GT/ Plastic cloud: New study analyzes airborne microplastics in clouds
Energy & green technology biweekly vol.58, 30th September — 19th October
TL;DR
- Plastic waste that accumulates on land eventually ends up in the ocean as microplastics. However, it is now speculated that microplastics are also present in the atmosphere, contained in clouds. In a new study, researchers analyzed cloud water samples from high-altitude mountains in Japan to ascertain the amount of microplastics in them. They also shed light on how these airborne particles influence cloud formation and their negative impact on the climate.
- The sun sends enormous amounts of energy to the earth. Nevertheless, some of it is lost in solar cells. This is an obstacle in the use of organic solar cells, especially for those viable in innovative applications. A key factor in increasing their performance: Improved transport of the solar energy stored within the material. Now a research group has shown that certain organic dyes can help build virtual highways for the energy.
- Scientists isolate a microbial enzyme and branch it on an electrode to efficiently and unidirectionally convert CO2 to formate.
- Engineers and scientists look at how thoughtful design can reduce a sustainably-designed neighborhood’s energy vulnerability during power disruptions, as well as which design characteristics are needed if and when local populations need to move to shelters. Researchers analyzed the design and energy characteristics of particular kinds of buildings and neighborhoods to assess their vulnerabilities and their access to alternative and renewable energy sources. The authors use several scenarios involving different lengths of power disruption to see which kind of response is most beneficial to the populations affected.
- In a breakthrough for environmentally friendly chemical production, researchers have developed an economical way to make succinic acid, an important industrial chemical, from sugarcane.
- It is impossible to imagine modern agriculture without plastics. 12 million tons are used every year. But what about the consequences for the environment? An international team of authors addresses this question in a recent study. The research shows the benefits and risks of using plastics in agriculture, and identifies solutions that ensure their sustainable use.
- An experiment using water from a large wastewater treatment plant has shown that this water continues to affect river diversity and the trophic web (food web) despite being properly treated and highly diluted before discharge. The study shows that the limits currently in place and the procedures used to treat wastewater may not be sufficient to protect the natural properties of food webs.
- Researchers have investigated the potential in Japan for more sustainable plastic recycling and the market for bioplastics.
- Storing renewable energy as hydrogen could soon become much easier thanks to a new catalyst based on single atoms of platinum.
- Scientists have devised an efficient method of recovering high-purity silicon from expired solar panels to produce lithium-ion batteries that could help meet the increasing global demand to power electric vehicles.
- 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
Airborne hydrophilic microplastics in cloud water at high altitudes and their role in cloud formation
by Yize Wang, Hiroshi Okochi, Yuto Tani, et al in Environmental Chemistry Letters
Plastic waste that accumulates on land eventually ends up in the ocean as microplastics. However, it is now speculated that microplastics are also present in the atmosphere, contained in clouds. In a new study, researchers analyzed cloud water samples from high-altitude mountains in Japan to ascertain the amount of microplastics in them. They also shed light on how these airborne particles influence cloud formation and their negative impact on the climate.
Plastic particles less than 5 mm in size are called “microplastics.” These tiny bits of plastic are often found in industrial effluents, or form from the degradation of bulkier plastic waste. Research shows that large amounts of microplastics are ingested or inhaled by humans and animals alike and have been detected in multiple organs such as lung, heart, blood, placenta, and feces. Ten million tons of these plastic bits end up in the ocean, released with the ocean spray, and find their way into the atmosphere. This implies that microplastics may have become an essential component of clouds, contaminating nearly everything we eat and drink via “plastic rainfall.” While most studies on microplastics have focused on aquatic ecosystems, few have looked into their impact on cloud formation and climate change as “airborne particles.”
In a new study led by Hiroshi Okochi, Professor at Waseda University, a group of Japanese researchers has explored the path of airborne microplastics (AMPs) as they circulate in the biosphere, adversely impacting human health, and the climate. Their study was recently published with contributions from co-authors Yize Wang from Waseda University and Yasuhiro Niida from PerkinElmer Japan Co. Ltd.
“Microplastics in the free troposphere are transported and contribute to global pollution. If the issue of ‘plastic air pollution’ is not addressed proactively, climate change and ecological risks may become a reality, causing irreversible and serious environmental damage in the future,” explains Okochi.
To investigate the role of these tiny plastic particles in the troposphere and the atmospheric boundary layer, the team collected cloud water from the summit of Mount (Mt.) Fuji, south-eastern foothills of Mt. Fuji (Tarobo), and the summit of Mt. Oyama — regions at altitudes ranging between 1300–3776 meters. Using advanced imaging techniques like attenuated total reflection imaging and micro-Fourier transform infrared spectroscopy (µFTIR ATR imaging), the researchers determined the presence of microplastics in the cloud water, and examined their physical and chemical properties.
They identified nine different types of polymers and one type of rubber in the AMPs detected. Notably, most of the polypropylene that was detected in the samples was degraded and had carbonyl (C=O) and/or hydroxyl (OH) groups. The Feret diameters of these AMPs ranged between 7.1–94.6 µm, the smallest seen in the free troposphere. Moreover, the presence of hydrophilic (water loving) polymers in the cloud water was abundant, suggesting that they were removed as “cloud condensation nuclei.” These findings confirm that AMPs play a key role in rapid cloud formation, which may eventually affect the overall climate.
Accumulation of AMPs in the atmosphere, especially in the polar regions, could lead to significant changes in the ecological balance of the planet, leading to severe loss of biodiversity.
Okochi concludes by saying “AMPs are degraded much faster in the upper atmosphere than on the ground due to strong ultraviolet radiation, and this degradation releases greenhouse gases and contributes to global warming. As a result, the findings of this study can be used to account for the effects of AMPs in future global warming projections.”
Directed exciton transport highways in organic semiconductors
by Kai Müller, Karl S. Schellhammer, Nico Gräßler, Bipasha Debnath, Fupin Liu, Yulia Krupskaya, Karl Leo, Martin Knupfer, Frank Ortmann in Nature Communications
The sun sends enormous amounts of energy to the earth. Nevertheless, some of it is lost in solar cells. This is an obstacle in the use of organic solar cells, especially for those viable in innovative applications. A key factor in increasing their performance: Improved transport of the solar energy stored within the material. Now a research group at the Technical University of Munich (TUM) has shown that certain organic dyes can help build virtual highways for the energy.
Organic solar cells are light, extremely thin energy collectors and as a flexible coating are a perfect fit on almost any surface: Solar cells based on organic semiconductors open up a range of application possibilities, for example, as solar panels and films which can be rolled up, or for use on smart devices. But one disadvantage in many applications is the comparatively poor transport of the energy collected within the material. Researchers are investigating the elementary transport processes of organic solar cells in order to find ways to improve this transport.
One of these researchers is Frank Ortmann, Professor of Theoretical Methods in Spectroscopy at TUM. He and his colleagues from Dresden focus more than anything on the mutual interaction between light and material — especially the behavior of what are called excitons. “Excitons are something like the fuel of the sun, which has to be used optimally,” explains Ortmann, who is also a member of the “e-conversion” Excellence Cluster. “When light energy in the form of a photon collides with the material of a solar cell it is absorbed and buffered as an excited state. This intermediate state is referred to as an exciton.” These charges cannot be used as electrical energy until they reach a specially designed interface. Ortmann and his team have now shown that what are referred to as exciton transport highways can be created using organic dyes.
The reason it is so important that the excitons reach this interface as quickly as possible has to do with their short lifespan. “The faster and more targeted the transport, the higher the energy yield, and thus the higher the efficiency of the solar cell,” says Ortmann. The molecules of the organic dyes, referred to as quinoid merocyanines, make this possible, thanks to their chemical structure and their excellent ability to absorb visible light. Accordingly, they are also suitable for use as the active layer in an organic solar cell, Ortmann explains.
Using spectroscopic measurements and models the researchers were able to observe the excitons racing through the dye molecules. “The value of 1.33 electron volts delivered by our design is far above the values found in organic semiconductors — you could say the organic dye molecules form a kind of super-highway,” Ortmann adds. These fundamental new findings could pave the way for targeted, more efficient exciton transport in organic solid matter, accelerating the development of organic solar cells and organic light emitting diodes with even higher performance.
Bioelectrocatalytic CO2 Reduction by Mo‐Dependent Formylmethanofuran Dehydrogenase
by Selmihan Sahin, Olivier N. Lemaire, Mélissa Belhamri, Julia M. Kurth, Cornelia U. Welte, Tristan Wagner, Ross D. Milton in Angewandte Chemie International Edition
Humanity continuously emits greenhouse gases and thereby worsens global warming. Increasing research efforts go into developing strategies to convert these gases, such as carbon dioxide (CO2), into valuable products. CO2 accumulates dramatically over the years and is chemically very stable, thus challenging to transform. Yet, for billions of years, some microbes have actively captured CO2 using highly efficient enzymes. Scientists from the Max Planck Institute for Marine Microbiology in Bremen together with the Universities of Geneva and Radboud isolated one of these enzymes. When the enzyme was electronically branched on an electrode, they observed the conversion of CO2 to formate with perfect efficiency. This phenomenon will inspire new CO2-fixation systems because of its remarkable directionality and rates.
“The enzymes employed by the microorganisms represent a fantastic playground for scientists as they allow highly specific reactions at fast rates,” says Tristan Wagner, head of the Max Planck Research Group Microbial Metabolism at the Max Planck Institute for Marine Microbiology (MPIMM). Some of these enzymes have an interesting way of capturing CO2: They transform it into formate, a stable and safe compound that can be used to store energy or to synthesize various molecules for industrial or pharmaceutical purposes. One example is Methermicoccus shengliensis, a methanogen (a microbe producing methane) isolated from an oilfield and growing at 50 °C. It has been cultivated and studied over the past years by Julia Kurth and Cornelia Welte at Radboud University in the Netherlands. At the Max Planck Institute for Marine Microbiology, Olivier Lemaire, Mélissa Belhamri and Tristan Wagner dissected the microbe to find its CO2-capturing enzyme and measure how fast and efficiently it can transform CO2.
The Max Planck-scientists undertook the challenging task to isolate the microbial enzyme. “Since we knew that such enzymes are sensitive to oxygen, we had to work inside an anaerobic tent devoid of ambient air to separate it from the other proteins — quite complicated, but we succeeded,” says Olivier Lemaire. Once isolated, the scientists characterized the enzyme’s properties. They showed that it efficiently generates formate from CO2 but performs the reverse reaction at very slow rates and poor yield.
“Similar enzymes belonging to the family of formate dehydrogenases are well known to operate in both directions, but we showed that the enzyme from Methermicoccus shengliensis is nearly unidirectional and could not efficiently convert the formate back into CO2,” reports Mélissa Belhamri. “We were quite thrilled by this phenomenon, occurring only in the absence of oxygen,” she adds.
“Since the formate generated from CO2-fixation cannot be transformed back and therefore accumulates, such a system would be a highly interesting candidate for CO2-capture, especially if we could branch it on an electrode,” Tristan Wagner points out. The advantage of that: With the enzyme naturally or chemically attached to an electrode, the “energy” required to capture the CO2 will be directly delivered by the electrode, without electric current loss or the need for expensive or toxic chemical compounds as relays. Consequently, the enzyme-bound electrodes are efficient and attractive systems for gas conversion procedures. Thus, the purified enzyme was sent to the University of Geneva to set up an electrode-based CO2-capture system.
Selmihan Sahin and Ross Milton from the University of Geneva are specialists in electrochemistry. They use electrodes connected to electric current to perform chemical reactions. The electrode-based formate generation from CO2 often requires polluting and rare metals, and that is why they tried to replace these metals with the enzyme extracted in the group of Tristan Wagner at the MPIMM. The procedure of enzyme binding on an electrode is not always as efficient as expected, but the enzyme from Wagner’s research group has specific characteristics that could facilitate the process. The scientists from Switzerland managed to fix the enzyme on a graphite electrode, where it performed the gas conversion. The measured rates were comparable to those obtained with classic formate dehydrogenases. “The strength of this biological system coupled to the electrode lies in its efficiency in transferring the electrons from the electricity towards CO2 transformation,” highlights Lemaire. Sahin and Milton also confirmed that the system performs the reverse reaction poorly, as previously observed in the reaction tube. Consequently, the modified electrode continuously converted the greenhouse gas to formate without any detectable side-products generated or electric current loss.
The collaborative work provides a new molecular tool to the scientific community: An enzyme converting CO2 by transferring electricity with high efficiency. Renewable green energy (e.g., wind or solar) could provide electricity to the electrode-based system that would turn CO2 into formate, a molecule directly usable for applications or to store energy.
“Before us, no one ever tried to study an enzyme from such a methanogen for an electrode-based gas conversion,” says Tristan Wagner. “Yet, methanogens are natural outstanding gas converters.”
As powerful as they could be, employing enzymes for large-scale processes would also require similar-scale enzyme production systems, a considerable investment. Therefore, while the discovered strategy could, in theory, significantly improve CO2 transformation, a deep knowledge of the enzyme mechanism is necessary before its application, and the team of researchers will now have to dissect in depth the molecular secrets of the reaction.
Role of neighbourhood spatial and energy design in reducing energy vulnerability during power disruption
by Caroline Hachem-Vermette, Kuljeet Singh in Renewable and Sustainable Energy Reviews
Individual neighbourhoods will be intimately involved in providing local solutions to collective problems. One measure will be distributed renewable energy production — energy produced at local levels, either by solar technology, wind or other methods, will push cities to achieve their net-zero targets.
However, even these power-generating neighbourhoods will remain vulnerable to power outages resulting from natural disasters such as hurricanes, fires or floods. And all of these are likely to become increasingly common due to the effects of climate change. So how will sustainable neighbourhoods cope with the pressures put on their energy systems?
Caroline Hachem-Vermette is an associate professor in the Department of Building, Civil and Environmental Engineering at the Gina Cody School of Engineering and Computer Science. In a new paper, she looks at how thoughtful design can reduce a neighbourhood’s energy vulnerability during power disruptions, as well as which design characteristics are needed if and when local populations need to move to shelters.
In article Hachem-Vermette and co-author Kuljeet Singh from the University of Prince Edward Island analyse the design and energy characteristics of particular kinds of buildings and neighbourhoods to assess their vulnerabilities and their access to alternative and renewable energy sources. The authors use several scenarios involving different lengths of power disruption to see which kind of response is most beneficial to the populations affected.
“We focused on the neighbourhood unit level because we can look at characteristics and detail levels that are harder to find at the city level,” Hachem-Vermette explains. “Designed to be self-contained in terms of basic conveniences and services, the neighbourhood unit is a fundamental concept in urban planning. Neighborhood units serve as a basis for city-level development and design and can be used to understand various sustainable and resilient strategies.”
Designed along sustainable practices, the theoretical neighbourhoods were based on the kinds found in typical Canadian municipalities: low-density residential, mixed residential/commercial and retail, high-density residential and mixed high-density residential and industrial. The researchers also assessed the types of energy systems these neighbourhoods primarily relied on to provide electrical and thermal energy.
These indicators were considered across scenarios in which power disruptions lasted between one day and over three weeks. They provided reliable estimates regarding energy interruption vulnerability as well as the best measures to be considered to mitigate the effects of these disasters on local populations.
The researchers came away from their study with several recommendations that could improve a stricken neighbourhood’s resilience. They urged municipal authorities to do the following: equip large buildings such as schools with the means to be self-sufficient in energy production so they could be used as temporary shelters; modify design standards for shelters to increase their maximum population while still providing good indoor air quality, hygienic spaces for living, food preparation and recreation; and incorporate neighbourhood spatial design methods to ensure access to roads, potential shelter buildings and hospitals, and landscapes for energy system installations.
Hachem-Vermette realizes much more study is needed as cities move toward fully sustainable practices in the face of increasingly extreme weather. But she is confident that initiatives such as Concordia’s PLAN/NET ZERØ and the $123-million dollar Canada First Research Excellence Fund grant announced earlier this year will help her and her fellow researchers find pathways to navigate the societal transition to renewable energy sources.
“My research is at the heart of the effort to build neighbourhoods that are decarbonised,” she says. “With my background in architecture, urban planning and building engineering, I can pull these disciplines together. Bridging the gaps at the interface of these disciplines is where we will find sustainable and resilient solutions.”
An end-to-end pipeline for succinic acid production at an industrially relevant scale using Issatchenkia orientalis
by Vinh G. Tran, Somesh Mishra, Sarang S. Bhagwat, Saman Shafaei, Yihui Shen, Jayne L. Allen, Benjamin A. Crosly, Shih-I Tan, Zia Fatma, Joshua D. Rabinowitz, Jeremy S. Guest, Vijay Singh, Huimin Zhao in Nature Communications
In a breakthrough for environmentally friendly chemical production, researchers at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) have developed an economical way to make succinic acid, an important industrial chemical, from sugarcane.
The team of University of Illinois and Princeton University researchers created a cost-effective, end-to-end pipeline for this valuable organic acid by engineering a tough, acid-tolerant yeast as the fermenting agent, avoiding costly steps in downstream processing. Succinic acid is a widely used additive for food and beverages and has diverse applications in agricultural and pharmaceutical products.
This same pipeline can be used to produce other industrially important organic acids targeted by CABBI in its work to develop sustainable biofuels and biochemicals from crops, said co-author Huimin Zhao, CABBI’s Conversion Theme Leader and Professor of Chemical and Biomolecular Engineering (ChBE) at Illinois. To reduce reliance on fossil fuels, Conversion researchers are deploying microbes to convert plant biomass into chemicals used in everyday products as an alternative to conventional petroleum-based production.
“This will serve as a blueprint for all the other metabolic engineering products in CABBI,” said Zhao, one of several CABBI principal investigators on the project. The study is led by CABBI — a U.S. Department of Energy Bioenergy Research Center — and funded by BioMADE, a Manufacturing Innovation Institute with more than 230 member organizations around the country, including companies, universities, and nonprofit organizations. BioMADE was catalyzed by the U.S. Department of Defense and works to secure America’s future through bioindustrial manufacturing innovation, education, and collaboration.
The work builds on years of research on succinic acid production by Zhao and his colleagues using Issatchenkia orientalis, an unconventional yeast ideal for making organic acids.
I. orientalis has the unique ability to thrive in low-pH, or acidic, conditions. Most organisms require a neutral pH environment to survive, including Saccharomyces cerevisiae, a more conventional yeast, or Escherichia coli bacteria. Both have been used by companies and labs to produce succinic acid but proved to be too costly, so efforts to scale up production have failed, Zhao said. Those microorganisms require the addition of a base to neutralize the toxic acidic conditions so they can continue making succinic acid. But that generates side products, such as gypsum or calcium sulfate, which have to be separated out at the end of the pipeline to purify the product, driving up downstream processing costs.
“One of the bottlenecks in the production of organic acids is the separation cost,” Zhao said. “We have to add a lot of base to keep the pH near neutral, between 6 to 7.”
With I. orientalis, however, “the organism lives happily at a pH of 3 to 4,” so the additives are not required, Zhao said. “In the end, that significantly reduces costs.”
The CABBI researchers also did extensive metabolic engineering to rewire I. orientalis to produce robust levels of succinic acid — higher than either S. cerevisiae or E. coli, he said. Using metabolic flux analysis from Rabinowitz’s lab, they identified the steps in the yeast’s metabolism that limited the production of succinic acid. One key roadblock: Native I. orientalis can’t utilize the sucrose from sugarcane. So an enzyme was added that could break down sucrose from the sugarcane juice into glucose and fructose to make succinic acid. Other genes were introduced to overproduce succinic acid.
Working with Singh’s group at IBRL, the team then scaled up succinic acid production using industrially relevant equipment to conduct an end-to-end integration of the process. The pilot-scale work showed the new strains could produce up to 110 g/L of succinic acid and, after batch fermentation and downstream processing, an overall yield of 64% — impressive results having commercial significance, Singh said. The combination of higher production levels through genetic engineering and lower costs from the elimination of downstream separation makes the process “very attractive,” Zhao said. “That’s why the pipeline is so economical, at least at this pilot scale.”
The final step was working with Guest to simulate a full end-to-end, low-pH succinic acid production pipeline, using the open-source software platform BioSTEAM developed by his group. The techno-economic analysis (TEA) and life cycle assessment showed the process was financially viable and could reduce greenhouse gas emissions by 34% to 90% relative to fossil fuel-based production processes.
“These advancements in metabolic engineering could have large-scale benefits, simultaneously driving down costs and environmental impacts in support of a circular bioeconomy,” Guest said.
The process emits less carbon dioxide (CO2) than conventional petroleum-based chemical processing. Plants like sugarcane also soak up carbon, and CO2 can be used as a substrate for the process, further reducing its carbon footprint.
“It’s definitely more environmentally friendly. That’s the premise for all the research in CABBI: using renewable resources to make chemicals and fuels,” Zhao said.
Researchers plan further scale-up studies soon to support commercialization of the succinic acid production process. The work will also be a template for production of other CABBI products using I. orientalis, including 3-hydroxypropionic acid (3-HP). The market for 3-HP, used in components of disposable diapers and sealants, exceeds $1 billion, and research to date shows huge promise, Zhao said.
“We expect I. orientalis can serve as a general industrial platform for the production of a wide variety of organic acids,” said Vinh Tran, primary author on the paper and a Ph.D. student in ChBE.
Plastics can be used more sustainably in agriculture
by Thilo Hofmann, Subhasis Ghoshal, Nathalie Tufenkji, et al in Communications Earth & Environment
It is impossible to imagine modern agriculture without plastics. 12 million tonnes are used every year. But what about the consequences for the environment? An international team of authors led by Thilo Hofmann from the Division of Environmental Geosciences at the University of Vienna addresses this question in a recent study. The research shows the benefits and risks of using plastics in agriculture, and identifies solutions that ensure their sustainable use.
Once celebrated as a symbol of modern innovation, plastic is now both a blessing and a curse of our time. Plastic is ubiquitous in every sector, and agriculture is no different. Modern agriculture, which is responsible for almost a third of global greenhouse gas emissions and is a major drain on the planet’s resources, is inextricably linked to plastic. The new study from the University of Vienna was conducted by Thilo Hofmann, environmental psychologist Sabine Pahl and environmental scientist Thorsten Hüffer, along with international co-authors. Their research reveals that plastic plays a multi-faceted role: from mulch films that protect plants to water-saving irrigation systems, plastic is deeply embedded in our food production.
According to the Food and Agriculture Organisation of the United Nations (FAO), over 12 million tonnes of plastic are integrated into the agricultural process every year. From securing plants with clamps to protecting them with nets, plastic has found its place in all areas of agricultural production. The use of plastic in agriculture undeniably conserves important resources. The front-runner is mulch films, which account for about 50% of all agricultural plastics. Mulch films not only control weeds and pests, but also preserve soil moisture, regulate temperature, and improve nutrient uptake, thus helping to reduce the ecological footprint of agriculture. In China, not using mulch films would require an additional 3.9 million hectares of cropland to maintain the status quo of production.
But the intensive use of plastics in agriculture also has downsides: impaired soil fertility, dwindling crop yields, and the chilling prospect of toxic additives seeping into our food chain. Conventional plastics persist in the environment, with residues accumulating in our soils. Tiny plastic particles can be ingested by plants. Although research into the uptake of nanoplastics is still in its infancy, preliminary data suggests that plastics can enter our food chain through agriculture.
In navigating the challenges of plastic in agriculture, the spotlight falls on a strategy that champions the rational use of plastic, its efficient collection post-use, and the innovation of cutting-edge recycling methods, the authors state in the new study. “In cases where plastics remain in the environment, their design should ensure complete biodegradation. Furthermore, it is crucial that toxic plastic additives are replaced by safer alternatives,” explains Thilo Hofmann
While bio-based materials present a tempting alternative, they are not without caveats. A rushed pivot to such materials without adequate consideration of their life cycles could unintentionally put more strain on our ecosystems and food networks.
The measures proposed by the authors are in line with global initiatives like the UN Plastics Treaty (UNEA 5.2). Adopting these practices will foster more sustainable use of plastics in agriculture, according to the scientists. While a complete replacement of plastics is untenable at present, the judicious use of alternatives with minimal environmental impact seems to be a promising way forward. With mandatory monitoring, technological advancement and educational initiatives, reducing our reliance on plastic and its adverse environmental impacts should be possible.
Treated and highly diluted, but wastewater still impacts diversity and energy fluxes of freshwater food webs
by Ioar de Guzman, Arturo Elosegi, Daniel von Schiller, Jose M. González, Laura E. Paz, Benoit Gauzens, Ulrich Brose, Alvaro Antón, Nuria Olarte, José M. Montoya, Aitor Larrañaga in Journal of Environmental Management
An experiment using water from a large wastewater treatment plant carried out by the Stream Ecology group has shown that this water continues to affect river diversity and the trophic web (food web) despite being properly treated and highly diluted before discharge. The study shows that the limits currently in place and the procedures used to treat wastewater may not be sufficient to protect the natural properties of food webs.
Wastewater treatment plants have considerably improved water quality around the world since the quantity of pollutants reaching aquatic ecosystems has been significantly reduced, as a result of environmental regulatory procedures. However, despite the fact that the effluent discharged through wastewater treatment plants is treated, what is left behind is a complex cocktail of pollutants, nutrients and pathogens, whose environmental effects, hidden by other factors, may pass unnoticed. More advanced WWTPs apply additional treatments to reduce nutrients, organic matter and metals in the sewage, and these wastewater discharges, despite being highly diluted, can exert minor effects if they continue for a long time.
“To study the effects of these plants properly, we designed an innovative experiment that allowed us to handle the entire ecosystem over several years,” explained Ioar de Guzmán, a researcher in the UPV/EHU’s Stream Ecology group. Firstly, several variables were measured for one year in two selected reaches in an unpolluted stream, to see the difference between these reaches: “That way we knew how these stream variables changed depending on time and place,” she said. After that, properly treated, highly diluted water from a wastewater treatment plant was diverted to one of these downstream reaches, and “we took measurements over the period of another year in both reaches to see what changes had been brought about by these discharges on the diversity of the stream and on the trophic network (group of organisms organised by food relationships) and on the functioning of the ecosystem.”
The study showed that treated wastewater can exert significant effects on the ecosystem and affect the structure and functioning of stream communities even if it is highly diluted when discharged. Although the toxicity of the effluent was found to be low, “in general, invertebrate diversity was reduced and communities became more heterogeneous; the amount of algae and herbivory (or tendency to feed on plants) increased,” explained the researcher. Although the wastewater is treated, certain nutrients that can help boost algae and organic matter enter the stream, but the pollutants can also lead to the disappearance of sensitive invertebrates and their replacement by more resistant ones.
It is therefore clear that the more advanced processes currently used in wastewater treatment continue to affect freshwater ecosystems, and that the conservation of freshwater food webs requires intensified efforts in the treatment of polluted waters: “We believe that by adhering to the limits stipulated by the legislation, the problems are reduced, but impacts are nevertheless generated; we must bear in mind that for an optimal conservation of the trophic networks of the streams, these treatments have to be even more stringent,” concluded the researcher from the Stream Ecology group.
Toward Economically Efficient Carbon Reduction: Contrasting Greening Plastic Supply Chains with Alternative Energy Policy Approaches
by Yuuki Yoshimoto, Koki Kishimoto, Kanchan Kumar Sen, Takako Mochida, Andrew Chapman in Sustainability
Japan has a plastic problem. Thanks in part to an overabundance of packaging, the country is the second largest producer of plastic waste per capita.
While plastic pollution is a well-known cause for concern, an often-overlooked issue is how plastics contribute to global warming. Plastics are a surprisingly large cause of carbon emissions, with roughly 4.5% of global emissions caused by the plastics sector. Now, joint research between Kyushu University and Yokohama-based start-up company, Sotas Co., Ltd, has investigated the potential for Japan’s market to incorporate a greener plastic supply chain.
“The Japanese government has pledged to achieve carbon neutrality by 2050. However, the predominant method that Japan uses to get rid of plastic waste is ‘thermal recycling’ or incineration, which releases carbon dioxide into the atmosphere,” says senior author Professor Andrew Chapman, from Kyushu University’s International Institute for Carbon Neutral Energy and Research. “We have examined whether switching to more sustainable recycled plastics and bioplastics is a competitive and effective alternative to current carbon reduction policies.”
The researchers began with an economic and environmental assessment of six commonly used plastic types, based on whether they were made using virgin, recycled or bioplastic. They scored the plastics using four different criteria: global warming potential, cost, recyclability and perceived quality for manufacturers. Depending on the weighting given to each factor, the researchers calculated how desirable each plastic was under a number of scenarios.
In general, the researchers found that virgin plastics, which are made directly from fossil fuels, are perceived to be the highest quality, but have a high global warming potential and are relatively expensive. Recycled plastics, on the other hand, are cheaper and also have a lower global warming potential. However, plastics with a higher blend of recycled material were perceived to be of lower quality and recyclability also varied greatly for each plastic type.
“One issue is that it can be physically harder to separate out some types of plastics before recycling and additionally, some plastics can only be recycled a certain number of times,” says first author Yuuki Yoshimoto, President of Sotas Co., Ltd. “It’s therefore important to establish a robust, centralized chain of custody to keep track of how many times a piece of plastic has been recycled to provide quality assurance to end users.”
The analysis also revealed that bioplastics, which are made from plants, have the lowest global warming potential. Some bioplastics can even be carbon-negative, as the plants take in carbon dioxide from the atmosphere as they grow, which is then sequestered in the material. However, bioplastics are much more costly to make than virgin or recycled plastics, and, as drop-in replacements are not always available, currently perform less well regarding perceived quality. Additionally, starch-based bioplastics require arable land to grow the crops.
“Food versus plastic production is not a fight we want, as land resources are very limited in Japan,” says Prof Chapman. Instead, the researchers suggested further funding for research into cellulose-based bioplastics, which can be sourced from wood pulp.
One additional factor that could help bridge the gap in the cost between bioplastics and virgin plastics is the consumers’ willingness to pay. Prior research suggests that consumers are willing to pay more for environmentally-friendly products, which the researchers plan to investigate in detail and incorporate into their analysis.
“This is a complex situation, with no one-size-fits-all solution,” concludes Yoshimoto. “Ultimately we hope this analysis can help policymakers decide what recycling processes to support, and to inform manufacturers which plastics can best meet their manufacturing and carbon reduction goals.”
This research also considers the economic efficiency of carbon reduction via plastic recycling and bioplastic replacement, broadening the potential policy approaches which can be pursued by policymakers.
Phase-dependent growth of Pt on MoS2 for highly efficient H2 evolution
by Zhenyu Shi, Xiao Zhang, Xiaoqian Lin, Guigao Liu, et al in Nature
Storing renewable energy as hydrogen could soon become much easier thanks to a new catalyst based on single atoms of platinum.
The new catalyst, designed by researchers at City University Hong Kong (CityU) and tested by colleagues at Imperial College London, could be cheaply scaled up for mass use.
Co-author Professor Anthony Kucernak, from the Department of Chemistry at Imperial, said: “The UK Hydrogen Strategy sets out an ambition to reach 10GW of low-carbon hydrogen production capacity by 2030. To facilitate that goal, we need to ramp up the production of cheap, easy-to-produce and efficient hydrogen storage. The new electrocatalyst could be a major contributor to this, ultimately helping the UK meet its net-zero goals by 2050.”
Renewable energy generation, from sources like wind and solar, is rapidly growing. However, some of the energy generated needs to be stored for when weather conditions are unfavourable for wind and sun. One promising way to do this is to save the energy in the form of hydrogen, which can be stored and transported for later use.
To do this, the renewable energy is used to split water molecules into hydrogen and oxygen, with the energy stored in the hydrogen atoms. This uses platinum catalysts to spur a reaction that splits the water molecule, which is called electrolysis. However, although platinum is an excellent catalyst for this reaction, it is expensive and rare, so minimising its use is important to reduce system cost and limit platinum extraction. Now, the team have designed and tested a catalyst that uses as little platinum as possible to produce an efficient but cost-effective platform for water splitting.
Lead researcher Professor Zhang Hua, from CityU, said: “Hydrogen generated by electrocatalytic water splitting is regarded as one of the most promising clean energies for replacing fossil fuels in the near future, reducing environmental pollution and the greenhouse effect.”
The team’s innovation involves dispersing single atoms of platinum in a sheet of molybdenum sulphide (MoS2). This uses much less platinum than existing catalysts and even boosts the performance, as the platinum interacts with the molybdenum to improve the efficiency of the reaction.
Growing the thin catalysts on nanosheet supports allowed the CityU team to create high-purity materials. These were then characterised in Professor Kucernak’ lab at Imperial, which has developed methods and models for determining how the catalyst operates. The Imperial team has the tools for stringent testing because they have developed several technologies that are designed to make use of such catalysts. Professor Kucernak and colleagues have set up several companies based on these technologies, including RFC Power that specialises in hydrogen flow batteries, which could be improved by using the new single-atom platinum catalysts.
Once renewable energy is stored as hydrogen, to use it as electricity again it needs to be converted using fuel cells, which produce water vapour as a by-product of an oxygen-splitting reaction. Recently, Professor Kucernak and colleagues revealed a single-atom catalyst for this reaction that is based on iron, instead of platinum, which will also reduce the cost of this technology.
Simplified silicon recovery from photovoltaic waste enables high performance, sustainable lithium-ion batteries
by Ying Sim, Yeow Boon Tay, Ankit, Xue Lin, Nripan Mathews in Solar Energy Materials and Solar Cells
Scientists from Nanyang Technological University, Singapore (NTU Singapore) have devised an efficient method of recovering high-purity silicon from expired solar panels to produce lithium-ion batteries that could help meet the increasing global demand to power electric vehicles.
High-purity silicon makes up the majority of solar cells, yet they are typically discarded at the end of their operational lifespan after 25 to 30 years. It is challenging to separate the silicon from other solar cell components such as aluminium, copper, silver, lead, and plastic. Moreover, recycled silicon has impurities and defects, making it unsuitable for other silicon-based technologies.
Existing methods to recover high-purity silicon are energy-intensive and involve highly toxic chemicals, making them expensive and limiting their widespread adoption among recyclers. The NTU researchers overcame the challenges through a new extraction method using phosphoric acid, a substance commonly used in the food and beverage industry. The NTU approach demonstrated a higher recovery rate and purity than present silicon recovery technologies. The process is also more efficient, involving just a single reagent (phosphoric acid), whereas conventional methods include at least two types of chemicals (highly acidic and highly alkaline).
Principal investigator of the study, Associate Professor Nripan Mathews, Provost’s Chair in Materials Science and Engineering and Cluster Director of the Energy Research Institute), said, “Our approach to silicon recovery is both efficient and effective. We do not have to use multiple chemicals, reducing the time spent on post-treatment of the chemical wastes. At the same time, we achieved a high recovery rate of pure silicon comparable to those produced by energy-intensive extraction techniques.”
While the use of solar renewable energy has climbed over the last few decades, the limited lifespan of 30 years for solar panels means that 78 million tonnes of solar panels are due to expire by 2050.
The NTU research team believes their silicon recovery method can potentially solve the growing problem of solar panel waste by keeping resources in a loop. The study signifies NTU’s commitment to its 2025 Strategic Plan, in which sustainability and innovation for a circular economy are key pillars. It also supports the NTU Sustainability Manifesto, which charts the University’s course for sustainability, carbon neutrality and societal impact.
Silicon is considered one of the most promising materials for next-generation lithium-ion batteries to power electric vehicles (EVs) due to its ability to deliver extended range and quick charging times. With carmakers racing to develop silicon-based lithium-ion batteries for advanced EVs, the NTU research team believes their newly developed silicon recovery method can support the expected demand for high-purity silicon.
The NTU approach involves first soaking the expired solar cell in hot diluted phosphoric acid for 30 minutes to remove metals (aluminium and silver) from their surfaces. This process is repeated using fresh phosphoric acid to ensure complete removal of the metals, resulting in pure silicon wafer at the end of another 30 minutes. Using advanced spectroscopic analyses to evaluate the elemental content of the recovered wafer, researchers found that their sample achieved a recovery rate of 98.9 per cent with a purity of 99.2 per cent — comparable results to silicon recovered through currently available methods. When the recovered silicon was upcycled into a lithium-ion battery anode and tested for efficiency, it performed similarly to new, commercially bought silicon.
Lead author of the study, Dr Sim Ying, Research Fellow, Energy Research Institute, said, “The comparable performance between our upcycled silicon-based lithium-ion battery and the newly purchased ones proves that the NTU approach is feasible. We envision our faster and cheaper silicon recovery method to be a positive boost for the development of EV batteries. Aside from EVs, there are also potential applications such as thermoelectric devices.”
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