What Could China Give to and Take from Other Countries in Terms of the Development of the Biogas Industry?

Round 1

Reviewer 1 Report

The manuscript needs thorough restructuring. From the introduction one gets the impression that the manuscript focuses on the new developments in medium to large scale biogas plants in China in comparison to to the development in Western countries, mainly Europe with main focus on Germany. But then in the end the authors also describe the developments in small scale household biogas plants - by the way small scale in Germany is already medium scale in China and elsewhere, therefore it is confusing to write about small scale biogas plants in German context.

Instead of describing in detail the modifications and changes of German EEG the authors should have focused on the essential outcomes which could be transferred to China and other countries. They should also consider modifications necessary for an application under Chinese circumstances. They also should stay with regulations concerning biogas. I don’t understand why they inserted the regulations for energy intensive enterprises in 2014 as these regulations were valid from beginning on?

The authors mix up technological descriptions and comparisons with legal-economic descriptions and comparisons and with descriptions and comparisons of country reports. They should be more strict in keeping a structure of the manuscript. So they could follow an order of describing the Chinese country report and followed by the technological, legal-economic and development issues and in each chapter what could be transferred from other countries to China or vice versa. They also should include the conclusions on the impact on Chinese biogas Industrie in each chapter.

The authors introduce at two causal loop models. They also should include necessary alterations of these models for a sound development.

The authors should also reconsider if all their conclusions are correct. E.g. I cannot follow that the up to now subsidy model of founding the construction leads the owners to save construction cost. I can follow that this scheme does not support a proper operation of the biogas plant.

Especially with conclusions on on-going developments in Europe the authors should not cite literature that is older than 4 years.

One final remark: as you usually use m³ as volumetric unit you should not confuse the the reader with Nm³ as this is a very German abbreviation and you do not state what a the standard conditions. 

Author Response

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript summarized the history and status of Chinese biogas industry and barriers limited its’ further development. Experiences from European countries, especially Germany, were intensively discussed as reference as it is one of the world leading countries for biogas sector. It is an interesting topic. However, the manuscript is not acceptable as current way. Please find my comments and suggestions.

General comments.

1. The entire biogas sector in China is booming within the recent decades under the background of economic development and special concerns on atmospheric conditions. However, most of the newly constructed biogas plants, regardless of the scales, cannot be operated as expected. This is, of course, partly due to the fact that the subsidies can only be used for construction rather than directly to ‘green’ energy under current regulation. However, it won’t be possible to copy European model directly to China. As the author mentioned in the manuscript, various European countries have their own strategies on biogas sector. This is due to the agricultural traditions. Therefore, I suggest the author to consider how to distinguish which is the most useful way to help China’s biogas development. Should we recommend the policy marker first or invest on new technologies ?  If the latter option has higher priority, the which technology is more promising ?

2. Moreover, China is a big country with quite different situations from North to South. It might be better to compare or make short note on that issue. Should China develop biogas in the same way or geographically?

3. The word ‘organic waste’ were generally used to describe the manure and agricultural straw. I will stand for using manure directly or ‘residue’ since it is not waste. We can convert it to energy and recover nutrients for crop cultivation. It is a mistake to call it ‘waste’, especially for us.

Some detailed suggestions

Abstract

(The abstract should be revised and re-organized)

Line 17: ‘Anaerobic digestion is one of the most sustainable and promising for the management of 17 organic waste.’  AD is .. promising of what ?  technologies or processes maybe ?

Line 25.should be ‘ established relatively complete laws, policies and a subsidy system.’

Keywords 

I think ‘lesson learned’ is not a good keyword.

Introduction

Line 39. The same issue with line 17.

Line 59-60. I am not very confident about that. However, please give details about how to category biogas plants into mid or large scale as in some other countries, they use farm-based or commercialized  biogas plant.

Line 64-66. As a scientific paper, the objective should be not too ambitious. You are not writing for a newspaper. It is not possible to promote the development of biogas industry throughout the world with one paper. J

Line 94. Table 2. I suggest to give detailed citations for this table. It can be summarized by the author but must be collected from ohter's work.

For instance the following paper:

Where is the future of China’s biogas? Review, forecast, and policy implications

3. Lessons learned from the frontrunners

In general, only Germany is discussed. Where are the statuses or lessons learned from Sweden, Austria, Denmark ?

Line 304. 3.3 Co-digestion plant. I suggest to not have 3.3 individually as co-digestion is still one of the AD technologies.Or only if you thought co-digestion is the most promising technology for China.

Table 6 and 7. It is not necessary to show any decimal in table 6 and 7.

Author Response

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has considerably been improved. You argued quite well the points you have not changed according to my suggestions.

One special remark I didn't consider in my first review. In the conclusions you write that " ... garbage-type dry fermentation and plug-flow dry fermentation, are feasible and promising ...". First: I guess you mean garage-type and second: to my opinion these conclusions are not supported by results and findings in your text. It seems to be a personal opinion of the authors.

Author Response

Response: First, yes, we mean “garage-type”. It is a clerical error. Thanks very much for finding this mistake for us.

Second, it was the suggestion from reviewer 2, who suggested us to present personal opinions more or less. So we added this and the title from “conclusions” to “conclusions and outlook”.

Reviewer 2 Report

Overall, the questions and comments are addressed. 

I suggest to accept. 

Author Response

Thanks for your acceptance.