A Comparison of the Qualitative Characteristics of Pellets Made from Different Types of Raw Materials

Round 1

Reviewer 1 Report

Dear authors,

You have carried out some useful research. I do have a few comments and questions that you might want to respond to in a next version.

Let me start with the English language. I am not going to go through the whole text with proposals for improvement, because that isn’t my job, but I will discuss your summary by way of example. Generally, you tend to make sentences more complicated and longer than necessary. I suggest you ask a person who is more fluent in English to make the text more readable.

Line 15: has -> the

Line 22/3: You use the expression ‘on the other hand’ several times in the paper without mentioning ‘on the one hand’. In most cases, you can simply leave out ‘on the other hand’. Here, you can replace ‘On the other hand, the same was not detected’ by ‘This was not the case’.

Line 24: ‘whose’ can only refer to persons; here it should read; ‘the values of which’.

Line 27: showed as well -> also showed (or ‘as well’ at the end of the sentence).

Line 30: ‘allow to’ can be deleted

Now to your text: minor and somewhat more important comments/questions.

Line 59/60: Can this be read as ‘between 40 and 800 kg/m^-3’? The sentence now contains two ranges and it is not clear what they refer to.

Line 66-90: It would be more interesting of you had data for more than just two/three years. Moreover, the data in this section don’t seem to fit. In 2020 European production was 23 million tons; in 2021 EU27 production was 26 million tons. These 26 million are supposed to be 48.3% of world production of ‘over 40 million tons’. Clearly, 26 is far more than 50% of 40. In line 76, you speak of 1.5 tons, whereas you are speaking of millions of tons elsewhere. 1.5 tons is negligible in this context – or do you mean 1.5 million?

Line 92: What crises in the housing sector are you referring to?

Line 104/5: I would suggest: ‘using wood products defined as waste, could be a means to contain the increase …’.  It is certainly not an alternative to containing increasing prices.

 

Line 116: In the summary, in Table 4 and in your conclusions, you refer to (reference) legislation. Here you are mentioning regulation. Nowhere in the paper becomes clear what you refer to. It may be that you are referring to ISO EN 17225-2, which however is only a standard. A standard is not a law. Is there any national or EU legislation/regulation that forces suppliers and/or users of pellets to conform to this standard? If not, your paper only shows that is difficult to produce pellets that fulfil all requirements of the standard. If there is a regulation that requires firms/consumers to the ISO standard, who is enforcing it?

 

Line 122: ‘artificial’ is the wrong expression here. I think you mean ‘planned’ forest as opposed to ‘natural’ forest.

 

Line 139: It is unclear to me what stems without branches are.

 

Line 176: ‘performed’ -> measured or determined.

 

187 and 194: typologies should be types.

 

Table 2 and 3: I have no idea how the letters in the table should be interpreted. The explanation ‘Different letters indicate statistically significant differences’ is insufficient at least for me.

 

Table 4: (text). Could it be that this should read ‘value classes to which the parameter belongs'? I read the table as follows: for Radiata pine the parameter Durability has a value that is lower than the lowest value in the lowest class defined by the standard. Correct?

 

Line 377: What ‘trend’ are you talking about? I suggest you simple say ‘As regards heating value’.

 

Line 453: I found your concluding paragraph difficult to follow. I suggest the following (if only to see if I understood it correctly):

 

Ultimately, if producers and users of pellets want to meet the quality standards established by the ISO, further research is needed to quantify the effects of the characteristics of the starting wood material on various parameters, paying also attention to seasonal variations, the type of harvest and storage of the same. Also, the process of obtaining the refined product needs to be taken into account.

see above

Author Response

Dear authors,

You have carried out some useful research. I do have a few comments and questions that you might want to respond to in a next version.

Let me start with the English language. I am not going to go through the whole text with proposals for improvement, because that isn’t my job, but I will discuss your summary by way of example. Generally, you tend to make sentences more complicated and longer than necessary. I suggest you ask a person who is more fluent in English to make the text more readable.

 

Line 15: has -> the

Done

 

Line 22/3: You use the expression ‘on the other hand’ several times in the paper without mentioning ‘on the one hand’. In most cases, you can simply leave out ‘on the other hand’. Here, you can replace ‘On the other hand, the same was not detected’ by ‘This was not the case’.

Done

 

Line 24: ‘whose’ can only refer to persons; here it should read; ‘the values of which’.

Done

 

Line 27: showed as well -> also showed (or ‘as well’ at the end of the sentence).

Done

 

Line 30: ‘allow to’ can be deleted.

Done

 

Now to your text: minor and somewhat more important comments/questions.

 

Line 59/60: Can this be read as ‘between 40 and 800 kg/m^-3’? The sentence now contains two ranges and it is not clear what they refer to.

The sentence was better specified.

 

Line 66-90: It would be more interesting of you had data for more than just two/three years. Moreover, the data in this section don’t seem to fit. In 2020 European production was 23 million tons; in 2021 EU27 production was 26 million tons. These 26 million are supposed to be 48.3% of world production of ‘over 40 million tons’. Clearly, 26 is far more than 50% of 40. In line 76, you speak of 1.5 tons, whereas you are speaking of millions of tons elsewhere. 1.5 tons is negligible in this context – or do you mean 1.5 million?

 

We did not correct what was requested because reviewer n° 2 suggested deleting the period from line 70 to line 90.

 

Line 92: What crises in the housing sector are you referring to?

We have modified the paragraph by referring to the growth in demand for pellets as reported in the discussions of the cited work

 

Line 104/5: I would suggest: ‘using wood products defined as waste, could be a means to contain the increase …’.  It is certainly not an alternative to containing increasing prices.

Done

 

Line 116: In the summary, in Table 4 and in your conclusions, you refer to (reference) legislation. Here you are mentioning regulation. Nowhere in the paper becomes clear what you refer to. It may be that you are referring to ISO EN 17225-2, which however is only a standard. A standard is not a law. Is there any national or EU legislation/regulation that forces suppliers and/or users of pellets to conform to this standard? If not, your paper only shows that is difficult to produce pellets that fulfil all requirements of the standard. If there is a regulation that requires firms/consumers to the ISO standard, who is enforcing it?

Thanks for the suggestion, we assumed that the reference to 17225-2 was clear, we changed the text

 

 

Line 122: ‘artificial’ is the wrong expression here. I think you mean ‘planned’ forest as opposed to ‘natural’ forest.

Replaced word.

 

Line 139: It is unclear to me what stems without branches are.

Sentence changed

 

Line 176: ‘performed’ -> measured or determined.

Done

 

187 and 194: typologies should be types.

Done

 

Table 2 and 3: I have no idea how the letters in the table should be interpreted. The explanation ‘Different letters indicate statistically significant differences’ is insufficient at least for me.

Added more specifics on this.

 

Table 4: (text). Could it be that this should read ‘value classes to which the parameter belongs'?

We have corrected the text in the table.

 

I read the table as follows: for Radiata pine the parameter Durability has a value that is lower than the lowest value in the lowest class defined by the standard. Correct?

Yes, it is correct

 

Line 377: What ‘trend’ are you talking about? I suggest you simple say ‘As regards heating value’.

Done

 

Line 453: I found your concluding paragraph difficult to follow. I suggest the following (if only to see if I understood it correctly):

Ultimately, if producers and users of pellets want to meet the quality standards established by the ISO, further research is needed to quantify the effects of the characteristics of the starting wood material on various parameters, paying also attention to seasonal variations, the type of harvest and storage of the same. Also, the process of obtaining the refined product needs to be taken into account.

Modified text

 

 

 

Reviewer 2 Report

Current topic.

Adequate title of the paper.

It is necessary to shorten the summary and the introductory part of the manuscript. There are general phrases and irrelevant data for this research and are not relevant for other researchers. In the discussion as many as 8 paragraphs without citing at least one literary source (citation).

Abstract: The last sentence (line 28-31) - This sentence does not belong in a summary.

Introduction: Line 35-44 Remove from the manuscript. Redundant, unnecessary and irrelevant to this research.

Line 62-63 The main consumer of what?

Line 62-69 These three paragraphs can be combined into one paragraph.

Line 70-90 Remove from the manuscript. Redundant, unnecessary and irrelevant to this research.

Line 100-105 A very long sentence. Make 2 or 3 shorter sentences. In addition, provide an appropriate citation (literary source).

Line 109 notwithstanding? Vague expression.

Line 115-117 The authors should especially emphasize the challenges and prospects for the future of biomass and bioenergy from forests.

Materials and Methods: No comments.

Discussion: Line 322-324 provide an appropriate citation (literary source).

Line 328-354 and 404-433 Seven paragraphs without citing at least one literary source (citation).

Conclusions: No comments.

References: Out of a total of 64 cited references, 9 references are up to 3 years old - satisfactory.

Comments for author File: Comments.pdf

The quality of English can be improved. Some words are inappropriate.

Author Response

Adequate title of the paper.

It is necessary to shorten the summary and the introductory part of the manuscript. There are general phrases and irrelevant data for this research and are not relevant for other researchers. In the discussion as many as 8 paragraphs without citing at least one literary source (citation).

Abstract: The last sentence (line 28-31) - This sentence does not belong in a summary.

Done

 

Introduction: Line 35-44 Remove from the manuscript. Redundant, unnecessary and irrelevant to this research.

Done

 

Line 62-63 The main consumer of what?

We added the word “pellet”

Line 62-69 These three paragraphs can be combined into one paragraph.

Done

Line 70-90 Remove from the manuscript. Redundant, unnecessary and irrelevant to this research.

Done

 

Line 100-105 A very long sentence. Make 2 or 3 shorter sentences. In addition, provide an appropriate citation (literary source).

We have reduced the length of the sentence. There are no citations because the text of lines 100-105 are our considerations.

Line 109 notwithstanding? Vague expression.

We have revised the sentence.

Line 115-117 The authors should especially emphasize the challenges and prospects for the future of biomass and bioenergy from forests.

Done

Materials and Methods: No comments.

Discussion: Line 322-324 provide an appropriate citation (literary source).

Done

Line 328-354 and 404-433 Seven paragraphs without citing at least one literary source (citation).

Line 328-354: the text directly concerns the discussions of the results reported in table 4. the citations referring to this part are those found in the lines 355-388 (citations 49 to 58).

Line 404-433: we have included three quotes regarding pellet mixtures.

Conclusions: No comments.

 

 

Reviewer 3 Report

The topic of the research work and manuscript is really interesting and provides new information. However there are some issues to be addressed towards its quality improvement before publication. In line 15, te word "has" should be checked again, probably grammatical error. In line 18 "derived". In line 24, the "didn’t" should be separated. In the abstract, the proportions of the materials is important to be presented in the text. In the abstract you should refer to the standard used for the evaluation of suitability of these biomass types for pellets production. Add the word "fuel" in the key words. In lines 66-67, could you probably provide as well relevant data of the recent years? In 103 line, check the "recourse". Even though the introduction is well-written and provides several important and interesting data, the state-of-the-art relevant to the topic of this manuscript (pellets produced from alternative feedstock) is not analysed and properly described, including the alternative biomass types utilized so far, ratios, advantages, drawbacks and challenges, the most significant findings related to their pellets properties and the potential of utilization of them etc. Do not forget, that each of the biomass types requires different pelletization conditions for example moisture content of biomass, temprature etc. (this aspect should be referred in the text). In materials and methods, try to correct thte names of species in order to be completed. Please provide reference on the 12% that you refer for the proper moisture content before pelletizing in 152 line. For all the equipment used, provide model, manufacturer, and country. In the discussion of results, the relevant study of https://doi.org/10.3390/en15082865 could be used in order to compare some of the properties of pellets sold nowadays in the market. Such a brief comment would be valueable to the readers and the drawing conlusions process in this article. Please provide as well a photograph of the pellets produced, it would be highly attractive and useful to the readership. In 448 line, there is a type error.

The use of passive voice would be more appropriate compared to the use of "we did this, we did that" in the descriptions, mainly in conclusions. The use of English language is generally satisfying in my opinion. In 452 line, the "would" instead of "did" would improve the meaning, please make a check again in this sentence. In 453 line, "research" should be changed in plural form.

Author Response

The topic of the research work and manuscript is really interesting and provides new information. However there are some issues to be addressed towards its quality improvement before publication.

 

In line 15, the word "has" should be checked again, probably grammatical error. In line 18 "derived".

Done

 

In line 24, the "didn’t" should be separated. In the abstract, the proportions of the materials is important to be presented in the text. In the abstract you should refer to the standard used for the evaluation of suitability of these biomass types for pellets production. Add the word "fuel" in the key words.

Done

 

In lines 66-67, could you probably provide as well relevant data of the recent years?

 

The data reported are the latest available with scientific value. We tried to look for data from 2022 but it is not available at the moment. The 2021 data has been published in the 2022 year reports.

 

In 103 line, check the "recourse". Even though the introduction is well-written and provides several important and interesting data, the state-of-the-art relevant to the topic of this manuscript (pellets produced from alternative feedstock) is not analysed and properly described, including the alternative biomass types utilized so far, ratios, advantages, drawbacks and challenges, the most significant findings related to their pellets properties and the potential of utilization of them etc. Do not forget, that each of the biomass types requires different pelletization conditions for example moisture content of biomass, temperature etc. (this aspect should be referred in the text).

 

The title of the work does not refer to pellets produced from alternative feedstock but refers to pellets produced from different types of raw materials, i.e. lignocellulosic biomass from dedicated plantations and pruning residues, nothing alternative to classic biomass for energy production. No reference is made to residues from the processing of food products, herbaceous plants etc. therefore it does not seem appropriate to delve into such a broad topic, even though it is certainly of interest, given that no type of innovative biomass is examined in the work.

 

 

In materials and methods, try to correct the names of species in order to be completed.

Done

 

Please provide reference on the 12% that you refer for the proper moisture content before pelletizing.

Done

 

 

In 152 line. For all the equipment used, provide model, manufacturer, and country.

Brand and model are already listed in the text, the other information could be non-essential, also considering that we had to cut the description of the equipment into materials and methods to reduce the similarity index detected.

 

In the discussion of results, the relevant study of https://doi.org/10.3390/en15082865 could be used in order to compare some of the properties of pellets sold nowadays in the market. Such a brief comment would be valueable to the readers and the drawing conlusions process in this article.

Thank you for the valuable suggestion, we have included and commented on the suggested work

 

 

Please provide as well a photograph of the pellets produced, it would be highly attractive and useful to the readership.

We could insert a photo for each group (mrf, agricultural residues, forest residues, urban green residues)

 

 

In 448 line, there is a type error.

We didn’t find the error.

 

Comments on the Quality of English Language

The use of passive voice would be more appropriate compared to the use of "we did this, we did that" in the descriptions, mainly in conclusions. The use of English language is generally satisfying in my opinion.

 

In 452 line, the "would" instead of "did" would improve the meaning, please make a check again in this sentence.

Done

 

In 453 line, "research" should be changed in plural form.

Done. The sentence has changed

Round 2

Reviewer 2 Report

I am pleased to state that the authors adopted the suggestions and prepared the manuscript for publication.

Reviewer 3 Report

As I have checked the authors have implemented the proposed changes in the revised verion of manuscript towards the improvement of their work. Almost all the changes have been implemented and in my opinion, the manuscript is well-prepared and organized enough to be accepted for publication in this journal. I remain at your disposal for any clarification.

The english language use has been highly improved.