A methodology to constrain carbon dioxide emissions from coal-fired power plants using satellite observations of co-emitted nitrogen dioxide

Liu, Fei; Duncan, Bryan N.; Krotkov, Nickolay A.; Lamsal, Lok N.; Beirle, Steffen; Griffin, Debora; McLinden, Chris A.; Goldberg, Daniel L.; Lu, Zifeng

doi:https://doi.org/10.5194/acp-20-99-2020

Articles | Volume 20, issue 1

https://doi.org/10.5194/acp-20-99-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-20-99-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 1

Research article

|

03 Jan 2020

Research article |

| 03 Jan 2020

A methodology to constrain carbon dioxide emissions from coal-fired power plants using satellite observations of co-emitted nitrogen dioxide

Fei Liu, Bryan N. Duncan, Nickolay A. Krotkov, Lok N. Lamsal, Steffen Beirle, Debora Griffin, Chris A. McLinden, Daniel L. Goldberg, and Zifeng Lu

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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'referee comment', Anonymous Referee #2, 05 Aug 2019
- AC1: 'response for Referee #2', Fei Liu, 29 Oct 2019
RC2: 'Review to the manuscript by Liu et al. “A methodology to constrain carbon dioxide emissions from coal-fired power plants using satellite observations of co-emitted nitrogen dioxide”', Anonymous Referee #1, 06 Aug 2019
- AC2: 'response for Referee #1', Fei Liu, 29 Oct 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Fei Liu on behalf of the Authors (29 Oct 2019) Manuscript

ED: Referee Nomination & Report Request started (01 Nov 2019) by Aijun Ding

RR by Anonymous Referee #2 (16 Nov 2019)

Suggestions for revision or reasons for rejection

Liu et al. carefully addressed my comments. Even though I’m still not convinced that the US CEMS based estimates of the NOx/CO2 ratio is always a better alternative to similar estimates available from bottom-up emission inventories (such as, e.g., EDGAR or GPED), I find that the manuscript is much improved and that its revised version allows a reader to get a better understanding of the advantages and limitations of the proposed method. I also find that the analysis of the factors determining the NOx/CO2 emission ratios for coal-fired power plants is sufficiently useful and novel to warrant publication of this paper. However, I still see a few minor issues that need to be addressed before the paper can be accepted for the final publication.

1. Figure 1 is first mentioned at the beginning of the Sect. 2.1 as showing the locations of the power plants, but it also presents emission estimates which are first discussed only at the very end of this section. I recommend therefore that Figure 1 is revised. Along with the location of the power plants, it might provide some other introductory information, such as e.g. NOx and CO emissions or NOx/CO2 emission ratio according to CEMS, but the derived emission estimates should be presented in a separate figure and discussed in Sect. 3.

2. P.4, l. 3, “The locations of the 8 plants are shown in Figure 1 and given in Table S1 ”: Actually, Table S1 provides the coordinates of 21 power plants, and it is not at all clear which of them are the “8 plants”.

3. P. 4, l. 15: I suggest mentioning here that the uncertainty of the NOx/NO2 ratio is discussed below in Sect. 3.2. Also, I guess the authors meant the NOx/NO2 ratio rather than the NO/NO2 ratio.

4. Figure 7b is not mentioned anywhere in the text, although the results shown in this figure are discussed in the second paragraph of Sect. 3.1.

5. P. 7, l. 36 and Table S2: The authors indicate the uncertainty of the plant-specific CEMS measurements (which is assumed to be within 15%) as one of the sources of the overall uncertainty of the CO2 emission estimates. Should not instead the uncertainty of the ratio_CEMS_regressed (which is much larger) be taken into account in this analysis?

6. Sect. 3.3.1. I appreciate the extended discussion of the feasibility of applying the proposed method outside the US, but I do not see any solid arguments that using the ratio_CEMS_regressed in the case of “less strict” countries is indeed a better choice than using the available GPED data. If the authors cannot provide such arguments, I suggest that they should at least make it clear that using the NOx/CO2 emission ratios based on the GPED data is an equally reliable alternative.

7. P. 9, l. 22-25. The sentence is confusing: many details are required for what?

8. P.11, Data availability: The authors indicate the source of the satellite data but I believe they should also inform a reader about the availability of the CEMS and GPED data used in their analysis.

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RR by Anonymous Referee #1 (18 Nov 2019)

ED: Publish as is (25 Nov 2019) by Aijun Ding

AR by Fei Liu on behalf of the Authors (26 Nov 2019) Manuscript

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Short summary

We present a novel method to infer CO₂ emissions from individual power plants, based on satellite observations of co-emitted NO₂. We find that the CO₂ emissions estimated by our satellite-based method during 2005–2017 are in reasonable agreement with the CEMS measurements for US power plants. The broader implication of our methodology is that it has the potential to provide an additional constraint on CO₂ emissions from power plants in regions of the world without reliable emissions accounting.