Feasibility Analysis of Brewers’ Spent Grain for Energy Use: Waste and Experimental Pellets

Abstract

Waste production is increasing every day as a consequence of human activities; thus, its valorization is becoming more important. For this purpose, the usage of wastes as biofuels is one of the most important aspects of sustainable strategies. This is the case of the main waste generated in brewing industries: brewers’ spent grain (BSG). In this sector, microbreweries are not able to properly manage the wastes that they generate due to lack of space. Consequently, the transformation of BSG to a high-quality biofuel might be an interesting option for this kind of small industry. In this work, we carried out a physical-energy characterization of BSG, as well as pellets from this waste. The initial characterization showed slightly unfavorable results concerning N and ash, with values of 3.76% and 3.37% db, respectively. Nevertheless, the physical characterization of the pellets was very good, with acceptable bulk density (662.96 kg·m−3 wb) and low heating value (LHV; 17.65 MJ·kg−1 wb), among others. This situation is very favorable for any of the intended uses (for energy use or animal feed, among others).

The Use of Brewer’s Spent Grain after Beer Production for Energy Purposes

“…The elemental composition of spent grain (carbon—46.8%, hydrogen—7.0%, oxygen—38.7%, nitrogen—0.7%, and sulphur—0.3%) does not meet the standards for fossil fuels [ 19 ]. Similar results of elemental analysis were obtained by other researchers [ 20 , 21 , 22 , 23 ], except for the amount of nitrogen, which was at the level of 3.46–5.45%. The discussed direction of spent grain use may not cover the total demand of the brewery for energy but it may be a stimulus for the introduction of a 100% renewable energy plan in a brewery.…”

“…According to the literature [ 20 , 21 , 34 , 44 ], in the next few years, plant-derived biomass may become one of the main renewable resources of electrical and heat energy, which may result in numerous benefits such as the reduction in greenhouse gas emissions, increase in employment, or reduction in expenditure on fossil fuel exports, e.g., crude oil or natural gas.…”

“…Water content is extremely closely correlated with the calorific value. The higher the content of water in the material, the lower its calorific value [ 20 , 21 , 43 , 44 , 45 ].…”

“…BSG analysed by Bieniek et al [ 23 ] contained lower amounts of fixed carbon—8.85%, and the samples tested by Coronado et al [ 20 ] contained bound carbon at the level of 17.48%. A high content of bound carbon and volatile substances increase the calorific value of all biomass fuels [ 19 , 21 , 33 ].…”

Torrefaction of spruce, beech, and oak pellets in order to improve calorific value

“…The use of pellets in combustion promotes "green energy" and reduces the noxious emissions released into the atmosphere by fossil fuels (Cardozo et al 2014;Arranz et al 2021). Even though the price of wood pellets is double that of briquettes, their major advantages (they are renewable, decrease dependence on fossil fuels, don't degrade during storage, etc.)…”