Activated carbon from pyrolysis of brewer’s spent grain: Production and adsorption properties

Abstract

Brewer's spent grain is a low cost residue generated by the brewing industry. Its chemical composition (high nitrogen content 4.35 wt.%, fibres, etc.) makes it very useful for the production of added value in situ nitrogenised activated carbon. The composition of brewer's spent grain revealed high amounts of cellulose (20.8 wt.%), hemicellulose (48.78 wt.%) and lignin (11.3 wt.%). The fat, ethanol extractives and ash accounted for 8.17 wt.%, 4.7 wt.% and 3.2 wt.%, respectively. Different activated carbons were produced in a lab-scale pyrolysis/activation reactor by applying several heat and steam activation profiles on brewer's spent grain. Activated carbon yields from 16.1 to 23.6 wt.% with high N-contents (> 2 wt.%) were obtained. The efficiency of the prepared activated carbons for phenol adsorption was studied as a function of different parameters: pH, contact time and carbon dosage relative to two commercial activated carbons. The equilibrium isotherms were described by the non-linear Langmuir and Freundlich models, and the kinetic results were fitted using the pseudo-first-order model and the pseudo-second-order model. The feasibility of an activated carbon production facility (onsite and offsite) that processes brewer's spent grain for different input feeds is evaluated based on a techno-economic model for estimating the net present value. Even though the model assumptions start from a rather pessimistic scenario, encouraging results for a profitable production of activated carbon using brewer's spent grain are obtained.

Thermo-kinetic, spectroscopic study of brewer’s spent grains and characterisation of their pyrolysis products

“…For example, the N content for the BSG (3.48%) was comparable to the one found in literature with an estimated protein content of 22% [7]. The BSG could therefore serve as a feedstock for the production of an in situ nitrogenised activated biocarbon [1]. The CH 2 Cl 2 extractives content for the BSG in this study was a third of that in the literature [7].…”

“…Furthermore, the high moisture content associated with wet BSG makes it highly susceptible to microbial activity; jeopardising storage and escalating transportation cost. From the foregoing, the continuous generation of BSG has raised significant environmental and economic concerns; thus necessitating the search for alternative uses [1,3,6]. Being a lignocellulosic material, composed of an intricate matrix of cellulose and hemicellulose polysaccharides, lignin and extractives, it could be an ideal feedstock for thermochemical conversion and other valorisation processes [6][7][8].…”

“…As these grains undergo the beneficiation processes, one of the agro-industrial residues often generated are the brewer's spent grains (BSG). The BSG represents about 85% of the total by-product of the brewing process with an annual global production of 30 × 10 6 tonnes [1]. According to Deconinck et al [2] and Mussatto et al [3] an estimate of 0.14-0.20 kg of wet BSG (20-25 wt% dry matter) is generated for every 1 L of beer.…”

Lignocellulosic Materials as Dye Adsorbents: Adsorption of Methylene Blue and Congo Red on Brewers’ Spent Grain

“…So far BSG was mostly used as feed or has been landfilled, and its exploitation as a valuable renewable resource has been neglected. [25] However, different investigations were conducted in order to evaluate BSG as an adsorbent for the removal of synthetic dyes, namely acid dyes -green, yellow, blue and orange 7, [20,26,27] Basic Blue 41, Reactive Black 5, and Acid Black 1, [28] malachite green, [15] methylene blue, [19] and Congo red. [29] Methylene blue (MB) is a cationic (basic) dye most commonly used for cotton, silk and leather dyeing.…”

Evaluation of brewers’ spent grain as a novel media for yeast growth

“…The majority of the produced BSG is currently disposed in landfills or used as feed for animals such as cattle, pig and chicken (Mussatto et al 2006). Other alternative uses include energy production, through direct combustion or biogas (Čater et al 2015), bioethanol production (Liguori et al 2015), for charcoal (Zhang et al 2015), activated carbon production (Mussatto et al 2010; Vanreppelen et al 2014), paper manufacturing (Russ et al 2005; Sousa et al 2007), as a brick component (Russ et al 2005), to grow mushroom on (Beharry 2015) and composting for agriculture to be used as fertilizer (Beharry 2015). …”