Lignin from Brewers’ Spent Grain: Structural and Thermal Evaluations

Abstract

Lignocellulose is a renewable ubiquitous material that comprises cellulose, hemicellulose, and lignin. Lignin has been isolated from different lignocellulosic biomass via chemical treatments, but there has been little or no investigation carried out on the processing of lignin from brewers’ spent grain (BSG) to the best of authors’ knowledge. This material makes up 85% of the brewery industry’s byproducts. Its high moisture content hastens its deterioration, which has posed a huge challenge to its preservation and transportation; this eventually causes environmental pollution. One of the methods of solving this environmental menace is the extraction of lignin as a precursor for carbon fiber production from this waste. This study considers the viability of sourcing lignin from BSG with the use of acid solutions at 100 °C. Structural and thermal analyses were carried out on extracted samples, and the results were compared with other biomass-soured lignin to assess the proficiency of this isolation technique. Wet BSG sourced from Nigeria Breweries (NB), Lagos, was washed and sun-dried for 7 days. Tetraoxosulphate (VI) (H2SO4), hydrochloric (HCl), and acetic acid, each of 10 M, were individually reacted with dried BSG at 100 °C for 3 h and designated as H2, HC, and AC lignin. The residue (lignin) was washed and dried for analysis. Wavenumber shift values from Fourier transform infrared spectroscopy (FTIR) show that intra- and intermolecular OH interactions in H2 lignin are the strongest and possess the highest magnitude of hydrogen-bond enthalpy (5.73 kCal/mol). The thermogravimetric analysis (TGA) results show that a higher lignin yield can be achieved when it is isolated from BSG, as 82.9, 79.3, and 70.2% were realized for H2, HC, and AC lignin. The highest size of ordered domains (0.0299 nm) displayed by H2 lignin from X-ray diffraction (XRD) informs that it has the greatest potential of forming nanofibers via electrospinning. The enthalpy of reaction values of 133.3, 126.6, and 114.1 J/g recorded for H2, HC, and AC lignin, respectively, from differential scanning calorimetry (DSC) results affirm that H2 lignin is the most thermally stable with the highest glass transition temperature (Tg = 107 °C).

The Potential Valorization of Corn Stalks by Alkaline Sequential Fractionation to Obtain Papermaking Fibers, Hemicelluloses, and Lignin—A Comprehensive Mass Balance Approach

“…In this study, the structural features in lignin and hemicellulose samples were analyzed by FTIR spectroscopy. A complete description of the main absorption bands of hemicellulose and lignin is given in Table 6 for lignin samples [ 84 , 85 , 86 , 87 , 88 , 89 , 90 ] and Table 7 for hemicelluloses [ 84 , 85 , 90 , 91 ].…”

“…In this study, the structural features in lignin and hemicellulose samples were analyzed by FTIR spectroscopy. A complete description of the main absorption bands of hemicellulose and lignin is given in Table 6 for lignin samples [84][85][86][87][88][89][90] and Table 7 for hemicelluloses [84,85,90,91]. The FTIR spectra of lignin and hemicellulose samples are presented in Figures S6 and S7, respectively, in the Supplementary Materials.…”

Lignins as Promising Renewable Biopolymers and Bioactive Compounds for High-Performance Materials

“…Differences in molecular structure are also found in lignins resulting/extracted from different sources (plant family and species, their culture conditions, part of plant, age, climate, etc.) and extraction procedures [58,59], as evidenced for kraft lignin and lignosulfonates in Figure 2. They can contain different amounts of carboxyl, carbonyl, phenolic, and aliphatic hydroxyl groups.…”

Extracción Secuencial De Fracciones Ricas en Polisacáridos Y Proteínas a Partir De Bagazo De Cebada

“…En la BSG-C (Figura 1 D) se ubican las bandas relacionadas con la vibración de los enlaces O-H entre 3600 y 3200 cm -1 , a 898 cm -1 se observa la vibración del grupo C1-H y el pico a 894 cm -1 se relaciona con la vibración oscilante de C-H propio de la celulosa (Liang et al, 2023). Finalmente, en la fracción BGS-L (Figura 1E) se observan bandas características de OH presente en los alcoholes entre 3664 y 3326 cm -1 , las bandas a 2915 cm -1 y 2851 cm -1 se asocian estiramiento de C-H de los grupos metoxilo del anillo aromático y a los grupos metil y metileno de las cadenas laterales de los anillos, a 1142 cm -1 se observa una de las bandas en las que se muestra la deformación del anillo de siringilo y a 631 cm -1 la presencia de anillos aromáticos (Gbenebor et al, 2023), cabe señalar que no se observaron señales en la zona de 1700 cm -1 que es característica de un proceso de oxidación.…”