GT/ Unlocking the power of molecular crystals: A possible solution to nuclear waste
Energy & green technology biweekly vol.54, 28th July — 11th August
TL;DR
- A team of researchers has discovered molecular crystals capable of capturing iodine — one of the most common radioactive fission products — and other pollutants. The versatile crystals could be used for nuclear waste management and other energy-related applications and move the world closer to a net-zero future.
- Engineers have created a device that turns sunlight into hydrogen with record-breaking efficiency by integrating next-generation halide perovskite semiconductors with electrocatalysts in a single, durable, cost-effective and scalable device.
- Chemists have demonstrated that water remediation can be powered in part — and perhaps even exclusively — by renewable energy sources.
- New research focuses on optimizing a promising technology called pyrolysis, which can chemically recycle waste plastics into more valuable chemicals.
- A new study has now demonstrated, using field samples from Indonesia, that such rocks pose an increased environmental risk to coastal ecosystems such as seagrass beds, mangroves or coral reefs. The melted plastic decomposes more quickly into microplastics and is also contaminated with organic pollutants.
- Researchers have identified a strategy that can offset the random and unpredictable nature of weather conditions that threaten carbon emission reduction efforts in the shipping sector.
- A bifacial perovskite solar cell, which allows sunlight to reach both sides of the device, holds the potential to produce higher energy yields at lower overall costs.
- Researchers have developed new bioplastics that degrade on the same timescale as a banana peel in a backyard compost bin.
- Scientists reveal the extent of plastic pollution on coral reefs, finding that debris increases with depth, largely stems from fishing activities, and is correlated with proximity to marine protected areas.
- Engineers have developed a cost-effective and environmentally friendly way to remove heavy metals, including copper and zinc, from biosolids. The team’s work advances other methods for heavy-metal removal by recycling the acidic liquid waste that is produced during the recovery phase, instead of throwing it away.
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
Cyclobenzil hydrazones with high iodine capture capacities in solutions and on interfaces
by Alexandra Robles, Maymounah Alrayyani, Xiqu Wang, Ognjen Š. Miljanić in Cell Reports Physical Science
In a world increasingly concerned about the environmental and geopolitical implications of fossil fuel usage, nuclear energy has resurfaced as a subject of great interest. Its ability to generate electricity at scale without greenhouse gas emissions holds promise as a sustainable clean energy source that could bridge society’s transition away from fossil fuels to a net-zero future. However, nuclear power generation does produce radioactive waste. The safe management of nuclear waste remains a crucial challenge that must be addressed to gain public confidence in this transformative power solution.
Now, a team of University of Houston researchers has come up with an innovative solution for nuclear waste management: molecular crystals based on cyclotetrabenzil hydrazones. These crystals, which are based on a groundbreaking discovery made by the team in 2015, are capable of capturing iodine — one of the most common radioactive fission products — in aqueous and organic solutions, and on the interface between the two.
“This last point is particularly salient because iodine capture on interfaces could prevent the iodine from reaching and damaging the specialized paint coatings used in nuclear reactors and waste containment vessels,” said Ognjen Miljanic, professor of chemistry and corresponding author of the paper.
These crystals exhibit an astonishing iodine uptake capacity, rivaling that of porous metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), which were previously deemed the pinnacle of iodine capture materials. Alexandra Robles, the first author of the study and a former doctoral student who based her dissertation on this research, was working with the crystals in Miljanic’s lab when she made the discovery. Her interest in finding a solution for nuclear waste led Robles to investigate using crystals to capture iodine.
“She ended up capturing iodine on the interface between the organic and water layers, which is an understudied phenomenon,” said Miljanic, who added that this exceptional feature provides a crucial advantage. “When the material is deposited between the organic and aqueous layer, it essentially stops the transfer of iodine from one layer to another.”
Not only does this process preserve integrity of reactor coatings and enhance containment, but the captured iodine could also then be moved from one area to another. “The idea here is that you capture it at a place where it’s difficult to manage, and then you release it at a place where it’s easy to manage,” Miljanic said.
The other benefit of this catch-and-release technology is that the crystals can be reused. “If the pollutant just sticks to the regent, the whole thing has to be thrown away,” he said. “And that increases waste and economic loss.” Of course, all of these great potentials still need to be tested in practical applications, which has Miljanic thinking of the next steps.
Miljanic’s team creates these tiny organic molecules containing only carbon, hydrogen and oxygen atoms using commercially available chemicals. Each crystal is a ring-shaped structure with eight linear piece emanating from it, which has led the research team to nickname it “The Octopus.”
“They are quite easy to make and can be produced at a large scale from relatively inexpensive materials without any special protective atmosphere,” said Miljanic.
He estimated that he can currently produce these crystals at the cost of about $1 per gram in an academic lab. In an industrial setting, Miljanic believes the cost would drop significantly. These hungry little crystals are very versatile and can capture more than iodine. Miljanic and his team have used some of them to capture carbon dioxide, which would be another great step toward a cleaner, more sustainable world. In addition, “The Octopus” molecules are closely related to those found in materials used to make lithium-ion batteries, which opens the door to other energy opportunities.
“This is a type of simple molecule that can do all sorts of different things depending on how we integrate it with the rest of any given system,” Miljanic said. “So, we’re pursuing all those applications as well.”
He is excited by the multitude of potential offered by the crystals and looking forward to exploring practical applications. His next goal is to find a partner who will help the scientists explore different commercial aspects. Until then, the researchers are planning to further explore the kinetics and behaviors of the crystal structures to make them even better.
Integrated halide perovskite photoelectrochemical cells with solar-driven water-splitting efficiency of 20.8%
by Austin M. K. Fehr, Ayush Agrawal, Faiz Mandani, et al in Nature Communications
Rice University engineers can turn sunlight into hydrogen with record-breaking efficiency thanks to a device that combines next-generation halide perovskite semiconductors with electrocatalysts in a single, durable, cost-effective and scalable device.
The new technology is a significant step forward for clean energy and could serve as a platform for a wide range of chemical reactions that use solar-harvested electricity to convert feedstocks into fuels. The lab of chemical and biomolecular engineer Aditya Mohite built the integrated photoreactor using an anticorrosion barrier that insulates the semiconductor from water without impeding the transfer of electrons. According to a study, the device achieved a 20.8% solar-to-hydrogen conversion efficiency.
“Using sunlight as an energy source to manufacture chemicals is one of the largest hurdles to a clean energy economy,” said Austin Fehr, a chemical and biomolecular engineering doctoral student and one of the study’s lead authors. “Our goal is to build economically feasible platforms that can generate solar-derived fuels. Here, we designed a system that absorbs light and completes electrochemical water-splitting chemistry on its surface.”
The device is known as a photoelectrochemical cell because the absorption of light, its conversion into electricity and the use of the electricity to power a chemical reaction all occur in the same device. Until now, using photoelectrochemical technology to produce green hydrogen was hampered by low efficiencies and the high cost of semiconductors.
“All devices of this type produce green hydrogen using only sunlight and water, but ours is exceptional because it has record-breaking efficiency and it uses a semiconductor that is very cheap,” Fehr said.
The Mohite lab and its collaborators created the device by turning their highly-competitive solar cell into a reactor that could use harvested energy to split water into oxygen and hydrogen. The challenge they had to overcome was that halide perovskites are extremely unstable in water and coatings used to insulate the semiconductors ended up either disrupting their function or damaging them.
“Over the last two years, we’ve gone back and forth trying different materials and techniques,” said Michael Wong, a Rice chemical engineer and co-author on the study.
After lengthy trials failed to yield the desired result, the researchers finally came across a winning solution.
“Our key insight was that you needed two layers to the barrier, one to block the water and one to make good electrical contact between the perovskite layers and the protective layer,” Fehr said. “Our results are the highest efficiency for photoelectrochemical cells without solar concentration, and the best overall for those using halide perovskite semiconductors.
“It is a first for a field that has historically been dominated by prohibitively expensive semiconductors, and may represent a pathway to commercial feasibility for this type of device for the first time ever,” Fehr said.
The researchers showed their barrier design worked for different reactions and with different semiconductors, making it applicable across many systems.
“We hope that such systems will serve as a platform for driving a wide range of electrons to fuel-forming reactions using abundant feedstocks with only sunlight as the energy input,” Mohite said.
“With further improvements to stability and scale, this technology could open up the hydrogen economy and change the way humans make things from fossil fuel to solar fuel,” Fehr added.
Redox‐Functionalized Semiconductor Interfaces for Photoelectrochemical Separations
by Ki‐Hyun Cho, Raylin Chen, Johannes Elbert, Xiao Su in Small
Using electrochemistry to separate different particles within a solution (also known as electrochemical separation) is an energy-efficient strategy for environmental and water remediation: the process of purifying contaminated water. But while electrochemistry uses less energy than other, similar methods, the electric energy is largely derived from nonrenewable sources like fossil fuels.
Chemists at the University of Illinois Urbana-Champaign have demonstrated that water remediation can be powered in part — and perhaps even exclusively — by renewable energy sources. Through a semiconductor, their method integrates solar energy into an electrochemical separation process powered by a redox reaction, which manipulates ions’ electric charge to separate them from a solution like water. Using this system, the researchers successfully separated and removed dilute arsenate — a derivative of arsenic, which is a major waste component from steel and mining industries — from wastewater.
This work represents proof-of-concept for the applicability of such systems for wastewater treatment and environmental protection.
“Global electrical energy is still predominantly derived from nonrenewable, fossil-fuel-based sources, which raises questions about the long-term sustainability of electrochemical processes, including separations. Integrating solar power advances the sustainability of electrochemical separations in general, and its applications to water purification benefit the water sector as well,” said lead investigator Xiao Su, a researcher at the Beckman Institute for Advanced Science and Technology and an assistant professor of chemical and biomolecular engineering.
Ab Initio Thermochemistry of Highly Flexible Molecules for Thermal Decomposition Analysis
by Hyunguk Kwon, Giannis Mpourmpakis in Journal of Chemical Theory and Computation
It’s lightweight, low-cost, almost endlessly customizable, and concerningly ubiquitous: For all its benefits, plastic — and plastic waste — is a big problem. Unlike glass, which is infinitely recyclable, plastic recycling is challenging and expensive because of the material’s complex molecular structure designed for specific needs.
Globally, an estimated 380 million metric tons of plastic is produced every year. However, only about 9 percent of all plastic waste is recycled, about 12 percent is incinerated, and the rest is discarded in landfills and the natural environment. New research from the lab of Giannis Mpoumpakis, associate professor of chemical and petroleum engineering at the University of Pittsburgh, focuses on optimizing a promising technology called pyrolysis, which can chemically recycle waste plastics into more valuable chemicals. The paper was published recently and featured on the cover of the American Chemical Society (ACS) Journal of Chemical Theory and Computation.
“Pyrolysis is relatively low in cost and can generate high-value products, so it presents an appealing, practical solution,” said Mpourmpakis. “It has already been developed on a commercial scale.The main challenge now is finding optimal operating conditions, given the starting and final chemical products, without needing to rely heavily on trial-and-error experimentation.”
To optimize pyrolysis conditions and produce desired products, researchers typically use thermodynamic calculations based on what’s known as the Gibbs free energy minimization approach. However, the lack of thermochemical data can limit the accuracy of these calculations.
While density functional theory (DFT) calculations are commonly used to obtain precise thermochemical data for small molecules, their application becomes challenging and computationally expensive for the large, flexible molecules that make up waste plastics, especially at elevated temperatures of pyrolysis.
In this study, Mpourmpakis and former postdoc Hyunguk Kwon, who is now a professor at Seoul National University of Science and Technology, developed a computational framework to accurately calculate the temperature-dependent thermochemistry of large and flexible molecules. This framework combines conformational search, DFT calculations, thermochemical corrections, and Boltzmann statistics; the resulting thermochemistry data is used to predict the thermal decomposition profiles of octadecane, a model compound representing polyethylene.
The proposed computational analysis based on first principles offers a significant advancement in predicting temperature-dependent product distributions from plastic pyrolysis. It can guide future experimental efforts in chemical plastic recycling, enabling researchers to optimize pyrolysis conditions and increase the efficiency of converting waste plastics into valuable chemicals.
“The production of plastics is expected to keep increasing, so it’s essential that we find and perfect ways to recycle and reuse plastics without harming the environment,” said Mpourmpakis. “This work, which has been funded by the National Science Foundation, contributes to the development of sustainable waste management strategies and the reduction of plastic pollution, offering potential benefits for both the environment and society.”
Plastiglomerates from uncontrolled burning of plastic waste on Indonesian beaches contain high contents of organic pollutants
by Dwi Amanda Utami, Lars Reuning, Lorenz Schwark, Gernot Friedrichs, Ludwig Dittmer, Ayu Utami Nurhidayati, Ahmad Al Fauzan, Sri Yudawati Cahyarini in Scientific Reports
Plastic waste is a problem on our beaches. Hence, it is largely removed in a coordinated manner within a few weeks. However, it can litter other coasts of the world for many months to years due to unregulated waste disposal. Often the garbage on the beach is simply burned and a special form of plastic waste is created: so-called plastiglomerate. This “rock” is made up of natural components, such as coral fragments, held together by the melted and reconsolidated plastic. A new study by a German-Indonesian research team at Kiel University has now demonstrated, using field samples from Indonesia, that such rocks pose an increased environmental risk to coastal ecosystems such as seagrass beds, mangroves or coral reefs. The melted plastic decomposes more quickly into microplastics and is also contaminated with organic pollutants.
“Until now, there have been rather basic studies describing the formation of plastiglomerates. With our results, we have shown for the first time how plastiglomerate differs from other plastic waste and can make better statements about its environmental impact,” says first author Dr Amanda Utami, who works as a scientist at Indonesia’s largest science organization (BRIN, Badan Riset dan Inovasi Nasional) and came to Kiel on a three-month fellowship. The research work was made possible by funding from the German Academic Exchange Service (DAAD) and cooperation between BRIN and scientists in the Kiel Marine Science (KMS) priority research area at Kiel University.
If plastic waste is burnt directly on the beach, this melting and burning process produces the plastiglomerate “rock,” in whose plastic matrix the carbon chains are degraded. This chemically degraded plastic weathers more rapidly into microplastics through exposure to wind, waves and sediment grains on the beach. The incomplete combustion process releases new pollutants from the plastic that first settle on the plastic and are then released into the environment. These contaminants often have higher ecotoxicological relevance than the parent plastic, are potentially bioavailable, and thus can be introduced and enriched in the food chain.
Scientist Utami collected a total of 25 field samples from beaches on Panjang Island on the western side of the Indonesian island of Java and analyzed them in the laboratory together with researchers from Kiel University. One of them is Dr Lars Reuning, Utami’s scientific host in Kiel and second author of the study: “Our analyses show that Plastiglomerates are contaminated with organic pollutants. Even though further results on bioaccumulation are still pending, they can be classified as potentially carcinogenic to humans.” Reuning is a member of the Paleontology Research Group at the Institute of Geosciences at Kiel University. The working group, led by Professor Miriam Pfeiffer, is also involved in the German Research Foundation’s (DFG) Earth Science Priority Program 2299 “Tropical Climate Variability and Coral Reefs.”
The researchers first differentiated the plastiglomerate samples according to optical criteria into less strongly as well as more strongly melted or burned samples and extracted volatile pollutants with the help of solvents. These analyses, which were carried out in Professor Lorenz Schwark’s Organic Geochemistry Group at the Institute of Geosciences, revealed, for example, contamination with polycyclic aromatic hydrocarbons (PAHs) and phthalates, which are used as plasticizers for plastics. Experts consider both classes of substances to have a high potential for causing cancer.
The research team also used physicochemical methods and comparison with databases to characterize the nature of polymers such as polypropylene (PP) or polyethylene (PE) or their mixtures. They conducted measurements using Fourier transform infrared spectroscopy (FTIR) in the working group of Professor Gernot Friedrichs at the Institute of Physical Chemistry at Kiel University to investigate the degree of weathering. Outcome: Areas that were already visibly more exposed to the burning process also showed a greater degree of weathering and oxidation.
“To better assess environmental damage, we are currently researching the exact composition of the organic pollutants associated with the plastic, such as organophosphorus compounds,” says geochemist Schwark. Also of interest is the tendency of the plastiglomerates to decay easily. “Normally, photo-oxidation by UV light affects the top layer of plastics. But thermo-oxidation by burning the plastic waste significantly alters the internal structures of the material as well,” says geoscientist Reuning.
In the future, numerous coastal ecosystems of tropical waters off Indonesia as well as worldwide will be affected by Plastiglomerates. Studies already show that organic pollutants are also transferred to corals or other marine organisms and can thus have a negative impact on ocean health. Further studies are therefore also looking at other ecosystems such as seagrass beds, mangroves or organisms living in the sediment.
“Compared to normal plastic waste, the unique properties of Plastiglomerates require a specific form of coastal management,” Utami sums up. “If trash from urban areas on tropical beaches were better disposed of and managed, a serious problem could be prevented.”
Mitigating stochastic uncertainty from weather routing for ships with wind propulsion
by James Mason, Alice Larkin, Alejandro Gallego-Schmid in Ocean Engineering
Researchers have identified a strategy that can offset the random and unpredictable nature of weather conditions that threaten carbon emission reduction efforts in the shipping sector.
Erratic weather is a major source of concern for ship owners installing modern sails to reduce carbon emissions. However, new research from The University of Manchester highlights operational strategies that can reduce shipping emissions by up to a quarter, strengthening confidence in sails as a decarbonisation tool. It is estimated that the international shipping sector contributes to 2–3% of global carbon emissions annually and its target to cut carbon by 50% relative to 2008 levels by 2050 falls short of the cuts required in the Paris Climate Agreement, meaning the shipping sector requires urgent global action.
The research calculated carbon emissions from more than 1000 ship departures setting sail from three main shipping routes. The results found that combining modern sail technology with efficient routing systems could provide greater assurances of carbon savings by using the technique that reduces uncertainty from unpredictable weather patterns.
Dr James Mason, previously a postdoctoral researcher and now a visiting academic at the Tyndall Centre for Climate Change Research at The University of Manchester, said: “Current measures to reduce carbon emissions include fitting retrofit technologies, such as wind propulsion technology, where modern sails produce direct energy from the wind to reduce the power consumed by a ship’s engine. Weather routing is also used as an efficient routing system to allow a ship to deviate from standard shipping routes to search for new routes with more favourable winds.
“Current academic methods assume a perfect foresight of future weather rather than accounting for unpredictable winds that are happening in real-time. This can detrimentally reduce the carbon savings from weather routing and could present a real challenge for the shipping sector when trying to meet its climate reduction goals.”
Dr Alejandro Gallego Schmid, a Senior Lecturer at the Tyndall Centre for Climate Change Research, added: “This research provides an insight into which routes are most sensitive to changing weather forecasts when using wind propulsion and assesses a strategy that could help to mitigate the detrimental impact that unpredictable weather conditions can have.”
The strategy mirrors existing routing methods in the sector by updating weather and wind every 12 hours to allow ships to adjust their routes based on the most accurate weather forecast available. To test the strategy, the study simulated 1080 ship departures across eastbound and westbound journeys in the North Sea, South Atlantic Ocean and North Atlantic Ocean, which have voyage times of up to 12 days.
The research found that the method successfully reduced the uncertainty from unpredictable weather and showed that sails and efficient routing can provide annual carbon savings of up to 25%. However, while the method reduces the uncertainty from unpredictable weather, it does not remove it entirely. Wind propulsion and efficient routing can provide maximum carbon savings of up to 29% in ideal conditions and weather uncertainty reduces these savings by 10–20%. Further research is needed to understand how ships can achieve these maximum savings in practice.
Reducing shipping emissions by up to a quarter by using wind propulsion with efficient routing could provide profound benefits to the sector. The research offers a clearer understanding of the potential carbon savings achievable through wind propulsion decarbonisation strategies, without which, objectives in the Paris Climate Agreement may become out of sight.
Highly efficient bifacial single-junction perovskite solar cells
by Qi Jiang, Zhaoning Song, Rosemary C. Bramante, Paul F. Ndione, Robert Tirawat, Joseph J. Berry, Yanfa Yan, Kai Zhu in Joule
A bifacial perovskite solar cell, which allows sunlight to reach both sides of the device, holds the potential to produce higher energy yields at lower overall costs, according to scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).
The dual nature of a bifacial solar cell enables the capture of direct sunlight on the front and the capture of reflected sunlight on the back, allowing this type of device to outperform its monofacial counterparts.
“This perovskite cell can operate very effectively from either side,” said Kai Zhu, a senior scientist in the Chemistry and Nanoscience Center at NREL and lead author of a new paper. His co-authors from NREL are Qi Jiang, Rosemary Bramante, Paul Ndione, Robert Tirawat, and Joseph Berry. Other co-authors are from the University of Toledo.
Past bifacial perovskite solar cell research has yielded devices considered inadequate in comparison to monofacial cells, which have a current record of 26% efficiency. Ideally, the NREL researchers noted, a bifacial cell should have a front-side efficiency close to the best-performing monofacial cell and a similar back-side efficiency.
The researchers were able to make a solar cell where the efficiency under illumination from both sides are close together. The lab-measured efficiency of the front illumination reached above 23%. From the back illumination, the efficiency was about 91%-93% of the front.
Before constructing the cell, researchers relied on optical and electrical simulations to determine the necessary thickness. The perovskite layer on the front of the cell had to be sufficiently thick to absorb most of the photons from a certain part of the solar spectrum, but a perovskite layer that is too thick can block the photons. On the back of the cell, the NREL team had to determine the ideal thickness of the rear electrode to minimize resistive loss.
According to Zhu, simulations guided the design of the bifacial cell, and without that assistance the researchers would have had to experimentally produce cell after cell to determine the ideal thickness. They found the ideal thickness for a perovskite layer is around 850 nanometers. By comparison, a human hair is approximately 70,000 nanometers.
To evaluate the efficiency gained through bifacial illumination, the researchers placed the cell between two solar simulators. Direct light was aimed at the front side, while the back side received reflected light. The efficiency of the cell climbed as the ratio of reflected light to the front illumination increased.
While researchers estimate that a bifacial perovskite solar module would cost more to manufacture than a monofacial module, over time bifacial modules could end up being better financial investments because they generate 10%-20% more power.
Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells
by Hareesh Iyer, Paul Grandgeorge, Andrew M. Jimenez, Ian R. Campbell, Mallory Parker, Michael Holden, Mathangi Venkatesh, Marissa Nelsen, Bichlien Nguyen, Eleftheria Roumeli in Advanced Functional Materials
We use plastics in almost every aspect of our lives. These materials are cheap to make and incredibly stable. The problem comes when we’re done using something plastic — it can persist in the environment for years. Over time, plastic will break down into smaller fragments, called microplastics, that can pose significant environmental and health concerns.
The best-case solution would be to use bio-based plastics that biodegrade instead, but many of those bioplastics are not designed to degrade in backyard composting conditions. They must be processed in commercial composting facilities, which are not accessible in all regions of the country.
A team led by researchers at the University of Washington has developed new bioplastics that degrade on the same timescale as a banana peel in a backyard compost bin. These bioplastics are made entirely from powdered blue-green cyanobacteria cells, otherwise known as spirulina. The team used heat and pressure to form the spirulina powder into various shapes, the same processing technique used to create conventional plastics. The UW team’s bioplastics have mechanical properties that are comparable to single-use, petroleum-derived plastics.
“We were motivated to create bioplastics that are both bio-derived and biodegradable in our backyards, while also being processable, scalable and recyclable,” said senior author Eleftheria Roumeli, UW assistant professor of materials science and engineering. “The bioplastics we have developed, using only spirulina, not only have a degradation profile similar to organic waste, but also are on average 10 times stronger and stiffer than previously reported spirulina bioplastics. These properties open up new possibilities for the practical application of spirulina-based plastics in various industries, including disposable food packaging or household plastics, such as bottles or trays.”
The researchers opted to use spirulina to make their bioplastics for a few reasons. First of all, it can be cultivated on large scales because people already use it for various foods and cosmetics. Also, spirulina cells sequester carbon dioxide as they grow, making this biomass a carbon-neutral, or potentially carbon-negative, feedstock for plastics.
“Spirulina also has unique fire-resistant properties,” said lead author Hareesh Iyer, a UW materials science and engineering doctoral student. “When exposed to fire, it instantly self-extinguishes, unlike many traditional plastics that either combust or melt. This fire-resistant characteristic makes spirulina-based plastics advantageous for applications where traditional plastics may not be suitable due to their flammability. One example could be plastic racks in data centers because the systems that are used to keep the servers cool can get very hot.”
Creating plastic products often involves a process that uses heat and pressure to shape the plastic into a desired shape. The UW team took a similar approach with their bioplastics.
“This means that we would not have to redesign manufacturing lines from scratch if we wanted to use our materials at industrial scales,” Roumeli said. “We’ve removed one of the common barriers between the lab and scaling up to meet industrial demand. For example, many bioplastics are made from molecules that are extracted from biomass, such as seaweed, and mixed with performance modifiers before being cast into films. This process requires the materials to be in the form of a solution prior to casting, and this is not scalable.”
Other researchers have used spirulina to create bioplastics, but the UW researchers’ bioplastics are much stronger and stiffer than previous attempts. The UW team optimized microstructure and bonding within these bioplastics by altering their processing conditions — such as temperature, pressure, and time in the extruder or hot-press — and studying the resulting materials’ structural properties, including their strength, stiffness and toughness.
These bioplastics are not quite ready to be scaled up for industrial usage. For example, while these materials are strong, they are still fairly brittle. Another challenge is that they are sensitive to water.
“You wouldn’t want these materials to get rained on,” Iyer said.
The team is addressing these issues and continuing to study the fundamental principles that dictate how these materials behave. The researchers hope to design for different situations, by creating an assortment of bioplastics. This would be similar to the variety of existing petroleum-based plastics.
Plastic pollution on the world’s coral reefs
by Hudson T. Pinheiro, Chancey MacDonald, Robson G. Santos, et al in Nature
In a paper, researchers from the California Academy of Sciences, University of São Paulo, University of Oxford, University of Exeter, and other collaborators reveal the extent of plastic pollution on coral reefs, finding that debris increases with depth, largely stems from fishing activities, and is correlated with proximity to marine protected areas.
Through underwater visual surveys spanning more than two dozen locations across the Indian, Pacific, and Atlantic oceans, the researchers expose the abundance, distribution, and drivers of plastic pollution at various depths, which in turn enables them to identify what conservation efforts could be prioritized — and where — to protect our planet’s vulnerable coral reefs.
“Plastic pollution is one of the most pressing problems plaguing ocean ecosystems, and coral reefs are no exception,” says Hudson Pinheiro, PhD, the study’s lead author, a biologist at the Center for Marine Biology of the University of São Paulo, and an Academy research fellow. “From macroplastics that spread coral diseases to fishing lines that entangle and damage the structural complexity of the reef, decreasing both fish abundance and diversity, pollution negatively impacts the entire coral reef ecosystem.”
For the study, the researchers conducted more than 1,200 visual surveys across 84 shallow and mesophotic reef ecosystems located in 14 countries. To survey hard-to-reach mesophotic — or ‘twilight zone’ — coral reefs that exist between 100 and 500 feet (30 and 150 meters) deep, researchers relied on specialized diving gear that few other scientific dive teams are trained to safely use.
According to the study, coral reefs appear to be more contaminated by plastics and other human-derived debris than other marine ecosystems that have been evaluated, but are much less polluted than shoreline ecosystems like beaches and wetlands. However, contrary to studies of near-shore environments, the researchers found that the amount of plastic increased with depth — peaking in the mesophotic zone — and was mostly derived from fishing activities.
“It was surprising to find that debris increased with depth since deeper reefs in general are farther from sources of plastic pollution,” says Luiz Rocha, PhD, Academy curator of ichthyology and co-director of the Academy’s Hope for Reefs initiative, who was the senior author on the study. “We are almost always the first humans to set eyes on these deeper reefs, and yet we see human-produced trash on every dive. It really puts the effect we have had on the planet into perspective.”
Of the total debris, 88% was macroplastics larger than about two inches (five centimeters). The researchers posit that the potential causes of pollution reaching such depths include increased wave action and turbulence near the surface dislodging trash and carrying it away, recreational divers removing debris from more accessible shallow reefs, and shallow corals with higher growth rates overgrowing the trash hiding it from their surveys.
Over the course of the study, the researchers found human-derived debris in nearly all locations, including some of the planet’s most remote and pristine coral reefs, such as those adjacent to uninhabited islands in the central Pacific. The lowest densities of pollution — around 580 items per square kilometer — were observed in locations such as the Marshall Islands. Comoros, an island chain off the southeast coast of Africa, had the highest density of pollution with nearly 84,500 items per square kilometer — the equivalent of around 520 pieces of debris on one football field. Troublingly, the researchers say that because these plastic-laden deeper reefs are more difficult to study, they are rarely included in conservation efforts, management targets, and discussions despite harboring unique biodiversity that’s often not found on shallow reefs.
“Our findings provide more evidence that the mesophotic is not a refuge for shallow reef species in a changing climate as we once thought,” says co-author Bart Shepherd, director of the Academy’s Steinhart Aquarium and co-director of Hope for Reefs. “These reefs face many of the same pressures from human society as shallow reefs, and have a unique and poorly-studied fauna. We need to protect deeper reefs and make sure that they are included in the conservation conversation.”
Although the researchers found much consumer debris, such as water bottles and food wrappers, which are often the main source of plastic pollution in other ecosystems, nearly three-quarters of all plastic items documented on the surveyed reefs were related to fishing like ropes, nets, and fishing lines.
“Fishing gear, which even as debris continues to catch marine life through what we call ghost fishing, appears to contribute a large proportion of the plastic seen on mesophotic reefs,” says co-author Lucy Woodall, PhD, principal scientist of Nekton and associate professor in marine conservation biology and policy at University of Exeter. “Unfortunately, fishing gear debris is often not reduced by general waste management interventions; therefore specific solutions related to the needs of fishers should be considered, such as no-charge disposing of damaged gear in ports or individually labelling gear to ensure fishers take responsibility for misplaced equipment.”
To uncover the drivers of coral reef pollution, the researchers analyzed how the abundance of human-derived debris correlated with a number of geographic and socioeconomic factors. In general, they found pollution on reefs increases with depth and proximity to densely populated cities, local markets, and, counterintuitively, marine protected areas. Since most marine protected areas allow some fishing within or near their borders and are typically more productive than other locations due to their protected status, they are often heavily frequented by fishers, according to the researchers.
“Our findings reveal some of the complex collective challenges we face when dealing with plastic pollution,” Pinheiro says. “As marine resources around the world dwindle, humans that rely on those resources are turning to deeper habitats and those closer to marine protected areas where fish remain abundant.”
Investigations into the closed-loop hydrometallurgical process for heavy metals removal and recovery from biosolids via mild acid pre-treatment
by Ibrahim Gbolahan Hakeem, Pobitra Halder, Shefali Aktar, Mojtaba Hedayati Marzbali, Abhishek Sharma, Aravind Surapaneni, Graeme Short, Jorge Paz-Ferreiro, Kalpit Shah in Hydrometallurgy
Engineers in Melbourne have developed a cost-effective and environmentally friendly way to remove heavy metals, including copper and zinc, from biosolids.
The team’s work, led by RMIT University in collaboration with South East Water and Manipal University in India, advances other methods for heavy-metal removal by recycling the acidic liquid waste that is produced during the recovery phase, instead of throwing it away. Lead senior researcher Professor Kalpit Shah from RMIT said the heavy metals found in biosolids — treated sewage sludge — can be valuable, and the recovery of metals such as copper and zinc can be achieved using the team’s approach.
“Our innovation helps ensure the resulting biosolids do not leach heavy metals into the environment and retain the nutrients that can be used for land applications,” said Shah, Deputy Director (Academic) of the ARC-funded Training Centre for the Transformation of Australia’s Biosolids Resources in RMIT’s School of Engineering.
“With further processing, the biosolids can be turned into high-grade biochar, which is a renewable energy resource and has a range of applications including as a fertiliser.”
The overall metal-removal process occurs over three stages: extraction, purification and recovery. Prior to the team’s work, metal recovery from biosolids had not been fully explored among researchers beyond the first stage. The first author of the journal article, RMIT PhD researcher Ibrahim Hakeem, said biosolids can contain several metals locked within organic matter, making purification and metal recovery challenging.
“We devised an approach where we were able to recover the metals one by one and did so with a closed-loop solution that causes least harm to the environment,” said Hakeem, from RMIT’s School of Engineering.
The challenge is that reducing the organic matter through pyrolysis results in a higher concentration of heavy metals in the biochar, which the team’s new technique helps resolve. The application of biosolids to agricultural land in Australia is subject to guidelines and regulations that specify limits for heavy-metal concentrations, ensuring that biosolids can be safely used as fertiliser. The team aims to work with water authorities to use its heavy-metal removal technique prior to pyrolysis.
“The transition to a circular economy is important for the water industry,” said South East Water’s R&D Manager, Dr David Bergmann. “We have previously seen our sludge as waste, but now through research like this we are able to see that it’s possible to clean it up and convert it into potential materials with value and further applications.”
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