Review Reports - Cross-Linked Gelatine as a Binder in Wood Fibre Composites for Topsoil Protection

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please see the attached file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Response to Reviewer 1 Comments

Thank you very much for taking the time to review this manuscript. Please find the detailed

responses below and the corresponding corrections in track changes in the re-submitted files.

I have the following suggestions, which should be implemented :

1- In section 3.1, Line 168 and 173, more details are necessary about preparing of tannic acid mixture and the gelatine mixture. How can the author control the pH, and what is the percentage of added NaOH.

Authors thank the referee for the comment:

The pH is measured continuously: portable pH-meter pH 3110 with pH electrode with liquid electrolyte SenTix® 81 with temperature sensor NTC 30 kW both from WTW supplied by Th. Geyer GmbH & Co. KG (Renningen, Germany)

The percentage of added NaOH depended on the ID:

ID	m (NaOH) / %
5 R	0.28
6 R	0.48
7 R	0.27
8 R	0.53
9 R	0.28
5 H	0.44
6 H	0.85
7 H	0.44
8 H	1.13
9 H	0.46

2- In the material section, real photos of the wood fibers, gelatine powder, and Tannic acid chestnut powder must be added, and more details should be added to show the photos before and after mixing.

Authors thank the referee for the comment and photos have been added.

3- Line 190, “varied between the normal pH and the higher pH during the production of the composite”, what are the normal and the higher pH?

Authors thank the referee for the comment:

Normal pH is the regular pH of 9 (index R) and higher is 10-11 (index H), see also section 3.1 text under table 1

4- Eq. 1, is not clear. How can the author calculate the mass mID variation of ID 8?

Authors thank the referee for the comment:

Refers to the mass of tannic acid of each ID variation

5- Some of the specimen photos should be shown.

Authors thank the referee for the comment and photos of the specimens for the mechanical tests, shrinkage, and long-term study have been added.

6- The authors stressed on the subject statistically, while more focus should be given to the physics associated with real pictures of the outputs of the specimens.

The authors are grateful for the comment. An abstract of physical interaction was added in the shrinkage section (ll 390 ff)

7- How long does it take for the mass to dry in the oven? And why specific at 103 °C?

Authors thank the referee for the comment:

The duration depends on the sample size, that was why constant mass was ensured.

Drying at (103 ± 2) °C is a standardized procedure in wood technology, ensuring an evaporation of water without degradation of other wood constituents.

8- What is the difference between Eq. 2 and Eq. 3? Both gave the moisture content?

Authors thank the referee for the comment:

Refers to different experimental set-ups and different mass

9- Section 3.2.1 Water Uptake should be replaced by moisture content.

As for soil conditioners, it is crucial to consider the water uptake in relation to the weight after absorption rather than the initial weight. The authors want to retain the term 'water uptake'.

10- Samples of the moisture content and the shrinkage content should be shown.

Authors thank the referee for the comment and photos have been added.

11- Line 216 and 217, how can the author control the RH at 85% and 65%?

Authors thank the referee for the comment:

Espec climate chamber PL-3KPH -40 °C to 150 °C

12- “Error! Refer- 226ence source not found” appears in many places of the manuscript.

The authors are unable to verify this message in your document.

13- How did the authors measure Δp in Eq. 6? Nomenclature must be added.

Δp was set to 1404 Pa as given in EN 12572:2016 Table 2. An derivation of the differential pressure as well as nomenclature was added toe he section.

14- More details about Tensile Strength: How the sample was prepared, what machine was used to do that, force deflection, stress strain curves should be added for the specimens,….etc

Authors thank the referee for the comment:

Preparation as described in section 3.1 and then cut to size More details are given in section 3.2.4

Before the test

15- “…..and were installed outdoors in a trough, tilted at an angle of 30°…” A photo of the trough and the sample should be added.

Authors thank the referee for the comment and photos have been added.

16- The figures presenting the results are not clear. What is the overall trend? It will be better if the authors look for clearer figures to present their data.

The overall trends can be summarized as follows: increasing wood fibre content generally enhanced the dimensional stability of the composites by reducing cross-sectional shrinkage, while higher gelatine and tannic acid contents improved cohesion, tensile strength, and weathering resistance. Conversely, elevated humidity resulted in reduced tensile strength and stiffness, reflecting the moisture sensitivity of the gelatin matrix. Despite the hydrophilic nature of the fibres, the water vapour permeability of all formulations remained within the typical range reported for biodegradable mulch films. These general tendencies are highlighted in the discussion part.

17- Please see “RILEM-TC. Test for the determination of modulus of rupture and limit of proportionality of thin fibre reinforced cement sections. In RILEM Technical Recommendations for the Testing and Use of Construction Materials; CRC Press: Boca Raton, FL, USA, 1994”.

We appreciate the reviewer’s suggestion to consider the RILEM-TC (1984) test method. But as far as the authors understand was this procedure developed for fibre-reinforced cementitious materials and primarily addresses flexural behaviour, including the determination of the modulus of rupture and the limit of proportionality under bending. As the present study investigates biopolymer-based wood fibre composites, which differ fundamentally from mineral-bonded systems in structure, stiffness, and failure mechanisms, the RILEM-TC method is not directly applicable. Instead, uniaxial tensile testing under controlled climatic conditions was selected as a more suitable approach for evaluating the mechanical response of the biopolymer matrix and fibre–matrix interaction.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript entitled “Cross-Linked Gelatine as Binder in Wood-Fibre Composites for Topsoil Protection” has been carefully reviewed. The topic is timely and relevant, addressing the pressing need for sustainable and biodegradable alternatives to conventional plastic-based mulching films. The study is well-structured and methodologically sound, with a comprehensive set of experiments. However, several issues related to clarity, novelty claims, methodological details, and contextual discussion need to be addressed.

Introduction

Provides a comprehensive overview of the context of topsoil covers (TSCs) and their role in agriculture and forestry.

Cites relevant literature on synthetic plastics, biodegradable polymers, and natural mulches.

Establishes a clear research gap: the need for biodegradable, low-cost, multifunctional TSCs.

Motivates the choice of gelatin–tannin as a binder system well.

The introduction is somewhat repetitive: the first two paragraphs repeat the description of TSCs and plastic films. This could be condensed for clarity.

References are numerous but sometimes redundant (e.g., multiple citations for similar claims on plastics and biodegradable polymers). Consider streamlining.

The novelty claim (“for the first time”) should be carefully justified with stronger evidence that no similar gelatin–fibre systems exist.

The hypothesis is implicit but not explicitly stated. Authors should clearly formulate the researc question (e.g., “We hypothesize that cross-linked gelatin reinforced with wood fibres can provide sufficient mechanical strength, dimensional stability, and biodegradability for use as TSCs.”).

Materials and Methods

The materials are described with commercial names, suppliers, and specifications, ensuring reproducibility.

Experimental design includes both factorial variation (gelatin, fibre, tannin contents) and systematic variation of pH and tannic acid concentration.

Multiple characterization techniques are employed: water uptake, shrinkage, permeability, tensile strength, and long-term weathering.

Statistical methods (Kruskal-Wallis and Dunn-Sidak) are appropriate given the lack of normal distribution.

The description of the composite preparation is detailed but could be clarified with a schematic flowchart (gelatin prep → tannin prep → mixing → drying).

Exclusion of IDs 1–4 due to “rapid degradation” is mentioned but not justified with data. At least brief evidence or reasoning should be reported.

The statistical section (ANOVA description) is overly long and repetitive; consider moving details of boxplot conventions to supplementary material.

Weathering tests are described with meteorological data, but no clear rationale for the chosen 46-week duration is provided. Why 46 weeks instead of 12 months?

It would be useful to include replicates/sample sizes systematically in a summary table instead of scattered through text.

Results and Discussion

The results are presented with statistical comparisons, boxplots, and tabulated data, which improves transparency.

Discussion links experimental outcomes with literature (e.g., comparison of water vapour permeability to PE and other biopolymers).

Long-term weathering study adds significant value and strengthens applicability of findings.

The results section is very long, with extended descriptions of figures that sometimes restate obvious trends. Condensing narrative while highlighting key findings would improve readability.

Discussion sometimes lacks depth — for example, mechanical performance (tensile strength up to 17 MPa) should be contextualized with typical values of PE or PLA mulching films.

Water uptake and ageing behavior are described in detail, but implications for field performance are not sufficiently explored. For instance: would higher uptake compromise mulch functionality under rainfall?

Shrinkage results show wood fibres limit deformation, but the mechanism (mechanical interlocking, dimensional restraint) could be better explained.

No clear link is made between laboratory tests and end-use performance in real soil/plant growth conditions. Field validation is missing.

Figures are numerous and complex. Consider moving some data (e.g., detailed tannin variations) to supplementary materials.

Conclusions

Conclusions summarize the main findings well (dimensional stability, water uptake, mechanical properties, biodegradability).

Highlights the potential of gelatin–wood fibre composites as sustainable TSCs.

The conclusions are somewhat overstated. Claims of “promising technology” should be tempered by acknowledging limitations: relatively high water absorption, need for optimization, and lack of field trials.

Practical considerations such as cost, scalability, and sourcing of gelatin/tannin are not addressed. These would strengthen the applied relevance.

Authors should provide a short outlook with next steps (e.g., pilot-scale production, greenhouse/field trials).

Author Response

Response to Reviewer 2 Comments

Thank you very much for taking the time to review this manuscript. Please find the detailed

responses below and the corresponding corrections in track changes in the re-submitted files.

Introduction

Provides a comprehensive overview of the context of topsoil covers (TSCs) and their role in agriculture and forestry.

Cites relevant literature on synthetic plastics, biodegradable polymers, and natural mulches.

Establishes a clear research gap: the need for biodegradable, low-cost, multifunctional TSCs.

Motivates the choice of gelatin–tannin as a binder system well.

The introduction is somewhat repetitive: the first two paragraphs repeat the description of TSCs and plastic films. This could be condensed for clarity.

Authors thank the referee for the suggestion and the first two paragraphs have been summarized for clarity.

References are numerous but sometimes redundant (e.g., multiple citations for similar claims on plastics and biodegradable polymers). Consider streamlining.

The redundant references have been removed and the introduction section seems to be keep somehow more on the main theme.

The novelty claim (“for the first time”) should be carefully justified with stronger evidence that no similar gelatin–fibre systems exist.

Authors thank the referee for the comment and the claim has been removed.

Authors thank the referee for the comment. The suggested statement has been added to the manuscript.

Materials and Methods

The materials are described with commercial names, suppliers, and specifications, ensuring reproducibility.

Experimental design includes both factorial variation (gelatin, fibre, tannin contents) and systematic variation of pH and tannic acid concentration.

Multiple characterization techniques are employed: water uptake, shrinkage, permeability, tensile strength, and long-term weathering.

Statistical methods (Kruskal-Wallis and Dunn-Sidak) are appropriate given the lack of normal distribution.

The description of the composite preparation is detailed but could be clarified with a schematic flowchart (gelatin prep → tannin prep → mixing → drying).

Authors agree with the referee, and Figure 3 has been added to show the sample preparation process schematically.

Exclusion of IDs 1–4 due to “rapid degradation” is mentioned but not justified with data. At least brief evidence or reasoning should be reported.

Authors thank the referee for the comment. As explained in the manuscript, these formulations were discarded during preliminary qualitative evaluations. These formulations did not fulfil the basic requirements for TSCs (e.g., mechanical integrity, water barrier properties, etc.). Adding further data would be redundant and would not add any value to the manuscript, which is already quite comprehensive.

The statistical section (ANOVA description) is overly long and repetitive; consider moving details of boxplot conventions to supplementary material.

Authors thank the referee for the comment. The statistical section is fundamental to describing the methodology adopted. Therefore, this section should be maintained in the main manuscript. However, in light of the referee’s observations, the section has been streamlined and summarized.

Weathering tests are described with meteorological data, but no clear rationale for the chosen 46-week duration is provided. Why 46 weeks instead of 12 months?

Authors agree with the referee; however, for technical reasons, the test was stopped after 46 weeks (approximately 11 months). The data collected still provides reasonable and interesting results.

It would be useful to include replicates/sample sizes systematically in a summary table instead of scattered through text.

Authors thank the referee for the comment and have added Table 6 to indicate the number of replicates for each test.

Results and Discussion

The results are presented with statistical comparisons, boxplots, and tabulated data, which improves transparency.

Discussion links experimental outcomes with literature (e.g., comparison of water vapour permeability to PE and other biopolymers).

Long-term weathering study adds significant value and strengthens applicability of findings.

The results section is very long, with extended descriptions of figures that sometimes restate obvious trends. Condensing narrative while highlighting key findings would improve readability.

Authors thank the referee for the comment and the result section has been summarized were possible.

Discussion sometimes lacks depth — for example, mechanical performance (tensile strength up to 17 MPa) should be contextualized with typical values of PE or PLA mulching films.

Authors thank the referee for the suggestion and values of typical mulching films were added in the manuscript as reference.

Authors thank the referee for the comment. The implications regarding the performance of these materials under rainfall were investigated further during the field test as stated in the future perspectives.

Shrinkage results show wood fibres limit deformation, but the mechanism (mechanical interlocking, dimensional restraint) could be better explained.

Authors thank the referee. A section was added.

No clear link is made between laboratory tests and end-use performance in real soil/plant growth conditions. Field validation is missing.

Authors agree with the referee. However, this study aims to systematically characterise the composites produced from a laboratory perspective. Field tests have already been planned and carried out, and some of the results will be published very soon in separate papers.

Figures are numerous and complex. Consider moving some data (e.g., detailed tannin variations) to supplementary materials.

Authors agree with the referee and some results have been moved to the Appendix A.

Conclusions

Conclusions summarize the main findings well (dimensional stability, water uptake, mechanical properties, biodegradability).

Highlights the potential of gelatin–wood fibre composites as sustainable TSCs.

Authors agree with the referee and the claim has been removed.

Practical considerations such as cost, scalability, and sourcing of gelatin/tannin are not addressed. These would strengthen the applied relevance.

Authors thank the referee for the comment. Some considerations regarding the high cost of materials have been added. Moreover, as mentioned in the conclusions section, future research will focus on using more cost-effective materials to improve the scalability of the production process. These aspects have been better clarified in the manuscript.

Authors should provide a short outlook with next steps (e.g., pilot-scale production, greenhouse/field trials).

Authors agree with the referee and future steps have been better stated at the end of the conclusion section (line 613-622).

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all my points, and the manuscript is in a better shape for acceptance.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made the necessary revisions. The paper can be accepted for publication in its current form.