Review Reports

Round 1

Reviewer 1 Report

The article presents the results of years of joint work in cooperation between scientists from Kazakstan and Switzerland. The analysis of the existing combined gas installations in the territory of Kazakstan and the possibility of introducing new, more technological and efficient ones.

The authors studied 5 potential sites for the application of biogas technologies, some of which already have installations for the processing of organic raw materials with the production of biogas.

The shortcoming is that in paragraph 4, five farms are considered in detail, three of which have no biogas plants, instead in the paragraph 5, there are three options solutions, only for farms with existing installations.

Another drawback is in taking biogas technologies introduced in Africa as an example. Despite the fact that Kazakhstan is low-middle-income country, given the climatic conditions, it would preferable to take biogas plants in northern countries such as Denmark and Germany as an example instead of Africa.

For example solution for Yuldosh Majid (Khiva district), proposed in paragraph 5.2 (Fig. 6), implemented in Ghana, will rather not work in the cold winters with temperature of -5^oC. The same is said in the source 44, to which the authors refer.

Another note, schemes shown in Figure 5 as well as Figure 7 needs a more detailed explanation. It is not indicated what improvement is expected as a result of the application of the technologies indicated in these figures.

Some line in paragraph 6 does not sound convincing. For example, the conclusion that for the efficient operation of biogas plants it is necessary to mix different types of organic waste to increase the yield of biogas, and the farms in Kazakstan are geographically remote from settlements (line 462), does not give a chance for the development of biogas technologies in Kazakstan. As well as fact, that only farms up to 250 heads of livestock (line 439), could make biogas generation facilities economically feasible, instead all studied ones were up to cattle 200 heads.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is very interesting case  study focuses on the Aral Sea region of Uzbekistan possessing a well-developed agricultural prduction with high livestock numbers and intensive crop production.

Some suggestions for correction:

1. I suggest that the article should be supplemented with information on the biogas potential/methane potential of substrates that occur on farms. It is worth developing a discussion in this direction.
2. It would be interesting to show the expected amount of biogas produced (Table 1) and to develop the discussion on the use of this biogas on farms (for example, covering the electricity demand of farms etc.).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The information presented in the manuscript is certainly interesting and important from the perspective of the issues raised in the analyzed region. However, it should be pointed out that the manuscript is too general and shallowly addresses the issues raised. It is like an after-control report showing deficiencies or irregularities in operating installations.

The presented manuscript does not meet the structure and assumptions of the Case Study. Case study as a research method involves approximation, in-depth and detailed study of a specific situation.

Line 180: 3. Problem identification and study purpose - chapter name does not correspond to the description presented.

Authors should define the purpose, material and methodology in a more detailed and specific way.

Pay attention to the properties of the raw material, its availability, transport and suitability for the biogas production process. And also the technological process of biogas production itself.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Question 4: Another note, schemes shown in Figure 5 as well as Figure 7 needs a more detailed explanation. It is not indicated what improvement is expected as a result of the application of the technologies indicated in these figures.

Answer 4: Figure 5 (line 360-363) and Figure 7 (387-390) are provided with more detailed explanation. Updated in the paper please

Comment: The updated text to Figure 5 does not provide any details or explain what the improved design of the existing installation is. The scheme captions are missed.

Author Response

Dear Reviewer,

Thanks for your feedback.

Now, the updated manuscript includes more details about the figure 5 on improved design of the simple liquid manure digester (line 361-367). The scheme captions are decribed properly.

 

Reviewer 3 Report

No further comments. The authors provided appropriate explanations and supplements in the text of the article. I accept the manuscript in present form.

Author Response

Dear Reviewer,

Many thanks for positive evaluation of our latest efforts to improve the paper!