**1. Introduction**

As a consequence of its current linear economic model of "produce, use, and discard", the construction industry is a significant contributor to global greenhouse gas emissions, destruction of natural habitat and production of industrial waste [1,2]. The industry's reliance on a select few non-renewable materials, such as concrete and steel, puts environmental pressure on finite natural resources, which could eventually lead to their permanent depletion [3]. While the industry is increasingly shifting towards more renewable building materials, the long-term environmental impact of this accelerating growth in demand and rate of regeneration remains to be seen. This shift is spearheaded by mass engineered timber (MET) and engineered bamboo composite (EBC) that depend on additional natural resources such as soil and water, which consequently experience increases in demand [4]. The transition from extracting non-renewable resources to harvesting renewable ones alone

**Citation:** Bitting, S.; Derme, T.; Lee, J.; Van Mele, T.; Dillenburger, B.; Block, P. Challenges and Opportunities in Scaling up Architectural Applications of Mycelium-Based Materials with Digital Fabrication. *Biomimetics* **2022**, *7*, 44. https://doi.org/10.3390/ biomimetics7020044

Academic Editors: Andrew Adamatzky, Han A.B. Wösten and Phil Ayres

Received: 15 March 2022 Accepted: 31 March 2022 Published: 14 April 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

does not necessarily guarantee that the resultant material has a fully circular life cycle. For example, synthetic adhesives are fundamental for the production of MET and alternative bio-based solutions still largely rely on the usage of chemicals. This hinders the commercialisation of fully sustainable, circular wood products, which in turn impedes a transition to more circular and environmentally conscientious material sourcing [5].

Similar trends can be observed with the emergence of bio-resins and bio-plastics. These serve as alternatives to their more traditional, petroleum-based counterparts. However, the production of these alternatives typically relies on a single commodity feedstock, such as corn or sugarcane. This causes a rise in demand for these feedstocks for industrial use, creating competition with existing stock for food supply and instigating complex socioeconomic policy problems [6]. There are similar consequences for the rapidly growing demand for MET, which have the potential to intensify the current volume and rate of deforestation across the world. While this rising demand can be potentially addressed with a fast-growing and high-yield material such as bamboo in certain contexts, hardwoods such as oak that are used for the production of most commercially available MET have the highest potential for contributing to further deforestation [7]. Therefore, there is a considerable need to find new alternative materials that are not just naturally cultivated and harvested, but also produced with processes that repurpose waste streams and improve the reusability and recyclability at the end of their life cycle.
