Thermodynamic Equilibrium Study of Anaerobic Digestion through Helmholtz Equation of State
Round 1
Reviewer 1 Report
The paper is well written and structured. Here some typos and few comments:
· Line 44: Farry al posto di Fatty
· Eq 9: Check the stoichiometric balance (I guess that you should use 2* for one of the reactants)
· Line 200: aforedescribed(?)
· Discussion from line 268: If I understood correctly, the vapour fraction should increase with the pressure while the chart shows an opposite trend
Author Response
We thank the reviewer for the comments done, we advise him to see the attachment to check our report.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript introduces a thermodynamic equilibrium study of anaerobic digestion through Helmholtz equation of state with the aim to determine the best operating conditions (temperature and air pressure) for maximum pure bio-methane production. Temperatures between 20 and 55°C and at pressure values between 0.3 atm and 1.5 atm were examined for simulations. The modeling methods are interesting, and the results are also instructive. Below are my observations.
1. In the introduction, the background information of the four steps of anaerobic digestion could be simplified. Those equations could also be simplified and summarized in one figure or one table.
2. As H2S was one of the species being considered and studied, the authors should include the kinetic reaction step and reason of hydrogen sulfide formation in AD.
3. Page 9, Line 233. Grammar error. Missing of “that”. Pay attention to the use of subject when doing comparisons. Check throughout the manuscript.
4. Section 3.3 should be in the second part “Methods” rather than in the “Results”.
5. There are too many (a total of 11) figures in the manuscript. I recommend combining some figures into one or move some to the supplementary materials.
6. As mentioned, there were a total of 32 simulation points, however, in some figures (Figure 5-8), some of the data points were missing and seemed out of the axis range. The authors should widen the axes range or provide explanations in the manuscript if those missing data points were outliers.
7. Figure 9. How do you obtain it? The author should supplement the information of the data source of figure 9 in the manuscript. Also pay attention to the correct use of subtitles in the tittle text.
8. Page 13. Line 330-331. Equation 24. The authors should give the citation source when referring the previous work.
9. Page 13. Line 332-334. It will be more interesting and convincing to see the consistency of “The diffusion coefficients of the species into water” with the previous “works…”. The authors can provide a table to summarize them.
10. More discussion of comparing the previous work with this study are encouraged.
11. The results of this study are basically from simulations. It will be more persuasive if validation experiments were performed.
Author Response
We thank the reviewer for the comments done, we advise him to see the attachment to check our report.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors made meaningful revisions to address most of the comments. I believe that it is acceptable in the present form.
