GT/ Disposing of solar panels at end of their life
Energy & green technology biweekly vol.46, 23rd March — 6th April
TL;DR
- Renewable energy experts have come up with an environmentally-friendly plan to dispose of solar panels at the end of their life.
- Lower electricity costs for consumers and more reliable clean energy could be some of the benefits of a new study by researchers who have examined how predictable solar or wind energy generation is and the impact of it on profits in the electricity market.
- A new study found drought and heat waves could make air pollution worse for communities that already have a high pollution burden in California, and deepen pollution inequalities along racial and ethnic lines. The study also found financial penalties for power plants can significantly reduce people’s pollution exposure, except during severe heat waves.
- Scientists have created a comprehensive ‘roadmap’ to guide global efforts to convert waste energy into clean power.
- Sunlight can be used to produce green hydrogen directly from water in photoelectrochemical (PEC) cells. So far, most systems based on this ‘direct approach’ have not been energetically competitive. However, the balance changes as soon as some of the hydrogen in such PEC cells is used in-situ for a catalytic hydrogenation reaction, resulting in the co-production of chemicals used in the chemical and pharmaceutical industries. The energy payback time of photoelectrochemical ‘green’ hydrogen production can be reduced dramatically, the study shows.
- New research has shown that methane emissions from urban areas are underestimated by a factor of three to four and that untreated wastewater may be a contributing factor.
- Researchers have developed a new method that can easily purify contaminated water using a cellulose-based material. This discovery could have implications for countries with poor water treatment technologies and combat the widespread problem of toxic dye discharge from the textile industry.
- Large amounts of plastic waste are incinerated or deposited in landfills. This degrades the environment and depletes valuable resources. In this light, recycling plastics such as polymers is promising. However, recycling diminishes their quality. Recently, researchers have proposed a ‘closed-loop’ recycling process based on polymer microparticles. It produces fully recyclable polymer films with high mechanical stability and fracture energy, which they retain upon recycling.
- Engineers have developed a new water treatment that removes ‘forever chemicals’ from drinking water safely, efficiently — and for good.
- A team has experimentally confirmed that nitrate, a compound common in fertilizers and animal waste, can help transport naturally occurring uranium from the underground to groundwater. The new research backs a previous study showing that aquifers contaminated with high levels of nitrate — including the High Plains Aquifer residing beneath Nebraska — also contain uranium concentrations far exceeding a threshold set by the Environmental Protection Agency. Uranium concentrations above that EPA threshold have been shown to cause kidney damage in humans, especially when regularly consumed via drinking water.
- 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
Product stewardship considerations for solar photovoltaic panels
by Peter Majewski, Rong Deng, Pablo R Dias, Megan Jones in AIMS Energy
The renewable energy sector is facing a quandary: how Australia will dispose of 80 million solar panels in an environmentally friendly way when they reach the end of their life.
Paradoxically, one of the reasons people are installing solar photovoltaic (PV) panels in huge numbers is to help the environment, but the industry is now grappling with the anticipated waste generated by 100,000 tonnes of panels due to be dismantled in Australia from 2035.
A new study led by the University of South Australia has proposed a comprehensive product stewardship scheme for solar panels, which was prioritised by the Federal Government several years ago. In a paper, UniSA researcher Professor Peter Majewski says incentives are needed for producers to design solar panels that can be more easily recycled if they are damaged or out of warranty.
“Australia has one of the highest uptakes of solar panels in the world, which is outstanding, but little thought has been given to the significant volume of panels ending up in landfill 20 years down the track when they need to be replaced,” Prof Majewski says. “There are some simple recycling steps that can be taken to reduce the waste volume, including removing the panels’ frames, glass covers and solar connectors before they are disposed of.
“Landfill bans are already in place in Victoria, following the lead of some European countries, encouraging existing installers to start thinking about recyclable materials when making the panels.”
Prof Majewski says landfill bans are a powerful tool but require legislation that ensures waste is not just diverted to other locations with less stringent regulations. Serial numbers that can track a history of solar panels could also monitor their recycling use and ensure they are disposed of in an environmentally friendly way.
“Several European nations have legislation in place for electric car manufacturers to ensure they are using materials that allow 85 per cent of the car to be recycled at the end of their life. Something similar could be legislated for solar panels.”
Weatherproof polymers used in solar panels pose environmental risks, releasing harmful hydro-fluorite gas when incinerated. Exposure to the gas can severely irritate and burn the eyes, causing headaches, nausea, and pulmonary edema in the worst cases, sometimes leaving permanent damage. Another primary material used in solar cells is silicon, the second most abundant material on Earth after oxygen and the most common conductor used in computer chips.
“The demand for silicon is huge, so it’s important it is recycled to reduce its environmental footprint.
“About three billion solar panels are installed worldwide, containing about 1.8 million tons of high-grade silicon, the current value of which is USD 7.2 billion. Considering this, recycling of solar PV panels has the potential to be commercially viable.”
Prof Majewski says a second-hand economy could also be generated by re-using solar panels that are still functioning.
“Solar panel re-use offers a variety of social and environmental benefits, but consumers will need guarantees that second-hand panels will work properly and provide a minimum capacity in watts.”
Any end-of-life legislation will need to address existing and new panels and support the creation of a second-hand economy, Prof Majewski says.
Quantifying the predictability of renewable energy data for improving power systems decision-making
by Sahand Karimi-Arpanahi, S. Ali Pourmousavi, Nariman Mahdav in Patterns
Lower electricity costs for consumers and more reliable clean energy could be some of the benefits of a new study by the University of Adelaide researchers who have examined how predictable solar or wind energy generation is and the impact of it on profits in the electricity market.
PhD candidate Sahand Karimi-Arpanahi and Dr Ali Pourmousavi Kani, Senior Lecturer from the University’s School of Electrical and Mechanical Engineering, have looked at different ways of achieving more predictable renewable energy with the aim of saving millions of dollars in operating costs, prevent clean energy spillage, and deliver lower-cost electricity.
“One of the biggest challenges in the renewable energy sector is being able to reliably predict the amount of power generated,” said Mr Karimi-Arpanahi. “Owners of solar and wind farms sell their energy to the market ahead of time before it is generated; however, there are sizable penalties if they don’t produce what they promise, which can add up to millions of dollars annually.
“Peaks and troughs are the reality of this form of power generation, however using predictability of energy generation as part of the decision to locate a solar or wind farm means that we can minimise supply fluctuations and better plan for them.”
The team’s research analysed six existing solar farms located in New South Wales, Australia and selected up to nine alternative sites, comparing the sites based on the current analysis parameters and when the predictability factor was also considered. The data showed that the optimal location changed when the predictability of energy generation was considered and led to a significant increase in the potential revenue generated by the site. Dr Pourmousavi Kani said the findings of this paper will be significant for the energy industry in planning new solar and wind farms and public policy design.
“Researchers and practitioners in the energy sector have often overlooked this aspect, but hopefully our study will lead to change in the industry, better returns for investors, and lower prices for the customer,” he said. “The predictability of solar energy generation is the lowest in South Australia each year from August to October while it is highest in NSW during the same period.
“In the event of proper interconnection between the two states, the more predictable power from NSW could be used to manage the higher uncertainties in the SA power grid during that time.”
The researchers’ analysis of the fluctuations in energy output from solar farms may be applied to other applications in the energy industry.
“The average predictability of renewable generation in each state can also inform power system operators and market participants in determining the time frame for the annual maintenance of their assets, ensuring the availability of enough reserve requirements when renewable resources have lower predictability,” said Dr Pourmousavi Kani.
U.S. West Coast droughts and heat waves exacerbate pollution inequality and can evade emission control policies
by Amir Zeighami, Jordan Kern, Andrew J. Yates, Paige Weber, August A. Bruno in Nature Communications
A new study led by North Carolina State University researchers found drought and heat waves could make air pollution worse for communities that already have a high pollution burden in California, and deepen pollution inequalities along racial and ethnic lines.
The study also found financial penalties for power plants can significantly reduce people’s pollution exposure, except during severe heat waves.
“We have known that air pollution disproportionally impacts communities of color, the poor and communities that are already more likely to be impacted by other sources of environmental pollution,” said the study’s lead author Jordan Kern, assistant professor of forestry and environmental resources at NC State. “What we know now is that drought and heat waves makes things worse.”
For the study, researchers estimated emissions of sulfur dioxide, nitrogen oxides and fine particulate matter from power plants in California across 500 different scenarios for what the weather could look like in future years, which they called “synthetic weather years.” These years simulated conditions that could occur based on historical wind, air, temperature and solar radiation values on the West Coast between 1953 and 2008. Then by using information about the location of power plants in California and how much electricity they would be generating under different weather conditions, they estimated air pollution within individual counties.
They saw the worst air pollution in the hottest, driest years, which Kern said is due to the demand for more air conditioning during hot years. In addition, drought can impact the availability of hydropower. The excess electricity has to come from somewhere else, which is where fossil fuel plants come in.
“One of the things we were interested in was teasing apart the relative roles of drought, which can be chronic, lasting for months or years, versus heat waves, which can happen like a flash in a pan,” Kern said. “We found drought is a driver of chronic pollution exposure, but heat waves are responsible for these incredible spikes in emissions in a short period of time.”
They also saw that counties with a higher existing pollution burden were disproportionately impacted by pollution during drought and heat waves. Counties that were more diverse by race and ethnicity were also far more likely to be impacted by increased emissions from power plants during droughts and heat waves.
“The more diverse your county is by race and ethnicity, the more likely you are to be impacted by air pollution on an annual basis,” Kern said. “During a drought, the relationship is more pronounced.”
When they simulated the impact of three different policies that taxed power generators for emitting air pollution locally, overall, or both, they found that penalties helped reduce pollution health damages in more than 99% of days. However, during extreme heat waves, penalties failed to reduce emissions.
“Penalties make the more damaging power plants more expensive to operate, while it makes clean power plants comparatively less expensive,” Kern said. “It incentivizes the system to switch to rely on more clean power plants, but that stops happening during really massive heat waves. The power operators have no choice but to turn on every power plant. They can’t switch from the dirty power plants to the clean ones.”
Roadmap on Energy Harvesting Materials
by Vincenzo Pecunia, S Ravi P Silva, Jamie Dean Phillips, Elisa Artegiani, Alessandro Romeo, Hongjae Shim, Jongsung Park, Jin-Hyeok Kim, Jae Sung Yun, Gregory Charles Welch in Journal of Physics: Materials
Simon Fraser University professor Vincenzo Pecunia has led a team of more than 100 internationally-recognized scientists in creating a comprehensive “roadmap” to guide global efforts to convert waste energy into clean power.
“With the rising global energy demand and the challenges posed by climate change, it is more urgent than ever to generate green energy to preserve our planet and sustain human development,” says Pecunia, from the School of Sustainable Energy Engineering, where he leads the Sustainable Optoelectronics Research Group.
“Energy harvesting materials present a promising opportunity to generate clean electricity, ultimately enhancing the energy efficiency of our daily lives and supporting our efforts to combat climate change. These materials have the ability to convert ambient energy from various sources including light, heat, radiofrequency waves (like those from Wi-Fi and mobile signals), and mechanical vibrations.”
To realize the full potential of energy harvesting technology, Pecunia and 116 leading experts from around the world have published their Roadmap on Energy Harvesting Materials. The roadmap pools expert perspectives on various types of energy harvesting, recent advances and challenges and also analyzes key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, it outlines strategies for future research to fully harness the potential of energy harvesting materials.
“This roadmap is the result of an unprecedented endeavour, marking the first time that such a large and diverse international network of energy harvesting experts — from America, Asia, Europe, and Oceania — have worked together to chart a course for the advancement of these technologies towards seamless integration into everyday objects and environments,” says Pecunia, lead author.
Smart systems are developing rapidly, making smart homes, smart cities, smart manufacturing and smart healthcare achievable. Sensors and systems are embedded in our daily lives through devices such as smartphones, fitness trackers and smart home assistant technologies. All of these operate as part of a wide network, known as the Internet of Things (IoT), that is constantly communicating and exchanging data.
“An area of tremendous potential involves using ambient energy harvesters to sustainably power the billions of sensor nodes being deployed for IoT,” explains Pecunia. “By providing an eco-friendly alternative to batteries (which face materials scarcity, toxicity, and waste issues), energy harvesters could sustainably power IoT sensors.”
Pecunia’s research group has made major contributions in this area, spearheading the generation of clean electricity from indoor light using printable semiconductors and their integration with printed electronics towards eco-friendly IoT sensors. Collecting energy from ambient light, vibrations and radiofrequency waves is challenging due to their limited power density.
“It’s essential to develop energy harvesting materials that can efficiently capture this energy and convert it to electricity,” he explains. “Another important priority is to develop energy harvesters that can be applied on all types of surfaces and objects, which requires energy harvesting materials that are mechanically flexible.”
The roadmap on energy harvesting technology is a united and global effort to help pave a path forward for researchers and leaders to help expedite the advancement of this research area.
“Our hope is to catalyze research efforts in energy harvesting research across multiple disciplines to ultimately deliver clean energy anywhere, anytime.”
Life cycle net energy assessment of sustainable H2 production and hydrogenation of chemicals in a coupled photoelectrochemical device
by Xinyi Zhang, Michael Schwarze, Reinhard Schomäcker, Roel van de Krol, Fatwa F. Abdi in Nature Communications
Hydrogen can be produced by electrolysis of water, ideally with solar cells or wind power providing the electrical energy required. This “green” hydrogen is expected to play an important role in the energy system of the future. Over the past decade, solar water splitting has made considerable progress: the best electrolysers, which draw the required voltage from PV modules or wind power, already achieve efficiencies of up to 30%. This is the indirect approach.
At the HZB Institute for Solar Fuels, several teams are working on a direct approach to solar water splitting: they are developing photoelectrodes that convert sunlight into electrical energy, are stable in aqueous solutions, and catalytically promote water splitting. These photoelectrodes consist of light absorbers that are intimately coupled to catalyst materials to form the active component of a photoelectrochemical cell (PEC). The best PEC cells based on low-cost and stable metal oxide absorbers already achieve efficiencies close to 10%. Although PEC cells are still less efficient than PV-driven electrolyzers, they also have important advantages: in PEC cells, for example, the heat from sunlight can be used to further accelerate the reactions. And because current densities are ten to a hundred times lower with this approach, it is possible to use abundant and very inexpensive materials as catalysts.
So far, techno-economic analyses (TEA) and net energy assessments (NEA) have shown that the PEC approach is not yet competitive for large-scale implementation. Hydrogen from PEC systems today costs about 10 USD/kg, about 6 times more than hydrogen from fossil methane steam reforming (1.5 USD/kg). Moreover, the cumulative energy demand for PEC water splitting is estimated to be 4–20 times higher than for hydrogen production with wind turbines and electrolysers.
“This is where we wanted to bring a new approach,” says Dr Fatwa Abdi from the HZB Institute for Solar Fuels. Within the framework of the UniSysCat excellence network collaboration between Prof Reinhard Schomäcker and Prof Roel van de Krol, Abdi’s group investigated how the balance changes when some of the hydrogen produced reacts further with itaconic acid (IA) in the same reactor (in situ) to form methyl succinic acid (MSA).
They first calculated how much energy is needed to produce the PEC cell from light absorbers, catalyst materials and other materials such as glass, and how long it has to function to produce this energy in the form of chemical energy as hydrogen or MSA. For hydrogen alone, this ‘energy payback time’ is around 17 years assuming a modest 5% solar-to-hydrogen efficiency. If only 2% of the hydrogen produced is used to convert IA into MSA, the energy payback time is halved, and if 30% of the hydrogen is converted into MSA, the production energy can be regained after just 2 years. “This makes the process much more sustainable and competitive,” says Abdi. One reason: the energy needed to synthesise MSA in such a PEC cell is only one-seventh of the energy need of conventional MSA production processes.
“The system is flexible and can also produce other valuable chemicals that are currently needed at the site,” explains Abdi. The advantage is that the fixed components of the PEC unit, which account for most of the investment costs, remain the same; only the hydrogenation catalyst and the feedstock need to be exchanged.
“This approach offers a way to significantly reduce the production cost of green hydrogen and increases the economic feasibility of PEC technology,” Abdi says. “We have carefully thought through the process, and the next step is to test in the laboratory how well the simultaneous production of hydrogen and MSA works in practice.”
Investigating high methane emissions from urban areas detected by TROPOMI and their association with untreated wastewater
by Benjamin de Foy, James J Schauer, Alba Lorente, Tobias Borsdorff in Environmental Research Letters
Research has shown that methane emissions from urban areas are underestimated by a factor of three to four and that untreated wastewater may be a contributing factor.
The study was led by Benjamin de Foy, Ph.D., professor of Earth and Atmospheric Sciences at Saint Louis University. The researchers found that methane emissions from the discharge of untreated wastewater are a major contributor to global methane emissions and that improving wastewater treatment in urban areas could lead to a significant reduction in greenhouse gas emissions, helping cities on a quest for carbon neutrality.
“We estimate that reducing discharges of untreated wastewater could reduce global methane emissions by up to 5 to 10%,” said de Foy. “This could also yield significant ecological and human benefits.”
The two largest contributors to climate change are carbon dioxide and methane. In 2021, global methane concentrations increased at the highest rates on record and current estimates of methane emissions inventory cannot explain recent trends. One method of evaluating methane emission is via satellite remote sensing, for example, with the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel 5 Precursor satellite. This has been measuring methane and other air pollutants all around the world since November 2017.
The research shows that methane emissions from urban areas may be underestimated by a factor of 3 to 4 in the Emissions Database for Global Atmospheric Research (EDGAR) greenhouse gas emission inventory. The study scaled the results to 385 urban areas worldwide with more than 2 million inhabitants each, suggesting that they could account for up to 22% of global methane emissions. The emission estimates of the 61 urban areas do not correlate with the total or sectoral EDGAR emission inventory. They do however correlate with estimated rates of untreated wastewater, varying from 33 kg of methane per person per year for cities with zero untreated wastewater to 138 kg of methane per person per year for the cities with the most untreated wastewater.
The study looked at different scenarios for reducing emissions in the 61 urban areas, as well as for all areas with a population of more than 2 million. By reducing the emissions of the 33 cities with medium to high levels of untreated wastewater to the mean emissions of cities with zero to low untreated wastewater emissions, 2% of the worldwide emissions total could be cut. If all 61 cities reduced their emissions to the lowest rate, that would cut 6% of total worldwide methane emissions. The researchers’ model points to untreated wastewater rather than other options, including natural gas leaks or older infrastructure, as a large share of overall methane emissions.
“Our estimates of methane emissions suggest that there is methane formation in the environment as a result of the release of untreated wastewater which is much larger than the estimates in current inventories,” said de Foy. “Some urban areas could reduce their emissions 50% or more by fully treating all their wastewater.”
The researchers say more work is needed to bridge the gap between inventories and measurements to create a more refined global emission inventory and identify more precisely the varying emissions from city to city. For example, cities in Europe and China emit much less methane than those in North America and Asia.
De Foy said that there can be large differences within countries, noting Milwaukee has a large methane enhancement but neighboring Minneapolis does not, which could be due to differences in how stormwater and sewage are handled. One hundred fifty countries have committed to reducing their methane emissions by 30% by 2030 relative to 2020 as part of the Global Methane Pledge. Improved wastewater treatment could make a significant contribution to this goal.
Cellulose Nanocrystals Derived from Microcrystalline Cellulose for Selective Removal of Janus Green Azo Dye
by Ruchi Aggarwal, Anjali Kumari Garg, Deepika Saini, Sumit Kumar Sonkar, Amit Kumar Sonker, Gunnar Westman in Industrial & Engineering Chemistry Research
Researchers at Chalmers University of Technology, Sweden, have developed a new method that can easily purify contaminated water using a cellulose-based material. This discovery could have implications for countries with poor water treatment technologies and combat the widespread problem of toxic dye discharge from the textile industry.
Clean water is a prerequisite for our health and living environment, but far from a given for everyone. According to the World Health Organization, WHO, there are currently over two billion people living with limited or no access to clean water. This global challenge is at the centre of a research group at Chalmers University of Technology, which has developed a method to easily remove pollutants from water. The group, led by Gunnar Westman, Associate Professor of Organic Chemistry focuses on new uses for cellulose and wood-based products and is part of the Wallenberg Wood Science Center.
The researchers have built up solid knowledge about cellulose nanocrystals* — and this is where the key to water purification lies. These tiny nanoparticles have an outstanding adsorption capacity, which the researchers have now found a way to utilise.
“We have taken a unique holistic approach to these cellulose nanocrystals, examining their properties and potential applications. We have now created a biobased material, a form of cellulose powder with excellent purification properties that we can adapt and modify depending on the types of pollutants to be removed,” says Gunnar Westman.
In a study, the researchers show how toxic dyes can be filtered out of wastewater using the method and material developed by the group. The research was conducted in collaboration with the Malaviya National Institute of Technology Jaipur in India, where dye pollutants in textile industry wastewater are a widespread problem. The treatment requires neither pressure nor heat and uses sunlight to catalyse the process. Gunnar Westman likens the method to pouring raspberry juice into a glass with grains of rice, which soak up the juice to make the water transparent again.
“Imagine a simple purification system, like a portable box connected to the sewage pipe. As the contaminated water passes through the cellulose powder filter, the pollutants are absorbed and the sunlight entering the treatment system causes them to break down quickly and efficiently. It is a cost-effective and simple system to set up and use, and we see that it could be of great benefit in countries that currently have poor or non-existent water treatment,” he says.
India is one of the developing countries in Asia with extensive textile production, where large amounts of dyes are released into lakes, rivers and streams every year. The consequences for humans and the environment are serious. Water contaminant contains dyes and heavy metals and can cause skin damage with direct contact and increase the risk of cancer and organ damage when they enter into the food chain. Additionally, nature is affected in several ways, including the impairment of photosynthesis and plant growth.
Conducting field studies in India is an important next step, and the Chalmers researchers are now supporting their Indian colleagues in their efforts to get some of the country’s small-scale industries to test the method in reality. So far, laboratory tests with industrial water have shown that more than 80 percent of the dye pollutants are removed with the new method, and Gunnar Westman sees good opportunities to further increase the degree of purification.
“Going from discharging completely untreated water to removing 80 percent of the pollutants is a huge improvement, and means significantly less destruction of nature and harm to humans. In addition, by optimising the pH and treatment time, we see an opportunity to further improve the process so that we can produce both irrigation and drinking water. It would be fantastic if we can help these industries to get a water treatment system that works, so that people in the surrounding area can use the water without risking their health,” he says.
Gunnar Westman also sees great opportunities to use cellulose nanocrystals for the treatment of other water pollutants than dyes. In a previous study, the research group has shown that pollutants of toxic hexavalent chromium, which is common in wastewater from mining, leather and metal industries, could be successfully removed with a similar type of cellulose-based material. The group is also exploring how the research area can contribute to the purification of antibiotic residues.
“There is great potential to find good water purification opportunities with this material, and in addition to the basic knowledge we have built up at Chalmers, an important key to success is the collective expertise available at the Wallenberg Wood Science Center,” he says.
Closed-loop recycling of microparticle-based polymers
by Takumi Watanabe, Haruka Minato, Yuma Sasaki, Seina Hiroshige, et al in Green Chemistry
The ever-increasing generation of plastic solid waste has resulted in global plastic pollution both on land and in the oceans. Projections show that plastic waste will double in the next 20 years, causing further environmental problems. Large amounts of plastic waste are, at present, incinerated or deposited in landfills. This not only degrades the environment but also depletes valuable resources.
In this light, recycling plastics such as polymers is a promising sustainable alternative for waste management. But this involves the breaking of chemical bonds between monomers (building blocks of polymers), which diminishes their overall stability and quality. Addressing this concern, researchers have developed methods to recycle polymers in a “closed loop,” that is, without the loss of these properties. However, these methods are complicated and expensive and require specialized monomers, necessitating further innovation.
In this direction, a group of researchers led by Daisuke Suzuki, an Associate Professor at Shinshu University, has recently proposed a closed-loop recycling process based on polymer microparticles. Their work, co-authored by Dr. Takumi Watanabe and Dr. Haruka Minato of Shinshu University, has been published in the journal Green Chemistry.
Prof. Suzuki briefly explains the rationale behind their strategy: “Recycling materials without deterioration (closed-loop recycling) is attractive in terms of reducing anthropogenic waste. However, this currently remains very difficult given that there usually is a trade-off between mechanical stability and degradability of polymer materials. Our material recycling concept with microparticles enables the recycling of a huge amount of functional polymer materials that we use in our day-to-day lives and has the potential to solve the problems of resource depletion and environmental pollution.”
In their study, the authors prepared polymer microparticles via the aqueous emulsion polymerization of methyl acrylate (MA) monomers in water, which resulted in polymer chains. These aggregated to form a solution containing uniform spherical poly-MA microparticles. The solution was then dried to get a thin polymer film with physical (as opposed to chemical) cross-linking among the microparticles, which could be reobtained by dissolving the film in ethanol. These recycled microparticles, in turn, could be reused to form various recycled materials.
The films synthesized in this work exhibit several desirable properties, which they retain upon recycling. They have high mechanical stability and fracture energy, which is an indicator of their toughness. The latter property increases with the interfacial thickness between the poly-MA microparticles. This, in turn, decreases with the degree of interparticle cross-linking but increases upon heating the film.
The researchers further enhanced the fracture energy of the polymer films by mixing the microparticles with silica nanofillers. Moreover, adding colored pigments gave the resulting composite films tunable optical properties, which did not diminish upon recycling. These results suggest that closed-loop recycling based on polymer microparticles will enable resource circulation for polymers as well as numerous other composite materials that contain polymer microparticles to create adhering interfaces between their different layers.
Concludingly, Prof. Suzuki highlights the future potential of the present work. “Our concept can lead to the production of fully recyclable films with high fracture energy. Therefore, it will enable the recycling of huge amounts of various polymer materials, thus reducing plastic waste and potentially solving the problems of environmental degradation and plastic pollution.”
Electrochemical degradation of PFOA and its common alternatives: Assessment of key parameters, roles of active species, and transformation pathway
by Fatemeh Asadi Zeidabadi, Ehsan Banayan Esfahani, Sean T. McBeath, Kristian L. Dubrawski, Madjid Mohseni in Chemosphere
Engineers at the University of British Columbia have developed a new water treatment that removes “forever chemicals” from drinking water safely, efficiently — and for good.
Forever chemicals, formally known as PFAS (per-and polyfluoroalkyl substances) are a large group of substances that make certain products non-stick or stain-resistant. There are more than 4,700 PFAS in use, mostly in raingear, non-stick cookware, stain repellents and firefighting foam. Research links these chemicals to a wide range of health problems including hormonal disruption, cardiovascular disease, developmental delays and cancer.
To remove PFAS from drinking water, Dr. Mohseni and his team devised a unique adsorbing material that is capable of trapping and holding all the PFAS present in the water supply. The PFAS are then destroyed using special electrochemical and photochemical techniques, also developed at the Mohseni lab and described in part in a new paper published recently in Chemosphere. While there are treatments currently on the market, like activated carbon and ion-exchange systems which are widely used in homes and industry, they do not effectively capture all the different PFAS, or they require longer treatment time, Dr. Mohseni explained.
“Our adsorbing media captures up to 99 per cent of PFAS particles and can also be regenerated and potentially reused. This means that when we scrub off the PFAS from these materials, we do not end up with more highly toxic solid waste that will be another major environmental challenge.”
He explained that while PFAS are no longer manufactured in Canada, they are still incorporated in many consumer products and can then leach into the environment. For example, when we apply stain-resistant or repellent sprays/materials, wash PFAS-treated raingear, or use certain foams to put down fires, the chemicals end up in our waterways. Or when we use PFAS-containing cosmetics and sunscreens, the chemicals could find their way into the body. For most people, exposure is through food and consumer products, but they can also be exposed from drinking water — particularly if they live in areas with contaminated water sources.
Dr. Mohseni, whose research group also focuses on developing water solutions for rural, remote and Indigenous communities, noted: “Our adsorbing media are particularly beneficial for people living in smaller communities who lack resources to implement the most advanced and expensive solutions that could capture PFAS. These can also be used in the form of decentralized and in-home water treatments.”
“The results we obtain from these real-world field studies will allow us to further optimize the technology and have it ready as products that municipalities, industry and individuals can use to eliminate PFAS in their water,” said Dr. Mohseni.
Nitrate-Stimulated Release of Naturally Occurring Sedimentary Uranium
by Jeffrey P. Westrop, Pooja Yadav, PJ Nolan, Kate M. Campbell, Rajesh Singh, Sharon E. Bone, Alicia H. Chan, Anthony J. Kohtz, Donald Pan, Olivia Healy, John R. Bargar, Daniel D. Snow, Karrie A. Weber in Environmental Science & Technology
Eight years ago, the data was sound but only suggestive, the evidence strong but circumstantial. Now, the University of Nebraska-Lincoln’s Karrie Weber and colleagues have experimentally confirmed that nitrate, a compound common in fertilizers and animal waste, can help transport naturally occurring uranium from the underground to groundwater.
Their new research backs a 2015 Weber-led study showing that aquifers contaminated with high levels of nitrate — including the High Plains Aquifer residing beneath Nebraska — also contain uranium concentrations far exceeding a threshold set by the Environmental Protection Agency. Uranium concentrations above that EPA threshold have been shown to cause kidney damage in humans, especially when regularly consumed via drinking water.
“Most Nebraskans do rely on groundwater as drinking water,” said Weber, associate professor in the School of Biological Sciences and Department of Earth and Atmospheric Sciences. “In Lincoln, we rely on it. A lot of rural communities, they’re relying on groundwater. “So when you have high concentrations (of uranium), that becomes a potential concern.”
Research had already established that dissolved inorganic carbon could chemically detach traces of natural, non-radioactive uranium from underground sediment, ultimately priming it for transport into groundwater. But the 2015 study, which found that certain areas of the High Plains Aquifer contained uranium levels up to 89 times the EPA threshold, had convinced Weber that nitrate was contributing, too. So, with the help of 12 colleagues, Weber set out to test the hypothesis. To do it, the team extracted two cylindrical cores of sediment — each roughly 2 inches wide and running 60 feet deep — from an aquifer site near Alda, Nebraska. That site not only contains natural traces of uranium, the researchers knew, but also allows groundwater to flow east into the adjacent Platte River. Their goal? Recreate that flow in the samples of sediment, then determine whether adding some nitrate to the water would increase the amount of uranium that got carried away with it.
“One of the things we wanted to make sure of was that we did not alter the state of the uranium or the sediments or the (microbial) community when we collected the samples,” Weber said. “We did everything we could to preserve natural conditions.”
“Everything” meant immediately capping and wax-sealing the extracted cores, sliding them into airtight tubes, flushing those tubes with argon gas to dispel any oxygen, and putting them on ice. Back at the lab, Weber and her colleagues would eventually remove 15-inch segments from each of the two cores. Those segments consisted of sand and also silt that contained relatively high levels of uranium.
Later, the team would fill multiple columns with that silt before pumping simulated groundwater through them at roughly the same rate it would have traveled underground. In some cases, that water contained nothing extra. In others, the researchers added nitrate. And in still other cases, they added both nitrate and an inhibitor designed to halt the biochemical activity of microorganisms living in the sediment.
The water containing nitrate, but lacking the microbial inhibitor, managed to carry away roughly 85% of the uranium — compared with just 55% when the water lacked nitrate and 60% when it contained nitrate but also the inhibitor. Those results implicated both the nitrate and the microbes in further mobilizing the uranium.
They also supported the hypothesis that a series of biochemical events, kicked off by the microbes, was transforming the otherwise-solid uranium into a form that could be easily dissolved in water. First, bacteria living in the sediment donate electrons to the nitrate, catalyzing its transformation into a compound called nitrite. That nitrite then oxidizes — steals electrons from — the neighboring uranium, ultimately turning it from a solid mineral into an aqueous one ready to surf the trickle of water seeping through the silt.
After analyzing DNA sequences present in its sediment samples, the team identified multiple microbial species capable of metabolizing nitrate to nitrite. Though that uranium-mobilizing biochemistry had been known to unfold in highly contaminated areas — uranium mines, sites where nuclear waste is processed — Weber said the new study is the first to establish that the same mobilization process also takes place in natural sediment.
“When we first got this project funded, and we were thinking about this, it was as a primary contaminant leading to secondary contamination,” she said of the nitrate and uranium. “This research supports that, yes, that can happen.”
Still, as Weber said, “Nitrate isn’t always a bad thing.” Both her previous research and some forthcoming studies suggest that nitrate mobilizes uranium only when the compound approaches its own EPA threshold of 10 parts per million.
“If we reflect upon what we published prior, that data suggests there’s a tipping point. The important thing,” she said, “is not to have too much.”
MISC
Subscribe to Paradigm!
Medium. Twitter. Telegram. Telegram Chat. Reddit. LinkedIn.
Main Sources
Research articles
