Low-Carbon Bio-Concretes with Wood, Bamboo, and Rice Husk Aggregates: Life Cycle Assessment for Sustainable Wall Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presented is very interesting because its main topic is the replacement of ceramic cement material with cement composite material with wood, rice husk, and bamboo aggregates. It presents calculations on the carbon footprint, calculation of the energy that would be necessary for preparation and transportation, but the limitation of the use of these materials is restricted by aspects of integrity and mechanical stress, which is why it is requested that it have results of mechanical tests.

The analyses presented on performance and durability presented in lines 574 to 587 are supported only by bibliography and not by experimental results, and these properties are very relevant for the use of these new materials. It is suggested to complete the mechanical tests for the 3 composite materials to complete the study, they would be resistance to compression and resistance to environmental conditions such as humidity and UV rays, very relevant.

Comments on the Quality of English Language

English is presented fluently and correctly. I have no qualms about it.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors assessed the carbon footprint of three bio-concretes, computer wood-based configuration (WBC), bamboo agglomerated bio-concrete (BBC), and rice husk-based bio-concrete (RHBC) for their possible application as sustainable wall systems. The study based on Life Cycle Assessment (LCA) revealed that WBC and BBC were low or negative in carbon emissions, whereas RHBC had some modest reductions in emissions. The application of these bio-concretes resulted in up to 32 percent reduction of greenhouse gas emissions in masonry blocks and 107 percent in light-framing systems as compared with conventional materials. This said study underlines durability and availability of localized biomass as prerequisites for scaling bio-concretes and indicates great potential for mitigation of climate change within the paradigms of a circular economy.

 

The abstract states that bio-concretes achieved a significantly low or negative carbon footprint. Would it be possible to specify actually how low or negative that is compared to the conventional concretes for better context in the abstract?

 

The introduction makes some references to the goals of the Paris Agreement but does not really link the study to those goals. Could you, therefore, clarify how your findings directly support the achievement of these climate goals, e.g. CO2 reductions quantified in terms of the construction sector? Could you also clarify why bamboo, wood, and rice husk were selected against other biomass like hemp, especially with the restrictions against hemp in Brazil? 

 

Could you first explain the fact where the water content for RHBC is higher than WBC and BBC in Table 1? Can this even affect the hydration process or the mechanical properties of RHBC? The biogenic carbon sensitivity analysis considers "best", "intermediate," and "worst" scenarios. Can you give some more details about why these scenarios were chosen and how they correlate with biomass use in the real world? As for Transport distance analysis, the intermediate scenario assumes that the suppliers are located very close to Rio de Janeiro. What is the level of realism of those assumptions in terms of possible future widespread adoption in different Brazilian regions?

 

According to Figure 4, WBC and BBC exhibit a negative carbon footprint at 50% biomass, while RHBC does not. Is this because the lesser density and carbon content of rice husk are not favouring it in an overall way, or are there any applications where RHBC might still be advantageous? 

 

For Figure 7, bio-concretes could bring masonry block emissions reduction up to 32%. However, the text does not say anything about its costs. Would including cost comparisons with ordinary materials strengthen the argument related to its practical feasibility?

 

Different type of natural aggregate can be mentioned in the paper using followings: 

Composition Component Influence on Concrete Properties with the Additive of Rubber Tree Seed Shells; Normal-Weight Concrete with Improved Stress–Strain Characteristics Reinforced with Dispersed Coconut Fibers; Performance Assessment of a Novel Green Concrete Using Coffee Grounds Biochar Waste; Properties and Structure of Functional Concrete Mixtures Modified with River Shell Powder

 

It is possible to capture passive hygrothermal regulation potentials via bio-concretes. Define this benefit in absolute terms, and you could say what temperature or humidity levels are achieved with this kind of bio-concrete in a controlled environment. Mention that the paper refers to layered coatings or architectural designs to increase bio-concrete durability. Can you mention these such solutions or further reference works that have studied them?

 

Figure 6-the period of carbon storage must extend to as much as 100 years. Will it be possible to get more specific on realistic design interventions to this end within Brazilian construction? Table 5 deals with transport distances, although not with rural or inaccessible areas. Can you make suggestions towards minimizing emissions from such areas? 

 

According to the conclusion, the reductions obtained show that GHG emissions for light-framing scenarios could account for as high as 107%. According to this, does it include only direct emissions or indirect benefits, such as minimized energy for climate control in buildings?

 

This study models the life cycle assessment (LCA), using Simapro v.9.4. Can you confirm that the datasets used for Brazilian conditions like Ecoinvent v.3.8 are the newest update of local realities? Discuss the potential of the mentioned boards-in-industrialized scenarios-BBC and RHBC-for upscaling in city situations where lightweight solutions are preferred.

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf