Menace of Plastics Waste-Hanging like the Sword of Damocles ?

Plastics, plastics everywhere, you name it, they are  there

Plastics are a part of nearly every product in our daily use today. Production increased from about 2.5 million tons in 1950 to 450 million tons by 2015.  In 2017, nearly 7 % of the nine billion tons of plastic produced became waste.  Production is expected to double by 2050. Every year, about eight million tons of plastic waste escapes into the oceans. As virgin plastic is cheap, industries prefer to make new plastic items than to collect, sort, and process the waste.  

UN World Oceans Day is celebrated every year (on June 8) to highlight the importance of clean oceans which produce more than 50 % of the Oxygen and provide food and  livelihood to millions of people. The United Nations estimated that land-based sources account for up to 80 %of the world’s marine pollution, and 60 % to 95 % of the waste is plastics debris.

Reducing production to solve the waste problem will only aggravate the problem of carbon dioxide (CO2) and climate change, as alternative materials have higher emissions. The manufacturing of plastic emits less CO2 and uses less water than for glass or aluminum.).

Earth Day celebration  (April 22) in 2018 had the theme: End Plastic Pollution. Up to nine million metric tons of plastic waste enters the oceans each year. All organisms are harmed by entanglement, ingestion and by the chemicals in  the plastic waste. Plastics outnumber by 7-to-1 baby fish in coastal ocean slicks that are nurseries for larva.  Humans get adverse hormonal changes due to plastics.

Alliance to End Plastic Waste, is an organization founded at Singapore in 2020, by 50 global industries, to meet the plastic-waste challenge.  It is investing $1.5 billion in creating solutions for collecting plastic waste and recycling into new products. It has launched dozens of projects in Southeast Asia and Africa, in the Philippines, Indonesia, and Ghana.

Vehicular structures made of plastics for automobiles and aircrafts are very economical. But less than 10 % of their waste is recycled, while more than  75%  ends up in landfills and oceans. The rest is burnt, releasing toxic greenhouse gases in the atmosphere. 

Tires have about 10 % of natural rubber from trees and  25% of synthetic rubber, (plastic polymers). Oil, a fossil fuel, is used to make synthetic rubbers. Tires not recycled end up in landfills, while microplastics from wear and tear reach oceans.

Main Polluting Industries include Packaging, Textiles, Consumer goods (like furniture, items for kitchens and sports), Transport, Buildings and Construction, Industrial machinery, and Electrical / Electronic goods.

Micro-plastics are the by-products of chemical degradation of plastics on heating to high temperatures. Infants ingest on an average one million micro-plastics every day from (polypropylene) plastic bottles, when heated (to 950 C), for sterilisation and infant formula preparation. Average daily consumption by infants per capita is about 1.5 million particles. Other products (like kettles and lunchboxes) release similar quantities of  micro-plastic waste, which go into our food-chain.

Recycling is melting the waste to produce lower quality plastic. Plastic resin is made of many identical molecules (monomers) bound into long chains (polymers), with carbon-carbon (C-C) , and carbon-hydrogen (C-H) bonds, difficult to break. Being inert, plastics do not rust or leach into water. For textures and colors, many pigments, heat stabilizers, and flame retardants are added to the resin. During recycling, the polymers get mixed with these additives. However, life of recycled plastic is extended to at least 400 years before breaking down. 

University of Delaware has developed a method (called hydrocracking) to break down the hard plastic waste (polyolefins) into  gases for jet fuels, diesel, and lubricants. Polyolefins account for 60 to 70% of all plastics made today. Refineries use this process to convert heavy crude oil into gasoline. Researchers are using  a method to break the tough bonds, using  platinum on alumina (Pt/Al2 O3) catalyst, (at about 3000 C). This rearranges the polymers to form new plastic structures that are the basis of many industrial and consumer products.

Lawrence Berkeley National Laboratory has produced a new recyclable plastic, Poly-di-keto (PDK) enamine. It is similar to traditional plastics, but there are no environmental pitfalls, because PDKs can be recycled indefinitely with no loss in quality. PDK plastic resin polymers are engineered to easily break down into individual monomers when mixed with an acid. The monomers can then be separated from the additives,  (Nature Chemistry, April 2019).

Self-destroying Plastics are made from compostable compounds of poly-lactic acid (PLA), which were earlier lasting forever in landfills and oceans. Scientists have invented a way to make plastics break down by themselves, with heat and water, within a few weeks. It involves embedding polyester-eating enzymes (such as lipase) in the plastic as it is made. The enzymes, protected by a polymer wrapping, come out of it on heating and start “eating” the plastic, reducing it to lactic acid which feeds the soil microbes in compost.

Turning plastic waste into hydrogen (H2) and carbon nanotubes is another process developed for waste elimination. The very thin nanotubes improve electrical and thermal conductivity because they stretch through the plastic matrix. It pulverizes the plastic waste using microwaves for heating catalysts (aluminum oxide and iron oxide), without heating the plastics. The conversion lasts 30 to 90 seconds, and 97% of the Hydrogen in the waste is recovered.  They are used in auto parts, water filters, thin film electronics and energy storage.

Plant-based  plastics can replace (single-use) disposables in consumer products. This is created from polymer films by mimicking the properties of spider silk, one of the strongest materials in nature. It is home compostable, whereas other types of bioplastics require industrial composting.  Spider silk strength is due to hydrogen (H) bonds arranged regularly in space, in high density.  Proteins have a propensity for molecular self-organization and self-assembly. Plant proteins in particular are abundant and are sourced as by-products of the food industry. Other researchers are working directly with soluble silk materials as a plastic replacement.  

All these methods have the potential to reduce the menace of persistent plastic- waste pollution.

Plastics-waste pollution is very long-lived and is destroying the planet Earth. Some plastics, such as PVC or vinyl, contain phthalates (as solvents) and heavy metals. They create dioxins (persistent environmental polluters) when burnt. Other plastics contain Bis-Phenol-A (BPA), a chemical that disrupts hormones. Plastic waste is generated differently by different polymer types. These include – LDPE: Low-density polyethylene, – HDPE: High-density polyethylene, – PP: Polypropylene, – PS: Polystyrene, – PVC: Polyvinyl chloride, – PET: Polyethylene terephthalate and – PUT: Polyurethanes. Plastics contain thousands of additives, and manufacturers are not required to disclose what their recipes are ! That makes them much more dangerous.

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