# Turning Disposed into Disposable—Development of Single-Use Products from Underutilized Brewery Wastes

## TL;DR

This paper presents a sustainable solution to repurpose brewery waste into disposable products like plates, using spent yeast and spent grain with a vegetable oil coating.

## Contribution

The novel use of untreated or minimally treated spent yeast as a binder for spent grain-based products is a key innovation.

## Key findings

- The final product achieved a flexural modulus exceeding 1 GPa and flexural strength over 6 MPa.
- A vegetable oil coating improved moisture resistance, increasing the water contact angle from <50° to >80°.
- Disposable plates were successfully manufactured, showing potential for industrial application after meeting food-contact criteria.

## Abstract

Although the market recently shifted toward low- or non-alcoholic drinks, the beer sector is an important branch of industry in Europe. It stimulates local economies and communities, thereby justifying the need for its development. Both economic and environmental benefits could be achieved through proper management of the generated by-products, enabling them to stay in a loop. Such an approach aligns with currently postulated sustainability-oriented trends. Herein, a solution for the simultaneous management of the two main by-products of beer production is described. The spent yeast (SY) was used as a potential binder for brewers’ spent grain (BSG)-based products, representing a highly innovative solution given the state of the art. Using SY without treatment or with minimal addition of common organic acids (citric, succinic, and tartaric) enabled efficient bonding of the final product. It yielded properties similar to those of commercial counterparts, with a flexural modulus exceeding 1 GPa and a flexural strength exceeding 6 MPa. Because of the nature of the applied raw materials and their inherent moisture sensitivity (water contact angle < 50°), the final product was coated with vegetable oil. The applied coating, after thermooxidation-induced crosslinking, protected against moisture and humidity (water contact angle > 80°), potentially broadening its application range. The application potential was confirmed from a technical point of view through the efficient manufacturing of disposable plates. Nevertheless, their implementation in industrial practice must be preceded by meeting proper criteria for food-contact materials related to the stability and odor of the plates and coatings and migration of their components into food products.