Synthesis of Biomass Corridor in Peninsular Malaysia via Hybrid Mathematical and Graphical Framework

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This paper is written in a clear and engaging manner. All sections are well-structured and easily comprehensible, notwithstanding a few minor typos throughout the manuscript. The approach taken to solve the optimization problem is quite interesting, and the methodology description allows readers to replicate the approach in different scenarios. However, upon reviewing this version, certain technical shortcomings in techno-economic and natural resource modelling came to light, which are crucial for the accuracy of the results. Thus, I would like to present a summary of the problems found in the model and manuscript:

Line 267: The equation (1) referred to as gross profit in the text is, in fact, a cost equation. According to theory, gross profit is obtained by subtracting the cost of goods sold (COGS) from revenues. Hence, since there is no revenue term in equation (1), it cannot be called gross profit.

Lines 362 to 365: The authors need to justify why they chose to use capital recovery factor (CRF) to account for CAPEX. Technically, CRF is a figure of merit that should apply to all annual payments or annual cash flows. Applying a CRF to only the capital investment term in equation (16) means that this term is updated to present value, but CGP and CTR are not. A depreciation method would be a simpler and more straightforward option.

Line 368: The statement presented here needs to be corrected. At the very least, the term CTR is nonlinear. Therefore, the proposed model is a nonlinear mixed-integer nonlinear programming (MINLP). However, according to the explanation in the text, the problem is "linearized" using multiple linear regression (MLR) to obtain a mixed-integer linear programming (MILP). If I understood this correctly, the text needs to be amended, but if not, the authors need to provide a justification.

Figure 6: There is a typo. In technologies, "palletising" is used instead of "pelletising."

Table 1: The references are outdated, and most of them are not specific to Malaysia. For example, [57] dates from 2013, [58] from 2019, [59] from 2002, etc. There is no mention of a method to update these prices to 2023. Moreover, some prices seem unusually high or low. For instance, at 0.14 USD/kWh, electricity is too expensive to be competitive in most electricity markets. The expected value should be less than 0.05 USD/kWh. The price of rice husk is uncharacteristically low. A brief online search revealed that this product has other competitive uses in Malaysia, therefore such a low price would be unrealistic. The same applies to rice straw. In summary, the lack of accuracy in feedstock and product prices is a critical problem in this paper, as it invalidates the profitability results and all optimization results obtained in the following sections. Therefore, it is strongly recommended that the authors find current, Malaysia-specific prices for all feedstock and products and recalculate all calculations before revisiting their results and conclusions for an improved submission.

All the paper: It is recommended that the use of energy pack as a potential product be reconsidered. As per Reference [57] itself the literature suggests that energy pack is merely a theoretical proposal combining oil palm residues and waste motor oils, and nowdays is not available in the market. Therefore, the paper should better reflect on the absence of the actual market for this product at present by removing it.

Line 385 and onwards: the allocation of biomass residues to each technology option is unclear. With no major technological restrictions, in principle, all the biomass residues could be processed using any of the technologies discussed. Hence, the paper should explain why specific combinations of biomass residues and technology options were chosen for the analysis.

Regarding Table 2, the term "combustion" should not be considered a technology. This is a termochemical reaction. The tag "High-pressure steam production" would be more appropriate.

Table 3: it is uncertain whether operating costs include maintenance costs. Additionally, capital and operating costs were obtained from References dated from [2010, 2013, 2015], which raises questions on the validity of the capital investment and cost-related results. Furthermore, the Energy pack production does not have a capital cost.

lines 408 - 411: the paper briefly mentions the biomass origin, but fails to explain how the biomass quantities were obtained, nor does it specify which crop production and residues to crop ratio were utilized in the calculation or what yields were considered for the mentioned production areas. It is important to note that these biomass residues may have competing uses, such as animal feed or in alternative industries, and a portion should be left in the field for fertility reasons. As such, not all biomass residues may be available and accesible as expected by the model. The implications on food security and crop production for excluding biomass residues without proper analysis are critical issues and should be properly addressed, especially if the authors expect to publish in a reputable journal, such as Sustainability.

lines 414-419: In the paper, the authors explain the export market as demand points. However, they suddenly explain that electricity and MPS are sold to nearby markets, which seems logical but is not captured properly in the model. Additionally, the authors have not considered the specific conditions required for potential overseas transport of syngas, such as highly pressurized vessels in the model, which is an important factor.

Table 4 presents transportation costs that are unusually high for the volumes moved. The discount rate is also unusually low, particularly considering the current global economic situation. The authors need to provide justification for these figures and include appropriate references.

In Section 4.1, the authors have erroneously used the term sygas instead of biogas. They need to rectify this mistake. The term EP is introduced suddenly with no explanation about its meaning, which is not desirable in academic writing. The authors should provide a clear explanation of the term.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report

Please revise the manuscript follow comments as shown in attach file. 

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 4 Report

This study conducted on Synthesis of Biomass Corridor in Peninsular Malaysia via Hybrid Mathematical and Graphical Framework. Overall, this article is interesting and discussed the several innovative points such as Identify the optimal location to set up the processing hubs (sinks) in Peninsular; Evaluate the optimum allocation of various types of biomasses for valorisation; Identify the most significant parameter to the net profit in the optimisation model.

I suggest authors to pay more attention to the scientific literature on this topic. Also, it would be much sufficient to include few examples of oil palm, paddy, and coconut supply chains. 

 

Figure 2 quality is poor. It is difficult to read.

Authors did not properly supported their findings. Please support your results with published scientific articles. Furthermore, researchers needs to develop some debate in discussion section on the similarity and dissimilarity of their findings with published articles.

Practical implications, theoretical contribution, limitations of study and future research avenue. These needs to be included as a subsection in conclusion part.

Appendixes should be listed after reference sections.

 

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Agreed

Reviewer 2 Report

After thoroughly reading the updated version of this paper, I have found that the authors have responded comprehensively to all comments and suggestions. The provided explanations were convincing, making this paper worthy of publication.

Congratulations to the authors for their effort and achievements. I thoroughly enjoyed reading the paper and gained substantial knowledge from it.

Reviewer 4 Report

Accepted