Assessment of the Carbon Footprint of Large Yellow Croaker Farming on the Aquaculture Vessel in Deep Sea in China

Round 1

Reviewer 1 Report

General comments:

1a. The first part of introduction is quite long, and the explaination of the actual topic of the manuscript is reported only in the last paragraph. Please rearrange

1b. the manuscript is hard to read in some of points of the materials and methods and discussion. I suggest to making the explaination of the different equation as pointed list

Furthermore, the discussion in lines 338-349 is not well readable.

2. attention to the abbrevations, to be stated at the first time when they are used

3. all the statistical analysis reported in results and discussion has to be stated in materials and methods. Moreover: the origin of the hypothesis values?

4. no data about EF (kg single greenhouse gas / kg input) is reported

5. table 3: no studies after 2018?? (except Ulf Johanes)

Specific comments

lines 26-30. A citation is needed

line 99. Why IPCC 2006 and not IPCC 2019?

lines 114-115. the functional unit is "1 kg", whereas co2-eq emission is the impact assesed (related to the impact category "glowal warming potential" or "climate change")

lines 133-136. The diet composition is not clear

lines 383-389. Some citations are needed. See for example Bordignon et al. 2022, https://doi.org/10.1016/j.aquaculture.2022.738264, and Yacout et al 2016 

• https://doi.org/10.1007/s11367-016-1061-5

•  

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript. The revised version for the article (jmse-2947107) has been completed.

The point-by-point response to your comments refer to the attachment. Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Reviewer 2 Report

1 – The very large vessel for farming fish at sea is an extremely interesting topic as the strategy is likely to expand and spread internationally.

2 – The detailed appraisal of the various phases of rearing is appropriate and contributes to the accuracy of the results.

3 – Table 3 is long and not tightly organized.  The authors should consider creating a tighter system of subcategories to make the table easier to read.

4 – The shading on the circular graph causes the print to fade into the background toward the edges. Suggest keeping the graph style but redoing the color.

5 – The comparison of the different aquaculture operations is interesting and a valuable result. 

6 - Some further discussion of the comparability of the studies cited is appropriate. A few sentences on possible issues with methodology and variance might help.  How accurate are these studies?  Are any factors likely to skew the comparison?  

1 – The word “furtherly” is not correct in the abstract.  “The seafood have” line 30 is not a usual English structure. “Seafood has become…” is the usual as seafood is singular.

2 - Some articles like "the" are missing. Watch singulars and plurals. 

This needs one more careful edit of the English to clean up a few minor omissions and syntax issues.  

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript. The revised version for the article (jmse-2947107) has been completed.

The point-by-point response to your comments refer to the attachment. Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

I read the ms Study on Carbon Footprint of large Yellow Croaker Deep Sea Breeding on Aquaculture Vessel in China.

In my opinion there are major issues to be addressed. Minor issues can be evaluated in the next review round.

1. The research is overly too specific and the objective is not framed within a research context. This is highlighted by authors across the ms, up to the discussions (for example lines 397-399). Authors should clarify the research objective and how the case study is of wider research interest.

2. Research design and use of terminology. the research design should be clearly presented at the beginning of the methods section, to enable readers' understanding. in the current ms text, it is not clear how the CF was conceived within the broader LCA framework, system boundaries (are background processes considered? what are their sources?) and functional units require better specification, data and clarification of data collection procedures should be made explicit to enable replication. Attention should be paid to terminology (example, "survey questionnaire")

3. Results: The lack of clear objectives and methods affects this section the looks a bit messy. for example, the literature review should be presented in the results section (interpretation phase of the LCA framework). The discussions should build on lessons learnt from the cases study and offering a recommendations of wide interest. I suggest having the discussions in a dedicated section

The ms is readable. I suggest English poof reading of the final version of the final version of the ms, after all revisions' rounds are completed

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript. The revised version for the article (jmse-2947107) has been completed.

The point-by-point response to your comments refer to the attachment. Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Reviewer 4 Report

Your paper is a study of the carbon footprint (CF) of the deep sea culture of yellow croaker in an aquaculture vessel in China. Your findings are that “the CF of the aquaculture vessel was lower than the CF average level of the closed aquaculture systems. In order to bring down the carbon footprint of large yellow croaker breeding process furtherly, some suggestions were put forward, such as adjusting the energy structure, improving energy efficiency, improving feed ratio, and optimizing the feeding mode” (lines 17-21).

I am a social scientist, not a natural scientist, so I cannot evaluate the mathematical analysis in your paper. However, I have three reservations about the would like you to respond to the following comments before I recommend your paper’s  publication.

First, there are some infelicities of English expression that need to be dealt with by a native English speaker.

Second, you set out to assess the carbon footprint of the entire life cycle of yellow croaker deep sea breeding:

“The carbon footprint calculation method of large yellow croaker breeding on aquaculture vessel was established, and the whole life cycle was divided into four processes: feed production (FP), fingerling breeding (FB), adult fish culture (AC) and fish product distribution (PD)” (lines 9-12).

But you omit two important elements of that cycle – (1) the CF of adult fish culture (AC):

“Due to the maximum total number of water exchanges reaching to 16 times per day in the culture tank, there was almost no sludge and residual feed staying in the culture tank, and the conditions for heterotrophic denitrification and anaerobic reaction were not available in the culture tank, so the CF of AC [adult fish culture] process is not assessed in this study” (lines 173-177)

Surely your analysis is seriously incomplete without assessing that element?

(2) the exclusion of the construction of aquaculture facilities. In Section 3.2. “Comparison of CF of Marine Fish Culturing under Different Modes” you state:

“It referred to the research literatures on the CF of mariculture, and selected the research literature which adopted the LCA method and evaluated from the beginning of feed cultivation to the end of aquaculture (before), excluding the construction of aquaculture facilities, processing and packaging, distribution and other processes” (lines 318-321)

Why have you excluded the calculation of the carbon footprint (CF) construction of aquaculture facilities? Is it not a vital part of estimating the CF of a whole life cycle of fish farming that you take account of the CO2 emissions incurred in constructing the production vehicle which is used to grow the fish? If you did calculate the carbon footprint of constructing Aquaculture Vessel Guoxin No. 1 and compare it with the carbon footprint of the other methods of growing yellow croaker, would you not expect to find that the CF of this vessel’s whole production cycle vastly exceeded the CF of any of the other methods? Does this consideration not undermine your main finding that “the CF of the aquaculture vessel was lower than the CF average level of the closed aquaculture systems”?

You seem to allude to this issue in Section 3.3 when you write the following:

“"Guoxin No. 1" is the first 100,000 tons of aquaculture vessel in the world, and also the only currently operating large-scale aquaculture vessel in our country, therefore, the data of vessel actual service life is not available, and the design data would be yet to be verified. Besides, the CF measurement of the construction and use process of aquaculture equipment on board had not yet been carried out. So, this project will conduct further research in order to objectively evaluate the advantages and disadvantages of aquaculture modes” (lines 397-403).

The yellow highlighted passage implies that you intend to conduct future research into the CF of the construction of aquaculture equipment, including Guoxin No. 1’s construction Until you do so, are not your current findings premature and incomplete? How can you claim you have conducted a whole life cycle when two major components of that cycle are missing?  

There are some infelicities of English language that need to be corrected

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript. The revised version for the article (jmse-2947107) has been completed.

The point-by-point response to your comments refer to the attachment. Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

the article can be published.

Just I think some text editing is required, for example I suggest not using acronyms in paragraph headings. also citation style should be checked

I think that the ms is well understandable, then just minor text editing is required

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript again. The second modified version refers to the attachment. Moreover, the point-by-point response to your comments as follows:

 Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Reviewer 4 Report

Your response to my criticism that you fail to take into account any calculation of the carbon footprint of the construction of the huge aquaculture vessel is not adequate. You say the following: 

 "Guoxin No.1" is currently the only large-scale deep-sea aquaculture vessel in operation in China. Based on its operational performance, it achieves breeding densities 4 to 6 times higher than traditional cages while maintaining a survival rate exceeding 95%. Additionally, its design service 3 life exceeds 20 years which significantly reduces environmental costs associated with unit breeding bodies. Therefore, the construction process of aquaculture boats has been excluded as it makes trivial contributions to the final result"

How can you claim the carbon footprint of aquaculture boats is 'trivial' when you have not provided any figures to demonstrate its quantity? This is not science but guesswork, and it undermines the validity of the assertion in your revised Abstract that "Results showed that the carbon footprint (CF, kgCO2e/kg LW) for the complete life cycle amounted to 6.0375 kgCO2e/kg LW, while the CF per unit economic value of “Guoxin No.1” large yellow croaker was estimated at 30gCO2e/CNY". Until and unless you include the CF of the vessel's construction, you cannot claim to have computed the CF of the entire life cycle of the production process. 

Some infelicities of English expression remain. 

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript again. The second modified version refers to the attachment. Moreover, the point-by-point response to your comments as follows:

Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Round 3

Reviewer 4 Report

Thank you for adding a section on the carbon footprint of ship construction. However, in that section you say the following:

 “2.4.2 Process of ship construction. The SC process of aquaculture vessel encompassed the ship construction, as well as the production and transportation of construction materials. Referring to previous studies by Li B.Y. in 2009[27], Li B.Y. et al. in 2010[21], Nicolae et al. in 2014[28], Nathanael Koand et al. in 2016[22] and Ailong Fan et al. in 2023[23], it was found that the CF attributed to ship construction accounted for 0.32%, 4.92%, 87.71%, 4.46% and 4.64% of the CF throughout the entire life cycle (excluding ship dismantling) respectively. After excluding discrete values, the ratio between CF of the construction process and CF of the whole life cycle ranged from 4.4% to 5.0%. This study used the ratio value of 4.7%” (lines 173-182)

So your calculation of the carbon footprint of the ship construction of the 100,000 tonne vessel Guoxin No 1 is based on the average figure of the carbon footprints of the ship construction of other vessels calculated by previous researchers. But how do we know that that average figure is accurate for Guoxin No 1? The previous researchers might have been calculating the carbon footprints of much smaller vessels. You cannot just assume that their figures are appropriate for Guoxin No 1: you must prove that their figures are appropriate for Guoxin No 1. 

Author Response

Dear Reviewer,

I am deeply grateful for the invaluable suggestions you have provided me with regarding my manuscript again. The third modified version refers to the attachment. Moreover, the point-by-point response to your comments as follows:

Thank you.

Kind regards

Fei Fan

Author Response File: Author Response.pdf

Round 4

Reviewer 4 Report

Thank you for your speedy response to my last query. You have addressed my concern and I am happy to recommend publication of your paper. Can you tell me whether it is standard practice not to include the carbon footprint of the dismantling of the ship in the calculation of the carbon footprint of the whole life cycle of vessel-based aquaculture production systems? In the case of nuclear power, I believe it is standard practice to include the environmental cost of decommissioning nuclear installations in calculations of their whole life cycle impact.

Fine