Integrated Carbonate-Based CO2 Capture—Biofixation through Cyanobacteria
, Biagio Anderlini 1, Veronica D’Eusanio 1, Andrea Luca Russo 4 and Luca Forti 5
Eric Lawrence Singsaas
Round 1
Reviewer 1 Report
This work aims to optimize growth conditions for two species of ˆSpirulinaˆ in a prototype photobioreactor. Algal carbon capture promises to help sequester industrial CO2 emissions to address anthropogenic emissions that threaten our stable climate. Despite the importance of this work, numerous things need to be improved in the presentation and organization of this paper. Ranging from the format of figures and tables to rewriting the introduction to illustrate the scientific/engineering problem being addressed.
More fundamentally, I recommend that the authors consider their photobioreactor's design before attempting to optimize culture conditions. Many designs – in literature and commercially available – already address light and CO2 delivery to the cells. These factors are well-known and can be addressed through reactor engineering before any system optimization occurs. The authors would do well to review the impact of reactor design on algal carbon capture.
The introduction should be shorter. Reviewing generic carbon capture system approaches and photosynthesis is unnecessary in this case. Instead, discuss the limitations in knowledge relevant to the techno economics of algal carbon capture.
Please keep it to the essential information necessary to set up your questions. Then, briefly enumerate your research questions, hypothesis, or objectives at the end.
The methods state that the PPFD was measured, but no details are given on the instrumentation, the placement of the sensor, and what sensor was used. Was the instrument made for measuring PPFD in water or air? Was it filtered/attenuated for land plants or algae? More importantly, how even was the PPFD across and within the culture tubes? Algal cultures of OD > 0.5 attenuate greater than 90% of the incident light. Considering the depth of the tubes, how much of that light is reaching the cells in the middle or far side of the culture?
Figure legends need to be more explanatory; they should briefly describe the figure's key components, focusing on what's essential to understanding the figure without unnecessary details. Explain symbols, colors, lines, and any relevant labels. Keep it concise but informative.
The text in figures 6-8 needs to be bigger to be legible.
Rubisco is the IUPAC name of the enzyme. The unusual capitalization is not necessary.
Please explain the significance of Pareto charts. Is Figure 6 necessary? The statistical analysis could be described in the text without referring to a figure.
The English usage is acceptable.
Author Response
Please, see the attached PDF file
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript proposes an innovative approach to address the pressing issue of CO2 emissions by integrating carbonate-based CO2 capture with biofixation using cyanobacteria. The research focuses on assessing the potential of two Spirulina strains to directly utilize sodium bicarbonate as a carbon source. Through a Design of Experiments approach, the study optimizes parameters like light irradiation, temperature, and bicarbonate concentration. The achieved biomass productivity of 880 mg/L∙d and CO2 utilization efficiency of 58 mol% are good outcomes. However, the manuscript lacks a thorough discussion of potential challenges or limitations associated with the proposed integrated approach. Additionally, while mentioning the suitability of Spirulina strains for "broad industrial applications," the manuscript does not delve into the specifics that make these strains suitable for large-scale industrial implementation. To strengthen the paper, addressing these points through major revisions is recommended.
Major Revision:
The paper's potential impact could be significantly enhanced by addressing two major points.
1- Firstly, a section discussing potential challenges and limitations of the integrated approach is essential. Providing insight into practical constraints will better contextualize the proposed solution and guide future research directions as reported in the recent literature of a) “Understanding the interaction between active sites and sorbents during the integrated carbon capture and utilization process” and b) “Integrated carbon capture and utilization: Synergistic catalysis between highly dispersed Ni clusters and ceria oxygen vacancies”.
2- Secondly, the suitability of Spirulina strains for industrial applications needs to be elaborated. Exploring aspects like scalability, ease of cultivation, economic viability, and any potential bottlenecks will provide a clearer understanding of the feasibility of large-scale implementation. Addressing these aspects will not only strengthen the paper's practical implications but also improve its overall quality and potential for broader impact.
3- The manuscript would benefit from a section dedicated to discussing the limitations of the study. Identifying potential limitations and addressing them would strengthen the credibility and reliability of the research. Additionally, it would be helpful to suggest potential directions for future research based on the findings and limitations identified.
The paper presents a promising approach to tackle CO2 emissions by integrating carbonate-based CO2 capture with cyanobacteria biofixation. The study's emphasis on process optimization and impressive results are commendable. However, the manuscript should be revised to include discussions on challenges and limitations, as well as detailed insights into the industrial suitability of Spirulina strains. These revisions are crucial to enhancing the paper's significance and relevance.
The English require minor revision
Author Response
Please, see the attached PDF file
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The manuscript can be accepted now in its present form.
The manuscript can be accepted now in its present form.
