More than just a beer - Brewers' spent grain, spent hops, and spent yeast as potential functional fillers for polymer composites

Aleksander Hejna; Mateusz Barczewski; Paulina Kosmela; Joanna Aniśko; Joanna Szulc; Katarzyna Skórczewska; Adam Piasecki; Tairong Kuang

doi:10.1016/j.wasman.2024.03.023

More than just a beer - Brewers' spent grain, spent hops, and spent yeast as potential functional fillers for polymer composites

Waste Manag. 2024 May 15:180:23-35. doi: 10.1016/j.wasman.2024.03.023. Epub 2024 Mar 19.

Authors

Aleksander Hejna¹, Mateusz Barczewski², Paulina Kosmela³, Joanna Aniśko², Joanna Szulc⁴, Katarzyna Skórczewska⁵, Adam Piasecki⁶, Tairong Kuang⁷

Affiliations

¹ Institute of Materials Technology, Poznan University of Technology, Piotrowo 3, 61-138 Poznań, Poland; Department of Polymer Technology, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland. Electronic address: aleksander.hejna@put.poznan.pl.
² Institute of Materials Technology, Poznan University of Technology, Piotrowo 3, 61-138 Poznań, Poland.
³ Department of Polymer Technology, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland.
⁴ Department of Food Industry Technology and Engineering, Bydgoszcz University of Science and Technology, Seminaryjna 3, 85-326 Bydgoszcz, Poland.
⁵ Department of Polymer Technology, Bydgoszcz University of Science and Technology, Seminaryjna 3, 85-326 Bydgoszcz, Poland.
⁶ Institute of Materials Engineering, Poznan University of Technology, Jana Pawła II 24, 61-138 Poznań, Poland.
⁷ Zhejiang Key Laboratory of Plastic Modification and Processing Technology, College of Material Science and Engineering, Zhejiang University of Technology, Hangzhou 310014, China.

PMID: 38503031
DOI: 10.1016/j.wasman.2024.03.023

Abstract

Beer is among the most popular beverages in the world, with the production distributed uniformly between the biggest continents, so the utilization of brewing by-products is essential on a global scale. Among their potential recipients, the plastics industry offers extensive range of potential products. Herein, the presented study investigated the application of currently underutilized solid brewing by-products (brewers' spent grain, spent hops, spent yeast) as fillers for highly-filled poly(ε-caprolactone)-based composites, providing the first direct connection between spent hops or spent yeast and the polymer composites. Comprehensive by-product characterization revealed differences in chemical composition. The elemental C:O ratio, protein content, and Trolox equivalent antioxidant capacity varied from 1.40 to 1.89, 12.9 to 32.4 wt%, and 2.41 to 10.24 mg/g, respectively, which was mirrored in the composites' structure and performance. Morphological analysis pointed to the composition-driven hydrophilicity gap limiting interfacial adhesion for high shares of brewers' spent grain and spent hops, due to high hydrophilicity induced by carbohydrate content. Phytochemicals and other components of applied by-products stimulated composites' oxidative resistance, shifting oxidation onset temperature from 261 °C for matrix over 360 °C for high spent yeast shares. Simultaneously, spent yeast also provided compatibilizing effects for poly(ε-caprolactone)-based composites, reducing complex viscosity compared to other fillers and indicating its highest affinity to poly(ε-caprolactone)due to the lowest hydrophilicity gap. The presented results indicate that the proper selection of brewing by-products and adjustment of their shares creates an exciting possibility of engineering composites' structure and performance, which can be transferred to other polymers differing with hydrophilicity.

Keywords: Brewers' spent grain; Brewery waste; Poly(ε-caprolactone); Recycling; Spent hops; Spent yeast.

MeSH terms

Beer
Carbohydrates / analysis
Edible Grain / chemistry
Humulus*
Polymers
Saccharomyces cerevisiae*

Substances

Polymers
Carbohydrates