Analysis of the Environmental Impact of Different Olive Grove Systems in Southern Portugal

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors attempt to address an important and policy-relevant issue, which is the environmental implications of olive grove intensification in Portugal using a LCA approach. The topic fits well within Sustainability’s scope and contributes useful regional evidence to the broader Mediterranean discussion. The work reflects a good command of LCA methodology and commendable primary data collection from farmers. However, there are fundamental issues about their work.

The authors claim novelty by focusing on Portuguese olive groves with primary data. While this is partly justified, the study’s added value compared to prior works (e.g., Sales et al., 2022; Romero-Gámez et al., 2017; De Luca et al., 2018) is only briefly articulated.

The innovation relative to the Sustainolive project and similar southern European studies is underexplained. The authors should explicitly clarify whether their contribution is methodological (e.g., detailed LCI for Portuguese farms), geographical (Alentejo specificity), or analytical (comparison of alternative vs. standard systems).

The discussion mostly reiterates known findings (fertilization as the dominant hotspot). The paper would be stronger if it showed quantitative differences between this case and existing Mediterranean LCAs or presented a sensitivity analysis illustrating regional uniqueness.

The authors follow ISO 14040/44 and use SimaPro 9.4 with ReCiPe 2016, which is appropriate. Still, several methodological decisions need clearer justification:

1. Functional unit: using 1 ha is valid for comparing systems but not for assessing productivity or per-output impacts. The omission of yield-based results (e.g., per kg olive or per L olive oil) restricts interpretability. Since productivity varies sharply across densities, the conclusions about “sustainability” per hectare could be misleading.

2. The “cradle-to-farm gate” scope excludes post-harvest and oil-milling processes, but the abstract and conclusion refer to “olive oil production,” which is inconsistent. Clarify whether olive oil refers to the upstream agricultural stage only.

3. The inventory (Table 3) is comprehensive, yet no uncertainty or variability ranges are reported. Given that much data come from six farms, statistical treatment (mean ± SD or coefficient of variation) would improve robustness.

4. Modeling 100 years through repeated cycles is unconventional for agricultural LCAs and may distort cumulative impacts. A normalization to yearly averages or an explicit time-weighting rationale should be provided.

5. Electricity inputs (0.2 kWh ha⁻¹) seem unrealistically low compared with typical Mediterranean irrigation energy use (usually tens–hundreds kWh ha⁻¹ yr⁻¹). Verification or correction is needed.

Another big issue to me is related to Carbon Uptake and Biogenic Carbon Accounting. The authors’ treatment of climate change impacts appears incomplete, as it excludes biogenic carbon uptake and storage in olive biomass and soils. Olive trees are perennial and long-lived, and a significant share of their carbon exchange occurs through photosynthetic CO₂ fixation in trunks, branches, leaves, roots, and soil organic matter. By modeling only emission-side processes (fertilizer production, diesel combustion, irrigation energy, etc.) under the ReCiPe 2016 midpoint method, the authors effectively report gross GHG emissions rather than net life-cycle balances. This approach may overstate the climate burden of all systems, particularly the traditional and high-density rainfed groves where long-term carbon sequestration can offset a meaningful fraction of emissions.

I will recommend that the authors should clarify explicitly whether CO₂ removals were excluded or considered negligible. If omitted, the authors are encouraged to:

1. Quantify annual and cumulative carbon uptake using established references (e.g., González-Sánchez et al., Agriculture, Ecosystems & Environment, 2012; Baldantoni et al., Science of the Total Environment, 2019) for above- and below-ground biomass accumulation in olive systems.
2. Incorporate biogenic CO₂ flows into the inventory (CO₂ uptake to biomass and soil) and apply climate change characterization factors consistent with ISO 14067 or IPCC AR6.
3. Discuss the temporal dimension of carbon storage, distinguishing short-term (annual litter, prunings) from long-term (tree biomass, soil carbon) pools.
4. Report both gross and net GHG results, as this would more accurately reflect the mitigation potential of olive groves and improve comparability with other Mediterranean LCAs that include biogenic carbon.

Without such accounting, the study cannot claim to assess the overall climate performance or “environmental sustainability” of the systems analyzed, since a central carbon sink process inherent to perennial crops remains unrepresented.

 

The results tables are detailed but occasionally repetitive. My key concerns are:

• The discussion does not quantify relative uncertainty or conduct sensitivity checks on fertilizer rates, irrigation water, or yield. This weakens confidence in cross-system ranking.
• The claim that alternative (sustainable) systems sometimes perform worse is interesting but not explored, the authors should explain whether this results from higher organic input rates, lower yields, or different allocation rules.
• The link between environmental results and practical management recommendations (e.g., irrigation optimization, nutrient recycling) is sound but should be backed by data or references rather than broad statements.

 

The authors cite many Mediterranean LCA studies but lack synthesis.

• Recent dynamic or consequential LCAs (post-2021) addressing olive intensification, energy use, or circularity could be added.
• The discussion could be reorganized around drivers of impacts (fertilization, irrigation, mechanization) rather than merely restating system rankings.

5. Figures and Tables

• Figure 2 is informative but crowded. Consider summarizing main comparisons through normalized impact scores or radar plots.
• The term “standard vs. alternative” would benefit from consistent labeling (currently alternates between “STS/nSTS” and “standard/alternative”).

 

The manuscript contains stylistic redundancies and translation artifacts (e.g., “Face to previous studies,” “Plantig Stage”). A careful language edit is required. Sections 4 and 5 should be merged into a single “Results and Discussion” to reduce repetition. Some sentences in the abstract and conclusion could be more concise and less promotional (“make agriculture a force for environmental recovery” sounds editorial rather than scientific).

The authors acknowledge the lack of social and economic dimensions, which is commendable. However, the conclusion could more explicitly list current study limitations:

• small and region-specific sample (six plots),
• exclusion of yield-based FU,
• omission of uncertainty analysis,
• potential underestimation of irrigation energy.

These should be transparently presented as boundaries of inference.

Author Response

We would like to sincerely thank the reviewer for the time dedicated to evaluating our manuscript (sustainability-3975619). We found the comments very constructive and believe they have substantially improved the quality of our work. The revised version has been modified to address all the points raised. We are submitting the manuscript, an appendix containing a figure, and our responses to the reviewer's questions.

I remain available for any further clarification.

Best regards,
Rachel Hermeto

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I believe the authors should review recent literature that supports this work.

For example: Assessing the environmental sustainability of Portuguese olive growing practices from a life cycle assessment perspective.

Regarding lines 120-136 on page 3, is it necessary to comment on this in the introduction section? I don't think so.

Section 2, "The Case Study," should be part of the methodology description.

The data collection source for Table 1 could be included in the supporting information or data. This information should explain the question-and-answer strategy used.

The authors should review their use of acronyms.

Author Response

Dear, reviewer

We would like to sincerely thank the reviewer for the time dedicated to evaluating our manuscript (sustainability-3975619). We found the comments very constructive and believe they have substantially improved the quality of our work. The revised version has been modified to address all the points raised. We are submitting the manuscript, an appendix containing a figure, and our responses to the reviewer's questions.

I remain available for any further clarification.

Best regards,
Rachel Hermeto

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The article assesses the environmental impact of various techniques and processes used in olive production in Portugal. This is an important issue due to the growing level and intensification of production, so that it does not have a devastating effect on soil, climate and water. My general comment is as follows: Can it really be concluded at the outset of the research that a given technology is recommended/proposed? It would seem that all technologies should first be assessed (indicators examined) and only then, on that basis, can it be determined which technologies are better for the environment and which are worse. Perhaps the authors could rephrase these issues to make them clearer to the reader. Below are my detailed comments on the text.

 

Title

I think it should be either assessment or analysis, not both words at once. Perhaps it should be changed to an analysis of the environmental impact of different olive grove systems? In addition, the name of the country in which the region is analysed should be added in brackets at the end.

 

Adres

L6 – the country should be added

 

Abstract

It should be significantly shortened to 200 words; currently, the same information is repeated twice. My comments below actually apply to both texts.

L14 – I suggest removing the word “sustainable” here, as some of these techniques have a fairly significant impact on the environment, so I am not sure if they can be described as such.

L17-18 – the highest/the best – a consistent scale should be used here – either the highest/the lowest or the best/the worst.

 

Keywords

I suggest verifying them so that they do not repeat the title, then the article will have a better chance of being found in article databases.

 

Introduction

L62 – isn't 20% of the total area of the country (Portugal) a mistake?

L97 – ‘Espadas-Aldana, 2019’ – there is no such item in References

L109 – the term ‘in addition’ is unjustified, as there is no information about the advantages of this article earlier in the text, only here

 

The case study

L141-150 – this text introduces confusion. Since this division does not apply here, it is unnecessary, but it can be used in the discussion of the results. In addition, this division is not very clear – EXISTING plots are divided into STS and nSTS groups, and then the authors write that STS are PROPOSED technological alternatives. So are we considering existing plots or alternatives? This should be clarified so that there is no doubt.

L154-156 – again, this division is unclear. Existing plots are divided into standard or alternative, while alternative technologies are only proposed, i.e. I understand that they have not yet been introduced. What is going on here? Or is EVERY plot considered in two variants – the current one and the improved one, to make it better for the environment?

Table 1 – planting stage is not a proper noun, so it does not require capital letters. In addition, there are typos in some cases (plantig, fluroxypyr e flazasulfuron). Livestock integration – I do not understand the basis for entering yes/no. I understand yes in the case of sheep (QSAS), but why yes in the case of VDA and CVA? I guess it is not a matter of manure, because it is used everywhere. Please check the correctness of all yes/no entries again.

 

Methodology

L168-173 – such texts should not be left unattached to any subsection. I suggest moving it further, as the second paragraph of subsection 3.1. Furthermore, there is no clear reference to the fourth stage here.

L186-187 – I do not quite understand this sentence, please explain it in more detail.

L190-191 – please add the terms “traditional production” and “irrigated plots” to this sentence

Fig. 1 – one research area is missing

L203-205 – phytosanitary is also absent in CVA. OK, this is written further on

L205-206 – not only QSAS, because VDA also has pruning and harvesting only during FPS and DS. OK, this is further explained. In that case, please correct the entire description L201-212, as there are many inaccuracies and fragments of descriptions that do not match Table 2.

L219 – here there is information about both inputs and outputs, while further on (e.g. Table 3) there are only references to inputs

Table 3 – why is diesel in kg? Typo (eletric). If the hours of equipment operation are given for pruning and harvesting, why are they not given for the other categories of work? The table lacks data for explantation, transport and excavation.

L224-228 – this would be more appropriate as text before the table, rather than after it, although the question arises as to whether it is necessary at all, as the types of operations have already been mentioned earlier

L231 – typo (should be World)

L238 – ReCiPe 2016 v1.01 – citation missing here and in References

L240-245 – in Fig. 1, olives are also listed among the outputs; shouldn't this also be analysed as part of the impacts generated by olive groves? Would it not also be valuable to refer not only to 1 ha, but also, for example, to 1,000 kg of olives – how much energy, water, fertilisers, etc. does their production consume depending on the technology used?

 

Results

L291-294 – this is part of the discussion of the results and should be included in the next chapter

L298-302 – is the lowest value for the MEU for No Production Stage ultimately in the case of QSAS or CVA? There can only be one lowest value for NPS

Table 5 – please specify the units in the column headings (as in Table 4)

Fig. 2 – I suggest giving the titles ‘Climate Change’ etc. to the individual graphs (above the bars), because the markings ‘2a) CC’ are difficult to read and, in addition, are not explained. In the last sentence of the Figure description, replace “e” with ‘and’. The chart legends include the term ‘power sawing’, which the authors have not used previously when describing agricultural operations – please be consistent. The use of very similar colours for Harvesting and Irrigation means that the boundary between them is not visible on the bars.

L323 – which plots does this 97% refer to? This should be added here due to the difference between QSAS and CVA plots in this respect.

L329-330 – this is not entirely true; in several charts, e.g. in the NPS phase, it has a smaller share compared to other operations. Unless it is a comparison between QSAS, CVA and VDA, but that would not be true either, looking at the results for MEU.

L335-337 – comparing the share of orange for the VDA and CVA bars, it seems to me that this impact is quite comparable, please recalculate this.

L347 – this percentage depends on the stage of production; the description here (and earlier) is a little too simplified and imprecise. The impact of pruning is also quite visible in some cases in VDA and CVA plots.

L350-351 – this only concerns Climate Change, please clarify

L355 – stage D is an exception, which the authors did not mention

L356 – how are these percentages calculated? If we take into account the entire process (6 stages), it will not be 96% (in stages PS and D it is 0%). Please explain this in detail (preferably at the beginning of the description of the results or in the description of the methodology), because the descriptions do not match the original graphs

 

Discussion

Once again, I would like to emphasise my doubts about dividing the individual plots into standard and alternative right at the outset. Rather, it should be decided during the discussion of the results which methods/processes are considered better/safer and therefore PROPOSED for wider application. Furthermore, a large part of the discussion consists of repeating the results; it would be better to provide a broader commentary on them, their interpretation, with references to the literature.

L373/374 – information on olive productivity should also be included in the results (or earlier, in the description of plots), as this is also very important information needed to form a complete picture of a given olive production technology

L382-383 – what is the QSAS performance in olive production?

L383-385 – there are typos and a poorly constructed sentence

 

Conclusions

L434 – we know nothing about these yields, as there was no information on this subject in the article

L445-448 – but olive production efficiency is probably lower, which the authors unfortunately did not mention. I am increasingly convinced that it would be better to assess the environmental impact of individual techniques in terms of the weight of olives produced. Please consider this! And in this text, please at least refer to this as an alternative, if it is feasible, of course.

L452 – which plots/production systems are the most sustainable in this case? Please specify this clearly.

Comments on the Quality of English Language

The text requires review for accuracy and style; I have included some comments in the review text.

Author Response

Dear, reviewer

We would like to sincerely thank you for the time dedicated to evaluating our manuscript (sustainability-3975619). We found the comments very constructive and believe they have substantially improved the quality of our work. The revised version has been modified to address all the points raised. We are submitting the manuscript, an appendix containing a figure, and our responses to the reviewer's questions.

I remain available for any further clarification.

Best regards,
Rachel Hermeto

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Several comments have been acknowledged, and some clarifications and additions have been incorporated into the manuscript. However, a number of core methodological issues remain insufficiently addressed, and some responses introduce new concerns about scientific rigor, transparency, and interpretability. The main points of assessment are summarized below.

The response elaborates on the structure of the Sustain olive project but does not directly answer the reviewer’s core question regarding the specific contribution of this manuscript. While contextual information is useful, the reply should more clearly explain the manuscript’s distinctive contribution within the broader project framework.

The addition of yield data is noted, but the justification for retaining a hectare based functional unit remains weak. Because productivity varies significantly across orchard densities, excluding yield based impact indicators continues to limit the robustness and interpretability of the sustainability comparison.

The authors acknowledge the ambiguity between “olive production” and “olive oil production” and have revised the text. This is a positive change.

The authors state that statistical treatment is not feasible due to heterogeneous farm practices. However, even simple ranges or qualitative uncertainty discussion would support transparency. Presenting no uncertainty information remains a concern.

The rationale for modelling repeated cycles over 100 years remains insufficiently justified. The reviewer’s concern about potential distortions is not resolved, as the manuscript still does not present a time weighting rationale beyond averaging values.

The explanation that irrigation energy is supplied under pressure by a central system is plausible, but no verification or reference is provided. Given the unusually low reported energy use, documentation is still recommended.

The authors confirm that biogenic carbon uptake was not included because related experiments are unpublished. While it is acceptable to list this as a limitation, the omission of all CO₂ removal processes in perennial orchards is a fundamental methodological gap that significantly affects climate change results. This remains the most serious unresolved issue. Without at least a bounding estimate or literature based values, the manuscript cannot claim to reflect overall climate performance.

The reviewer’s suggestions to reorganize the discussion and deepen the analysis were not implemented. The manuscript still does not clearly explain why “alternative systems” perform worse in certain categories, nor does it adequately connect impact drivers to management implications. These omissions weaken the explanatory value of the results.

The authors have added the requested limitations, which improves transparency. However, several limitations, particularly those related to biogenic carbon and the functional unit, are too significant to be listed without deeper methodological adjustment.

Author Response

Dear reviewer,

 We sincerely thank you for the careful evaluation of our manuscript and for the valuable and constructive comments. We have carefully considered all the suggestions and have made our best efforts to address them in the revised version of the manuscript. We believe that these modifications have improved the clarity, robustness, and overall quality of the paper.

We greatly appreciate the time and effort dedicated to reviewing our work and the helpful guidance provided throughout the review process.

Best regards,

Rachel Hermeto

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have taken all comments into account; the current version can be accepted.

Author Response

Dear Reviewer 2,

We sincerely thank you for the careful evaluation of our manuscript and for the positive feedback. We greatly appreciate the time and effort dedicated to reviewing our work and the constructive comments provided throughout the review process, which have significantly contributed to improving the quality and clarity of the manuscript.

Best regards,

Reviewer 3 Report

Comments and Suggestions for Authors

The article has been significantly improved, but there are still some gaps. General comments: citations in the text should be numbered consecutively starting from 1; there is no reference to Appendix 1 in the text, this should be added. Below are detailed comments on the text; the line numbering refers to the version of the text with visible changes (the file I received from the editor).

 

Title

Is the last ‘of’ really necessary?

 

Abstract

As I mentioned earlier, it should be significantly shortened to 200 words. Despite my earlier comment, the same information is still repeated twice. The text from the word CONTEXT to the end should be deleted.

L15 – please remove the word ‘sustainable’ because some of these techniques are not sustainable, as the authors explain further in the text. ‘Different technological solutions’ is sufficient here.

 

Methodology

L172-187 – there are still inconsistencies and illogicalities in this text. Please look at this set of quotations: "The Sustainolive project compared the plots to be analysed and created an index to separate the plots into non-sustainable technological solutions (nSTS) and sustainable technological solutions (STS). The former are current technological practices in the Alentejo region‘ – which means that, theoretically, all plots in this region, including those selected by the authors, should be classified as nSTS, but they are not. And the second quote: ’Therefore, the plots were separated and classified as standard and alternative. The former are standard technological practices in the Alentejo region and the latter are the proposed technological alternatives based on agroecological methods." – since they are only PROPOSED, it means that they have not yet been implemented and are not functioning, so how could the authors examine them? Once again, I ask for very precise writing so that there is no doubt about what is meant.

Table 1 – there is still a typo (fluroxypyr E flazasulfuron). If there are sheep in the QSAS plot, why does the Organic fertilisation row say ‘No’? Surely this is a natural consequence of the presence of animals?

L239-250 – this text is quite chaotic, please rework it a little so that there are comprehensive descriptions, e.g. by operations (i.e. the entire comment on soil operation; then the entire comment on Fertilisation, etc.); currently it is mixed up.

Table 3 – there is still a typo (it should be electric, not eletric). Since the working hours of the equipment are given for pruning and harvesting, why are they not given for the other categories of work? The table still lacks data for explantation, transport and excavation!

 

Results and Discussion

L353 – please add the word TRADITIONAL before the abbreviation VDA to show that the results from this group of plots are being compared

After L383 – there is a paragraph missing here, in which the alternative plots themselves are compared!

L447-448 – this is not entirely true; in several graphs, e.g. in the NPS phase, it has a smaller share compared to other operations. Unless it is a comparison between QSAS, CVA and VDA, but that would not be true either, looking at the results for MEU. In response to the first review, the authors agreed with my comment, but unfortunately did not correct anything in the text.

L451-452 – ‘In traditional orchards, OUR STUDY APPLIED less fertiliser than other studies’ – this is too much of a simplification, as is the case in the rest of the text added below. It is not the study that applied it, but the farmers.

L464 – ‘align closely for phosphorus’??? The authors' results for P2O5 are 67, while Sales' results are 240! So where is the close similarity?

L506 – as I wrote earlier, this percentage depends on the stage of production; the description here (and earlier) is a little too simplified and imprecise, and should be supplemented. The impact of pruning is also quite visible in some cases in VDA and CVA plots, which the authors also failed to mention.

L509-510 – as I wrote in my previous review, this only concerns Climate Change, please clarify this in the text.

L513-514 – the authors did not write that stage D (Disposal) is an exception to the negative impact of irrigation, which is what I meant in my previous review.

L514-515 – please use the sentence from the response to the review here (‘To the freshwater eutrophication category, the MNA plot makes a significant contribution of 96% (no production stage and increasing stage), compared to other operations occurring in this plot’).

 

Appendix 1

Since there is no Figure 1 here, any figure numbering should be removed, and only one title with an explanation of abbreviations should be used. The figure has not been corrected despite specific comments from the first review. To improve the readability of the graphs, I recommend giving titles such as ‘Climate Change’ etc. to individual graphs (in the space above the bars), as the markings ‘2a) CC’ are difficult to read and, moreover, are not explained. In the last sentence of the Figure description, replace the Portuguese “e” with ‘and’. The use of very similar colours for Harvesting and Irrigation means that the boundary between them is not visible on the bars. This should be changed because it is illegible. If, according to the authors' explanations, ‘power sawing’ is related to pruning, why are they separate categories in the graphs and not one?

Author Response

Dear reviewer,

 We sincerely thank you for the careful evaluation of our manuscript and for the valuable and constructive comments. We have carefully considered all the suggestions and have made our best efforts to address them in the revised version of the manuscript. We believe that these modifications have improved the clarity, robustness, and overall quality of the paper.

We greatly appreciate the time and effort dedicated to reviewing our work and the helpful guidance provided throughout the review process.

Best regards,

Rachel Hermeto

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

The article has been significantly improved. However, the massive changes in Table 7 in the results section are surprising. Please explain them to the editors, as they raise doubts, especially since the further description of the results and the graphs in Appendix 1 have not been corrected. Below are my remaining detailed comments on the text.

 

Methodology

L189 - are recent technological PRACTICES…

L247-248 – this sentence should be deleted (Moreover, QSAS only presents operations of pruning and harvesting in the Full Production Stage and Decreasing Stage.), because this information is provided in an even more complete form in the following sentence

L253 – I suggest adding (Explantation, Transport, Excavation) at the very end in brackets.

Table 3 – there is still a typo (it should be eleCtric stick, not eletric stick). The table still lacks data for explantation, transport and excavation.

 

Results and Discussion

L422-442 – please move this section BEFORE the newly added text on biogenic CO₂ (L389-419), as it fits better into a coherent whole analysis

Table 5 – the source should be given in numerical form

Table 7 – what does CC/GW mean in the column header? Until now, it was just CC. Where did such massive changes in the results contained in this table come from? This is very disturbing

L540-651 (+ appendix 1) – as a result of the radical changes in the results in Table 7, should all these results/descriptions/graphs also be corrected? At this point, it is difficult for me to comment on the accuracy of the text of the results and conclusions.

L555 – In the terrestrial ACIDIFICATION category...

 

Appendix 1

Should this appendix be amended as a result of the changes in Table 7?

Author Response

Dear Reviewer,

We sincerely thank you for your careful review and valuable comments. We have made every effort to provide detailed responses to your questions and have implemented the requested modifications. We hope that the changes address your concerns satisfactorily. Please do not hesitate to contact us if any further clarifications are needed.

We greatly appreciate your time and effort in helping us improve our work.

Sincerely,

Rachel Hermeto

Author Response File: Author Response.pdf