It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, July 05, 2024
Why the U.S. food system needs agroecology
DARTMOUTH COLLEGE
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LEAH PENNIMAN (LEFT), CO-FOUNDER AND FARM DIRECTOR AT SOUL FIRE FARM IN PETERSBURG, NEW YORK, AND MX. T, FARM IMMERSION PROGRAM PARTICIPANT.
CREDIT: PHOTO COURTESY OF SOUL FIRE FARM WHO PARTICIPATED IN THE U.S. AGROECOLOGY SUMMIT 2023.
Agroecology—a science, practice, and movement which seeks social, political, economic, and environmental sustainability in the global food system—is gaining momentum in the U.S., according to a new Dartmouth-led commentary in Nature Food. As the co-authors report, the approach requires coordination between scientists, farmers, and activists.
"When it comes to sustainable food and agriculture, people in the U.S. tend to be more familiar with organic farming, the production of food without synthetic inputs, and regenerative agriculture, which primarily strives to restore soil health," says lead author Theresa Ong, an assistant professor of environmental studies at Dartmouth.
"Agroecology is different, as it strives to achieve both ecological and social sustainability of food systems without sacrificing one for the other. We cannot save biodiversity and ecosystem integrity without also preserving farmer livelihoods and ensuring that the food systems we create provide food that is culturally relevant to local communities, and not simply meeting a calorie quota," says Ong.
Supporters of agroecology say the U.S. food system is dominated by industrial agriculture, which is characterized by monoculture production, reliance on agrochemicals like pesticides and fertilizers, and advanced technology and machinery that depend heavily on fossil fuels.
Prior research has found that challenges facing global food systems—which include food insecurity, public health crises, biodiversity loss, and climate change—are perpetuated in part by the U.S. food system and the political influence of its big players.
For decades, many in the U.S. and beyond have called for transforming the industrial food system. The United Nations has promoted agroecology as the mechanism to achieve that transformation.
Despite its growing international reputation, agroecology was slow to gain recognition beyond academic circles in the U.S.
But staff from the U.S. Department of Agriculture asked agroecologists to convene a U.S. Agroecology Summit in 2023, which brought together 100 stakeholders in the food system to discuss promoting research of this kind in the country.
Participants discussed the need for equitable representation and support for all food system stakeholders including agricultural practitioners, food systems changemakers, and scientists, and increased access to funding and ethical approaches to research.
"'Food sovereignty'—the right to define, produce, and access healthy food that is culturally appropriate and preserves the ways of life of farmers, is a critical goal in agroecology and was first defined by La Vía Campesina, an international peasant movement, in 1996," says Ong, who was a participant at the summit.
The Agroecology Summit builds on momentum that has been growing over the last 15 years, with the establishment of the nonprofit U.S. Food Sovereignty Alliance in 2010 and enactment of food sovereignty laws in eight states (Maine, Vermont, Massachusetts, Georgia, North Carolina, Utah, Wyoming, and Montana). In addition, agroecology institutes were created at Florida A&M University in 2022 and University of Vermont in 2023.
Much work still needs to be done to ensure that all voices are represented and have decision-making power in this space, who may share many of the same values and goals like large and small farmers, family farmers, migrant farmers, Black and Indigenous farmers, and farm workers, according to the co-authors.
"Agroecology is about building coalitions to ensure equitable representation and coordination between farmers, activists, and academics," says Ong.
Antonio Roman-Alcalá at California State University, East Bay; Estelí Jiménez-Soto at University of South Florida; Erin Jackson at Colorado State University; Ivette Perfecto at University of Michigan; and Hannah Duff at Montana State University; also contributed to the commentary.
The James Webb Space Telescope captures a staggering quasar-galaxy merger in the remote universe
An international research group led by the Italian National Institute for Astrophysics (INAF) utilised the the James Webb Space Telescope to witness the dramatic interaction between a quasar and two massive satellite galaxies in the distant universe
ISTITUTO NAZIONALE DI ASTROFISICA
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MAP OF THE LINE EMISSION OF HYDROGEN (IN RED AND BLUE) AND OXYGEN (IN GREEN) IN THE PJ308-21 SYSTEM, SHOWN AFTER MASKING THE LIGHT FROM THE CENTRAL QUASAR ("QSO"). THE DIFFERENT COLOURS OF THE QUASAR'S HOST GALAXY AND COMPANION GALAXIES IN THIS MAP REVEAL THE PHYSICAL PROPERTIES OF THE GAS WITHIN THEM.
Observations of this quasar (already described by the same authors in another study published last May), one of the first studied with NIRSpec when the universe was less than a billion years old (redshift z = 6.2342), have revealed data of sensational quality: the instrument “captured” the quasar’s spectrum with an uncertainty of less than 1% per pixel. The host galaxy of PJ308–21 shows high metallicity and photoionisation conditions typical of an active galactic nucleus (AGN), whereas one of the satellite galaxies exhibits low metallicity (which refers to the abundance of chemical elements heavier than hydrogen and helium) and photoionisation induced by star formation; a higher metallicity characterises the second satellite galaxy, which is partially photoionised by the quasar.
The discovery has enabled astronomers to determine the mass of the supermassive black hole at the centre of the system (about 2 billion solar masses). It also confirmed that both the quasar and the surrounding galaxies are highly evolved in mass and metal enrichment, and in constant growth. This has profound implications for our understanding of cosmic history and galaxies' chemical evolution, highlighting this research's transformative impact.
Roberto Decarli, a researcher at INAF in Bologna and first author of the article, explains: "Our study reveals that both the black holes at the centre of high-redshift quasars and the galaxies that host them undergo extremely efficient and tumultuous growth already in the first billion years of cosmic history, aided by the rich galactic environment in which these sources form". The data were obtained in September 2022 as part of Program 1554, one of the nine Italian-led projects of the first observation cycle of JWST. Decarli leads this program to observe the merger between the galaxy hosting the quasar (PJ308-21) and two of its satellite galaxies.
The observations were carried out in integral field spectroscopy mode: for each image pixel, the spectrum of the entire optical band (in the source rest frame) can be observed, shifted towards the infrared by the universe’s expansion. This allows for the study of various gas tracers (emission lines) using a 3D approach. Thanks to this technique, the team led by INAF detected spatially extended emissions from different elements, which were used to study the properties of the ionised interstellar medium, including the source and hardness of the photoionising radiation field, metallicity, dust obscuration, electron density and temperature, and star formation rate. Furthermore, the researchers marginally detected the starlight emission associated with companion sources.
Federica Loiacono, astrophysicist, research fellow and postdoc working at INAF, enthusiastically comments on the results: "Thanks to NIRSpec, for the first time we can study in the PJ308-21 system the optical band, rich in precious diagnostic data on properties of the gas near the black hole in the galaxy hosting the quasar and in the surrounding galaxies. We can see, for example, the emission of hydrogen atoms and compare it with the chemical elements produced by the stars to establish how rich the gas in galaxies is in metals. The experience in reducing and calibrating these data, some of the first collected with NIRSpec in integral field spectroscopy mode, has ensured a strategic advantage for the Italian community in managing similar data from other programs". Federica Loiacono is the Italian contact person for NIRSpec data reduction at the INAF JWST Support Center.
She adds: “Thanks to the sensitivity of the James Webb Space Telescope in the near and medium infrared, it was possible to study the spectrum of the quasar and companion galaxies with unprecedented precision in the distant universe. Only the excellent 'view' offered by JWST, with its unparalleled capabilities, can ensure these observations". The work represented a real "emotional rollercoaster", Decarli continues, "with the need to develop innovative solutions to overcome the initial difficulties in data reduction".
This transformative impact of the James Webb Space Telescope's onboard instruments underscores its crucial role in advancing astrophysical research: “Until a couple of years ago, data on the enrichment of metals (essential for understanding the chemical evolution of galaxies) were almost beyond our reach, especially at these distances. Now we can map them in detail with just a few hours of observation, even in galaxies observed when the universe was in its infancy", Decarli concludes.
Related journal article: "A quasar-galaxy merger at z ∼ 6.2: rapid host growth via accretion of two massive satellite galaxies”, by Roberto Decarli, Federica Loiacono, Emanuele Paolo Farina, Massimo Dotti, Alessandro Lupi, Romain A. Meyer, Marco Mignoli, Antonio Pensabene, Michael A. Strauss, Bram Venemans, Jinyi Yang, Fabian Walter, Julien Wolf, Eduardo Bañados, Laura Blecha, Sarah Bosman, Chris L. Carilli, Andrea Comastri, Thomas Connor, Tiago Costa, Anna-Christina Eilers, Xiaohui Fan, Roberto Gilli, Hyunsung D. Jun, Weizhe Liu, Madeline A. Marshall, Chiara Mazzucchelli, Marcel Neeleman, Masafusa Onoue, Roderik Overzier, Maria Anne Pudoka, Dominik A. Riechers, Hans-Walter Rix, Jan-Torge Schindler, Benny Trakhtenbrot, Maxime Trebitsch, Marianne Vestergaard, Marta Volonteri, Feige Wang, Huanian Zhang, Siwei Zou. Forthcoming in: Astronomy & Astrophysics.
A quasar-galaxy merger at z~6.2: Rapid host growth via the accretion of two massive satellite galaxies
Fresh wind blows from historical supernova
Elusive temporary star described in historical documents recreated using new computer model, shows it may have recently started generating stellar winds
UNIVERSITY OF TOKYO
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THIS ILLUSTRATION CHARTS THE EVOLUTION OF THE SNR 1181 REMNANT, FROM ITS CREATION WHEN A CARBON-OXYGEN-BASED WHITE DWARF AND OXYGEN-NEON WHITE DWARF MERGED, TO THE FORMATION OF ITS TWO SHOCK REGIONS.
A mysterious remnant from a rare type of supernova recorded in 1181 has been explained for the first time. Two white dwarf stars collided, creating a temporary “guest star,” now labeled supernova (SN) 1181, which was recorded in historical documents in Japan and elsewhere in Asia. However, after the star dimmed, its location and structure remained a mystery until a team pinpointed its location in 2021. Now, through computer modeling and observational analysis, researchers have recreated the structure of the remnant white dwarf, a rare occurrence, explaining its double shock formation. They also discovered that high-speed stellar winds may have started blowing from its surface within just the past 20-30 years. This finding improves our understanding of the diversity of supernova explosions, and highlights the benefits of interdisciplinary research, combining history with modern astronomy to enable new discoveries about our galaxy.
It is the year 1181 and in Japan the Genpei War (1180-85) has recently begun. It will lead to a shift in political power from aristocratic families to the new military-based shogunate, which will establish itself in the coastal city of Kamakura near modern-day Tokyo. A record of this tumultuous period was compiled in a diary format in the Azuma Kagami. It chronicled not only people’s lives and key events (with varying accuracy), but other daily observations, including the appearance of a new star.
“There are many accounts of this temporary guest star in historical records from Japan, China and Korea. At its peak, the star’s brightness was comparable to Saturn’s. It remained visible to the naked eye for about 180 days, until it gradually dimmed out of sight. The remnant of the SN 1181 explosion is now very old, so it is dark and difficult to find,” explained lead author Takatoshi Ko, a doctoral student from the Department of Astronomy at the University of Tokyo.
The remnant of this guest star, labeled supernova remnant (SNR) 1181, was found to have been created when two extremely dense, Earth-sized stars, called white dwarfs, collided. This created a rare type of supernova, called a Type Iax supernova, which left behind a single, bright and fast-rotating white dwarf. Aided by observations on its position noted in the historical document, modern astrophysicists finally pinpointed its location in 2021 in a nebula towards the constellation Cassiopeia.
Due to its rare nature and location within our galaxy, SNR 1181 has been the subject of much observational research. This suggested that SNR 1181 is made up of two shock regions, an outer region and an inner one. In this new study, the research group analyzed the latest X-ray data to construct a theoretical computer model to explain these observations, and which has recreated the previously unexplained structure of this supernova remnant.
The main challenge was that according to conventional understanding, when two white dwarfs collide like this, they should explode and disappear. However, this merger left behind a white dwarf. The spinning white dwarf was expected to create a stellar wind (a fast-flowing stream of particles) immediately after its formation. However, what the researchers found was something else.
“If the wind had started blowing immediately after SNR 1181’s formation, we couldn’t reproduce the observed size of the inner shock region,” said Ko. “However, by treating the wind’s onset time as variable, we succeeded in explaining all of the observed features of SNR 1181 accurately and unraveling the mysterious properties of this high-speed wind. We were also able to simultaneously track the time evolution of each shock region, using numerical calculations.”
The team was very surprised to find that according to their calculations, the wind may have started blowing only very recently, within the past 20-30 years. They suggest this may indicate that the white dwarf has started to burn again, possibly due to some of the matter thrown out by the explosion witnessed in 1181 falling back to its surface, increasing its density and temperature over a threshold to restart burning.
To validate their computer model, the team is now preparing to further observe SNR 1181 using the Very Large Array (VLA) radio telescope based in central New Mexico state in the U.S., and the 8.2 meter-class Subaru Telescope in the U.S. state of Hawaii.
“The ability to determine the age of supernova remnants or the brightness at the time of their explosion through archaeological perspectives is a rare and invaluable asset to modern astronomy,” said Ko. “Such interdisciplinary research is both exciting and highlights the immense potential for combining diverse fields to uncover new dimensions of astronomical phenomena.”
Comparison of X-ray image (left) and new schematic (right)
CAPTION
These images show the two shock regions of the remnant SNR 1181. The bright white at the center is the white dwarf.
CREDIT
2024 T. Ko, H. Suzuki, K. Kashiyama et al./ The Astrophysical Journal
Paper
Takatoshi Ko, Hiromasa Suzuki, Kazumi Kashiyama, Hiroyuki Uchida, Takaaki Tanaka, Daichi Tsuna, Kotaro Fujisawa, Aya Bamba and Toshikazu Shigeyama. A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311. The Astrophysical Journal. 5th July, 2024 DOI: 10.3847/1538-4357/ad4d99
Funding:
This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. This work was financially supported by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (KAKENHI) Grant Numbers JP24KJ0672(TK), JP21J00031 (HS), JP24K00668 (KK), JP20K04010 (KK), JP20H01904 (KK), JP22H00130 (KK), JP22H01265 (HU), JP19H01936 (TT), JP21H04493 (TT), JP20K14512 (KF), JP23H01211 (AB), JP22K03688 (TS), JP22K03671 (TS), and JP20H05639 (TS). DT is supported by the Sherman Fairchild Postdoctoral Fellowship at the California Institute of Technology. TK is supported by RIKEN Junior Research Associate Program.
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A dynamical model for IRAS 00500+6713: the remnant of a type Iax supernova SN 1181 hosting a double degenerate merger product WD J005311
ARTICLE PUBLICATION DATE
5-Jul-2024
"Motion picture" view of warped Milky Way reveals shape of its dark matter halo
CHINESE ACADEMY OF SCIENCES HEADQUARTERS
A research team led by Dr. HUANG Yang from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) pioneered the "motion picture" method for measuring the precession rate of the Milky Way's disk warp. This method allows the clear observation of the precession direction and rate of the Milky Way's warp using a sample of Cepheid variable stars of different ages. Based on these measurements, the team revealed that the current dark matter halo of the Milky Way is slightly oblate. The study was published online in Nature Astronomy.
In the nearby universe, nearly one-third of disk galaxies are not perfect disks but exhibit a warped shape resembling a potato chip. Astronomers refer to this phenomenon as a disk warp. The Milky Way, as a typical disk galaxy, also has this warp feature. It is generally believed that the warp originates from the rotational plane of the outer disk stars deviating from the symmetry plane of the surrounding dark matter halo. This tilted, rotating Galactic disk, much like a spinning top, inevitably undergoes precession due to the torque exerted by the surrounding dark matter halo.
However, the measurement of this important dynamic parameter, both in direction and rate, has been widely debated. This is because previous measurements relied on indirect kinematic methods, where the tracers used are subject to dynamical perturbations or heating effects, greatly limiting their accuracy and precision.
This study used 2,600 young classical Cepheid variable stars discovered by Gaia as tracers, along with precise distance and age data from both Gaia and LAMOST. The researchers, using the "motion picture" method, constructed the three-dimensional structure of the Milky Way's disk across populations of various ages but all younger than 250 Myr.
By "seeing" how the disk warp evolves with age, the researchers found that the warp precesses in a retrograde direction at a rate of 2 km/s/kpc (or 0.12 degrees per million years).
Further measurements showed that the warp's precession rate gradually decreases with radius. Regardless of the origin of the warp, its precession rate and direction were jointly determined by the Galactic inner disk and the dark matter halo.
After subtracting the contribution of the Galactic inner disk, the researchers found that the current dark matter halo enveloping the warp exhibits a slightly oblate ellipsoidal shape with a flattening ratio q between 0.84 and 0.96 for the equipotential surfaces. Currently, only this shape can explain the remaining precession rate of the warp.
This study provides a crucial anchor point for studying the evolution of the Milky Way's dark matter halo.
One of the greatest mysteries of science could be one step closer to being solved.
Approximately 80% of the matter in the universe is dark, meaning that it cannot be seen. In fact, dark matter is passing through us constantly – possibly at a rate of trillions of particles per second.
We know it exists because we can see the effects of its gravity, but experiments to date have so far failed to detect it.
Taking advantage of the most advanced quantum technologies, scientists from Lancaster University, the University of Oxford, and Royal Holloway, University of London are building the most sensitive dark matter detectors to date.
Their public exhibit entitled “A Quantum View of the Invisible Universe” is showcased at this year’s Royal Society’s flagship Summer Science Exhibition from 2-7 July 2024.
The researchers include Dr Michael Thompson, Professor Edward Laird, Dr Dmitry Zmeev and Dr Samuli Autti from Lancaster, Professor Jocelyn Monroe from Oxford and Professor Andrew Casey from RHUL.
EPSRC Fellow Dr Autti said: “We are using quantum technologies at ultra-low temperatures to build the most sensitive detectors to date. The goal is to observe this mysterious matter directly in the laboratory and solve one of the greatest enigmas in science.”
There is indirect observational evidence of the typical dark matter density in the galaxy, but the mass of the constituent particles and their possible interactions with ordinary atoms are unknown.
Particle physics theory suggests two likely dark matter candidates: new particles with interactions so weak we haven’t observed them yet, and, very light wave-like particles termed axions. The team are building two experiments, one to search for each.
Of the two candidates, new particles with ultra-weak interactions could be detected through their collisions with ordinary matter. However, whether these collisions can be identified in an experiment depends on the mass of the dark matter being searched for. Most searches so far would be able to detect dark matter particles weighing between five and 1,000 times more than a hydrogen atom, but it is possible that much lighter dark matter candidates may have been missed.
The Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology (QUEST-DMC) team aims to reach world-leading sensitivity to collisions with dark matter candidates with mass between 0.01 to a few hydrogen atoms. To achieve this, the detector is made of superfluid helium-3, cooled into a macroscopic quantum state and instrumented with superconducting quantum amplifiers. Combining these two quantum technologies creates the sensitivity to measure extremely weak signatures of dark matter collisions.
By contrast, if dark matter is made from axions, they will be extremely light – more than a billion times lighter than a hydrogen atom – but correspondingly more abundant. Scientists would not be able to detect collisions with axions, but they can search instead for another signature - an electrical signal that results when axions decay in a magnetic field. This effect can only be measured using an exquisitely sensitive amplifier that works at the highest precision allowed by quantum mechanics. The Quantum Sensors for the Hidden Sector (QSHS) team is therefore developing a new class of quantum amplifier that is perfectly suited to search for an axion signal.
The stand at this year’s exhibition will enable visitors to observe the unseeable with imaginative hands-on exhibits for all ages.
Demonstrating how we infer dark matter from observing galaxies, there will be a gyroscope-in-a-box that moves in surprising ways due to the unseen angular momentum. There will also be glass marbles that are transparent in liquid, showing how invisible masses may be observed using clever experimentation.
A light-up dilution refrigerator will demonstrate how the team achieve ultra-low temperatures, and a model dark matter particle collision detector will show how our Universe would behave if dark matter behaved like normal matter.
Visitors can then search for dark matter with a model axion detector by scanning the frequency of a radio receiver, and they can also create their own parametric amplifier using a pendulum.
Cosmologist Carlos Frenk, Fellow of the Royal Society and Chair of the Public Engagement Committee, said: “Science is vital in helping us understand the world we live in – past, present and future. I urge visitors of all ages to come along with an open mind, curiosity and enthusiasm and celebrate incredible scientific achievements that are benefiting us all.”
The research in this exhibit is supported by the UKRI Quantum Technologies for Fundamental Physics programme.
TO FIND OUT HOW MIGRATING BIRDS FIND THEIR WAY, STARLINGS WERE RELOCATED FROM AUTUMN STOPOVERS ALONG THE DUTCH NORTH SEA COAST TO SWITZERLAND (RED, 1948–1957) AND SPAIN (BLUE, 1959–1962).
CREDIT: FROM: REVISITING PERDECK'S MASSIVE AVIAN MIGRATION EXPERIMENTS DEBUNKS ALTERNATIVE SOCIAL INTERPRETATIONS, HTTPS://DOI.ORG/10.1098/RSBL.2024.0217
Young, naïve starlings are looking for their wintering grounds independently of experienced conspecifics. Starlings are highly social birds throughout the year, but this does not mean that they copy the migration route from each other. By revisiting a classic ‘displacement’ experiment and by adding new data, a team of researchers at the Netherlands Institute of Ecology (NIOO-KNAW) and the Swiss Ornithological Institute (Vogelwarte Sempach) have settled a long-lasting debate. Their findings are now published in the scientific journal Biology Letters.
The question of how migratory birds locate their migration routes has intrigued mankind for centuries. Biologist Albert Perdeck from the Netherlands aimed to find answers when he displaced thousands of migrating starlings by plane from the Netherlands to Switzerland and Spain in the 1950’s and 1960’s. This experiment has become a classic study on the migratory orientation of birds. Now, seventy years later, colleagues have confirmed his findings and were able to solve a long-lasting scientific debate using this historical dataset.
Young vs. adult
The birds were individually recognisable using light-weight metal leg rings with a unique code – a method used by the Dutch Centre for Avian Migration and Demography, Vogelwarte Sempach and European partners until this day. Ring recoveries indicated that relocated young and adult starlings used different strategies to reach the winter destinations in the British Isles and France. “Adult starlings were aware of this move and adjusted their migratory orientation to reach their normal wintering areas,” according to Morrison Pot at the NIOO-KNAW. “Young starlings continued in a south-westerly direction – the direction they would have chosen when departing from the Netherlands – and reached ‘wrong’ destinations in southern France and Spain.”
New friends?
Over the years, experts in the field of avian migration have been divided about the interpretation of Perdeck’s results. Pot: “Starlings are highly social animals and, according to some experts, the relocated young starlings may just as well have joined a flock of local conspecifics.” The relocated starlings would have copied the migratory behaviour of their new friends showing them where to go. “If true, the migratory route is largely learned instead of inherited.” A major difference.
The team of researchers retrieved the historical data of Perdeck’s displacement experiments in the paper archives of the Dutch Centre for Avian Migration and Demography and compared the migratory orientation with the migratory behaviour of local Swiss and Spanish starlings. “The latter data were retrieved from institutional archives, but were unavailable in Perdeck’s days.”
Social migrants
By re-analysing this historical dataset, the team showed that the migratory orientation of the relocated starlings differed from the local conspecifics. Starlings are thus no social migrants or ‘copycats’. The alternative social explanation of Perdeck’s results has thus been debunked. As explained by Pot: “Starlings travel independently and decisions about where to go are not overruled by the migratory behaviour of others.” Recently, a study in collaboration with Vogelwarte Sempach showed that starlings migrate at night. This is in line with the 70-year-old findings, because how would you follow someone in the pitch darkness of the night?
Times of change
Learned or inherited behaviour, why does it matter? “In times of rapid changes in global climate and land-use, it is of great importance to understand whether migratory behaviour is largely inherited or learned,” says lead scientist and head of the Dutch Centre for Avian Migration and Demography Henk van der Jeugd. Inherited behaviours are less flexible to rapid change. “Although starlings are numerous and widespread birds that have adjusted to human dominated landscapes, their migratory behaviour is likely less flexible.”
With more than 200 staff members and students, the Netherlands Institute of Ecology (NIOO-KNAW) is one of the largest research institutes of the Royal Netherlands Academy of Arts and Sciences (KNAW). The institute specialises in water and land ecology with three major themes: biodiversity, climate change and the sustainable use of land and water. The institute is located in an innovative and sustainable research building in Wageningen, the Netherlands. NIOO has an impressive research history that stretches back 70 years and spans the entire country, and beyond.
Revisiting Perdeck's massive avian migration experiments debunks alternative social interpretations
ARTICLE PUBLICATION DATE
3-Jul-2024
Innovative battery design: More energy and less environmental impact
ETH ZURICH
Lithium metal batteries are among the most promising candidates of the next generation of high-energy batteries. They can store at least twice as much energy per unit of volume as the lithium-ion batteries that are in widespread use today. This will mean, for example, that an electric car can travel twice as far on a single charge, or that a smartphone will not have to be recharged so often.
At present, there is still one crucial drawback with lithium metal batteries: the liquid electrolyte requires the addition of significant amounts of fluorinated solvents and fluorinated salts, which increases its environmental footprint. Without the addition of fluorine, however, lithium metal batteries would be unstable, they would stop working after very few charging cycles and be prone to short circuits as well as overheating and igniting. A research group led by Maria Lukatskaya, Professor of Electrochemical Energy Systems at ETH Zurich, has now developed a new method that dramatically reduces the amount of fluorine required in lithium metal batteries, thereby rendering them more environmentally friendly and more stable as well as cost-effective.
A stable protective layer increases battery safety and efficiency
The fluorinated compounds from electrolyte help the formation of a protective layer around the metallic lithium at the negative electrode of the battery. “This protective layer can be compared to the enamel of a tooth,” Lukatskaya explains. “It protects the metallic lithium from continuous reaction with electrolyte components.” Without it, the electrolyte would quickly get depleted during cycling, the cell would fail, and the lack of a stable layer would result in the formation of lithium metal whiskers – ‘dendrites’ – during the recharging process instead of a conformal flat layer.
Should these dendrites touch the positive electrode, this would cause a short circuit with the risk that the battery heats up so much that it ignites. The ability to control the properties of this protective layer is therefore crucial for battery performance. A stable protective layer increases battery efficiency, safety and service life.
Minimising fluorine content
“The question was how to reduce the amount of added fluorine without compromising the protective layer’s stability,” says doctoral student Nathan Hong. The group’s new method uses electrostatic attraction to achieve the desired reaction. Here, electrically charged fluorinated molecules serve as a vehicle to transport the fluorine to the protective layer. This means that only 0.1 percent by weight of fluorine is required in the liquid electrolyte, which is at least 20 times lower than in prior studies.
Optimised method makes batteries greener
The ETH Zurich research group describes the new method and its underlying principles in a paper recently published in the journal Energy & Environmental Science. An application for a patent has been made.
One of the biggest challenges was to find the right molecule to which fluorine could be attached and that would also decompose again under the right conditions once it had reached the lithium metal. As the group explains, a key advantage of this method is that it can be seamlessly integrated into the existing battery production process without generating additional costs to change the production setup. The batteries used in the lab were the size of a coin. In a next step, the researchers plan to test the method’s scalability and apply it to pouch cells as used in smartphones.
