Towards a Circular Economy: Unlocking the Potentials of Cigarette Butt Recycling as a Resource for Seashore Paspalum Growth

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The abstract is informative, but the flow could be improved. Treatment codes (e.g., I25, F25) are not clearly explained, which may confuse readers. Additionally, the conclusion could be more concise and highlight the broader relevance of the findings. Reorganizing some sentences for clarity would enhance readability.

The introduction could better highlight what’s new in this study and why it matters. Emphasizing the scientific contribution more clearly would strengthen the overall impact.

Clarify number of replicates for all measurements

A brief explanation or citation supporting the choice of 25% and 50% inclusion rates would help readers understand the rationale behind these experimental levels.

The recovery phase is mentioned but not explained. It would be helpful to briefly clarify its purpose—was it included to assess potential delayed toxicity or the plants’ ability to recover from stress? A short rationale would improve the clarity of the experimental design.

Many values described in the text are already presented in the figures. You could streamline the text by highlighting only statistically significant differences or unexpected findings, rather than listing every result.

Instead of repeating "significantly different from Ctr" many times, vary the phrasing or use grouping statements (e.g., “Treatments A, B, and C showed significantly lower values than control and L1.”)

The Discussion offers a thorough interpretation of the results and contextualizes the findings well within the existing literature. However, the message could be strengthened by summarizing key insights more clearly—particularly which CB-derived materials proved most beneficial or problematic for turf performance. Grouping conclusions around practical implications (e.g., recommended uses, thresholds to avoid) would help highlight the study’s relevance and long-term applicability.

Author Response

The abstract is informative, but the flow could be improved. Treatment codes (e.g., I25, F25) are not clearly explained, which may confuse readers.

Reply: The abstract was re-written following the reviewer’s comments.

Additionally, the conclusion could be more concise and highlight the broader relevance of the findings. Reorganizing some sentences for clarity would enhance readability.

Reply: The item “Conclusions” was added in the revised version and was modified as suggested.

The introduction could better highlight what’s new in this study and why it matters. Emphasizing the scientific contribution more clearly would strengthen the overall impact.

Reply: The introduction in the revised version was modified as suggested.

Clarify number of replicates for all measurements.

Reply: The number of replicates are stated in M&M item 2.7.

A brief explanation or citation supporting the choice of 25% and 50% inclusion rates would help readers understand the rationale behind these experimental levels.

Reply: We apologize. The explanation was included in the M&M (item 2.2) of the revised version.

The recovery phase is mentioned but not explained. It would be helpful to briefly clarify its purpose—was it included to assess potential delayed toxicity or the plants’ ability to recover from stress? A short rationale would improve the clarity of the experimental design.

Reply: The requested explanation was added in M&M of the revised version.

Many values described in the text are already presented in the figures. You could streamline the text by highlighting only statistically significant differences or unexpected findings, rather than listing every result. Instead of repeating "significantly different from Ctr" many times, vary the phrasing or use grouping statements (e.g., “Treatments A, B, and C showed significantly lower values than control and L1.”)

Reply: We appreciate the reviewer’s suggestion. The text of Results was modified in the revised version.

The Discussion offers a thorough interpretation of the results and contextualizes the findings well within the existing literature. However, the message could be strengthened by summarizing key insights more clearly—particularly which CB-derived materials proved most beneficial or problematic for turf performance. Grouping conclusions around practical implications (e.g., recommended uses, thresholds to avoid) would help highlight the study’s relevance and long-term applicability.

Reply: Thank you for your comment. As mentioned above, a new section of “conclusions” was added following the reviewer’s suggestion.

Reviewer 2 Report

Comments and Suggestions for Authors

 

Comments on manuscript entitled: Towards a Circular Economy: Unlocking the Potentials of Cigarette Butts Recycling as Resources for Seashore Paspalum Growth.

The present study aimed to assess the use of cleaned cellulose acetate filters, solid debris and wastewater, mixed with soil for their applicability in the long‐term growth of Paspalum vaginatum under controlled conditions. Unmodified soil (control) and modified with intact CBs (I) were also tested in this study. In addition, physiological and biometrical parameters including chlorophyll fluorescence, photosynthetic pigments, surface coverage, shoot length, and aboveground biomass were evaluated under different treatments. The manuscript describes a good work. Authors need following points to be included before reconsideration.

- The abstract should focus on the novelty of your study.

- Voucher specimens should be deposited in a public herbarium or other public collections providing access to deposited material. Information on the voucher specimens and who identified them must be included in the Materials and methods section.

- You can add the properties of soil in the materials and methods section.

- There’s insufficient characterization of the recycled materials before use in soil.

- While the study explores CBs recycling, its real-world applicability is not fully demonstrated. Field experiments or real soil applications are lacking. Discuss.

- No measurement of ROS levels, or enzymatic antioxidants (catalase, peroxidase….etc.), which are central to claims about stress adaptation. Please clarify.

- Conclusions should be separated from discussion and must be revised to suit the major findings of the present study.

 

Author Response

Comments on manuscript entitled: Towards a Circular Economy: Unlocking the Potentials of Cigarette Butts Recycling as Resources for Seashore Paspalum Growth.

The present study aimed to assess the use of cleaned cellulose acetate filters, solid debris and wastewater, mixed with soil for their applicability in the long‐term growth of Paspalum vaginatum under controlled conditions. Unmodified soil (control) and modified with intact CBs (I) were also tested in this study. In addition, physiological and biometrical parameters including chlorophyll fluorescence, photosynthetic pigments, surface coverage, shoot length, and aboveground biomass were evaluated under different treatments. The manuscript describes a good work. Authors need following points to be included before reconsideration.

- The abstract should focus on the novelty of your study.

Reply: The abstract was re-written following the reviewer’s comments.

- Voucher specimens should be deposited in a public herbarium or other public collections providing access to deposited material. Information on the voucher specimens and who identified them must be included in the Materials and methods section.

Reply: In the present study Paspalum vaginatum Swartz cv. Sea Spray was used as it is a commercial cultivar commonly found in the market. The revised version contains more details about the vegetal material used in this study.

- You can add the properties of soil in the materials and methods section.

Reply: We apologize. The revised version contains more details about the soil used in the study.

- There’s insufficient characterization of the recycled materials before use in soil.

Reply: Thank you for your observation. The composition of the CB recycling byproducts has been detailed in a previous publication by Mariotti et al. (2022), which is now referenced in the revised version.

- While the study explores CBs recycling, its real-world applicability is not fully demonstrated. Field experiments or real soil applications are lacking. Discuss.

Reply: We appreciate the reviewer’s comment. We agree that field validation is essential to confirm real-world applicability. This study focused on controlled conditions as a first step to evaluate the applicability of CB recycling byproducts on turfgrass cultivation. We now addressed this important point in the Conclusions section and emphasizing the need for future research involving greenhouse and nursery-scale trials.

- No measurement of ROS levels, or enzymatic antioxidants (catalase, peroxidase….etc.), which are central to claims about stress adaptation. Please clarify.

Reply: Thank you for your comment. We recognize that ROS levels would provide valuable insights into turfgrass response to CB recycling byproducts. Although these measurements were not included in this study, we assessed photosynthetic performance (chlorophyll fluorescence, pigments) as a direct and sensitive indicator of stress adaptation. These metrics directly reflect plant energy production efficiency, serving as a key aspect for understanding physiological responses under abiotic/biotic stress conditions. Future research will undoubtedly benefit from exploring ROS as well as other traits to further elucidate how turfgrass adapts to these new growth conditions.

- Conclusions should be separated from discussion and must be revised to suit the major findings of the present study.

Reply: The item “Conclusions” was added in the revised version and was modified as suggested.

Reviewer 3 Report

Comments and Suggestions for Authors

MS No. sustainability-3724449

Title: Towards a Circular Economy: Unlocking the Potentials of Cigarette Butts Recycling as Resources for Seashore Paspalum Growth

Authors: Thais Huarancca Reyes et al.

 

 

The authors assessed the long term applicability of materials in cigarette butts (CB) recycling process including cleaned filters (F), solid debris (mainly paper and tobacco; R), and wastewater (L). for Paspalum vaginatum Swartz growth.

 

The topic is very interesting and the results seem to be useful in practice. The descriptions of the paper are clear. The quality of figures is ok at large.

 

However, the reviewer concerns the following aspects:

1. How about the composition of cleaned filters (F), solid debris (mainly paper and tobacco; R), and wastewater (L)? Is there any hazardous substance except for nicotine? For example, PAHs. How about their level? Could the recycling byproducts directly applied without further treatment?
2. The authors described a plenty of results. However, the mechanisms on inhibiting or enhancing plant growth are not so clear.
3. Although the authors mentioned “further research is needed to determine whether nicotine undergoes degradation in the applied system, clarify its effects on photosynthesis and hormone regulation, investigate the role of organosilanes in turfgrass metabolism, and assess their potential in mitigating CB‐derived chemical toxicity in turfgrass”, why was the situation for PAHs (if there is a high level) not concerned?
4. “especially wastewater at certain concentration, can sustainably promote turfgrass growth”, and “The wastewater (hereafter L) was cooled to 100 room temperature, divided into 50 mL tubes, frozen, and stored at ‐20 °C until use”, it seems not logical. In general, any waste water must be treated before its reuse.
5. “The experiment lasted 7 weeks”, in view of this, “However, long term studies are necessary to evaluate plant growth performance in this new substrate” is contradictory. The novelty is not clear.
6. The titles of figures are too lengthy.

The paper needs to be revised largely.

 

Author Response

How about the composition of cleaned filters (F), solid debris (mainly paper and tobacco; R), and wastewater (L)? Is there any hazardous substance except for nicotine? For example, PAHs. How about their level?

Reply: Thank you for your observation. The composition of the CB recycling byproducts has been detailed in a previous publication by Mariotti et al. (2022), which is now referenced in the revised version. The main compound in CB recycling is nicotine; however, other substances such as PAHs and BTEX are present in lower concentrations. In the revised version these chemical compounds were also mentioned.

Could the recycling byproducts directly applied without further treatment?

Reply: This is the central focus of our study: exploring the direct use of recycling byproducts without further treatment. Previous studies have highlighted that CB effects on plant physiology can be both positive and negative. Notably, research on turfgrasses is limited to just two species, which have also shown contrasting responses to CBs. By addressing this gap, our study not only addresses a critical environmental issue (i.e., CB waste) but also evaluates the sustainability and feasibility of CB recycling byproducts in horticultural applications, where ornamental plants, such as turfgrass, can be propagated and later be marketed for urban greening or gardening purposes.

The authors described a plenty of results. However, the mechanisms on inhibiting or enhancing plant growth are not so clear.

Reply: We appreciate the reviewer’s comment and understand the concern regarding the clarity of the mechanisms behind. However, we respectfully disagree with the concept that mechanisms were not addressed. In the Discussion, we included several physiological interpretations, such as dose-dependent responses to nicotine (potentially via hormesis), root hypoxia effects due to altered field capacity, oxidative stress evidenced by changes in chlorophyll content and antioxidant levels.

We recognize that a full mechanistic understanding goes beyond the scope of this study that aims to lay the groundwork for future studies exploring the underlying molecular mechanisms that mediate turfgrass adaptation to these novel growth conditions. We have now clarified this point in the revised Discussion and Conclusions, highlighting that this work opens new directions to investigating the reuse of CB recycling byproducts and plant’s adaptive responses in more detail.

Although the authors mentioned “further research is needed to determine whether nicotine undergoes degradation in the applied system, clarify its effects on photosynthesis and hormone regulation, investigate the role of organosilanes in turfgrass metabolism, and assess their potential in mitigating CB‐derived chemical toxicity in turfgrass”, why was the situation for PAHs (if there is a high level) not concerned?

Reply: Thank you for your observation. In the present study, we focused our physiological interpretations primarily on the most abundant and better-characterized compounds in L (i.e., nicotine and Si-based compounds). However, we fully agree that PAHs, although their low concentrations, are environmental contaminants of concern due to their persistence and potential toxicity. We mentioned them into the revised Discussion to explicitly recognize their presence and the need for further investigation into their possible role in affecting turfgrass metabolism and growth.

“especially wastewater at certain concentration, can sustainably promote turfgrass growth”, and “The wastewater (hereafter L) was cooled to 100 room temperature, divided into 50 mL tubes, frozen, and stored at ‐20 °C until use”, it seems not logical. In general, any waste water must be treated before its reuse.

Reply: We respectfully disagree with the reviewer’s assertion that wastewater must always be treated prior to reuse. Of course, this will depend on the intended application of the recycling water – for example, whether the plants grown using recycled water will be used for food or feed purposes, or on the specific wastewater type (ex: Wolcott S. et al. (2022). Suitability of select micro-green, ornamental and legume plants for use in green walls: a novel brewery wastewater treatment option. Environmental Technology, 44(18), 2679–2692. https://doi.org/10.1080/21622515.2022.2039782; Ahsan M. et al. (2022) Nutrients uptake and accumulation in plant parts of fragrant Rosa species irrigated with treated and untreated wastewater. Plants, 11, 1260. https://doi.org/10.3390/plants11091260). Here, our main goal was to evaluate the feasibility of using recycled byproducts, including wastewater, without additional treatment to determine whether this approach is viable. Our results indicated that wastewater can be effectively utilized when diluted appropriately, aligning with our hypothesis that direct application of these byproducts may be sustainable for turfgrass cultivation. This demonstrates the potential for direct reuse under controlled conditions, challenging conventional waste management practices and opening new possibilities.

“The experiment lasted 7 weeks”, in view of this, “However, long term studies are necessary to evaluate plant growth performance in this new substrate” is contradictory. The novelty is not clear.

Reply: Thank you for your comment. We modified the last sentences of the introduction in order to clarify the novelty of the study.

The titles of figures are too lengthy.

Reply: The titles of the figures have been shortened in the revised version.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors has responded the comments and revised the paper well at large.

The paper could be accepted.