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

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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.

Euro VI diesel emission norms can avert nearly 174,000 premature deaths

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Under the current diesel emission norms, there is a wide gap between on-road NOx emissions and certification limits.

Despite tighter nitrogen oxides (NOx) emission norms for diesel cars, buses and trucks in several countries, the actual amount of NOx emitted by diesel vehicles is far more during on-road driving conditions than under laboratory testing carried out at the time of certification. As a result, the excess NOx emitted over certification limits caused nearly 38,000 premature deaths in 2015 in the European Union, China and India; India alone had 9,400 deaths due to excess NOx emissions. Over and above the deaths caused by excess NOx emissions, increased air pollution from diesel NOx caused 107,600 premature deaths globally in 2015.

Diesel vehicles in the 11 major markets (Australia, Brazil, Canada, China, the EU, India, Japan, Mexico, Russia, South Korea, and the U.S.) emitted 13.2 million tonnes of NOx under on-road driving conditions, which is 4.6 million tonnes more than the vehicles’ performance under official laboratory testing. Compared with certification testing, the average on-road NOx emission is 2.3 times higher for light-duty diesel vehicles and 1.45 times the limit for heavy-duty diesel vehicles. Diesel vehicles sold in the 11 markets account for about 80% of global sales.

Adopting and enforcing the stricter Euro VI emission norms could “nearly eliminate” on-road diesel-related NOx emissions and avoid nearly 174,000 premature deaths in 2040, says a study published in Nature on May 15. NOx is a key contributor to outdoor air pollution in the forms of ground-level ozone and fine particulate matter of less than 2.5 micrometre size (PM2.5).

Under the current Euro IV diesel emission norms, there is a wide gap between on-road NOx emissions and certification limits. The excess NOx emissions coming from diesel vehicles gained worldwide attention when 11 million Volkswagen vehicles that contained defeat devices that controlled emissions only at the time of emission testing became known. But what is less known is that the current certification procedure adopted for diesel cars, buses and trucks “legally permits higher” vehicle emissions under normal driving conditions than the certification limits.

Euro VI emission norms have in-service testing, in-use emission monitoring, expanded driving conditions and independent verification.

Heavy diesel vehicles accounted for 86% of on-road emissions and over 75% of excess on-road diesel NOx emissions in 2015, about 90% of which is from China and India, the EU, Brazil and the U.S. In the case of diesel cars, the on-road emissions were 130% more than the certification limits.

Soon, plastic can be biodegraded more efficiently

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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

IIT Kanpur finds more aerosol in the atmosphere produces heavier, widespread rainfall

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Prof. Sachchida Tripathi (left) and Chandan Sarangi studied satellite data spread over 12 years.

Contrary to the general notion that pre-monsoon aerosol loading results in decrease in seasonal rainfall, a long-term (2002-2013) satellite observational study and model-based analysis by researchers from the Indian Institute of Technology (IIT) Kanpur has found that higher aerosol loading results in delayed but more rainfall over Central and Northern India. Higher aerosol loading changes cloud properties in terms of size (both height and width) and microphysics, which results in more rainfall. The results were published in the journal Atmospheric Chemistry and Physics.

Fourteen microns is the agreed raindrop size and until it reaches this size the growth of droplets in the cloud is primarily driven by condensation. When aerosol particles are higher, the number of nucleation sites increases resulting in far too many number of droplets. Under such circumstances, it takes time for the droplets to grow in size through condensation.

More but smaller droplets

“There is an increase in the condensation of water vapour into cloud droplets as the number of aerosol particles increases. But there is a reduction in radius of the drops formed near the cloud base,” says Prof. Sachchida N. Tripathi, from the Department of Civil Engineering, IIT Kanpur and the corresponding author of the paper. This results in delay in the onset and efficiency of the condensation process.

“Although genesis of cloud systems is influenced by various meteorological parameters, aerosols are capable of strongly modifying the cloud structure, dynamics and composition during Indian summer monsoon,” says Chandan Sarangi from the Department of Civil Engineering, IIT Kanpur and the first author of the paper. “Once cloud starts forming due to convection, the presence of more aerosol particles tend to modify the warm phase microphysics as well as ice phase microphysics.”

Two forces — gravity and updraft (vertical velocity) — tend to act on droplets. Under high aerosol loading, rather than falling down as raindrops, the smaller droplets tend to rise upwards in convective atmosphere due to updraft. As the droplets are lifted up they tend to cross the freezing level and turn into ice particles. The process of water droplets turning into ice particles releases more latent heat of freezing and further invigorates the cloud. “Ice turns into water by absorbing heat. Similarly, when water turns into ice it gives off heat. This release of heat further fuels the convection process and the clouds grow taller,” says Sarangi.

Taller clouds

“Satellite data showed that clouds are getting taller and wider under high aerosol loading,” says Prof. Tripathi. As the height of clouds increases, the ice particles generated at top of the cloud come in contact with numerous water and ice particles and become bigger in size. This results in more ice mass in the cloud and eventually more rainfall when the ice particles fall down due to gravity. “There is a delay in the onset of rainfall but once it starts raining it covers a wider area and may be heavier rainfall as well,” Prof. Tripathi says.

In the absence of cloud, aerosol particles tend to absorb solar radiation and this leads to warming or less decrease in temperature with height. As a result, there is suppression of convection leading to further suppression of cloud formation.

As clouds reflect radiation, an increase in aerosol concentration leads to further increase in reflected radiation from the cloud. Also, as the cloud top increases in height, the emitted long wave decreases. “An unit increase in aerosol concentration leads to twice more cooling under cloudy conditions,” Prof. Tripathi says.

Till now scientists have shown that presence of more aerosol in pre-monsoon season may lead to reduction in total monsoon rainfall due to aerosol-solar radiation interactions. “But in our study we looked at co-located measurement of aerosol, cloud and rainfall system. The aerosol-cloud microphysical feedback suggests that higher aerosol loading can enhance the strength of convective rainfall and increase the frequency and intensity of extreme rainfall during Indian summer monsoon,” says Sarangi.

Published in The Hindu on April 22, 2017

Indian researchers use graphene sieves to turn seawater into drinking water

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(From left) Dr. Vasu Siddeswara Kalangi, Jijo Abraham and Prof. Rahul Nair produced molecular sieves by using two techniques to prevent graphene oxide membranes from swelling when in contact with water.

Producing potable water through desalination may become more efficient and less energy intensive if researchers at the University of Manchester are able to successfully use graphene oxide (GO) membranes to filter common salts present in seawater on a commercial scale. When the spacing between two successive graphene oxide sheets was nearly 10 Å (1 angstrom is 0.1 nanometre), more than 97% of table salt (NaCl) was removed from seawater. The removal of salts will be even better when the spacing between two successive sheets is reduced to below 8 Å.

The use of grapene oxide as a molecular sieve to filter common salts from seawater while allowing water to pass through it is already known. But grapene oxide membranes have a tendency to slightly swell when immersed in water and this results in increased spacing between successive sheets (akin to increasing the pore size of a sieve). The increased spacing allows smaller salts to flow through the membrane without being filtered.

A team led by Prof. Rahul Raveendran Nair from the National Graphene Institute, University of Manchester has addressed this problem by developing graphene oxide membranes that do not swell when immersed in water and are able to sieve common salts. In a paper published on April 3 in the journal Nature Nanotechnology, the researchers were able to achieve a desirable interlayer spacing by storing the membranes in high humidity and then physically restraining the membranes from swelling by embedding them in epoxy. “The grapene oxide sheets adjust their interlayer spacing according to the humidity of the air (hygro-responsive property),” Prof. Nair says in an email. Embedding the membranes in epoxy did not alter the rate at which water permeated through the membranes.

Alternative technique

The researchers also tried an alternative technique of adding graphene flakes to graphene oxide to prevent the membranes from swelling. “Though the epoxy coating gives better control over swelling, large area membrane fabrication may be difficult and time-consuming. Producing scalable membranes for desalination application will be possible by adding graphene flakes to graphene oxide instead,” he says.

The higher the ion charge, the stronger it attracts water molecules. So ions with higher free energies have water molecules that are strongly bound. The salt ions with water molecules strongly bound have larger diameter and experience larger barriers to enter the tiny space between the sheets. On the other hand, water molecules have weak hydrogen bonding and need very little energy to strip the surrounding water from the water molecules before entering the tiny space between the graphene oxide layers. So water is able to pass through the membrane more easily.

Making use of energy barriers

“Both KCl and NaCl have similar energy barriers and the [rejection] increases with decreasing spacing. Similar to the case of KCl, even the channel with a spacing of 10 Å has a finite energy barrier, but that barrier increases nearly three fold when the spacing is reduced to below 8 Å,” Prof. Nair says.

In the case of graphene oxide membranes that have graphene flakes (Gr) added to it, the ion permeation rate was suppressed by two orders of magnitude compared with graphane oxide membranes embedded in epoxy. As a result, salt rejection was as high as 97% in the case of Go-Gr membranes when the spacing was nearly 10 Å. There was about 20% reduction in water permeation rate across the membranes.

Treating wastewater

The graphene oxide-graphene flakes membranes are not mechanically strong and are ill-suited for conventional reverse osmosis process. Instead, they can be used for treating wastewater using forward osmosis (and where hydraulic force is not applied).

“Instead of hydraulic pressure, naturally occurring osmotic pressure due to the concentration gradient of salt/molecular solution present on both sides of the membrane is used to drive water molecules across a membrane,” he says. “If we separate wastewater (something needs to be filtered) and sugar solution by using a membrane, then, water from the wastewater solution will flow towards the sugar solution if the concentration of sugar solution is higher than the wastewater solution. This process enables the dilution of sugar solution by pulling the pure water from the wastewater solution to the sugar solution. This technology can be used to separate clean water from the wastewater including sea water. Currently, forward osmosis is mainly using as a pre-treatment to RO process to reduce the energy consumption.”

Preliminary experiments by the team found clogging of the membranes with salt was negligible and the membrane can be recovered to the original state by a simple washing process. They do not anticipate any significant fouling due to the inertness of graphene surface. More studies are needed before the membranes can be commercialised.

Published in The Hindu on April 3, 2017

IISc researchers’ novel, eco-friendly way of recycling e-waste

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Prof. Mahapatra (left) and Prof. Chattopadhyay took advantage of cryo-mill’s ability to crush e-waste into individual components — polymer, oxides and metals.

Indian Institute of Science (IISc) researchers have found a novel way of recycling the mounting pile of electronic waste more efficiently and in an environmentally friendly manner. According to the United National Environmental Programme, about 50 million tonnes of e-waste is generated annually across the world.

The new approach is based on the idea of crushing e-waste into nanosize particles using a ball mill at very low temperature ranging from -50 to -150 degree C.

When crushed to nanosize particles for about 30 minutes, different classes of materials — metals, oxides and polymer — that go into making of electronic items get physically reduced into their constituent phases, which can then be separated without using any chemicals. The use of low-temperature grinding eliminates noxious emission. The results of the study were published in the journal Materials Today.

“The behaviour of individual materials is different when they are pulverised at room temperature. While metal and oxides get mixed, the local temperature of polymer increases during grinding and so the polymer melts instead of breaking,” says Dr. Chandra Sekhar Tiwary from the Materials Engineering Department at IISc and the first author of the paper. “The polymer starts reacting with the rest of the components and forms a chunk. So we can’t separate the individual components.”

“The deformation behaviour at low temperature is very different from room temperature. There are two processes that happen when milling. The polymer material breaks but metals get welded, some sort of solid-state welding resulting in mixing; the welded metals again get broken during milling. At low temperature mixing does not happen,” says Prof. K. Chattopadhyay from the Materials Engineering Department at IISc and the corresponding author of the paper.

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Dr. Tiwary designed the cryo-mill.

There is also a lower limit to which materials can be broken into when e-waste is milled at room temperature. The maximum size reduction that can be achieved is about of 200 nanometre. But in the case of low temperature ball milling the size can be reduced to 20-150 nanometres.

The low-temperature ball mill was designed by Dr. Tiwary. The cryo-mill grinding chamber is cooled using liquid nitrogen and a small hardened steel ball is used for grinding the material in a controlled inert atmosphere using argon gas. “The interface remains clean when broken in an inert atmosphere,” says Prof. Chattopadhyay.

“One of the main purposes of ball milling [at room temperature] is to mix materials. But in the case of ball milling at low temperature we did not observe any mixing; the individual components separate out really well. We wanted to use this property more constructively. So we took two printed circuit boards from optical mouse and milled them for 30 minutes,” recalls Dr. Tiwary, who is currently at Rice University, Houston, Texas.

The polymer becomes brittle when cooled to -120 degree C and ball milling easily breaks it into a fine power. Metals and oxides too get broken but are a bit bigger in size.

Separation of individual components

The milled e-waste powder was then mixed with water to separate the components into the individual classes of materials using gravity. The powder separated into two layers — the polymer floats at the top due to lower density, while metals and oxides of similar size and different density settle at the bottom. The bottom layer when diluted further separated into oxides at the top and metals at the bottom. The oxides and metals were present as individual elements.

“Our low-temperature milling separates the components into single phase components without using any chemicals, which is not possible using other techniques,” says Prof. Chattopadhyay. “Our process is scalable and is environment friendly though it uses higher energy.”

The technology has been patented and transferred to a Bengaluru-based company.

Published in The Hindu on April 2, 2017

Plastic waste found in fish meant for human consumption

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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.