A Review of Poultry Waste-to-Wealth: Technological Progress, Modeling and Simulation Studies, and Economic- Environmental and Social Sustainability

Round 1

Reviewer 1 Report

This work elucidates the potential of unlocking economic value from poultry waste. In my opinion, this work is well-organized and contains relevant information that will be beneficial to the readership of this journal. Therefore, I recommended the publication of this manuscript.

Author Response

Reviewer #1

This work elucidates the potential of unlocking economic value from poultry waste. In my opinion, this work is well-organized and contains relevant information that will be beneficial to the readership of this journal. Therefore, I recommended the publication of this manuscript.

 

Respond: Thank you very much for your valuable reviewing work. It is our honor to get your recognition of this work.

 

 

Reviewer 2 Report

Dear Authors,

I read the manuscript entitled: "A Review of Poultry Waste to Wealth: Technological Progress, Modeling and Simulation Studies, and Economic-environmental and Social Sustainability" by Long Zhang, Jingzheng Ren, and Wuliyasu Bai with great interest.

Your work is a very rich compendium of knowledge on the use of waste generated in poultry production, and the value of this waste from economic, environmental, and social points of view. An interesting part of the work is the section Conclusions and recommendations for further research, in which you present in an orderly manner conclusions and recommendations not only for future research but also for the government policy in the field of animal waste management (poultry waste).

I included my comments on the manuscript in the attached pdf version.

The most important of them are:

Row 29 please, change poultry treatment processes to Poultry waste treatment processes

Row 59: Please add the source of the graph in the References section.
Our World in Data. 2023. Available online: https://ourworldindata.org/grapher/global-meat-projections-to-2050 (accessed on DD month YYYY).

Row 63: Please add the source of the graph in the References section.
Our World in Data. 2023. Available online: https://ourworldindata.org/grapher/global-meat-production-by-livestock-type (accessed on DD month YYYY).

Row 93: "...Poultry manures (PMs) is a valuable natural fertilizer because it is a rich source of macro- and micronutrients for crops. The PMs differ in terms of chemical composition, which was determined by their origin. The use of PMs increases soil pH and decreases hydrolytic acidity (HAC) and increases the sum of base cations (SBC) and the cation exchange capacity (CEC) of the soil, thus, increasing the content of available nutrients. The application of this soil amendment promotes the accumulation of soil carbon and accelerates the rate of nutrient turnover, providing available organic substances and nutrients, which increase the activity of soil enzymes..."

You can add the reference: Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639 

In this publication, you will find a lot of useful information on the fertilizing value of poultry manure

Row 147: Please consider this waste as a raw material for the production of meat and bone meal (MBM). “…Meat and bone meal (MBM) can be a viable alternative to natural, organic and mineral nitrogen (N), and phosphorus (P) fertilizers because it is rich in N (approximately 80 g kg⁻¹), P (approximately 50 g kg⁻¹), calcium - Ca (approximately 100 g kg⁻¹), micronutrients, and organic matter (approximately 700 g kg⁻¹)

Nogalska, A.; Załuszniewska, A. The Effect of Meat and Bone Meal (MBM) on Crop Yields, Nitrogen Content and Uptake, and Soil Mineral Nitrogen Balance. Agronomy 2021, 11, 2307. https://doi.org/10.3390/agronomy11112307 

Nogalska, A.; Krzebietke, S.J.; Zalewska, M.; Nogalski, Z. The effect of meat and bone meal (MBM) on the nitrogen and phosphorus content and pH of soil. Agric. Food Sci. 2017, 26, 181–187. http://dx.doi.org/10.23986/afsci.64207 

 Row 275: Żołnowski et al. (2022) found that the poultry manures (PMs) enriched with mineral-microbial deodorizing preparations (MMDP) based on perlite and bentonite as well as the following microorganism strains Lactobacillus plantarum, Leuconostoc mesenteroides, Bacillus megatherium, B. subtilis, and Pseudomonas fluorescens had a more favorable effect on the physicochemical properties of the soil than PMs without the addition of MMDP.

Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639

Row 287: Why the authors did not indicate the basic use of waste from poultry farming and processing as unprocessed products - poultry manure (natural, dried, granulated) and processed (feather meal, meat, and bone meal) to improve the soil's abundance of nutrients and organic matter. These products do not need to be gasified, pyrolyzed, fermented, etc. It should also be noted that co-incineration with sewage sludge and/or municipal waste often excludes the use of ashes from combustion in agricultural production due to harmful elements, mainly heavy metals.

Row 307: organic

Row 307: pH

Row 350: Authors suggest that chicken litter contains a low level of alkali metals – is it true?
Poultry manure is characterized by the highest calcium content among the manures obtained from farm animals. The Ca concentration in the manure of turkey broilers and laying hens was on average, 44.77 and 99.80 g Ca kg^–1, respectively, which resulted from the experimental nature of poultry farming.

This content in PMs under production conditions is, on average, 16.2–24.0 g Ca kg^–1, while the Ca content in cow and pig manure amounts only to 4.2 and 4.4 g Ca kg^–1, respectively.

Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639

Row 428: What the authors think about Insect protein production from poultry wastes.
Can such a subsection be added to the manuscript?

Waste from poultry and bovine slaughterhouses can be used for black soldier fly larvae (BSFL) rearing, to turn it into valuable biomass as a circular bioeconomy technique;

https://doi.org/10.22034/gjesm.2023.01.03

The larvae of these insects, particularly BSFL, are voracious eaters of decaying organic matter, hence they have been successfully used to reduce waste streams including livestock (chicken, cow, swine, etc) manure, human excreta, poultry slaughterhouse waste, mill by-products, food waste, fruits, and vegetable waste, as well as palm oil industry waste. Black soldier fly larvae (BSFL), Hermetia illucens have proven to convert organic waste into high-quality nutrients for pet foods, fish, and poultry feeds, as well as residue fertilizer for soil amendment.

https://doi.org/10.1016/j.wasman.2021.12.044

Row 453-475: Thank you that the authors did not forget about the basic use of poultry waste in agriculture. Suggested articles can be cited here.

Since in section 5. Impacts of Poultry Waste to Wealth, the use of poultry waste in agriculture is listed first 5.1. Economic benefits; Agriculture: In my opinion, in the manuscript, this use should be placed at the beginning in subsection 4.1 Agricultural use. Right?

Then authors should discuss other technological options for use.

The use of waste for energy generation (energy recovery) should occur at the very end. This is the last stage in which we can still recover energy from waste. At the end, of course, ash provided it meets environmental standards, can be used in agriculture.

The authors may take my suggestions into consideration, but I especially recommend supplementing the manuscript with information on the fertilizing value of poultry manure, the use of meat and bone meals produced on the basis of poultry waste, and the use of poultry waste for the production of insect protein.

With regards

Reviewer

Comments for author File: Comments.pdf

Author Response

Reviewer #2

 

Dear Authors,

I read the manuscript entitled: "A Review of Poultry Waste to Wealth: Technological Progress, Modeling and Simulation Studies, and Economic-environmental and Social Sustainability" by Long Zhang, Jingzheng Ren, and Wuliyasu Bai with great interest.

Your work is a very rich compendium of knowledge on the use of waste generated in poultry production, and the value of this waste from economic, environmental, and social points of view. An interesting part of the work is the section Conclusions and recommendations for further research, in which you present in an orderly manner conclusions and recommendations not only for future research but also for the government policy in the field of animal waste management (poultry waste).

I included my comments on the manuscript in the attached pdf version.

Respond: Thank you very much for your valuable reviewing work and constructive comments. We have taken these suggestions and made corresponding revisions to this manuscript, and we believe that the quality of this manuscript have been quite improved based on your valuable suggestions.

 

Q1. Row 29 please, change poultry treatment processes to poultry waste treatment processes.

Respond: Thank you very much for this suggestion. We have replaced “poultry treatment processes” with “poultry waste treatment processes” in the list of keywords.

 

Q2. Row 59: Please add the source of the graph in the References section. Our World in Data. 2023. Available online: https://ourworldindata.org/grapher/global-meat-projections-to-2050 (accessed on DD month YYYY).

Row 63: Please add the source of the graph in the References section. Our World in Data. 2023. Available online: https://ourworldindata.org/grapher/global-meat-production-by-livestock-type (accessed on DD month YYYY).

Respond: Thank you very much for giving the suggestion on the source of data in Figure 1 and Figure 2. We have listed the data sources in the reference list as suggested.

Q3. Row 93: "...Poultry manures (PMs) is a valuable natural fertilizer because it is a rich source of macro- and micronutrients for crops. The PMs differ in terms of chemical composition, which was determined by their origin. The use of PMs increases soil pH and decreases hydrolytic acidity (HAC) and increases the sum of base cations (SBC) and the cation exchange capacity (CEC) of the soil, thus, increasing the content of available nutrients. The application of this soil amendment promotes the accumulation of soil carbon and accelerates the rate of nutrient turnover, providing available organic substances and nutrients, which increase the activity of soil enzymes..." You can add the reference: Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639 In this publication, you will find a lot of useful information on the fertilizing value of poultry manure.

Row 147: Please consider this waste as a raw material for the production of meat and bone meal (MBM). “…Meat and bone meal (MBM) can be a viable alternative to natural, organic and mineral nitrogen (N), and phosphorus (P) fertilizers because it is rich in N (approximately 80 g kg⁻¹), P (approximately 50 g kg⁻¹), calcium - Ca (approximately 100 g kg⁻¹), micronutrients, and organic matter (approximately 700 g kg⁻¹) (Nogalska, A.; Załuszniewska, A. The Effect of Meat and Bone Meal (MBM) on Crop Yields, Nitrogen Content and Uptake, and Soil Mineral Nitrogen Balance. Agronomy 2021, 11, 2307. https://doi.org/10.3390/agronomy11112307; Nogalska, A.; Krzebietke, S.J.; Zalewska, M.; Nogalski, Z. The effect of meat and bone meal (MBM) on the nitrogen and phosphorus content and pH of soil. Agric. Food Sci. 2017, 26, 181–187. http://dx.doi.org/10.23986/afsci.64207)

 Row 275: Żołnowski et al. (2022) found that the poultry manures (PMs) enriched with mineral-microbial deodorizing preparations (MMDP) based on perlite and bentonite as well as the following microorganism strains Lactobacillus plantarum, Leuconostoc mesenteroides, Bacillus megatherium, B. subtilis, and Pseudomonas fluorescens had a more favorable effect on the physicochemical properties of the soil than PMs without the addition of MMDP. (Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639)

Respond: Thank you very much for providing so much useful information and suggesting so many highly related articles as references. We have added the useful information to the corresponding parts in our manuscript to support the point of view in this study.

 

Q4. Row 287: Why the authors did not indicate the basic use of waste from poultry farming and processing as unprocessed products - poultry manure (natural, dried, granulated) and processed (feather meal, meat, and bone meal) to improve the soil's abundance of nutrients and organic matter. These products do not need to be gasified, pyrolyzed, fermented, etc. It should also be noted that co-incineration with sewage sludge and/or municipal waste often excludes the use of ashes from combustion in agricultural production due to harmful elements, mainly heavy metals.

Respond: This is a very good question. We have added some pretreatment processes and composting treatment in Section 4 as a technique of using poultry waste for agricultural application. In addition, we have also discussed the economic benefits of using poultry waste as agricultural fertilizer or soil amendment by incorporating the useful information suggested by the reviewers.

 

Q5. Row 307: organic, pH

Respond: Thank you very much for catching these mistakes. We have corrected them in the revised manuscript.

 

Q6. Row 350: Authors suggest that chicken litter contains a low level of alkali metals – is it true? Poultry manure is characterized by the highest calcium content among the manures obtained from farm animals. The Ca concentration in the manure of turkey broilers and laying hens was on average, 44.77 and 99.80 g Ca kg^–1, respectively, which resulted from the experimental nature of poultry farming. This content in PMs under production conditions is, on average, 16.2–24.0 g Ca kg^–1, while the Ca content in cow and pig manure amounts only to 4.2 and 4.4 g Ca kg^–1, respectively. (Żołnowski, A.C.; Bakuła, T.; Rolka, E.; Klasa, A. Effect of Mineral–Microbial Deodorizing Preparation on the Value of Poultry Manure as Soil Amendment. Int. J. Environ. Res. Public Health 2022, 19, 16639. https://doi.org/10.3390/ijerph192416639)

Respond: Thank you very much for providing so detailed data on the alkali metals contained in various animal manures. We have summarized this conclusion based on the work (Zhou, S.; Han, L.; Huang, G.; Yang, Z.; Peng, J., Pyrolysis characteristics and gaseous product release properties of different livestock and poultry manures: Comparative study regarding influence of inherent alkali metals. Journal of Analytical and Applied Pyrolysis 2018, 134, 343-350.). In the study of Zhou et al. (2018), the conclusion is derived by comparing the biogas yields from swine manure, dairy cattle manure, and beef cattle manure, broiler litter, and layer chicken litter through pyrolysis, while poultry litter and poultry manure are not exactly the same. To present a more comprehensive picture, we have also mentioned the facts of more alkali metals contained in poultry manure than other animal manure for discussion.

 

Q7. Row 428: What the authors think about Insect protein production from poultry wastes. Can such a subsection be added to the manuscript? Waste from poultry and bovine slaughterhouses can be used for black soldier fly larvae (BSFL) rearing, to turn it into valuable biomass as a circular bioeconomy technique (https://doi.org/10.22034/gjesm.2023.01.03). The larvae of these insects, particularly BSFL, are voracious eaters of decaying organic matter, hence they have been successfully used to reduce waste streams including livestock (chicken, cow, swine, etc) manure, human excreta, poultry slaughterhouse waste, mill by-products, food waste, fruits, and vegetable waste, as well as palm oil industry waste. Black soldier fly larvae (BSFL), Hermetia illucens have proven to convert organic waste into high-quality nutrients for pet foods, fish, and poultry feeds, as well as residue fertilizer for soil amendment. (https://doi.org/10.1016/j.wasman.2021.12.044)

Respond: That’s a very good point. In fact, using poultry waste for the production of insect protein is a bioconversion technology that has been widely used in waste treatment. We have taken this advice and added the application of poultry waste for the production of insect protein in Section 4.7 of the revised manuscript.

 

Q8. Row 453-475: Thank you that the authors did not forget about the basic use of poultry waste in agriculture. Suggested articles can be cited here.

Respond: Thank you very much for providing us so many useful references and information. We have discussed the application of poultry waste in agriculture here and added the suggested information and reference to support this application technique.

 

Q9. Since in section 5. Impacts of Poultry Waste to Wealth, the use of poultry waste in agriculture is listed first 5.1. Economic benefits; Agriculture: In my opinion, in the manuscript, this use should be placed at the beginning in subsection 4.1 Agricultural use. Right?

Respond: Thank you very much, and this is a very good suggestion. In this study, we do believe that poultry waste should be used as a primary way in agriculture. So in Section 4, we have taken your advice and added the technique of composting treatment and some pretreatment processes, which serve as techniques of using poultry waste in agriculture.

 

Q10. Then authors should discuss other technological options for use. The use of waste for energy generation (energy recovery) should occur at the very end. This is the last stage in which we can still recover energy from waste. At the end, of course, ash provided it meets environmental standards, can be used in agriculture.

Respond: Thank you for this suggestion. We have added the discussion on the technological options in the Section of recommendations for further research as follows: “As one of the sectors of broad agriculture, poultry production has generated numerous solid wastes. From the perspective of circular economy, the waste generated from agriculture should be reused for agricultural production at the very beginning, followed by other sectors. Thus, it is suggested to using poultry waste to produce organic fertilizer or soil amendment with priority”.

 

Q11. The authors may take my suggestions into consideration, but I especially recommend supplementing the manuscript with information on the fertilizing value of poultry manure, the use of meat and bone meals produced on the basis of poultry waste, and the use of poultry waste for the production of insect protein.

Respond: Thank you very much. These three points have widened the application of poultry waste from a broad perspective. We have taken these suggestions and added these technologies to our manuscript. Thank you again for your valuable suggestions.

 

Reviewer 3 Report

A Review of Poultry Waste to Wealth: Technological Progress, Modelling and Simulation Studies, and Economic-environmental and Social Sustainability

The author discusses in this review article the poultry waste management, by categorizes poultry waste as litter and manure waste, feathers waste, mortality waste, abattoir waste, and hatchery waste. The author discusses various modelling and simulation of the poultry wastes and six various technological approaches for poultry waste management. Furthermore, the economics, environmental and social aspects of the poultry to wealth are also evolved.

The problem studied in this manuscript is of the great technical and scientific importance for the researchers, but it needs some revisions and improvement to make it able to be published in this journal.  

-      The letter “E” in the heading of the manuscript should be capital.

-      The introduction should be improved and need to be discussed wisely. The literature included should be improved by inserting some of the following articles:

Petrillo, A., Colangelo, F., Farina, I., Travaglioni, M., Salzano, C., & Cioffi, R. (2022). Multi-criteria analysis for Life Cycle Assessment and Life Cycle Costing of lightweight artificial aggregates from industrial waste by double-step cold bonding palletization. Journal of Cleaner Production, 351, 131395.

Colangelo, F., Navarro, T. G., Farina, I., & Petrillo, A. (2020). Comparative LCA of concrete with recycled aggregates: A circular economy mindset in Europe. The International Journal of Life Cycle Assessment, 25, 1790-1804.

-      Line 77-81, the paragraph discussed in these lines are already discussed in the introduction (line 47-49). It should be improved.

-      In section 4, the important parameters for each and every technological process should be discussed.

-      Some pre-treatment technologies for poultry waste management if available in the literature should be added.

-      It should be added that which technological better suit for which type of the poultry waste.

-      In economic section, just two benefits are not enough, the author should add more.

-      If other sub section like 5.2 and 5.3 are not further divided, then the pointer in term of agriculture and energy recovery should be removed from sub section 5.1.

-      Section 6, “conclusion and future recommendation” should be write in separate section as both are two different things.

-      Some figures and results analysis should be added from the literature to ease reader understanding. For example, process diagram for each technological process should be adapted from literature.

-      Comparison should be drawn among various technological process and also among modelling and simulation.

-      The positive and negative aspects of the technological process should be added and similar for the modelling and simulation.

-      For each type of the poultry waste the author should discuss the technological process separately, for example, for litter waste all six technological approaches should be discussed. And at the end conclusive paragraph should be added to give the reader the idea that for which particular waste which type of the technological process will suit better.

Author Response

Reviewer #3

The author discusses in this review article the poultry waste management, by categorizes poultry waste as litter and manure waste, feathers waste, mortality waste, abattoir waste, and hatchery waste. The author discusses various modelling and simulation of the poultry wastes and six various technological approaches for poultry waste management. Furthermore, the economics, environmental and social aspects of the poultry to wealth are also evolved. The problem studied in this manuscript is of the great technical and scientific importance for the researchers, but it needs some revisions and improvement to make it able to be published in this journal.  

Respond: Thank you very much for your valuable reviewing work and comments for this manuscript. We have made corresponding revisions to this manuscript based on your comments and suggestions.

 

Q1: The letter “E” in the heading of the manuscript should be capital.

Respond: Thank you very much for pointing out this mistake. We have corrected it in the revised manuscript.

 

Q2: The introduction should be improved and need to be discussed wisely. The literature included should be improved by inserting some of the following articles:

Petrillo, A., Colangelo, F., Farina, I., Travaglioni, M., Salzano, C., & Cioffi, R. (2022). Multi-criteria analysis for Life Cycle Assessment and Life Cycle Costing of lightweight artificial aggregates from industrial waste by double-step cold bonding palletization. Journal of Cleaner Production, 351, 131395.

Colangelo, F., Navarro, T. G., Farina, I., & Petrillo, A. (2020). Comparative LCA of concrete with recycled aggregates: A circular economy mindset in Europe. The International Journal of Life Cycle Assessment, 25, 1790-1804.

Respond: Thank you very much. We have improved the part of introduction and incorporate the suggested references.

 

Q3: Line 77-81, the paragraph discussed in these lines are already discussed in the introduction (line 47-49). It should be improved.

Respond: Thank you very much for pointing out this problem. We have rewritten these sentences to avoid similar expressions that have been discussed above previously.

 

Q4: In section 4, the important parameters for each and every technological process should be discussed.

Respond: Thank you very much for this suggestion. We have added the important parameters for these processes in Section 3, including temperature, moisture, duration, blending ratio, etc. As can be seen, these parameters may vary with each other due to the different system designations and material feds.

 

Q5: Some pre-treatment technologies for poultry waste management if available in the literature should be added.

Respond: Thank you very much for this suggestion. We have added the pretreatment processes that are usually used in poultry waste management in Section 4 as follows: “Before poultry waste being recycled and reused, necessary pretreatment processes are needed. Aerobic process and anaerobic process are the most commonly pretreatment techniques used in poultry waste management, and these two processes are also the most frequently used technique of realizing poultry waste to wealth. In addition, some other pretreatment processes can also be applied in poultry waste management. For instance, electrochemical process is proved to be very effective for removing some physicochemical parameters such as turbidity, color, total suspended solids, total iron, aluminum, chemical oxygen demand, and biochemical oxygen demand; Alkaline pretreatment can be an effective way to reducing the lignin content of lignocellulosic biomass and increases the bio-digestibility in poultry litters without significant loss in carbohydrates”. In addition, aerobic composting and anaerobic digestion are specifically explained in subsection 4.1 and 4.2 respectively, as the primary ways of poultry waste management.

 

Q6: It should be added that which technological better suit for which type of the poultry waste.

Respond: Thank you very much. We have taken this advice and discussed the suitability of these processes for each type of poultry waste at the end of Section 4. And the discussion is as follows: “Based on the above-mentioned analysis, the suitable technologies for various poultry waste types are summarized. Poultry litter and manure waste can be valorized by almost all the technological processes, and composting and anaerobic digestion seems to be the most practical and economically feasible ones for agricultural application, energy recovery and feed production, and enzymatic treatment and pyrolysis are more suitable to deal with feather waste for feed production. As various bacteria and pathogen are contained in poultry mortality waste, abattoir waste and hatchery waste, and gasification, pyrolysis, microbial conversion can fully decompose or remove these harmful substances and recover energy and protein from these wastes. However, the performance of these technologies in treating different poultry wastes still need to be validated by process simulations and laboratory researches”.

 

Q7: In economic section, just two benefits are not enough, the author should add more.

Respond: Thank you very much for this comment. In fact, being used for agricultural fertilizer production and energy recovery are the major pathways to convert poultry waste to wealth. Therefore, we have paid great efforts to these two fields of poultry waste to wealth. In addition to being used for agricultural fertilizer production and energy recovery, we also discussed the application of poultry waste in other industry as follows: “In addition, poultry waste can also be utilized in some other industries. For in-stance, McGauran et al. (2021) estimated that the total profits to the polymer industry would be 1,96 million British pounds if using poultry bone, meal and feather as materials for production in the United Kingdom, indicating the possibility of improving the economic benefits of both the polymer and poultry industries. Besides, cheap edible or inedible fat and grease can be produced from the waste of poultry rendering plants, which have great potential to be used in producing non-livestock animal feed, chemical industrial products, and fuel blending agents with much lower cost than vegetable oils. The protein production from the rearing of insects and earthworm by using poultry waste as base material provided both additional high-quality animal protein sources for feed production and organic fertilizer or soil amendment for crop pro-duction”. We have written this part to enrich the application of poultry waste in other sectors in the revised manuscript.

 

Q8: If other sub section like 5.2 and 5.3 are not further divided, then the pointer in term of agriculture and energy recovery should be removed from sub section 5.1.

Respond: Thank you very much for this suggestion. We have reorganized this part and removed the terms of agriculture and energy recovery from subsection 5.1.

 

Q9: Section 6, “conclusion and future recommendation” should be written in separate section as both are two different things.

Respond: Thank you very much for this suggestion. We have separated the section of “Conclusions and recommendations for further research” into two separate sections of “Conclusions” and “Recommendations for further research” in the revised manuscript.

 

Q10: Some figures and results analysis should be added from the literature to ease reader understanding. For example, process diagram for each technological process should be adapted from literature.

Respond: Thank you very much for this valuable comment. We have described the results of the modelling and simulations adapted from literature. We think it would help readers to better understand these technological processes.

 

Q11: Comparison should be drawn among various technological process and also among modelling and simulation.

Respond: Thank you very much for this comment. We have made a thorough comparisons on the advantages and disadvantages of different poultry waste treatment processes, as presented in Table 1 in the revised manuscript.

 

Q12: The positive and negative aspects of the technological process should be added and similar for the modelling and simulation.

Respond: This is a very good suggestion. We have summarized the advantages and drawbacks for the reviewed poultry waste treatment techniques, and summarized their advantages and disadvantages as present in Table 1 in the revised manuscript.

 

Q13: For each type of the poultry waste the author should discuss the technological process separately, for example, for litter waste all six technological approaches should be discussed. And at the end conclusive paragraph should be added to give the reader the idea that for which particular waste which type of the technological process will suit better.

Respond: Thank you very much for this suggestion. We have discussed the suitability of these technological processes for each type of poultry waste at the end of Section 4. And the discussion is as follows: “Based on the above-mentioned analysis, the suitable technologies for various poultry waste types are summarized. Poultry litter and manure waste can be valorized by almost all the technological processes, and composting and anaerobic digestion seems to be the most practical and economically feasible ones for agricultural application, energy recovery and feed production, and enzymatic treatment and pyrolysis are more suitable to deal with feather waste for feed production. As various bacteria and pathogen are contained in poultry mortality waste, abattoir waste and hatchery waste, and gasification, pyrolysis, microbial conversion can fully decompose or remove these harmful substances and recover energy and protein from these wastes. However, the performance of these technologies in treating different poultry wastes still need to be validated by process simulations and laboratory researches”.