Characterization of Volatile Organic Compound (VOC) Emissions from Swine Manure Biogas Digestate Storage
, Yongxing Chen 1,2, Fubin Yin 1,2, Wanqin Zhang 1,2, Hongmin Dong 1,2,* and Hongwei Xin 3Round 1
Reviewer 1 Report
this is a sound paper and generally well written. I am not to sure about the overall relevance as the emissions from the storage of digestate will in practise be low in most instances as these stores are likely to be covered (best practise and/or legislation).
The literature review used in the introduction is wide, but there are more recent publications (2017-2019) that are also relevant and not mentioned.
There is no mention anywhere in the paper (methods or results discussion) on the limitations of the methodology used and the implications on real live emissions or for that matter on the benefits of the method used.
the section on odorous VOC components can do with a short discussion on the impact of the odour components in terms of odour nuisance (odour units expected in the wider environment based on the flux measurements taken).
the section on hazardous VOC components ((by the way not hazardous compositions of VOCs; change to hazardous VOC compounds) should have a section on the dose response scenario. Just providing the concentrations doesn't give the reader much information. Please provide an estimate of the dose response relationship so that the reader gets a feel for the real danger of these components for those working/living in the vicinity of the digestate storage.
Please check the manuscript for any typos. Is abbreviation for litre L or l for this journal? missing superscripts (to many to count), missing address. Missing full version of OVOC, TVOC, VS, TS etc.
14 I am not convinced the term anthropogenic is relevant here. these are not strictly due to human activity.
20 OVOC (TVOC later on undefined)
34: Delfino et al should be omitted
42 variety
81 physiochemical (physical and chemical properties?)
84 mg L-1 mg l -1 lower case l and first of many super scripts missed)
106 name?
138 I have no issue with the abbreviations used in the table, but does this apply to all readers?!
147-151 the reader doesn't need to know exactly which software was used for analysis and plotting (shorter ref is fine).
Author Response
Response to Reviewer comments
Comment 1. This is a sound paper and generally well written. I am not to sure about the overall relevance as the emissions from the storage of digestate will in practise be low in most instances as these stores are likely to be covered (best practise and/or legislation).
Reply： VOCs emission may be low in covered storage of biogas digestate where coverage is required in some countries. However, coverage of digestate storage is not required in China, there are large poetntial emission of VOCs during biogas digestate storage. The aim of this study was to characterize VOCs and provide a scientific basis for mitigating VOCs emissions from stored biogas digestate, including coverage of digestate.
Comment 2. The literature review used in the introduction is wide, but there are more recent publications (2017-2019) that are also relevant and not mentioned.
Reply: Follwing 4 relevant publications in recent years have been added in revised MS .
[5] Giannadaki D , Giannakis E , Pozzer A , et al. Estimating health and economic benefits of reductions in air pollution from agriculture[J]. Science of The Total Environment, 2018, 622-623:1304-1316.
[14] Orzi V , Riva C , Scaglia B , et al. Anaerobic digestion coupled with digestate injection reduced odour emissions from soil during manure distribution[J]. Science of The Total Environment, 2018, 621:168-176.
[36] Li J J , Wu Y D , Zhang Y L , et al. Emission of odorous volatile organic compounds from a municipal manure treatment plant and their removal using a biotrickling filter[J]. Environmental Technology, 2015, 36(8):1050-1056.
[37] Carslaw, N., Shaw, D. 2019. Secondary product creation potential (SPCP): a metric for assessing the potential impact of indoor air pollution on human health. Environmental Science: Processes & Impacts.
Comment 3：There is no mention anywhere in the paper (methods or results discussion) on the limitations of the methodology used and the implications on real live emissions or for that matter on the benefits of the method used.
Reply: The sentence was added in “3.1 The abundance of VOCs and main classes” of revised MS. The sentence are as follow: This study investigated VOCs emission from same batch of biogas digestate, even though where same volume of digestate with sample size was added after sampling. However, fresh biogas digestate may be added to the storage frequently in actual storage process, which may cause higher VOCs emission due to the disturbing and fresh components.
Comment 4: The section on odorous VOC components can do with a short discussion on the impact of the odour components in terms of odour nuisance (odour units expected in the wider environment based on the flux measurements taken).
Reply: Due to the odour VOCs detected in this study were all lower than olfactory threshold，the odour nuisance was not included in this study, impact of the odour components on odour nuisance will be considered in future research with relative high concentration.
Comment 5: The section on hazardous VOC components ((by the way not hazardous compositions of VOCs; change to hazardous VOC compounds) should have a section on the dose response scenario. Just providing the concentrations doesn't give the reader much information. Please provide an estimate of the dose response relationship so that the reader gets a feel for the real danger of these components for those working/living in the vicinity of the digestate storage.
Reply: The text a on exposure risk of hazardous VOCs detected in this study was added in Chapter 3.4. Toxicity Value of detected 22 types of hazardous VOCs based on EPA’s Integrated Risk Information System (IRIS) are listed in STable 1 of supplementary information (SI).
Comment 6: Please check the manuscript for any typos. Is abbreviation for litre L or l for this journal? missing superscripts (to many to count), missing address. Missing full version of OVOC, TVOC, VS, TS etc.
Reply: corrected the abbreviation in revised MS.
Comment 7: L14 I am not convinced the term anthropogenic is relevant here. these are not strictly due to human activity.
Reply : “anthropogenic” be deleted in revised MS.
Comment 8: L 20 OVOC (TVOC later on undefined)
Reply : corrected in revised MS.
Comment 9: L 34: Delfino et al should be omitted
Reply: “Delfino et al” have been replaced by “Previous study” in revised MS.
Comment 10: L 42 variety
Reply: corrected in revised MS.
Comment 11: L 81 physiochemical (physical and chemical properties?)
Reply: corrected in revised MS.
Comment 12: L 84 mg L-1 mg l -1 lower case l and first of many super scripts missed)
Reply : corrected in revised MS.
Comment 13: L 106 name?
Reply : corrected in revised MS.
Comment 14: L 138 I have no issue with the abbreviations used in the table, but does this apply to all readers?
Reply : Full name has been added in table. Table1
Comment 15: L 147-151 the reader doesn't need to know exactly which software was used for analysis and plotting (shorter ref is fine).
Reply : Statistical analysis sector has been simplified in revised MS.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title: Characterization of Volatile Organic Compounds (VOCs) Emissions from Swine Manure Biogas Digestate Storage.
Authors: Yu Zhang, Zhiping Zhu, Yunhao Zheng, Yongxing Chen, Fubin Yin, Wanqin Zhang, Hongmin Dong, and Hongwei Xin.
Manuscript ID: atmosphere-537002
My comments:
This research article characterized VOCs emission from swine manure biogas digestate when stored for 5 day 25oC. Given the continued interest of the general public in odor mitigation, the study is timely and significant. Additionally, the study appears to be well-planned. Truly, this paper is a well-written, grammar is good, easy to follow, showed sequential flow of information, and the authors have demonstrated good knowledge of the overall problem. The materials and methods especially the GC-MS method, performance of the GC itself (MDL, % recoveries, etc.), QA/QC protocol and statistical method were well described. I also believe the authors have competently made the described measurements in the laboratory. Per my opinion, this paper would be published with minor correction as suggested below:
Authors are strongly authors to include a table on the performances of the GC_MS incorporating method detection limit (MDL) and span checking by spiking with a known concentration at a regular interval, percent analyte recoveries (GC), R2 of calibration equations (if applicable) for top 20 most abundant VOC species (as shown in the Table 4).
Author Response
Response to Reviewer
Comment 1 : This research article characterized VOCs emission from swine manure biogas digestate when stored for 5 day 25oC. Given the continued interest of the general public in odor mitigation, the study is timely and significant. Additionally, the study appears to be well-planned. Truly, this paper is a well-written, grammar is good, easy to follow, showed sequential flow of information, and the authors have demonstrated good knowledge of the overall problem. The materials and methods especially the GC-MS method, performance of the GC itself (MDL, % recoveries, etc.), QA/QC protocol and statistical method were well described. I also believe the authors have competently made the described measurements in the laboratory. Per my opinion, this paper would be published with minor correction as suggested below:
Reply: Thanks a lot for encourage.
Comment 2: Authors are strongly authors to include a table on the performances of the GC_MS incorporating method detection limit (MDL) and span checking by spiking with a known concentration at a regular interval, percent analyte recoveries (GC), R2 of calibration equations (if applicable) for top 20 most abundant VOC species (as shown in the Table 4).
Reply : The method detection limit, R2 of calibration equations for top 20 most abundant VOC species have been provided in Stable2 of supplementary information (SI).
Author Response File: Author Response.docx
