An Environmental and Economic Assessment of Household Food Waste Management Scenarios in Ireland

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is well written and within the scope of the journal. however the paper lacks the novelty required for a publication. It is a well technical report of the Irland situation. However the conclussions do not go beyond the state of the art. Results are similar to the ones obtained by Slorach et al in "Assessing the economic and environmental sustainability of household food waste management in the UK: Current situation and future scenarios".

Therefore, the manucsript cannot be recomened for its publication.

Author Response

Comment 1: The manuscript is well written and within the scope of the journal. however, the paper lacks the novelty required for a publication. It is a well technical report of the Irland situation. However the conclusions do not go beyond the state of the art. Results are similar to the ones obtained by Slorach et al in "Assessing the economic and environmental sustainability of household food waste management in the UK: Current situation and future scenarios". Therefore, the manuscript cannot be recommended for its publication.

We appreciate the reviewer’s concern regarding the novelty of our study. We have taken this opportunity to better clarify and enhance the contribution of our work by:

• Strengthening the Discussion and Conclusion to emphasize methodological and policy relevance beyond existing UK-focused studies,
• Clearly contrasting our Ireland-specific approach to prior work by Slorach et al. and others,
• Highlighting our integration of MCDA with LCA and LCC as a novel contribution to decision-support tools in waste management.

We hope that with these clarifications, the revised manuscript now communicates better its value to both the scientific and policy communities.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Data Limitations

Self-Reporting Bias: The survey-based food waste data relies on self-reported household responses, which inherently underreport actual waste generation (acknowledged in the text but not quantified). No triangulation with direct waste audits or external datasets (e.g., national waste statistics) was performed, weakening data reliability.

Homogeneity of Irish Household Data: The study aggregates data from 974 households without disaggregating by regional, socioeconomic, or cultural factors, limiting the representativeness of results.

Methodological Simplifications

LCA Model Assumptions: The LCA framework uses static parameters (e.g., fixed biogas yield, compost nutrient content) without accounting for temporal variability (e.g., seasonal changes in food waste composition, technological advancements).

Allocation Methods: The system expansion approach for multi-output processes (e.g., biogas and digestate) assumes linear substitution of conventional products (e.g., grid electricity, synthetic fertilizers), ignoring market dynamics (e.g., oversupply of compost affecting fertilizer substitution rates).

Environmental Impact Gaps

Microplastics and PFAS: The study explicitly acknowledges the absence of microplastic and PFAS analysis in LCA but does not quantify their potential contributions to ecotoxicity or human health risks, despite recent literature highlighting their persistence in organic waste streams.

Soil Health and Biodiversity: No assessment of long-term soil quality impacts (e.g., heavy metal accumulation, microbial community changes) from compost/digestate application, which is critical for sustainable agriculture.

Economic Analysis Constraints

Revenue Uncertainty: The revenue projections for biogas and compost assume stable market prices, neglecting price volatility and regional demand variations. For example, compost sales may face competition from cheaper synthetic fertilizers.

Financing and Subsidies: The LCC analysis does not factor in potential government incentives (e.g., carbon taxes, grants) or penalties (e.g., landfill taxes), which significantly influence investment decisions in waste management.

Regional Context and Scalability

Infrastructure Dependencies: The proposed AD scenarios assume centralized treatment facilities, which may not align with Ireland’s decentralized waste management infrastructure. No assessment of logistics (e.g., transportation costs, storage requirements) for rural areas is provided.

Policy Alignment: While referencing Ireland’s circular economy goals, the study does not evaluate how existing policies (e.g., EU’s Waste Framework Directive) or emerging regulations (e.g., carbon border adjustments) might impact the feasibility of AD-based solutions.

Sensitivity Analysis Scope

Impurity Levels: The sensitivity analysis focuses on AD-incineration but overlooks how impurities (e.g., plastics, metals) affect other scenarios (e.g., ADgas efficiency, compost quality). No assessment of pretreatment technologies to mitigate impurity impacts is included.

Social and Cultural Factors

Public Perception: The study ignores stakeholder attitudes toward AD facilities (e.g., odor concerns, NIMBYism) and compost acceptance, which are critical for successful implementation.

Behavioral Change: No consideration of food waste reduction strategies (e.g., consumer education, redistribution programs) as a complementary approach to treatment.

Technical Validation

Field Data Validation: The AD process modeling relies on generic BMP values and lab-scale data, but no field validation with Irish AD plants is conducted, potentially overestimating energy yields and underestimating operational challenges (e.g., digester failures).

Recommendations for Improvement

Enhance Data Rigor

Triangulate survey data with direct waste audits and national waste statistics.

Disaggregate results by region, income level, and household size.

Refine LCA Methodology

Incorporate dynamic parameters (e.g., seasonal variability, technological learning curves).

Use market-based allocation for co-products (e.g., biogas and digestate) to reflect real-world substitution rates.

Expand Impact Categories

Include microplastic and PFAS pathways in LCA through literature-derived emission factors.

Model long-term soil health impacts using experimental data or soil quality indices.

Strengthen Economic Analysis

Conduct Monte Carlo simulations to account for revenue and cost uncertainties.

Integrate policy-driven financial incentives (e.g., subsidies, carbon pricing) into LCC.

Address Regional Feasibility

Evaluate decentralized AD systems for rural areas and estimate transportation/emission trade-offs.

Align scenarios with Irish and EU policy roadmaps (e.g., REPowerEU, Circular Economy Action Plan).

Improve Technical Validation

Validate AD models with operational data from Irish biogas plants.

Assess impurity mitigation strategies (e.g., advanced sorting technologies).

Consider Social and Behavioral Factors

Conduct stakeholder interviews or surveys to gauge public acceptance of AD and composting.

Explore food waste reduction policies as a supplementary strategy.

These improvements would enhance the study’s robustness and relevance to real-world decision-making in Ireland and beyond.

Comments on the Quality of English Language

The English version of this paper needs further polishing.

Author Response

Comment 1: Data Limitations

Self-Reporting Bias: The survey-based food waste data relies on self-reported household responses, which inherently underreport actual waste generation (acknowledged in the text but not quantified). No triangulation with direct waste audits or external datasets (e.g., national waste statistics) was performed, weakening data reliability. Homogeneity of Irish Household Data: The study aggregates data from 974 households without disaggregating by regional, socioeconomic, or cultural factors, limiting the representativeness of results.

Response: We thank the reviewer for highlighting this important limitation. In response, we have added a new subsection titled “Limitations of Primary Data Collection” in the Methods section. This paragraph explicitly acknowledges the potential for underreporting in self-reported data, the lack of regional/socioeconomic disaggregation, and the absence of triangulation with external datasets. These limitations are also noted as priorities for future data collection efforts to strengthen the accuracy and applicability of the model.

 

Comment 2: Methodological Simplifications

LCA Model Assumptions: The LCA framework uses static parameters (e.g., fixed biogas yield, compost nutrient content) without accounting for temporal variability (e.g., seasonal changes in food waste composition, technological advancements).

 

Response: We appreciate the reviewer’s thoughtful observation. We acknowledge that the use of static parameters such as average biogas yield and compost nutrient content does not capture temporal variability in food waste composition or system performance. This simplification was necessary to maintain model tractability and to reflect the average operational conditions over the assumed 10-year system lifetime. Given the limited availability of high-resolution seasonal or monthly waste composition data in Ireland, static modeling remains the most practical approach for the current analysis. Nonetheless, we agree that incorporating dynamic LCA with temporal parameters—such as seasonal variations in organic content, moisture levels, and technological efficiency—would improve the accuracy and realism of future LCA models. We have now explicitly noted this as a limitation in the manuscript and suggested it as an important area for further research, especially as time-series data from municipal audits or AD facility performance becomes more accessible.

 

Comment 3: Allocation Methods

The system expansion approach for multi-output processes (e.g., biogas and digestate) assumes linear substitution of conventional products (e.g., grid electricity, synthetic fertilizers), ignoring market dynamics (e.g., oversupply of compost affecting fertilizer substitution rates).

 

Response: We thank the reviewer for this insightful comment. The system expansion approach was adopted in line with ISO 14044 recommendations and to ensure consistency in comparing the avoided burden of co-products such as grid electricity and synthetic fertilizers. We acknowledge, however, that this method assumes linear substitution and does not account for market constraints, such as oversupply or limited regional demand for compost or digestate.

Due to the lack of reliable data on regional compost market dynamics in Ireland, including price fluctuations and application rates, a market-based or economic allocation method was not feasible within the scope of this study. We have now explicitly acknowledged this limitation in the revised manuscript and suggested that future studies should integrate market elasticity models or region-specific allocation factors where data permits

 

Comment 4: Environmental Impact Gaps

Microplastics and PFAS: The study explicitly acknowledges the absence of microplastic and PFAS analysis in LCA but does not quantify their potential contributions to ecotoxicity or human health risks, despite recent literature highlighting their persistence in organic waste streams.

Response: We appreciate the reviewer’s important observation. We fully recognize that microplastics and PFAS are emerging contaminants of concern, particularly in organic waste streams such as compost and digestate, and that their potential ecotoxicity and persistence present growing challenges for sustainable waste valorization.

While we briefly acknowledged their exclusion in the original manuscript, we now wish to clarify that these impact pathways were not included due to the lack of consensus on standardized emission factors, fate and transport models, and characterization methods within existing LCIA frameworks (e.g., ReCiPe, CML). Furthermore, region-specific data on microplastic and PFAS concentrations in Irish food waste or digestate streams is not yet available.

Including these contaminants would require extensive additional assumptions and modeling layers, which would go beyond the scope and word limits of this article. However, we agree that this is a critical area for future research, and we have updated the discussion to emphasize the need for integrating such pathways into future LCA work, especially as characterization models evolve and relevant data becomes more accessible.

 

 

 

Comment 5: Soil Health and Biodiversity

 No assessment of long-term soil quality impacts (e.g., heavy metal accumulation, microbial community changes) from compost/digestate application, which is critical for sustainable agriculture.

Response: We appreciate this important observation. Indeed, long-term soil health impacts—such as heavy metal accumulation, nutrient leaching, and microbial shifts—are critical factors in evaluating the sustainability of compost and digestate use in agriculture. However, due to data limitations and the absence of region-specific experimental studies in Ireland, these factors were not included in the current LCA framework.

We have now acknowledged this limitation in the manuscript and emphasized that future work should incorporate field data or modeling approaches to assess long-term impacts on soil quality, biodiversity, and agroecosystem resilience. This would improve the robustness of compost/digestate pathways and provide better alignment with sustainable agriculture goals.

 

Comment 6: Economic Analysis Constraints

Revenue Uncertainty: The revenue projections for biogas and compost assume stable market prices, neglecting price volatility and regional demand variations. For example, compost sales may face competition from cheaper synthetic fertilizers.

Response: We appreciate the reviewer’s comment regarding revenue uncertainty. We fully acknowledge that the market prices for biogas and compost are subject to fluctuations due to factors such as policy incentives, energy markets, and competition from synthetic alternatives. In this study, we adopted average market values as a simplifying assumption to maintain consistency across scenarios and facilitate comparability. While these assumptions introduce uncertainty, our primary aim was to establish a baseline assessment of economic viability. We agree that future studies should incorporate sensitivity analyses or probabilistic models to better capture the effects of market variability on revenue projections.

 

Comment 7: Financing and Subsidies

The LCC analysis does not factor in potential government incentives (e.g., carbon taxes, grants) or penalties (e.g., landfill taxes), which significantly influence investment decisions in waste management.

Response: We thank the reviewer for highlighting this important consideration. We agree that policy instruments such as carbon taxes, landfill levies, and financial subsidies can have a substantial impact on the economic feasibility of waste treatment options. However, in this study, we chose to focus on baseline, market-based costs to ensure scenario comparability and to maintain the clarity and scope of the financial assessment. Incorporating such policy-driven dynamics would require additional modeling layers and context-specific assumptions, which would significantly increase the length and complexity of the manuscript—beyond the journal’s recommended limits for research articles. We have noted this as a valuable direction for future research, particularly in the context of national and EU circular economy financing mechanisms.

 

Comment 8: Regional Context and Scalability

Infrastructure Dependencies: The proposed AD scenarios assume centralized treatment facilities, which may not align with Ireland’s decentralized waste management infrastructure. No assessment of logistics (e.g., transportation costs, storage requirements) for rural areas is provided.

Response: We appreciate the reviewer’s thoughtful observation. The assumption of centralized anaerobic digestion (AD) facilities was made to provide a simplified and consistent basis for comparative analysis across treatment scenarios. We acknowledge that this may not fully reflect the decentralized nature of Ireland’s current waste management infrastructure, particularly in rural or remote areas. While integrating detailed logistics and transport modeling would provide important insights, it would also significantly expand the scope and complexity of the study—beyond what is feasible within the word and format constraints of the journal. We consider this a critical area for future research, particularly to assess the trade-offs between centralized and decentralized AD deployment in terms of environmental and economic performance.

 

Comment 9: Policy Alignment

 While referencing Ireland’s circular economy goals, the study does not evaluate how existing policies (e.g., EU’s Waste Framework Directive) or emerging regulations (e.g., carbon border adjustments) might impact the feasibility of AD-based solutions.

Response: We appreciate the reviewer’s important observation regarding the role of broader regulatory frameworks in shaping the feasibility of anaerobic digestion (AD) and other waste treatment pathways. While our study references Ireland’s circular economy strategy, we intentionally focused the analysis on environmental and economic performance under current baseline conditions to maintain a manageable scope. A comprehensive policy evaluation—including the influence of EU-wide directives and emerging instruments such as carbon border adjustments—would require detailed scenario modeling and dynamic regulatory analysis, which we recognize as a valuable area for future research.

To acknowledge this limitation and its relevance, we have added a paragraph in Section 3.15. Limitations and prospects for future research that highlights the potential impacts of EU and international policies on the implementation and long-term viability of AD-based systems. This addition also points to the need for future research that integrates evolving regulatory and financial mechanisms into life cycle and techno-economic assessments. Please check Page 27, Line 1107.

 

Comment 10: Sensitivity Analysis Scope

Impurity Levels: The sensitivity analysis focuses on AD-incineration but overlooks how impurities (e.g., plastics, metals) affect other scenarios (e.g., ADgas efficiency, compost quality). No assessment of pretreatment technologies to mitigate impurity impacts is included.

Response: We thank the reviewer for this insightful observation. We agree that impurities such as plastics and metals can significantly affect the performance of anaerobic digestion and composting processes—both in terms of process efficiency and end-product quality. In this study, we focused the sensitivity analysis on the AD-incineration scenario due to its relatively higher environmental burden and the presence of combustion-specific trade-offs. However, we acknowledge that extending the analysis to include impurity impacts on AD and composting systems—particularly in relation to biogas yield reduction, digestate contamination, and compost marketability—would provide additional depth and real-world relevance. Due to space limitations and the absence of comprehensive data on impurity concentrations and pretreatment efficiency across Irish household waste streams, this was not incorporated into the current analysis.

Comment 11: Social and Cultural Factors

Public Perception: The study ignores stakeholder attitudes toward AD facilities (e.g., odor concerns, NIMBYism) and compost acceptance, which are critical for successful implementation.

Response: We appreciate the reviewer’s observation regarding the role of public perception in the successful implementation of anaerobic digestion (AD) and composting systems. We fully agree that factors such as odor concerns, community acceptance, and stakeholder engagement can significantly influence project feasibility and long-term adoption. However, the primary aim of this study was to develop a quantitative, scenario-based assessment of the environmental and economic trade-offs associated with food waste treatment pathways in Ireland.

Incorporating social perception data—such as public surveys, stakeholder interviews, or behavioral analysis—would have required an entirely different methodological approach and significantly expanded the scope of the study. Given the focus on life cycle assessment (LCA) and life cycle costing (LCC), and in light of word count and article length constraints, we elected to maintain a technical focus. We acknowledge the importance of this topic and view it as a complementary area for future interdisciplinary research that could build upon our findings by exploring the social acceptance dimensions of AD and composting systems.

 

Comment 12: Behavioral Change

No consideration of food waste reduction strategies (e.g., consumer education, redistribution programs) as a complementary approach to treatment.

Response: We thank the reviewer for this valuable comment. We fully agree that food waste prevention and behavioral change strategies—such as consumer education, portion control, and food redistribution—are critical components of a holistic food waste management system. However, the focus of this study was on the comparative sustainability of treatment pathways for unavoidable or already generated household food waste, rather than upstream waste prevention interventions.

Integrating behavioral strategies would have required additional modeling dimensions, data sources, and assumptions regarding consumer behavior change effectiveness, which fall outside the scope of the current research. Additionally, incorporating such elements would have significantly extended the manuscript beyond the journal’s recommended word count for research articles. We consider this an important avenue for future work that could build on the environmental and economic baseline established here by exploring how upstream prevention measures interact with downstream treatment options to further optimize national food waste strategies.

 

Comment 13: Technical Validation

Field Data Validation: The AD process modeling relies on generic BMP values and lab-scale data, but no field validation with Irish AD plants is conducted, potentially overestimating energy yields and underestimating operational challenges (e.g., digester failures).

Response: We thank the reviewer for highlighting this important point. We acknowledge that the anaerobic digestion (AD) modeling in this study is based on average Biochemical Methane Potential (BMP) values from established literature and laboratory-scale experiments. This approach was chosen due to the limited availability of high-resolution, publicly accessible performance data from operational AD facilities in Ireland. While using empirical field data would certainly strengthen model validation and improve the accuracy of energy yield estimates, such data is often site-specific and proprietary, posing challenges for broad scenario-based modeling.

Given the study’s objective of comparing treatment pathways at a national level using a consistent and transferable framework, we opted to use standardized values to ensure methodological comparability across scenarios. We recognize this as a limitation and have identified the integration of field-level operational data from Irish AD facilities as a priority for future research. However, expanding the study to include detailed validation would have significantly increased its scope, length, and complexity—beyond what is supported within the journal’s format and focus for research articles.

 

Comment 14: Recommendations for Improvement-Enhance Data Rigor

Triangulate survey data with direct waste audits and national waste statistics.

Disaggregate results by region, income level, and household size.

Response: We appreciate the reviewer’s thoughtful suggestions regarding data triangulation and demographic disaggregation. We fully agree that combining survey responses with direct waste audits and national waste statistics would enhance the robustness of household food waste estimates. However, due to limited access to harmonized audit data and the anonymized nature of our survey instrument, triangulation with other datasets and disaggregation by region, income, or household type were not feasible within the scope of this study.

The primary aim was to develop a high-level, nationally relevant assessment of household food waste treatment options using integrated LCA and LCC approaches. Incorporating disaggregated modeling and multi-source validation would have significantly expanded the study’s data demands and exceeded the word count and methodological limits of the journal’s article format. That said, we acknowledge the value of this approach and consider it a priority for future work—particularly in efforts to develop more targeted, region-specific food waste policies or to calibrate environmental models using multi-tier data sources.

 

Comment 15: Refine LCA Methodology

Incorporate dynamic parameters (e.g., seasonal variability, technological learning curves).

Use market-based allocation for co-products (e.g., biogas and digestate) to reflect real-world substitution rates.

Response: We thank the reviewer for these valuable methodological suggestions. In response, we have revised the methodology section (see Section 2.2.3) to more clearly articulate the assumptions and limitations related to static modeling and allocation methods. We acknowledge that the current LCA model does not incorporate dynamic parameters such as seasonal variation in food waste composition or long-term technological learning effects, due to the absence of time-resolved regional datasets and the study’s focus on current baseline scenarios. This limitation is now explicitly stated in the revised manuscript.

Regarding allocation, we continue to use the system expansion approach for co-products (biogas and compost) to align with ISO 14044 and enable transparent scenario comparison. However, we have added a discussion in Section 2.2.3 to acknowledge the limitations of this method and the potential benefits of market-based allocation, particularly where oversupply or regional demand variations might affect substitution rates. We agree that incorporating such dynamic and market-driven parameters would enhance the realism of future assessments and have highlighted this as an important area for future research in the revised Discussion section (Section 4).

 

Comment 16: Expand Impact Categories

Include microplastic and PFAS pathways in LCA through literature-derived emission factors.

Model long-term soil health impacts using experimental data or soil quality indices.

Response: We appreciate the reviewer’s insightful recommendation regarding the inclusion of emerging contaminants such as microplastics and PFAS in the LCA framework, along with long-term soil health metrics. We fully acknowledge that these impact categories are increasingly relevant in assessing the sustainability of organic waste treatment, especially with growing attention to environmental persistence and ecotoxicity.

However, the incorporation of PFAS and microplastics into LCA models remains highly complex due to limited consensus on emission factors, spatial distribution models, degradation rates, and characterization methods across current LCIA frameworks. Additionally, robust experimental data on their accumulation through digestate or compost application in Irish soils is not yet available. Modeling these pathways would require extensive assumptions and introduce significant uncertainty, which falls outside the intended scope and methodological depth of the current study.

Similarly, long-term impacts on soil health—such as heavy metal accumulation or changes in microbial communities—are important considerations but were not included due to a lack of validated, region-specific indices and the focus of this study on comparative, mid-point LCA metrics.

We have acknowledged these exclusions in our discussion of limitations and identified them as critical directions for future research that could integrate experimental data and advanced LCIA modeling to capture a more comprehensive set of environmental trade-offs.

 

Comment 17: Strengthen Economic Analysis

Conduct Monte Carlo simulations to account for revenue and cost uncertainties.

Integrate policy-driven financial incentives (e.g., subsidies, carbon pricing) into LCC.

Response: We thank the reviewer for this insightful recommendation. We fully agree that incorporating uncertainty analysis through Monte Carlo simulations and integrating policy-related financial instruments would provide a more robust and decision-relevant economic assessment.

In this study, we addressed uncertainty by presenting upper and lower bounds for capital costs, operational costs, and revenue estimates across all treatment scenarios (see Table 4). While Monte Carlo simulations were considered, they were not implemented due to time and resource constraints, as well as the journal’s limitations on manuscript length and formatting. However, we acknowledge their value and identify this as a key direction for future work, particularly in developing probabilistic LCC models that better reflect real-world financial variability.

Regarding financial incentives, we intentionally excluded policy-driven mechanisms such as subsidies, landfill taxes, or carbon pricing to maintain comparability under baseline market conditions. Including such instruments would require policy-specific assumptions and scenario modeling that, while valuable, would have significantly expanded the scope and complexity of the current work. We have acknowledged this limitation in the manuscript and consider it an important area for future scenario development.

 

Comment 18: Address Regional Feasibility

Evaluate decentralized AD systems for rural areas and estimate transportation/emission trade-offs.

Response: We thank the reviewer for highlighting this important aspect of regional feasibility. We agree that the spatial distribution of treatment infrastructure—particularly the trade-offs between centralized and decentralized anaerobic digestion (AD) systems—has significant implications for environmental performance and logistical efficiency. However, this study was designed as a national-scale comparative analysis using generalized assumptions and system boundaries. Incorporating a detailed spatial assessment of decentralized AD systems would have required high-resolution geospatial data, detailed transport logistics modeling, and region-specific infrastructure mapping, which were beyond the intended scope and data availability for this study.

Furthermore, such an extension would substantially increase the complexity and length of the manuscript, exceeding the word limits typically supported for research articles in the journal. We have now acknowledged this as a key limitation and a valuable area for future research—particularly for informing rural bioeconomy strategies and optimizing AD system deployment across heterogeneous geographic contexts in Ireland.

 

Comment 19: Align scenarios with Irish and EU policy roadmaps (e.g., REPowerEU, Circular Economy Action Plan).

Response: We appreciate the reviewer’s suggestion to better contextualize the scenarios within current Irish and EU policy frameworks. In response, we have added a dedicated paragraph in the Discussion section (Section 4) that explicitly references relevant policy instruments, including the REPowerEU Plan, Ireland’s Waste Action Plan for a Circular Economy (2020–2025), and the EU Circular Economy Action Plan. This addition highlights how the study’s findings support Ireland’s transition toward low-carbon, resource-efficient waste systems and how AD-composting pathways, in particular, align with EU objectives for bioenergy, nutrient recycling, and landfill reduction.

While we did not expand the scope to conduct a dynamic policy scenario analysis due to space and data constraints, this added discussion improves the policy relevance of the study and outlines how future work could more directly integrate policy-driven system modeling.

 

Comment 20: Improve Technical Validation

Validate AD models with operational data from Irish biogas plants.

Assess impurity mitigation strategies (e.g., advanced sorting technologies).

Response: We thank the reviewer for this valuable suggestion. We agree that validating the anaerobic digestion (AD) model using real-world operational data from Irish biogas facilities would enhance the technical accuracy and credibility of the study. However, access to such detailed, site-specific performance data, including biogas yield variability, digester reliability, and contaminant profiles—is currently limited due to confidentiality constraints and inconsistent data reporting across facilities. Given these limitations, the study relied on well-established BMP values and literature-based process assumptions that are widely accepted in comparative LCA modeling.

We also acknowledge the importance of impurity mitigation strategies, such as advanced sorting and pre-treatment systems, particularly in improving feedstock quality and system efficiency. However, modeling these technologies in detail would require process-specific operational and cost data, and would have substantially increased the complexity and length of the manuscript beyond the journal's recommended limits for research articles.

We have therefore maintained a more generalized model structure to ensure methodological clarity and comparability and consider technical validation using operational plant data and the integration of impurity management technologies as key directions for future research.

 

Comment 21: Consider Social and Behavioral Factors

Conduct stakeholder interviews or surveys to gauge public acceptance of AD and composting.

Explore food waste reduction policies as a supplementary strategy.

Response: We appreciate the reviewer’s thoughtful suggestion regarding the integration of social and behavioral dimensions into the analysis. We agree that public acceptance of anaerobic digestion (AD) and composting facilities, along with behavioral change strategies to reduce food waste generation, are critical elements of a comprehensive waste management framework. However, the primary objective of this study was to assess the environmental and economic performance of food waste treatment pathways using life cycle assessment (LCA) and life cycle costing (LCC) methodologies.

Incorporating stakeholder interviews or behavioral modeling would have required an entirely different methodological approach, along with a significant expansion of the study’s scope beyond what is supported by the journal’s format and article length constraints. Moreover, our focus was on the treatment of unavoidable household food waste, rather than the broader spectrum of prevention and redistribution strategies.

We have now acknowledged the absence of social factors and upstream prevention measures as a limitation of the current work and identified them as valuable avenues for interdisciplinary research that builds upon the baseline analysis provided here.

 

Comment 22: These improvements would enhance the study’s robustness and relevance to real-world decision-making in Ireland and beyond.

Response: We sincerely appreciate the reviewer’s comprehensive feedback and constructive suggestions. Many of the points raised—such as enhanced data triangulation, technical validation, expanded impact categories, and policy alignment—are indeed valuable and would contribute to a broader, more integrated framework for food waste management assessment. While several of these elements were beyond the scope and word limits of the current article, we have carefully revised the manuscript to improve methodological clarity, acknowledge key limitations, and outline specific directions for future research.

Our goal was to establish a regionally grounded, methodologically transparent baseline that can inform future policy, infrastructure investment, and academic inquiry. We hope the revisions strengthen the study’s contribution to real-world decision-making in Ireland and provide a foundation for further interdisciplinary work aligned with EU sustainability goals.

 

Comment 23: Comments on the Quality of English Language

The English version of this paper needs further polishing.

Response: We appreciate the reviewer’s note regarding the language quality. In response, we have thoroughly revised the manuscript to improve clarity, grammar, and overall readability. Particular attention was paid to sentence structure, technical terminology, and consistency of style throughout the paper. We trust that the updated version meets the expected standards of academic English.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Report
Introduction:
The research gap is poorly articulated, making it difficult to understand what specific issue the study aims to address and There is a lack of engagement with recent and relevant studies, making the gap appear either outdated or irrelevant.
The introduction fails to establish why this research matters in both theoretical and practical contexts.

Methods
There is no strong rationale for why specific methods were chosen over others, reducing the credibility of the research approach.
Essential aspects, such as sample selection, data collection techniques, and analysis procedures, are either vaguely described or completely missing.
2.2. Life cycle assessment 
Needs a stronger discussion on how LCA findings can influence policy, business strategies, and environmental planning.
Should better address the balance between environmental, economic, and social factors.
Enhancing discussions on real-world implementation would strengthen the section’s usefulness in decision-making.
Life Cycle Cost Analysis 
Clearly defining discount rates, cost estimates, and risk factors would improve reliability and comparability.
Strengthening the link between LCCA and LCA would provide a more comprehensive sustainability assessment.
Expanding the scope to include environmental and social costs would enhance decision-making beyond purely financial perspectives.

Comments on the Quality of English Language

 The English could be improved to more clearly express the research.

Author Response

We sincerely thank the reviewer for the constructive comments and suggestions aimed at improving the quality of our manuscript. We have carefully considered all points and made substantial revisions to address each concern. Below, we provide detailed point-by-point responses.

 

Comment 1 – Introduction:

The research gap is poorly articulated, making it difficult to understand what specific issue the study aims to address. There is a lack of engagement with recent and relevant studies, making the gap appear either outdated or irrelevant. The introduction fails to establish why this research matters in both theoretical and practical contexts.

Response: We appreciate the reviewer’s observation and agree that clarifying the research gap and novelty is crucial for framing the significance of the study. In response, we have revised the introduction to explicitly highlight the lack of comparative life cycle assessments (LCAs) of digestate treatment options (composting, incineration, and gasification), particularly within the Irish context. While previous studies have assessed anaerobic digestion (AD) for food waste treatment, very few have addressed the environmental trade-offs associated with downstream digestate management.

We also integrated recent literature (e.g., Maghsoudi et. al., 2025; Lykoudis, 2020) and framed our study as one of the first to provide a region-specific, dual environmental and economic assessment of these pathways using LCA and Life Cycle Costing (LCC). This addition strengthens both the theoretical contribution and the practical value of our research for informing circular economy policy and infrastructure investment decisions in Ireland.

Changes made: A new paragraph was added in the Introduction (lines 41–63), clarifying:

• The need for a comparative LCA of digestate treatment pathways.
• The absence of such an assessment in Irish studies to date.
• The practical significance of our findings in shaping sustainable waste policy.

We trust this addresses the concern and improves the clarity and contextual relevance of our study.

 

Comment 2 – Methods:

There is no strong rationale for why specific methods were chosen over others, reducing the credibility of the research approach. Essential aspects, such as sample selection, data collection techniques, and analysis procedures, are either vaguely described or completely missing.

Response: We appreciate this important comment and have revised the “Materials and Methods” section to clarify and justify our methodological choices. We now explain the rationale behind selecting Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) as integrated tools to assess environmental and economic trade-offs in food waste treatment. Additionally, we provide detailed information on our household food waste survey, including recruitment strategy, sample size, and eligibility criteria. We also elaborate on how food waste quantities were estimated, processed, and integrated into the LCA and LCC frameworks. These additions strengthen the transparency and reproducibility of our approach. Changes made: Please see Section 2.1 (Page3, Lines 115–124) and Section 2.2.1 (Page 6, Lines 210-216) for the revised methodology description.

 

Comment 3 – LCA Section:

Needs a stronger discussion on how LCA findings can influence policy, business strategies, and environmental planning. Should better address the balance between environmental, economic, and social factors. Enhancing discussions on real-world implementation would strengthen the section’s usefulness in decision-making.

Response: We thank the reviewer for this important suggestion. In response, we added the following into the Section 3.13: “Our findings highlight that AD combined with composting provides the lowest environmental burden among the considered scenarios, particularly in terms of green-house gas emissions and eutrophication. These results are highly relevant for Irish pol-icy frameworks such as the Waste Action Plan for a Circular Economy (2020–2025), which aims to reduce landfilling and promote organic recycling. The evidence supports prioritizing funding for AD infrastructure development and composting facilities, especially in regions with high biowaste generation.” This subsection outlines how our LCA and LCC findings can inform real-time decision-making by policymakers, municipal authorities, and waste management firms. We also incorporated a broader sustainability perspective by discussing social equity, behavior change, and infrastructure investment barriers. These additions strengthen the policy and planning relevance of our findings and connect our scenario-based modeling to real-world implementation challenges and opportunities. We also added “From an economic perspective, Life Cycle Costing (LCC) reveals that while incineration yields some energy recovery, its high capital and operational costs make it un-competitive in the absence of strong subsidies. This is particularly relevant for waste management companies and local municipalities evaluating investment in treatment technologies. Our results support the business case for AD-composting systems, especially when integrated with local farming sectors that can utilize compost outputs, reducing dependency on synthetic fertilizers. Social factors also influence the success of food waste management strategies. AD-composting systems, for example, can create green jobs in rural areas, support decentralized waste treatment, and generate public acceptance due to their “natural” outputs (compost). However, successful implementation depends on citizen participation in waste separation at the source. Future planning should consider behavior change incentives and educational campaigns to boost source separation rates, especially in urban areas.” into Section 3.15.4. Social and Policy Considerations.

Changes made: Please see Page 21, lines 821–827, Page 26, Lines 1082-1088.

We also have expanded the Discussion section to acknowledge key real-world implementation challenges associated with AD-composting systems, including infrastructure, public participation, and regulatory gaps. We also provide potential solutions and policy mechanisms to overcome these barriers, thereby strengthening the practical relevance and decision-making utility of our findings. (Page 26, lines 1089–1095).

 

Comment 4 – Life Cycle Cost Analysis (LCCA):

Clearly defining discount rates, cost estimates, and risk factors would improve reliability and comparability. Strengthening the link between LCCA and LCA would provide a more comprehensive sustainability assessment. Expanding the scope to include environmental and social costs would enhance decision-making beyond purely financial perspectives.

 

Response: We thank the reviewer for highlighting this important point. In response, we have clarified the financial assumptions used in the Life Cycle Costing (LCC) model. Specifically, we have now defined the discount rate (4%), cost reference period (2021–2024), and key cost components including capital, operation, maintenance, and revenue streams. These have been benchmarked against market data and values reported in recent literature (see Section 3.12 and Table 4).

To strengthen the integration between LCC and LCA, we have expanded our discussion of trade-offs across environmental and economic indicators, and we introduced a multi-criteria impact-based ranking (Section 3.13). This allows scenarios to be evaluated holistically, taking into account both environmental burdens and financial feasibility, providing a more decision-relevant sustainability assessment.

To integrate environmental and economic performance in a decision-relevant format, we developed a multi-criteria decision analysis (MCDA) using normalized LCA and LCC results. Table 5 presents the sustainability scores for each scenario, combining environmental burden (from ReCiPe-weighted LCA) and cost (€/ton). The combined score enables a clear comparison of trade-offs and supports evidence-based selection of optimal food waste treatment strategies (Table 5). We believe these revisions enhance the transparency, comparability, and practical utility of our study’s outcomes.

We also appreciate the reviewer’s insightful suggestion to incorporate environmental and social externalities into the cost analysis. We fully agree that a more holistic sustainability assessment—including social costs such as health impacts, equity considerations, and public acceptance—would provide additional value for decision-makers. However, due to space limitations and the already extensive integration of both Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), expanding the scope to include social impact assessment or monetized environmental externalities was not feasible within the current study.

That said, we recognize the importance of this broader perspective and intend to explore these dimensions in future research. Specifically, we aim to build on this foundational work by integrating Social Life Cycle Assessment (S-LCA) and external cost quantification methods in subsequent publications. Please see Page 23 and 24, Lines 908-962.

 

Comment 5 – Quality of English:

The English could be improved to more clearly express the research.

Response: We appreciate the reviewer’s comments on the language. The manuscript has undergone comprehensive language editing to improve clarity, sentence structure, and academic tone. Specific attention was given to technical terminology, transitions, and conciseness across all sections.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised manuscript has been improved but the lack of novelty is still a significant issue. The manuscript is more a technical report than a scientific paper.

The state of the art is not completed. There is similar paper on the situation in Germany that is not mentioned in this paper: "Environmental and economic assessment assessment of household food waste source-separation efficiency in a German case study". 2023. Cleaner waste systems. https://doi.org/10.1016/j.clwas.2023.100092

Although this paper is more focus on the pretreatments there are useful and similar information to compate with the situation in Irland. 

In summary although this version is improved, the manuscript cannot be recomended for its publication.

Author Response

Response to Reviewer #1

Comment 1: The revised manuscript has been improved but the lack of novelty is still a significant issue. The manuscript is more a technical report than a scientific paper.

Response: We sincerely thank the reviewer for this observation. We respectfully disagree with the characterization of the manuscript as a technical report rather than a scientific paper. We would like to emphasize that our study follows a well-established tradition of scientific research that combines primary data collection, environmental modeling, and scenario-based analysis to inform sustainability-oriented decision-making — an approach widely published in high-impact journals within waste management, environmental science, and life cycle assessment fields.

Importantly, we highlight that:

• The study is based on original primary data collected directly from 974 Irish households — a dataset not available elsewhere — representing a significant empirical contribution to the literature on food waste management in Ireland.
• The paper advances beyond technical reporting by applying internationally recognized sustainability assessment methods (LCA and LCC), integrated through a structured Multi-Criteria Decision Analysis (MCDA) framework.
• The study provides evidence-based insights for both environmental and economic trade-offs across multiple food waste treatment scenarios, explicitly contextualized within current Irish and EU waste policy frameworks.
• Similar studies combining region-specific data with LCA and LCC approaches — such as Slorach et al. (2020) published by Science of The Total Environment, (IF=8.2, CiteScore=17.6, Article Citation number=109) and Angouria-Tsorochidou et al. (2023) published by Cleaner Waste systems (no IF, CiteScore=2.6, Article Citation number=12)  — are widely published and recognized as scientific contributions precisely because of their applied, data-driven nature aimed at supporting real-world sustainability challenges.

We hope that these clarifications better communicate the scientific value of this work and its contribution to both the academic literature and practical waste management policy development.

 

 

Comment 2: The state of the art is not completed. There is similar paper on the situation in Germany that is not mentioned in this paper: "Environmental and economic assessment of household food waste source-separation efficiency in a German case study". 2023. Cleaner waste systems. https://doi.org/10.1016/j.clwas.2023.100092. Although this paper is more focus on the pretreatments there are useful and similar information to compare with the situation in Irland.  In summary although this version is improved, the manuscript cannot be recommended for its publication

Response: We sincerely thank the reviewer for detailed feedback and for highlighting the recent study by Angouria-Tsorochidou et al. (2023) published in Cleaner Waste Systems. We appreciate this suggestion and fully agree that referencing comparable studies enhances the contextualization and relevance of our work. In response, we have carefully reviewed the cited paper and incorporated it into the revised Introduction and Discussion sections. We have particularly highlighted the similarities in methodological approaches and the contrasting focus areas — noting that while  Angouria-Tsorochidou et al. (2023) provide valuable insights into source-separation efficiencies and pretreatment strategies within the German context, our study extends the scope by evaluating end-of-life treatment scenarios for unavoidable household food waste in Ireland, including a comparative assessment of digestate management options (composting, gasification, and incineration), which has received limited attention in previous literature. Please check Page 2, Lines 88-98, for the following content: “Recent studies have also examined the environmental and economic implications of household food waste management in other European contexts. For example, Angouria-Tsorochidou et al. (2023) conducted a comprehensive assessment of source-separation efficiency and pretreatment strategies in a German case study, highlighting the importance of upstream waste management practices in reducing environmental impacts. While that study focused primarily on the efficiency of source separation and pretreatment processes, there remains a knowledge gap regarding the comparative sustainability of downstream treatment options, particularly for digestate management. This study seeks to address that gap within the Irish context by evaluating multiple end-of-life treatment scenarios for unavoidable household food waste, integrating LCA, LCC, and multi-criteria analysis to support evidence-based policy decisions.”

and Page 21, Lines 839-848 for: “It is also important to situate the findings of this study within the broader European literature on household food waste management. The recent work of Angouria-Tsorochidou et al. (2023) in Germany provides valuable insights into how improving source-separation and pretreatment efficiency can reduce environmental impacts at the household level. In contrast, our study complements this perspective by focusing on the comparative performance of downstream treatment technologies, including multiple digestate management pathways, within the specific waste policy and infrastructure context of Ireland. Together, these studies highlight the need for integrated approaches that consider both upstream behavioral interventions and downstream technological solutions to optimize food waste management systems”

We respectfully note that the novelty of our work lies not only in the geographical focus on Ireland but also in:

• The integration of region-specific household food waste data;
• The comparative assessment of multiple digestate management scenarios;
• The combined LCA-LCC framework supported by MCDA for holistic sustainability assessment;
• The policy relevance tailored to Ireland's Waste Action Plan and broader EU circular economy goals.

It is also important to note that Ireland’s solid waste management infrastructure, particularly for household food waste (HFW), remains less developed compared to countries such as the UK or Germany, where source-separation practices and waste treatment technologies have been more widely implemented for a longer period. In Ireland, the separate collection of food waste from households has only recently become mandatory, and infrastructure for the treatment of biowaste is still expanding. As a result, this study provides valuable insights specific to a context where waste management systems are still evolving, and may offer lessons that go beyond the experiences of more established systems in mainland Europe. This further reinforces the relevance of our findings to other regions undergoing similar transitions toward circular economy practices.

While we recognize that some elements of the study are technical in nature — due to the data-driven scenario analysis — we respectfully submit that this technical rigor is essential for supporting scientifically grounded decision-making in waste management, which aligns with the aims and scope of Recycling.

We hope that with these additions and clarifications, the distinct contribution and scientific value of our study are now more apparent.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The author has responded well to the questions raised last time and has revised and improved the article. This is commendable. It is recommended that this paper be accepted for publication.

Author Response

Responses to Reviewer #2

Comment 1: The author has responded well to the questions raised last time and has revised and improved the article. This is commendable. It is recommended that this paper be accepted for publication.

Response: We sincerely thank the reviewer for positive and encouraging feedback. We greatly appreciate your recognition of the efforts made to revise and improve the manuscript in response to the previous comments. We are pleased that the revisions have addressed your concerns, and that the manuscript is now considered suitable for publication. Thank you again for your constructive input and support throughout the review process.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The required modifications have been made

Author Response

Response to Reviewer #3

Comment 1: The required modifications have been made.

Response: We thank the reviewer for their positive feedback and recommendation for publication. We confirm that all the required modifications have been made, and we sincerely appreciate the constructive comments and valuable insights provided during the review process.

Author Response File: Author Response.docx