Life Cycle Assessment of Fungal-Based Composite Bricks

Round 1

Reviewer 1 Report

The paper is on a very interesting and rare topic. It is related to current problems as protection of environment and biomaterials.

The experiment is well described. The results, discussion and conclusions are adequate to the topic. 

Author Response

Dear reviewer, thanks for the positive feedback on our submitted manuscript.

Based on your provided feedback, we did not carry out any changes as it seems you were pleased with the manuscript as it is in its current form. However, a few additions were made based on the comments of the other reviewers.

Reviewer 2 Report

The presented manuscript deals with an interesting topic related to the possibility of using new materials in construction such as fungal-based composite. The main aim of research was to identify potential environmental impacts of fungal-based bricks.

Life cycle assessment analysis has been limited to study from cradle to gate. This study certainly contains lot of new researches and information based on conducted experiment.

Nevertheless, I have a few comments on the article:

 

Is it possible to use fungi in live form in self-growing construction or combined with nanoparticles and polymers to make mycelium-based electronics.

 

In my opinion, the up-scaling of fungal-based bricks production on an industrial scale is too general. What is the production efficiency assumed for the industrial scale? The differences in Figure 5 show only the percentage changes after applying the energy index you specified.

For production on an industrial scale, should be also take into account energy losses resulting from the cubature of the building in which the fungal-based bricks would be produced? Such a building, depending on its size, would generate energy losses needed to maintain a relatively constant temperature inside it throughout the year, which should also be included in the LCA analysis.

Does the analysis include the energy consumption needed to produce the individual ingredients necessary for the cultivation of fungal-based bricks, such as, for example, gypsum?

Fig 4. The font size should be standardized in all figures, especially in figure 4, the fonts should be enlarged

Formula 1- no description of parameters

I did not find a reference to item 13 in the work: IEA and UNEP 2019 Global Status Report for Buildings and Construction; 2019; Vol. 224; ISBN 9789280737684.

Author Response

Dear reviewer, thanks for the feedback on our submitted manuscript.

Please see document attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have presented a LCA study of fungal based bricks. While acknowledging the importance and the novelty of the work presented, the following comments should be carefully addressed prior making the manuscript applicable for publication. 

(1) The manuscript doesn't explain the system boundary, functional unit objectives which are relevant for a typical LCA study. Please refer to ISO14040 and ISO14044 for more details and update the content accordingly.

(2) Usual practice in LCA is to compare the results with an a current application to understand the magnitude of saving. Therefore it is recommended to use a virgin product for comparison

(3) The impact assessment methodology is not very clear. Did you use any weighting method? How did the normalisation and characterisation of the results happen? Please explain in detail 

Thank you and good luck with your final submission. 

Author Response

Dear reviewer, thank you for your comments. We changed the manuscript accordingly and provided the revised manuscript with track change to better identify the changes we made. For details regarding your comments, please see the following explanations:

Comment	Answer
(1) The manuscript doesn't explain the system boundary, functional unit objectives which are relevant for a typical LCA study. Please refer to ISO14040 and ISO14044 for more details and update the content accordingly.	Thanks for the comment. We added additional information on the system boundary, cut-off, and used data. The functional unit was already defined in line 88+89.   Lines 95-107 The intended application of this LCA is to determine the environmental hotspots of the lab-scale production of fungal-based bricks. Within the discussion section (4.3) the fungal-based composite brick are further compared with conventionally used bricks in construction to estimate possible reduction potentials. A " cradle to gate" study is carried out to cover the production process setting the system boundaries to include all unit processes from cradle to gate as shown in Figure 2. The use phase and the end of the life phase are not considered. In the following, the studied product system is defined in detail. The included processes are shown in the flow diagram in Figure 2. The data of this foreground system were selected on site (laboratory) via measurements of e.g. electricity of equipment. Missing data were determined via literature research and by the use of databases. The used equipment was not included in the modeling. Further, a cut-off of 5% was defined. Applied data and corresponding modeling assumptions including allocation procedures are explained in section 2.2.
(2) Usual practice in LCA is to compare the results with an a current application to understand the magnitude of saving. Therefore it is recommended to use a virgin product for comparison	Thanks for this comment. This comparison has been done in section 4.3 (Comparison with other functional units/bricks used in construction). We included it in the discussion part because this comparison is currently still challenging as the functional equivalency has not been fully proven. Please see lines 373-385. To highlight that this comparison has been carried out, we added a sentence to the method part:   line 97-98: Within the discussion section (4.3) the fungal-based composite brick are further compared with conventionally used bricks in construction to estimate possible reduction potentials.
(3) The impact assessment methodology is not very clear. Did you use any weighting method? How did the normalisation and characterisation of the results happen? Please explain in detail	Thanks for the comment. We did not apply any normalization and/or weighting approach. This detail was missing from the paper and has been added:   Line 161: No normalization and weighting method was applied.   With regard to the applied characterization methods, we would like to refer to lines 155-160, where we addressed the used methods. As we did not develop any of these methods, but only applied them, we would like to refer to the associated publications. For a better understanding of the characterization methods, we included the category indicator as well as the applied method in Table 1.