Impact of Carbon Intensity Indicator on the Vessels’ Operation and Analysis of Onboard Operational Measures
Round 1
Reviewer 1 Report
The study shows the need for the cooperation between the vessel operators and charters to improve the efficiency of the vessel operation by the measure of CII. I believe that it is a relevant claim that the holistic approach is required to achieve a significant improvement in reduction of carbon footprint of shipping. However, the presentation of the backing case studies should be improved to make the claim more credible. There are mainly three points to improve in the article to be acknowledged as a sound scientific work.
1. The source of data for the benchmark analysis should be clearly specified. It is understandable not to specify the source directly due to confidentiality. However, the authors still could describe how the data are collected, what are the sampling rate, what kind of signals or information are used for the analysis, or how the data are pre-processed before they are used in the analysis, if any.
2. It will be great to include the description of assumptions and simplifications used for the calculation, if any. If possible, the process of the calculation could be presented with such assumptions and simplification.
3. It is not clear how the improvements of CIIs are considered and calculated. If the authors used a model-based approach, description of the models and the assumptions should be included. It will be also great to discuss the limitation and the validity of the model with the results.
Author Response
Thank you for your review,
herebelow are our replies to your comments
1.
Data collection
Master students from both Naval Academy and Costanta Maritime University were asked to collect the data from the ships they were doing the
cadetship training on.on. All data was copied from engine room log book with master and chief engineer approval. The data are collected from the
engine room log book Tthere after the data was checked for consistency by their course supervisor and out 30 students collecting data from 23
students were found suitable for our study. The 23 thereafter they were split in 4 categoriesresults weter thereafter grouped in 4 categories:
Container carriers ( 4 ), Bulk carriers ( 12), tankers (7) and LNG carriers (2). The results related to LNG carriers were considered not
representative and they were not selected for our study, while for the other three categories one cointar ship, 2 bulk carriers and 1 tanker ship
were randomly selected..
2. The data was collected for a number of complete voyages, average speed, average waiting time, average consumptions were calculated and
thereafter the averages were used for one-year calculations although the voyages were not completing exactly at the end of the year. The ship
was considered to repeat those voyages for one year.
3. The improvements were calculated using reverse calculations having in view that the target is that the vessels should always be with A, B or C
rating. For some of the scenarios to obtain C was almost impossible from practical point of view as apart from environmental consideration the
owners will always tend to focus on profit maximisation. For different type of ships, different type of solutions were applied. For container ships
reduction if waiting time can be translated into lower speed and that requires better planning with agents to avoid waiting time. For bulk carriers
and tankers on the other hand waiting time at anchorage is many times dependent of vessels arrival as many terminals use the first come, first
served principle and therefore the foxus was on reducing speed at sea and Eco speed and super eco speed were used as improvements
scenario.
Reviewer 2 Report
New CII (Carbon Intensity Indicator) is an operational measure part of SEEMP III and came into force on 1st January 2023. In the present work, the authors analyzed the one-year calendar routes of four vessels (one container carrier, two bulk carriers, and one tanker vessel). At last, they give one interesting conclusion that CII is highly dependent on idle and laden voyages and very good cooperation between shipowners and charterers. Overall, it is a nice work and is possible to be published on Sustainability (ISSN 2071-1050). Kind regards,
Author Response
Thank you very much for your positive feedback.
Reviewer 3 Report
Dear Authors,
I read your paper and from my point of view it can be published as it is. Your paper is well written and it contains all necessary chapters i.e.: introduction, literature review, methodology, results, conclusions and references. The literature review could be extended. It is also not clear how the vessels where selected for your case studies. Also, it is not clear how data visible in eq. 3 were obtained (line 177)? Please, could you explain both these issues in the research methodology (chapter 3).
Your sincerely,
Reviewer
Author Response
Dear reviewer,
Thank you very much for your comments. Herebelow is our reply to your querries
1.
Data collection
Master students from both Naval Academy and Constanta Maritime University were asked to collect the data from the ships they were doing the cadetship training on. All data was copied from the engine room log book with master and chief engineer approval. Thereafter the data were checked for consistency by the course supervisor and out of 30 students collecting data from 23 students were found suitable for our study. The 23 results were thereafter grouped into 4 categories: Container carriers (4). Bulk carriers (12), tankers (7), and LNG (2). The results related to LNG carriers were considered not representative and they were not selected for our study, while for the other three categories, one containership, 2 bulk carriers, and 1 tanker vessel were randomly selected.
2. a and c are parameters estimated through median regression fits, taking the attained CII and the Capacity of individual ships collected through IMO DCS in year 2019 as the sample.
Round 2
Reviewer 1 Report
The paper has been improved with respect to clarity of the source of the data and explaining the method. However, it is still not very transparent how what the nature of the data is and how it is processed. For example, the authors mentioned that the data were copied from the log book, but doesn't tell which information (fuel tank level, average of fuel consumption rate, etc) from the log book the authors took. In addition, period that the data cover is an important information to judge if the data are representative or not and should be presented.
For the method to estimate the improve in CII, the authors mentions that they took the reverse calculation approach but it is still challenging to understand the method. Assuming that the approach assumes that the CII goal is achieved for some vessels or not for other vessels, it does not support the conclusion very well as the conclusion is not supported by the data or models but by assumptions.
Author Response
Thank you very much for your feedback and sorry for delay. Herebelow is our reply
1. The text has been ammended as follows "Master students from both Naval Academy and Constanta Maritime University were asked to collect the data from the ships they were doing the cadetship training on. All data was copied from the engine room logbooks with master and chief engineer approval. The data collected included: number of hours sailing in a day (sometimes clock was changed, and it was either 23 or 25 hours depending on if the vessels were heading west or east), fuel oil consumption and distance travelled. When the ships were at anchorage or drifting the only of course there was no speed to record, but also diesel oil consumption was recorded. The data was collected during various periods during October 2020 – December 2021."
2. The methodology used is as follows
The target of all ship owners is to always maintain the vessels withing A, B, C ratings and since our initial calculations showed that this can be a challenge the following methodology was used to reach at least rating C.
- What is the average fuel consumption to reach minimum C rating?
2. Is the reduction of speed at sea sufficient to reach that level? For this option full speed, eco speed and super eco speed alternatives were calculated. - if the answer is NO , with the best speed calculated as per point two, what reduction is waiting time or drifting time is required to reach the minimum C rating?
Round 3
Reviewer 1 Report
Dear authors,
Thanks you for the clarification. However, it still misses the explanation of methodology for calculating the fuel consumption for the reduced speed. What kind of formula or model did you use to calculate the fuel consumption with reduced speed? Maybe it will be great to have an illustrative example for such a calculation.
Author Response
Good day, we have included an illustrative example. Hope this clarify the methodology.
