Fungal Mycelium Bio-Composite Acts as a CO₂-Sink Building Material with Low Embodied Energy

As part of the global transformation to a circular economy, modern society faces the challenge of developing sustainable building materials that do not deplete nonrenewable resources or generate environmentally destructive waste. Bio-composites based on fungal mycelium grown on agricultural waste streams have the potential to serve this purpose, reducing the ecological impact of the construction industry and the conventional materials on which it currently relies. In addition to the possible advantages in the production and postuse phases of their life cycle, mycelium bio-composites are lightweight and highly insulating, thus providing valuable thermal properties for reducing energy consumption and emissions over the operational lifespan of the building. In this study, a comprehensive life cycle assessment of mycelium bio-composites was conducted, focusing on the embodied energy (EE) and embodied carbon (EC). Part of the CO₂that is emitted is the result of the fungal growth. Therefore, a novel calculation method was developed to assess the metabolic carbon emissions as a function of weight loss during the growth period. Using a cradle-to-gate model of the production process, the EE of the mycelium bio-composite was estimated to be 860 MJ m^-3, which represents a 1.5- to 6-fold reduction compared with that of the common construction materials. The EC was calculated to be -39.5 kg CO₂eq m^-3, its negative value indicating that the fungal bio-composite effectively functions as a CO₂sink, in contrast to currently used construction materials that have a positive EC. The incubation stage of mycelium bio-composite production made up the largest portion (73%) of the overall energy, while metabolic CO₂comprised a significant proportion (21%) of the overall emissions as well. Altogether, our results demonstrate that using bio-composite building materials based on fungal mycelium and local plant residues can provide a sustainable alternative to current practice.