Recycle plastics for a cleaner environment and circular economy

For effective recycling, segregation of plastic material according to their properties or resin material needs to be science-based



By Shalini Verma

Published: Mon 10 Oct 2022, 10:24 PM

I happened to visit a grocery store in a sleepy village located in the hilly parts of Southern India. The store was tidy despite the glaring absence of garbage bins. So, I enquired about the store’s waste disposal system. The storekeeper casually said that he threw all his trash in the river. The river was fed by the hills and was joined by other streams before it emptied into the Arabian Sea. At first glance, you wouldn’t think that it carried all that waste from the villages it cut through. As no municipal truck rolls in, the villagers struggle with their plastic waste, which makes its way into the river and the ocean.

Plastic’s carbon footprint is relatively small - a third of that of glass and aluminium - because plastic does not decompose easily. This is precisely why it is a problem because it chokes rivers and drains and pollutes our environment with microplastics. Yet plastic is indispensable, especially in the food and pharma industry. Our complicated relationship with plastic means that its product lifecycle needs to become circular.

The good news is that regulators across the world are mandating extended producer responsibility (EPR) based on the polluter pays principle. This is a step towards a closed-loop approach because it forces producers to take ownership of the waste and manage it responsibly. Most countries are at various stages of transitioning from EPR as a political agenda to one that is mandated. For plastic waste, packaging manufacturers are mandated to include a certain proportion of recycled plastic. In India, the EPR target is 70% in 2022-23, going up to 100% in 2023-24. In the UAE, the importer would be a key segment to be held responsible.

Collection, sorting and recycling of plastics are on the cusp of significant innovation. There is plenty to get done. Plastic waste is a problem of measurement. Plastic waste is a problem of collection. Most of all, plastic waste is a problem of segregation. It comes mixed with wet waste if segregation is not done at source. Even after segregation, mixed plastics remain a hard problem to solve.

For effective recycling, segregation of plastic material according to their properties or resin material needs to be science-based. There are around 21 types of plastics found in e-Waste such as our old computers and refrigerators. In large landfills, municipal solid waste is being treated by massive trommel screens. This is a start, at least to separate some of the materials. Promising technologies that can identify resin material include near-infrared spectroscopy which identifies light-colored plastic material based on molecular vibration.

Segregation of plastics using AI-vision is evolving. Labour-intensive manual sorting is still more cost- effective for larger sizes. Yet there are many solutions using simple concepts of physics. Plastics can be segregated based on the material’s electrostatic charge or solvency. Air sorting takes out lighter material, while the float-sink separation technique drops the plastics. The less-dense material floats leaving the heavier ones to sink. You can amplify the material weight using centrifugal force to separate materials with a slight difference in weight. In practice, a combination of all these approaches is used to segregate mixed plastics.

Recycling is an environmentally friendly treatment of used plastics. Incumbent recyclers tend to use traditional labour-intensive sorting, grinding, washing and shredding. The material is then melted and shaped into granules. Modern mechanical recycling approaches tackle the diversity in plastics. Granules sometimes can nearly match the quality of virgin plastic. Mineral water bottles can be upcycled for making textiles, garden sprinklers and flowerpots. Sometimes we get downgraded recycled material that loses qualities like optical clarity, which is unfit for rigorous engineering use. It can still be used for making things like artificial turf.

Mixed residual plastics that are hard to recycle undergo chemical recycling. In one approach, polymers are broken down into simpler hydrocarbons through a destructive thermal treatment called pyrolysis. Shell is investing in BlueAlp’s technology, which transforms plastic waste into pyrolysis oil for Shell’s plants. However, the cost of Pyrolysis needs to be optimized. Non-recyclable multilayered plastic such as sachets and chocolate wrappers are simply shredded and burnt as refuse-derived fuel. Industries such as cement with high carbon emissions use refuse-derived fuel to partially substitute coal. Dubai Municipality is setting up the world’s largest waste-to-energy facility for diverting waste from landfills. The resultant 1,000 tonnes of bottom ash will be used in infrastructure projects. Lastly, there are biodegradable plastic materials that are compostable.

Recycling is an all-in effort to divert plastics from landfills. Plastic recycling will be central to a circular economy. We should thoughtfully segregate our plastic waste, avoiding contamination. Brand owners should design their EPR process. Recyclers need to modernize their plastic waste management systems.

- Shalini Verma is a serial entrepreneur. She recently founded a women-led climate tech startup.


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