In recent years, the increasing emphasis on responsible consumption and production has driven researchers to investigate more environmentally friendly options to replace fossil-based polymers [1]. This is due, in part, to the fact that current plastic waste recycling methods have not resulted in a significant reduction in the amount of plastic waste being disposed of in the environment, landfills, or through incineration. Indeed, current trends indicate that the mass of plastic waste generated is projected to reach 150 million tons by the year 2050 [2], further exacerbating the negative consequences associated with existing waste management approaches. These challenges include groundwater pollution caused by the leaching of plastic waste and the release of harmful chemicals like dioxins, furans, and polychlorinated biphenyls into the environment during incineration [2]. To address these waste management issues, the substitution of traditional fossil-based polymers with biobased alternatives has emerged as a viable solution [3]. Biobased polymers, or biopolymers, have gained significant attention for diverse applications, including the development of food packaging materials [4].

Among biopolymers, starch stands out as a promising replacement for non-degradable polymers due to its biodegradability, sustainability, widespread availability, and cost-effectiveness [5]. Starch, a polysaccharide biopolymer, is primarily found in plants [6], such as maize, cassava, wheat, rice, and potatoes, where it serves as a reserve of sugar molecules [7]. Despite its favorable film-forming properties, starch-based films are characterized by poor resistance to moisture due to their hydrophilic nature and limited mechanical strength [8,9].

To enhance the properties of starch-based films, various modification techniques have been explored. These methods range from chemical modifications to the incorporation of different polymers, compounds, and fillers into starch matrices [10]. The incorporation of natural fillers is of particular interest due to their affordability and biodegradability, with lignins being identified as a promising natural polymer to be used alongside starch in film production [11]. Lignins, the second most abundant natural polymer after cellulose, are present in the cell walls of lignocellulosic materials and serve as binding agents [[12], [13], [14], [15]]. Lignins consist of chemical units that contribute to hydrophobicity, UV absorption, and antioxidant properties when used as a filler in composites [16]. Comprising aliphatic and aromatic compounds, lignins are biosynthesized from components such as p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol [17]. Their structure is influenced by botanical source and extraction methods [18]. In alignment with the principles of a circular economy [19], lignins sourced from highly polluting potato crop residues (PCR-lignins) could be a valuable natural filler, as up to 46 million tons of potato crop residues (PCR) are generated globally each year [20]. Utilizing them can help mitigate associated pollution challenges [21]. In this study, the organosolv process was employed to recover lignins from PCR. In comparison to other lignin extraction methods such as kraft, sulfite, and soda processes [22,23], the organosolv process facilitates the efficient recovery of high-purity, sulfur-free lignin [24]. Additionally, the organosolv treatment can be integrated into other processes through solvent selection and can be made more economically viable through solvent recovery [25]. Importantly, a literature review indicates that the extraction of lignins from potato crop residues and their subsequent use to reinforce starch-based biocomposites has yet to be explored.

The objective of the present study is to utilize organosolv lignins from potato crop residues to produce innovative biodegradable biocomposites for food packaging. The impact of lignin content on the properties of the prepared films was investigated through various analyses, and the results are discussed in detail. The chemical composition of starch films and lignin particles incorporated into the starch matrix was determined using ATR-FTIR. The influence of lignins on the starch matrix was further evaluated through mechanical testing, X-ray diffraction, FE-SEM, TGA, UV–Vis spectrophotometry, oxygen permeation testing, water vapor transmission rate measurement, water swelling analysis, and antioxidant assays.