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GT/ Cooling down solar cells, naturally

Energy & green technology biweekly vol.38, 18th November — 2nd December

TL;DR

  • Too much sun and too much heat can reduce the efficiency of photovoltaics. A solar farm with optimally spaced panels facing the correct direction could cool itself through convection using the surrounding wind. Researchers explored how to exploit the geometry of solar farms to enhance natural cooling mechanisms.
  • A light-activated catalyst efficiently converts ammonia into clean-burning hydrogen using only inexpensive raw materials.
  • An interdisciplinary team of researchers has developed a potential breakthrough in green aviation: a recipe for a net-zero fuel for planes that will pull carbon dioxide (CO2) out of the air.
  • Aquifer thermal energy storage systems can largely contribute to climate-friendly heating and cooling of buildings: Heated water is stored in the underground and pumped up, if needed. Researchers have now found that low-temperature aquifer thermal energy storage is of great potential in Germany. This potential is expected to grow in future due to climate change.
  • A new method for describing energy loss in organic solar cells has paved the way for building better and more efficient devices.
  • Researchers have discovered a way to chemically recycle PVC into usable material, finding a way to use the phthalates in the plasticizers — one of PVC’s most noxious components — as the mediator for the chemical reaction.
  • Researchers have found an innovative way to rapidly remove hazardous microplastics from water using magnets.
  • Mangroves are the salt-tolerant shrubs that thrive in the toughest of conditions, but according to new UniSA research, mangroves are also avid coastal protectors, capable of surviving in heavy metal contaminated environments.
  • Almost 200 species of bacteria colonize microfibers in the Mediterranean Sea, including one that causes food poisoning in humans, according to a new study.
  • A new study says that moving the world energy system away from fossil fuels and into renewable sources will generate carbon emissions by itself, as construction of wind turbines, solar panels and other new infrastructure consumes energy — some of it necessarily coming from the fossil fuels we are trying to get rid of. But if this infrastructure can be put on line quickly, the study asserts, those emissions would dramatically decrease, because far more renewable energy early on will mean far less fossil fuel needed to power the changeover.
  • And more!

Green Technology Market

Green technology is an applicable combination of advanced tools and solutions to conserve natural resources and environment, minimize or mitigate negative impacts from human activities on the environment, and ensure sustainability development. Green technology is also referred to as clean technology or environmental technology which includes technologies, such as IoT, AI, analytics, blockchain, digital twin, security, and cloud, which collect, integrate, and analyze data from various real-time data sources, such as sensors, cameras, and Global Positioning System (GPS).

Green technology, also known as sustainable technology, protects the environment by using various forms of sustainable energy. Some of the best examples of green technologies include solar panels, LED lighting, wind energy, electric vehicles, vertical farming, and composting.

The global Green Technology and Sustainability market size to grow from USD 11.2 billion in 2020 to USD 36.6 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 26.6% during the forecast period. The growing consumer and industrial interest for the use of clean energy resources to conserve environment and increasing use of Radio Frequency Identification sensors across industries are driving the adoption of green technology and sustainability solutions and services in the market.

The blockchain segment is estimated to grow at the highest CAGR: Energy-intensive cryptocurrency mining has caused a spike in carbon emission, and hence blockchain is capable of driving innovation in the field of green technology.

Latest Research

Viewing convection as a solar farm phenomenon broadens modern power predictions for solar photovoltaics

by Sarah E. Smith, Brooke J. Stanislawski, Byron Kasey Eng, Naseem Ali, Timothy J Silverman, Marc Calaf, Raúl Bayoán Cal in Journal of Renewable and Sustainable Energy

A bright, sunny, cloudless day might seem like the optimal setting for solar cells. But too much sun, and too much heat, can actually reduce the efficiency of photovoltaics.

As operating temperature rises by 1 degree Celsius, traditional silicon-based solar cells will lose about 0.5% efficiency. In a typical photovoltaic plant, where modules operate nearly 25 degrees Celsius above the ambient temperature, energy losses can reach 12%.

Monitoring equipment present at Denver Federal Center (DFC) as adapted from Eng: (a) north-facing view of plant and weather tower; (b) panel surface thermocouple placement; (c) apogee radiometer placement.

This necessitates effective cooling measures for solar farms. Researchers from Portland State University, the University of Utah, and the National Renewable Energy Laboratory explored how to exploit the geometry of solar farms to enhance natural cooling mechanisms.

Some modern cooling methods force wind or water to interact with solar panel surfaces, while others employ specific materials with less thermal sensitivity. However, these techniques require significant resources to operate. In contrast, a solar farm with optimally spaced panels facing the correct direction could cool itself through convection using the surrounding wind.

Geometric array variations considered.

The team improved models that calculate how much energy a given solar plant will produce based on factors such as material, environmental conditions, and panel temperature. They specifically focused on the geometry of solar farms, or how much “gappy-ness” was present between the panels.

“Our hypothesis was that the most precise estimate of solar plant convection, and ultimately production efficiency, must consider the farm as a whole and all possible configuration changes,” said author Sarah Smith, of Portland State University.

Wind tunnel panel construction: (a) schematic of panel layers; (b) sideview of the assembled panel.

By design, it is rare that any two solar plants have the same setup. Each is uniquely designed to optimize solar irradiance and conform to its surrounding environment. For example, the tilt of solar panels changes with latitude and their height varies with vegetation. Spacing of rows often depends on how much land is available.

“This means that the heat-removing wind flow will also move differently throughout each solar plant based on its arrangement, ultimately changing how efficiently heat is removed from module surfaces,” said Smith.

Schematic of the lacunarity volume definition and box of size ri (yellow cube): outer volume is the total space considered for a given solar array (enlarged for clarity); red arrows represent gliding directions.

The researchers performed wind tunnel experiments and high-resolution simulations and collected real-world data to corroborate their model. They investigated photovoltaic heating and cooling with variations in module height, row spacing, angle, and wind. Raising the height of solar cells and increasing the spacing between panel rows increased power output by 2% to 3%.

“This correlation between geometry and efficiency is a huge step toward predicting convective cooling for solar farms based on their inherently unique arrangements,” said Smith. “It paves the way for more accurate energy generation and cost prediction models in industry.”

Earth-abundant photocatalyst for H 2 generation from NH 3 with light-emitting diode illumination

by Yigao Yuan, Linan Zhou, Hossein Robatjazi, Junwei Lucas Bao, Jingyi Zhou, Aaron Bayles, Lin Yuan, Minghe Lou, Minhan Lou, Suman Khatiwada, Emily A. Carter, Peter Nordlander, Naomi J. Halas in Science

Rice University researchers have engineered a key light-activated nanomaterial for the hydrogen economy. Using only inexpensive raw materials, a team from Rice’s Laboratory for Nanophotonics, Syzygy Plasmonics Inc. and Princeton University’s Andlinger Center for Energy and the Environment created a scalable catalyst that needs only the power of light to convert ammonia into clean-burning hydrogen fuel.

The research follows government and industry investment to create infrastructure and markets for carbon-free liquid ammonia fuel that will not contribute to greenhouse warming. Liquid ammonia is easy to transport and packs a lot of energy, with one nitrogen and three hydrogen atoms per molecule. The new catalyst breaks those molecules into hydrogen gas, a clean-burning fuel, and nitrogen gas, the largest component of Earth’s atmosphere. And unlike traditional catalysts, it doesn’t require heat. Instead, it harvests energy from light, either sunlight or energy-stingy LEDs.

The pace of chemical reactions typically increases with temperature, and chemical producers have capitalized on this for more than a century by applying heat on an industrial scale. The burning of fossil fuels to raise the temperature of large reaction vessels by hundreds or thousands of degrees results in an enormous carbon footprint. Chemical producers also spend billions of dollars each year on thermocatalysts — materials that don’t react but further speed reactions under intense heating.

“Transition metals like iron are typically poor thermocatalysts,” said study co-author Naomi Halas of Rice. “This work shows they can be efficient plasmonic photocatalysts. It also demonstrates that photocatalysis can be efficiently performed with inexpensive LED photon sources.”

“This discovery paves the way for sustainable, low-cost hydrogen that could be produced locally rather than in massive centralized plants,” said Peter Nordlander, also a Rice co-author.

The best thermocatalysts are made from platinum and related precious metals like palladium, rhodium and ruthenium. Halas and Nordlander spent years developing light-activated, or plasmonic, metal nanoparticles. The best of these are also typically made with precious metals like silver and gold.

Following their 2011 discovery of plasmonic particles that give off short-lived, high-energy electrons called “hot carriers,” they discovered in 2016 that hot-carrier generators could be married with catalytic particles to produce hybrid “antenna-reactors,” where one part harvested energy from light and the other part used the energy to drive chemical reactions with surgical precision.

Halas, Nordlander, their students and collaborators have worked for years to find non-precious metal alternatives for both the energy-harvesting and reaction-speeding halves of antenna reactors. The new study is a culmination of that work. In it, Halas, Nordlander, Rice alumnus Hossein Robatjazi, Princeton engineer and physical chemist Emily Carter, and others show that antenna-reactor particles made of copper and iron are highly efficient at converting ammonia. The copper, energy-harvesting piece of the particles captures energy from visible light.

A reaction cell (left) and the photocatalytic platform (right) used on tests of copper-iron plasmonic photocatalysts for hydrogen production from ammonia at Syzygy Plasmonics in Houston. All reaction energy for the catalysis came from LEDs that produced light with a wavelength of 470 nanometers.

“In the absence of light, the copper-iron catalyst exhibited about 300 times lower reactivity than copper-ruthenium catalysts, which is not surprising given that ruthenium is a better thermocatalyst for this reaction,” said Robatjazi, a Ph.D. alumnus from Halas’ research group who is now chief scientist at Houston-based Syzygy Plasmonics. “Under illumination, the copper-iron showed efficiencies and reactivities that were similar to and comparable with those of copper-ruthenium.

Syzygy has licensed Rice’s antenna-reactor technology, and the study included scaled-up tests of the catalyst in the company’s commercially available, LED-powered reactors. In laboratory tests at Rice, the copper-iron catalysts had been illuminated with lasers. The Syzygy tests showed the catalysts retained their efficiency under LED illumination and at a scale 500 times larger than lab setup.

“This is the first report in the scientific literature to show that photocatalysis with LEDs can produce gram-scale quantities of hydrogen gas from ammonia,” Halas said. “This opens the door to entirely replace precious metals in plasmonic photocatalysis.”

“Given their potential for significantly reducing chemical sector carbon emissions, plasmonic antenna-reactor photocatalysts are worthy of further study,” Carter added. “These results are a great motivator. They suggest it is likely that other combinations of abundant metals could be used as cost-effective catalysts for a wide range of chemical reactions.”

Magnesium hydride slurry: A potential net-zero carbon dioxide emitting aviation fuel

by Yi Jie Wu, Jake Scarponi, Adam Powell, Jagannath Jayachandran in Fuel

An interdisciplinary team of researchers at Worcester Polytechnic Institute (WPI) has developed a potential breakthrough in green aviation: a recipe for a net-zero fuel for planes that will pull carbon dioxide (CO2) out of the air. The research, which used sophisticated computational modeling and analysis, was recently published.

Led by Jagan Jayachandran, assistant professor of aerospace engineering, and Adam Powell, associate professor of mechanical and materials engineering, the work helps address an urgent climate change problem. Aviation accounts for approximately 2.5% of all global greenhouse emissions, according to the International Council on Clean Transportation (ICCT), and that number is only expected to increase.

“As aviation continues to grow, so will the industry’s emissions, says Powell. “We need to think out of the box and look at sustainable materials that will contribute to a long-term solution toward reducing the transportation sector’s carbon footprint.”

Through modeling and computation analysis, Jayachandran and Powell developed a formula for a fuel that consists of magnesium, a mineral that is found all over the globe, most abundantly in the world’s oceans. A slurry of magnesium hydride — a chemical compound made up of magnesium and hydrogen — mixed with hydrocarbon fuel would burn to produce CO2, water vapor and magnesium oxide (MgO) nanoparticles. The magnesium hydride fuel would also give planes the range for long-haul flights — e.g., from Boston to Tokyo — something that has been a challenge for other sustainable aviation fuels to provide. That longer range is achieved, in part, due to the chemical properties of the slurry — a lower volume of it is needed for combustion than a typical aviation fuel.

“We found this fuel would have up to 8% more range than other today’s jet fuel, and more than two to three times longer range than liquid hydrogen or ammonia which other researchers have proposed as sustainable fuels,” said Jayachandran.

The Department of Energy describes a sustainable aviation fuel as a “biofuel used to power aircraft that has similar properties to conventional jet fuel but with a smaller carbon footprint.” These biofuels have been made from resources including corn grain, algae, forestry, and agricultural residues, among others. Using a biofuel as the hydrocarbon in this slurry with magnesium hydride could potentially lead to net negative emissions.

The research was supported by a WPI TRIAD Seed Grant, a university award intended to encourage and promote interdisciplinary collaboration and innovation. Jayachandran and Powell plan to further their research through physical experiments with samples of the fuel, and are also pursuing potential funding from a federal agency. In addition, they hope this work can inspire others and contribute to a more sustainable world.

Noting the promise of research to mitigate emissions and other climate threats, Powell said, “we hope our work, which opens up a new category of sustainable aviation fuel will spark the imagination of other researchers. The sky’s the limit.”

Potential of low-temperature aquifer thermal energy storage (LT-ATES) in Germany

by Ruben Stemmle, Vanessa Hammer, Philipp Blum, Kathrin Menberg in Geothermal Energy

Aquifer thermal energy storage systems can largely contribute to climate-friendly heating and cooling of buildings: Heated water is stored in the underground and pumped up, if needed. Researchers of Karlsruhe Institute of Technology (KIT) have now found that low-temperature aquifer thermal energy storage is of great potential in Germany. This potential is expected to grow in future due to climate change. The study includes the so far most detailed map of potential aquifer storage systems in Germany.

More than 30 percent of domestic energy consumption currently consumed in Germany is used for heating and cooling buildings. Decarbonization of this sector could therefore lead to major greenhouse gas emission reductions and largely contribute to climate protection. Aquifer thermal energy storage systems, i.e. water-bearing layers in the underground, are suited well for the seasonal storage and flexible use of heat and cold. Water has a high capacity of storing thermal energy. The surrounding rocks have an insulating effect. Underground aquifer thermal energy storage systems are accessed by boreholes and used to store heat from solarthermal plants or waste heat from industrial facilities. If required, the heat can be pumped up again. Such storage systems can be combined perfectly with heat networks and heat pumps. Near-surface low-temperature aquifer thermal energy storage systems (LT-ATES) have proved to be particularly efficient. As the water temperature is not much higher than the temperature of the environment, little heat is lost during storage.

Schematic operation principle of ATES in cooling mode (left) and in heating mode (right).

Researchers from KIT’s Institute of Applied Geosciences (AGW) and the Sustainable Geoenergy Junior Research Group have now identified the regions suited for low-temperature aquifer thermal energy storage in Germany.

Criteria for an efficient LT-ATES operation include favorable hydrogeological conditions, such as the productivity of groundwater resources and groundwater flow velocity,” Ruben Stemmle explains. The member of AGW’s Engineering Geology Group and first author of the study adds: “Moreover, energy consumption for heating and cooling must be balanced. It can be approximated by the ratio of heating and cooling degree days.”

Researchers have combined hydrogeological and climate criteria in a spatial analysis. They found that 54 percent of the German territory will be suited very well or well for LT-ATES in the upcoming decades. These potentials are largely concentrating on the North German Basin, the Upper Rhine Graben, and the South German Molasse Basin. The corresponding map was generated by the researchers with the help of a geoinformation system (GIS) and a multi-criteria decision analysis.

a Mean ratio of CDDs to HDDs for 2021–2050, b change of mean degree days ratio from 2021–2050 to 2071–2100.

According to the study, the areas suited well or very well for LT-ATES will presumably increase by 13 percent for the period from 2071 to 2100. The large increase of very well-suited regions is attributed to an increasing cooling demand in the future, i.e. it will be due to climate change. However, use of aquifer storage systems is largely restricted in water protection zones, which will reduce the very well or well-suited areas by around eleven percent.

“Still, our study reveals that Germany has a high potential for seasonal heat and cold storage in aquifers,” Stemmle says.

Mitigation and adaptation emissions embedded in the broader climate transition

by Corey Lesk, Denes Csala, Robin Hasse, Sgouris Sgouridis, Antoine Levesque, Katharine J. Mach, Daniel Horen Greenford, H. Damon Matthews, Radley M. Horton in Proceedings of the National Academy of Sciences

First, the bad news: Nothing is free. Moving the world energy system away from fossil fuels and into renewable sources will generate carbon emissions by itself, as construction of wind turbines, solar panels and other new infrastructure consumes energy — some of it necessarily coming from the fossil fuels we are trying to get rid of. The good news: If this infrastructure can be put on line quickly, those emissions would dramatically decrease, because far more renewable energy early on will mean far less fossil fuel needed to power the changeover.

This is the conclusion of a study that for the first time estimates the cost of a green transition not in dollars, but in greenhouse gases.

“The message is that it is going to take energy to rebuild the global energy system, and we need to account for that,” said lead author Corey Lesk, who did the research as a Ph.D. student at the Columbia Climate School’s Lamont-Doherty Earth Observatory. “Any way you do it, it’s not negligible. But the more you can initially bring on renewables, the more you can power the transition with renewables.”

The researchers calculated the possible emissions produced by energy use in mining, manufacturing, transport, construction and other activities needed to create massive farms of solar panels and wind turbines, along with more limited infrastructure for geothermal and other energy sources. Previous research has projected the cost of new energy infrastructure in dollars — $3.5 trillion a year every year until 2050 to reach net-zero emissions, according to one study, or up to about $14 trillion for the United States alone in the same period, according to another. The new study appears to be the first to project the cost in greenhouse gases.

On the current slow pace of renewable infrastructure production (predicted to lead to 2.7 degrees C warming by the end of the century), the researchers estimate these activities will produce 185 billion tons of carbon dioxide by 2100. This alone is equivalent to five or six years of current global emissions — a hefty added burden on the atmosphere. However, if the world builds the same infrastructure fast enough to limit warming to 2 degrees — current international agreement aims to come in under this — those emissions would be halved to 95 billion tons. And, if a truly ambitious path were followed, limiting warming to 1.5 degrees, the cost would be only 20 billion tons by 2100 — just six months or so of current global emissions.

Simulated quantities of renewable deployment and adaptation under the gradual decarbonization pathway.

The researchers point out that all their estimates are probably quite low. For one, they do not account for materials and construction needed for new electric-transmission lines, nor batteries for storage — both highly energy- and resource-intensive products. Nor do they include the cost of replacing gas- and diesel- powered vehicles with electric ones, or making existing buildings more energy efficient. The study also looks only at carbon-dioxide emissions, which currently cause about 60 percent of ongoing warming — not other greenhouse gases including methane and nitrous oxide.

Other effects of the move to renewables are hard to quantify, but could be substantial. All this new high-tech hardware will require not just massive amounts of base metals including copper, iron and nickel, but previously lesser-used rare elements such as lithium, cobalt, yttrium and neodymium. Many commodities would probably have to come from previously untouched places with fragile environments, including the deep sea, African rain forests and fast-melting Greenland. Solar panels and wind turbines would directly consume large stretches of land, with attendant potential effects on ecosystems and people living there.

“We’re laying out the bottom bound,” said Lesk of the study’s estimates. “The upper bound could be much higher.” But, he says, “the result is encouraging.” Lesk said that given recent price drops for renewable technologies, 80 to 90 percent of what the world needs could be installed in the next few decades, especially if current subsidies for fossil-fuel production are diverted to renewables. “If we get on a more ambitious path, this whole problem goes away. It’s only bad news if we don’t start investing in the next 5 to 10 years.”

As part of the study, Lesk and his colleagues also looked at carbon emissions from adapting to sea-level rise; they found that construction of sea walls and moving cities inland where necessary would generate 1 billion tons of carbon dioxide by 2100 under the 2-degree scenario. This, again, would be only part of the cost of adaptation; they did not look at infrastructure to control inland flooding, irrigation in areas that might become drier, adapting buildings to higher temperatures or other needed projects.

“Despite these limitations, we conclude that the magnitude of CO2 emissions embedded in the broader climate transition are of geophysical and policy relevance,” the authors write. “Transition emissions can be greatly reduced under faster-paced decarbonization, lending new urgency to policy progress on rapid renewable energy deployment.”

Quantifying the effect of energetic disorder on organic solar cell energy loss

by Saeed-Uz-Zaman Khan, Jules Bertrandie, Manting Gui, Anirudh Sharma, Wejdan Alsufyani, Julien F. Gorenflot, Frédéric Laquai, Derya Baran, Barry P. Rand in Joule

Organic solar cells are an emerging technology with a lot of promise. Unlike the ubiquitous silicon solar panel, they have the potential to be lightweight, flexible, and present a variety of colors, making them particularly attractive for urban or façade applications. However, continued advancements in device performance have been sluggish as researchers work to understand the fundamental processes underlying how organic solar cells operate.

Now, engineers at Princeton University and King Abdullah University of Science and Technology have described a new way to express energy loss in organic solar cells and have extended that description to make recommendations for engineering the best devices. This breakthrough could reimagine the conventional approach to constructing organic solar cells.

“There was a way that energy loss in organic solar cells was traditionally described and defined. And it turns out that that description was not wholly correct,” said Barry Rand, co-author of the study and associate professor of electrical and computer engineering and the Andlinger Center for Energy and the Environment.

Rand pointed out that the traditional method for describing energy loss did not account for the presence of disorder in an organic solar cell. One type of disorder, dynamic disorder, is caused by the erratic movement of molecules at the micro level, leading to energy loss that is practically unavoidable at most temperatures. The other type, structural or static disorder, is a product of the intrinsic structures of the various materials used in an organic solar cell, as well as their arrangement inside a device. Past research on organic solar cells that did not account for disorder in energy loss calculations yielded values around 0.6 electron volts, regardless of the device’s materials. But when Rand and his team incorporated disorder into the way they calculated energy loss and tested various devices, they found that the level of disorder played an important role in determining the overall energy loss of an organic solar cell.

“As the disorder of a solar cell increases, we see our non-radiative energy loss component — the component that we have control over — grows rapidly,” Rand said. “The non-radiative energy loss grows with the square of the disorder component.”

After demonstrating that increasing disorder causes energy loss to sharply increase in devices, the researchers were able to make recommendations for materials that minimize disorder and therefore lead to more efficient devices. Since scientists can choose the materials they use as well as how to arrange them in an organic solar cell, they have some control over the level of structural disorder in a given device. When engineering an organic solar cell, researchers can focus on creating a homogenous mixture of materials, in which the parts of a film are either all crystalline or all amorphous, or a heterogeneous mixture, in which some parts of a film are crystalline and other parts are amorphous.

Through their work, Rand’s team demonstrated that when it comes to building organic solar cells, homogeneous mixtures reign supreme. For better-performing organic solar cells, Rand said that scientists should use either highly crystalline or highly amorphous materials and avoid mixing the two within a device.

“If you have anything in between, some heterogeneity in which parts of a film are slightly crystalline and some parts are amorphous, that’s when you lose the most energy,” Rand said.

This finding breaks with convention, as researchers previously believed that some level of heterogeneity in solar cell mixtures was beneficial for overall performance. But because Rand’s team found that heterogeneous device mixtures had high levels of disorder and lost significant amounts of energy, he said that their discovery could provide new focus for researchers as they pursue more efficient organic solar cells.

“Heterogeneity has often been the focal point of devices. Some level of crystallinity was thought to be beneficial. But it turns out that that’s not what we saw,” said Rand. He pointed out that many of the top-performing organic solar cells today are composed of highly amorphous films, and suggested that with existing technologies, completely amorphous mixtures are more pragmatic than completely crystalline ones.

Although his team’s research primarily sought to understand the science behind organic solar cells, Rand is hopeful that others can use their work to build more efficient devices and ultimately reach new performance benchmarks for this promising solar technology.

“This discovery is another aspect of organic solar cells that we can add to what we already know, which will help us improve their efficiency going forward,” Rand said.

Using waste poly(vinyl chloride) to synthesize chloroarenes by plasticizer-mediated electro(de)chlorination

by Danielle E. Fagnani, Dukhan Kim, Sofia I. Camarero, Jose F. Alfaro, Anne J. McNeil in Nature Chemistry

PVC, or polyvinyl chloride, is one of the most produced plastics in the United States and the third highest by volume in the world.

PVC makes up a vast amount of plastics we use on a daily basis. Much of the plastic used in hospital equipment — tubing, blood bags, masks and more — is PVC, as is most of the piping used in modern plumbing. Window frames, housing trim, siding and flooring are made of, or include, PVC. It coats electrical wiring and comprises materials such as shower curtains, tents, tarps and clothing. It also has a zero percent recycling rate in the United States.

Now, University of Michigan researchers, led by study first author Danielle Fagnani and principal investigator Anne McNeil, have discovered a way to chemically recycle PVC into usable material. The most fortuitous part of the study? The researchers found a way to use the phthalates in the plasticizers — one of PVC’s most noxious components — as the mediator for the chemical reaction. Their results are published in the journal Nature Chemistry.

“PVC is the kind of plastic that no one wants to deal with because it has its own unique set of problems,” said Fagnani, who completed the work as a postdoctoral researcher in the U-M Department of Chemistry. “PVC usually contains a lot of plasticizers, which contaminate everything in the recycling stream and are usually very toxic. It also releases hydrochloric acid really rapidly with some heat.”

Plastic is typically recycled by melting it down and reforming it into the lower quality materials in a process called mechanical recycling. But when heat is applied to PVC, one of its primary components, called plasticizers, leach out of the material very easily, McNeil says. They then can slip into other plastics in the recycling stream. Additionally, hydrochloric acid releases easily out of PVC with heat. It could corrode the recycling equipment and cause chemical burns to skin and eyes — not ideal for workers in a recycling plant.

What’s more, phthalates — a common plasticizer — are highly toxic endocrine disruptors, which means they can interfere with the thyroid hormone, growth hormones and hormones involved with reproduction in mammals, including humans.

So, to find a way to recycle PVC that does not require heat, Fagnani began exploring electrochemistry. Along the way, she and the team discovered that the plasticizer that presents one of the major recycling difficulties could be used in the method to break down PVC. In fact, the plasticizer improves the efficiency of the method, and the electrochemical method resolves the issue with hydrochloric acid.

“What we found is that it still releases hydrochloric acid, but at a much slower, more controlled rate,” Fagnani said.

Danielle Fagnani used electrochemistry to chemically recycle polyvinyl chloride in a reaction vessel. Image credit: Danielle Fagnani

PVC is a polymer with a hydrocarbon backbone, Fagnani says, composed of single carbon-carbon bonds. Attached to every other carbon group is a chlorine group. Under heat activation, hydrochloric acid rapidly pops off, resulting in a carbon-carbon double bond along the polymer’s backbone. But the research team instead uses electrochemistry to introduce an electron into the system, which causes the system to have a negative charge. This breaks the carbon-chloride bond and results in a negatively charged chloride ion. Because the researchers are using electrochemistry, they can meter the rate at which electrons are introduced into the system — which controls how quickly hydrochloric acid is produced.

The acid can then be used by industries as a reagent for other chemical reactions. The chloride ions can also be used to chlorinate small molecules called arenes. These arenes can be used in pharmaceutical and agricultural components. There is material left from the polymer, for which McNeil says the group is still looking for a use. Fagnani says the study shows how scientists might think about chemically recycling other difficult materials.

“Let’s be strategic with the additives that are in plastics formulations. Let’s think about the during-use and end-of-use from the perspective of the additives,” said Fagnani, who is now a research scientist at Ashland, a company focused on making biodegradable specialty additives to consumer goods such as laundry detergents, sunscreens and shampoos. “Current group members are trying to improve the efficiency of this process even more.”

The focus of McNeil’s lab has been to develop ways to chemically recycle different kinds of plastics. Breaking plastics into their constituent parts could produce non-degraded materials that industry can incorporate back into production.

“It’s a failure of humanity to have created these amazing materials which have improved our lives in many ways, but at the same time to be so shortsighted that we didn’t think about what to do with the waste,” McNeil said. “In the United States, we’re still stuck at a 9% recycling rate, and it’s only a few types of plastics. And even for the plastics we do recycle, it leads to lower and lower quality polymers. Our beverage bottles never become beverage bottles again. They become a textile or a park bench, which then ends up in a landfill.”

Self-assembly of C@FeO nanopillars on 2D-MOF for simultaneous removal of microplastic and dissolved contaminants from water

by Muhammad Haris, Muhammad Waqas Khan, Ali Zavabeti, Nasir Mahmood, Nicky Eshtiaghi in Chemical Engineering Journal

Researchers at RMIT University have found an innovative way to rapidly remove hazardous microplastics from water using magnets.

Lead researcher Professor Nicky Eshtiaghi said existing methods could take days to remove microplastics from water, while their cheap and sustainable invention achieves better results in just one hour. The team says they have developed adsorbents, in the form of a powder, that remove microplastics 1,000 times smaller than those currently detectable by existing wastewater treatment plants. The researchers have successfully tested the adsorbents in the lab, and they plan to engage with industry to further develop the innovation to remove microplastics from waterways.

“The nano-pillar structure we’ve engineered to remove this pollution, which is impossible to see but very harmful to the environment, is recycled from waste and can be used multiple times,” said Eshtiaghi from RMIT’s School of Environmental and Chemical Engineering.

“This is a big win for the environment and the circular economy.”

The researchers have developed an adsorbent using nanomaterials that they can mix into water to attract microplastics and dissolved pollutants. Muhammad Haris, the first author and PhD candidate from RMIT’s School of Environmental and Chemical Engineering, said the nanomaterials contained iron, which enabled the team to use magnets to easily separate the microplastics and pollutants from the water.

“This whole process takes one hour, compared to other inventions taking days,” he said.

Co-lead researcher Dr Nasir Mahmood said the nano-pillar structured material was designed to attract microplastics without creating any secondary pollutants or carbon footprints.

“The adsorbent is prepared with special surface properties so that it can effectively and simultaneously remove both microplastics and dissolved pollutants from water,” said Mahmood from Applied Chemistry and Environmental Science at RMIT.

“Microplastics smaller than 5 millimetres, which can take up to 450 years to degrade, are not detectable and removable through conventional treatment systems, resulting in millions of tonnes being released into the sea every year. This is not only harmful for aquatic life, but also has significant negative impacts on human health.”

The team received scientific and technical support from the Microscopy and Microanalysis Facility and the Micro Nano Research Facility, part of RMIT’s newly expanded Advanced Manufacturing Precinct, to complete their research.

Developing a cost-effective way to overcome these signficant challenges posed by microplastics was critical, Eshtiaghi said.

“Our powder additive can remove microplastics that are 1,000 times smaller than those that are currently detectable by existing wastewater treatment plants,” she said.

“We are looking for industrial collaborators to take our invention to the next steps, where we will be looking at its application in wastewater treatment plants.”

Metallic mangroves: Sediments and in situ diffusive gradients in thin films (DGTs) reveal Avicennia marina (Forssk.) Vierh. lives with high contamination near a lead‑zinc smelter in South Australia

by Farzana Kastury, Georgia Cahill, Ameesha Fernando, Adrienne Brotodewo, Jianyin Huang, Albert L. Juhasz, Hazel M. Vandeleur, Craig Styan in Science of The Total Environment

They are the salt-tolerant shrubs that thrive in the toughest of conditions, but according to new UniSA research, mangroves are also avid coastal protectors, capable of surviving in heavy metal contaminated environments.

The researchers found that grey mangroves (Avicennia marina) can tolerate high lead, zinc, arsenic, cadmium and copper in contaminated sediment — without sustaining adverse health impacts themselves. The study tested the health of grey mangroves living around the Port Pirie smelter. Using leaf chlorophyll content as a proxy to plant health, mangroves were found to be unaffected by metallic contaminants, despite lead and zinc levels being 60 and 151-fold higher than regulatory guidance values. The findings highlight the vital role of mangroves in stabilising polluted regions, and the importance of protecting these ‘coastal guardians’ around the world. The study also coincides with a $3 million federal government initiative to restore mangrove forests in Adelaide’s north.

Dr Farzana Kastury from UniSA’s Future Industries Institute says that ability of mangroves to withstand high metal concentrations make them invaluable in managing polluted environments.

“Mangroves are the ideal eco-defender: they protect our coastlines from erosion and sustain biodiversity, but they also have an incredible ability to trap toxic contaminants in their sediments,” Dr Farzana says.

“Grey mangroves are known for their tolerance of potentially toxic elements, but until now, little has been known about the health of these plants in the Upper Spencer Gulf.

“Our research found that grey mangroves were able to adapt and survive exposure to very high levels of lead and zinc — without adverse health effects in their chlorophyll content — demonstrating how valuable they are to coastal ecosystems.”

Other, ongoing work being done at Port Pirie by UniSA’s Associate Professor Craig Styan suggests there may be 4–7 times more metals stored in the sediments in mangroves than in adjacent unvegetated mudflats. Assoc Prof Styan said that, generally, a greater concentration of metals found in sediments means greater contamination risk for the animals and plants living on/in them.

“The levels of bioavailable metals we measured in the surface sediments in mangrove stands are the same as adjacent mudflats, meaning that although mangroves storing significantly more metals this doesn’t appear to increase the risk of contamination for the many animals that use mangrove habitats,” Prof Styan says.

“People should nonetheless still refer to the SA Department of Health’s advice if they are considering eating fish caught near the smelter.”

Mangroves (along with tidal marshes and seagrasses) are part of the blue carbon ecosystem; when protected or restored, they sequester and store carbon, but when degraded or destroyed, they emit stored carbon into the atmosphere as greenhouse gases. Dr Kastury says understanding the role of mangrove forests in safely stabilising metallic contaminants in highly polluted areas is imperative — not only for South Australian communities, but also around the world.

“Globally, over a third of mangrove forests have disappeared, mostly due to human impact such as reclaiming land for agriculture and industrial development and infrastructure projects,” Dr Kastury says.

“We must protect our mangrove forests so that they can continue their job in protecting our environment.”

Vibrio spp and other potential pathogenic bacteria associated to microfibers in the North-Western Mediterranean Sea

by Maria Luiza Pedrotti, Ana Luzia de Figueiredo Lacerda, Stephanie Petit, Jean François Ghiglione, Gabriel Gorsky in PLOS ONE

Almost 200 species of bacteria colonize microfibers in the Mediterranean Sea, including one that causes food poisoning in humans, according to a new study led by Maria Luiza Pedrotti of Sorbonne Université.

Synthetic and natural microfibers from plastic pollution, the textile industry and fishing activities have increased dramatically in the environment, becoming the most common type of particles in the ocean. These microfibers likely pose a threat to aquatic ecosystems and human health, because once they become colonized by microorganisms, they smell like food and are consumed by marine organisms. Due to their persistence, the microfibers likely build up in marine organisms as they move through the food chain.

Map of the northwestern Mediterranean Sea where seasonal sampling of MFs and seawater was carried out in the coastal area between Nice and Monaco, as well as in the offshore Dyfamed station, and the Haliotis waste water treatment plant.

To find out what types of bacteria live on floating microfibers, researchers used advanced microscopy techniques and DNA sequencing to identify microorganisms living on microfibers collected from the northwestern Mediterranean Sea. They discovered that more than 2,600 cells on average live on each microfiber. These cells belong to 195 bacterial species, including Vibrio parahaemolyticus, a potentially dangerous bacterium that causes food poisoning from seafood.

This new study is the first to report the presence of pathogenic Vibrio species on microfibers in the Mediterranean Sea. The discovery is important for assessing health risks, because the bacterium’s presence can be a threat to bathing and seafood consumption.

The study also raises the question of the environmental risk of microfibers. The increasing amount of persistent plastic waste in the environment may be transporting dangerous bacteria and other pollutants throughout the ocean, thus increasing the risk of contamination compared to short-lived natural particles, such as wood or sediments.

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