The Production of Gaseous Biofuels Using Biomass Waste from Construction Sites in Recife, Brazil

Round 1

Reviewer 1 Report

 Several points.

 

Would you mind clarifying why CCbiowaste is better compared to other bioenergy feedstock. Brazil's soybean is the main feedstock to biofuel. It is more interesting to know which feedstock is mainly for bioenergy. Compared to that main feestock, why ccbiowaste is more attractive? Basically, this study lacks a concise and clear introduction and literature review for the bioenergy industry for Brazil. Therefore, it is hard to understand the research drive.  If it is possible to include some economic analysis in the purchasing part.?

Author Response

 

First of all, thank you for your suggestions. I will respond to all comments/suggestion below.

 

1) Would you mind clarifying why CCbiowaste is better compared to other bioenergy feedstock.

The CCbiowastes are produced in all cities and mainly they are dumped in landfills or in open dumps (in Brazil, they are even left in the streets). They represent a serious environmental problem. The low moisture and ashes content, high volatility enables the CCbiowaste to be converted in gaseous fuels and used to run an Otto engine to produce electricity. They are concentrated in cities and are ready to be used even in the construction site.  The benefit includes the reduction of the environmental problems while generating electricity. Besides, some authors have reported that when landfilled, the wood wastes present no sign or very little degradation, hence, they won´t degrade and will accumulate in landfills.  And, woody feedstocks are not available in the cities. Normally, they come from energy crops farms and have to be processed and require transportation, while the ccbiowastes are available in the construction site, and energy can be used at the site. Using wastes are always a better option to WtE sustainable projects.

2) Brazil's soybean is the main feedstock to biofuel. It is more interesting to know which feedstock is mainly for bioenergy. Compared to that main feedstock, why ccbiowaste is more attractive?

Soybean wastes are left in the soil in order to reduce the amount of fertilizer required for the crop. Part of them could be used for energy generation purposes, however, due its high moisture content, will require drying and the collection and transportation of soybean residues would be a problem, as they are used to recompose the soil nutrients.  

 

3) Basically, this study lacks a concise and clear introduction and literature review for the bioenergy industry for Brazil. Therefore, it is hard to understand the research drive. 

I have included a more concise literature review, showing the importance of using ccbiowastes as feedstock for energy purposes. Hopefully, you will be satisfied.

 

4) If it is possible to include some economic analysis in the purchasing part.? 

It was not the intention of this paper to provide an economic analysis. However, it showed the feasibility of using ccbiowastes to produce energy in form of electricity.  The use of such wastes will avoid tipping fees and transportation costs to discard them in landfills. Besides, several authors concluded that it much better to use the waste to produce fuels, that substitute fossil fuels that pollute more (due to GHG), at the same time the contributes to the sustainability as biomass is carbon neutral whilst reduce the environmental problems caused by wastes. 

As mentioned in the paper, there are only few researchers using landfill-derived wood and C&D wood as feedstock in their gasification studies. Hence, the intention, mainly, was to show results, so this technology can be used in construction sites to enable them to be sustainable and residues-free.

Reviewer 2 Report

Dear Authours,

The manuscript shows specific properties and some economic analysis of different biomass waste from construction in Brazil. This results are a simple analysis with a very little novelty - there is a lot of literature about biomass/waste properties. Obtained result if will be reconsider by Editors should be complete by:

scheme of experiment set-up, more economical analysis, statistical analysis (to show a different beetween materials), significant extend the all results and discussions sectio.

The most important is to emphasize the novelty of this manuscript. Maybe you should reconsider to change manuscript in in the direction about environmental problems and add some mathematical models?

Specific comments in attachment.

 

Comments for author File: Comments.pdf

Author Response

Reviewer 2

Response to the Reviewer 2.

Thank you for your suggestion and guidance.

We have made modifications on the paper that included your suggestion. Hopefully, you be satisfied with the answers provided.

 

Some answers will be given below. 

1) The manuscript shows specific properties and some economic analysis of different biomass waste from construction in Brazil. These results are a simple analysis with a very little novelty - there is a lot of literature about biomass/waste properties.

This is true for several countries. However, this work was the first one, in Recife-Brazil that analyzed and characterized the biomass wastes in the construction of a residential building. Normally, the wastes are sent to landfills or open dumps. This paper showed that a better solution is to use the biomass wastes (CCbiowastes) as feedstocks to generate gaseous fuel (through gasification) and to produce electricity, besides avoiding the transportation costs to landfills and tipping fees, also reduces the cost on electricity at the construction sites.  

You are correct when stated that there is a lot of literature about biomass/waste properties. However, there are not so many on construction wood wastes, especially in Brazil. For this reason, it is good to know, what are the most common wood biomass used in construction in Brazil and their properties; also, the use of the ccbiowastes in WtE Projects would contribute to sustainability and less landfilling.

2) Obtained result if will be reconsider by Editors should be complete by:

- scheme of experiment set-up (it was done);

- more economical Analysis (it was not the intention of the paper, even though it has the value of the electricity than can be sold to the grid). More research has to be done on gasification and the economic part. One of the main problems to carry out an economic Analysis is the fact that the gasification is not a well-developed technology yet, and there is no ready-to-use pilot plant or commercial plants with costs that have to be taken into account. For this reason, this research described only the technical issues of converting solid waste to fuels and electricity. The value of electricity could be obtained. However, the costs to manufacture a gasifier connect to a genset are still unknown.

3) statistical analysis (to show a different between materials).

It was implemented on the manuscript.

4) significant extend the all results and discussions section.

It was implemented on the manuscript.

5) The most important is to emphasize the novelty of this manuscript. Maybe you should reconsider to change manuscript in in the direction about environmental problems

It was considered the environmental problems caused by wood waste landfilling and the solution to reduce the problem with ccbiowastes.

6) Add some mathematical models?

It can be done in another paper, as this manuscript did not focus on this.

Specific comments in attachment.

The answers to your comments are in the attachment.

 

Thank you very much for your comments. It really helped a lot to improve the quality of the paper.

Author Response File: Author Response.pdf

Reviewer 3 Report

Manuscript Number: Processes-694079

Article Type: Research article.

Title:  The production of gaseous biofuels using biomass waste from construction sites in Recife - Brazil

Comments:

In this manuscript, authors used biomass waste to produce biofuels. Although the topic has scientific interest but authors fails to explain it properly. Needs more clarifications. Overall manuscript needs further improvement. My specific comments are below:

Introduction section did not organize well. Need more background information followed by specifically mentioning the novelty of this study. Make some subtitles for sections two for clear overview to the readers. Can cite some reference to support some experimental procedures. Clearly explain the characterization techniques. This study is very much simple compared to other studies. Need some critical analysis of the data. There are plenty of literature on biofuel production from biomass. Hence, need minimum novelty to be accepted by this journal. Conclusion is too big. Just mention the critical information. Finally, I hope some critical analysis of the result or mention the innovativeness of the paper. In order to increase the reader’s attention, I also suggest compare their biofuel properties with some other published data.

Therefore, I recommend a major revision.

Author Response

Response to Reviewer 3

Title:  The production of gaseous biofuels using biomass waste from construction sites in Recife - Brazil

Comments:

In this manuscript, authors used biomass waste to produce biofuels. Although the topic has scientific interest but authors fails to explain it properly. Needs more clarifications. Overall manuscript needs further improvement. My specific comments are below:

• Introduction section did not organize well. Need more background information followed by specifically mentioning the novelty of this study.

It was implemented more background information and the originality and novelty of this work was reported on the manuscript.

 

• Make some subtitles for sections two for clear overview to the readers. Can cite some reference to support some experimental procedures.

This suggestion was accepted and implemented on the original manuscript.

 

• Clearly explain the characterization techniques.

This study is very much simple compared to other studies. Need some critical analysis of the data.

It was already included on the paper.

 

• There are plenty of literature on biofuel production from biomass. Hence, need minimum novelty to be accepted by this journal.

The use of agriculture residues and clean wood products can be found extensively in the literature. However, work on biofuel production and feedstock characterization using CCbiowastes and landfill-derived wood are not exploited. Only few researchers have published their work using gasification using challenging feedstocks such as landfill diverted wood (that also includes Ccbiowaste) as reported by Littlejohns et al. (2020). Hence, this manuscript described the use of CCbiowastes as feedstocks for gasification, and this a novelty and original work as it has never been done for residential buildings in Recife-Brazil.

 

• Conclusion is too big. Just mention the critical information.

The conclusions were reduced to a minimum and contain the critical information as required

 

• Finally, I hope some critical analysis of the result or mention the innovativeness of the paper. In order to increase the reader’s attention, I also suggest compare their biofuel properties with some other published data.

 

These comparisons with results found in the literature and the innovativeness were reported on the original paper.

 

 

Thank you for your suggestions and comments. It has improved the quality of the manuscript.

Reviewer 4 Report

Journal Processes (ISSN 2227-9717)

Manuscript ID processes-694079

Title: The production of gaseous biofuels using biomass waste from construction sites in Recife - Brazil

Authors: SERGIO PERES , EDUARDO LOUREIRO , HUMBERTO SANTOS , FABIO VANDERLEI E SILVA , ALEXANDRE GUSMAO

GENERAL COMMENT OF THE MANUSCRIPT

This paper describes the production of gaseous biofuels through a gasification process using biomass residues form construction sites.

From my point of view, the technical quality of this work is very satisfactory and original, although there is some aspect that can be improved. I offer some specific minor comments/suggestions as follows.

SPECIFIC COMMENTS

Comment 1. English spelling. I recommend reviewing the English spelling of the manuscript. For instance:

700, 800 and 900 ºC: page 3 the multi storey residencial building: page 3 The results are shown on Table 1: page 3 Similar results for the ultimate analysis for woody biomass: page 5

 

Comment 2. Introduction. I do not agree with the following sentence: “The low moisture content biomass is more feasible to be use in the thermochemical route, while high moisture content biomass may be used as feedstock for the biological one [2]”. The hydrothermal liquefaction is also a thermochemical process that can used with biomass with high moisture. In fact, I think that this process could be referenced in the introduction section.

Comment 3. Introduction. In my opinion, some references about similar works should be included in the introduction section.

Comment 4. Material and methods. Please, include also the country in the equipments.

Comment 5. Results and discussion. The following sentences can be omitted:

Page-3: In this section, the results were divided in biomass collection and sampling, biomass characterization and gasification, as follows.  

Page-4: The results for the physical, chemical and energetic characterization of the construction biomass residues were as follows.

Comment 5. Results and discussion. Table 6 to 8 are not commented and discussed in the manuscript. From my point of view, the discussion of the results, which are very interesting, can be increased and improved.

Comment 6. Results and discussion. The authors only study the effect of temperature in the gasification process. Why? In my opinion, pressure and reaction time are also important operating conditions.

Author Response

Journal Processes (ISSN 2227-9717)

Manuscript ID processes-694079

Title: The production of gaseous biofuels using biomass waste from construction sites in Recife - Brazil

Authors: SERGIO PERES, EDUARDO LOUREIRO, HUMBERTO SANTOS, FABIO VANDERLEI E SILVA, ALEXANDRE GUSMAO

GENERAL COMMENT OF THE MANUSCRIPT

This paper describes the production of gaseous biofuels through a gasification process using biomass residues form construction sites.

From my point of view, the technical quality of this work is very satisfactory and original, although there is some aspect that can be improved. I offer some specific minor comments/suggestions as follows.

SPECIFIC COMMENTS

Comment 1. English spelling. I recommend reviewing the English spelling of the manuscript. For instance:

700, 800 and 900 ºC: page 3 the multi storey residencial building: page 3 The results are shown on Table 1: page 3 Similar results for the ultimate analysis for woody biomass: page 5

Revision on English spelling was done throughout the paper.

 

Comment 2. Introduction. I do not agree with the following sentence: “The low moisture content biomass is more feasible to be use in the thermochemical route, while high moisture content biomass may be used as feedstock for the biological one [2]”. The hydrothermal liquefaction is also a thermochemical process that can used with biomass with high moisture. In fact, I think that this process could be referenced in the introduction section.

Hydrothermal liquefaction was included in the Introduction section. The sentence that contains “The low moisture contente...” was rephrased.

Comment 3. Introduction. In my opinion, some references about similar works should be included in the introduction section.

The references about similar Works were included in the Introduction section.

Comment 4. Material and methods. Please, include also the country in the equipments.

Comment 5. Results and discussion. The following sentences can be omitted:

Page-3: In this section, the results were divided in biomass collection and sampling, biomass characterization and gasification, as follows.  

Page-4: The results for the physical, chemical and energetic characterization of the construction biomass residues were as follows.

Comment 5. Results and discussion. Table 6 to 8 are not commented and discussed in the manuscript. From my point of view, the discussion of the results, which are very interesting, can be increased and improved.

Comments on the results of Tables 6 to 8, the effect of temperature in gases formation was included. However, Figures 2,3 and 4 illustrated the  heating values and the energy content of the gaseous produced in the gasification processes at diferente temperatures. As the objetive of this paper was to use the Ccbiowastes in electricity, the most importante information in this viewpoint, in the authors opinion, is the energy content of the gases, as it is this energy that will be converted to electricity in the genset. These comments were implemented on the manuscript.

Comment 6. Results and discussion. The authors only study the effect of temperature in the gasification process. Why? In my opinion, pressure and reaction time are also important operating conditions.

Previous Works on the bench scale gasifier at the Fuel and Energy Laboratory of the University of Pernambuco using different reaction times (1,2,3, 4, 5 min), have shown that the pressure become steady at three min of reaction time. Even in increased reaction times, there were no significant changes on the percentage of the gases formed and in their yields. The gasification pressure using this reactor starts at atmospheric pressure. And the pressure is monitored by the pressure gauge. Even the pressure represents an important operational variable, this specific bench gasifier is not pressurized. As, the valves at both ends of the reaction tube are closed when the feedstock is insert in the interior, pressure starts to increase as a consequence of the conversion solid to gas.

Hopefully, this explain the reasons why the experiments were carried out as described on this paper.

 

Thank you very much for your comments. They have improved significantly the quality of the paper.

Round 2

Reviewer 2 Report

Dear Authours,

 

Your manuscript has been improved deeply, but there is some comments which should be addressed before publish. Specific comments in attachment.

Comments for author File: Comments.pdf

Author Response

RESPONSE TO THE REVIEWER 2 COMMENTS:

COMMENT 1:

LINE 277 of the round 2 comments of the reviewer. (page 7 on the new manuscript version).

We have included a deeper explanation on the new version of the manuscript.

The ash content for C&D wood varied from 0.7 to 0.8%, by mass, as received [17]. According to Basu (2010) and Ruiz et al. (2013), thermal gasification typically requires a moisture content of less than 15% [12,19]. Every kilogram of moisture needs about 2,300 kJ of heat to vaporize and an additional 1,500 kJ to be raised to a typical gasifier temperature of 700°C. Therefore, the lower the moisture, the higher the heat available in the product gas [19]. Hence, it is desirable to keep moisture as low as possible to enhance the gaseous product heating value.

Comment 2 of the Reviewer 2:

The material and conditions of the Passos et al. were included.

The LHV results obtained in the CCbiowaste gasification at 700 °C, 800 °C and 900°C, ranged from 8.07 to 10.74 MJ.m^-³. These results were higher than the ones reported by Ruiz et al., Basu and Littlejohns et al. and Martinez et al. that ranged from 4.5 – 6.34 MJ. m^-³ using several types of biomass such as wood chips, spruce, wood pallets, rice husk, sawdust, pine wood blocks, wood waste and construction and demolition biomass in temperatures ranging from 700°C to 1000 °C [12, 18-20]. At this same temperature range, experiments using dried sugarcane bagasse obtained higher heating values ranging from 9.77 to 13.82 MJ. m^-³ [21,22]. Passos et al. showed results of LHV syngas of 8.62 MJ.m^-³, similar to the ones obtained at 700 °C , using construction and demolition waste with 12.7% moisture (by mass) [9]. However, Passos et al. did not mention the temperature that gasification was carried out. As mentioned by Littlejohns et al. there is a lack of experimental studies on CCbiowastes and landfill-diverted wood, what makes the comparison of results with other authors rather difficult, and the same time, shows the originality of this work [17].

Comment 3 – The reference number was added.

Comment 4 -

The comparison of the LHV with other types of biomass and Construction and demolition wood were added just before Figure 2.

 

The comparison on the gaseous fuels yields was added to the paper.  

Comment 5

Table 9 was included on the manuscript. This Table was constructed using values of LHV and gaseous fuels yields generated in the gasification process. The total energy available was calculated by the authors. Hence, a comparison of the Total energy available (TEA) results obtained using CCbiowastes with the ones obtained several types of biomass and wastes could be carried out.

Hopefully, this increased the depth of the discussion on the manuscript.

Comment 6

 

Explanation: As mentioned on the paper, the CCbiowastes are often discarded in landfills and in other inappropriate places. The CCbiowastes are available at the construction’s sites, there is no cost for use them and it is avoided a transportation cost to take them from the site to send to a landfill (that also requires a tipping fee). Other sources of biomass will be purchased, hence the cost of production of electricity will be higher than if the company decides to use the wastes that are available there. Besides, when using the CCbiowastes to electricity, there will be a reduction on the environment impact caused by such wastes. No wastes to discard, no environmental damage and the electricity generated is considered to be carbon neutral.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Editor,

Authors have responded sufficiently to my comments. This paper can now be accepted for publication.

 

Thanks 

Regards

Dr Boshir 

Author Response

Thank you for your acceptance!