Evaluation of Brewers Spent Grain as a Sole Substrate for Vermicompost Production within a Circular Economy Framework

Abstract

Brewer's spent grain (BSG) is the main by-product generated during craft beer production and is an environmental challenge when not properly processed. The present study evaluates the suitability of BSG as the sole added organic substrate (over a common-soil base) for vermicomposting processes using Eisenia fetida. The aim is to analyze its potential for humus production within a circular economy framework. A completely randomized 3x3 factorial design was employed, with the amount of BSG and the initial worm density serving as the factors under consideration. The humus obtained was characterized through the determination of humic and fulvic acid carbon. Only the results for fulvic acid carbon showed statistically significant differences among the treatments (p < 0.05). However, after performing the Tukey HSD test, it was determined that all means belonged to the same statistical group. The correlation between the amount of BSG and humic substances was strongly positive. The findings demonstrate that BSG can be efficiently valorized through vermicomposting, constituting a sustainable alternative for waste management in craft breweries.