GT/ Cost-effective flexible polymer solar cells
Energy & green technology biweekly vol.23, 22d April — 6th May
TL;DR
- A research team has used electron spin resonance spectroscopy to investigate a polymer solar cell while in operation. Molecular level comparison of the PTzBT/PC61BM system with and without added ITIC allowed them to establish the mechanism for the improvements in stability and power conversion efficiency observed when ITIC is added. It is hoped that this insight will contribute to the commercial realization of cost-effective flexible polymer solar cells.
- A research has developed new, highly efficient and stable perovskite solar cells. The breakthrough invention is expected to greatly accelerate the commercialization of perovskite photovoltaic technology, providing a promising alternative to silicon solar cells.
- A new approach to battery design could provide the key to low-cost, long-term energy storage, according to researchers.
- An experimental plant-based jet fuel could increase engine performance and efficiency, while dispensing with aromatics, the pollution-causing compounds added to conventional fuels, according to new research.
- Researchers have developed a hydrogen fuel cell that uses iron instead of rare and costly platinum, enabling greater use of the technology.
- New solar cell devices that are cheaper and easier to make could soon make their way to market thanks to new materials.
- An enzyme variant created by engineers and scientists can break down environment-throttling plastics that typically take centuries to degrade in just a matter of hours to days.
- An international group of experts says the production of new plastics should be capped to solve the plastic pollution problem. The authors argue that all other measures won’t suffice to keep up with the pace of plastic production and releases.
- While most missions to the moon and other planets rely upon solar power, scientists have assumed that any extended surface mission involving humans would require a more reliable source of energy: nuclear power. Improvements in photovoltaics are upending this calculus. A new study concludes that a solar power system would weigh less than a nuclear system, and would be sufficient to power a colony at sites over nearly half the surface.
- Polyethylene accounts for nearly one-third of the world’s plastic waste. An interdisciplinary team has now investigated the progressive degradation of polyethylene in the environment for the first time. Although the degradation process leads to fragmentation into ever smaller particles, isolated nanoplastic particles are rarely found in the environment. The reason is that such decay products do not like to remain on their own, but rather attach rapidly to larger colloidal systems that occur naturally in the environment.
- 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
Stability improvement mechanism due to less charge accumulation in ternary polymer solar cells
by Dong Xue, Masahiko Saito, Itaru Osaka, Kazuhiro Marumoto in npj Flexible Electronics
Solar cells will doubtless play a significant part in a sustainable energy future. Polymer solar cells (PSCs) specifically provide an excellent option because they are cheap to produce and can be both flexible and semitransparent. Ternary polymer solar cells are showing encouraging power conversion efficiencies, but it isn’t always clear why. Now, researchers from the University of Tsukuba and Hiroshima University have taken a closer look at PSCs in operation.
PSCs generally contain a material that is the p-type semiconductor mixed with one that is the n-type semiconductor. This blend gives the right combination of charge carriers — holes and electrons — for a current to flow when sunlight shines on the cell. Blends with these two components are known as binary PSCs. However, it has recently been found that adding an extra ingredient to the mix — giving what is known as a ternary PSC — can improve the power conversion efficiency (PCE) and stability of the solar cell. The trouble is that up until now nobody has thoroughly investigated why.
The researchers therefore conducted electron spin resonance (ESR) spectroscopy while the PSC was operating. This gave them the chance to observe the behavior of the electrons and holes when the cell was irradiated with sunlight and to get answers on a molecular level.
“It has been reported that the accumulation of charge over time contributes to the performance of cells deteriorating,” explain study author Professor Itaru Osaka and study corresponding author Professor Kazuhiro Marumoto. “We therefore used ESR to look at a system made up of the polymer PTzBT and large molecule PC61BM. It has been found that adding an acceptor molecule, known as ITIC, to this system improves the PCE and the stability of the cell, so we looked closely at cells with and without ITIC to determine why.”
The ESR spectroscopy experiment showed that the short-circuit current decreased as a result of the accumulation of electrons in the PC61BM and holes in PTzBT. Adding ITIC was found to reduce this accumulation by enhancing the orientation of the chainlike PTzBT polymer molecules in the active layer.
“Being able to understand why something works is important for ensuring that effects are optimized to their full potential,” says study corresponding author Professor Kazuhiro Marumoto. “By getting a molecular level picture of the effects of ITIC on a very promising PSC system, we believe we have taken a step closer to the commercial reality of polymer solar cells as part of a greener future.”
Controlling Ni redox states by dynamic ligand exchange for electroreductive Csp3–Csp2 coupling
by Taylor B. Hamby, Matthew J. LaLama, Christo S. Sevov in Science
A research team co-led by chemists from City University of Hong Kong (CityU) and Imperial College London (Imperial College) has developed new, highly efficient and stable perovskite solar cells. The breakthrough invention is expected to greatly accelerate the commercialisation of perovskite photovoltaic technology, providing a promising alternative to silicon solar cells.
Traditional solar cells are made of silicon, which has high power conversion efficiency and good stability. But they are relatively expensive and are reaching their practical and economic photovoltaic efficiency limits. Perovskites are regarded as the leading contender to replace silicon as the material of choice for solar panels. Perovskite solar cells are expected to cost less, have a low-manufacturing temperature, and are lightweight and flexible. They can be printed on plastic films as flexible solar cells, or can be used as window glass coating to absorb sunlight, offering wide usability.
Among the different types of perovskite solar cells, those with an inverted design configuration have exhibited exceptional stability, making them good candidates to reach the lifetime of commercial silicon solar cells. However, perovskite materials include chemically reactive components, which can easily volatilise and degrade under high temperature and humidity, shortening the solar cells’ operational lifetime. And there was still a lack of strategy to enhance the efficiency of inverted perovskite solar cells up to 25% to rival that of silicon solar cells, while maintaining their stability.
Inspired by the unique properties of a metal-containing material called ferrocenes, Dr Zhu Zonglong, Assistant Professor in CityU’s Department of Chemistry, overcame these obstacles with a new approach. In collaboration with Professor Nicholas Long from Imperial College, Dr Zhu’s team ingeniously added ferrocenes to perovskite solar cells as an interface between the light-absorbing layer and the electron transporting layer, achieving a breakthrough. “We are the first team to successfully boost inverted perovskite solar cells to a record-high efficiency of 25% and pass the stability test set by the International Electrotechnical Commission (IEC),” said Dr Zhu.
“The unique properties of ferrocenes can help overcome the problems with perovskite solar cells,” said Professor Long, who is an expert in organometallic chemistry. Ferrocene is a compound with an iron atom “sandwiched” between two planar carbon rings. Dr Zhu’s team employed ferrocene, in which the carbon rings are attached to different organic groups, developed by Professor Long’s team. “These organic groups reduce the reactivity of the perovskite surface, enhancing both efficiency and stability,” Dr Zhu explained.
Perovskite solar cells are made up of layers of materials. The perovskite layer is for light harvesting. The ferrocene molecules accelerate electron transfer from the perovskite active layer to the electrode in the electricity conversion layer, thus increasing efficiency.
Another merit of these organic groups, explained Dr Zhu is that “the ferrocene-based organometallic compound designed by the joint team firmly anchors the ion on the perovskite surface via a strong chemical bond, reducing the solar cells’ sensitivity to the external environment and delaying the device degradation process.”
In the experiment, the CityU team found that these newly invented solar cells can run under continuous illumination for more than 1,500 hours and still maintain more than 98% of their initial efficiency. The devices also passed the international standard for mature photovoltaics, exhibiting superior stability in a hot and humid environment (85 degrees Celsius and 85% humidity).
“The most important part of this work is that we successfully fabricated highly efficient perovskite solar cells while providing promising stability. The reliable results mean that the commercialisation of perovskites is on its way,” said Dr Zhu.
The collaboration team patented their design. “We aim to scale up the production of perovskite solar cells using this novel molecule and facile method, contributing to the global ‘zero-carbon’ sustainability goal,” concluded Dr Zhu.
A cost-effective alkaline polysulfide-air redox flow battery enabled by a dual-membrane cell architecture
by Yuhua Xia, Mengzheng Ouyang, Vladimir Yufit, Rui Tan, Anna Regoutz, Anqi Wang, Wenjie Mao, Barun Chakrabarti, Ashkan Kavei, Qilei Song, Anthony R. Kucernak, Nigel P. Brandon in Nature Communications
A new approach to battery design could provide the key to low-cost, long-term energy storage, according to Imperial College London researchers.
The team of engineers and chemists have created a polysulfide-air redox flow battery (PSA RFB) with not one, but two membranes. The dual membrane design overcomes the main problems with this type of large-scale battery, opening up its potential to store excess energy from, for example, renewable sources such as wind and solar.
In redox flow batteries, energy is stored in liquid electrolytes which flow through the cells during charge and discharge, enabled through chemical reactions. The amount of energy stored is determined by the volume of the electrolyte, making the design potentially easy to scale up. However, the electrolyte used in conventional redox flow batteries — vanadium — is expensive and primarily sourced from either China or Russia.
The Imperial team, led by Professors Nigel Brandon and Anthony Kucernak, have been working on alternatives that use lower cost materials which are widely available. Their approach uses a liquid as one electrolyte and a gas as the other — in this case polysulfide (sulphur dissolved in an alkaline solution) and air. However, the performance of polysulfide-air batteries is limited because no membrane could fully enable the chemical reactions to take place while still preventing polysulfide crossing over into the other part of the cell.
Dr Mengzheng Ouyang, from Imperial’s Department of Earth Science and Engineering, explained: “If the polysulfide crosses over into the air side, then you lose material from one side, which reduces the reaction taking place there and inhibits the activity of the catalyst on the other. This reduces the performance of the battery — so it was a problem we needed to solve.”
The alternative devised by the researchers was to use two membranes to separate the polysulfide and the air, with a solution of sodium hydroxide between them. The advantage of the design is that all materials, including the membranes, are relatively cheap and widely available, and that the design provides far more choice in the materials that can be used. When compared with the best results obtained to date from a polysulfide-air redox flow battery, the new design was able to provide significantly more power, up to 5.8 milliwatts per centimetre squared.
As cost is a critical factor for long-term and large-scale storage, the team also carried out a cost analysis. They calculated the energy cost — the price of the storage materials in relation to the amount of energy stored — to be around $2.5 per kilowatt hour. The power cost — the rate of charge and discharge achieved in relation to the price of the membranes and catalysts in the cell — was found to be around $1600 per kilowatt. This is currently higher than would be feasible for large-scale energy storage, but the team believe further improvements are readily achievable.
Professor Nigel Brandon, who is also Dean of the Faculty of Engineering, said: “Our dual-membrane approach is very exciting as it opens up many new possibilities, for both this and other batteries. To make this cost effective for large-scale storage, a relatively modest improvement in performance would be required, which could be achieved by changes to the catalyst to increase its activity or by further improvements in the membranes used.”
Work in this area is already underway within the team, through the catalyst expertise of Professor Anthony Kucernak, from the Department of Chemistry, and research into membrane technology by Dr Qilei Song from the Department of Chemical Engineering.
The spin-out company RFC Power Ltd, established to develop long-duration storage of renewable energy based on the team’s research, is set to commercialise this new design should the improvements be made.
CEO of RFC Power Ltd, Tim Von Werne, said: “There is a pressing need for new ways to store renewable energy over days, weeks or even months at a reasonable cost. This research shows a way to make that possible through improved performance and low-cost materials.”
Lignin-based jet fuel and its blending effect with conventional jet fuel
by Zhibin Yang, Zhangyang Xu, Maoqi Feng, John R. Cort, Rafal Gieleciak, Joshua Heyne, Bin Yang in Fuel
An experimental plant-based jet fuel could increase engine performance and efficiency, while dispensing with aromatics, the pollution-causing compounds added to conventional fuels, according to new research.
In a study, researchers analyzed a Washington State University-developed jet fuel based on lignin, an organic polymer that makes plants tough and woody. Using a range of tests and predictions, the researchers examined fuel properties critical to jet engine operation, including seal swell, density, efficiency, and emissions. Their results suggest that this sustainable fuel could be mixed with other biofuels to fully replace petroleum-derived fuels.
“When we tested our lignin jet fuel, we saw some interesting results,” said Bin Yang, professor with WSU’s Department of Biological Systems Engineering and corresponding author on the study. “We found that it not only had increased energy density and content but also could totally replace aromatics, which are a real problem for the aviation industry.”
“Aromatics are associated with increased soot emissions, as well as contrails, which are estimated to contribute more to the climate impact of aviation than carbon dioxide,” said Joshua Heyne, co-author, University of Dayton scientist and current co-director of the joint WSU-Pacific Northwest National Laboratory Bioproducts Institute. “Aromatics are still used in fuel today because we do not have solutions to some of the problems they solve: they provide jet fuel with a density that other sustainable technologies do not. Most unique is their ability to swell the O-rings used to seal metal-to-metal joints, and they do this well.”
“We want to fly safely, sustainably, and with the lowest impact to human health,” Heyne added. “The question is, how do we do all of this as economically as possible?”
Yang developed a patented process that turns lignin from agricultural waste into bio-based lignin jet fuel. Such sustainable fuel could help the aviation industry reduce dependance on increasingly expensive fossil fuels while meeting higher environmental standards.
The WSU-developed, lignin-based fuel’s properties “offer great opportunities for increasing fuel performance, higher fuel efficiency, reduced emission, and lower costs,” authors wrote in Fuel. “The fact that these molecules show sealant volume swell comparable with aromatics opens the door to develop jet fuels with virtually no aromatics, very low emissions, and very high-performance characteristics.”
“The lignin-based fuel we tested complements other sustainable aviation fuels by increasing the density and, perhaps most importantly, the ring-swelling potential of blends,” Heyne said. “While meeting our material needs, these sustainable blends confer higher energy densities and specific energies without using aromatics.”
“This process creates a cleaner, more energy-dense fuel,” Yang added. “That’s exactly what sustainable aviation fuels need for the future.”
High loading of single atomic iron sites in Fe–NC oxygen reduction catalysts for proton exchange membrane fuel cells
by Mehmood, A., Gong, M., Jaouen, F. et al. Nature Catalysis
Imperial researchers have developed a hydrogen fuel cell that uses iron instead of rare and costly platinum, enabling greater use of the technology.
Hydrogen fuel cells convert hydrogen to electricity with water vapour as the only by-product, making them an attractive green alternative for portable power, particularly for vehicles. However, their widespread use has been hampered in part by the cost of one of the primary components. To facilitate the reaction that produces the electricity, the fuel cells rely on a catalyst made of platinum, which is expensive and scarce.
Now, a European team led by Imperial College London researchers has created a catalyst using only iron, carbon, and nitrogen — materials that are cheap and readily available — and shown that it can be used to operate a fuel cell at high power.
Lead researcher Professor Anthony Kucernak, from the Department of Chemistry at Imperial, said: “Currently, around 60% of the cost of a single fuel cell is the platinum for the catalyst. To make fuel cells a real viable alternative to fossil-fuel-powered vehicles, for example, we need to bring that cost down.
“Our cheaper catalyst design should make this a reality, and allow deployment of significantly more renewable energy systems that use hydrogen as fuel, ultimately reducing greenhouse gas emissions and putting the world on a path to net-zero emissions.”
The team’s innovation was to produce a catalyst where all the iron was dispersed as single atoms within an electrically conducting carbon matrix. Single-atom iron has different chemical properties than bulk iron, where all the atoms are clustered together, making it more reactive. These properties mean the iron boosts the reactions needed in the fuel cell, acting as a good substitute for platinum. In lab tests, the team showed that a single-atom iron catalyst has performance approaching that of platinum-based catalysts in a real fuel cell system.
As well as producing a cheaper catalyst for fuel cells, the method the team developed to create could be adapted for other catalysts for other processes, such as chemical reactions using atmospheric oxygen as a reactant instead of expensive chemical oxidants, and in the treatment of wastewater using air to remove harmful contaminants.
First author Dr Asad Mehmood, from the Department of Chemistry at Imperial, said: “We have developed a new approach to make a range of ‘single atom’ catalysts that offer an opportunity to allow a range of new chemical and electrochemical processes. Specifically, we used a unique synthetic method, called transmetallation, to avoid forming iron clusters during synthesis. This process should be beneficial to other scientists looking to prepare a similar type of catalyst.”
Organometallic-functionalized interfaces for highly efficient inverted perovskite solar cells
by Zhen Li, Bo Li, Xin Wu, Stephanie A. Sheppard, Shoufeng Zhang, Danpeng Gao, Nicholas J. Long, Zonglong Zhu in Science
New solar cell devices that are cheaper and easier to make could soon make their way to market thanks to materials made at Imperial College London.
Traditional solar cells are made from silicon, which has good efficiency and stability, but is relatively expensive to make and can only be manufactured in stiff panels. Perovskite solar cells offer an intriguing alternative; they can be printed from inks, making them low cost, high efficiency, thin, lightweight and flexible. However, they have trailed behind silicon solar cells in efficiency and, importantly, stability, breaking down under normal environmental conditions.
New metal-containing materials called ferrocenes could help with these problems. Researchers from City University of Hong Kong (CityU) have added Imperial-made ferrocenes into perovskite solar cells, vastly improving their efficiency and stability.
Co-lead author Professor Nicholas Long, from the Department of Chemistry at Imperial, said: “Silicon cells are efficient but expensive, and we urgently need new solar energy devices to accelerate the transition to renewable energy. Stable and efficient perovskite cells could ultimately allow solar energy to be used in more applications — from powering the developing world to charging a new generation of wearable devices.
“Our collaboration with colleagues in Hong Kong was beautifully serendipitous, arising after I gave a talk about new ferrocene compounds and met Dr Zonglong Zhu from CityU, who asked me to send over some samples. Within a few months, the CityU team told us the results were exciting, and asked us to send more samples, beginning a research program that has resulted in perovskite devices that are both more efficient and more stable.”
Perovskite forms the ‘light-harvesting’ layer of solar cell devices. However, these devices have been less efficient at converting solar energy into electricity than silicon-based solar cells, primarily because the electrons are less ‘mobile’ — they are less able to move from the harvesting layer to the electricity conversion layers.
Ferrocenes are compounds with iron at their centre, surrounded by sandwiching rings of carbon. The unique structure of ferrocene was first recognised by Imperial’s own Nobel Prize-winner Professor Geoffrey Wilkinson in 1952, and ferrocenes are still being researched around the world today for their unique properties. One property their structure gives them is excellent electron richness, which in this case allows electrons to move more easily from the perovskite layer to subsequent layers, improving the efficiency of converting solar energy to electricity. Tests performed by the team CityU and in commercial labs show that the efficiency of perovskite devices with an added ferrocene layer can reach 25%, approaching the efficiency of traditional silicon cells.
But this isn’t the only problem the ferrocene-based materials solved. The team at Imperial have been experimenting with attaching different chemical groups to the carbon rings of ferrocene, and after sending the Hong Kong team several versions of these, made by PhD student Stephanie Sheppard, the collaborators discovered a version that significantly improves the attachment of the perovskite layers to the rest of the device. This added attachment power improved the stability of the devices, meaning they maintained more than 98% of their initial efficiency after continuously operating at maximum power for 1,500 hours. The efficiency and stability gained thanks to the addition of a ferrocene layer brings these perovskite devices close to current international standards for traditional silicon cells.
Lead researcher Dr Zonglong Zhu from CityU said: “We are the first team to successfully boost the inverted perovskite solar cell to a record-high efficiency of 25% and pass the stability test set by the International Electrotechnical Commission.”
The team have patented their design and hope to licence it, eventually bringing their perovskite devices to the market. In the meantime, they are experimenting with different ferrocene designs to further improve the performance and stability of the devices.
Machine learning-aided engineering of hydrolases for PET depolymerization
by Hongyuan Lu, Daniel J. Diaz, Natalie J. Czarnecki, Congzhi Zhu, Wantae Kim, Raghav Shroff, Daniel J. Acosta, Bradley R. Alexander, Hannah O. Cole, Yan Zhang, Nathaniel A. Lynd, Andrew D. Ellington, Hal S. Alper in Nature
An enzyme variant created by engineers and scientists at The University of Texas at Austin can break down environment-throttling plastics that typically take centuries to degrade in just a matter of hours to days.
This discovery could help solve one of the world’s most pressing environmental problems: what to do with the billions of tons of plastic waste piling up in landfills and polluting our natural lands and water. The enzyme has the potential to supercharge recycling on a large scale that would allow major industries to reduce their environmental impact by recovering and reusing plastics at the molecular level.
“The possibilities are endless across industries to leverage this leading-edge recycling process,” said Hal Alper, professor in the McKetta Department of Chemical Engineering at UT Austin. “Beyond the obvious waste management industry, this also provides corporations from every sector the opportunity to take a lead in recycling their products. Through these more sustainable enzyme approaches, we can begin to envision a true circular plastics economy.”
The project focuses on polyethylene terephthalate (PET), a significant polymer found in most consumer packaging, including cookie containers, soda bottles, fruit and salad packaging, and certain fibers and textiles. It makes up 12% of all global waste. The enzyme was able to complete a “circular process” of breaking down the plastic into smaller parts (depolymerization) and then chemically putting it back together (repolymerization). In some cases, these plastics can be fully broken down to monomers in as little as 24 hours.
Researchers at the Cockrell School of Engineering and College of Natural Sciences used a machine learning model to generate novel mutations to a natural enzyme called PETase that allows bacteria to degrade PET plastics. The model predicts which mutations in these enzymes would accomplish the goal of quickly depolymerizing post-consumer waste plastic at low temperatures. Through this process, which included studying 51 different post-consumer plastic containers, five different polyester fibers and fabrics and water bottles all made from PET, the researchers proved the effectiveness of the enzyme, which they are calling FAST-PETase (functional, active, stable and tolerant PETase).
“This work really demonstrates the power of bringing together different disciplines, from synthetic biology to chemical engineering to artificial intelligence,” said Andrew Ellington, professor in the Center for Systems and Synthetic Biology whose team led the development of the machine learning model.
Recycling is the most obvious way to cut down on plastic waste. But globally, less than 10% of all plastic has been recycled. The most common method for disposing of plastic, besides throwing it in a landfill, is to burn it, which is costly, energy intensive and spews noxious gas into the air. Other alternative industrial processes include very energy-intensive processes of glycolysis, pyrolysis, and/or methanolysis.
Biological solutions take much less energy. Research on enzymes for plastic recycling has advanced during the past 15 years. However, until now, no one had been able to figure out how to make enzymes that could operate efficiently at low temperatures to make them both portable and affordable at large industrial scale. FAST-PETase can perform the process at less than 50 degrees Celsius.
Up next, the team plans to work on scaling up enzyme production to prepare for industrial and environmental application. The researchers have filed a patent application for the technology and are eying several different uses. Cleaning up landfills and greening high waste-producing industries are the most obvious. But another key potential use is environmental remediation. The team is looking at a number of ways to get the enzymes out into the field to clean up polluted sites.
“When considering environmental cleanup applications, you need an enzyme that can work in the environment at ambient temperature. This requirement is where our tech has a huge advantage in the future,” Alper said.
A global plastic treaty must cap production
by Melanie Bergmann, Bethanie Carney Almroth, Susanne M. Brander, Tridibesh Dey, Dannielle S. Green, Sedat Gundogdu, Anja Krieger, Martin Wagner, Tony R. Walker in Science
Capping production of new plastics can help cut their release to the environment — and also brings other benefits, from boosting the value of recycled plastics to helping tackle climate change
Now, after the United Nations’ historic decision to adopt a global treaty to end plastic pollution earlier this year, governmental negotiations on the agreement are set to begin on May 30th. These will foster intense debates on what kind of measures will be needed to end the pollution of the air, soils, rivers and oceans with plastic debris and microplastics. In a letter to the journal Science, an international group of scientists and experts now argue for tackling the issue right at the source, by regulating, capping, and in the long term phasing out the production of new plastics.
“Even if we recycled better and tried to manage the waste as much as we can, we would still release more than 17 million tons of plastic per year into nature,” says Melanie Bergmann of the German Alfred-Wegener-Institute, the initiator of the letter. “If production just keeps growing and growing, we will be faced with a truly Sisyphean task,” she adds.
Research published in 2020 shows that plastic emissions can only be cut by 79 per cent over the next 20 years if all solutions available today are implemented, including replacing some plastics with other materials, and improved recycling and waste management.
“The exponentially growing production is really the root cause of the problem, and the amounts of plastics we have produced thus far have already exceeded planetary boundaries,” says Bethanie Carney Almroth of the University of Gothenburg, Sweden. “If we don’t tackle that, all other measures will fail to achieve the goal of substantially reducing the release of plastic into the environment,” she said.
Phasing out the production of new plastics from fresh feedstocks should be part of a systemic solution to end plastic pollution, the experts from Canada, Germany, India, Norway, Sweden, Turkey, the UK and the U.S. argue. This approach is supported by the best science available today and in line with what political and legal experts. Along with measures to address the consumption and demand side of the problem — such as taxes — a comprehensive approach must also cover the supply side, meaning the actual amount of plastics produced and put on the market. Gradually cutting the production of new plastics will come with many societal, environmental and economic benefits, the scientists say.
Sedat Gündodu of the Cukurova University, Turkey, says “The massive production also feeds the plastic waste transfer from the Global North to the South. A production cap will facilitate getting rid of non-essential applications and reduce plastic waste exports.”
“We gain a lot of benefits from plastics but reducing production will increase the value of plastics, boost other measures to curb plastic pollution, help tackle climate change and promote our transition to a circular and sustainable economy,” adds Martin Wagner, an ecotoxicologist at the Norwegian University of Science and Technology.
Photovoltaics-Driven Power Production Can Support Human Exploration on Mars
by Anthony J. Abel, Aaron J. Berliner, Mia Mirkovic, William D. Collins, Adam P. Arkin, Douglas S. Clark in Frontiers in Astronomy and Space Sciences
The high efficiency, light weight and flexibility of the latest solar cell technology means photovoltaics could provide all the power needed for an extended mission to Mars, or even a permanent settlement there, according to a new analysis by scientists at the University of California, Berkeley.
Most scientists and engineers who’ve thought about the logistics of living on the surface of the Red Planet have assumed that nuclear power is the best alternative, in large part because of its reliability and 24/7 operation. In the past decade, miniaturized Kilopower nuclear fission reactors have advanced to the point where NASA considers them to be a safe, efficient and plentiful source of energy and key to future robotic and human exploration.
Solar power, on the other hand, must be stored for use at night, which on Mars lasts about the same length of time as on Earth. And on Mars, solar panels’ power production can be reduced by the omnipresent red dust that covers everything. NASA’s nearly 15-year-old Opportunity rover, powered by solar panels, stopped working after a massive dust storm on Mars in 2019.
The new study uses a systems approach to actually compare these two technologies head-to-head for a six-person extended mission to Mars involving a 480-day stay on the planet’s surface before returning to Earth. That is the most likely scenario for a mission that reduces the transit time between the two planets and extends time on the surface beyond a 30-day window. Their analysis found that for settlement sites over nearly half the Martian surface, solar is comparable or better than nuclear, if you take into account the weight of the solar panels and their efficiency — as long as some daytime energy is used to produce hydrogen gas for use in fuel cells to power the colony at night or during sandstorms.
“Photovoltaic energy generation coupled to certain energy storage configurations in molecular hydrogen outperforms nuclear fusion reactors over 50% of the planet’s surface, mainly within those regions around the equatorial band, which is in fairly sharp contrast to what has been proposed over and over again in the literature, which is that it will be nuclear power,” said UC Berkeley bioengineering doctoral student Aaron Berliner, one of two first authors of the paper.
The study gives a new perspective on Mars colonization and provides a road map for deciding which other technologies to deploy when planning manned missions to other planets or moons.
“This paper takes a global view of what power technologies are available and how we might deploy them, what are the best-use cases for them and where do they come up short,” said co-first author Anthony Abel, a graduate student in the Department of Chemical and Biomolecular Engineering. “If humanity collectively decides that we want to go to Mars, this kind of systems-level approach is necessary to accomplish it safely and minimize cost in a way that’s ethical. We want to have a clear-eyed comparison between options, whether we’re deciding which technologies to use, which locations to go to on Mars, how to go and whom to bring.”
In the past, NASA’s estimates of the power needs of astronauts on Mars have generally focused on short stays, which don’t require power-hungry processes for growing food, manufacturing construction materials or producing chemicals. But as NASA and leaders of companies now building rockets that could go to Mars — including Elon Musk, CEO of SpaceX, and Jeff Bezos, founder of Blue Origin — talk up the idea of long-term, off-planet settlements, larger and more reliable sources of power need to be considered.
The complication is that all of these materials must be carried from Earth to Mars at a cost of hundreds of thousands of dollars per pound, making low weight essential. One key need is power for biomanufacturing facilities that use genetically engineered microbes to produce food, rocket fuel, plastic materials and chemicals, including drugs. Abel, Berliner and their co-authors are members of the Center for the Utilization of Biological Engineering in Space (CUBES), a multi-university effort to tweak microbes using the gene-insertion techniques of synthetic biology to supply necessary supplies for a colony.
The two researchers discovered, however, that without knowing how much power will be available for an extended mission, it was impossible to assess the practicality of many biomanufacturing processes. So, they set out to create a computerized model of various power supply scenarios and likely power demands, such as habitat maintenance — which includes temperature and pressure control — fertilizer production for agriculture, methane production for rocket propellant to return to Earth, and bioplastics production for manufacturing spare parts.
Pitted against a Kilopower nuclear system were photovoltaics with three power storage options: batteries and two different techniques for producing hydrogen gas from solar energy — by electolysis and directly by photoelectrochemical cells. In the latter cases, the hydrogen is pressurized and stored for later use in a fuel cell to produce power when the solar panels are not. Only photovoltaic power with electrolysis — using electricity to split water into hydrogen and oxygen — was competitive with nuclear power: It proved more cost-effective per kilogram than nuclear over nearly half the planet’s surface.
The main criterion was weight. The researchers assumed that a rocket ferrying a crew to Mars could carry a payload of about 100 tons, exclusive of fuel, and calculated how much of that payload would need to be devoted to a power system for use on the planet’s surface. A journey to and from Mars would take about 420 days — 210 days each way. Surprisingly, they found that the weight of a power system would be less than 10% of the entire payload.
For a landing site near the equator, for example, they estimated that the weight of solar panels plus hydrogen storage would be about 8.3 tons, versus 9.5 tons for a Kilopower nuclear reactor system. Their model also specifies how to tweak photovoltaic panels to maximize efficiency for the different conditions at sites on Mars. Latitude affects the intensity of sunlight, for example, while dust and ice in the atmosphere can scatter longer wavelengths of light.
Abel said that photovoltaics are now highly efficient at converting sunlight into electricity, though the best performers are still expensive. The most crucial new innovation, however, is a lightweight and flexible solar panel, which makes storage on the outbound rocket easier and the cost of transport less.
“The silicon panels that you have on your roof, with steel construction, glass backing, et cetera, just won’t compete with the new and improved nuclear, but newer lightweight, flexible panels all of a sudden really, really change that conversation,” Abel said.
He noted, too, that lighter weight means more panels can be transported to Mars, providing backup for any panels that fail. While kilowatt nuclear power plants provide more power, fewer are needed, so if one goes down, the colony would lose a significant proportion of its power.
Berliner, who is also pursuing a degree in nuclear engineering, came into the project with a bias toward nuclear power, while Abel, whose undergraduate thesis was about new innovations in photovoltaics, was more in favor of solar power.
“I feel like this paper really stems from a healthy scientific and engineering disagreement on the merits of nuclear versus solar power, and that really the work is just us trying to figure out and settle a bet,” Berliner said. “which I think I lost, based on the configurations we chose in order to publish this. But it’s a happy loss, for sure.”
Degradation of low-density polyethylene to nanoplastic particles by accelerated weathering
by Teresa Menzel, Nora Meides, Anika Mauel, Ulrich Mansfeld, Winfried Kretschmer, Meike Kuhn, Eva M. Herzig, Volker Altstädt, Peter Strohriegl, Jürgen Senker, Holger Ruckdäschel in Science of The Total Environment
Polyethylene, a plastic that is both cheap and easy to process, accounts for nearly one-third of the world’s plastic waste. An interdisciplinary team from the University of Bayreuth has investigated the progressive degradation of polyethylene in the environment for the first time. Although the degradation process leads to fragmentation into ever smaller particles, isolated nanoplastic particles are rarely found in the environment. The reason is that such decay products do not like to remain on their own, but rather attach rapidly to larger colloidal systems that occur naturally in the environment.
Polyethylene is a plastic that occurs in various molecular structures. Low-density polyethylene (LDPE) is widely used for packaging everyday consumer goods, such as food, and is one of the most common polymers worldwide as a result of increasing demand. Until now, there have only been estimates as to how this widely used plastic degrades after it enters the environment as waste. A research team from the Collaborative Research Centre “Microplastics” at the University of Bayreuth has now systematically investigated this question for the first time. The scientists developed a novel, technically sophisticated experimental set-up for this purpose. This makes it possible to simulate two well-known and environmentally linked processes of plastic degradation independently in the laboratory: 1.) photo-oxidation, in which the long polyethylene chains gradually break down into smaller, more water-soluble molecules when exposed to light, and 2.) increasing fragmentation due to mechanical stress. On this basis, it was possible to gain detailed insights into the complex physical and chemical processes of LDPE degradation.
The final stage of LDPE degradation is of particular interest for studies addressing the potential impact of polyethylene on the environment. What the researchers discovered was that this degradation does not end with the decomposition of the packaging material released into the environment into many micro- and nanoplastic particles, which have a high degree of crystallinity. The reason is that these tiny particles have a strong tendency to aggregate: they attach rapidly to larger colloidal systems consisting of organic or inorganic molecules and are part of the material cycle in the environment. Examples of such colloidal systems include clay minerals, humic acids, polysaccharides, and biological particles from bacteria and fungi.
“This process of aggregation prevents individual nanoparticles created by polyethylene degradation from being freely available in the environment and interacting with animals and plants. However, this is not an ‘all clear’ signal. Larger aggregates that participate in the material cycle in the environment and contain nanoplastics do often get ingested by living organisms. That is how nanoplastics can eventually enter the food chain,” says Teresa Menzel, one of the three lead authors of the new study and a doctoral researcher in the field of polymer materials.
To identify the degradation products formed when polyethylene decomposes, the researchers employed a method that has not been widely used in microplastics research: multi-cross-polarization in solid-state NMR spectroscopy. “This method even allows us to quantify the degradation products yielded by photooxidation,” says co-author Anika Mauel, a doctoral researcher in inorganic chemistry.
Bayreuth’s researchers have also discovered that the degradation and decomposition of polyethylene also leads to the formation of peroxides. “Peroxides have long been suspected of being cytotoxic, meaning they have a toxic effect on living cells. That is another way in which LDPE degradation poses a potential threat to natural ecosystems. These interrelationships need to be studied in more detail in the future,” adds co-author Nora Meides, a doctoral researcher in macromolecular chemistry.
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