Management and Reduction Techniques Strategies of Ammonia Emission in Agricultural Sectors in China
Round 1
Reviewer 1 Report
Dear authors, the manuscript entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”，reviewed progress of the NH3 emission inventory, NH3 emission management strategy, and NH3 emission reduction techniques strategy in China. The results help to promote attention to government, agriculture, and breeding industries. The manuscript looks sound, and had some small advices.
1. Authors should introduce the measurement methodology of NH3 emission briefly.
2. The control of NH3 emission in China has transformed from emission standards to technical guidelines to national strategic control. More proposal to government were needed on reasonable evaluation and reduces of NH3 emission.
3. The next research focus on NH3 emission were available in the part of Conclusions and expectations.
Author Response
Response to Reviewer’ s Comments
Dear reviewer,
We would like to express our gratitude to you for the opportunity to review and revise our manuscript agronomy-2589162 entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”. These comments are of great help to us in revising and improving the manuscript. We made revisions one by one based on the comments of the reviewers. At the same time, the content and grammar of the manuscript was checked. We hope that this manuscript will be considered by the agronomy. The following are the responses and modifications.
Comments and Suggestions for Authors
Dear authors, the manuscript entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”，reviewed progress of the NH3 emission inventory, NH3 emission management strategy, and NH3 emission reduction techniques strategy in China. The results help to promote attention to government, agriculture, and breeding industries. The manuscript looks sound, and had some small advices.
- Authors should introduce the measurement methodology of NH3emission briefly.
Response:
Thank you very much. The content of the NH3 emission calculation method has been added in the introduction.
Line 61: “Estimates of NH3 emissions rely primarily on the multiplication of activity levels of emission sources with emission factors [12]. Data on the activity level of a single source are easier to obtain, while data on local emission factors are more difficult to obtain. The emission factor method, which was widely used in early research, often used a single emission source activity level, such as multiplying the year-end inventory of livestock and poultry such as cattle and sheep by the corresponding emission factor in the statistical yearbook. The emission factors are directly calculated using foreign data or the average values of multiple foreign ammonia emission factors [12, 13]. The uncertainty in the results generated by this calculation method mainly comes from the differences between foreign emission factors and actual emission factors in various regions of China.”
- The control of NH3emission in China has transformed from emission standards to technical guidelines to national strategic control. More proposal to government were needed on reasonable evaluation and reduces of NH3 emission.
Response:
Thank you for your constructive comment. It has been added.
Line 354: “Although it started late, NH3 reduction in China is now a national program and requirement. Regarding NH3 emission control, national laws require that livestock and poultry breeding and farmland fertilization to pay attention to reducing NH3 emissions [44]. Specific action plans also emphasize the importance of NH3 reduction. The environ-mental protection department and agricultural department have policy documents that provide such technical advice. Irrespectively, China’s current NH3 emission control is un-clear about emission reduction targets and applications of emission reduction measures. Although laws and policy documents stipulate requirements for NH3 emission control, these requirements need further clarification. The practices of the European Union and the United States can provide reference for China's NH3 emission reduction. Establishing a complete technical framework for NH3 emission reduction is an important step. The next is to propose effective measures for key emission sources and key regions. In addition, more localized measures should be proposed, taking into account the local soil and aquaculture situation in China.”
Line 482: “The strategy of NH3 emission reduction should still be continued. For government departments, a better regional cooperation mechanism should be established. At the same time, the existing mechanism should be made more mature and publicized, including the provision of a more complete ammonia emission inventory, emission reduction targets and emission reduction measures in the relevant regions.”
- The next research focus on NH3emission were available in the part of Conclusions and expectations.
Response:
Based on reviewer's suggestion. The Conclusions and Perspectives section has been revised and next research focuses have been added.
Line 486: “In addition, more localized experiments need to be conducted to obtain more accurate emission factors. Improvement of localized models needs to be a priority. This will reduce the uncertainty of NH3 emission estimates. In terms of specific emission reduction measures, low-protein feeding technology, large-scale livestock and poultry farming, pilot projects on confined negative-pressure farming, as well as soil-formula fertilization and increasing the proportion of non-ammonium nitrogen fertilizers should be further pro-moted. The proportion of technology applications, economic benefits and supporting measures need more attention.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The purpose of this study is not clearly formulated, so it is not clear what answers you wanted to obtain. Maybe that's why the final conclusions in chapter „Conclusions and expectations” are not very properly written, it is more like summary and expectations. I do not find any conclusions as such. Some statements do not seem to be based on the material presented and analyzed in the manuscript, but simply based on the opinion of the authors (I have no doubt that you know the situation).
The authors provide detailed information on how the legal framework for NH3 emissions in China has changed (NH3 emissions inventory progress, NH3 emissions management strategy, objectives and policies, administration and supervision, NH3 emissions management mechanism), but no data is provided on how this has affected the situation in China, what the results were obtained. In order to justify the claim "Progress of the NH3 emission inventory", it is not enough to present only the bureaucratic mechanism (resolutions and procedures) without specific country data.
In chapter 4. „ NH3 emission reduction techniques strategy” you discuss what is being done in the world in terms of reducing NH3 emissions, but you do not try to relate to the situation in China, so it is not clear whether it will work effectively in your conditions. For example, you claim that in order to reduce the amount of emissions, you need to use low protein feed, (line 240) but it is not clear (you do not provide information) what level of feeding is now used, is it relevant in Chinese conditions.
In section 4.3 „Country/Regional Comparisons” describes in detail response strategies, and measures applied in the US and the European Union, and results obtained, but you do not relate them to the situation in China, you do not provide data Regarding emissions in China or its regions, you do not attempt to model how those measures would work in your country conditions and which could be effective.
There are also proofreading errors, technical corrections are needed: unify the font size (line 405), make spaces in many places when citing authors and indicating the source.
Author Response
Response to Reviewer’ s Comments
Dear reviewer,
We would like to express our gratitude to you for the opportunity to review and revise our manuscript agronomy-2589162 entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”. These comments are of great help to us in revising and improving the manuscript. We made revisions one by one based on the comments of the reviewers. At the same time, the content and grammar of the manuscript was checked. We hope that this manuscript will be considered by the agronomy. The following are the responses and modifications.
Comments and Suggestions for Authors
The purpose of this study is not clearly formulated, so it is not clear what answers you wanted to obtain. Maybe that's why the final conclusions in chapter „Conclusions and expectations” are not very properly written, it is more like summary and expectations. I do not find any conclusions as such. Some statements do not seem to be based on the material presented and analyzed in the manuscript, but simply based on the opinion of the authors (I have no doubt that you know the situation).
Response:
Thank you very much for pointing out the critical problem. It is true that the introduction section in the previous manuscript was not organized well. The purpose of the study was not clearly stated. This resulted in a not well written conclusion section. Therefore, we have reorganized the Introduction (including the Purposes) and Conclusion.
Line 61: “Estimates of NH3 emissions rely primarily on the multiplication of activity levels of emission sources with emission factors [12]. Data on the activity level of a single source are easier to obtain, while data on local emission factors are more difficult to obtain. The emission factor method, which was widely used in early research, often used a single emission source activity level, such as multiplying the year-end inventory of livestock and poultry such as cattle and sheep by the corresponding emission factor in the statistical yearbook. The emission factors are directly calculated using foreign data or the average values of multiple foreign ammonia emission factors [12, 13]. The uncertainty in the results generated by this calculation method mainly comes from the differences between foreign emission factors and actual emission factors in various regions of China.
Various policy measures have been proposed for the control of ammonia emissions. This includes clear provisions in the national law Air Pollution Prevention and Control Law of the People's Republic of China [14], as well as the special action plan Three-Year Action Plan to Fight Air Pollution [15] to address air pollution control. In terms of measures, technical guidelines such as the Technical Guideline on Environmental Safety Application of Chemical Fertilizer [16] provide a basis for ammonia emission cases. However, it can be observed that in implementing ammonia emission control, although the goal of reducing ammonia emissions has been proposed, this goal has not been quantified, and the implementation of specific emission reduction measures also needs to be further improved. The effective-ness of ammonia emission control in various regions needs to be evaluated.
Based on this, the research objectives of this paper are 1) to briefly sort out China's goals and policies on ammonia emission control and the relationship between government departments in the decision-making system; 2) to summarize the methods and results of ammonia emission inventories at different regional scales in recent years, and to understand the changes in China's ammonia emissions during the period of 1980-2019; and 3) to propose emission reduction measures in the areas of livestock and poultry farming and fertilizer application to farmland based on the goals and policies and the results of the ammonia emission inventories.”
Line 469: “This paper provides an overall overview of the management and reduction strategies for agricultural NH3 emissions in China. The control of ammonia emissions in China has gone through a process of development from emission standards to technical guidelines to national strategic control. Cooperation among governmental departments based on the national strategy is conducive to promoting the realization of ammonia emission reduction targets. Due to the differences in calculation methods, the results of NH3 emission inventories at different scales across the country vary widely. This makes the control of regional ammonia emissions more difficult, and the current status of NH3 emissions and emission reduction targets are difficult to be quantified in a uniform manner. In terms of technical measures to reduce emissions, more detailed technical operation guidelines are readily available. But the application of these measures in the relevant industries is not obvious enough, and the effectiveness of the reduction technologies in the field needs to be further evaluated.
The strategy of NH3 emission reduction should still be continued. For government departments, a better regional cooperation mechanism should be established. At the same time, the existing mechanism should be made more mature and publicized, including the provision of a more complete ammonia emission inventory, emission reduction targets and emission reduction measures in the relevant regions. In addition, more localized experiments need to be conducted to obtain more accurate emission factors. Improvement of localized models needs to be a priority. This will reduce the uncertainty of NH3 emission estimates. In terms of specific emission reduction measures, low-protein feeding technol-ogy, large-scale livestock and poultry farming, pilot projects on confined negative-pressure farming, as well as soil-formula fertilization and increasing the proportion of non-ammonium nitrogen fertilizers should be further promoted. The proportion of technology applications, economic benefits and supporting measures need more attention.”
The authors provide detailed information on how the legal framework for NH3 emissions in China has changed (NH3 emissions inventory progress, NH3 emissions management strategy, objectives and policies, administration and supervision, NH3 emissions management mechanism), but no data is provided on how this has affected the situation in China, what the results were obtained. In order to justify the claim "Progress of the NH3 emission inventory", it is not enough to present only the bureaucratic mechanism (resolutions and procedures) without specific country data.
Response:
We strongly agree with the reviewer's suggestion that additional data are needed to support the progress of the ammonia emission inventory. As suggested by the reviewers, we have added results on ammonia emission inventories at different scales (Table 1). We also added the results of ammonia emissions in months under different years and ammonia emissions in different provinces at the national scale. As follows:
Line 149: “There is significant increase in the range of studies on NH3 emission inventories nationwide. The estimated geographical scope has also expanded to include provincial, inter-provincial and the entire country. As in Table 1, a variety of methods (including the CHEN, NARSES, IAP-N and emission factor methods) have been used in NH3 emission studies in different areas, with different methods yielding different results. The emission factor method used by Ma [4] yielded a national anthropogenic NH3 emission in 2015 of 12580 Gg and that of livestock and poultry of 2560 Gg (20% of the total). Farmland emission was 5580 Gg (44.4%) and NH3 emission from waste treatment 1810 Gg (14.4%). Zhang et al. [6] used Coupled Human and Natural Systems (CHANS) model to estimate national NH3 emissions in 2015 of 15,600 Gg, of which 5870 Gg (37.6%) was from farmlands and 6650 Gg (42.6%) form livestock and poultry farming. The latter had significant-ly higher NH3 emission from livestock and poultry farming, mainly because a higher NH3 emission rate was used. Furthermore, Fu et al. [20] noted that although agriculture was the main source of NH3 emission, non-agricultural NH3 emissions were also increasing.
Table 1 Summary of NH3 emission inventories at different scales
|
No. |
Area |
Time |
Source |
Resolution |
Method |
Activity data |
Factor differentiation |
Total/Gg |
Farmland/Gg |
Livestock & poultry /Gg |
Human/Gg |
Uncertainty method |
Uncertainty |
Reference |
|
|
1 |
National |
National |
2016 |
Anthropogenic |
1*1km |
CHEN |
Provincial |
Yes |
11032.00 |
6475.00 |
3032.00 |
487.00 |
MC |
(-20%, +24%) |
[20] |
|
National |
2015 |
Anthropogenic |
|
CHANS |
Provincial |
Yes |
15600.00 |
5870.00 |
6650.00 |
780.00 |
MC |
(-21%, 32%) |
[6] |
||
|
National |
2015 |
Anthropogenic |
1*1km |
EF |
Provincial |
Yes |
12580.00 |
5580.00 |
2560.00 |
870.00 |
Literature-based values |
±30% |
[4] |
||
|
2 |
Regional |
Yangtze River Delta region |
2014 |
Anthropogenic |
1*1km |
EF、 NARSES |
Prefecture-level city |
Partial |
986.73 |
532.82 |
316.68 |
51.11 |
MC |
(-55%, +60%) |
[5, 34] |
|
North China |
2016 |
Anthropogenic |
|
EF |
Prefecture-level city |
Partial |
966.14 |
350.04 |
548.90 |
13.11 |
MC |
(-17%, 25%) |
[34] |
||
|
Sichuan and Chongqing |
2004 |
Agricultural |
|
IAP-N |
County |
No |
698.76 |
374.94 |
219.60 |
98.59 |
Qualitative analysis |
[23] |
|||
|
3 |
Provincial |
Fujian |
2015 |
Anthropogenic |
1*1km |
EF、 NARSES |
County |
Partial |
228.02 |
89.74 |
98.37 |
11.13 |
MC |
±16.3% |
[33] |
|
Jiangsu |
2017 |
Anthropogenic |
|
EF |
Prefecture-level city |
No |
562.47 |
250.54 |
212.91 |
33.55 |
Qualitative analysis |
[35] |
|||
|
Henan |
2015 |
Anthropogenic |
3*3km |
EF、 NARSES |
Prefecture-level city |
Partial |
1031.60 |
291.00 |
591.50 |
31.60 |
MC； the AuvToolPro tool |
(-33%, 35%) |
[2] |
||
Based on aggregated literature data [22, 36-39], China’s NH3 emission changes every month (Fig. 3). Due to limited data availability, NH3 emission data were collected for different years. It suggested differences in year-to-year NH3 emission. But on the average, however, different data had similar monthly variations. March to October of each year was the time with relatively high NH3 emission. Starting in March, NH3 emission gradually increases and reaching the highest point between June and August; and then gradually decreases. This trend is closely related with agricultural production activities. This is mainly caused by changes in nitrogen fertilizer application and NH3 emission from live-stock and poultry farming [22]. In terms of nitrogen fertilizer, application increases in April, after the start of spring planting and the warming temperature gradually increase NH3 emission. As most of the crops are harvested in autumn, NH3 emission gradually decreases during this period [36]. For livestock and poultry breeding, the relatively higher temperatures could also be due to the gradual increase in NH3 emission from the livestock and poultry breeding.
Figure 3 Monthly variations in NH3 emission in China
The difference in emission factor is the main reason for the significant difference in calculated results. When calculating emissions across the country, NH3 emission factor should take into account regional differences. This is so because emission coefficients are calculated based on provincial administrative divisions. In various studies, however, the values of emission factors for the same province are not consistent. For example, in calculating NH3 emissions in 2015, Zhang et al., [6] used an emission factor of 14.3% for NH3 emission from nitrogen fertilizers in Henan Province while Ma [4] used 15.1% for the same year and area. These emission factors are calculated in reference to different literature values. The emission results for the latter two studies are also quite different. The rea-son behind this difference shows the relevance of the parameters used to calculate NH3 emissions in China. NH3 emission accuracy should be ensured for effective implementation of reduction measures. This implies that NH3 emission reductions, environmental protection agencies or other government agencies should evaluate existing data to provide guidance.”
In chapter 4. “NH3 emission reduction techniques strategy” you discuss what is being done in the world in terms of reducing NH3 emissions, but you do not try to relate to the situation in China, so it is not clear whether it will work effectively in your conditions. For example, you claim that in order to reduce the amount of emissions, you need to use low protein feed, (line 240) but it is not clear (you do not provide information) what level of feeding is now used, is it relevant in Chinese conditions.
Response:
As stated by the reviewers, the emission reduction strategy should be combined with the actual situation in China to illustrate its effectiveness. Therefore, combining more research and field experiments, we have revised the section on emission reduction technologies.
Line 353: “In order to control NH3 emission, promotion of low-protein feed and bio-treatment of livestock and poultry manure can be considered. Also, construction of airtight breeding enterprises and NH3 emission purification devices could help. Specifically, low-protein feed techniques include replacing high-protein components in feeds with low-protein ones and using synthetic amino acids to partially replace crude protein [53]. Test results in Europe show that low-nitrogen feeds reduce NH3 emission by 4.1% [55]. Another study [56] shows that feeding dairy cows on feeds with protein content increased from 15 to 21%, urine nitrogen content increases linearly from 153.5 to 465.2 mg/dL. A similar increase occurs in pig breeding. When crude protein level in feed is reduced by 1%, total nitrogen and ammonium nitrogen content in the manure drop respectively by 8.5% and 10% [57], reducing NH3 volatilization by 10% [58].
In addition to low-protein feed, which controls NH3 emission in terms of nitrogen input, it is also possible to treat livestock manure to reduce NH3 emission from manure. Volatilization of NH3 will be higher when urine is in prolonged contact with feces. There-fore, to reduce the potential for NH3 volatilization, urine and feces should be separated quickly to reduce the contact between urease in feces and urea in urine [53]. Studies have shown that flushing every 2-3 h using the water-flush technique can effectively reduce ammonia volatilization by 14-70% [59]. Composting is one typical way of bio-treatment of animal manure. In composting, nitrogen in feces is converted to ammonium nitrogen through NH3 and then volatilizes as NH3. Measures such as controlling C/N ratio, ventilation and additives can reduce NH3 emission [60]. When a composting exhaust filter is used during the composting process, the emission reduction efficiency of NH3 is between 36% and 94% [61]. For large-scale aquaculture enterprises, waste gas can be collected by acid scrubbers or bio-trickling filters to convert NH3 into ammonium sulfate or nitrate substances, with NH3 reduction rate of over 70% [62]. Regarding internal and external exhaust gas from housing, most large-scale breeding enterprises in China have airtight housing facilities. A negative pressure environment is maintained in the housing and NH3 -containing waste gas is collected and discharged after pickling. However, since acidic chemicals are currently controlled, the actual operation of pickling equipment is not ideal [63].”
In section 4.3 “Country/Regional Comparisons” describes in detail response strategies, and measures applied in the US and the European Union, and results obtained, but you do not relate them to the situation in China, you do not provide data Regarding emissions in China or its regions, you do not attempt to model how those measures would work in your country conditions and which could be effective.
Response:
Thank you very much for this constructive suggestion. We have modified the Country/regional comparisons section. China's emission reduction strategy has been compared with the European Union and the United States. And based on the strategies of other countries, some emission reduction strategies that are more suitable for China have been proposed. More data has also been supplemented in sections 2 and 3.1.
Line 453: “Although it started late, NH3 reduction in China is now a national program and requirement. Regarding NH3 emission control, national laws require that livestock and poultry breeding and farmland fertilization to pay attention to reducing NH3 emissions [44]. Specific action plans also emphasize the importance of NH3 reduction. The environ-mental protection department and agricultural department have policy documents that provide such technical advice. Irrespectively, China’s current NH3 emission control is un-clear about emission reduction targets and applications of emission reduction measures. Although laws and policy documents stipulate requirements for NH3 emission control, these requirements need further clarification. The practices of the European Union and the United States can provide reference for China's NH3 emission reduction. Establishing a complete technical framework for NH3 emission reduction is an important step. The next is to propose effective measures for key emission sources and key regions. In addition, more localized measures should be proposed, taking into account the local soil and aquaculture situation in China.”
There are also proofreading errors, technical corrections are needed: unify the font size (line 405), make spaces in many places when citing authors and indicating the source.
Response:
Thank you so much. The problems pointed out by the reviewer have been corrected.
Reviewer 3 Report
This article reviews 40 years of NH3 emission control strategies in China, highlighting challenges such as inconsistent calculation methods and a lack of localized emission factors, leading to variable NH3 inventories influenced by meteorology and farming practices.
The article holds scientific significance; however, it requires further revision before official publication. The primary concern is the lack of clear differentiation between ammonia emissions and agricultural ammonia emissions. For instance:
-
Please clarify the distinction between ammonia emissions and agricultural ammonia emissions in the abstract, aligning with the article's title.
-
Elaborate more on the development of an ammonia emissions inventory, rather than focusing solely on agricultural ammonia emissions.
-
In Part 3, consider revising the title to emphasize agricultural ammonia emissions instead of ammonia emissions.
-
Although ammonia emissions were calculated, this is not adequately reflected in the article's content. Please incorporate these calculations into the introduction section.
-
Furthermore, please emphasize the uniqueness and innovation of this review's content compared to previous articles on ammonia emission inventories.
Need further improvement
Author Response
Response to Reviewer’ s Comments
Dear reviewer,
We would like to express our gratitude to you for the opportunity to review and revise our manuscript agronomy-2589162 entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”. These comments are of great help to us in revising and improving the manuscript. We made revisions one by one based on the comments of the reviewers. At the same time, the content and grammar of the manuscript was checked. We hope that this manuscript will be considered by the agronomy. The following are the responses and modifications.
Comments and Suggestions for Authors
This article reviews 40 years of NH3 emission control strategies in China, highlighting challenges such as inconsistent calculation methods and a lack of localized emission factors, leading to variable NH3 inventories influenced by meteorology and farming practices.
The article holds scientific significance; however, it requires further revision before official publication. The primary concern is the lack of clear differentiation between ammonia emissions and agricultural ammonia emissions. For instance:
Please clarify the distinction between ammonia emissions and agricultural ammonia emissions in the abstract, aligning with the article's title.
Response:
Thank you so much. We clarify the distinction between agricultural ammonia emissions and ammonia emissions in the Abstract. As follows:
Line 13: “Agricultural ammonia (NH3) emissions (including farmland, livestock and poultry) are the main sources of NH3 emissions in China. China’s government has proposed a national strategic goal to reduce NH3 emission. Excessive protein feeds, unreasonable manure treatments and agricultural fertilizer applications result in large emissions of NH3. Agricultural activities such as breeding of livestock and fertilization in farmlands are the main sources of atmospheric NH3 emissions. This article discussed the progress and characteristics of typical NH3 emission inventory, calculated the nationwide NH3 emissions and analyzed the NH3 emission control strategy in the past 40 years in China. There was also a integration analysis of national documents on emission reduction tech-nologies (including government reports) in China. The results showed that, there existed single calculation methods and insufficient localization of emission factors in the estimation of domestic NH3 emissions. NH3 emission inventories varied greatly influenced by meteorology, planting structure and breeding pattern. The control strategy of NH3 emission in China has transformed from emission standards to technical guidelines to national strategic control, and it involves the coordination and cooperation of the Ministry of Agriculture and Rural Affairs departments. Current domestic NH3 emission management strategy needs scientific emission verification specification, multi-department and inter-provincial regional coordination mechanisms, suggestions for further improvement have been put forward. It is urgent to evaluate precise NH3 emission inventories at different regional scales, followed by intensive NH3 emission controls in the key regions (such as North China). Government, agriculture, and breeding industries should vigorously promote low-protein feeds, large-scale livestock farming (including poultry), and pilot projects on closed negative pressure farming. Also, agriculture related NH3 emission reduction measures should be fully implemented by providing technical support for NH3 emission control in domestic agricultural farms.”
Elaborate more on the development of an ammonia emissions inventory, rather than focusing solely on agricultural ammonia emissions.
Response:
Thank you to the reviewer for this constructive comment. We have added more ammonia emission inventory data and descriptions, not limited to agricultural ammonia emissions. As follows:
Line 149: “There is significant increase in the range of studies on NH3 emission inventories nationwide. The estimated geographical scope has also expanded to include provincial, in-ter-provincial and the entire country. As in Table 1, a variety of methods (including the CHEN, NARSES, IAP-N and emission factor methods) have been used in NH3 emission studies in different areas, with different methods yielding different results. The emission factor method used by Ma [4] yielded a national anthropogenic NH3 emission in 2015 of 12580 Gg and that of livestock and poultry of 2560 Gg (20% of the total). Farmland emission was 5580 Gg (44.4%) and NH3 emission from waste treatment 1810 Gg (14.4%). Zhang et al. [6] used Coupled Human and Natural Systems (CHANS) model to estimate national NH3 emissions in 2015 of 15,600 Gg, of which 5870 Gg (37.6%) was from farmlands and 6650 Gg (42.6%) form livestock and poultry farming. The latter had significant-ly higher NH3 emission from livestock and poultry farming, mainly because a higher NH3 emission rate was used. Furthermore, Fu et al. [20] noted that although agriculture was the main source of NH3 emission, non-agricultural NH3 emissions were also increasing.”
Table 1 Summary of NH3 emission inventories at different scales
|
No. |
Area |
Time |
Source |
Resolution |
Method |
Activity data |
Factor differentiation |
Total/Gg |
Farmland/Gg |
Livestock & poultry /Gg |
Human/Gg |
Uncertainty method |
Uncertainty |
Reference |
|
|
1 |
National |
National |
2016 |
Anthropogenic |
1*1km |
CHEN |
Provincial |
Yes |
11032.00 |
6475.00 |
3032.00 |
487.00 |
MC |
(-20%, +24%) |
[20] |
|
National |
2015 |
Anthropogenic |
|
CHANS |
Provincial |
Yes |
15600.00 |
5870.00 |
6650.00 |
780.00 |
MC |
(-21%, 32%) |
[6] |
||
|
National |
2015 |
Anthropogenic |
1*1km |
EF |
Provincial |
Yes |
12580.00 |
5580.00 |
2560.00 |
870.00 |
Literature-based values |
±30% |
[4] |
||
|
2 |
Regional |
Yangtze River Delta region |
2014 |
Anthropogenic |
1*1km |
EF、 NARSES |
Prefecture-level city |
Partial |
986.73 |
532.82 |
316.68 |
51.11 |
MC |
(-55%, +60%) |
[5, 34] |
|
North China |
2016 |
Anthropogenic |
|
EF |
Prefecture-level city |
Partial |
966.14 |
350.04 |
548.90 |
13.11 |
MC |
(-17%, 25%) |
[34] |
||
|
Sichuan and Chongqing |
2004 |
Agricultural |
|
IAP-N |
County |
No |
698.76 |
374.94 |
219.60 |
98.59 |
Qualitative analysis |
[23] |
|||
|
3 |
Provincial |
Fujian |
2015 |
Anthropogenic |
1*1km |
EF、 NARSES |
County |
Partial |
228.02 |
89.74 |
98.37 |
11.13 |
MC |
±16.3% |
[33] |
|
Jiangsu |
2017 |
Anthropogenic |
|
EF |
Prefecture-level city |
No |
562.47 |
250.54 |
212.91 |
33.55 |
Qualitative analysis |
[35] |
|||
|
Henan |
2015 |
Anthropogenic |
3*3km |
EF、 NARSES |
Prefecture-level city |
Partial |
1031.60 |
291.00 |
591.50 |
31.60 |
MC； the AuvToolPro tool |
(-33%, 35%) |
[2] |
||
Line 265: “Fig. 5 shows NH3 emission intensity in each province in 2019. Shandong, Henan, and Jiangsu are the three provinces with the highest NH3 emission intensity, which are respectively 4,531.74, 4,664.05 and 3,355.96 kg/km2. This is followed by Hebei, Liaoning, Anhui, Hubei, Hunan and Guangdong provinces; with emission density of 1819.91‒2787.05 kg/km2. The emission intensities of the other provinces are relatively low. Most of the NH3 emissions are contributed by livestock and poultry farming and nitrogen fertilizer. The total amount of NH3 emission in Jiangsu Province is not high and is even lower than that of other provinces such as Sichuan and Inner Mongolia. When combined with the area of Jiangsu Province, the NH3 emission density of Jiangsu Province is still second only to Henan and Shandong. Similarly, Fu et al. [20] noted that agricultural NH3 emission in-tensity of Henan and Jiangsu provinces was significantly higher than that of other prov-inces, with the highest NH3 emission intensity of 6000‒8000 kg/km2. Ma [4] also showed that Henan and Jiangsu have high NH3 emission intensity in the country, including also Sichuan and Chongqing.”
Note that this figure does not include Hong Kong, Macau and Taiwan data
Figure 5 NH3 emission intensity of different provinces in 2019
In Part 3, consider revising the title to emphasize agricultural ammonia emissions instead of ammonia emissions.
Response:
Thank you very much. It has been modified.
Line 195: “3. China's agricultural NH3 emission management strategy.”
Although ammonia emissions were calculated, this is not adequately reflected in the article's content. Please incorporate these calculations into the introduction section.
Response:
Based on the reviewer's suggestion. We have revised the introduction and added a description of the calculation of ammonia emissions.
Line 61: “Estimates of NH3 emissions rely primarily on the multiplication of activity levels of emission sources with emission factors [12]. Data on the activity level of a single source are easier to obtain, while data on local emission factors are more difficult to obtain. The emission factor method, which was widely used in early research, often used a single emission source activity level, such as multiplying the year-end inventory of livestock and poultry such as cattle and sheep by the corresponding emission factor in the statistical yearbook. The emission factors are directly calculated using foreign data or the average values of multiple foreign ammonia emission factors [12, 13]. The uncertainty in the results generated by this calculation method mainly comes from the differences between foreign emission factors and actual emission factors in various regions of China.”
Line 81: “Based on this, the research objectives of this paper are 1) to briefly sort out China's goals and policies on ammonia emission control and the relationship between government departments in the decision-making system; 2) to summarize the methods and results of ammonia emission inventories at different regional scales in recent years, and to understand the changes in China's ammonia emissions during the period of 1980-2019; and 3) to propose emission reduction measures in the areas of livestock and poultry farming and fertilizer application to farmland based on the goals and policies and the results of the ammonia emission inventories.”
Furthermore, please emphasize the uniqueness and innovation of this review's content compared to previous articles on ammonia emission inventories.
Response:
Thank you for this important suggestion. We strongly agree with the importance of innovation as you mentioned. Therefore, the necessity of our study was emphasized in the introduction. As follows:
Line 71: “Various policy measures have been proposed for the control of ammonia emissions. This includes clear provisions in the national law Air Pollution Prevention and Control Law of the People's Republic of China [14], as well as the special action plan Three-Year Action Plan to Fight Air Pollution [15] to address air pollution control. In terms of measures, technical guidelines such as the Technical Guideline on Environmental Safety Application of Chemical Fertilizer [16] provide a basis for ammonia emission cases. However, it can be observed that in implementing ammonia emission control, although the goal of reducing ammonia emissions has been proposed, this goal has not been quantified, and the implementation of specific emission reduction measures also needs to be further improved. The effectiveness of ammonia emission control in various regions needs to be evaluated.
Based on this, the research objectives of this paper are 1) to briefly sort out China's goals and policies on ammonia emission control and the relationship between government departments in the decision-making system; 2) to summarize the methods and results of ammonia emission inventories at different regional scales in recent years, and to understand the changes in China's ammonia emissions during the period of 1980-2019; and 3) to propose emission reduction measures in the areas of livestock and poultry farming and fertilizer application to farmland based on the goals and policies and the results of the ammonia emission inventories.”
Author Response File: Author Response.pdf
Reviewer 4 Report
This paper describes the history and current status of ammonia mitigation technology and management in China, which is very meaningful and important for understanding the development of ammonia mitigation and guiding future mitigation regulation as well as environmental quality improvement. However, there are several issues that need to be clarified and details modified here.
Firstly, in the Introduction, it should be clearly stated what the research objectives and content scope of this paper are, and what meaningful information is provided for potential readers.
Secondly, in 4.1 Livestock and poultry, the content is too much inked on low protein feeding technologies, and there is almost no mention of technologies regarding manure storage, treatment, and application aspects, so please make appropriate adjustments and additions.
Thirdly, in 4.3Country/regional Comparison, the description of the differences between China and other countries or regions, as well as the aspects that need to be improved, is not clear, so please describe the emission reduction technologies, targets, management mechanisms and programmes appropriately.
Below are some suggestions for specific textual changes:
Lines 47-48:The description is not precise enough, nitrogen loss is not only ammonia volatilisation, but also leaching and denitrification.
Lines 296-297: Mechanical deep application has been widely used in rural areas at a very high percentage, probably for wheat and rice fertiliser is still spread, it should be described separately for different crops.
Rows 347-351: The description of the improvement of ammonia emission inventories is too general and should be properly described in terms of estimation methods and emission factors or activity data.
Lines 354 - 355: It seems that the proportion of technology application, economic benefits and ancillary measures need more attention and improvement than the effectiveness of application.
Author Response
Response to Reviewer’ s Comments
Dear reviewer,
We would like to express our gratitude to you for the opportunity to review and revise our manuscript agronomy-2589162 entitled “Management and reduction techniques strategies of ammonia emission in agricultural sectors in China”. These comments are of great help to us in revising and improving the manuscript. We made revisions one by one based on the comments of the reviewers. At the same time, the content and grammar of the manuscript was checked. We hope that this manuscript will be considered by the agronomy. The following are the responses and modifications.
Comments and Suggestions for Authors
This paper describes the history and current status of ammonia mitigation technology and management in China, which is very meaningful and important for understanding the development of ammonia mitigation and guiding future mitigation regulation as well as environmental quality improvement. However, there are several issues that need to be clarified and details modified here.
Firstly, in the Introduction, it should be clearly stated what the research objectives and content scope of this paper are, and what meaningful information is provided for potential readers.
Response:
Thank you very much for pointing out the critical problem. It is true that the introduction section in the previous manuscript was not organized well. The purpose of the study was not clearly stated. Therefore, we have reorganized the introduction.
Line 61: “Estimates of NH3 emissions rely primarily on the multiplication of activity levels of emission sources with emission factors [12]. Data on the activity level of a single source are easier to obtain, while data on local emission factors are more difficult to obtain. The emission factor method, which was widely used in early research, often used a single emission source activity level, such as multiplying the year-end inventory of livestock and poultry such as cattle and sheep by the corresponding emission factor in the statistical yearbook. The emission factors are directly calculated using foreign data or the average values of multiple foreign ammonia emission factors [12, 13]. The uncertainty in the results generated by this calculation method mainly comes from the differences between foreign emission factors and actual emission factors in various regions of China.
Various policy measures have been proposed for the control of ammonia emissions. This includes clear provisions in the national law Air Pollution Prevention and Control Law of the People's Republic of China [14], as well as the special action plan Three-Year Action Plan to Fight Air Pollution [15] to address air pollution control. In terms of measures, technical guidelines such as the Technical Guideline on Environmental Safety Application of Chemical Fertilizer [16] provide a basis for ammonia emission cases. However, it can be observed that in implementing ammonia emission control, although the goal of reducing ammonia emissions has been proposed, this goal has not been quantified, and the implementation of specific emission reduction measures also needs to be further improved. The effective-ness of ammonia emission control in various regions needs to be evaluated.
Based on this, the research objectives of this paper are 1) to briefly sort out China's goals and policies on ammonia emission control and the relationship between government departments in the decision-making system; 2) to summarize the methods and results of ammonia emission inventories at different regional scales in recent years, and to understand the changes in China's ammonia emissions during the period of 1980-2019; and 3) to propose emission reduction measures in the areas of livestock and poultry farming and fertilizer application to farmland based on the goals and policies and the results of the ammonia emission inventories.”
Secondly, in 4.1 Livestock and poultry, the content is too much inked on low protein feeding technologies, and there is almost no mention of technologies regarding manure storage, treatment, and application aspects, so please make appropriate adjustments and additions.
Response:
Thanks to the reviewer for this suggestion. Section 4.1 has been revised. The description on storage and handling of manure has been added. Specifics are given below:
Line 364: “In addition to low-protein feed, which controls NH3 emission in terms of nitrogen input, it is also possible to treat livestock manure to reduce NH3 emission from manure. Volatilization of NH3 will be higher when urine is in prolonged contact with feces. There-fore, to reduce the potential for NH3 volatilization, urine and feces should be separated quickly to reduce the contact between urease in feces and urea in urine [53]. Studies have shown that flushing every 2-3 h using the water-flush technique can effectively reduce ammonia volatilization by 14-70% [59]. Composting is one typical way of bio-treatment of animal manure. In composting, nitrogen in feces is converted to ammonium nitrogen through NH3 and then volatilizes as NH3. Measures such as controlling C/N ratio, ventilation and additives can reduce NH3 emission [60]. When a composting exhaust filter is used during the composting process, the emission reduction efficiency of NH3 is between 36% and 94% [61]. For large-scale aquaculture enterprises, waste gas can be collected by acid scrubbers or bio-trickling filters to convert NH3 into ammonium sulfate or nitrate substances, with NH3 reduction rate of over 70% [62]. Regarding internal and external exhaust gas from housing, most large-scale breeding enterprises in China have airtight housing facilities. A negative pressure environment is maintained in the housing and NH3-containing waste gas is collected and discharged after pickling. However, since acidic chemicals are currently controlled, the actual operation of pickling equipment is not ideal [63].”
Thirdly, in 4.3Country/regional Comparison, the description of the differences between China and other countries or regions, as well as the aspects that need to be improved, is not clear, so please describe the emission reduction technologies, targets, management mechanisms and programs appropriately.
Response:
Thank you very much for this constructive suggestion. We have modified the Country/regional comparisons section. China's emission reduction strategy has been compared with the European Union and the United States. And based on this, the relevant contents of emission reduction technologies, targets, management mechanisms and projects have also been described. As follow:
Line 453: “Although it started late, NH3 reduction in China is now a national program and requirement. Regarding NH3 emission control, national laws require that livestock and poultry breeding and farmland fertilization to pay attention to reducing NH3 emissions [44]. Specific action plans also emphasize the importance of NH3 reduction. The environ-mental protection department and agricultural department have policy documents that provide such technical advice. Irrespectively, China’s current NH3 emission control is un-clear about emission reduction targets and applications of emission reduction measures. Although laws and policy documents stipulate requirements for NH3 emission control, these requirements need further clarification. The practices of the European Union and the United States can provide reference for China's NH3 emission reduction. Establishing a complete technical framework for NH3 emission reduction is an important step. The next is to propose effective measures for key emission sources and key regions. In addition, more localized measures should be proposed, taking into account the local soil and aquaculture situation in China.”
Below are some suggestions for specific textual changes:
Lines 47-48: The description is not precise enough, nitrogen loss is not only ammonia volatilisation, but also leaching and denitrification.
Response:
Thanks for this suggestion. It has been corrected.
Line 48: “In addition to being absorbed by crops for growth, N fertilizers in farmlands are con-verted into NH3 and then volatilized. As well, leaching and denitrification are among the pathways of nitrogen loss.”
Lines 296-297: Mechanical deep application has been widely used in rural areas at a very high percentage, probably for wheat and rice fertiliser is still spread, it should be described separately for different crops.
Response:
We strongly agree with the reviewer on the differences in fertilization methods for different crops. So, the previous manuscript has been revised.
Line 417: “At present, large-scale domestic cultivation is realized through deep mechanical application of nitrogen fertilizers. Mechanical deep application for wheat and rice fertilization is also used in some rural areas. While in some areas where there are labor shortages, fertilizers are still applied by direct spreading.”
Line 347-351: The description of the improvement of ammonia emission inventories is too general and should be properly described in terms of estimation methods and emission factors or activity data.
Response:
Thank you so much. The description of the revised ammonia emission inventory is more detailed, supplementing the estimation methodology and activity data.
Line 469: “This paper provides an overall overview of the management and reduction strategies for agricultural NH3 emissions in China. The control of ammonia emissions in China has gone through a process of development from emission standards to technical guidelines to national strategic control. Cooperation among governmental departments based on the national strategy is conducive to promoting the realization of ammonia emission reduction targets. Due to the differences in calculation methods, the results of NH3 emission inventories at different scales across the country vary widely. This makes the control of regional ammonia emissions more difficult, and the current status of NH3 emissions and emission reduction targets are difficult to be quantified in a uniform manner. In terms of technical measures to reduce emissions, more detailed technical operation guidelines are readily available. But the application of these measures in the relevant industries is not obvious enough, and the effectiveness of the reduction technologies in the field needs to be further evaluated.
The strategy of NH3 emission reduction should still be continued. For government departments, a better regional cooperation mechanism should be established. At the same time, the existing mechanism should be made more mature and publicized, including the provision of a more complete ammonia emission inventory, emission reduction targets and emission reduction measures in the relevant regions. In addition, more localized experiments need to be conducted to obtain more accurate emission factors. Improvement of localized models needs to be a priority. This will reduce the uncertainty of NH3 emission estimates.”
Lines 354 - 355: It seems that the proportion of technology application, economic benefits and ancillary measures need more attention and improvement than the effectiveness of application.
Response:
We strongly agree with the reviewer's opinion and have made corresponding modifications. As follows:
Line 489: “In terms of specific emission reduction measures, low-protein feeding technology, large-scale livestock and poultry farming, pilot projects on confined negative-pressure farming, as well as soil-formula fertilization and increasing the proportion of non-ammonium nitrogen fertilizers should be further promoted. The proportion of technology applications, economic benefits and supporting measures need more attention.”
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Thank you for all the corrections you made. I think that now the quality of manuscript has improved significantly.
Reviewer 4 Report
The authors have made careful revisions and added important graphical information. Recommended for acceptance for publication.
