With 18 million tonnes, a remote island turns into plastic junkyard


Plastic debris on Henderson Island in Pacific Ocean

The beaches of Henderson Island, an uninhabited island in the South Pacific Ocean about 5,000 km away from the nearest population centre, are heavily littered with plastic waste. The beaches have an estimated 38 million plastic debris items weighing 17.6 tonnes.

The largest of the four islands of the Pitcairn Island group, Henderson Island is a Unesco World Heritage Listed site. Since it is uninhabited, its ecology is largely untouched by humans.

With 671 plastic items per sq metre on the surface of the beaches, the island has the highest density of plastic waste reported from anywhere in the world. And the amount of plastic waste on the island is ever growing with about 27 new plastic items per metre getting accumulated on a daily basis; in the North Beach of the Island alone, about 3,570 items get deposited daily. The results were published in the journal Proceedings of the National Academy of Sciences.

crab-OptimizedIn 2015, the researchers enumerated over 53,000 plastic items and arrived at an estimate of 37 million items littered on the beach. And alarmingly, even the 37 million plastic items may be an underestimation.  The reason: the team could not sample plastic waste buried below 10 cm from the surface and particles below 2 mm size and those found in the cliff areas and rocky coastline were not sampled.

With plastic waste disintegrating, smaller items were predominant, with microplastic accounting for 62% of items found in the Henderson Island.

The Henderson Island is located ion the western boundary of the South Pacific Gyre, a known plastic-accumulation zone for debris carried from South America (27%) or deposited by fishing boats.

“The plastic waste creates a physical barrier and contributes to a reduction in the number of sea turtles laying attempts, lower density of shoreline invertebrate communities and increased hazard of entanglement of coastal-nesting seabirds,” they write.

“Research has shown that more than 200 species are known to be at risk from eating plastic, and 55 per cent of the world’s seabirds, including two species found on Henderson Island, are at risk from marine debris,” Dr Jennifer Lavers from the University of Tasmania, Australia and the first author of the paper says in a release.

With the 17.6 tonnes of plastic waste found on the island accounting for only about 2 seconds of global production of plastic, the amount of waste that would get accumulated even in remote islands is bound to increases and further impact the exceptional natural beauty and biodiversity of these islands.

Soon, plastic can be biodegraded more efficiently

Degrading plastic-Optimized

A close-up of wax worm next to biodegraded holes in a polyethylene plastic shopping bag used in the experiment. – Photo: Paolo Bombelli

Polyethylene, which is a widely used plastic and the toughest to be degraded, has met its match. Larvae of wax moth Galleria mellonella has been shown to degrade polyethylene into ethylene glycol at an unbelievably fast rate.

Other methods of biodegrading polyethylene using a culture of fungus Penicillium simplicissimum after treating with nitric oxide and bacterium Nocardia asteroids take a very long time (three months and 4-7 months respectively) and are not efficient either.

Polyethylene is the world’s most widely used plastic (over 60 million tonnes are produced worldwide annually), primarily used to make films used in packaging and plastic bags. Very small amounts of plastic bags get recycled; they mostly end up in the ocean. It takes a very long time — 100-400 years — for polyethylene bags to be degraded.

In a paper published on April 24 in the journal Current Biology, Federica Bertocchini from the Institute of Biomedicine and Biotechnology of Cantabria (CSIC), Spain and her team found that wax worms kept in a polyethylene shopping bag formed holes in about 40 minutes. In about 12 hours, nearly 100 wax worms kept in the bag were able to reduce the mass of plastic by 92 mg. About 2.2 holes were made per worm per hour.

To confirm that the breakdown of polyethylene was not due to mechanical action of chewing, the researchers meshed the caterpillars and applied the paste on a polyethylene film. Compared with films that were not treated with the caterpillar paste, there was 13% loss of mass at the end of 14 hours in the case of the film treated with the paste. Though the loss of mass using the paste is less than when the worms were in direct contact with the polyethylene film, the average degradation rate of 0.23 mg per cm per hour is “markedly higher” than what was reported earlier.

Spectroscopic analysis carried out by the researchers showed that untreated parts of the film showed signatures of polyethylene while the treated parts of the film carried ethylene glycol signature, thus confirming the biodegradation of polyethylene into ethylene glycol.

Further studies showed that parts of the film that were treated with the paste had greater surface roughness, suggesting that the physical contact of the paste changed the integrity of the polymer surface.

“It was a chance discovery,” Dr. Bertocchini told me over telephone. “I am a beekeeper and was clearing the beehives as they were infested with worms. I put the worms in a plastic shopping bag. But soon I found the bag was full of holes and the worms were outside the bag.”

Wax worms live as parasites in bee colonies. They lay their eggs inside the hives which then hatch and grow eating the beeswax. “There is a lot of similarity in chemical structure of polyethylene and beeswax. The caterpillars are breaking down the chemical bonds of polyethylene like they do with beeswax,” she says.

“There is a possibility that the one or more enzymes of the caterpillar is causing the degradation,” she says. “We have so far not conducted any studies to analyse the faeces of the worms that made the holes. We have also not analysed the metabolism of the worms eating beeswax.”

The only catch is that the worms remain as caterpillars for only a few days. So using the caterpillars to biodegrade polyethylene might not be possible. Though the caterpillar paste can be used for biodegradation, isolating the enzymes and using them is the way to go forward for commercial-scale biodegration of polyethylene.

The team is planning to isolate the molecules responsible for degradation and study the biodegradation efficiency.

Published in The Hindu on April 24, 2017

Plastic waste found in fish meant for human consumption


As per a 2015 paper, plastic waste was found in fish from Indonesia and textile fibre in fish from California.

In a first, researchers have found plastic debris in fishes in Indonesia and California, U.S. meant for human consumption, raising a red flag for human health. According to a paper published in September 2015 in the journal Scientific Reports, man-made debris was found in 28% of individual fish and in 55% of all species samples from markets in Makassar, Indonesia. In the case of the U.S., man-made debris was found in 25% of individual fish and in 67% of all species. Anthropogenic debris was also found in 33% of individual shellfish sampled.

While all anthropogenic debris found in the digestive tracts of fish and whole shellfish sampled in Indonesia contained plastic, it was fibre from textiles in the case of fish from California (there was only 20% plastic waste). The difference in the type of man-made found in fish in the two countries reflects the waste-management practices in the two countries.

In Indonesia, of the 76 fish from 11 different species collected from a market, 21 (28%) had anthropogenic debris in the digestive tract. Of the 11 fish species collected, plastic waste was found six species. At 56%, the Indian mackerel had the most amount of debris, followed by herring at 29%.  Totally 105 plastic pieces were removed from the fish. The average size was 3.5 mm in length and up to 4.5 mm in width.

In the case of fish from 64 fish from 12 different species taken from California, 16 (25%) fish and four of 12 shellfish had man-made fibre from textiles waste inside the digestive tract; six fish had plastic waste. Totally, 30 individual fibre pieces were removed from the fish. The number of anthropogenic particles in individual fish was up to 10 pieces. The researchers were unable to know if the textile fibre found inside fish was synthetic or natural. The average length of fibre 5.5 mm and width was up to 0.05 mm.

“As anthropogenic debris is associated with a cocktail of priority pollutants, some of which can transfer to animals upon ingestion, this work supports concern that chemicals from anthropogenic debris may be transferring to humans via diets containing fish and shellfish, raising important questions regarding the bioaccumulation and biomagnification of chemicals and consequences for human health,” notes the paper.

Small-sized man-made debris has been shown to cause “physical damage leading to cellular necrosis, inflammation and lacerations of tissues in the gastrointestinal (GI) tract. As such, anthropogenic marine debris may cause physical harm to humans when debris is ingested via seafood,” the paper says.

Plastic debris is widely present in oceans. According to a February 2015 study published in Science, eight million tonnes of plastic entered the ocean from around the world in 2010. China was the worst offender contributing 8.82 million tonnes of plastic per year; India was ranked 12th with 0.60 million tonnes.

It was always known that of the huge plastic waste that enters the world oceans, certain percentage of degraded plastic in the form of tiny particles would be consumed by fishes and other marine animals and ultimately enter the food chain.

Plastic degrading bacteria isolated

PET bottle

The bacteria was able to almost completely degrade a thin film of PET film in six weeks at 30 degree C. – Photo: R. Prasad

A bacterium species capable of breaking down plastic — poly(ethylene terephthalate), or PET — has been identified by a team of Japanese researchers.  The bacterium uses two enzymes in sequence to break down the highly biodegradable-resistant polymer PET.  The results are published today (March 11) in the journal Science.

Except for rare instances of two fungi that have been found to grow on a mineral medium of PET yarns, there are no reports of any bacteria biologically degrading PET or growing on the chemically inert substance.

Shosuke Yoshida, the first author of the paper from the Department of Applied Biology, Kyoto Institute of Technology, Kyoto, and others collected 250 debris-contaminated samples from a PET bottle recycling site. They looked for microorganisms that relied on PET film as a primary source of carbon for growth.  At first they identified a distinct microbial consortium that contained a mixture of bacteria species that degraded the PET film surface at 30 degree C; 75 per cent of the PET film surface was broken down into carbon dioxide at 28 degree C.

From the microbial consortium, the researchers isolated a unique bacterium — Ideonella sakaiensis 201-F6 — that could almost completely degrade a thin film of PET in a short span of six weeks at 30 degree C. “The PET film was damaged extensively and almost completely degraded after six weeks at 30 degree C,” they note.

The bacterium degrades PET using two enzymes that act on it in sequence.  First, the bacterium adheres to PET and produces an intermediate substance through hydrolysis.  The second enzyme then works with water and acts on this intermediate substance to produce the two monomers — ethylene glycol and terephthalic acid — that are used for making PET through polymerisation.

Human-made PET has been littering the environment for the last 70 years and in 2013 56 million tonnes of PET were produced worldwide. Since PET came into being only 70 years ago, a pertinent question is how this distinct bacterium evolved in the environment. Also, it is not clear what natural processes were at play for the two unique enzymes capable of breaking down PET in sequential steps to evolve.

“PET enrichment in the sampling site and the enrichment culture potentially promoted the selection of a bacterium that might have obtained the necessary set of genes through lateral gene transfer,” they write.

“Did both hydrolytic enzymes evolve during that relatively short period to enable the bacterium to access a novel carbon source and hence provide an advantage for survival? Examples for such rapid natural evolution are scarce,” says Uwe T. Bornscheuer from Institute of Biochemistry, Greifswald University, Germany in an accompanying Perspective article.

Published in The Hindu on March 11, 2016



8 million tonnes of plastic waste entered oceans in 2010

For the first time, researchers have quantified the amount of plastic waste entering the ocean from land. In 2010, an estimated eight million tonnes of plastic waste made its way into the ocean; it is nearly the amount of plastic generated globally in 1961. The results of the study were published in the journal Science on February 13, 2015.

Most of the plastic waste that enters the ocean is on account of plastic litter and mismanaged plastic waste systems in several countries. The total amount that ended up in the ocean would have been much higher as the study did not take into account the contribution from other sources like fishing activities or at-sea vessels.

Twenty countries accounted for 83 per cent of mismanaged plastic waste that entered the ocean. The list of countries that pumped the greatest amount of waste into the ocean was arrived at by taking into account the population and quality of waste management systems in place.

India, with 0.60 million tonnes per year of mismanaged plastic waste, is ranked 12th. China ranks no. 1 with 8.82 million tonnes per year of mismanaged plastic waste. There are 11 Asian and Southeast Asian countries in the list, including Sri Lanka, Bangladesh, Pakistan and Burma.

The cumulative amount of plastic debris that would enter the ocean in the next decade will be more than double the 2010 figure in the absence of any improvement to waste management systems in the 192 coastal countries. In 2010, 275 million tonnes of plastic waste was generated in the world’s 192 coastal countries. It is very unlikely that a global “peak waste” will be reached before 2100.

With a 50-per-cent improvement in waste disposal in the 20 top-ranked countries, the mass of mismanaged waste will fall by 41 per cent by 2025.

Alternatively, a 26-per-cent decrease in waste can be achieved by 2025 if per capita waste generation is reduced to the 2010 average (1.7 kg per day) in the 91 countries that exceed it.

Published in The Hindu on February 13, 2015

Editorial: The menace of plastic waste

If there is one type of municipal solid waste that has become ubiquitous in India and most developing countries, and largely seen along the shores and waterways of many developed countries, it is plastic waste. Much of it is not recycled, and ends up in landfills or as litter on land, in waterways and the ocean. For the first time, researchers have estimated the amount of plastic that makes its way into the oceans. While the estimate of eight million tonnes of plastic being dumped into the oceans by 192 coastal countries in 2010 may appear staggeringly high, in reality the quantity would be many times more. Besides estimating the total quantity, a paper published recently in the journal Science has identified the top 20 countries that have dumped the most plastic waste into the oceans. At twelfth position, India is one of the worst performers. It has dumped up to 0.24 million tonnes of plastic into the ocean every year; the amount of mismanaged plastic waste per year is 0.6 million tonnes. In the case of China, the No. 1 polluter, the coastal population sends up to 3.53 million tonnes of plastic waste into the oceans each year. Besides the 11 Asian and South East Asian countries, the U.S. figures in the list.

A study published in December 2014 estimated the quantity of plastic floating in the ocean at nearly 270,000 tonnes. This is but a fraction of the total that finds its way into the oceans. Other studies suggest that the surface of the water is not its final resting place. Alarmingly, an unknown quantity of degraded plastic in the form of particles enters the food chain. Besides affecting marine life, plastic that gets into the food chain has serious health implications for humans. With the latest study estimating that the annual input into the oceans is set to double by 2025, there is an urgent need to tackle the problem. A two-pronged approach has to be adopted by the worst polluters to reduce per capita plastic waste generation and cut the amount of mismanaged waste by employing better waste management practices. Recycling is the best available way to tackle the waste, though it is not the ideal solution. India, which hardly recycles plastic waste, has its task cut out. It dumps a huge quantity into the ocean although it generates a relatively small amount of this waste per person — 3 per cent of 0.34 kg per person a day of all solid waste generated. The huge population offsets the advantage of low plastic consumption in the country. Cutting down on the use of plastic should also begin in earnest, and the first item that has to be targeted is the single-use plastic bag. The Union government recently refused to ban the manufacture of single-use plastic bags; the least it could do to reduce consumption is to make such bags expensive, employing the same rationale that has been applied for tobacco products that are taxed heavily to reduce consumption.

Published in The Hindu on February 17, 2015

Editorial: The cost of convenience of plastic bags

Despite several committees constituted by the Union government highlighting the many problems posed by thin, non-biodegradable, single-use plastic bags, and a body of evidence also indicating their ill-effects, the government emphatically stated recently that there would be “no ban on manufacture and use of plastic bags” in the country. But such a ban is already in place in a few States. Unfortunately, the other viable alternative of levying charges or raising taxes to curb its use was overlooked. The stand taken by the government is in stark contrast to the European Union’s decision. In a commendable move, EU member-states decided last month to cut the number of lightweight plastic bags consumed per person in a year. The member-countries would either limit the number of bags used to 90 per person a year by 2019 and 40 bags by 2025, or charge for all bags by 2018. Even in a country where plastic manufacturers constitute a powerful lot, in September this year California decided to ban single-use plastic bags from July 2015; though many cities have a similar ban, California is the first State in the U.S. to do so. Several countries that have either banned it or made it chargeable have seen a precipitous drop within a short time in the number of thin bags used. For instance, in 2002, Ireland witnessed a 95 per cent reduction in plastic bag litter once tax on such material was levied. It is proven beyond doubt that mandatory charge on single-use bags is a potent tool to reduce consumption. There is no reason why India cannot look at this option. After all, reducing litter should be the first goal under the Swachh Bharat Mission.

For a few minutes of convenience, people mindlessly turn to single-use plastic bags, apparently oblivious to its persistence in the environment, both on land and in the oceans, for hundreds of years. Besides ending up in landfills or as litter in all possible places, they very often clog drainage systems and even prevent the recharge of groundwater aquifers. The bigger ramification is the death of cattle and a huge number of marine animals every year due to plastic bag ingestion. The production process is energy-intensive. It is for these reasons that in 2012 the Supreme Court observed that in the absence of tough measures, the “next generation will be threatened with something more serious than the atom bomb”. It is strange and surprising that in a country where reuse and recycling are part of the ethos, the rampant use of disposable plastic bags has become second nature. At a time when solid waste management even for biodegradable waste is non-existent, it is naive to think of ever managing single-use bag waste.

Published in The Hindu on December 18, 2014