Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Definition and allocation of shell‑related processes:
   Could you justify more explicitly why shell disposal‑related emissions and sinks (incineration, landfilling, weathering, recycling) are treated as part of the biological carbon footprint (BCF) rather than being integrated into the anthropogenic carbon footprint (ACF)? How would your key conclusions change if these processes were instead allocated to ACF as waste‑management emissions?

2. Uncertainty and sensitivity of shell fate parameters:
   Your conclusion that mussel aquaculture becomes a strong net sink at centennial and geological timescales depends critically on the assumed fractions for shell incineration, landfilling, recycling, and weathering. Could you provide a quantitative sensitivity analysis (e.g., scenario analysis or uncertainty ranges) showing how total CF changes with plausible variations in RIARIA and RweatheringRweathering for the Shengsi system?

3. Landfill behaviour and weathering timescales:
   How do you justify assigning a substantial fraction of shells to a “weathering” pathway within the landfill or open‑dump context, and over what timescale do you assume this weathering occurs? Are there empirical data from Chinese landfills or coastal dump sites to support the assumed rate and extent of CO22 uptake in these environments?

4. Representativeness of air–sea CO22 flux measurements:
   The farming‑stage BCF (+5.5 kg CO22-eq/t) is derived from field observations at 20 culture and 6 reference stations over one annual cycle. Could you elaborate on how spatial heterogeneity and interannual variability were accounted for when scaling these local measurements to the entire Shengsi farming area, and provide an uncertainty estimate (e.g., confidence interval) for BCFfarmingfarming?

5. Transferability of biodeposition and burial parameters:
   The biodeposition rate Cdepdep is taken from studies on Mytilus galloprovincialis and scaled to Shengsi, while burial efficiency is assumed at 5%. Could you discuss in more detail how species‑ and site‑specific differences (e.g., hydrodynamics, sediment type, organic matter content) might affect these parameters, and whether any local sediment data exist to support your chosen values?

6. Reconciliation with GWP100100 and time‑dependent BCF:
   In your multi‑temporal framework, ACF is calculated using standard GWP100100 factors, while BCF is evaluated over 100‑year and geological horizons in a mass‑balance sense. Could you clarify how these approaches are methodologically consistent, and whether there is any risk of mixing concepts of time‑integrated radiative forcing with mass‑balance over discrete time windows?

7. Scalability and generalization of results:
   To what extent can the Shengsi results be generalized to other major mussel or bivalve farming regions in China and worldwide? Which aspects of your findings (e.g., dominance of shell‑fate control, relative importance of distribution vs farming ACF) do you consider robust across systems, and which are highly context‑dependent?

8. Implications for carbon accounting and policy instruments:
   Given your conclusion that Shengsi mussel aquaculture can act as a net carbon sink under certain shell‑waste management regimes, how do you envision these findings being incorporated into formal carbon accounting frameworks or carbon‑credit schemes? What safeguards would be necessary to avoid over‑crediting, especially in light of uncertainties around long‑term shell weathering and burial?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. The manuscript proposes an interesting and genuinely innovative dual-carbon flow LCA framework. But the novelty of this approach only becomes fully clear after reading a substantial portion of the paper. The authors may wish to sharpen the early framing by more explicitly stating how this framework differs from conventional LCA studies that focus primarily on anthropogenic emissions or treat biogenic carbon in a simplified way.

2. The sections describing the biological carbon footprint across different time horizons are scientifically sound but at times difficult to follow due to dense language and long sentences. Add some streamlining of phrasing and clearer signposting and it would significantly improve readability.

3. Several parameters used in the biological carbon footprint calculations, such as burial efficiency and shell disposal pathways, have a strong influence on the results. While conservative assumptions are stated, the discussion would benefit from a clearer reflection on uncertainty or sensitivity. Even a brief qualitative discussion of how alternative assumptions might affect the results..

4. The inclusion of post-consumption shell fate is one of the most original aspects of the study, but it also raises questions about system responsibility. Clarifying whether shell disposal is treated as a producer responsibility, a societal responsibility, or a shared boundary assumption would highly improve conceptual transparency and help readers interpret results.

5. Article generally avoids overstatement, the presentation of long-term carbon sink potentials could still be misunderstood as directly comparable to short-term mitigation measures. The conclusions would be strengthened by more clearly distinguishing between long-term accounting-based sink potential and emissions reductions that are relevant for near-term climate policy.

Comments on the Quality of English Language

The manuscript is written in clear and professional English, and the overall language quality is suitable for publication. However, some sections - particularly those describing the biological carbon processes - are quite dense and rely on long   complex sentences. A light language edit aimed at improving sentence clarity and flow would make the manuscript easier to read and help the key ideas stand out more clearly.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

check spelling, language and grammar ("This study proposes a dual-carbon flow LCA framework integrates the...", including use of blanks)

if shells are incinerated, what happens to the calcium carbonate from the shells. How is this part dealt with in the analysis?

I understand the measurements done. Where the results crosschecked with material balances (e. g. of the weight accumulated in meat and shells) 

Was the potential exchange of the water body in the farm with the environment, like seasonal currents, whether, temperature analysed?

can you provide for clarity a similar figure like figure 6 for the biological carbon footprint

Can you provide an interpretation of table 5 comparing your results to the ones from the references

Regarding literature: can you highlight in a dedicated paragraph how the sequestration of CO2 in shells is dealt with in other LCAs (e. g. in Italy, in the US, etc.)

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I would like to congratulate the authors on their revised manuscript. The paper has significantly improved after the revisions and now represents a high-quality and well-prepared publication.