Biomass Fuel Production through Cultivation of Microalgae Coccomyxa dispar and Scenedesmus parvus in Palm Oil Mill Effluent and Simultaneous Phycoremediation

Round 1

Reviewer 1 Report

Excellent work...If possible measure the viscosity and add in to this manuscript.

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

 

This paper describes a fairly extensive but routine study of biomass production in terms of two types of microalgae grown in palm oil mill effluent. It needs additional work, including clarifications and language corrections (see examples below), but otherwise it seems okay for eventual publication.

 

Examples of clarifications needed:

- The title promises “Biomass fuel production”. The Abstract is more ambiguous, referring to “potential production of biomass fuel” (line 11). Line 333 refers to “energy released from combustion of biomass fuel”. Is the dried biomass the fuel? Is this a solid or liquid fuel? This should be clarified.

 

- Line 9: “biomass fuel upon treatment using microorganism[s]” Please specify what treatment.

 

- The POME has to be dried before combustion (line 183). How much energy does that require compared to the CEV?

 

- Please define abbreviations like POME (first word of the Abstract, and at first mention in the text in line 31), COD, BOD, and TSS (line 32).

 

Line 91: “high calorific energy value (CEV) biomass fuel, which [is] indicated by [the] high carbon content” It is known and has been proven quantitatively (e.g. in https://doi.org/10.1021/acs.jchemed.5b00333) that the hydrogen content also contributes to the CEV. This should be pointed out, with a reference.

 

Line 112: “removing the contaminants.” Please specify which.

 

Line 124: “under controlled culture room” Change to “in a controlled culture room”

 

Line 124: “illuminated light with photon intensity” Change to “illuminated with light of photon intensity”

 

Table 1. “CEV for” Please specify the units.

 

Table 2. The caption of the table does not mention the elemental composition data shown, and whether they are for day-1 or day-14. Please specify that the values are wt%.

 

Line 330: “touted as prevalent to be adopted” is not clear and needs to be rephrased.

 

Line 531: Please rephrase this unclear sentence in the Conclusions.

 

- The words “viz” and “In lieu,” need to be replaced everywhere with more common English expressions.

 

- On pages 10-12 and elsewhere: Many percentages are given with four significant figures, but the large error margins in the corresponding figures show that this is not justified. In many cases, percentages should be reported only rounded to the nearest integer, i.e. without a decimal point. For instance, “13.60%” should be replaced with “14%”.

 

Examples of language issues:

The text needs to be read and corrected by a native English speaker. Incorrect word endings are unusually common in this text. These include:  

“exhausted gases”

“to emphasizes”

“in term of” (at least twice)

“three type of”

“was grow in”

“utilized lesser light”

“two selected growth mode of”

“show a decline trend”

“a decreased trend”

In particular, there are many incorrect endings of “ed “, e. g. 6 instances in lines 35-40 alone.

 

Grammatical and other errors include:

“prior entering”

“One of the microalgae species Chlorella is the most common microalgae to produce”

“prior to be used”

“four various concentrations”

“, pH approximately 4.0”

“under fluorescent light 6500 K”

“stabilised for two days prior usage”

Line 114: “activation … were performed”

 

“potray the”

 

- There should be no space between a number and %.

- On p. 4, the article “the” is missing in several places. And later in “At initial stage”.

 

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors propose the cultivation of Coccomyxa dispar and Scenedesmus parvus on palm oil mill effluent (POME) both to produce fuel biomass and for phycoremediation. The study proposes an alternative process for the treatment of POME, identifying S. parvus as a suitable candidate to produce biomass fuel better than C. dispar for a scale-up. The manuscript is sufficiently accurate. However, minor adjustments are required before publication.

In general: standardize the way of writing liters in "L" and not in "l" even in submultiples. Check throughout the manuscript.

Abstract

Pag. 1, Line 9, Please write “POME” in full and then the abbreviation in parenthesis.

P1, L13-14 Please remove “room temperature” and replace “viz.” with parenthesis. Please remove “mode” after “autotrophic”.

P.1, L.21 Please replace “from” with “in”.

 

Introduction

P1, L31 Please write “POME” in full and then the abbreviation in parenthesis.

P1, L39-40 Please, replace “will caused” with “causes”.

P2, L45-46 Please rewrite as follows: “comprising approximately 64% CH4, 36% CO2, and 670-2500 ppm H2S.

When you refer to “The large uncontrolled proportion of CH4…” what do you mean? Where do these emissions come from? A digestion plant does not emit CH4, on the contrary, it tends not to have losses for obvious economic reasons. Please write better.

 

Materials and Methods

In my opinion, it would be better to replace “prior” with “before”, in this section.

Is it necessary to divide this section into many sub-paragraphs? Wouldn't it be better to group the various methods and reduce the paragraph length?

P.3, L.109 Please, rewrite as follows: “In this study, two acidophile species of microalgae (Coccomyxa dispar and Scenedesmus parvus) were used…”

P3, L129 Please, replace “Next” with “In”, delete “required” and add “was required” after “species”.

P3, L141 Please, remove “room temperature”

P4, par. 2.4. Please, specify what was the wavelength

 

Results and Discussion

Please, conjugate all verbs in the past tense; uniform throughout the text.

P6 L266 Please, remove “recorded at” and put the OD values in parentheses. The same at lines 268 and 273

P7 L275 Please, remove “mode growth”.

P7 L277 Please, remove “As”.

P7 Fig. 2 Do the authors have an explanation for the higher ODs being 20 and 80% and then 40% and 60%? That is why there is no progression in the OD value that reflects the %.

P10 L378 Please, remove “that”.

P10 L391-394 Please, provide examples and/or references.

P11 – 13 Figures 4, 5, and 6 What was the initial COD and BDO concentration? Given that COD removal efficiency is similar between S. parvus and C. dispar, a different biomass yield cannot be explained if the initial COD concentration was different, as it would seem after 1 day, from figures 4 and 5. On the contrary, what happens to the COD and the BOD removed?

P12 L430 Please, write better: “In autotrophic mode, at day 4 BOD remove efficiency for S. parvus was similar to other, then it decreased; whereas for C. dispar it was always lower than other. However, the lowest BOD removal efficiency was caused by the absence of organic matter”. However, the BOD removal efficiency should be independent of whether there is little organic material since it is a percentage. Explain better: since the focus is on the removal efficiency, it can be said that in autotrophic mode the BOD removal has less efficiency compared to other growth modes, maybe due to less biodegradability of organic matter. In the absence of organic matter, indeed, the BOD efficiency should be around 0%. Whereas the absence of organic matter explains better the better efficiency of COD removal in comparison to BOD removal efficiency.

P14 L496-497 Please, replace “insignificant” with “not significant”; at line 497, do you refer to the final COD concentration?

 

P14 504-511 The paragraph is inconclusive and lacks discussion.

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf