Assessment of the Seasonal Potential of Macroalgae and Grass in the Sea of Azov for Methanogenesis and Optimization of the Digestate’s Carbon/Nitrogen Ratio

Round 1

Reviewer 1 Report

In introduction:

1.      The idea of using seaweeds and seagrass was suggested for the first time by Osman et al. 2023 , please mentioned that in the context.(https://doi.org/10.3390/fermentation9110934).

In material and methods:

1.      Please add the latitude coordinates for the sample collection location and a map figure showing the specific site.

2.      Do the authors have separated and quantified each type of seaweed individually?

3.      Possible inaccuracies in grid method for estimating biomass composition percentages. More precise quantitative analytical methods could strengthen results.

4.      TS and VS determination methods should be written in details.

5.      Table 2 could be improved by merging the seasonal data instead of repeating "Spring season", "Summer season", etc.

6.      Legend of Figure 1 could be modified as follow: Examples of samples for three seasons: (a-d) – spring season; (e-f) – summer season; (g-i) – autumn season.

7.      “A substrate composed of aquatic plant biomass (MASG), a mixture of cattle manure 166 with wheat straw (CMWS) and sewage sludge (WS)” those abbreviations for the substrate components are not intuitive or reader-friendly. You can use the following suggestion:

·        Aquatic plant biomass (APB)

·        Cattle manure + wheat straw (CMWS)

·        Sewage sludge (SS)

Results

1.      Lacked statistical analysis of the significance of differences between test conditions and seasonal factors in all figures and tables.

2.      it appears the authors conducted their study over three seasons rather than a full 12 months. So why they do make some references to potential yearly/seasonal dynamics and climate influences, the actual sampling and experiments detailed seem to have been done only over the course of these three seasons.

3.      Please clarify the type of the 4 samples used in figure 5.

4.      Did not account for variability in digestate nutrient levels over time. More frequent sampling could improve precision.

5.      Did not investigate long term storage effects on digestate stability and fertilizer quality.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The article is suitable and within the journal scope. The work deals with a topic of current interest and provides new experimentl results. The article is acceptable, although some minor improvements are listed below.

Explain the meaning of VS, TS, NS and DM the first time they are used.

Rewrite (pag 4) : “Along the shore there is brown algae, red and green  algae are present. “ for example to “Brown algae, along with red and green varieties, can be found along the shore.”

Table 3: Change “Kg” to “kg” (and everywhere in the text).

Page 9: “A study of the dynamics of the distribution…” Why the dynamics? What changes with time? What are samples 1 to 4 in Figure 5. This should be explained.

Acceptable

Author Response

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Author Response File: Author Response.pdf