Feasibility of producing biodegradable paper from malt bagasse: Bridging waste valorization, material performance, and circular economics

The brewing industry generates large volumes of malt bagasse, an underutilized lignocellulosic residue that poses an environmental challenge and represents an opportunity for the circular economy. In the face of increasing pressure on forest resources for paper production, the valorization of agro-industrial waste as an alternative source of cellulosic fiber emerges as a sustainable strategy. This study aimed to evaluate the technical and economic feasibility of producing biodegradable paper from brewer’s spent grain using an alkaline pulping process with sodium hydroxide (NaOH). The methodology included the collection and pretreatment of the bagasse, two-stage alkaline digestion (70 °C and 80 °C), morphological characterization of cellulose by scanning electron microscopy (SEM), and evaluation of the physical and mechanical properties of the resulting paper (grammage, moisture content, ash content, porosity, tensile strength, and tear resistance). The results showed a high grammage (233 g/m2), low porosity in the paper samples (Average: 27.96 μm2), ash content of 2.38%, maximum tensile stress of 2.26 MPa, elongation at break of 1.52%, and average tear resistance of 2.19 N—values comparable to those of commercial papers. Although the production cost at laboratory scale was high ($108.18/m2), the prospective analysis indicates that NaOH recovery (>80%) and process scale-up could reduce it to $3.28/m2, making it competitive. In conclusion, brewer’s spent grain constitutes a viable raw material for biodegradable paper production, aligned with circular economy principles, although further optimization is required to improve homogeneity, reduce ash content, and enable sustainable scale-up.