Anaerobic Digestion Remediation in Three Full-Scale Biogas Plants through Supplement Additions

Round 1

Reviewer 1 Report

This research study provided valuable insights into the use of additives in anaerobic digestion to enhance efficiency and address environmental challenges. The authors highlighted the potential benefits of additives, such as increased biogas production, reduced air pollution, and prevention of total ammoniacal nitrogen (TAN) inhibition. Moreover, they emphasized the importance of selecting the appropriate type of supplementation, as the effects on biogas production can vary. This research contributes significantly to the understanding of the role of additives in anaerobic digestion, and the findings offer practical insights that can potentially lead to more efficient and sustainable anaerobic digestion practices. However, there are several points which need to be addressed:

1. Expanding on the methodology section would allow readers to better comprehend the experimental setup, data collection procedures, and statistical analysis employed in the study.

2. The specific types of additives used need to be clarified. I would like to encourage the authors to provide more detailed information about the specific types of additives utilized in the study. Describing the chemical or biological nature of the additives and their composition would allow readers to better understand the mechanisms behind their effects on anaerobic digestion.

3. Providing a comparison of additive performance is necessary. While the study mentions that the effects of additives can vary depending on the type of supplement used, it would be beneficial to include a comparative analysis of different additives. Evaluating and discussing the performance of various additives in terms of their impact on biogas production and stabilization would provide a more comprehensive understanding of their relative effectiveness. Before addressing these concerns, I will recommend this paper with minor revisions. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Development of methods for enhanced efficiency of anaerobic digestion, and critical analysis their efficiency and, furthermore, maintain the biodegradation stability during AD has high importance for the practice. There are known several additives to boost the biogas (methane) production, and decrease the pH fluctuation during biodegradation, or reduce the undesirable gas emission, but their applicability and efficiency is less analysed in full-scale studies. Therefore, the topic of the manuscript can be considered as relevant and the manuscript can provide useful information not just for the science but also for the practice. The manuscript has a logic structure. Introduction section highlights well and clears the main operation problems of operating biogas plants and summarizes well the background and the specific aims of the research. The manuscript contains valuable and novel results that are represented well in figures and tables. The applied methods are adequate and described clearly.

Comments, suggestions:

Please give some more concrete parameters in the Abstract (zeolite dosage etc).

Please give additional references to establishments in lines 47-55.

Please provide the measuring errors for data presented in figures (if available).

Please improve the visibility of Figure 3 (mainly text).

In my opinion it is unnecessary to give the same word in figure captions and figure titles (‘micro-elements’, ‘macro elements’ etc.).

Please discuss and explain the results with relevant references, as well (section 3 ‘Discussion’).

Authors mentioned in lines 225-226 that ‘digested substrate material also affected the microbiome of the D1 digester’. Please give data related to the change of the microbiome and/or verify this establishment with reference(s).

Please give more information related to the trace element mixture, and explain how the dosage of zeolite and trace elements mixture was selected/determined.

Please discuss the (change of) CH4/CO2 in the produced biogas, as well.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript has an interesting topic that has practical relevance for the industry, as well. Authors have revised the manuscript thorougful according to suggestions and comments of the reviewers. The scientific quality of the manuscript has been improved significntaly due to the revision. The authors provided detailed answers for reviewers' questions. I agree and accept all modifications made by the authors.