Life Cycle Assessment of Ordinary Portland Cement Production in South Africa: Mid-Point and End-Point Approaches

Reviewer’s Comments

Author’s Responses

Reviewer One

1. This manuscript lacks innovation

The authors are grateful for the reviewer’s comment. The novelty of this current work has been highlighted in the literature review section (2.2. Overview and Gap in Knowledge) and Table 3.

… The aforementioned studies have provided useful insights on which this present study will be based. However, in contrast to previous work, this study adopts a holistic approach to life cycle impact evaluation by incorporating both midpoint and endpoint indicators using the ReCiPe methodology. This comprehensively assesses several damage categories, encompassing human health, ecosystems, and resources. In addition, sensitivity analysis is conducted to evaluate the reliability of outcomes in light of the uncertainty in modelling assumptions. Previous research lacked concurrent investigations into midpoint, endpoint models, and sensitivity analysis. Prior research on the cement sector in South Africa has primarily focused on midpoint analysis, with limited scope. This study provides novel insights into this geographical context by measuring the individual impacts and damages experienced...

… In contrast to other cement manufacturing LCA studies, the primary innovative elements of this research are incorporating a comprehensive damage assessment and sensitivity analysis to address the shortcomings identified in the existing literature. Additionally, the study projects the annual potential number of human lives and endangered species in South Africa, considering the country's cement demand and population. Furthermore, the monetary value of resource depletion is computed. The findings will give the South African cement industry a comprehensive insight into important environmental sustainability indicators and how they can be enhanced……

2. Comments on the Quality of English Language

The entire manuscript has been subjected to thorough review to improve the quality of communication.

3. Extensive editing of English language required

Extensive editing has been carried out to improve the sentence structure of the manuscript.

Reviewer’s Comments

Author’s Responses

Reviewer Two

1. line 18 In the abstract, it is unnecessary to mention which database and software were used in the paper.

The authors wish to thank the reviewer for this comment. In response to the comment, the database and software used in the manuscript have now been deleted from the abstract.

2. line 141 Chapter 3 contains discussed Results, so correcting the title to Results and Discussion is better.

The authors wish to thank the reviewer for this brilliant observation. In response to that, chapter three of the manuscript which originally read “RESULTS”, now reads “RESULTS AND DISCUSSION”.

3. Line 157 Pictures 2 and 8 are too small considering the issues they deal with (18 categories of impact) compared to, for example, pictures 11 or 12.

Figure 2 and 8 have been expanded for more clarity.

4. Line 158 Figure 2 shows the Mid-Point Impact Categories. It is not clear how the data shown in the image was obtained. In the chapter Methods, please explain how the data presented were obtained.

The data presented in the research paper were extracted from the Ecoinvent database. The methodology section under section 3.2 shows the data source.

… Secondary data from the ecoinvent database was used for this study. The Ecoinvent 3.6 database documentation of clinker production and Portland cement production in South Africa (ZA) (See Appendix 1 and 2). …

5. Line 226 The subtitles are not clearly marked. The text from line 226 onwards does not refer to point 3.1.5. Then, there are subheadings without labels that refer to Table 1 (Ozone formation, toxicity, global warming, fossil resource scarcity).

The authors wish to thank the reviewer for this observation. In response to that, chapter three of the manuscript which originally read “4.1. -4.1.5” leaving other subheadings without numbering, now reads “4.1-4.1.9”.

6. Line 231 Does number 30 in Tables 1,2 and 3 - Portland Cement [30] refer to data taken from reference 30?

Many thanks for pointing this out. Please note that the data was from Ecoinvent database and what we meant to include is {ZA} and not [30]. The {ZA} indicates that the data is for the South Africa context.

7. Line 303 Figure 6 is missing.

Thank you for the observation. Figure 6 has been added to the paper.

8. Line 314 In the chapter methods, better explain the data presented in the pictures. Is the data global, or is it for the SA area?

The data presented in the research paper were extracted from the Ecoinvent database. The methodology section under section 3.2 shows the data source.

… Secondary data from ecoinvent database was used for this study. The Ecoinvent 3.6 database documentation of clinker production and Portland cement production in South Africa (ZA) (See Appendix 1 and 2). …

9. Line 434 Appendix 3 is missing.

The authors are grateful for the comment. The tables (1,2 and 3) for uncertainty analyses were presented in in Appendix 3 in the supplementary material.

10. Line 467 It is recommended not to use references in the conclusion - only your conclusions and recommendations

The authors wish to thank the reviewer for this brilliant observation. In response to that, all references in the conclusion and recommendation sections have been deleted.

Reviewer’s Comments

Author’s Responses

Reviewer Three

1. The authors did not formulate the scientific problem well enough in the abstract. I would like to see a clear statement of the scientific deficit at the beginning of the abstract. This needs to be added.

The abstract has been enhanced by clearly stating the problem/rationale for the study as shown below:

…. Due to the growing demand for cement in the industry and limited studies in South Africa, it is essential to evaluate the environmental impact of cement production in South African context…

2. The "Introduction" section is not detailed enough. It does not fully reflect the current state of the issue. I would like to wish the authors to study a number of references in a little more detail, because nothing is clear about them based on the review and analysis. The literature review should be considered in more detail. It is who reveals to the reader a modern picture of the issue under study.

The authors are grateful for the constructive feedback. In order to strengthen the paper, a literature review section has been added covering the following:

2.1. Cement in the Sub-Saharan Africa (SSA) Region

2.2. Overview and Gap in Knowledge

3. Some images in Figure 1 are difficult to read. The authors should present the scheme, which is called " Material Flow Diagram for the Production of 1kg of Portland Cement", in a higher quality and more scientific form.

The authors thank the reviewer for the feedback. Figure 1 has been further enhanced for more clarity and the text in the figure is clear.

4. In the analysis of the RESULTS of this paper, the influence of each factor in the production of cement by two different methods is simply listed, and there is no detailed explanation and analysis.

The authors are grateful for the comment. The authors have added two sub-sections to the results and discussion section namely

4.4 Discussion of Results

4.5 Comparison with previous studies

5. Figure 6 is missing, please add it.

Thank you for the observation. Figure 6 has been added to the paper.

6. There are some errors in the diagram in this article, such as CO2 should be CO2, please correct such errors.

The authors are grateful for the comment. The CO2 in the paper has been corrected as suggested.

7. CONCLUSIONS, RECOMMENDATIONS AND FUTURE RESEARCH needs more in it, as it's more of an afterthought. The authors are suggested to highlight important findings and include afterthought of this work.

The authors appreciate the reviewer's comment on the conclusion section of the paper. The conclusion section of the paper has been further improved to include more information.

Reviewer’s Comments

Author’s Responses

Reviewer Four

1. Fig. 6 is missing;

Thank you for the observation. Figure 6 has been added to the paper.

2. the quality and standardization of drawings should be improved;

The authors appreciate the reviewer’s comment. The figures in the manuscript have been improved.

3. Fig. 7 was done correctly - all information has a line leading to the indicated area, other drawings with pie charts should be unified to the form in Fig. 7;

The authors are grateful for the suggestion. All the pie charts have been updated to include leader lines.

4. Fig. 8 - the reference to the -20% value is in the inscriptions, it should be corrected and the descriptions should be lowered;

Many thanks for the suggestion. The figure has been updated accordingly.