Energy & green technology biweekly vol.42, 20th January — 7th February
TL;DR
- The bacterium Rhodococcus ruber eats and actually digests plastic.
- Scientists have succeeded in synthesizing fumaric acid, a raw material for plastics, from CO2 powered by solar energy. Typically, fumaric acid is synthesized from petroleum as a raw material to make polybutylene succinate, a biodegradable plastic, but this research shows that it can be synthesized from CO2 and biomass-derived compounds using renewable energy.
- A laboratory in photonics and renewable energy has developed a new method for measuring the solar energy produced by bifacial solar panels, the double-sided solar technology which is expected to meet increased global energy demands moving forward.
- The material class of halide perovskites is seen as a great hope for even more solar power at even lower costs. The materials are very cheap, can be processed into thin films with minimal energy input and achieve already efficiencies that are significantly higher than those of conventional silicon solar cells.
- Scientists carve a path to profit from carbon capture by creating a system that efficiently captures CO2 and converts it into one of the world’s most widely used chemicals: methanol.
- Research team has demonstrated that wind turbines in forests impair endangered bat species: Common noctules (Nyctalus noctula), a species with a high risk of colliding with rotor blades, are attracted to forest wind turbines if these are located near their roosts. Far from roosts, common noctules avoid the turbines, essentially resulting in a loss of foraging space and thus habitat for this species.
- With rising concerns about energy and water management, microbial electrochemical technologies (METs), such as microbial fuel cells, have emerged as promising solutions. However, actual progress in these technologies have not lived up to the expectations so far. Now, in a new study, researchers have highlighted strategies that can help with the up-scaling of METs, eventually leading to their commercialization and widespread use.
- Scientists have taken the first step at estimating the best large-scale uses for food processing waste, first analyzing its contents and, based on those findings, proposing production opportunities ranging from sustainable fuels, biogas and electricity to useful chemicals and organic fertilizer.
- Nanotechnology researchers have made novel carbon nanotube yarns that convert mechanical movement into electricity more effectively than other material-based energy harvesters.
- A new hybrid catalyst converts carbon dioxide into ethylene in one pot.
- 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
A stable isotope assay with 13C-labeled polyethylene to investigate plastic mineralization mediated by Rhodococcus ruber
by Maaike Goudriaan, Victor Hernando Morales,et al in Marine Pollution Bulletin
The bacterium Rhodococcus ruber eats and actually digests plastic. This has been shown in laboratory experiments by PhD student Maaike Goudriaan at Royal Netherlands Institute for Sea Research (NIOZ). Based on a model study with plastic in artificial seawater in the lab, Goudriaan calculated that bacteria can break down about one percent of the fed plastic per year into CO2 and other harmless substances.
“But,” Goudriaan emphasizes, “this is certainly not a solution to the problem of the plastic soup in our oceans. It is, however, another part of the answer to the question of where all the ‘missing plastic’ in the oceans has gone.”
Goudriaan had a special plastic manufactured especially for these experiments with a distinct form of carbon (13C) in it. When she fed that plastic to bacteria after pretreatment with “sunlight” — a UV lamp — in a bottle of simulated seawater, she saw that special version of carbon appear as CO2 above the water. “The treatment with UV light was necessary because we already know that sunlight partially breaks down plastic into bite-sized chunks for bacteria,” the researcher explains.
“This is the first time we have proven in this way that bacteria actually digest plastic into CO2 and other molecules,” Goudriaan states. It was already known that the bacterium Rhodococcus ruber can form a so-called biofilm on plastic in nature. It had also been measured that plastic disappears under that biofilm. “But now we have really demonstrated that the bacteria actually digest the plastic.”
When Goudriaan calculates the total breakdown of plastic into CO2, she estimates that the bacteria can break down about one percent of the available plastic per year. “That’s probably an underestimate,” she adds. “We only measured the amount of carbon-13 in CO2, so not in the other breakdown products of the plastic. There will certainly be 13C in several other molecules, but it’s hard to say what part of that was broken down by the UV light and what part was digested by the bacteria.”
Even though marine microbiologist Goudriaan is very excited about the plastic-eating bacteria, she stresses that microbial digestion is not a solution to the huge problem of all the plastic floating on and in our oceans.
“These experiments are mainly a proof of principle. I see it as one piece of the jigsaw, in the issue of where all the plastic that disappears into the oceans stays. If you try to trace all our waste, a lot of plastic is lost. Digestion by bacteria could possibly provide part of the explanation.”
To discover whether ‘wild’ bacteria also eat plastic ‘in the wild’, follow-up research needs to be done. Goudriaan already did some pilot experiments with real sea water and some sediment that she had collected from the Wadden Sea floor.
“The first results of these experiments hints at plastic being degraded, even in nature,” she says. “A new PhD student will have to continue that work. Ultimately, of course, you hope to calculate how much plastic in the oceans really is degraded by bacteria. But much better than cleaning up, is prevention. And only we humans can do that,” Goudriaan says.
Visible-light-driven production of fumarate from CO2 and pyruvate using a photocatalytic system with dual biocatalysts
by Mika Takeuchi, Yutaka Amao in Sustainable Energy & Fuels
In recent years, environmental problems caused by global warming have become more apparent due to greenhouse gases such as CO2. In natural photosynthesis, CO2 is not reduced directly, but is bound to organic compounds which are converted to glucose or starch. Mimicking this, artificial photosynthesis could reduce CO2 by combining it into organic compounds to be used as raw materials, which can be converted into durable forms such as plastic.
A research team led by Professor Yutaka Amao from the Research Center for Artificial Photosynthesis and graduate student Mika Takeuchi, from the Osaka Metropolitan University Graduate School of Science, have succeeded in synthesizing fumaric acid from CO2, a raw material for plastics, powered — for the first time — by sunlight.
Fumaric acid is typically synthesized from petroleum, to be used as a raw material for making biodegradable plastics such as polybutylene succinate, but this discovery shows that fumaric acid can be synthesized from CO2 and biomass-derived compounds using renewable solar energy.
“Toward the practical application of artificial photosynthesis, this research has succeeded in using visible light — renewable energy — as the power source,” explained Professor Amao. “In the future, we aim to collect gaseous CO2 and use it to synthesize fumaric acid directly through artificial photosynthesis.”
A general illumination method to predict bifacial photovoltaic system performance
by Erin M. Tonita, Christopher E. Valdivia, Annie C.J. Russell, Michael Martinez-Szewczyk, Mariana I. Bertoni, Karin Hinzer in Joule
A leading laboratory in photonics and renewable energy at the University of Ottawa has developed a new method for measuring the solar energy produced by bifacial solar panels, the double-sided solar technology which is expected to meet increased global energy demands moving forward.
This study from the SUNLAB team in the Faculties of Engineering and Science proposes a characterization method that will improve the measurement of bifacial panels indoors by considering external effects of ground cover such as snow, grass and soil. This will provide a way to consistently test bifacial solar panel performance indoors that accurately represents how the panels will perform outdoors.
With bifacial photovoltaics expected to provide over 16% of global energy demand by 2050, the SUNLAB’s methodology will improve international device measurement standards which currently do not distinguish between ground cover.
“Our proposed characterization method, the scaled rear irradiance method, is an improved method for indoor-measuring and modelling of bifacial devices that is representative of outdoor environmental conditions,” explains Erin Tonita, lead author and a Physics PhD student studying under Professor Karin Hinzer, whose research group develops new ways to harness the sun’s energy.
“Incorporating this new method into future bifacial standards would provide a consistent methodology for testing bifacial panel performance under ground conditions including snow, grass, and soil, corresponding to globally varying illumination conditions.”
Photovoltaics is the study of converting solar energy into electricity through semiconducting materials, such as silicon. In bifacial solar panels, the semiconducting material is wedged between two sheets of glass to allow for sunlight collection on both sides, with one side typically angled towards the sun and the other side angled towards the ground. The additional light collected by bifacial solar panels on the rear-side offers an advantage over traditional solar panels, with manufacturers touting up to a 30% increase in production compared to traditional solar panels. Bifacial solar panels are also more durable than traditional panels and can produce power for over 30 years.
“Implementation of this method into international standards for such panels can enable predictions of outdoor bifacial panel performance to within 2% absolute,” says Tonita, who expects the benefits of this methodology to include:
- Allowing comparisons between existing and emerging bifacial technologies.
- Enhancing performance via ground cover specific design optimization.
- Increasing solar panel deployments in non-traditional markets.
- Reducing investment risk in bifacial panel deployments.
- Improving bifacial panel manufacture datasheets.
“This method is of particular importance as renewable energy penetration increases towards a net-zero world, with bifacial photovoltaics projected to contribute over 16% of the global energy supply by 2050, or around 30,000 TWh annually,” says Hinzer, founder of SUNLAB and the University Research Chair in Photonic Devices for Energy and a Professor at the School of Electrical Engineering and Computer Science.
“This will extend current International Electrochemical Commission standards for bifacial solar panel measurements, enabling accurate comparisons of bifacial panel technologies, application-specific optimization, and the standardization of bifacial panel power ratings,” adds Hinzer, whose SUNLAB researchers worked in collaboration with Arizona State University for the study.
Highly efficient p-i-n perovskite solar cells that endure temperature variations
by Guixiang Li, Zhenhuang Su, Laura Canil, Declan Hughes, et al in Science
The material class of halide perovskites is seen as a great hope for even more solar power at even lower costs. The materials are very cheap, can be processed into thin films with minimal energy input and achieve already efficiencies that are significantly higher than those of conventional silicon solar cells.
However, solar modules are expected to provide stable output for at least 20 years in outdoor conditions while exposed to large temperature fluctuations. Silicon PV manages this easily, whereas the semi-organic perovskites lose performance rather fast. “Sunlight can heat up the inside of a PV cell to 80 Celsius; in the dark, the cell then cools down immediately to the outside temperature. This triggers large mechanical stresses in the thin layer of perovskite microcrystals, creating defects and even local phase transitions, so that the thin film loses its quality,” explains Prof. Antonio Abate, who heads a large group at HZB.
Together with his team and a number of international partners, he has investigated a chemical variation that significantly improves the stability of the perovskite thin film in different solar cell architectures, among them the p-i-n architecture, which normally is a little less efficient than the more often used n-i-p architecture.
“We optimized the device structure and process parameters, building upon previous results, and finally could achieve a decisive improvement with b-poly(1,1-difluoroethylene) or b-pV2F for short,” says Guixiang Li, who is doing his PhD supervised by Prof. Abate. b-pV2F molecules resemble a zigzag chain occupied by alternating dipoles. “This polymer seems to wrap around the individual perovskite microcrystals in the thin film like a soft shell, creating a kind of cushion against thermomechanical stress,” Abate explains.
In fact, scanning electron microscope images show that in the cells with b-pV2F, the tiny granules nestle a little closer. “In addition, the dipole chain of b-pV2F improves the transport of charge carriers and thus increases the efficiency of the cell,” says Abate. Indeed they produced cells on a laboratory scale with efficiencies of up to 24.6%, which is a record for the p-i-n architecture.
The newly produced solar cells were subjected over a hundred cycles between +80 Celsius and -60 Celsius and 1000 hours of continuous 1-sun equivalent illumination. That corresponds to about one year of outdoor use. “Even under these extreme stresses, they still achieved 96 % efficiency in the end,” Abate emphasises. That is already in the right order of magnitude. If it is now feasible to reduce the losses a little further, perovskite solar modules could still produce most of their original output after 20 years — this goal is now coming within reach.
Energy-effective and low-cost carbon capture from point-sources enabled by water-lean solvents
by Yuan Jiang, Paul M. Mathias, Richard F. Zheng, Charlies J. Freeman, Dushyant Barpaga, Deepika Malhotra, Phillip K. Koech, Andy Zwoster, David J. Heldebrant in Journal of Cleaner Production
The need for technology that can capture, remove and repurpose carbon dioxide grows stronger with every CO2 molecule that reaches Earth’s atmosphere. To meet that need, scientists at the Department of Energy’s Pacific Northwest National Laboratory have cleared a new milestone in their efforts to make carbon capture more affordable and widespread. They have created a new system that efficiently captures CO2 — the least costly to date — and converts it into one of the world’s most widely used chemicals: methanol.
Snaring CO2 before it floats into the atmosphere is a key component in slowing global warming. Creating incentives for the largest emitters to adopt carbon capture technology, however, is an important precursor. The high cost of commercial capture technology is a longstanding barrier to its widespread use.
PNNL scientists believe methanol can provide that incentive. It holds many uses as a fuel, solvent, and an important ingredient in plastics, paint, construction materials and car parts. Converting CO2 into useful substances like methanol offers a path for industrial entities to capture and repurpose their carbon.
PNNL chemist David Heldebrant, who leads the research team behind the new technology, compares the system to recycling. Just as one can choose between single-use and recyclable materials, so too can one recycle carbon.
“That’s essentially what we’re trying to do here,” said Heldebrant. “Instead of extracting oil from the ground to make these chemicals, we’re trying to do it from CO2 captured from the atmosphere or from coal plants, so it can be reconstituted into useful things. You’re keeping carbon alive, so to speak, so it’s not just ‘pull it out of the ground, use it once, and throw it away.’ We’re trying to recycle the CO2, much like we try to recycle other things like glass, aluminum and plastics.”
As described, the new system is designed to fit into coal-, gas-, or biomass-fired power plants, as well as cement kilns and steel plants. Using a PNNL-developed capture solvent, the system snatches CO2 molecules before they’re emitted, then converts them into useful, sellable substances. A long line of dominoes must fall before carbon can be completely removed or entirely prevented from entering Earth’s atmosphere. This effort — getting capture and conversion technology out into the world — represents some of the first few crucial tiles.
Deploying this technology will reduce emissions, said Heldebrant. But it could also help stir the development of other carbon capture technology and establish a market for CO2-containing materials. With such a market in place, carbon seized by anticipated direct air capture technologies could be better reconstituted into longer-lived materials.
In April 2022, the Intergovernmental Panel on Climate Change issued its Working Group III report focused on mitigating climate change. Among the emissions-limiting measures outlined, carbon capture and storage was named as a necessary element in achieving net zero emissions, especially in sectors that are difficult to decarbonize, like steel and chemical production.
“Reducing emissions in industry will involve using materials more efficiently, reusing and recycling products and minimizing waste,” the IPCC stated in a news release issued alongside one of the report’s 2022 installments. “In order to reach net zero CO2 emissions for the carbon needed in society (e.g., plastics, wood, aviation fuels, solvents, etc.),” the report reads, “it is important to close the use loops for carbon and carbon dioxide through increased circularity with mechanical and chemical recycling.”
PNNL’s research is focused on doing just that — in alignment with DOE’s Carbon Negative Shot. By using renewably sourced hydrogen in the conversion, the team can produce methanol with a lower carbon footprint than conventional methods that use natural gas as a feedstock. Methanol produced via CO2 conversion could qualify for policy and market incentives intended to drive adoption of carbon reduction technologies. Methanol is among the most highly produced chemicals in existence by volume. Known as a “platform material,” its uses are wide ranging. In addition to methanol, the team can convert CO2 into formate (another commodity chemical), methane and other substances.
A significant amount of work remains to optimize and scale this process, and it may be several years before it is ready for commercial deployment. But, said Casie Davidson, manager for PNNL’s Carbon Management and Fossil Energy market sector, displacing conventional chemical commodities is only the beginning. “The team’s integrated approach opens up a world of new CO2 conversion chemistry. There’s a sense that we’re standing on the threshold of an entirely new field of scalable, cost-effective carbon tech. It’s a very exciting time.”
Commercial systems soak up carbon from flue gas at roughly $46 per metric ton of CO2, according to a DOE analysis. The PNNL team’s goal is to continually chip away at costs by making the capture process more efficient and economically competitive. The team brought the cost of capture down to $47.10 per metric ton of CO2 in 2021. A new study explores the cost of running the methanol system using different PNNL-developed capture solvents, and that figure has now dropped to just below $39 per metric ton of CO2.
“We looked at three CO2-binding solvents in this new study,” said chemical engineer Yuan Jiang, who led the assessment. “We found that they capture over 90 percent of the carbon that passes through them, and they do so for roughly 75 percent of the cost of traditional capture technology.”
Different systems can be used depending on the nature of the plant or kiln. But, no matter the setup, solvents are central. In these systems, solvents wash over CO2-rich flue gas before it’s emitted, leaving behind CO2 molecules now bound within that liquid. Creating methanol from CO2 is not new. But the ability to both capture carbon and then convert it into methanol in one continuously flowing system is. Capture and conversion has traditionally occurred as two distinct steps, separated by each process’s unique, often non-complementary chemistry.
“We’re finally making sure that one technology can do both steps and do them well,” said Heldebrant, adding that traditional conversion technology typically requires highly purified CO2. The new system is the first to create methanol from “dirty” CO2.
The process of capturing CO2 and converting it to methanol is not CO2-negative. The carbon in methanol is released when burned or sequestered when methanol is converted to substances with longer lifespans. But this technology does “set the stage,” Heldebrant said, for the important work of keeping carbon bound inside material and out of the atmosphere.
Other target materials include polyurethanes, which are found in adhesives, coatings, and foam insulation, and polyesters, which are widely used in fabrics for textiles. Once researchers finalize the chemistry behind converting CO2 into materials that keep it out of the atmosphere for climate-relevant timescales, a wide web of capture systems could be poised to run such reactions.
Wind energy production in forests conflicts with tree-roosting bats
by Christine Reusch, Ana Ailin Paul, Marcus Fritze, Stephanie Kramer-Schadt, Christian C. Voigt in Current Biology
In order to meet climate protection goals, renewable energies are booming — often wind power. More than 30,000 turbines have already been installed on the German mainland so far, and the industry is currently scrambling to locate increasingly rare suitable sites. Thus, forests are coming into focus as potential sites. A scientific team from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) now demonstrated in a new paper published in the scientific journal “Current Biology” that wind turbines in forests impair endangered bat species: Common noctules (Nyctalus noctula), a species with a high risk of colliding with rotor blades, are attracted to forest wind turbines if these are located near their roosts. Far from roosts, common noctules avoid the turbines, essentially resulting in a loss of foraging space and thus habitat for this species.
The research results show that common noctules suffer in two ways from wind turbines in forests: If the wind turbines are built near roosts, noctules face an increasing risk of colliding with the turbines, and they lose foraging habitat because they avoid wind turbines far from roosts. In their paper the team concludes that wind power development in forests must be avoided or, if there is no alternative, should be undertaken with great care and caution. The wind turbine should be placed at least at a distance of 500 meters away from bat roosting sites, and loss of foraging habitat should be compensated for by taking forests out of use for wind power (or other anthropogenic activities) elsewhere.
Wind energy production is an important pillar for the energy transition to renewable energies in Germany and makes a significant contribution to reducing greenhouse gas emissions. Approximately eight percent of wind turbines in Germany have already been built in forests. This number is expected to significantly increase in the coming years as suitable sites in open landscapes become increasingly scarce.
“A large number of bat species occur in forests because there are many tree roosts and suitable foraging habitats with a high abundance of insects, their prey,” says Christian Voigt, head of the Department of Evolutionary Ecology at the Leibniz-IZW. “These include species such as the common noctule, which is the most common victim among the bat species of wind turbines in Germany. According to the German Federal Agency for Nature Conservation (BfN), common noctule populations are declining throughout Germany. It is therefore a matter of urgency to take a closer look at the interaction of bats with wind turbines in forests.”
Voigt and his colleagues investigated the space-use behaviour of common noctules using miniaturised GPS loggers. These loggers recorded the flight paths of 60 bats with a high temporal and spatial resolution over 1–2 nights before the loggers automatically came off each animal. “We found that the common noctules were particularly likely to approach wind turbines if the latter were located close to bat roosts,” explains Voigt. As highly social mammals, the bats use exposed structures as meeting spots. This could be the reason why they often approach wind turbines, which rise well above the canopy, if turbines are located near roosts. This poses a high risk to the animals of colliding with the rotor blades.
“Wind turbines would therefore have to be erected at a sufficient distance from existing tree roosts,” concludes Christine Reusch, first author of the paper. “As roosts can also be newly created, there is a risk that supposedly safe wind turbines, which were initially erected at a sufficiently large distance from the then existing bat roosts during the approval phase, later become death traps,” Reusch adds.
The authors also found that further away from tree roosts, common noctules avoided wind turbines. They discovered this after they had carried out a data analysis in which all bat GPS locations in the vicinity of roosts were excluded from the analysis. This showed that bats avoid wind turbines if placed well beyond roosts. “This sounds like good news but it has a problematic side to it,” says Voigt. “Owing to their avoidance behaviour, common noctule bats essentially lose important hunting habitats.” The scientists therefore recommend, firstly, that wind turbines should not be sited in forests, and secondly, that special care should be taken if there are no alternatives. A minimum distance of 500 meters of wind turbines to known bat roosts should be taken into account during the approval procedures and the loss of foraging habitat in the vicinity of wind turbines should be compensated for elsewhere. The expansion of wind energy production into forests is therefore a major challenge to conservation in view of the complex interaction of bats with wind turbines in forests, according to Voigt and Reusch.
Scale-up of the bioelectrochemical system: Strategic perspectives and normalization of performance indices
by Dipak A. Jadhav, Ashvini D. Chendake, Vandana Vinayak, Abdulaziz Atabani, Mohammad Ali Abdelkareem, Kyu-Jung Chae in Bioresource Technology
With rising concerns about energy and water management, microbial electrochemical technologies (METs), such as microbial fuel cells, have emerged as promising solutions. However, actual progress in these technologies have not lived up to the expectations so far. Now, in a new study, researchers from Korea, India, UAE, and Turkey have highlighted strategies that can help with the up-scaling of METs, eventually leading to their commercialization and widespread use.
Microbial electrochemical technologies (METs) have recently emerged as a tool for recovering bioenergy and bio-resource from organic waste matter. This can help with long-term energy generation during wastewater treatment. METs, commonly expressed as bioelectrochemical systems (BES), offer maximum resource and energy recovery with minimum energy investment. However, there is currently a mismatch between expectations and actual progress in BES technologies due to a lack of reproducible and statistical data, which hinders their scalability and, in turn, commercialization. Set against this backdrop, an international team of researchers, led by Dr. Dipak Jadhav and Prof. Kyu-Jung Chae from Korea Maritime and Ocean University (KMOU) addressing this issue.
“For industrial applications, the scaling up of bioelectrochemical system is an important concern before moving ahead with their commercialization. Our study provides strategies that can be adopted to achieve this end,” explains Dr. Jadhav. “Such a technology will be a value addition for the recovery of resources including biohydrogen, electricity, industrial chemicals.” On this front, a review of recent research revealed the need for a systematic rethinking of net energy recovery, resource yield, and current production, with a focus on sustainability and energy marketability, for the scaling-up of METs.
The most important need identified was the standardization of performance indices, which helps assess the performance of various BES. Additionally, the team proposed a single frame for normalization methods to allow for precise data comparison to existing treatments. These technological implementations, the study suggests, will effectively address the existing concerns with BES. This, in turn, would help attract the business market, stakeholders, and investors, paving the way for their commercialization.
“We expect that, based on our highlighted strategies for up-scaling BES technologies, we can harness their potential for resource recovery by converting the chemical energy of wastewater into valuable resources during on-site treatment at an efficiency that is comparable with conventional methods,” concludes an optimistic Prof. Kyu-Jung Chae.
Characterization and potential valorization of industrial food processing wastes
by Beenish Saba, Ashok K. Bharathidasan, Thaddeus C. Ezeji, Katrina Cornish in Science of The Total Environment
There is money to be made — and potential to reduce greenhouse gas emissions — by finding a second life for the potato peels, fried dough particles, cheese whey and other industrial food-processing waste products that routinely end up in landfills, according to new research.
Scientists have taken the first step at estimating the best large-scale uses for food processing waste, first analyzing its contents and, based on those findings, proposing production opportunities ranging from sustainable fuels, biogas and electricity to useful chemicals and organic fertilizer. This work is known as valorization, or determining the potential value of something “that is otherwise valueless or even a drain on resources for a company — when you have to spend money to get rid of it,” said Katrina Cornish, senior author of the study and professor of horticulture and crop science and food, agricultural and biological engineering at The Ohio State University.
“The bioeconomy is becoming much more prevalent as a topic of conversation. In this case, don’t get rid of food waste — make some money from it,” said Cornish, also an Ohio Research Scholar of Bio-Emergent Materials. “Here, we’re putting the base model in place for food manufacturers who are wondering, ‘What can I do with this stuff?’ Our flow chart guides them in a specific direction and prevents them from wasting time trying something we know won’t work.”
About 2% of the 80 billion pounds of food discarded annually in the United States is attributable to food manufacturing and processing — with food waste solids sent to landfills or composted, and liquids poured into sewers. For the study, researchers collected a total of 46 waste samples, including 14 from large Ohio food processing companies, and divided them into four broad categories: vegetable, fat-rich, industrial sludge and starchy. They then characterized the sample contents’ physical and chemical properties and tested some starchy wastes they determined were good candidates for fermentation into the platform chemical acetone.
In the big picture, a waste type’s energy density — based on calorific value — and carbon-to-nitrogen ratio were major determinants for its repurposing potential. For example, fatty waste and mineral-based waste can be digested anaerobically to generate biogas, and soybean waste has enough energy density to be used for biodiesel production. Low-calorific vegetable wastes aren’t great for energy production, but they are plentiful organic sources of flavonoids, antioxidants and pigments that could be extracted and used in health-promoting compounds.
Based on the analysis of fibrous and mineral-rich wastes, Cornish has practiced what she’s preaching: Her lab developed a method for turning eggshells and tomato peels sourced from Ohio food producers into fillers in rubber products, partially replacing petroleum-based carbon black in tires, for example.
“We aligned this work with the Environmental Protection Agency goal to reduce 50% of food loss and waste by 2030,” said first author Beenish Saba, a postdoctoral researcher in food, agricultural and biological engineering at Ohio State. “So, how can you reduce this waste? Valorization is one method.
“In Ohio, corn is being grown to convert into biofuel, acetone and butanol, and here we’ve identified other sources already available as wastes that you can also convert into those products.”
The proposed conversion technologies require energy to operate and also yield some secondary waste, but the valorization modeling lays groundwork for further “cradle to grave” analyses that would help quantify the environmental benefits of large-scale food — and other industry — waste reduction, Saba said.
While this study is a starting point, it ideally will offer incentive for food producers to consider the possibilities of making something out of waste products that are currently treated as trash, the researchers say.
“What we hope will happen is that food producers will actually look at their costs and their footprint, and see which of these approaches for their particular wastes will work best — which will be the least financially negative, and preferably profitable, and also minimize any carbon footprint,” Cornish said. “In terms of global warming, any waste that can be valorized has a direct impact on global warming because it has a direct impact on emissions and on the ecosystem.
“This is all about improving energy security and lowering the financial and environmental impacts of food waste management,” she said. “If your waste has enough value for you to do something with it that prevents it from going into the landfill, that’s a really good thing.”
Mechanical energy harvesters with tensile efficiency of 17.4% and torsional efficiency of 22.4% based on homochirally plied carbon nanotube yarns
by Mengmeng Zhang, Wenting Cai, Zhong Wang, Shaoli Fang, Runyu Zhang, et al in Nature Energy
Nanotechnology researchers at The University of Texas at Dallas have made novel carbon nanotube yarns that convert mechanical movement into electricity more effectively than other material-based energy harvesters.
In a study, UT Dallas researchers and their collaborators describe improvements to high-tech yarns they invented called “twistrons,” which generate electricity when stretched or twisted. Their new version is constructed much like traditional wool or cotton yarns. Twistrons sewn into textiles can sense and harvest human motion; when deployed in salt water, twistrons can harvest energy from the movement of ocean waves; and twistrons can even charge supercapacitors.
First described by UTD researchers in a study published in 2017 in the journal Science, twistrons are constructed from carbon nanotubes (CNTs), which are hollow cylinders of carbon 10,000 times smaller in diameter than a human hair. To make twistrons, the nanotubes are twist-spun into high-strength, lightweight fibers, or yarns, into which electrolytes can also be incorporated. Previous versions of twistrons were highly elastic, which the researchers accomplished by introducing so much twist that the yarns coil like an overtwisted rubber band. Electricity is generated by the coiled yarns by repeatedly stretching and releasing them, or by twisting and untwisting them.
In the new study, the research team did not twist the fibers to the point of coiling. Instead, they intertwined three individual strands of spun carbon nanotube fibers to make a single yarn, similar to the way conventional yarns used in textiles are constructed — but with a different twist.
“Plied yarns used in textiles typically are made with individual strands that are twisted in one direction and then are plied together in the opposite direction to make the final yarn. This heterochiral construction provides stability against untwisting,” said Dr. Ray Baughman, director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas and the corresponding author of the study.
“In contrast, our highest-performance carbon-nanotube-plied twistrons have the same-handedness of twist and plying — they are homochiral rather than heterochiral,” said Baughman, the Robert A. Welch Distinguished Chair in Chemistry in the School of Natural Sciences and Mathematics.
In experiments with the plied CNT yarns, the researchers demonstrated an energy conversion efficiency of 17.4% for tensile (stretching) energy harvesting and 22.4% for torsional (twisting) energy harvesting. Previous versions of their coiled twistrons reached a peak energy conversion efficiency of 7.6% for both tensile and torsional energy harvesting.
“These twistrons have a higher power output per harvester weight over a wide frequency range — between 2 Hz and 120 Hz — than previously reported for any non-twistron, material-based mechanical energy harvester,” Baughman said.
Baughman said the improved performance of the plied twistrons results from the lateral compression of the yarn upon stretching or twisting. This process brings the plies in contact with one another in a way that affects the electrical properties of the yarn.
“Our materials do something very unusual,” Baughman said. “When you stretch them, instead of becoming less dense, they become more dense. This densification pushes the carbon nanotubes closer together and contributes to their energy-harvesting ability. We have a large team of theorists and experimentalists trying to understand more completely why we get such good results.”
The researchers found that constructing the yarn from three plies provided the optimal performance. The team conducted several proof-of-concept experiments using three-ply twistrons. In one demonstration they simulated the generation of electricity from ocean waves by attaching a three-ply twistron between a balloon and the bottom of an aquarium filled with salt water. They also arranged multiple plied twistrons in an array weighing only 3.2 milligrams and repeatedly stretched them to charge a supercapacitor, which then had enough energy to power five small light-emitting diodes, a digital watch and a digital humidity/temperature sensor.
The team also sewed the CNT yarns into a cotton fabric patch that was then wrapped around a person’s elbow. Electrical signals were generated as the person repeatedly bent their elbow, demonstrating the potential use of the fibers for sensing and harvesting human motion.
Hybrid Catalyst Coupling Single-Atom Ni and Nanoscale Cu for Efficient CO2 Electroreduction to Ethylene
by Zhouyang Yin, Jiaqi Yu, Zhenhua Xie, Shen-Wei Yu, Liyue Zhang, Tangi Akauola, Jingguang G. Chen, Wenyu Huang, Long Qi, Sen Zhang in Journal of the American Chemical Society
A new hybrid catalyst converts carbon dioxide into ethylene in one pot. The catalyst was developed by scientists from Ames National Laboratory, Iowa State University, University of Virginia, and Columbia University. This catalyst supports the world net-zero carbon initiative by using carbon dioxide (CO2) as a feedstock for efficient ethylene production powered by electricity.
Ethylene is a commodity chemical used to manufacture a wide range of products from plastics to antifreeze. The large-scale production of ethylene is energy intensive and relies heavily on fossil resources. Electrocatalytic production of ethylene from CO2 is emerging as a promising method. This new catalyst consists of only earth-abundant materials, such as nickel and copper, and requires less energy for chemical reaction.
Long Qi, a scientist at Ames Lab, explained how the catalyst works. Atomically dispersed nickel anchored on nitrogen assembly carbon (NAC) works to catalyze CO2 to CO at low voltage and high current. The catalyst is effective over a wide range of voltages and its effectiveness at higher currents means a higher rate of CO production.
“Since this catalyst remains active over a very wide voltage range, that allows easy coupling with a second catalyst,” Qi said. “So we use the second catalyst, which is a copper nanowire, and by combining these two we have a very selective process that has up to 60% efficiency going from CO2 to ethylene in one pot.”
Another important aspect of the catalyst is its structure. Wenyu Huang, an Ames Lab scientist and Iowa State University professor from the team, noted that the catalyst’s porous structure enhances its effectiveness. “Our catalyst has an ordered mesoporous structure that is beneficiary for mass transfer,” he said. “Because it’s highly porous, you have a very high surface area to expose a lot of nickel’s active sites, making our catalyst very effective in CO2 reduction to CO.”
For Huang, the most exciting aspect of this research was how the team combined the two catalysts to streamline the process. “We basically combine the two best catalysts on their own, and they work together so we can connect the CO2 to CO and the CO to ethylene reactions in one system,” he said.
Qi emphasized the importance of using CO2 as a feedstock for this reaction, because it addresses the global need to reduce the amount of CO2 released into the atmosphere. He explained that this process can use CO2 recovered from chemical or industrial processes, or from air capture.
“And we can do this without any precious metal, simply the nickel, copper, carbon, and nitrogen, to permit large-scale industrial applications,” Qi said. “Also, we potentially eliminate the use of fossil resources to make ethylene.”
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