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Neat poly (lactic acid) (PLA) and PLA/cassava bagasse (CB) composites were used to produce seedling tubes by extrusion and injection molding. The tubes were buried in simulated soil, and their biodegradation was investigated by weight loss, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). After 180 days, the composites' biodegradation was higher than neat PLA material, and the higher the CB content, the higher the biodegradation, which caused fissures and voids in the material. The biodegradation of PLA/CB composites increased the phosphorus content in the soil after 180 days. Composites of PLA with CB, an abundant agro‐industrial residue in Brazil, are promising because they can reduce the environmental impact due to CB's proper destination, and the composites' costs and biodegradation are faster than pure PLA material. Both the faster biodegradation of the tube and the higher P content are advantageous for seedling tubes.

Studies using starch to produce biodegradable materials have proved attractive due to its availability and low cost in relation to commercial biodegradable polymers, such as poly (lactic acid) and others. Starch-based materials do not have adequate mechanical properties for production and use on a commercial scale, requiring mixtures (blends) with other biodegradable polymers to improve these properties. However, these blends need compatibilizers due to the immiscibility between the starch and the polymer. The present work aimed to study the effect of different compatibilizers (3-(trimethoxysilyl) propyl methacrylate, citric acid, and maleic anhydride) on the functional properties of biodegradable starch and poly (lactic acid) (PLA) materials produced by extrusion and thermoplastic injection. Citric acid was considered the best compatibilizer for these materials because it improved the processability, and the materials presented properties suitable for applications where good mechanical resistance is required. In addition, the materials containing citric acid and maleic anhydride were more uniform from the morphological point of view.

The incorporation of tannin in bio-composite biodegradable thermoset materials (BTM) based on poly (lactic acid), starch, sugarcane fiber, and nutrient compounds, to achieve an alternative material for conventional plastics processed by injection molding aiming environmental applications was investigated. The biodegradation of injection molded BTM dog-bone shape specimens prepared with and without incorporation of 1% tannin extract was evaluated up to 60 days with overall characterization by scanning electron microscopy, Fourier transform-infrared spectroscopy, thermogravimetric analyzer, and X-ray diffraction. The BTM produced with 1% tannin showed reduced molding defects with an increased productivity of up to 82%, improved mechanical properties and reduced biodegradation of samples buried in an organic substrate. Based on physicochemical characterization, the observed delay in biodegradation of BTM induced by tannin is suggested to result from its tight interaction with the starch and lignocellulosic fibers, acting as antimicrobial agent and reducing the hydrophilicity of blends. Natural polyphenols such as tannins are suitable additives to improve the processability of injection molded bio-composites and to extend the lifetime of biodegradable materials subjected to contact with high microbial load substrates, such as pots and buckets used to grow plants.