Impact of Biofuel on the Environmental and Economic Performance of Marine Diesel Engines

Round 1

Reviewer 1 Report

In this manuscript, the Authors experimentally assessed the potential of the biofuel adoption on the fuel consumption and emissions of a marine diesel engine, developed by Yanmar. Different fuel mixture have been adopted, considering different percentages of biofuel.

The paper can be considered suitable for publication after major revision addressing the following comments.

General comments

0.1 The main weakness of the presented work is that it lacks of scientific sound. Some results are presented but they are not scientifically justified and explained.

0.2 The innovative contribution to the available literature and the research gap are not clearly defined in the manuscript.

Specific comments

1. Introduction

1.1 (pag. 1 – line 28) – the introduction session must be shortened and it can be linked in a smoother way with the consequent paragraph 2.

2. Literature review

2.1 (pag. 3 – line 106) – the different fuels and the relative characteristics, can be highlighted in a single table at the beginning of the paragraph.

2.2 Other works can be found in literature considering also different fuels (HVO, e-fuels, …). This can be added in the introduction. In addition, as correctly pointed out in the paragraph 3 by the Authors, the toxicity of these fuels compared to the conventional ones should be taken into account. Regarding this topic, the following citations can be useful:

- Jalava P, Aakko-Saksa P, Murtonen T, Happo M, et al. Toxicological properties of emission particles from heavy duty engines powered by conventional and bio-based diesel fuels and compressed natural gas. Part Fibre Toxicol 2012;9:1–14. https://doi.org/10.1186/1743-8977-9-37.

- Millo F, Vlachos T, Piano A, Physicochemical and mutagenic analysis of particulate matter emissions from an automotive diesel engine fuelled with fossil and biofuel blends, Fuel, Volume 285, 2021, 119092, https://doi.org/10.1016/j.fuel.2020.119092.

- Kowalska M, Wegierek-Ciuk A, Brzoska K, Wojewodzka M, et al. Genotoxic potential of diesel exhaust particles from the combustion of first- and second-generation biodiesel fuels—the FuelHealth project. Environ Sci Pollut Res 2017;24:24223–34. https://doi.org/10.1007/s11356-017-9995-0.

3. Material and methods

3.1 Figure 1, please add a reference in the caption if this picture has not been provided by the Authors

3.2 (pag. 5 – line 235) – a table with the characteristics biofuel, RMA10 can be useful to better compare the different fuels.

3.3 (pag. 6 – line 251) – as highlighted, a table with the engine feature can be more effective

3.4 (pag. 6 – line 262), figure 2 is not a “flowchart”

3.5 (pag. 7 – line 311) – Equation 2 is useless. Please remember that this could be a scientific article.

3.6 (pag. 7 – line 317) – what is the meaning of ‘diesel power’? is it just a power?

4. Results

4.1 Table 1, interesting results, however there is not any explanation.

4.2 Figure 3 is not so effective. Please, add a legend, and think about a different way to show the results, even using just lines can be better

4.3 (page 10 – line 399) – which is the reasons behind the modification of the reference (i.e., denominator) between emissions and brake specific fuel consumption in Equation 4?

4.4 Figure 4 is not effective again. In addition, this is just the percentage difference of the results already highlighted in Figure 3. This, it can be avoided.

4.5 Figure 5 must be improved. Colors are not consisted with the other figures, legend is missing. This figure, and the whole Results section must be improved with a more technical sound.

5. Discussion

5.1 In my point of view, this paragraph is useless at this point of the manuscript, where a scientific explanation of the results mu be inserted. This is a scientific paper and not only the evidences from experiments should be added, but also their explanations, and the reasons behind the behaviors highlighted.

6. Conclusions

6.1 Please, reduce the length of this section. Conclusions should be concise, highlighting the framework, the aim and the main results achieved.

Author Response

For reviewer 1.

1.1 (pag. 1 – line 28) – the introduction session must be shortened and it can be linked in a smoother way with the consequent paragraph 2.

In the introduction section, we wanted to show the relevance of the topic and possible ways to solve it. We are ready to shorten lines 70-81 and 95-100.

2.1 (pag. 3 – line 106) – the different fuels and the relative characteristics, can be highlighted in a single table at the beginning of the paragraph.

We are ready to add the following phrase

“Characteristics of alternative fuels are given in table 1”

and table

Table 1. Some characteristics of alternative fuels

2.2 Other works can be found in literature considering also different fuels (HVO, e-fuels, …). This can be added in the introduction. In addition, as correctly pointed out in the paragraph 3 by the Authors, the toxicity of these fuels compared to the conventional ones should be taken into account. Regarding this topic, the following citations can be useful:

Thanks for the recommendations, we are changing the References and adding these articles as 38, 39, 40

38. Jalava, P; Aakko-Saksa, P; Murtonen, T; Happo, M. et al. Toxicological properties of emission particles from heavy duty engines powered by conventional and bio-based diesel fuels and compressed natural gas. Part Fibre Toxicol. 2012, 9, 1–14. https://doi.org/10.1186/1743-8977-9-37.
39. Millo, F; Vlachos, T; Piano, A. Physicochemical and mutagenic analysis of particulate matter emissions from an automotive diesel engine fuelled with fossil and biofuel blends. Fuel. 2021, 285, 119092, https://doi.org/10.1016/j.fuel.2020.119092.
40. Kowalska, M; Wegierek-Ciuk, A; Brzoska, K; Wojewodzka, M. et al. Genotoxic potential of diesel exhaust particles from the combustion of first- and second-generation biodiesel fuels – the Fuel Health project. Environ Sci Pollut Res. 2017, 24, 24223–34. https://doi.org/10.1007/s11356-017-9995-0.

3.1 Figure 1, please add a reference in the caption if this picture has not been provided by the Authors

The Figure 1 was created by us taking into account the recommendations of Annex VI MARPOL. We added references to the title of the Figure 1

Figure 1. Requirements Annex VI MARPOL to quantity NOX in the exhaust gases of marine diesel engines [36, 60]

3.2 (pag. 5 – line 235) – a table with the characteristics biofuel, RMA10 can be useful to better compare the different fuels.

According to your recommendations, we change the lines 233–245.

This research used biofuel FAME as an alternative fuel and RMA10 fuel as basic diesel ful. Fuel characteristics are given in Table 2.

Table 2. Some characteristics of biofuel FAME and RMA10 fuel

3.3 (pag. 6 – line 251) – as highlighted, a table with the engine feature can be more effective.

According to your recommendations, we change the lines 250–256.

The research was carried out on marine medium-speed diesel engines 6N165LW Yanmar with the following characteristics (Table 3).

Table 3. Mane characteristics of diesel engines 6N165LW Yanmar

3.4 (pag. 6 – line 262), figure 2 is not a “flowchart”

We correct as

Figure 2. Fragment of the fuel feed system of marine diesel engines 6N165LW Yanmar

and line 262–263 as

A fragment of the diesel fuel feed system is shown in Fig. 2.

3.5 (pag. 7 – line 311) – Equation 2 is useless. Please remember that this could be a scientific article.

Equation 2 shows how we performed the calculation hourly fuel consumption in the research. This parameter can be defined in various ways.

3.6 (pag. 7 – line 317) – what is the meaning of ‘diesel power’? is it just a power?

We correct as

power of the diesel in different modes of operation , kW.

4.1 Table 1, interesting results, however there is not any explanation.

We have provided short explanations on the lines 364-366 as well as on the figures after the table.

4.2 Figure 3 is not so effective. Please, add a legend, and think about a different way to show the results, even using just lines can be better

Figure 3 show the relative changes in parameters. Figure 3 allow you to visually determine the best composition of the fuel blend and the best mode of operation of the diesel engine.

4.3 (page 10 – line 399) – which is the reasons behind the modification of the reference (i.e., denominator) between emissions and brake specific fuel consumption in Equation 4?

Equation 4 allows you to determine the relative change in performance. This allows you to evaluate which mixture and which mode is more effective.

4.4 Figure 4 is not effective again. In addition, this is just the percentage difference of the results already highlighted in Figure 3. This, it can be avoided.

Figure 3 allow you to visually determine the best composition of the fuel blend and the best mode of operation of the diesel engine. We believe this is more convenient than determining these values from a table.

4.5 Figure 5 must be improved. Colors are not consisted with the other figures, legend is missing. This figure, and the whole Results section must be improved with a more technical sound.

The colors in Figure 5 do not have to match the colors in Figures 3 and 4. Figure 5 corresponds to the optimal composition of the fuel mixture for a load range of 50–80%.

5.1 In my point of view, this paragraph is useless at this point of the manuscript, where a scientific explanation of the results mu be inserted. This is a scientific paper and not only the evidences from experiments should be added, but also their explanations, and the reasons behind the behaviors highlighted.

In this paragraph, we have highlighted our thoughts for research.

6.1 Please, reduce the length of this section. Conclusions should be concise, highlighting the framework, the aim and the main results achieved.

We are ready to shorten lines 483-495.

Author Response File: Author Response.pdf

Reviewer 2 Report

The group of authors measured fuel consumption, emissions and power on diesel engines fueled by blends of marine diesel RMA10 and FAME biodiesel with various ratios. They concluded on the best ratio with respect to engine fuel efficiency and with respect to lowest pollutant emissions.

The experimental setup is well described but there is given too much introduction and context, in the way that distracts from the focus of the experiment.

The introduction is too wide. It explains about all problems of other energy sources and carriers, should be shortened. Lines 55-57 does not stand, there are some very large cruising ships powered by methane (MS Iona).

Line 69: emissions of carbon oxide...it is imprecise. Is it monoxyde or dioxide that is limited?

Line 88: unclear sentence, private nature?

Lines 106 ...118, out of subject, describing properties of natural gas?

Further describes use of hydrogen, shortcomings of methanol...In my opinion it misses the subject. If it would be an alternative fuel revision, it misses ammonia properties.

The next chapter, Materials and Methods, again proceeds with the wide introduction by reporting MARPOL regulations.

The relevant Materials and Methods starts only on line 233, by describing the fuel, the engines and fuel system setup. Line 255: the term output range is inappropriate. Should be output power, or MCR, or similar.

Line 305: gas turbine?!? wasn't it a diesel engine?

308: the term specific useful fuel is inappropriate, You mean specific fuel consumption?

Line 308: If the exhaust gasses analyzer is specified and described (Testo340), I would expect more details on the engine output power measurement, more then just "electronic equipment".

Line 332: what does NMG stand for?

Line 327: "not taken in a view"? You mean not considered?

Line 332-333: additional...additionally: repetition

Line 360: What does list mean?

Line 365: per volumetric present? You mean volume ratio?

Table 1. It could be explained better then "Experiment data"

The formulas (4) is trivial, and does not need to be explained or reported.

Table 2 just repeats the results from table 1, but the relative amounts, which are already presented graphically in figure 3, so I find it unnecessary.

Line 421. carbon oxides? You mean monoxyde? carbon dioxyde is not toxic.

Line 467: temperature tension? You mean temperature stress?

Lines 469-472: It is obvious, does not need to be explained.

Lines 506-508 repeat the same sentence from 505-506.

The References section is very long.

The article is based on diesel engine power and emissions measurement, but it is not written concisely and the style is sometimes difficult.

Author Response

For reviewer 2.

The experimental setup is well described but there is given too much introduction and context, in the way that distracts from the focus of the experiment.

We have given a detailed description so that the sequence of experiments is understandable not only to specialists in this field, but also to everyone who will read the article. Also, a detailed description confirms the correctness of the technology of the experiment.

The introduction is too wide. It explains about all problems of other energy sources and carriers, should be shortened. Lines 55-57 does not stand, there are some very large cruising ships powered by methane (MS Iona).

We have taken your comments into account and have changed this phrase:

The use of gaseous fuels is possible only on a limited type of ships (gas carriers and some tankers) on which this fuel is transported as cargo and also on some very large cruise ships that are powered by methane [14].

Line 69: emissions of carbon oxide...it is imprecise. Is it monoxyde or dioxide that is limited?

We corrected according your remarks

“…the emissions of carbon monooxides are limited [17]”.

Line 88: unclear sentence, private nature?

We corrected according your remarks:

For power plants of sea and inland water transport, the use of alternative fuels has a limited case.

Lines 106 ...118, out of subject, describing properties of natural gas?

The following sentences was add.

At the moment, the following alternative fuels are used and actively promoted on marine vessels.

Further describes use of hydrogen, shortcomings of methanol...In my opinion it misses the subject. If it would be an alternative fuel revision, it misses ammonia properties.

We have tried in this section (Literature Review) to provide a brief overview of possible alternatives to fuel oil. Further, as one of the options, proved the possibility of using biofuel FAME.

The next chapter, Materials and Methods, again proceeds with the wide introduction by reporting MARPOL regulations.

In the following, we present the characteristics of diesel fuel and biofuel, including their sulfur content. This description ensures that the experiment complies with MARPOL requirements regarding the sulfur content of the fuel. Also in the next section of the article, the emission of nitrogen oxides is calculated in accordance with the diagram shown in Fig. 1. Therefore, this section contains the main requirements of Annex VI MARPOL

The relevant Materials and Methods starts only on line 233, by describing the fuel, the engines and fuel system setup.

In lines 182-232, we have given the features of the operation of marine diesel engines on biofuel, as well as the requirements that must be met. In our opinion, this is directly related to Research Methods.

Line 255: the term output range is inappropriate. Should be output power, or MCR, or similar.

Thanks, we use your advice “output power”.

Line 305: gas turbine?!? wasn't it a diesel engine?

In accordance with the requirements of the NOx Technical Code, the analysis of exhaust gases was carried out in the gas outlet line at a distance of 10 m from the place where gases exited the gas turbine of diesel turbocharger.

308: the term specific useful fuel is inappropriate, You mean specific fuel consumption?

We corrected according your remarks:

specific fuel oil consumption

Line 308: If the exhaust gasses analyzer is specified and described (Testo340), I would expect more details on the engine output power measurement, more then just "electronic equipment".

The gas analyzer was an additional measuring element. Diesel power was measured by standard control equipment, which is included in the package of the central control room.

Line 322: what does NMG stand for?

NMG – it’s model of the electromagnetic flowmeters (as Testo – for gas analyzer).

Line 327: "not taken in a view"? You mean not considered?

Yes, we meant it. We correct according your remarks.

“…the error in measuring the time was not considered”.

Line 332-333: additional...additionally: repetition

We correct according your remarks – without “additionally”

“…in the fuel system of which additional equipment was additionally installed.”

Line 360: What does list mean?

We correct “ship roll”.

Line 365: per volumetric present? You mean volume ratio?

Yes. We mean volume ratio. But not to write in subsequent tables “volume ratio” we use “volumetric present” and in table – “volume %”.

Table 1. It could be explained better then "Experiment data"

We correct

“Results of the experiment”

The formulas (4) is trivial, and does not need to be explained or reported.

The formulas (4) are trivial, but they explain how the calculation was done. We could not write "the relative change in indicators is ...".

Table 2 just repeats the results from table 1, but the relative amounts, which are already presented graphically in figure 3, so I find it unnecessary.

Table 1 shows the values of the parameters with units of measurement. This makes it possible to evaluate their compliance with the requirements (for example, Annex VI MARPOL – for NO_X emissions and diesels manual – for specific fuel consumption). Table 1 allows you to determine that all parameters are in accordance with the recommendations.

Table 2 and Figure 3 show the relative changes in parameters. Table 2 and Figure 3 complement each other. They allow you to visually determine the best composition of the fuel blend and the best mode of operation of the diesel engine.

Line 421. carbon oxides? You mean monoxyde? carbon dioxyde is not toxic.

Yes? We mean monoxyde. We correct it.

“The emission of carbon monoxides (due to its toxicity) is also an important indicator.

Line 467: temperature tension? You mean temperature stress?

Yes? We mean temperature stress. We correct it.

…“temperature stress”…

Lines 469-472: It is obvious, does not need to be explained.

We remove these lines.

Lines 506-508 repeat the same sentence from 505-506.

We remove lines 505-506.

The References section is very long.

We included many references in the introduction and literature review sections because we wanted to show the relevance of the problem and a large number of options for solving it.

The article is based on diesel engine power and emissions measurement, but it is not written concisely and the style is sometimes difficult.

Thanks to the responses to your comments, we have tried to solve this problem.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Even if some of my comments were not taken into account, i accept the paper in the present form. As a suggestion, please properly consider reviewers' comment next time, accepting or rejecting them but with a rational justification.

Author Response

We tried to take into account all your comments and made correction in our last version of manuscript.

Reviewer 2 Report

The authors answered to my complains and improved the paper.

However I still noticed different spelling errors and unclear sentences (even if I am not a native English speaker), so I suggest a serious language check and correction. I do not find the paper particularly innovative but it can be published, after a detailed language correction.

For example:

36 turbine unite?, you mean unit?

70 emission of carbon monoxydes?, should be monoxyde, singular

85 reformulate the sentence

91 ..has a limited case.? Unclear

347 I do not understand „ship roll” in this context

Author Response

We have taken into account your comments. Our fixes are marked in blue.

We have also taken your suggestions to improve our English.

Author Response File: Author Response.pdf