Making Bioplastics from Agro waste

In Italy’s ancient port city of Genoa, a laboratory table at Istituto Italiano di Tecnologia (IIT)  laden with green, brown and orange heaps of powder may remind one of Holi, India’s festival of colours. But this is a scene of cutting-edge research on crafting biodegradable plastics out of agro-waste, a component whose poor management in India is a root cause of air pollution.

These powders, derived from fruit and vegetable waste, are the raw materials for bioplastics fabricated by the researchers at IIT Genoa’s Smart Materials lab part of the team composed by Giovanni Perotto, Ilker Bayer and Athanassia Athanassiou.

Bioplastics are derived from renewable, plant-based sources such as vegetable plants and oils, wood chips, etc., and are a potential alternative to fossil-fuel derived plastics.

At IIT Genoa, researchers transform these powders to bioplastics of varying flexibility and mechanical strength using an eco-friendly water-based method.

So while bright green powdered parsley and spinach stems became soft and stretchable plastic films, rice husks yielded more robust and less flexible version of bioplastics.

“Our main approach is to use waste material from agriculture such as fruit and vegetable peels, inedible parts of fruits and vegetables and unsold fruit and vegetables. We have established a strong collaboration with the central vegetable market of Genoa, as well as with other producers,” said Despina Fragouli, team leader at the Smart Materials lab.

These powders, derived from fruit and vegetable waste, are the raw materials for bioplastics fabricated by the researchers at IIT Genoa’s Smart Materials. Photo by IIT-Istituto Italiano di Tecnologia.

“We developed a technology for the direct transformation of inedible agro waste into bioplastics,” Fragouli said.

Fragouli discussed the research on eco-friendly smart materials with a visiting delegation of science journalists, including this Mongabay-India correspondent, during a field trip organised alongside the World Conference of Science Journalists, 2019 in July

The technology developed by IIT, Genoa breathes new life into cellulose-rich vegetable and fruit waste and aligns with the idea of a circular economy where a strategy of reduction, reuse and recycling of elements drives resource utilisation.

From powder to plastic

These bioplastics, which are being promoted as biodegradable and environmentally friendly, can be produced in two ways, including a water-based process.

“In the first one, we blend the agro-waste powders with variable amounts of biopolymeric material and then we make objects by processes widely applied in the industry such as melt extrusion, injection moulding or by mould casting,” Fragouli told Mongabay-India in a follow-up email.

“The amount of agro-waste component can reach 70-80 percent by weight in the biocomposites. So in the final composite, a very small amount of polymer is actually acting as a glue to keep the powder particles together,” Fragouli said.

In the second method, the waste powders are simply mixed with specific solvents or water of defined pH without the addition of any other components. 

“The solvent ‘attacks’ and destroys the crystallinity of the cellulose components of the wastes, resulting in homogeneous solutions, and after casting and solvent evaporation, homogeneous plastic films are formed,” Fragouli said.

It can take from a few minutes to a few hours to arrive at the final product. 

Depending on the plant species, biopolymers display diverse mechanical properties ranging from brittleness and rigidity (such as rice husk polymers) to softness and stretchability (parsley stems).

Because of the mild conditions of the fabrication process, the colour of the starting vegetables stay preserved in the bioplastics, the researcher explained. Functional properties of the source material, like antioxidant capabilities and even odour are retained. 

Upon cradling the circular patches of bioplastics, one notices a delicate fragrance, reminiscent of their source: a slightly peppery note of turmeric in one film and a toasty whiff of coffee off a brown coloured bioplastic.

Once produced, the bioplastics can be broken down into non-toxic byproducts.

“Plastics biodegrade at highly variable rates that span from few months to few years. The bioplastics break down into low-weight and non-toxic byproducts. We have proved that our biocomposites are biodegradable either in landfills or even in home composting conditions or even in the sea. The production is not energy-intensive and they are not costly,” said Fragouli.

The time needed for biodegradation depends on the temperature and humidity of the environment and the properties of the plastic component added Fragouli. For instance, crystalline plastics require more time compared to amorphous plastics.

Biodegradable packaging from artichokes. Photo by IIT-Istituto Italiano di Tecnologia.

Article published by sahana

The article was first published in Mongabay India


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