From Plaintains to Plastic: Agricultural Waste Turns Into Compostable Polymers

Researchers from the Universidad del Valle (Univalle) have found a way to turn pineapple crowns and plantains that aren't commerical-grade to produce an eco-friendly alternative to single-use plastics.

In June 2022, the Colombian Senate approved the legislation that bans single-use plastics in the country including knives, forks, spoons, mixers and straws for drinks, citing that every year each Colombian uses the equivalent of 24 kilos of plastic per year, 93% of which is not recycled.

In addition,the estimated agricultural waste production of plaintains for Colombia in 2017 was 26.5 million metric tonnes (equal in mass to 4 pyramids of Giza).

In the scientific publication "Potential Uses of Musaceae Wastes: Case of Application in the Development of Bio-Based Composites" that came out in the international scientific journal Polymers, the researchers, led by Professor José Herminsul Mina, from the School of Materials Engineering (EIMAT), explored the possibilities of replacing disposable plastics with products based on novel biopolymers, i.e. plastics made from agricultural waste sources, not of petrochemical origin like conventional synthetic plastics.

"Starch is characterized by the fact that it absorbs a lot of moisture and in previous years, biopolymers made with only starch did not have the same characteristics as conventional plastics, for example, a mixing stick that does not withstand the heat and humidity of coffee," said Professor Mina, adding the researchers found that incorporating fibers from pineapple crowns and other parts of the plantain, this problem is solved.

To face all these challenges, during the last three years, Professor Mina, with international and national collaborators have developed a project financed by the Colombian Ministry of Science.

 

Photo: Professor Miguel Angel Hidalgo Salazar (left) and Juan Pablo Correa, Materials Engineer graduated from UNIVALLE in the laboratory. Credit: GITEM

The Research

In the Polymer Laboratory, a team of undergraduate and graduate researchers process third-grade plantains, reducing them to a starch paste.

In another lab at the School of Materials, Professor Mina showed a white powder that was this same paste after oven drying.

"It is this starch powder is combined with pineapple and plantain fibers and extruded in a very similar way to how it is done with conventional plastics," Professor Mina explained, adding that the final products are very similar to what we use polystyrene for today: cutlery, plates and other single-use disposables.

"The tools and techniques to convert agricultural waste, plantain and pineapple, into the fibers needed for these biopolymers are within the reach of small farmers, potentially providing those same farmers with a value-added product that they can sell for additional income," Prof. Mina explained.

Miguel Angel Hidalgo Salazar, a full professor at the Faculty of Engineering and Coordinator of the Research Group in Technology for Manufacturing - (GITEM) at Universidad Autónoma De Occidente (UAO, in Cali Colombia) and Professor Mina have been working together for more than 10 years.

Professor Hidalgo said that the dynamic/thermal/mechanical analysis (DMA) available at UAO helps in the characterization of new materials, using a combination of mathematical modeling and mechanical experimentation.

VIDEO: Profesor Miguel Angel Hidalgo Salazar  Crédito: GITEM

The Circular Economy

"Undoubtedly, this type of project will support the development of the circular economy of the country and the region," Professor Hidalgo said.

"The use of this type of materials, in the case of thermoplastics and the different materials we want to obtain including nanomaterials, for example for the production of food utensils, will have a great impact on the environmental issue," Professor Hidalgo said.

Dr. Lety del Pilar Fajardo Cabrera, a lecturer in the Department of Industrial Design at Universidad del Valle and a key collaborator on the project with Professor Mina, said that the development of new materials opens up the possibilities of designing more sustainable products.

"Contemporary industrial designers must seek to satisfy users in such a way that by blending technique with aesthetics, they combine practical utility with emotional pleasure, " explained Dr. Fajardo, adding that the three aspects of Triple Bottom Line must also be considered: balancing social, environmental and economic impacts.

"These types of projects for obtaining and applying materials from the recycling of agro-industrial waste collaborate directly with the optimization of the circular economy," Dr. Fajardo said.

Read more from the School of Materials Engineering: Wood From Waste and Seismic protection: Two Univalle Patents Improving the World 

Professor Mina in the laboratory of the Centro de Investigación Científica de Yucatán (CICY), conducting a biodegradation study Credit: Andrew James/NCC-FI/Univalle

Claves colaboradores internacionales

The researchers said it is important to analyze if and how the polymers are compostable, that is, they do not contribute to the generation of microplastics which today is a major concern in the areas of environmental pollution and health.

To get an assessment of how biopolymers degrade over time, compared to conventional plastics, Prof. Mina teamed up with the group of Professor Alex Valadez-Gonzalez, a researcher at the Yucatan Scientific Research Center  (CICY).

"In the last five years my group has been working on the study of biodegradation of polymeric materials while Dr. Mina's group has been working on the design and development of biodegradable composite materials," Prof. Valadez-Gonzalez said, adding that the project is a clear example of multidisciplinarity.

"Collaboration between institutions is always a win-win relationship as it allows us to tackle multidisciplinary projects in which we share the use of scientific infrastructure and the experience of the participants, who are generally from complementary specialties," Prof. Valadez-Gonzalez 

said.

If you would like to contact the researcher or learn more about the project, please write to the Communications Office, Faculty of Engineering: comunicaingenieria(at)correounivalle.edu.co.

Banner photo: Professor Mina (left) Credit: Andrew James/NCC-FI/Univalle