Environmental Assessment of Pig Manure Treatment Systems through Life Cycle Assessment: A Mini-Review

Round 1

Reviewer 1 Report

The topic of your review is timely and interesting. But, it is difficult to read your paper owing to the poor English and unclear description. I have judged major revision is required before accepting your paper. The followings are your weak and unclear points．Please revise your paper by taking into account the following my comments.

1.      English is poor. Native check is required. There a lot of repeated words and phrases.

(avoiding, in which etc.)

Do not use first person(we) in the text.

2.      Table 1  Please add the “Study No.” at the top item.  You need not describe all authors names. It is better to write first author name only. For example, Wang, X. et al.. It is better to show the reference number at the last item.

3.      Table 2  Please mention the fermentation clearly. Is this fermentation the acid fermentation? I could not understand the “draft beer” . It is better to change “Anaerobic fermentation” in way of treatment in Study 2 to “Anaerobic digestion”

4.      Table 3, 4, 5 and 6  Please add the “Study No.” at the top item.

5.      You must explain the “x” at the footnote of the Table.

6.      I advise you to show the treatment scenario in “block chart” in Table 6 or in the text.

7.      The proper nitrogen removal of pig manure is the urgent problem which should be solved. You have only focused on the phosphorous removal in this review paper. You must consider the nitrogen removal of pig manure for reducing the eutrophication risk caused by nitrogen.

2． English

ü  Line 2 　sistem →　system

ü  Line 49 　reconciled →　harmonized

ü  Line 61   study →  review paper

ü  Line 67  Materials and Methods → Methodology

ü  Line 130-134  Please check this long sentence.

ü  Line 239  wash water → washing water

ü  Line 275  fugitive ??

ü  Line 311  (CHP) ??

ü  Line 494  no.1 → No.1

ü  Line 514  Cen Ⅱ→　SceⅡ

English is poor. Native check is required. x

Author Response

Dear Reviewer

We are very thankful for the careful review and constructive suggestions by the Reviewers and by the Editor. It is our belief that the manuscript is substantially improved after making the suggested edits. Following are the Editors and Reviewer comments and point-by-point responses, including how and where the text was modified. The revision has been developed in consultation with the co-authors, and each author has given approval to the final form of this revision. We very much hope the revised manuscript will be finally accepted for publication in Sustainability.

Author Response File: Author Response.pdf

Reviewer 2 Report

see the files

Comments for author File: Comments.pdf

The English in the manuscript has significant room for improvement. While the overall message is generally understandable, there are frequent grammatical errors, awkward sentence structures, and unconventional word choices that detract from the clarity and readability of the text.

Some specific issues I noticed:

1. Inconsistent verb tenses within sentences and paragraphs.

2. Misuse of articles (a/an/the).

3. Incorrect preposition usage.

4. Lack of subject-verb agreement in several sentences.

5. Run-on sentences that should be divided into smaller, clearer sentences.

6. Overuse of passive voice, which makes the writing less engaging.

7. Occasional misuse of plurals and singular/plural inconsistency.

8. Some unclear antecedents for pronouns.

Author Response

Dear Reviewer

We are very thankful for the careful review and constructive suggestions by the Reviewers and by the Editor. It is our belief that the manuscript is substantially improved after making the suggested edits. Following are the Editors and Reviewer comments and point-by-point responses, including how and where the text was modified. The revision has been developed in consultation with the co-authors, and each author has given approval to the final form of this revision. We very much hope the revised manuscript will be finally accepted for publication in Sustainability.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript entitled: "Environmental Assessment of Pig Manure Treatment Sistems Through Life Cycle Assessment: a Literature Review" compiles the LCA results from 10 recent papers aiming to update the more recent and effective practices for a proper management of pig manure. 

I suggest that for this manuscript to be published as a scientific article in the Sustainability journal, the authors must expand their search and the papers they assessed, besides restructuring it and improving the Discussion and the Conclusions.

My first and more specific question is: why the search was limited to 'manure' and did not include 'slurry'? This probably limited a lot the number of papers available. 

The scope and the aim of this study is relevant, however, I feel like the topic 'treatment of pig manure' is broader than the only 10 papers summarized in this manuscript, which were mainly from Brazil and China. I strongly believe that the most advanced techniques of slurry treatment are in the EU, specially in countries as the Netherlands, Belgium, and Denmark. A lot of studies have been published recently in this topic from different research groups in these countries and none is cited or assessed in this manuscript. 

For instance, surprisingly, the authors do not mention at any moment potential ammonia emissions during storage and field application, and the use sulfuric acid for acidification to avoid that. This practice has been adopted in countries as Denmark since early 2000s and listed by the EU among the best available techniques for slurry treatments. There are many studies on this topic, including LCA in different European regions and some with focus in Portugal. Just to make clear that I am not involved in any of these studies and have no collaborations with the Portuguese groups, but as I work in the field of biowaste management in the EU, these are topics that are well known and should be considered in this study. 

In addition to that, this manuscript is very descriptive, non-conclusive, and, therefore, lacks novelty. The results section describe the main findings, as it should be, and this is fine. But, for instance, the discussion has 3 paragraphs and only 1 reference. The 'literature review' consists of only 10 papers plus other 10 basic references cited in the text. Moreover, the Conclusions is basically a summary of the main findings, lacking the novelty of the work. 

For instance, the last sentence:

"These results show that anaerobic digestion is an environmentally friendly technology that can be essential for a future energy transition in Europe."

1. This is already well-known, and, as previously mentioned, EU countries (Northern specially) already adopt this and even other technologies that are more 'environmental friendly'.

2. Most of the studies cited in this manuscript are not from Europe... 

The English and the written part must be improved. Therefore, I recommend the authors to proofread it again line-by-line and make the adequate changes.

In the title: Sistems should be replaced by Systems 

For instance, in the first sentence of the abstract:

"The main objective of this study is to review the literature on studies published pig waste treatment technologies the last five years on."

It has to be rewritten as:

"The main objective of this study is to review the literature on studies published on pig waste treatment technologies in the last five years."

Author Response

Dear Reviewer

We are very thankful for the careful review and constructive suggestions by the Reviewers and by the Editor. It is our belief that the manuscript is substantially improved after making the suggested edits. Following are the Editors and Reviewer comments and point-by-point responses, including how and where the text was modified. The revision has been developed in consultation with the co-authors, and each author has given approval to the final form of this revision. We very much hope the revised manuscript will be finally accepted for publication in Sustainability.

Author Response File: Author Response.pdf

Reviewer 4 Report

1. It is advisable to complete the review of environmental assessment of swine manure processing systems through a life cycle assessment by developing a classification of the systems under study according to any selected classification criterion;

2. It is advisable to present the obtained results of analytical studies in the form of a graphical dependence of the studied treatment systems found in selected studies for the main categories of impact;

3. In Table 2 of the manuscript it is advisable to indicate the technical means used to obtain the product;

4. Perhaps it makes sense for the reader of this article to indicate in Table 1 a separate column indicating the name of the journal in which the submitted manuscript was published.

Author Response

Dear Reviewer

We are very thankful for the careful review and constructive suggestions by the Reviewers and by the Editor. It is our belief that the manuscript is substantially improved after making the suggested edits. Following are the Editors and Reviewer comments and point-by-point responses, including how and where the text was modified. The revision has been developed in consultation with the co-authors, and each author has given approval to the final form of this revision. We very much hope the revised manuscript will be finally accepted for publication in Sustainability.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

You have improved your paper properly by taking into account my comments. I have judged your paper reached to the acceptance level of “Sustainability”.

Reviewer 2 Report

All comments are addressed. well done.

English is fine.

Reviewer 3 Report

The authors managed to make the required revisions. It can be accepted.

IT's fine, I advice the authors to proofread line-by-line, to make sure there are no typos.