Experimental Analysis of Brewers’ Spent Grains Steam Gasification in an Allothermal Batch Reactor

Abstract

In this work, brewers’ spent grains (BSG) were evaluated and studied in order to obtain a combustible gas by means of allothermal steam gasification. BSG were preprocessed in a rotary dryer and a pelletizer prior to gasification in an indirectly heated batch reactor. BSG characterization was conducted by means of proximate, ultimate, and thermogravimetric analysis, allowing us to conclude that BSG have characteristics comparable to those of regular lignocellulosic biomasses. Gasification tests were performed in an allothermal bench-scale batch reactor in order to determine the effect of temperature and steam-to-biomass ratio (S/B) in the produced gas. The produced gas was mainly composed of 22.8–30.2% H2, 15.1–22.3% CO, and 7.2–11.1% CH4, contributing to a heating value of 8.11–9.0 MJ/Nm3 with the higher values found for a low S/B ratio and for high temperatures. The performance of the process was assessed by evaluating the cold gas and carbon conversion efficiencies. These indicators were found to be in the ranges 47.0%–52.1% and 57.0%–62.7%, respectively. The main conclusion of this work is that the produced gas obtained from BSG steam gasification has sufficient quality to open other options to beer producers to use their own brewing wastes to satisfy their energy needs, allowing them to progress toward the circular economy concept.

Experimental and Modeling Analysis of Brewers´ Spent Grains Gasification in a Downdraft Reactor

“…The BSG used in downdraft gasification experiments was characterized in a previous study [13] in terms of ultimate and proximate analysis and heating value. The main results of BSG characterization are shown in Table 1.…”

“…The interest in using lignocellulosic biomass as a renewable resource for bioproducts production is rising, especially due to their abundance, low cost, and their production does not compete with the food chain [7]. Among the lignocellulosic biomasses, spent grain [8] has received increased interest in the last few years [9][10][11][12][13][14].…”

“…From this brief overview of the brewing process, it is possible to verify that the brewer's spent grains (BSG) are the most representative byproduct of the brewing process. The brewing sector in Portugal generates around 135,000 tonnes of BSG per year [13], which are mainly used as animal feed. Nevertheless, recent developments exposed other possible applications such as the production of various value-added bio-products [9][10][11] and energy generation for the brewing process [11][12][13].…”

“…Activation energies of the carbon dioxide reaction also decrease with higher hydrothermal carbonization reaction rates. Ferreira et al [13] performed a very complete characterization of brewers' spent grains and subject it to steam gasification in an allothermal batch reactor. BSG was characterized through proximate, ultimate, and thermogravimetric analysis and a van Krevelen diagram.…”

Evaluation of Spent Grain Biochar Impact on Hop (Humulus lupulus L.) Growth by Multivariate Image Analysis

“…Therefore, in a perspective of a zero waste approach and in order to reduce waste storage and logistics costs, alternatives to valorize these residues and to recover and reuse them in a sustainable and profitable way are continuously proposed and developed. Moreover, by-products can be transformed in combustible gas, to be reused in the beer production cycle, or in soil amendments for agricultural applications [4,5].…”