Abstract
The main challenge of this work is to identify a novel approach to reuse and valorize brewers’ spent grain (BSG) to produce a new source of income for the brewers in terms of self-consumption or selling goods. Therefore, this study explored the composting behavior of BSG mixed with different organic materials: wheat straw with pig slurry solid fraction and wheat straw with sheep manure, MIX1 and MIX2, respectively. The composting process was carried out in bins by comparing two different composting strategies: manual turning (MT) and static composting xxx– without turning operations (ST). During the experimental trial, BSG mixtures were chemically analyzed for pH, total Kjeldahl nitrogen, ammoniacal nitrogen, nitrate-nitrogen, total organic carbon, volatile solids, carbon to nitrogen ratio, and moisture content. Furthermore, the final composted materials were evaluated according to the physicochemical and biological limits fixed by the European regulation (2019/1009) and the Italian law (D.Lgs 75/2010). At the end of the composting process, the C/N ratio ranged from 11.6 to 15.5, the humification ratio ranged from 12.4 to 13.8 and the NH4+-N/NO3−-N ratio was lower than 0.5 indicating, in all investigated treatments, a good degree of maturation. However, as evidenced by the high pH values and low Germination Index, the sheep manure, as starting material, proved less effective than the solid fraction of pig slurry, probably due to excessive trampling and slow litter change. Finally, concerning the two composting strategies investigated, the obtained results highlighted that the composting strategy did not affect the final compost quality.
Highlights
The brewery industry produces large quantities of by-products, typically spent hops, yeast, and spent grain
This study explored the composting behavior of brewers’ spent grain (BSG) mixed with different organic materials: wheat straw with pig slurry solid fraction and wheat straw with sheep manure, MIX1 and MIX2, respectively
Several authors [45,48,49,50,51,52] reported that temperatures above 55 ◦C for three or five consecutive days are requested for the correct sanitation of the composting mixtures
Summary
The brewery industry produces large quantities of by-products, typically spent hops, yeast, and spent grain. Brewers’ spent grain (BSG) represents 85% of total by-products generated in the brewing process and 20% for a liter of beer produced (20 kg hL−1 beer) [1]. The worldwide annual production of brewers’ spent grain ranged from 38 to 39 million tons [3], with 3.4 million tons in the European Union [4]. Nowadays the main way of recycling BSG is represented by livestock feed production, due to its high content in fiber, un-degradable protein, and water-soluble vitamins [5,6,7,8]. The high protein content of BSG combined with its high moisture content and fermentable sugar content makes it susceptible to microbial growth and subsequent spoilage over short periods of time, from 7 to 10 days [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
