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Lignin from Brewers' Spent Grain: Structural and Thermal Evaluations
Oluwashina Philips Gbenebor1, Oludolapo Akanni Olanrewaju2, Mohammed Awwalu Usman3
1Department of Metallurgical and Materials Engineering, University of Lagos, Lagos 101017, Nigeria.
Polymers
|May 27, 2023
Summary
Researchers explored extracting lignin from brewers' spent grain (BSG) using acid treatments. The study found that sulfuric acid (H2SO4) yielded the most thermally stable lignin, suitable for carbon fiber production.
Area of Science:
- Materials Science
- Biomass Valorization
- Chemical Engineering
Background:
- Brewers' spent grain (BSG) is a major brewery byproduct, posing environmental challenges due to its high moisture content and rapid deterioration.
- Lignin, a key component of lignocellulose, is a valuable precursor for advanced materials like carbon fiber.
- Current methods for lignin isolation often overlook BSG, a readily available and abundant waste stream.
Purpose of the Study:
- To investigate the feasibility of extracting lignin from BSG using different acid solutions.
- To characterize the structural and thermal properties of the extracted lignin.
- To assess the potential of BSG-derived lignin for carbon fiber production.
Main Methods:
- Brewers' spent grain (BSG) was treated with 10 M sulfuric acid (H2SO4), hydrochloric acid (HCl), and acetic acid at 100 °C for 3 hours.
- Fourier Transform Infrared Spectroscopy (FTIR) was used to analyze chemical structure and hydrogen bonding.
- Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), and Differential Scanning Calorimetry (DSC) were employed for thermal stability and structural domain analysis.
Main Results:
- Sulfuric acid treatment (H2 lignin) resulted in the strongest intra- and intermolecular OH interactions with the highest hydrogen bond enthalpy (5.73 kCal/mol).
- Lignin yields from BSG were high, with H2, HC, and AC lignin achieving 82.9%, 79.3%, and 70.2% respectively.
- H2 lignin exhibited the largest ordered domains (0.0299 nm) and superior thermal stability, with a glass transition temperature (Tg) of 107 °C and an enthalpy of reaction of 133.3 J/g.
Conclusions:
- Acid-catalyzed extraction from BSG is a viable method for obtaining high-quality lignin.
- Lignin derived from BSG, particularly using sulfuric acid, demonstrates excellent thermal stability and structural properties suitable for nanofiber formation and carbon fiber precursors.
- This research offers a sustainable approach to valorize brewery waste, mitigating environmental pollution and creating valuable biomaterials.
