sustainability Article Life Cycle Assessment of Fungal-Based Composite Bricks Lisa Stelzer 1 , Friederike Hoberg 1, * , Vanessa Bach 2, * , Bertram Schmidt 1 , Sven Pfeiffer 3 , Vera Meyer 1 and Matthias Finkbeiner 2   Citation: Stelzer, L.; Hoberg, F.; Bach, V.; Schmidt, B.; Pfeiffer, S.; Meyer, V.; Finkbeiner, M. Life Cycle Assessment of Fungal-Based Composite Bricks. Sustainability 2021, 13, 11573. https://doi.org/10.3390/su132111573 Academic Editor: Jorge de Brito Received: 8 September 2021 Accepted: 15 October 2021 Published: 20 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 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/). 1 Applied & Molecular Microbiology, Institute of Biotechnology, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany; lisastelzer@gmx.net (L.S.); bertram.schmidt@tu-berlin.de (B.S.); vera.meyer@tu-berlin.de (V.M.) 2 Sustainable Engineering, Institute of EnvironmentalTechnology, Technische Universität Berlin, 10623 Berlin, Germany; matthias.finkbeiner@tu-berlin.de 3 Department of Digital Design Planning and Building, Hochschule Bochum, Am Hochschulcampus 1, 44801 Bochum, Germany; sven.pfeiffer@hs-bochum.de * Correspondence: frie.hoberg@gmx.de (F.H.); vanessa.bach@tu-berlin.de (V.B.); Tel.: +49-160-321-7031 (F.H.); +49-314-27941 (V.B.) Abstract: Fungal-based composites as substitutes for construction materials might represent a promis- ing solution to reduce the environmental burdens of the building industry. Such composites can be produced biotechnologically through the cultivation of multicellular fungi that form dense mycelia whilst growing into and onto residual plant biomass from agriculture and forestry. As comprehensive environmental assessments are missing, this paper conducts a life cycle assessment for fungal-based composite bricks considering the categories of climate change, eutrophication, acidification, smog, water scarcity, and land use. Electricity for sterilization, incubation, and the drying process led to 81.4% of a total 0.494 total kg CO 2 eq. for climate change and 58.7% of a total 9.39 × 10 −4 kg SO 2 eq. for acidification. Further, hemp shives and grain mix were identified as hotspots for eutrophication (77.7% of 6.02 × 10 −4 kg PO 4 −3 eq.) and land use (81.8% of 19.4 kg Pt eq.). However, the use of hemp shives, rapeseed straw, or poplar wood chips did not differ in the environmental impacts. Further, lab-scale production was compared with industrial scale-up, which is mostly characterized by energy efficiency showing reduced impacts for all considered categories, e.g., a decrease of 68% in climate change. Recycling should be included in future studies as well as considering the use and end-of-life phase. Keywords: life cycle assessment; fungal-based composites; composite material; construction material; climate change; architecture; fomes fomentarius 1. Introduction Fungi have been used by mankind in numerous ways since prehistoric times. Com- monly known is their use as food or in food fermentation. Less well-known is that fungi have also long played a role as a source of materials and medicine. The Iceman mummy found at Tisenjoch, also known as “Ötzi”, carried parts of tinder fungus Fomes fomentarius and birch polypore Piptoporus betulina. These fungi were probably used for fire-making and healing purposes [1]. In particular, the tinder fungus was used for thousands of years to obtain tinder. This soft felt-like material served as a spark catcher for fire making. In addition, it was suitable for making textile items. The formerly widespread traditional use of this “felt leather” is kept alive today in some regions, primarily in Eastern Europe, or through innovative product designers, e.g., ZVNDER [2], MYLO [3], or NEFFA [4]. In biotechnology, unicellular and filamentous fungi play a prominent role due to their metabolic versatility and robustness and are therefore harnessed by different industries including pharma, chemical, food, feed, biofuel, and textile industries to produce drugs, Sustainability 2021, 13, 11573. https://doi.org/10.3390/su132111573 https://www.mdpi.com/journal/sustainability