A new collaborative research between universities in Spain and Honduras found that agricultural waste from yucca, taro, and bananas can be used to manufacture bioplastics. The study, published in Polymers, provided a complete analysis and evaluation of the three different Honduran agro-wastes, exploring the physicochemical and thermal properties to optimize their processing conditions for the development of bioplastics.
The agro-wastes the authors collected consisted of damaged or deformed fruits that could not be sold on the market due to hygienic or quality problems. In addition, glycerol and distilled water were used as plasticizers for the manufacture of bioplastics.
The samples were washed, cut into thin slices and “submitted to a drying process in an oven at 60 °C for 4 h to prevent denaturation of the polymers and, after that, they were tempered at room temperature for 40 min. This drying process was carried out in order to prevent the high water content of these samples (>50%) from destabilizing the flours obtained during storage
“Once dried, the slices were fed into a rotating ball mill LIHONG LHG-1.5 (Agropec, Madrid, Spain) where the friction of the balls breaks the particles and gradually reduces their size until they pass through a 60-micron sieve (250 mesh). This process allows the obtention of the flours.”
“The bioplastic processing was performed in three different stages where raw materials were mixed, homogenized, and conformed. The selected proportions were 70, 20, and 10 wt.% of flour, glycerol, and distilled water, respectively. The blends obtained after the mixing stage were processed through extrusion to produce pellets that could be shaped as bioplastics. Finally, pellets were shaped by injection molding to produce bioplastics”.
The authors found that taro flour presented the highest protein content and banana flour showed the highest moisture content. Banana bioplastics had the best mechanical properties, with a Young’s modulus around 300 MPa, while taro bioplastics had the highest water-uptake capacity (200%). In general, the results “showed the potential of these Honduran agro-wastes for producing bioplastics with different characteristics that could add value to these wastes, promoting the circular economy” the authors wrote.