Hydrogels have become one of the potential polymers used with great performance for many issues and can be promoted as biomaterials with highly innovative characteristics and different uses. Gelatin is obtained from collagen, a co-product of the meat industry. Thus, converting wastes such as cartilage, bones, and skins into gelatin would give them added value. Furthermore, biodegradability, non-toxicity, and easy cross-linking with other substances can promote polymers with high performance and low cost for many applications, turning them into sustainable products with high acceptance in society. Gelatin-based hydrogels have been shown to be useful for different applications with important and innovative characteristics. For instance, these hydrogels have been used for biomedical applications such as bone reconstruction or drug delivery. Furthermore, they have also shown substantial performance and important characteristics for remediation for removing pollutants from water, watercourse, and effluents. After its uses, gelatin-based hydrogels can easily biodegrade and, thus, can be sustainably used in the environment. In this study, gelatin was shown to be a potential polymer for hydrogel synthesis with highly renewable and sustainable characteristics and multiple uses.

Walnut kernels represent no more than 50-60% of the total weight of the fruit, so the sum of walnut shells generated every year is immense. Nonetheless, these shells could be further valorised for the extraction of their main constituents following a biorefinery scheme. Hence, the objective of this work was an integral valorisation of walnut shells, which involved a sequential organosolv delignification (200 °C, 90 min, 70/30 v/v EtOH/H₂O, LSR 6:1) and several posterior non-isothermal hydrothermal treatments (180, 195 and 210 °C, LSR 8:1). Moreover, the spent solids after the aforementioned treatments were evaluated as possible sources of cellulose nanocrystals. The results showed that the sequential organosolv delignifications presented relative lignin yields up to 60%, which leaded to lignins that just differed on their molecular weight distributions. The hydrothermal treatments were efficient for the removal of still present hemicelluloses (14.7-71.8%), and permitted a successful cellulose nanocrystal obtaining whereas the spent solid from the delignification stages did not. Thus, this study presented an innovative strategy for the integral valorisation of walnut shells.

The chemical industry’s transition towards sustainability necessitates the development of eco-friendly processes that can replace petrochemical derivatives. Lignin, the second most abundant plant polymer, has potential as a renewable alternative to phenolic compounds. This study investigates lignin precipitation from softwood black liquor using five organic acids (acetic, citric, lactic, malic, and oxalic) as a sustainable alternative to sulfuric acid. The precipitated lignins were subjected to comprehensive chemical and thermal characterization, revealing higher total phenolic content and enhanced reactivity when organic acids were employed. Notably, organic acid-precipitated lignins demonstrated comparable or superior purity, with ash contents below 0.50%, compared to 3.28% observed for sulfuric acid-precipitated lignin. These findings suggest that organic acids are a viable and greener alternative for lignin precipitation, promoting higher purity and yield, thus supporting lignin valorization efforts.