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This work addresses the management of Brewers' Spent Grain (BSG) using a state-of-the-art, microwave-assisted, hydrothermal carbonization (MA-HTC) process, for the production of hydrochar, i.e., a renewable solid biomaterial with many industrial applications. For the first time, a detailed relationship has been established between the processing conditions and the properties of the hydrochar via a thorough physicochemical characterization. The experimental results revealed that the temperature (180−250 °C) and reaction time (0−2 h) used in the MA-HTC process exerted a significant influence on the yield and properties of the hydrochar. An increase in these variables (process severity) diminished the hydrochar yield. However, such increments were beneficial to enhance the fuel properties of this product, as the proportions of O and C decreased and increased, respectively. As a result, this process was capable of transforming up to 47% of the original BSG into a high-energy hydrochar with a calorific value of 32 MJ/kg. The characterization of the hydrochar revelated that it was a mesoporous, hydrophilic, rough material, containing several cavities and oxygen functionalities on the surface. These features not only provide the hydrochar with a high aromatic character but also are fundamental for its potential applicability as a bioadsorbent material. An increase in the MA-HTC severity augmented the amounts of aliphatic and aromatic structures in the hydrochar as well as the roughness and the presence of cavities, thus highlighting the excellent flexibility of the process. Therefore, these promising results, together with the energy-efficient and bespoke nature of the MA-HTC process, which substantially reduces the reaction temperature and processing times in comparison to standard carbonization procedures reported to date, represent a step-change not only for the production of biofuels and biomaterials but also for the management of BSG.

The table olive industry is producing a huge amount of wastewater, which is a post-processing cost and an environmental concern. The present study aims to valorize this processing by-product to obtain a value-added product, thereby enhancing resource efficiency and contributing to achieving sustainable development goals (SDGs). In this sense, a chemical reaction-based platform was developed to obtain valuable components, such as levulinic acid (LA) and 5-hydromethylfurfural (HMF). The products were then analyzed using NMR identification of the antioxidant phenolic fraction and microwave single-phase reaction of the sugary fraction. According to the results, the highest concentration of phenolic compounds does not correspond to the sample directly obtained from NaOH treatment (S1), indicating that water washing steps (S2–S5) are fundamental to recover phenolic substances. Moreover, glucose was presented in the sugary fraction that can be transformed into levulinic acid by a single-phase reaction under microwave irradiation. The information provided in this manuscript suggests that the wastewater from the olive processing industry can be valorized to obtain valuable products.

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Electrochemical energy storage technologies offer means to transition toward a decarbonized society and carbon neutrality by 2050. Compared to conventional lithium-ion batteries, aqueous zinc-ion chemistries do not require scarce materials or toxic and flammable organic-based electrolytes to function, making them favorable contenders in the scenario of intensifying climate change and supply chain crisis. However, environmentally benign and bio-based materials are needed to substitute fossil-based battery materials. Accordingly, this work taps into the possibilities of lignin together with chitosan to form gel polymer electrolytes (GPEs) for zinc-ion chemistries. A simple fabrication process enabling free-standing sodium lignosulfonate− chitosan and micellar lignosulfonate−kraft lignin−chitosan GPEs with diameters exceeding 80 mm is developed. The GPEs combine tensile strength with ductility, reaching Young's moduli of 55 ± 4 to 940 ± 63 MPa and elongations at break of 14.1 ± 0.2 to 43.9 ± 21.1%. Competitive ionic conductivities ranging from 3.8 to 18.6 mS cm −1 and electrochemical stability windows of up to +2.2 V vs Zn 2+ /Zn were observed. Given the improved interfacial adhesion of the GPEs with metallic Zn promoted by the anionic groups of the lignosulfonate, a stable cycling of the Zn anode is obtained. As a result, GPEs can operate at 5000 μA cm −2 with no short-circuit and Coulombic efficiencies above 99.7%, outperforming conventional separator−liquid electrolyte configurations such as the glass microfiber separator soaked into 2 M ZnSO 4 aqueous electrolyte, which short-circuits after 100 μA cm −2 . This work demonstrates the potential of underutilized biorefinery side-streams and marine waste as electrolytes in the battery field, opening new alternatives in the sustainable energy storage landscape beyond LIBs.