Influence of the Wood Species, Forest Management Practice and Allocation Method on the Environmental Impacts of Roundwood and Biomass

Round 1

Reviewer 1 Report

Interesting article, but with problems which must be mentioned.: 1) three different production types and the same productivity with MP, 2) use of machinery (processor) which is unnecessary in the given conditions (wrong terminology), 3) use of road construction and maintenance data, but only in one part...detailed comments are given below:

Lines 49-50, m3 exponent correction

Line 53: rephrase: “Operations related to logging, such as harvesting and forwarding” to “Harvesting operations i.e. felling, cutting and forwarding.

Line 122-123: Italic for latin names

Line 159: it is better to use “harvesting operations” than “logging” since it is a wider term which includes felling and cutting and primary transport (skidding, forwarding etc.)

Line 167: “with A harvester” the same with tractor and forwarder. What king of a tractor was it? A skidder or an adopted farm tractor, please specify.

Table 1. roundwood – letter D is in the lower part, please correct

Line 189 – you are mentioning that the productivity between three MP was the same and that you could not find appropriate data. Does this makes sense? You have three different production types and the same productivity for all of them. Choose one and compare the one you have chosen to the other two species. Maybe MP-plant would be the best choice.

Table 2: if you have CTL (harvester+forwarder system) why do you have an excavator-based processor? What is its job? A processor does not do timber extraction.

Chapters 4.1 and 4.2. and 4.3 are not discussion, but results. Forests journal  does not ask for a discussion paragraph so either move these parts to result, or write a discussion section covering and commenting other references with your results.

Author Response

Response to Reviewer 1 Comments

 

Point 1: Interesting article, but with problems which must be mentioned.: 1) three different production types and the same productivity with MP, 2) use of machinery (processor) which is unnecessary in the given conditions (wrong terminology), 3) use of road construction and maintenance data, but only in one part...detailed comments are given below:

Response 1: Firstly, the authors would like to express their gratitude for your revision and comments. Reviewer contributions have clearly improved the quality of the work presented in this document. The problems mentioned by the reviewer in this point were reviewed and changes were made in accordance with the comments given below.

 

Point 2: Lines 49-50, m3 exponent correction

Response 2: The exponent was amended.

 

Point 3: Line 53: rephrase: “Operations related to logging, such as harvesting and forwarding” to “Harvesting operations i.e. felling, cutting and forwarding.

Response 3: The sentence was rephrased.

 

Point 4: Line 122-123: Italic for latin names

Response 4: The format of Latin names was changed.

 

Point 5: Line 159: it is better to use “harvesting operations” than “logging” since it is a wider term which includes felling and cutting and primary transport (skidding, forwarding etc.)

Response 5: The nomenclature was changed.

 

Point 6: Line 167: “with A harvester” the same with tractor and forwarder. What king of a tractor was it? A skidder or an adopted farm tractor, please specify.

Response 6: Harvesting is performed with an adapted tractor and forwarding is performed with a skidder. The nomenclature was changed.

 

Point 7: Table 1. roundwood – letter D is in the lower part, please correct

Response 7: The authors did not understand the intention of this Point. It could be related with formatting. We re-formatted the Table 1.

 

Point 8: Line 189 – you are mentioning that the productivity between three MP was the same and that you could not find appropriate data. Does this makes sense? You have three different production types and the same productivity for all of them. Choose one and compare the one you have chosen to the other two species. Maybe MP-plant would be the best choice.

Response 8: The authors understood the point. However, the productivity data was not available for different production types. The productivity is related, not only with mechanical operations, but mainly with the environmental conditions (solar exposure, humidity, etc.). The influence of environmental conditions on the productivity of forest species is a complex issue and it is difficult to consider, at least within the scope of this study. In this study, we focused the work on the influence of mechanical operations in environmental impacts of forest products. Thus, as no analysis of the influence of mechanical operations on the productivity was found in the bibliography, the same yield was assumed for various forest management models.

 

Point 9: Table 2: if you have CTL (harvester+forwarder system) why do you have an excavator-based processor? What is its job? A processor does not do timber extraction.

Response 9: This operation was included in tables and text by mistake. This operation has been excluded from the analysis. 

 

Point 10: Chapters 4.1 and 4.2. and 4.3 are not discussion, but results. Forests journal does not ask for a discussion paragraph so either move these parts to result, or write a discussion section covering and commenting other references with your results.

Response 10: The chapters 4.1 and 4.2 was moved to the results section.

Author Response File: Author Response.docx

Reviewer 2 Report

• See attachment

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 2 Comments

 

Point 1: I found this study very interesting. However, after reading the introduction, and several times the methodology, I have not been able to continue with the review. It is an analysis with too many variables, scenarios, processes, forest operations, database operations, etc., which makes it difficult to follow in a simple way. Too many abbreviations are used for so many combinations of variables that every time I try to read I have to go back to look for the meaning of each abbreviation. It is a complicated paper. This does not mean in any way that the article is poorly written or does not present a robust methodology; it is just exhausting to read.

Response 1: Firstly, the authors would like to express their gratitude for your revision and comments. The authors understand the points and the issues raised by the reviewer and tried to make the article “more readable”. The changes made in the text were based on the reviewer's comments analysed below. In addition to the changes made in the main text, the comments of Reviewer 2 resulted in the proposal of a “Supplementary material” document.

 

Point 2: The difficulty in understanding the study starts from the abstract, where it is mentioned that the study quantifies and compares the environmental impacts of biomass and roundwood from different wood species under different forest management scenarios: planted, seeded, and naturally regenerated. Do biomass and roundwood per se have an environmental impact? Wouldn't it be better to say the system (or method) of biomass production, or the harvesting system? Production processes have an environmental impact. For example, a pencil does not have an environmental impact, but the whole production process of that pencil does.

Response 2: The authors agreed with the reviewer and changed the Abstract to: “This study quantifies and compares the environmental impacts of production systems of biomass and roundwood from different wood species (…)”

 

Point 3: Moreover, the authors state in the abstract: “the results showed that roundwood and biomass from eucalyptus had the highest environmental impacts in most of the categories. Which categories? Impact categories?

Response 3: Yes, it is “environmental categories”. The text was changed.

 

Point 4: In materials and methods, it is stated that “the aim of this study was to quantify and compare the environmental performance of various types of roundwood from different Portuguese forest management scenarios”. However, at the end of the introduction it is mentioned that “This study applied the LCA methodology to quantify the environmental impacts of various Portuguese forest management scenarios”. Environmental performance is not the same as environmental impact. Please be consistent in all parts of the text where the objective of the study is mentioned.

Response 4: It shall be “the aim of this study was to quantify and compare the environmental impacts of various types of roundwood from different Portuguese forest management scenarios”. The text was changed.

 

Point 5: Line 175-176: Site-specific data were calculated from companies’ inquiries and from literature. Cite all information sources consulted.

Response 5: The information sources were cited.

 

Point 6: Line 176-177: Whenever necessary, LCA databases were used as background data. Mention the cases where it was necessary to use LCA databases; for scenarios, forestry operations?

Response 6: The text was changed to give the cases that used background data, namely for site preparation, stand establishment, tending and harvesting operations.

 

Point 7: Line 179-180: The time related coverage was representative of one year from 2010 to 2020. What year exactly? Were average values used for each variable over the 10 years?

Response 7: It was used the mean values of the decade from 2010 to 2020 (mean data available at Ecoivent 3.0 database). The text was amended.

 

Point 8: Line 183-185: In order to obtain the results per cubic meter of roundwood under bark, the inputs and outputs were divided by the total volume of roundwood produced. What were the inputs and outputs? Please declare them. What does total volume mean? Is it the volume with bark, or is it the volume with bark plus the volume of branches?

Response 8: The inputs and outputs of production system of roundwood and biomass were given in Supplementary material document. The total volume is the volume of roundwood (with bark) plus the volume of branches (biomass). The text was amended.

 

Point 9: If the unit of study was 1 m3 under bark, what about with bark and branches? Are they left in the forest as a residue from harvesting? are they handled on the industry facilities? What is the environmental impact of bark as a secondary forest product?

Response 9: By mistake, the volume of roundwood was assumed “under bark”, but it was calculated “with bark”. The functional unit was amended in the text. Branches was accounted as biomass.

 

Point 10: In table 1, the total volume is the sum of roundwood and biomass. Back to the previous question, what is biomass in this case? is it bark and branches? is it bark, branches, tips and stumps? 

Response 10: Total volume was the sum of roundwood with bark and biomass (bio-residues from thinning and pruning operations and branches).

 

Point 11: In table 2, what does U, GLO, RER, row mean? 

Response 11: The nomenclature was given in caption.

 

Point 12: How many combinations of variables were used to measure environmental impact? For example, how were the variables in tables 1 and 2, or tables 2 and 4 combined, and how was the impact of each combination measured?

Response 12: The combination of variables was detailed in the main text. In addition, the quantification of variables for each combination was given in Table S1 and Table S2 of supplementary material document.

 

Point 13: In table 5, a factor of 0.5 was used to convert dry biomass to carbon, then by 3.67 to calculate the amount of carbon dioxide. Why was 0.5 used? Is the carbon content of the wood of each species not available? Justify.

Response 13: The calculation of carbon content followed the procedure given by EN 16449 standard for “Calculation of sequestration of atmospheric carbon dioxide”. The factors are described in standard. Since it is not the focus of this study, the procedure for calculation of carbon content was not detailed.

 

Point 14: How was the environmental impact calculated? For example, how was the global warming potential (GWP-t) calculated? in which units is GWP-t reported? or how was the PA calculated? This is no small thing, because the aim of the study is to quantify, which means to measure; therefore, the results must be quantities. Authors should describe how each impact was estimated and specify the units in which each impact is calculated.

Response 14: The calculation of environmental impacts followed the methodology given by EN 15804+A2 standard. This standard gives the procedures to quantify the impacts of each environmental category. Since this is a procedure commonly followed in LCA studies and regulated by environmental impact calculation standards, the calculation procedure has not been detailed. The units of each environmental category were given in Tables S3 and S4 of Supplementary material document.

 

Point 15: Results and discussion In line with my previous comment, the results should be quantities. The authors report the environmental impact per cubic meter as a percentage; but percentage of what? For example, MP_Seed had a relative impact of almost 75% of GWP-f; but how much is that 75%? 75% of how many Mg, Tg, Gg; parts per million?

Response 15: The results and its units for one cubic meter of biomass and roundwood were given in Table S3 and Table S4 of Supplementary material document. In the main document, the environmental impacts were shown normalised for each category, which means that for each environmental category the scenario with the higher impacts had 100% and the impacts of other scenarios are a relative percentage of that one. This is a procedure commonly followed in LCA comparative studies because makes the comparison easier to understand for “non-expert” readers and gives the sufficient information for “expert” readers. 

 

Point 16: The results presented in figures 2-7 should be presented in the units in which each environmental impact category was measured.

Response 16: The reason why the absolute environmental impacts were not shown in figures 2-7 were given in response 15.

 

Point 18: I am sure that the authors will have a clear and perhaps simple answer to each observation; but they must not forget that the paper must be clear for the readers to understand, not for the author. The potential audience must be thought of. Therefore, a restructuring of the methodology to make it simpler and easier to understand, as well as presenting the results in quantities rather than percentages, will surely make this article a very valuable contribution to the literature related to this topic.

Response 18: The authors expect that the new version of the paper (including the supplementary material) and the answers given to the reviewer made the article more understandable for experts and non-experts readers.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Line 15, 415: change to lower cases of letters for the tree species names change in the whole MS

Line 42: the same comment as the one above

Line 49, 50: cubic meter to superscript (check in all text for this)

Line 53: since you are using a skidder in some operations the term “skidding” should be used when roundwood is transported by a skidder. In order to cover both forwarding and skidding in this sentence use the term “primary transport” i.e. “Harvesting operations i.e. felling and cutting as well as primary transport;….” So basically when you were using a forwarder transport is called forwarding, and skidding is used for skidder. Please correct that in the entire article (be careful in the tables (2) as well.

Line 163: the harvesting itself was not done with an adopted tractor, primary transport was done with a tractor or? Did the tractor had a semi-trailer (the roundwood was driven in it ) or did it have a winch so the roundwood was dragged on the ground? You should clarify with what was the actual felling performed. Motor-manually with a chainsaw or it was fully mechanized with a harvester and then  you should include those parameters in the overall study….this comment refers also to the table 2 where you are again mentioning that the harvesting was done with an adopted tractor…

Lines 187-193: as I have mentioned in the previous review you should change your scenarios to three: MP plant, EUC plant and CRYPT plant. It is just not right to have the same productivity in all three MP scenarios, you are mentioning this in this paragraph that in this way it is not realistic, but still are using this “unrealistic data” because different data could not be found in the literature review. Your article will not be poorer if you have only three scenarios planation based with three species, I therefore strongly advise to change this in the whole article.

Author Response

The authors thank the reviewer for his comments. All the recommendations made by the reviewer have been analysed and considered in this new version. Please see the attached document. 

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript has been substantially improved in the corrected version. Virtually all comments and suggestions have been addressed by the authors. For the above, I have no further comments. Please check the text for possible editing errors.

Author Response

The authors thank the reviewer for his review.