Cost Comparison for Emerging Technologies to Haul Round Bales for the Biorefinery Industry

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

My comments are attached.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Author Response

                                                       Response to Reviewer 1

Journal:  AgriEngineering 

Title:  Cost Comparison for Emerging Technologies to Haul Round Bales for the Biorefinery Industry Manuscript No.:  AgriEngineering 2950329

This Research Paper focuses on the economics of large round bale logistics, specifically in regard to biomass feedstock logistics.  This topic is appropriate to be considered for publication in this journal.  The results are important to the field of biomass logistics and once published it will make an important contribution to the literature in this area.   However, in its current form, this manuscript is not ready for  detailed review and needs substantial revision before a detailed review can be conducted.  Here are my concerns:

• The manuscript is excessively lengthy and frequently challenging to follow. Certain sections lack clarity or contain redundant information.  To enhance readability, careful editing and culling is necessary to streamline the content, making it more concise and coherent.

Response: The authors very much appreciate the effort this reviewer invested in their review. We have tried to include all suggestions.

• A word search found seven instances of “DOE project”. Frankly, the number of times I see “DOE project” makes me think that you feel obligated to acknowledge the DOE at every turn.  It is not necessary to acknowledge DOE funding like this.  If you feel this is needed, put it in the Acknowledgement section.

Response: This study received no funding from DOE. We are not acknowledging funding.  The references are to reports of DOE projects which developed to ALSS and Rack prototypes. We believe it is appropriate to give credit for the important work done by DOE to improve hauling efficiency.

• I found it disconcerting to not see the “$” in front of the costs. Please use this symbol throughout the manuscript.  

Response: We are, of course, glad to follow this convention. At the editor’s direction, we will change this. Often the “USD” is used to refer to US dollar.

• Abstract:
• There is a lack of clarity regarding the importance and impact of this work. Please start with one or two sentences better describing the problem.  The challenge is high costs of handling and transport.  Consider ending the with a concluding sentence that tells reader how the different systems helped  overcome this issue.  Simply state that three systems were considered and state the main difference between these.  Actual cost values are not important in this section – provide the reader with the main reasons why the system’s costs were different and the end with a concluding sentence or two as to why this result is important.

Response: The abstract has been rewritten. We begin with a statement that 20 to 30% of the delivered cost of feedstock is the highway hauling. We did leave in the last two sentences which summarize the cost results.

• Introduction:
  • This is where there should be a literature review that provides sufficient clarity on the importance and impact of this work. Of the overall costs of biomass delivered costs, how much is related to handling and transport?  Is this where the greatest cost reductions can be made.  Why was so much time and treasure spent on developing and conducting analysis of these handling and transport options.

Response: The cost for a farmgate contract (grow, harvest, and store in SSLs) is probably going to be about $120/Mg for perennial grasses in the Piedmont. Total delivered cost is then 120 (farmgate contract) + 35 (load-out and highway hauling) = $155/Mg. This means that the delivery is (35/155) 100 = 23% of the average delivered cost. If the Excel system is used, then 120 +50 = $170/Mg. The delivery cost is (50/170) 100 = 29% of the average delivered cost. If we include these statements, then the reviewers will ask where the $120/Mg farmgate cost comes from. It comes from a study we did about 3 years ago. If we reference this study, done using the conditions found in the Piedmont, we will be referencing our own work, which is criticized. We decided to include the following statement. “The highway hauling of feedstock is generally between 20 and 30% of the average delivered cost to deliver a stream of round bales for processing 24/7, 48 wk/y.”  

Is this where the greatest cost reductions can be made? We think that the in-field hauling (the movement of bales from the field into SSL storage) is probably the place where the most progress can be made. However, we cannot prove this at this time. The Stinger in-field hauling technology, we think, can be successfully implemented in the Piedmont. However, it has not been done.

• Sections 1.1 and 1.2 are not really Introductions – they describe specific handling and transport options and deserve a separate identified section. Also, put the Objectives at

the end of the Introduction and then provide details of the handling and transport options in the next section.

Response: Done.

• Line 30: “The argument against round baling has historically been the lack of an efficient system for highway hauling”.  This is one of many, many reasons why large round bales are not considered the best option for biomass feedstock packaging: low field productivity, low density, poor use of transport volume, poor value conservation during prolonged outdoor storage, high ash content, etc.

Response: We changed the wording to indicate that highway hauling is ONE of the arguments against the round bale. We do not agree with the reviewer’s entire list of “round bale negatives”. As might be expected, our work focuses on the round bale because we believe in its potential for the conditions found in the Piedmont.   

• You could consider indicating that this work concentrates on perennial grass biomass and not corn stover.

Response: Done. There is not sufficient wheat grown in the Piedmont to provide significant wheat straw. There is not sufficient corn grown to provide significant corn stover.

• Lines 47 – 57: This paragraph is too long and could be reduced to one or two sentences.  I don’t recall seeing a calculation like this in an Introduction.  This should be moved to an Appendix.

Response: Para. shortened. Calculation eliminated.

• Lines 61 – 71: This paragraph is also too long and could be reduced to one or two sentences.  

Response: Done:

• Results and Assumptions:
  • There is not a clear distinction made between sections that are Assumptions and sections that represent Results. I have reviewed quite a few techno-economic (TEA) publications, and they all use a format where Assumptions are provided first, then a separate section for Results.  Please edit to ensure that there is a clear distinction between these two sections.
  • Most TEA publications have one or two large tables where all the major assumptions are located in a focused location(s). Please do that here as well.

Response: Assumptions (constraints) are now listed in Table 1 for the structure of the industry. Table 2 has the key parameters for the load-out simulations and Table 3 has the key parameters for the hauling simulations.  We also did some                                     reorganization to clarify the results, including changing some subheadings. We appreciate this guidance and hope we have increased the clarity and conciseness. 

 

• Proposed Structure of Industry for the Comparison o This section is very confusing – it is hard to distinguish what are assumptions and what are results. Please edit for clarity and consider moving information of less importance to an Appendix.  This section is very long considering the information provided.

Response: Material was moved to two appendices.

                                                                      Appendix A

                                     Number of Racks (and rack trailers) Required for Rack System

                                                                     Appendix B

                                                     Design of Receiving Facility

 We also edited to reduce length.
                   

o Make sure that you separate Assumptions from Results.

Response: Done. See new Tables 1, 2, and 3.

• Required Hauling Equipment o Section 4.1:
  • The first paragraph can be shortened to one or two sentences. The discussion of the “leftovers” is not needed.
  • Lines 308 – 322 should be put into an Appendix.

 

Section 4.2:

• This should be either deleted or put into an Appendix.

                               Response: Sec. 4.2 was shortened. Sec. 4.3 was moved to Appendix A. We did not eliminate the discussion of the “leftovers”. Why? The feedstock contract holder needs to be paid for the total material they produce. It is not fair for them to have to absorb for cost of the left-behind material. The amount of left-behind material and the cost for a clean-up crew to haul it is a component of the logistics system.

• Section 5: This section should be moved to an Appendix.  The last few paragraphs on the productivity could remain in the text, but the details of the storage pads, size of stacks, etc. are not essential to the cost analysis, which is the main objective of this work.

Response: This material was moved to Appendix B

• Section 6:
  • This is the heart of this manuscript, but it is incredibly difficult to follow as there is way too much detail provided. This section feels like it was copied from a grant final report, and then pasted without editing for length and clarity.

Response: The authors agree that we did not present our work with clarity and conciseness. However, this is not a “cut and paste” job; it is original work.   

• Somehow this has to be a simpler way to convey these results. Table 6 shows that the Excel system requires almost twice as many truck loads.  The Rack system requires specialized equipment, so their costs are greater.  Table 8 shows that most of the cost differences are related to these two factors.  Knowing this, please consider making this entire section much shorter by zeroing in on the most important differences and then move much of the rest of this section into a short Appendix.

Response: Table 6 shows that the Excel system requires almost twice the “truck operating hours”, not “truck loads”. Editing was done to reduce length and, we hope improve clarity.

• Discussion:
  • This section should inform the readers as to the implications and industry measures that can be implemented with this new information. Provide examples on how to utilize this information, i.e. carry the reader to where and how they can best use this previously unknown information.

Response: With this study, we hoped to quantify a) the potential for rapid load and unload technology to reduce truck cost, and b) the need for central control of trucking get a truck at the correct SSL at the correct time, and thus minimize wait time to load. We believe we accomplished a) and established a need for a follow-up study to address b).  

• There should be comparison with costs of handling and transporting large round bales from other published work. How do your results compare with the many of the TEA analysis of biomass logistics.  Currently there is no such comparison and that should be done.

Response: We did not find published studies on the highway hauling of round bales. Commercial applications use the large rectangular bale because of the higher density and thus the higher load mass. We appreciate that this reviewer begins their review by saying that a study like this should be published; it is a minority viewpoint.  

• There should be a capstone paragraph in that summarizes a critical interpretation of this work. What are your one or two conclusions based on the cost results.

 Response: All short-haul operations are organized to minimize the truck wait time to load and unload. Here, the ALSS-2 trailers are left at the SSL for loading and left at the Receiving Facility for unloading, thus uncoupling the load-unload operations from the hauling. The same procedure is used for the rack trailers. This principle is used for this case study to compare the three technologies. We do not know how to make this clearer.  

 

• Figures:
  • Figure 1: The picture is too blurry.  Please obtain a better picture.  I’m sure Stinger would be glad to supply a picture that shows their product in a better light.  Also, you have misspelled Stinger” and “Singer”.

Response: Figure replaced.

• Figure 2: This figure is unacceptable because of the words “The Excelerator” are placed in the picture.   I’ve never seen anything like that in a peer reviewed journal.  I went to the web site, found a YouTube video of the round bale device and was able to take a clear screen shot of the device.  Please do the same.

Response: Figure eliminated. The company that developed the technology is in the process of selling it to another company. Subsequently, they are not in a position to grant permission to use the photograph. We changed all references to the cable technology from “Excel” to the generic designation “Cable”.

Figure 3:  

• In the Rack system, you have a separate floor to put bales on. This is not the case with the ALSS-2 system.  So, I cannot see how you can stack round bales one directly on top of the other without the top layer rolling into the “crotch” of the bottom layer bales.  You should mention that you have tried this and that it is practical.

Response: The reviewer raises a valid point. We have not loaded an ALSS-2 trailer in the manner shown.  We expect that the telehandler will have to have a “side-shift” capability such that the last bale on the top tier can be shifted to move the previously loaded top tier bales, and then “nudge” the last bale into position. However, this has not been done.  

• You should identify this as an ALSS-2 in the figure title, not just ALSS.

Response: Done.

• Figure 4: Describe what is meant by a “load-out”.  Each figure should be able to stand alone.

Response: Load-out is defined.

• Figure 5: Is this for the 8, 9 or 11 load-out system?

Response: The results for the 9-load-out simulation are used for this figure. Caption is changed to indicate this.

• Figures 6 and 7: Please provide in the figure title the total area, total number of bales in the storage area, and the mass of biomass in this area.  But these two figures should be moved to an Appendix.

Response: Figures moved to Appendix B. And, the areas are now given in the figure caption.

• Equations:
  • There are 28 numbered equations and several that you have missed numbering. This many equations make the manuscript very difficult to read.  I reviewed the following techno-economic biomass analysis and in none of these were there the number of equations used here.  Please put these equations in an Appendix
    • Vadas, P. A., & Digman, M. F. (2013). Production costs of potential corn stover harvest and storage systems. biomass and bioenergy, 54, 133-139.
    • Wendt, L. M., Smith, W. A., Hartley, D. S., Wendt, D. S., Ross, J. A., Sexton, D. M., ... & Kenney, K. L. (2018). Techno-economic assessment of a chopped feedstock logistics supply chain for corn stover. Frontiers in Energy Research, 6,

90.

• Hemmelgarn, A. B., Lin, Y., Wendt, L. M., Hartley, D. S., & Digman, M. F. (2023). Techno-economic assessment of single-stream feedstock logistics supply chain for corn stover and grain. Biofuels, Bioproducts and Biorefining, 17(3), 437-448.
• Vasco-Correa, J., & Shah, A. (2019). Techno-economic bottlenecks of the fungal pretreatment of lignocellulosic biomass. Fermentation, 5(2), 30.

                                      Response: We have reduced the number of equations. There are now 14. We do not believe that the clarity will be improved by putting all the equations into an Appendix. We will be glad to do this, if required by the editor. 

• Tables:
  • It was hard to tell which tables represented Assumptions and which tables represented Results. This should be made very clear.
  • Some tables could be combined – Tables 1 and 2 for instance. Tables 4a, 4b, and 4c could also be combined. 

Response: Table 1 summarizes parameters for the 3 load-out simulations and Table 2 summarizes parameters for the 3 hauling simulations. These are short tables, however, we think it is clearer to keep them as separate tables.

Tables 4 and 5 are good examples of where the results could be made more succinct.  Is it necessary to show the results for every load out number?  In many instances the values hardly change from one load out number to the next.  You could show only the results odd-numbered load outs  and make the tables tell the same story with much less clutter.  Could this data be better represented by a plot?

• Table format: Don’t use so many horizontal lines.  Table 4b is the correct format, Tables 4a and 4b are not.  And dashed lines in a table should not be used.

Response: We eliminated Tables 4a, 4b, and 4c and replaced them with a short summary para.

 We did not include the lines. These were added when the manuscript was processed by the editor. Our revised submission will not include the table lines.

We do believe the dashed lines in Table 8 add clarity, thus these remain.

                

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article compares the costs of three emerging round bale shipping technologies in the biorefinery industry. The main conclusion is that large transport units such as rack systems can significantly increase transport efficiency and reduce transport costs per ton compared to traditional single bale loading methods. This article provides a detailed analysis of the costs of these three technologies, including the entire logistics process from satellite storage point to biorefinery. However, this article also has some shortcomings:

1. Some cost calculations in the article do not have sufficient evidence. For example, for the cable cost of the Excel system, the trailer cost of the ALSS-2 system, and the rack and trailer cost of the rack system, this article only gives an estimate, but does not give a detailed price basis.

2. This article assumes that the equipment operates with high efficiency and low failure rate. For example, in a rack system, this article assumes that each rack can be used an average of 182 times per year, without taking into account possible damage and repairs.

3. The detailed design parameters and operating parameters of some key equipment are not explained in this article. For example, the specific design and operating parameters of the rack loader and rack unloader in the RACK system are not given.

4. This article does not consider the differences in operating costs in different regions and time periods, such as oil prices, labor wages, etc.

5. This article does not analyze the investment payback period of different technologies, so it is difficult to evaluate the economic feasibility of different technologies.

 

6. This article does not consider the impact of different technologies on the environment, such as fuel consumption, equipment wear, etc.

7. This article does not provide applicable conditions for different technologies, such as transportation distances in different regions and transportation requirements for different raw materials.

In summary, this article has some shortcomings in cost calculation and equipment design, and relevant data and parameters need to be further improved to improve the reference value of the paper.

Author Response

Response to Reviewer 2

Comments and Suggestions for Authors

This article compares the costs of three emerging round bale shipping technologies in the biorefinery industry. The main conclusion is that large transport units such as rack systems can significantly increase transport efficiency and reduce transport costs per ton compared to traditional single bale loading methods. This article provides a detailed analysis of the costs of these three technologies, including the entire logistics process from satellite storage point to biorefinery. However, this article also has some shortcomings:

1. Some cost calculations in the article do not have sufficient evidence. For example, for the cable cost of the Excel system, the trailer cost of the ALSS-2 system, and the rack and trailer cost of the rack system, this article only gives an estimate, but does not give a detailed price basis.

Response: The reviewer is correct; only cost estimates are given. We explain that none of the three technologies are commercially available, thus a definitive (more defensible) cost estimate is not possible. We changed some wording to emphasize that the technologies are “potential” technologies. Also, when giving the estimates with a “low certainty”, we use an “lc” designation to tell the reader we this cost estimate is not well defined.    

2. This article assumes that the equipment operates with high efficiency and low failure rate. For example, in a rack system, this article assumes that each rack can be used an average of 182 times per year, without taking into account possible damage and repairs.

Response: The reviewer is correct in their concern. We have the same concern. In the determination of rack cost (number of racks required) we include a 5-rack reserve in anticipation that racks may be damaged and out of service at some point during the year. Only one rack prototype has been built, so obviously we do not have an operational history to report. Should a commercial rack design be built, the usage (180+ cycles per year) will need to be part of the design criteria.  

3. The detailed design parameters and operating parameters of some key equipment are not explained in this article. For example, the specific design and operating parameters of the rack loader and rack unloader in the RACK system are not given.

Response: No prototype of the rack loader has been built, as explained in the text. A prototype of the rack unloader has been built. More development is needed before a commercial design can be done. The authors estimate that maybe 50% of the protype development has been done. This is covered on the Discussion section.

Response to points 2 and 3: Why would someone fund continued development of the rack concept? They should not (and will not) unless there is an expectation that the new technology will provide a more cost-effective operation of the logistics system. Our goal was to complete a “good faith” analysis to make the case for a) a multi-bale handling unit for round bales, and b) an industry organized to achieve central control of trucking.  

4. This article does not consider the differences in operating costs in different regions and time periods, such as oil prices, labor wages, etc.

Response: The reviewer is correct. The paper is already too long---there is no practical way to address these issues in addition to the main objective of our study. See above response to points 2 and 3.

5. This article does not analyze the investment payback period of different technologies, so it is difficult to evaluate the economic feasibility of different technologies.

Response: We did use a relatively simple rate procedure for calculating the hourly cost (ownership + operating) for the various pieces of equipment. If commercial models of the technologies are available in the future, and purchase price is better defined, then we agree that a more complete cost analysis is needed. We used a commercial rent rate for the truck tractors rather than trying to develop a business plan that is typical for a 10 to 20-truck fleet. The mileage cost used for the trailers is typical for the heavy truck industry.

6. This article does not consider the impact of different technologies on the environment, such as fuel consumption, equipment wear, etc.

Response: This question is beyond the scope of our study.

7. This article does not provide applicable conditions for different technologies, such as transportation distances in different regions and transportation requirements for different raw materials.

Response: This is an excellent suggestion for a future study. The key variable is the “feedstock density” defined as the average Mg/km² across a 50-km radius production area. The higher the density, the lower the average delivered cost for feedstock. We would like to see this study done in the future, but cannot commit, at this time, to do it.  

In summary, this article has some shortcomings in cost calculation and equipment design, and relevant data and parameters need to be further improved to improve the reference value of the paper.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The supply of straw bales to the biorefinery must be uninterrupted to ensure continuous operation. So delivery logistics is a priority here. Appropriate calculations of several transport methods were made and their advantages and disadvantages were indicated. However, there are no final solutions indicating the best solutions depending on constant, unchangeable factors such as distances to be covered, processing technologies used in the factory, etc. It is advisable to develop a computer system to support making these important decisions in conditions of uncertainty (this is missing here) and risk. The results are too arbitrary (this is a case study) because they concern a specific task, and they should be more universal and therefore valuable for logistics practice.
Megagram (Mg) is the SI unit of tonne (t). If so, we always write it in a straight font, not in italics.
Units need to be standardized. The SI system applies, so feet would have to be converted to meters throughout the work (line 29, e.g. 63, 75 or the description of Figure 1).
I guess there is no need to show subsequent stages of calculations in chapters 4.3 and 6 (but also in chapter 1, equation 1), it does not look scientific. General equations and final results are enough and should be presented in charts rather than tables. They are then more legible.
Modest bibliography. Similar problems also occur in Europe and Asia and are being solved on an ongoing basis.

Author Response

                                                 Response to Reviewer 3

The supply of straw bales to the biorefinery must be uninterrupted to ensure continuous operation. So delivery logistics is a priority here.

Response: The only viable option for a herbaceous feedstock in the Piedmont is a perennial grass, like switchgrass. The amount of wheat grown in not sufficient to provide the needed straw. Also, the amount of corn grown does not provide to opportunity to harvest sufficient stover.    

Appropriate calculations of several transport methods were made and their advantages and disadvantages were indicated. However, there are no final solutions indicating the best solutions depending on constant, unchangeable factors such as distances to be covered, processing technologies used in the factory, etc.

Response: We presented our average delivered cost results for the three emerging technologies. We tried to present the methodology for the calculations in sufficient detail for the reader to make their own judgement as to the value of the cost comparison for the three technologies. The least cost option, by a small amount, was the ALSS-2 technology. However, the reduced receiving facility handling benefit offered by the rack system is probably undervalued in the analysis. Thus, we do not attempt to make a definitive statement as to the “best” option. Both the ALSS-2 and Rack options desire further study.

It is advisable to develop a computer system to support making these important decisions in conditions of uncertainty (this is missing here) and risk.

Response: There is software that has been developed for, and is used by, many other logistics systems: solid waste truck fleets, warehousing operations which delivery to retail outlets, police patrol fleets, taxi and similar fleets, ect. The authors believe that there will be a day when this software will be adapted and used to operate the truck fleet supplying a biorefinery. The Feedstock Manager at the biorefinery will know the location of each truck at all times and can direct the fleet the minimize wait time at the several load-out operations. We believe this computer support will, as this reviewer suggests, reduce the risk in the operation of the logistics system. The authors would also like to see this software developed, improved with real-life operational data, and then utilized for the biorefinery industry.   

 The results are too arbitrary (this is a case study) because they concern a specific task, and they should be more universal and therefore valuable for logistics practice.

Response:  There are results presented for a total of 9 load-out and hauling combinations, and the authors need specific examples of what factors or issues are "arbitrary." This comment is difficult to respond without some specific examples.

Megagram (Mg) is the SI unit of tonne (t). If so, we always write it in a straight font, not in italics.
Units need to be standardized. The SI system applies, so feet would have to be converted to meters throughout the work (line 29, e.g. 63, 75 or the description of Figure 1).

Response: These changes have been made.

I guess there is no need to show subsequent stages of calculations in chapters 4.3 and 6 (but also in chapter 1, equation 1), it does not look scientific.

Response: These changes have been made.

 General equations and final results are enough and should be presented in charts rather than tables. They are then more legible.

Response: The authors do not agree. We submit that Table 8 is the best presentation of the average delivered cost for the 9 load-out and trucking combinations. 3 load-out simulations x 3 hauling simulations give a total of 3 x 3 = 9 combinations. Thus, a range of results are available to the reader.

Modest bibliography. Similar problems also occur in Europe and Asia and are being solved on an ongoing basis.

Response: Many of those studying feedstock logistics have “written off” the round bale. We found a number of studies that have evaluated technologies for the highway hauling of large rectangular bales. We did not find another study that compared technologies for highway hauling of round bales. The authors believe that, generally, a more focused bibliography is the better approach to the review of literature.