###### Abstract  
This work reports on the development and performance evaluation of newly developed paper sheets coated, on both sides, with thin films of biodegradable poly(3-hydroxybutyrateate-co-3-hydroxyvalerate) (PHBV) for applications of food packaging. For this, PHBV/paper/PHBV multilayers were first prepared by the thermo-sealing technique, optimizing the process variables of temperature and time. Thereafter, the multilayer sheets were characterized in terms of their morphological, optical, thermal, mechanical, and barrier properties and compared with equivalent paper structures double coated with high-barrier multilayer films of petrochemical polymers. The results indicated that the double coatings of PHBV successfully improved the mechanical resistance and ductility, protected from moisture, and also reduced the aroma and oxygen permeances of paper, having a minimal effect on its optical and thermal properties. Finally, the composability of the resultant multilayer sheets was analyzed, confirming that the presence of the PHBV coatings slightly delayed the aerobic biodegradation and disintegration of paper. paper; PHBV; multilayers; food packaging; Circular Economy 202313179913010179130101791301017913010179130101791301017913010179130179130101791301791  
sents a sustainable option due to its biodegradable nature and the fact that it can be more easily recycled than plastic. However, paper lacks moisture resistance and shows poor thermal, mechanical, and barrier performances so that it is habitually coated with plastic materials [6]. Thus, multilayer packaging structures based on paper have expanded tremendously during the past few years, with use of different coating technologies to offer several functionalities, such as hydrophobicity, a gas and moisture barrier, antimicrobial protection, cohesive strength, scratch resistance, etc. [7]. Different petrochemical polymers have been used for coating paper, including polypropylene (PP) and biaxially oriented polypropylene (BOPP), low- and high-density polyethylene (LDPE, HDPE), polyethylene terephthalate (PET), biaxially oriented polyamide (OPA), and more importantly their combinations in the form of multilayers with high-barrier poly(ethylene-_co_-vinyl alcohol) (EVOH) [8]. These plastic multilayers have been demonstrated to increase the barrier against moisture, oxygen, odor, and grease, and offer favorable stiffness, toughness, processability, manufacturing cost, chemical resistance, and thermal stability. Nevertheless, these are not biodegradable and must be properly separated from paper for recycling to avoid impairing the compostability and recyclability of paper [9]. In this context, biopolymers can solve the main environmental constraints and limitations of the food packaging industry [10]. On the one hand, biopolymers can be obtained from natural and renewable sources. On the other hand, the resultant packaging materials can be composted or biodegraded in the environment [11]. Thus, some biopolymers are very promising as paper coating materials, including polysaccharides (e.g., chitosan, starch, lignocellulosic derived compounds, and alginates), proteins (e.g., whey, wheat gluten, and zein) and, most relevantly, polyesters such as polylactide (PLA), poly(\(\varepsilon\)-caprolactone) (PCL), and recently polyhydroxyalkanoates (PHAs) [12]. PHAs are semi-crystalline aliphatic polyesters that offer the advantage of being synthesized by microorganisms using renewable sources, such as sugars and triglycerides, and can also biodegrade under natural conditions [13]. Therefore, PHAs can offer key benefits over petrochemical polymers to reduce packaging's carbon footprint and avoid \"white pollution. Poly(3-hydroxybutyrate) (PHB) is the homopolyester and most common type of PHA, which has some physical properties similar to those of PP and PET [14; 15; 16]. However, the high crystallinity of PHB results in a highly rigid and brittle material that is also difficult to process due to its narrow processing window and low thermal stability [17; 18].