Do not use acronyms in the title - MSW

Ok, thanks a lot for the suggestion.

Define all acronyms at the first occurrence - e.g. GHG, WtE,...

Thanks a lot for your comment. We defined it.

Line 130, page 3 - "adavtages", "disadvatanges" - check spelling

Thank you very much. We corrected it.

The meaning of MSW - municipal solid waste - has to be defined - do not be mistaken with MMW - mixed municipal waste. Please specify, which you mean and treat at each occurrence

Thanks a lot for your comment. We specified it, for example for the Bestrade P2P plant the waste input stream consists in Municipal Solid Waste and residual plastic materials

The composition of waste varies a lot and it has a direct impact on energy production and operational conditions of the plant. Comment on this, where applicable

Yes, this is true, in fact we wrote in the text the following sentence “The developed indexes allow to have a general framework of the analyzed technology, in fact they depend certainly to the composition of the MSW in input but also to the adopted technology for the energy revenue and also to the employed flue gas depuration line”. For the Bestrade P2P plant we reported that “the waste input stream consists in Municipal Solid Waste and residual plastic materials”.

Describe CO₂ equivalent - why is the unit in t_CO₂ and not in t_CO_2e at each occurrence?

Thank you very much for your comment: there was a mistake. The right term is always CO_2e. We corrected it in the text paper.

Table 1 - add also a country of each plant.

Ok, we added the information concerning the Country.

Please use dots and commas according to international standards regarding the numbers.

Ok, thanks a lot. We corrected it.

More information on each treatment plants needed - input stream of waste, technology, gas capture for landfills, flue gas cleaning etc.

Thanks a lot for your useful comment. We added these information into the paper text.

SCR - no need for the acronym, when used only once.

Ok, thanks for your suggestion.

Overall, the novelty of the paper is not clear. Conclusions on the best treatment options were already published. Some additional comparisons are needed, it could reveal new insights.
The environmental and cost evaluation is not compact, inconsistencies need to be addressed.

Thanks for your comment. The comparison methodology that has been defined (with the definition of the four indexes) can establish a more general useful approach, in order to help the definition of the best solution for waste management planning. In fact in this way, with the results of the indexes approach, it is possible to proceed with a comparison of different waste management scenario (Landifll, MBT, thermal treatment, etc) and for a single solution with the evaluation of different possibility (choise of BAT, choise of the energetic configuration,  etc).

Reviewer 2 Report

The paper topic is very interesting and relevant for the scope of the journal. However, the analysis lacks important considerations on factors that strongly affect the results. Therefore conclusions are very weak. Below are my comments and recommendations.

• Line 64: The statement that energy recovery from MSW is not a relevant solution for England and Norway is not true. The cited reference for England is from 1997 and the situation has changed since then. The statistic that is cited for Norway is not about MSW but about everything defined as waste, which also includes e.g. filling material from excavation works. As far as MSW is concerned, landfilling of degradable material has indeed been banned in Norway since 2009 (https://www.internationallawoffice.com/Newsletters/Environment-Climate-Change/Norway/Arntzen-de-Besche-Advokatfirma-AS/New-Landfill-Ban-on-Biodegradable-Waste). For updated statistics on MSW treatment see e.g.: https://www.cewep.eu/municipal-waste-treatment-2018/. Please update and rewrite.

• Table 1: The "Plant suppliers" indicated for some of the plants are not the suppliers, but the owners of the plants. Please correct this.

• Table 2: the heating value of the fuel processed in the Bestrade P2P plant (which must be larger than 4.18+3.36MWh/t, corresponding to 27 MJ/kg) is not typical of MSW streams. What fuel is processed at this plant?

• Line 202: The fact that emissions of incineration plants are so low is due to the fact that such plants are subject to very strict emission regulations that make necessary the adoption of advanced flue gas cleaning systems. What are the flue gas cleaning systems of the different plants (both incineration and gassification/pyrolysis)? Gassification/pyrolysis plants with the similar flue gas cleaning systems would probably hold similar emissions.

• Table 5: Assuming full thermal conversion of the MSW, the results for both traditional and innovative MSW treatment systems depend on the composition of the MSW only. What is the relevance of Index D?

• Line 268: In Europe, MSW is approximately 50% biogenic (i.e. originated from renewable biomass). This means that approximately 50% of the CO2 emissions have a zero net impact on the CO2 balance in the atmosphere.

• Line 269: It is not true that there are no consolidated technologies for CO2 removal. Amine-based absorption plants have been used for decades for CO2 removal from gas mixtures. The reason why no CO2 removal solution is adopted is that CO2 emissions are not regulated (as opposed to other emissions) and that both capex and opex of such removal systems are high. Please correct and rewrite.

• The analysis is very weak. The reported results depend very little on the adopted technology (incineration vs gasification). They indeed depend mostly on 1) waste composition, 2) flue gas treatment and 3) heat and power delivery requirements. Without taking these three boundary conditions into account, the results are not very meaningful to compare.

Author Response

REVIEWER 2

The paper topic is very interesting and relevant for the scope of the journal. However, the analysis lacks important considerations on factors that strongly affect the results. Therefore conclusions are very weak. Below are my comments and recommendations.

• Line 64: The statement that energy recovery from MSW is not a relevant solution for England and Norway is not true. The cited reference for England is from 1997 and the situation has changed since then. The statistic that is cited for Norway is not about MSW but about everything defined as waste, which also includes e.g. filling material from excavation works. As far as MSW is concerned, landfilling of degradable material has indeed been banned in Norway since 2009 (https://www.internationallawoffice.com/Newsletters/Environment-Climate-Change/Norway/Arntzen-de-Besche-Advokatfirma-AS/New-Landfill-Ban-on-Biodegradable-Waste). For updated statistics on MSW treatment see e.g.: https://www.cewep.eu/municipal-waste-treatment-2018/. Please update and rewrite.

Thanks a lot for the useful comment. We corrected and introduced the two website references.

• Table 1: The "Plant suppliers" indicated for some of the plants are not the suppliers, but the owners of the plants. Please correct this.

Thank you very much for your comment. We corrected it

• Table 2: the heating value of the fuel processed in the Bestrade P2P plant (which must be larger than 4.18+3.36MWh/t, corresponding to 27 MJ/kg) is not typical of MSW streams. What fuel is processed at this plant?

Thank you very much for your comment. This is true: in fact the waste stream in input consists, in this case, in MSW an residual plastic materials. We added this information into the paper text.

• Line 202: The fact that emissions of incineration plants are so low is due to the fact that such plants are subject to very strict emission regulations that make necessary the adoption of advanced flue gas cleaning systems. What are the flue gas cleaning systems of the different plants (both incineration and gassification/pyrolysis)? Gassification/pyrolysis plants with the similar flue gas cleaning systems would probably hold similar emissions.

Thank you for your comment and suggestion. We introduced a new Table (Table 2) with the information of the flue gas depuration line adopted by the different plants.

• Table 5: Assuming full thermal conversion of the MSW, the results for both traditional and innovative MSW treatment systems depend on the composition of the MSW only. What is the relevance of Index D?

Thanks for the comment. The index D is concerning the ratio between the total amount of CO_2e produced from the considered plant (in our case thermal treatment or landfill facilities) and the total treated wastes (t_CO2e/t_MSW). In this way it is possible to compare the different final waste management scenarios (thermal treatment, landfill but also MBT, etc) from the viewpoint of the CO_2e emission that we know to be one of the main responsible of the Climate Change.

• Line 268: In Europe, MSW is approximately 50% biogenic (i.e. originated from renewable biomass). This means that approximately 50% of the CO₂ emissions have a zero net impact on the CO₂ balance in the atmosphere.

            Thanks a lot for your comment. We introduced your correct consideration into the paper text.

• Line 269: It is not true that there are no consolidated technologies for CO₂ removal. Amine-based absorption plants have been used for decades for CO₂ removal from gas mixtures. The reason why no CO₂ removal solution is adopted is that CO₂ emissions are not regulated (as opposed to other emissions) and that both capex and opex of such removal systems are high. Please correct and rewrite.

Thanks for your comment. We corrected and rewritten the sentence.

• The analysis is very weak. The reported results depend very little on the adopted technology (incineration vs gasification). They indeed depend mostly on 1) waste composition, 2) flue gas treatment and 3) heat and power delivery requirements. Without taking these three boundary conditions into account, the results are not very meaningful to compare.

Thanks for your correct comment, we think that the specific obtained results depend mostly on the waste composition, the flue gas treatment and the heat and power delivery requirements (as you reported) but the comparison methodology that has been defined can establish a more general useful approach, in order to help the definition of the best solution for waste management planning.

Round 2

Reviewer 1 Report

The paper has been improved, however, not sufficiently.

Please dedicate more time and effort to the following comments from the first review:

Spell check required - many typos still occur in the manuscript.

The novelty has to specified clearly in the introduction.

The properties of input waste are crucial for the operation of each plant, at least proper discussion has to be provided if not data analysis takes place.

Conclusion lacks new information. Please go through the whole paper and update it with new ideas and points of view.

Author Response

REVIEWER 1

The paper has been improved, however, not sufficiently.

Please dedicate more time and effort to the following comments from the first review:

Spell check required - many typos still occur in the manuscript

Thanks a lot for your comment. We did what you suggested.

The novelty has to specified clearly in the introduction

Thanks a lot for your comment. We added in the introduciton the following sentence: “From a general viewpoint, the novelty of the work is the definition of synthetic indexes through which it is possible to evaluate different waste management scenarios from a technological and environmental point of view”

The properties of input waste are crucial for the operation of each plant, at least proper discussion has to be provided if not data analysis takes place

Dear Reviewer, thanks a lot for your comment. We searched for more information about each plant. For everyone (except for P2P plant) we found that the input power supply consists predominantly of MSW. We didn't find the product composition.

Anyway, we agree with what you write. For this reason we have reported the following comment in the text: “In particular, the composition of waste is a very important parameter for the operation of each plant: the flue gas depuration line to be adopted and the amount of energy recovery also depend on it.”

Conclusion lacks new information. Please go through the whole paper and update it with new ideas and points of view

Thanks for your comment.

In the conclusion chapter we reported the discussion of the results obtaining from our study. So we reported the indexes methodology and the results of the methodology implementation to the analyzed MSW management scenario.

Finally we reported a general conclusion: “In conclusion, the specific obtained results depend mostly on the waste composition, the flue gas treatment and the heat and power delivery requirements but the comparison methodology that has been defined can establish a more general useful approach, in order to help the definition of the best solution for waste management planning”.

Reviewer 2 Report

All comments and queries have been answered in the revised manuscript.

Author Response

REVIEWER 2

All comments and queries have been answered in the revised manuscript

Dear Reviewer, thanks a lot

Round 3

Reviewer 1 Report

Thank you for the updates. Since there is no additional information available, the manuscript can be accepted.