PBS is a biodegradable polyester that can be produced from petroleum-derived or renewable feedstocks. Its appeal comes from a balance of properties that is difficult to achieve in many bioplastics: it can be processed using established polymer-manufacturing techniques, it can degrade under suitable environmental conditions, and it offers useful mechanical performance. Yet unmodified PBS is not a perfect replacement for more rigid engineering plastics. The review identifies relatively low stiffness, limited thermal resistance and only moderate mechanical strength as important barriers to wider industrial use. In practical terms, a product made from neat PBS may be flexible and workable but lack the rigidity or heat tolerance required for demanding packaging, vehicle components or durable goods.

The strategy examined by the authors is to embed organic reinforcements inside the PBS matrix. In a composite, the polymer forms a continuous phase that surrounds and binds a second material, such as a fiber, powder or starch-rich residue. When the reinforcement is stiff and well distributed, an applied load can be transferred from the comparatively soft polymer to the stronger plant-based phase. This can raise stiffness and hardness, but the outcome depends on the microscopic structure of the material. Fiber length, particle size, moisture content, surface chemistry, processing temperature and filler concentration all influence whether the reinforcement strengthens the composite or instead creates defects that weaken it.

The central technical challenge is the interface between hydrophobic polymer chains and naturally hydrophilic plant matter. Cellulose, hemicellulose and other components of agricultural residues contain chemical groups that interact readily with water, while the PBS matrix does not bond with them automatically. Poor interfacial adhesion can leave gaps around fibers or particles, allowing cracks to begin and spread under stress. The review therefore emphasizes interfacial compatibility and filler dispersion as decisive factors. Compatibilizers can act as molecular bridges, improving fiber–matrix adhesion and helping the two phases behave more like a unified material. Chemical surface treatments, reactive processing and carefully selected blend components are among the approaches discussed for controlling this interface.

Natural fibers are among the most direct ways to reinforce PBS. Jute, cotton, bamboo, ramie, date-palm fibers and other plant-derived reinforcements contain elongated cellulose-rich structures that can support tensile loads along their length. Their geometry makes orientation especially important: aligned fibers can provide greater directional strength, whereas randomly distributed fibers may produce more uniform but less pronounced reinforcement. The review also examines wood flour and bamboo powder, which can supply a wood-like appearance and increase rigidity in molded materials. These fillers are attractive not only because they are renewable, but also because they may come from existing forestry or agricultural streams rather than requiring a dedicated crop grown solely for plastics.

Food and crop residues broaden the concept beyond traditional fibers. Grape pomace, apple pomace, rice husk and cassava pulp contain mixtures of cellulose, lignin, starch and other organic constituents, giving them different shapes, surface chemistries and thermal behaviors. Instead of treating these materials as waste requiring disposal, manufacturers could potentially mill and incorporate them into PBS-based products. The review identifies such residues as promising fillers for low-cost composites, although their variability presents a manufacturing problem. A filler collected from one crop, region or processing method may differ substantially in moisture, composition and particle morphology from another. Industrial use would therefore require consistent preparation, drying, size control and quality standards.

Adding more filler does not automatically make a composite better. At moderate concentrations, rigid particles and fibers can increase stiffness and surface hardness. At excessive loadings, however, the polymer may no longer wet or surround the reinforcement effectively. Particles can agglomerate, fibers can become poorly bonded, and voids can form during melt processing. These defects concentrate stress and can reduce ductility, impact resistance and overall toughness. In other words, the material may become harder to deform but more likely to crack. The review highlights this trade-off as a recurring pattern: natural reinforcements often improve rigidity while sacrificing some of the flexibility that makes unfilled PBS useful.

Thermal behavior is similarly complicated. Plant-based fillers can alter the way PBS chains crystallize, move and reorganize during heating and cooling. Crystallinity—the formation of ordered regions within a polymer—can affect stiffness, dimensional stability and heat resistance. A dispersed filler may act as a site that encourages crystal formation, but organic components can also begin to degrade at processing temperatures or interfere with the polymer’s morphology. As a result, the effects of natural reinforcement on thermal stability are not uniform. Processing must be carefully controlled to avoid damaging the biomass while still producing a well-consolidated composite. The review calls for further optimization of processing conditions, rather than assuming that a single formulation will work for every residue.

The potential applications range from short-lived packaging to longer-lasting technical products. PBS composites containing starch, cellulose or agricultural fibers could be developed for compostable films, trays and other packaging formats, while rice-husk and wood-based formulations may be considered for molded components. In agriculture, biodegradable mulch films and slow-release materials could reduce the need to retrieve plastic products from fields after use. Automotive components are another possibility because natural fillers can reduce density and increase stiffness, although durability and thermal requirements remain demanding. Biomedical uses are also discussed, including composites in which lignin or other bio-derived constituents may contribute additional functions such as antioxidant or antibacterial behavior. These applications remain dependent on performance, safety, cost and end-of-life testing.

The review’s broader message is that sustainable plastics will probably need more than a single substitute polymer. PBS offers a biodegradable matrix, but its environmental value depends on how it is produced, what additives and reinforcements it contains, and whether the finished material can be managed appropriately after use. Incorporating agricultural residues could lower reliance on virgin resources and create value from biomass that might otherwise be discarded, but biodegradation is not instantaneous or identical in every environment. The authors call for long-term studies of degradation behavior, stronger control over interfaces, optimized manufacturing and assessments that follow materials across their life cycle. If those challenges can be resolved, PBS-based green composites could turn crop waste into useful products—and make the humble leftovers of food production part of the next generation of plastics.