Biobased Insulation Materials Cut Carbon Footprint

By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Aug 15 2024

A recent review article published in the Journal of Cleaner Production examined the key physical and environmental characteristics of biobased insulation materials, evaluating their potential for climate mitigation. The review assessed these biobased products based on their thermal performance, climate impact, and overall environmental sustainability.

Background

Insulation materials play a key role in the construction industry by enhancing the thermal performance of buildings, which helps to reduce energy consumption and carbon emissions. As the sector shifts towards sustainability, there is a growing adoption of biobased insulation materials, which are derived from renewable and eco-friendly sources, replacing traditional mineral and plastic-based insulations.

While the physical and environmental properties of biobased insulation materials have been reviewed, comparing their effectiveness in climate mitigation against conventional materials remains challenging due to inconsistent environmental data and methodologies.

To address this, the literature review mapped the key physical and environmental properties of biobased insulation materials to evaluate their climate mitigation potential. The review established specific definitions and categorization criteria for emerging biobased insulation materials and products developed up to August 2023. It also calculated the embodied energy (EE) and carbon (EC) of these materials within the European context.

Definitions and Mapping of Biobased Materials

Functionally, biobased insulation materials are defined as thermal insulation products derived from plant and animal biomass. In the United States, the BioPreferred Program requires a minimum of 25 % biobased content for a product to be certified as biobased. However, this criterion does not address the materials’ potential for climate mitigation through greenhouse gas reduction.

The current use of thermal conductivity as a performance benchmark is problematic. The International Organization for Standardization (ISO) specifies a maximum thermal conductivity of 0.065 W/Km for commercial insulation materials, a standard that may not fully reflect climate mitigation potential. For example, this criterion excludes emerging biobased materials like hempcrete, which has a low global warming potential.

Biocomposites and bio-reinforced composites are hybrid bio-insulation materials made from two or more components. Bio-reinforced composites are further categorized into hybrid composites, which use multiple types of fibers, and green or sustainable composites, which combine natural-origin matrix resins, fibers, and other materials.

This review mapped 174 products, which included 39 types of biobased materials. Of these, 22 were non-composite materials that did not use binders, while the remaining 152 were composite materials. Within the composites, polymer, biopolymer, and mineral-based materials were the most common, with only seven products utilizing alternative binders.

Significant variation was observed in the EE and EC of these materials, similar to the variation in thermal conductivity. The lowest EE recorded was zero, while the highest exceeded 100,000 MJ. EC values ranged from -250 to over 300,000 kg CO₂-equivalent. Notably, materials such as flax, rice, hemp, wheat, and wood, which use less energy-intensive binders like lime, molasses, alginate, and clay instead of polymer resins, might offer better EE performance compared to the best-performing glass wool.

Categorization of Biobased Materials/Products

Principal component analysis (PCA) was conducted on a dataset of 134 materials with six attributes to identify the key components capturing over 80 % of the variance. The analysis revealed that mineral composite materials generally have a long lifespan and high thermal conductivity but a low proportion of biomaterials and waste. Conversely, non-composite materials, with few exceptions, showed better thermal resistance.

Mineral composites exhibited excellent thermal performance due to their extended lifespans compared to non-composites, biopolymer composites, and polymer composites. However, they also had high EE and EC values. On the other hand, materials selected for climate mitigation were less energy- and carbon-intensive, spanning various material groups, except for the energy-intensive polymer composites, which showed diverse physical properties.

None of the reviewed products met all three criteria of thermal performance, climate mitigation, and environmental sustainability. There was no overlap between products focused on performance and those aimed at climate mitigation. This indicates that choosing the optimal biobased insulation material involves trade-offs between thermal performance (such as thermal conductivity and lifespan) and climate mitigation (EE and EC).

Although climate-oriented products did not achieve optimal performance, they often offered benefits like a long lifespan or low thermal conductivity. When selecting the best insulation materials, prioritizing low thermal conductivity over a long lifespan may be more advantageous for overall effectiveness.

Conclusion and Future Prospects

Overall, the researchers provided a critical review and comprehensive categorization of biobased insulation materials, highlighting their potential to significantly decarbonize the construction sector. Many of the materials evaluated showed strong performance in cradle-to-gate EC due to the carbon storage capacity of biomaterials.

Cellulose and straw bales emerged as particularly promising options for both thermal performance and environmental sustainability, with notable potential for large-scale application. However, the physical and environmental performance of many biobased products showed considerable variability. Consequently, lab-developed biobased products need improvements in EE and thermal conductivity to match or surpass the performance of traditional materials like glass wool.

While biobased insulation materials hold promise for reducing the carbon footprint of building insulation, the researchers also cautioned about potential future risks. Large-scale adoption of biobased materials might lead to unintended environmental impacts, such as increased waste incineration and landfilling, highlighting the need for careful consideration of these factors in the transition towards more sustainable building practices.

Journal Reference

Lu, Z. et al. (2024). Climate Mitigation Potential of Biobased Insulation Materials: A Comprehensive Review and Categorization. Journal of Cleaner Production, 143356. DOI: 10.1016/j.jclepro.2024.143356, https://www.sciencedirect.com/science/article/pii/S095965262402805

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