Waste Biomass Valorisation for the Development of Sustainable Cellulosic Aerogels and their Sound Absorption Properties

Funding Information: This research is part of the CSIC program for the Spanish Recovery, Transformation and Resilience Plan funded by the Recovery and Resilience Facility of the European Union, established by the Regulation (EU) 2020/2094. Grant RTI2018‐094268‐B‐C22 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”. This work was a part of the Academy of Finland's Flagship Programme under Projects No. 318890 and 318891 (Competence Center for Materials Bioeconomy, FinnCERES). Timo Pääkkönen is greatly acknowledged for providing the authors with the brewers’ spent grain and Eero Kontturi is acknowledged for fruitful discussions. Publisher Copyright: © 2022 The Authors. Advanced Sustainable Systems published by Wiley-VCH GmbH.Novel and more sustainable sound absorbing materials are produced through the valorization of waste biomass sources by following circular economy principles. Cellulosic nanocrystals (CNC) were extracted from Posidonia oceanica dead leaves, spent barely grains, and kale stems (KS) using a simplified purification protocol. These nanocrystals are used to prepare cellulosic aerogels, evaluating the effect of three parameters, namely, concentration (0.5–4%), CaCl2 and poly(lactic acid) (PLA) incorporation (hybrid aerogels), on their sound absorption properties. Aerogels from 4% suspensions show the highest sound absorption, outperforming benchmark rockwool and polyester—two modern commonly-used sound absorbers. Moreover, PLA coating also improves the sound absorption performance of the most aerogels. CNC from KS aerogels are selected as the optimum at both high (500–6000 Hz) and low (100–1500 Hz) frequency ranges. Overall, these results represent a new proof-of-concept of waste biomass conversion to high-performance cellulosic aerogels that have excellent sound absorbing properties.Peer reviewe