Review of the manuscript “Potential environmental impact of bromoform from Aspargopsis farming in Australia” by Jia et al., ACPD, 2021.

The paper presents modeling experiment to evaluate how one of the proposed feeding management alternatives to reduce CH4 emissions from ruminant livestock (i.e., Aspargopsis farming) could impact on the stratospheric ozone layer due to the by-product formation of bromoform (CHBr3). This species is a very short-lived species (VSLS) with a mean lifetime of 17 days in the atmosphere, and consequently, the CHBr3 impact on stratospheric ozone depends on the superposition of source strength and location with the efficiency of convective transport. The paper propose a multiple set of realistic local and global scenarios, as well as the occurrence of some improbable extreme episodes affecting the Australian coast, to evaluate a representative range of the overall ozone depletion potential (ODP) of bromoform emissions from oceanic and terrestrial cultivation approaches, and compare them with the impact of coastal natural bromoform emissions. The work is very well-planed and provides a realistic and clear evaluation of the magnitude of one of the environmental consequences of promoting Aspargopsis production in Australia, and determine that even in the worse possible scenario, the negative impact of the additional farming-released bromoform are very small in comparison with the natural contribution from the ocean. The methodology and results are generally well presented, although some clarification is required as described below. I suggest the paper is accepted for publication after the following issues have been solved:

paper propose a multiple set of realistic local and global scenarios, as well as the occurrence of some improbable extreme episodes affecting the Australian coast, to evaluate a representative range of the overall ozone depletion potential (ODP) of bromoform emissions from oceanic and terrestrial cultivation approaches, and compare them with the impact of coastal natural bromoform emissions. The work is very well-planed and provides a realistic and clear evaluation of the magnitude of one of the environmental consequences of promoting Aspargopsis production in Australia, and determine that even in the worse possible scenario, the negative impact of the additional farming-released bromoform are very small in comparison with the natural contribution from the ocean. The methodology and results are generally well presented, although some clarification is required as described below. I suggest the paper is accepted for publication after the following issues have been solved: Main Comments:

1a. Ozone Depleting Potentials (ODPs): Concept and Implications
Section 2.5 briefly describes the ODP concept and how it has been adapted to evaluate the ODP impact of VSLS due to their variable distribution in the troposphere. However, given the importance of the ODP fields used to determine the bromoform ODP-weighted emissions presented in this work, I found that more details (and results discussion in Section 4) should be given. In particular, the authors based their analysis on the ODP spatiotemporal study performed by (Pisso et al., 2010) using the same FLEXPART model, but no mention is provided about other approaches to determine the Stratospheric ODP (SODP) for long-lived species that are know to affect both tropospheric and stratospheric ozone (Claxton et al., 2019;Zhang et al., 2020), and why it is important to distinguish the tropospheric and stratospheric ozone impacts of CHBr3.
Page 15, Lines 326-329 is the only place in the text where I found explicit mention that the product gas contribution of VSLS degradation is not being considered, which is reasonable as the proposed methodology considers only the exponential decay of the emitted source gases.
However, this should be at least highlighted again in the conclusions and if possible, an estimation of the magnitude of the neglected tropospheric impact of VSLS product gases and/or how the modeling ozone changes depend on the treatment of VSLS product gases (i.e., Fernandez et al., 2021) could be given.

1b. Ozone Depleting Potentials (ODPs): Methodology
The ODP for bromoform is computed by comparing the ozone destruction of CHBr3 compared with the ozone destruction produced by an equivalent mass of CFC-11. However, no CFC-11 sensitivity is mentioned to have been performed for this study. Thus, it is not clear if Fig. 7 is a direct result of the modeling simulations performed in this work, or it is taken from Pisso et al., (2010). If the later is the case (which I believe it is), then, this should be expressed more clearly in the text and proper reference to this study should be given in the caption of Fig. 7. Page 14, Lines 311-313 explicit says that "ODPs for VSLSs are calculated by means of combining two sources of information: one corresponding to the slow stratospheric branch and the other to the fast tropospheric branch of transport". First, how the tropopause location is determined in the study? Second, is it possible to quantify the contribution of these two branches, and could this be taken as an approximation of the tropospheric and stratospheric influence of CHBr3 farming emissions? Note that one of the main results of the paper is that ODP-weigthed CHBr3 contribution from Aspargopsis farming would be, at most, less than 1% of the natural CHBr3 value (i.e., the Ziska_Coast scenario); thus properly showing how the ODP values were computed for this particular VSLS should be clear.

Minor Comments:
GENERAL: The number of significant digits used when reporting numbers should be revised throughout the hole text.
P2,L36: What do you mean by "the remains are relatively small"? P2,L37: "less than 0.016%" … is this significant different to less than 0.02%? P2,L39: "by 0.48%" … of its initial value, or up to 0.48%? P4,L88: "In consequence, the environmental impact of CHBr3 … needs to be explored and elucidated". As detailed in the main comment, the authors should explicit mention that VSLS influence both the troposphere and stratosphere, and that here only the stratospheric impact is considered.
P4,L94: I found the paper very informative not only to industry, but also to policy makers and the scientific community. P5,L119: 3.4674 x 10⁴. Does this number have 5 significant digits? Please clarify and make it consistent throughout the text. P5,L128-130: How did you get the 30 times scaling factor to extrapolate from Australian Aspargopsis production to Global production? And how did you get the 1 Tg DW value? (I could not get that value by multiplying the informed data … I must have missed something).  Table 1 it is evident that the study was performed for meteorological conditions of year 2018 … But I could not find where in the text this is described (I might have missed it). P11,L263 and Table 1: The total CHBr3 emission within the background scenario considers the well-established Ziska emission inventory, and is mentioned to consider "all 1ºx1º grid cells directly neighboring the coastline", which accounts for 3109 Mg (Table 1)    P3,L64: rephrase "showed the most potential for CH4 production decrease". P9,L189: What do you mean by "as the farming aims at high yielding CHBr3 varieties"? P10,L214: "the gradient is between" … it is computed between? It is computed considering …?