Aurelia Butler

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    in Environment

    Silk offers an alternative to some microplastics

    Microplastics, tiny particles of plastic that are now found worldwide in the air, water, and soil, are increasingly recognized as a serious pollution threat, and have been found in the bloodstream of animals and people around the world.

    Some of these microplastics are intentionally added to a variety of products, including agricultural chemicals, paints, cosmetics, and detergents — amounting to an estimated 50,000 tons a year in the European Union alone, according to the European Chemicals Agency. The EU has already declared that these added, nonbiodegradable microplastics must be eliminated by 2025, so the search is on for suitable replacements, which do not currently exist.

    Now, a team of scientists at MIT and elsewhere has developed a system based on silk that could provide an inexpensive and easily manufactured substitute. The new process is described in a paper in the journal Small, written by MIT postdoc Muchun Liu, MIT professor of civil and environmental engineering Benedetto Marelli, and five others at the chemical company BASF in Germany and the U.S.

    The microplastics widely used in industrial products generally protect some specific active ingredient (or ingredients) from being degraded by exposure to air or moisture, until the time they are needed. They provide a slow release of the active ingredient for a targeted period of time and minimize adverse effects to its surroundings. For example, vitamins are often delivered in the form of microcapsules packed into a pill or capsule, and pesticides and herbicides are similarly enveloped. But the materials used today for such microencapsulation are plastics that persist in the environment for a long time. Until now, there has been no practical, economical substitute available that would biodegrade naturally.

    Much of the burden of environmental microplastics comes from other sources, such as the degradation over time of larger plastic objects such as bottles and packaging, and from the wear of car tires. Each of these sources may require its own kind of solutions for reducing its spread, Marelli says. The European Chemical Agency has estimated that the intentionally added microplastics represent approximately 10-15 percent of the total amount in the environment, but this source may be relatively easy to address using this nature-based biodegradable replacement, he says.

    “We cannot solve the whole microplastics problem with one solution that fits them all,” he says. “Ten percent of a big number is still a big number. … We’ll solve climate change and pollution of the world one percent at a time.”

    Unlike the high-quality silk threads used for fine fabrics, the silk protein used in the new alternative material is widely available and less expensive, Liu says. While silkworm cocoons must be painstakingly unwound to produce the fine threads needed for fabric, for this use, non-textile-quality cocoons can be used, and the silk fibers can simply be dissolved using a scalable water-based process. The processing is so simple and tunable that the resulting material can be adapted to work on existing manufacturing equipment, potentially providing a simple “drop in” solution using existing factories.

    Silk is recognized as safe for food or medical use, as it is nontoxic and degrades naturally in the body. In lab tests, the researchers demonstrated that the silk-based coating material could be used in existing, standard spray-based manufacturing equipment to make a standard water-soluble microencapsulated herbicide product, which was then tested in a greenhouse on a corn crop. The test showed it worked even better than an existing commercial product, inflicting less damage to the plants, Liu says.

    While other groups have proposed degradable encapsulation materials that may work at a small laboratory scale, Marelli says, “there is a strong need to achieve encapsulation of high-content actives to open the door to commercial use. The only way to have an impact is where we can not only replace a synthetic polymer with a biodegradable counterpart, but also achieve performance that is the same, if not better.”

    The secret to making the material compatible with existing equipment, Liu explains, is in the tunability of the silk material. By precisely adjusting the polymer chain arrangements of silk materials and addition of a surfactant, it is possible to fine-tune the properties of the resulting coatings once they dry out and harden. The material can be hydrophobic (water-repelling) even though it is made and processed in a water solution, or it can be hydrophilic (water-attracting), or anywhere in between, and for a given application it can be made to match the characteristics of the material it is being used to replace.

    In order to arrive at a practical solution, Liu had to develop a way of freezing the forming droplets of encapsulated materials as they were forming, to study the formation process in detail. She did this using a special spray-freezing system, and was able to observe exactly how the encapsulation works in order to control it better. Some of the encapsulated “payload” materials, whether they be pesticides or nutrients or enzymes, are water-soluble and some are not, and they interact in different ways with the coating material.

    “To encapsulate different materials, we have to study how the polymer chains interact and whether they are compatible with different active materials in suspension,” she says. The payload material and the coating material are mixed together in a solution and then sprayed. As droplets form, the payload tends to be embedded in a shell of the coating material, whether that’s the original synthetic plastic or the new silk material.

    The new method can make use of low-grade silk that is unusable for fabrics, and large quantities of which are currently discarded because they have no significant uses, Liu says. It can also use used, discarded silk fabric, diverting that material from being disposed of in landfills.

    Currently, 90 percent of the world’s silk production takes place in China, Marelli says, but that’s largely because China has perfected the production of the high-quality silk threads needed for fabrics. But because this process uses bulk silk and has no need for that level of quality, production could easily be ramped up in other parts of the world to meet local demand if this process becomes widely used, he says.

    “This elegant and clever study describes a sustainable and biodegradable silk-based replacement for microplastic encapsulants, which are a pressing environmental challenge,” says Alon Gorodetsky, an associate professor of chemical and biomolecular engineering at the University of California at Irvine, who was not associated with this research. “The modularity of the described materials and the scalability of the manufacturing processes are key advantages that portend well for translation to real-world applications.”

    This process “represents a potentially highly significant advance in active ingredient delivery for a range of industries, particularly agriculture,” says Jason White, director of the Connecticut Agricultural Experiment Station, who also was not associated with this work. “Given the current and future challenges related to food insecurity, agricultural production, and a changing climate, novel strategies such as this are greatly needed.”

    The research team also included Pierre-Eric Millard, Ophelie Zeyons, Henning Urch, Douglas Findley and Rupert Konradi from the BASF corporation, in Germany and in the U.S. The work was supported by BASF through the Northeast Research Alliance (NORA). More

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    in Environment

    Four researchers with MIT ties earn Schmidt Science Fellowships

    Four researchers with MIT ties — Juncal Arbelaiz, Xiangkun (Elvis) Cao, Sandya Subramanian, and Heather Zlotnick ’17 — have been honored with competitive Schmidt Science Fellowships.

    Created in 2017, the fellows program aims to bring together the world’s brightest minds “to solve society’s toughest challenges.”

    The four MIT-affiliated researchers are among 29 Schmidt Science Fellows from around the world who will receive postdoctoral support for either one or two years with an annual stipend of $100,000, along with individualized mentoring and participation in the program’s Global Meeting Series. The fellows will also have opportunities to engage with thought-leaders from science, business, policy, and society. According to the award announcement, the fellows are expected to pursue research that shifts from the focus of their PhDs, to help expand and enhance their futures as scientific leaders.

    Juncal Arbelaiz is a PhD candidate in applied mathematics at MIT, who is completing her doctorate this summer. Her doctoral research at MIT is advised by Ali Jadbabaie, the JR East Professor of Engineering and head of the Department of Civil and Environmental Engineering; Anette Hosoi, the Neil and Jane Pappalardo Professor of Mechanical Engineering and associate dean of the School of Engineering; and Bassam Bamieh, professor of mechanical engineering and associate director of the Center for Control, Dynamical Systems, and Computation at the University of California at Santa Barbara. Arbelaiz’s research revolves around the design of optimal decentralized intelligence for spatially-distributed dynamical systems.

    “I cannot think of a better way to start my independent scientific career. I feel very excited and grateful for this opportunity,” says Arbelaiz. With her fellowship, she will enlist systems biology to explore how the nervous system encodes and processes sensory information to address future safety-critical artificial intelligence applications. “The Schmidt Science Fellowship will provide me with a unique opportunity to work at the intersection of biological and machine intelligence for two years and will be a steppingstone towards my longer-term objective of becoming a researcher in bio-inspired machine intelligence,” she says.

    Xiangkun (Elvis) Cao is currently a postdoc in the lab of T. Alan Hatton, the Ralph Landau Professor in Chemical Engineering, and an Impact Fellow at the MIT Climate and Sustainability Consortium. Cao received his PhD in mechanical engineering from Cornell University in 2021, during which he focused on microscopic precision in the simultaneous delivery of light and fluids by optofluidics, with advances relevant to health and sustainability applications. As a Schmidt Science Fellow, he plans to be co-advised by Hatton on carbon capture, and Ted Sargent, professor of chemistry at Northwestern University, on carbon utilization. Cao is passionate about integrated carbon capture and utilization (CCU) from molecular to process levels, machine learning to inspire smart CCU, and the nexus of technology, business, and policy for CCU.

    “The Schmidt Science Fellowship provides the perfect opportunity for me to work across disciplines to study integrated carbon capture and utilization from molecular to process levels,” Cao explains. “My vision is that by integrating carbon capture and utilization, we can concurrently make scientific discoveries and unlock economic opportunities while mitigating global climate change. This way, we can turn our carbon liability into an asset.”

    Sandya Subramanian, a 2021 PhD graduate of the Harvard-MIT Program in Health Sciences and Technology (HST) in the area of medical engineering and medical physics, is currently a postdoc at Stanford Data Science. She is focused on the topics of biomedical engineering, statistics, machine learning, neuroscience, and health care. Her research is on developing new technologies and methods to study the interactions between the brain, the autonomic nervous system, and the gut. “I’m extremely honored to receive the Schmidt Science Fellowship and to join the Schmidt community of leaders and scholars,” says Subramanian. “I’ve heard so much about the fellowship and the fact that it can open doors and give people confidence to pursue challenging or unique paths.”

    According to Subramanian, the autonomic nervous system and its interactions with other body systems are poorly understood but thought to be involved in several disorders, such as functional gastrointestinal disorders, Parkinson’s disease, diabetes, migraines, and eating disorders. The goal of her research is to improve our ability to monitor and quantify these physiologic processes. “I’m really interested in understanding how we can use physiological monitoring technologies to inform clinical decision-making, especially around the autonomic nervous system, and I look forward to continuing the work that I’ve recently started at Stanford as Schmidt Science Fellow,” she says. “A huge thank you to all of the mentors, colleagues, friends, and leaders I had the pleasure of meeting and working with at HST and MIT; I couldn’t have done this without everything I learned there.”

    Hannah Zlotnick ’17 attended MIT for her undergraduate studies, majoring in biological engineering with a minor in mechanical engineering. At MIT, Zlotnick was a student-athlete on the women’s varsity soccer team, a UROP student in Alan Grodzinsky’s laboratory, and a member of Pi Beta Phi. For her PhD, Zlotnick attended the University of Pennsylvania, and worked in Robert Mauck’s laboratory within the departments of Bioengineering and Orthopaedic Surgery.

    Zlotnick’s PhD research focused on harnessing remote forces, such as magnetism or gravity, to enhance engineered cartilage and osteochondral repair both in vitro and in large animal models. Zlotnick now plans to pivot to the field of biofabrication to create tissue models of the knee joint to assess potential therapeutics for osteoarthritis. “I am humbled to be a part of the Schmidt Science Fellows community, and excited to venture into the field of biofabrication,” Zlotnick says. “Hopefully this work uncovers new therapies for patients with inflammatory joint diseases.” More

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    in Environment

    Charting the landscape at MIT

    Norman Magnuson’s MIT career — culminating in his role as manager of grounds services in the Department of Facilities for the past 20 years — started in 1974 with a summer job. Fresh out of high school and unsure of his next step, Magnuson’s father, Norman Sr., a housing manager at MIT, encouraged him to take a summer staffer position with MIT Grounds Services. That temporary job would turn into a 48-year career, in which Magnuson found and fed his passion for horticulture.

    Over the years, Magnuson has had a number of roles, including mover, truck driver, and landscaper. In his most recent role, Magnuson was responsible for managing and maintaining the grounds of MIT’s more-than-168-acre campus — work that includes landscaping, snow removal, and event setup — a position where his pride of work could be seen across campus. Now, after nearly half a century at the Institute, Magnuson is retiring, leaving an enormous set of shoes to fill.

    “Norman’s passion for stewarding an immense array of green spaces has delighted the eyes of tens of thousands of people from around the world who have worked, visited, studied, and resided at MIT over the years,” says Vice President for Campus Services and Stewardship Joe Higgins. Adds Martin O’Brien, senior manager of Campus Services, “Not only do he and his team excel at high-profile events like snowstorms and Commencement, but day to day, they keep the campus shining.”

    Touching six decades on a transforming campus

    Like many who have spent dozens of years at the Institute, when asked what has changed the most in his time here, Magnuson thinks first of MIT’s skyline. He notes that the Landau Building (Building 66) was the first new construction he saw on campus. He remembers seeing E40 and E51 be transformed from warehouses to more functional spaces for research and labs — a pattern that would be repeated often during his time at MIT. As each part of campus dramatically evolved, so did the quiet and steadfast work of Magnuson and Grounds Services.

    When Magnuson first started working for Grounds Services, he says that landscaping was often an afterthought. “We worked with whatever extra budget money there was,” he remembers, speaking of the landscaping support for new buildings. Magnuson says that over his long career, the work of his department became more professionalized and integrated with departments like the Office of Campus Planning. Grounds Services now works closely with that office to support design and management of resilient campus landscapes that incorporate systems of soils, plantings, and hardscapes for stormwater management, as well as mitigating heat island effects while growing and diversifying the urban forest canopy.

    “There’s growing recognition of the contributions that our campus green spaces make to both community well-being and campus resiliency,” explains Laura Tenny, senior campus planner. “Over the last two years, people have rediscovered the outdoors as a place to come together, and so these campus spaces have become part of the social fabric of MIT. As landscapes become more performance-based and more like living green infrastructure, Norman has overseen a complex campus system that’s working at multiple levels, not unlike our sophisticated building and infrastructure systems.”

    Magnuson says he always welcomed change in the landscaping space and has worked hard to drive it. “I like to be on the cutting edge,” he says highlighting environmentally- and climate-friendly change he’s pushed for. “I can remember when we used to do things like throw leaves in the trash in plastic garbage bags,” he says. “These days, we’ve almost eliminated herbicides and pesticides, we’re mindful of the fertilizer that we use, and we’re very cognizant of things like this because we work with teams like the Office of Sustainability (MITOS).”

    As Magnuson and his team have striven to do better for the environment, he notes that he has also seen firsthand how climate change is transforming the campus landscape: “Leaves fall off the deciduous trees earlier than they used to. This year the azaleas bloomed late; the rhododendrons were a little bit early. When you look at particular plants that have been in the ground for many years, you do see the difference,” he says, adding that snow seasons have also become more unpredictable despite improved forecasting technology.

    Enduring connections with the community

    With his craft and campus always changing, one thing remained constant for Magnuson: MIT students. Magnuson and his team have connected with students for countless interviews and research projects over the years — a highlight of his work and a reminder of its impact. “I always tell my staff that we help educate the students — not directly most times, but we are part of the mechanism that makes it possible for them to be here,” he says.

    A recent project for Magnuson was working with students to create and maintain The Hive Garden, MIT’s first sustainability garden and a collaborative project between MITOS, the Undergraduate Association Committee on Sustainability, and Grounds Services. “That was probably one of my favorite interactions with the students,” Magnuson says of the garden. Susy Jones, senior sustainability project manager who worked with Magnuson on the garden, says Magnuson played an essential role: “He took real joy in working with the students — they brought him sketches of these complex hexagonal garden beds, and I watched him and his team sit patiently with them and come up with something we could implement quickly that would maintain the integrity of their designs,” she remembers. “His team happily taught the students how to irrigate the beds and which plants to cut back in the winter — little lessons about the natural world they’ll take with them forever.” 

    As Magnuson begins his retirement, he capped off his career with one more go at this favorite MIT event — Commencement. Though the event requires tremendous amounts of work for Grounds Services, Magnuson looks forward to it each year. “It’s our Super Bowl,” he says. Each spring the Grounds Services team partners with the MIT Repair and Maintenance Carpentry crew to ready Killian Court for several thousand people by turning the open court into a massive seating area and stage while protecting and highlighting the grounds. “When the students come in and they announce them, it’s always an emotional moment for me, because it’s, ‘OK, this is it, it started, and everything looks perfect,’” he says. Former executive officer for Commencement Gayle Gallagher, who worked closely with Magnuson for more than two dozen Commencement weekends, agrees with the “perfect” assessment. “His commitment to the campus grounds — regardless of the season — was unparalleled. He spent countless hours each year to ensure our campus looked its absolute best for our graduates, their families and guests, and our alumni,” she recalls. “I always looked forward to collaborating with him — he is simply one-of-a-kind.”

    When Magnuson looks back on his long career, he notes that community and camaraderie are a large part of what kept him with MIT for so long. He’s built many relationships at MIT (his wife, Diane, recently retired from MIT Medical after 44 years, and his daughter Kelsey works with the Department of Facilities Contracts team) and says his department has the unique ability to support individuals and foster careers like it did for him. “We have some very, very talented people and we have a lot of people like me who learned on the job. Landscaping is one of those professions that if you put your all into it, you can get a degree in landscaping without having an actual degree,” he says.

    “Everybody that works for Grounds is so proud of what they do — you can see it in the work,” he adds. “I’m so proud of the work I’ve done.” More

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    in Environment

    Better living through multicellular life cycles

    Cooperation is a core part of life for many organisms, ranging from microbes to complex multicellular life. It emerges when individuals share resources or partition a task in such a way that each derives a greater benefit when acting together than they could on their own. For example, birds and fish flock to evade predators, slime mold swarms to hunt for food and reproduce, and bacteria form biofilms to resist stress.

    Individuals must live in the same “neighborhood” to cooperate. For bacteria, this neighborhood can be as small as tens of microns. But in environments like the ocean, it’s rare for cells with the same genetic makeup to co-occur in the same neighborhood on their own. And this necessity poses a puzzle to scientists: In environments where survival hinges on cooperation, how do bacteria build their neighborhood?

    To study this problem, MIT professor Otto X. Cordero and colleagues took inspiration from nature: They developed a model system around a common coastal seawater bacterium that requires cooperation to eat sugars from brown algae. In the system, single cells were initially suspended in seawater too far away from other cells to cooperate. To share resources and grow, the cells had to find a mechanism of creating a neighborhood. “Surprisingly, each cell was able to divide and create its own neighborhood of clones by forming tightly packed clusters,” says Cordero, associate professor in the Department of Civil and Environmental Engineering.

    A new paper, published today in Current Biology, demonstrates how an algae-eating bacterium solves the engineering challenge of creating local cell density starting from a single-celled state.

    “A key discovery was the importance of phenotypic heterogeneity in supporting this surprising mechanism of clonal cooperation,” says Cordero, lead author of the new paper.

    Using a combination of microscopy, transcriptomics, and labeling experiments to profile a cellular metabolic state, the researchers found that cells phenotypically differentiate into a sticky “shell” population and a motile, carbon-storing “core.” The researchers propose that shell cells create the cellular neighborhood needed to sustain cooperation while core cells accumulate stores of carbon that support further clonal reproduction when the multicellular structure ruptures.

    This work addresses a key piece in the bigger challenge of understanding the bacterial processes that shape our earth, such as the cycling of carbon from dead organic matter back into food webs and the atmosphere. “Bacteria are fundamentally single cells, but often what they accomplish in nature is done through cooperation. We have much to uncover about what bacteria can accomplish together and how that differs from their capacity as individuals,” adds Cordero.

    Co-authors include Julia Schwartzman and Ali Ebrahimi, former postdocs in the Cordero Lab. Other co-authors are Gray Chadwick, a former graduate student at Caltech; Yuya Sato, a senior researcher at Japan’s National Institute of Advanced Industrial Science and Technology; Benjamin Roller, a current postdoc at the University of Vienna; and Victoria Orphan of Caltech.

    Funding was provided by the Simons Foundation. Individual authors received support from the Swiss National Science Foundation, Japan Society for the Promotion of Science, the U.S. National Science Foundation, the Kavli Institute of Theoretical Physics, and the National Institutes of Health. More

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    in Environment

    Kerry Emanuel: A climate scientist and meteorologist in the eye of the storm

    Kerry Emanuel once joked that whenever he retired, he would start a “hurricane safari” so other people could experience what it’s like to fly into the eye of a hurricane.

    “All of a sudden, the turbulence stops, the sun comes out, bright sunshine, and it’s amazingly calm. And you’re in this grand stadium [of clouds miles high],” he says. “It’s quite an experience.”

    While the hurricane safari is unlikely to come to fruition — “You can’t just conjure up a hurricane,” he explains — Emanuel, a world-leading expert on links between hurricanes and climate change, is retiring from teaching in the Department of Earth Atmospheric and Planetary Sciences (EAPS) at MIT after a more than 40-year career.

    Best known for his foundational contributions to the science of tropical cyclones, climate, and links between them, Emanuel has also been a prominent voice in public debates on climate change, and what we should do about it.

    “Kerry has had an enormous effect on the world through the students and junior scientists he has trained,” says William Boos PhD ’08, an atmospheric scientist at the University of California at Berkeley. “He’s a brilliant enough scientist and theoretician that he didn’t need any of us to accomplish what he has, but he genuinely cares about educating new generations of scientists and helping to launch their careers.”

    In recognition of Emanuel’s teaching career and contributions to science, a symposium was held in his honor at MIT on June 21 and 22, organized by several of his former students and collaborators, including Boos. Research presented at the symposium focused on the many fields influenced by Emanuel’s more than 200 published research papers — on everything from forecasting the risks posed by tropical cyclones to understanding how rainfall is produced by continent-sized patterns of atmospheric circulation.

    Emanuel’s career observing perturbations of Earth’s atmosphere started earlier than he can remember. “According to my older brother, from the age of 2, I would crawl to the window whenever there was a thunderstorm,” he says. At first, those were the rolling thunderheads of the Midwest where he grew up, then it was the edges of hurricanes during a few teenage years in Florida. Eventually, he would find himself watching from the very eye of the storm, both physically and mathematically.

    Emanuel attended MIT both as an undergraduate studying Earth and planetary sciences, and for his PhD in meteorology, writing a dissertation on thunderstorms that form ahead of cold fronts. Within the department, he worked with some of the central figures of modern meteorology such as Jule Charney, Fred Sanders, and Edward Lorenz — the founder of chaos theory.

    After receiving his PhD in 1978, Emanuel joined the faculty of the University of California at Los Angeles. During this period, he also took a semester sabbatical to film the wind speeds of tornadoes in Texas and Oklahoma. After three years, he returned to MIT and joined the Department of Meteorology in 1981. Two years later, the department merged with Earth and Planetary Sciences to form EAPS as it is known today, and where Emanuel has remained ever since.

    At MIT, he shifted scales. The thunderstorms and tornadoes that had been the focus of Emanuel’s research up to then were local atmospheric phenomena, or “mesoscale” in the language of meteorologists. The larger “synoptic scale” storms that are hurricanes blew into Emanuel’s research when as a young faculty member he was asked to teach a class in tropical meteorology; in prepping for the class, Emanuel found his notes on hurricanes from graduate school no longer made sense.

    “I realized I didn’t understand them because they couldn’t have been correct,” he says. “And so I set out to try to find a much better theoretical formulation for hurricanes.”

    He soon made two important contributions. In 1986, his paper “An Air-Sea Interaction Theory for Tropical Cyclones. Part 1: Steady-State Maintenance” developed a new theory for upper limits of hurricane intensity given atmospheric conditions. This work in turn led to even larger-scale questions to address. “That upper bound had to be dependent on climate, and it was likely to go up if we were to warm the climate,” Emanuel says — a phenomenon he explored in another paper, “The Dependence of Hurricane Intensity on Climate,” which showed how warming sea surface temperatures and changing atmospheric conditions from a warming climate would make hurricanes more destructive.

    “In my view, this is among the most remarkable achievements in theoretical geophysics,” says Adam Sobel PhD ’98, an atmospheric scientist at Columbia University who got to know Emanuel after he graduated and became interested in tropical meteorology. “From first principles, using only pencil-and-paper analysis and physical reasoning, he derives a quantitative bound on hurricane intensity that has held up well over decades of comparison to observations” and underpins current methods of predicting hurricane intensity and how it changes with climate.

    This and diverse subsequent work led to numerous honors, including membership to the American Philosophical Society, the National Academy of Sciences, and the American Academy of Arts and Sciences.

    Emanuel’s research was never confined to academic circles, however; when politicians and industry leaders voiced loud opposition to the idea that human-caused climate change posed a threat, he spoke up.

    “I felt kind of a duty to try to counter that,” says Emanuel. “I thought it was an interesting challenge to see if you could go out and convince what some people call climate deniers, skeptics, that this was a serious risk and we had to treat it as such.”

    In addition to many public lectures and media appearances discussing climate change, Emanuel penned a book for general audiences titled “What We Know About Climate Change,” in addition to a widely-read primer on climate change and risk assessment designed to influence business leaders.

    “Kerry has an unmatched physical understanding of tropical climate phenomena,” says Emanuel’s colleague, Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies at EAPS. “But he’s also a great communicator and has generously given his time to public outreach. His book ‘What We Know About Climate Change’ is a beautiful piece of work that is readily understandable and has captivated many a non-expert reader.”

    Along with a number of other prominent climate scientists, Emanuel also began advocating for expanding nuclear power as the most rapid path to decarbonizing the world’s energy systems.

    “I think the impediment to nuclear is largely irrational in the United States,” he says. “So, I’ve been trying to fight that just like I’ve been trying to fight climate denial.”

    One lesson Emanuel has taken from his public work on climate change is that skeptical audiences often respond better to issues framed in positive terms than to doom and gloom; he’s found emphasizing the potential benefits rather than the sacrifices involved in the energy transition can engage otherwise wary audiences.

    “It’s really not opposition to science, per se,” he says. “It’s fear of the societal changes they think are required to do something about it.”

    He has also worked to raise awareness about how insurance companies significantly underestimate climate risks in their policies, in particular by basing hurricane risk on unreliable historical data. One recent practical result has been a project by the First Street Foundation to assess the true flood risk of every property in the United States using hurricane models Emanuel developed.

    “I think it’s transformative,” Emanuel says of the project with First Street. “That may prove to be the most substantive research I’ve done.”

    Though Emanuel is retiring from teaching, he has no plans to stop working. “When I say ‘retire’ it’s in quotes,” he says. In 2011, Emanuel and Professor of Geophysics Daniel Rothman founded the Lorenz Center, a climate research center at MIT in honor of Emanuel’s mentor and friend Edward Lorenz. Emanuel will continue to participate in work at the center, which aims to counter what Emanuel describes as a trend away from “curiosity-driven” work in climate science.

    “Even if there were no such thing as global warming, [climate science] would still be a really, really exciting field,” says Emanuel. “There’s so much to understand about climate, about the climates of the past, about the climates of other planets.”

    In addition to work with the Lorenz Center, he’s become interested once again in tornadoes and severe local storms, and understanding whether climate also controls such local phenomena. He’s also involved in two of MIT’s Climate Grand Challenges projects focused on translating climate hazards to explicit financial and health risks — what will bring the dangers of climate change home to people, he says, is for the public to understand more concrete risks, like agricultural failure, water shortages, electricity shortages, and severe weather events. Capturing that will drive the next few years of his work.

    “I’m going to be stepping up research in some respects,” he says, now living full-time at his home in Maine.

    Of course, “retiring” does mean a bit more free time for new pursuits, like learning a language or an instrument, and “rediscovering the art of sailing,” says Emanuel. He’s looking forward to those days on the water, whatever storms are to come. More

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    in Security

    Could used beer yeast be the solution to heavy metal contamination in water?

    A new analysis by researchers at MIT’s Center for Bits and Atoms (CBA) has found that inactive yeast could be effective as an inexpensive, abundant, and simple material for removing lead contamination from drinking water supplies. The study shows that this approach can be efficient and economic, even down to part-per-billion levels of contamination. Serious damage to human health is known to occur even at these low levels.

    The method is so efficient that the team has calculated that waste yeast discarded from a single brewery in Boston would enough to treat the city’s entire water supply. Such a fully sustainable system would not only purify the water but also divert what would otherwise be a waste stream needing disposal.

    The findings are detailed today in the journal Nature Communications Earth and Environment, in a paper by MIT Research Scientist Patritsia Statathou; Brown University postdoc and MIT Visiting Scholar Christos Athanasiou; MIT Professor Neil Gershenfeld, the director of CBA; and nine others at MIT, Brown, Wellesley College, Nanyang Technological University, and National Technical University of Athens.

    Lead and other heavy metals in water are a significant global problem that continues to grow because of electronic waste and discharges from mining operations. In the U.S. alone, more than 12,000 miles of waterways are impacted by acidic mine-drainage-water rich in heavy metals, the country’s leading source of water pollution. And unlike organic pollutants, most of which can be eventually broken down, heavy metals don’t biodegrade, but persist indefinitely and bioaccumulate. They are either impossible or very expensive to completely remove by conventional methods such as chemical precipitation or membrane filtration.

    Lead is highly toxic, even at tiny concentrations, especially affecting children as they grow. The European Union has reduced its standard for allowable lead in drinking water from 10 parts per billion to 5 parts per billion. In the U.S., the Environmental Protection Agency has declared that no level at all in water supplies is safe. And average levels in bodies of surface water globally are 10 times higher than they were 50 years ago, ranging from 10 parts per billion in Europe to hundreds of parts per billion in South America.

    “We don’t just need to minimize the existence of lead; we need to eliminate it in drinking water,” says Stathatou. “And the fact is that the conventional treatment processes are not doing this effectively when the initial concentrations they have to remove are low, in the parts-per-billion scale and below. They either fail to completely remove these trace amounts, or in order to do so they consume a lot of energy and they produce toxic byproducts.”

    The solution studied by the MIT team is not a new one — a process called biosorption, in which inactive biological material is used to remove heavy metals from water, has been known for a few decades. But the process has been studied and characterized only at much higher concentrations, at more than one part-per-million levels. “Our study demonstrates that the process can indeed work efficiently at the much lower concentrations of typical real-world water supplies, and investigates in detail the mechanisms involved in the process,” Athanasiou says.

    The team studied the use of a type of yeast widely used in brewing and in industrial processes, called S. cerevisiae, on pure water spiked with trace amounts of lead. They demonstrated that a single gram of the inactive, dried yeast cells can remove up to 12 milligrams of lead in aqueous solutions with initial lead concentrations below 1 part per million. They also showed that the process is very rapid, taking less than five minutes to complete.

    Because the yeast cells used in the process are inactive and desiccated, they require no particular care, unlike other processes that rely on living biomass to perform such functions which require nutrients and sunlight to keep the materials active. What’s more, yeast is abundantly available already, as a waste product from beer brewing and from various other fermentation-based industrial processes.

    Stathatou has estimated that to clean a water supply for a city the size of Boston, which uses about 200 million gallons a day, would require about 20 tons of yeast per day, or about 7,000 tons per year. By comparison, one single brewery, the Boston Beer Company, generates 20,000 tons a year of surplus yeast that is no longer useful for fermentation.

    The researchers also performed a series of tests to determine that the yeast cells are responsible for biosorption. Athanasiou says that “exploring biosorption mechanisms at such challenging concentrations is a tough problem. We were the first to use a mechanics perspective to unravel biosorption mechanisms, and we discovered that the mechanical properties of the yeast cells change significantly after lead uptake. This provides fundamentally new insights for the process.”

    Devising a practical system for processing the water and retrieving the yeast, which could then be separated from the lead for reuse, is the next stage of the team’s research, they say.

    “To scale up the process and actually put it in place, you need to embed these cells in a kind of filter, and this is the work that’s currently ongoing,” Stathatou says. They are also looking at ways of recovering both the cells and the lead. “We need to conduct further experiments, but there is the option to get both back,” she says.

    The same material can potentially be used to remove other heavy metals, such as cadmium and copper, but that will require further research to quantify the effective rates for those processes, the researchers say.

    “This research revealed a very promising, inexpensive, and environmentally friendly solution for lead removal,” says Sivan Zamir, vice president of Xylem Innovation Labs, a water technology research firm, who was not associated with this research. “It also deepened our understanding of the biosorption process, paving the way for the development of materials tailored to removal of other heavy metals.”

    The team also included Marios Tsezos at the National Technical University of Athens, in Greece; John Gross at Wellesley College; Camron Blackburn, Filippos Tourlomousis, and Andreas Mershin at MIT’s CBA; Brian Sheldon, Nitin Padture, Eric Darling at Brown University; and Huajian Gao at Brown University and Nanyang Technological University, in Singapore. More

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    in Environment

    Helping renewable energy projects succeed in local communities

    Jungwoo Chun makes surprising discoveries about sustainability initiatives by zooming in on local communities.

    His discoveries lie in understanding how renewable energy infrastructure develops at a local level. With so many stakeholders in a community — citizens, government officials, businesses, and other organizations — the development process gets complicated very quickly. Chun works to unpack stakeholder relationships to help local renewable energy projects move forward.

    While his interests today are in local communities around the U.S., Chun comes from a global background. Growing up, his family moved frequently due to his dad’s work. He lived in Seoul, South Korea until elementary school and then hopped from city to city around Asia, spending time in China, Hong Kong, and Singapore. When it was time for college, he returned to South Korea, majoring in international studies at Korea University and later completing his master’s there in the same field.

    After graduating, Chun wanted to leverage his international expertise to tackle climate change. So, he pursued a second master’s in international environmental policy with William Moomaw at Tufts University.

    During that time, Chun came across an article on climate change by David Victor, a professor in public policy at the University of California at San Diego. Victor argued that while international efforts to fight climate change are necessary, more tangible progress can be made through local efforts catered to each country. That prompted Chun to think a step further: “What can we do in the local community to make a little bit of a difference, which could add up to something big in the long term?”

    With a renewed direction for his goals, Chun arrived at the MIT Department of Urban Studies and Planning, specializing in environmental policy and planning. But he was still missing that final inspirational spark to proactively pursue his goals — until he began working with his primary advisor, Lawrence Susskind, the Ford Professor of Urban and Environmental Planning and director of the Science Impact Collaborative.

    For previous research projects, “I would just do what I was told,” Chun says, but his new advisor “really opened [his] eyes” to being an active member of the community. From the start, Susskind has encouraged Chun to share his research ideas and has shown him how to leverage his research skills for public service. Over the past few years, Chun has also taught several classes with Susskind, learning to approach education thoughtfully for an engaging and equitable classroom. Because of their relationship, Chun now always searches for ways to make a difference through research, teaching, and public service.

    Understanding renewable energy projects at a local level

    For his main dissertation project with Susskind, Chun is studying community-owned solar energy projects, working to understand what makes them successful.

    Often, communities don’t have the required expertise to carry out these projects on their own and instead look to advisory organizations for help. But little research has been done on these organizations and the roles that they play in developing solar energy infrastructure.

    Through over 200 surveys and counting, Chun has discovered that these organizations act as life-long collaborators to communities and are critical in getting community-owned solar projects up and running. At the start of these projects, they walk communities through a mountain of logistics for setting up solar energy infrastructure, including permit applications, budgeting, and contractor employment. After the infrastructure is in place, the organizations stay involved, serving as consultants when needed and sometimes even becoming partners.

    Because of these roles, Chun calls these organizations “intermediaries,” drawing a parallel with roles in in conflict resolution. “But it’s much more than that,” he adds. Intermediaries help local communities “build a movement [for community-owned solar energy projects] … and empower them to be independent and self-sustaining.”

    Chun is also working on another project with Susskind, looking at situations where communities are opposed to renewable energy infrastructure. For this project, Chun is supervising and mentoring a group of five undergraduates. Together, they are trying to pinpoint the reasons behind local opposition to renewable energy projects.

    The idea for this project emerged two years ago, when Chun heard in the news that many solar and wind projects were being delayed or cancelled due to local opposition. But the reasons for this opposition weren’t thoroughly researched.

    “When we started to dig a little deeper, [we found that] communities oppose these projects even though they aren’t opposed to renewable energy,” Chun says. The primary reasons for opposition lie in land use concerns, including financial challenges, health and safety concerns, and ironically, environmental consequences. By better understanding these concerns, Chun hopes to help more renewable energy projects succeed and bring society closer to a sustainable future.

    Bringing research to the classroom and community

    Right now, Chun is looking to bring his research insights on renewable energy infrastructure into the classroom. He’s developing a course on renewable energy that will act as a “clinic” where students will work with communities to understand their concerns for potential renewable energy projects. The students’ findings will then be passed onto project leaders to help them address these concerns.

    This new course is modeled after 11.074/11.274 (Cybersecurity Clinic), which Chun has helped develop over the past few years. In this clinic, students work with local governments in New England to assess potential cybersecurity vulnerabilities in their digital systems. At first, “a lot of city governments were very skeptical, like ‘students doing service for us…?’” Chun says. “But in the end, they were all very satisfied with the outcome” and found the assessments “impactful.”

    Since the Cybersecurity Clinic has kicked off, other universities have approached Chun and his co-instructors about developing their own regional clinics. Now, there are cybersecurity clinics operating around the world. “That’s been a huge success,” Chun says. Going forward, “we’d like to expand the benefit of this clinic [to address] communities opposing renewable energy [projects].” The new course will be a philosophical trifecta for Chun, combining his commitments to research, teaching, and public service.

    Chun plans to wrap up his PhD at the end of this summer and is currently writing his dissertation on community-owned solar energy projects. “I’m done with all the background work — working the soil and throwing the seeds in the right place,” he says, “It’s now time to gather all the crops and present the work.” More

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    in Environment

    Study finds natural sources of air pollution exceed air quality guidelines in many regions

    Alongside climate change, air pollution is one of the biggest environmental threats to human health. Tiny particles known as particulate matter or PM2.5 (named for their diameter of just 2.5 micrometers or less) are a particularly hazardous type of pollutant. These particles are produced from a variety of sources, including wildfires and the burning of fossil fuels, and can enter our bloodstream, travel deep into our lungs, and cause respiratory and cardiovascular damage. Exposure to particulate matter is responsible for millions of premature deaths globally every year.

    In response to the increasing body of evidence on the detrimental effects of PM2.5, the World Health Organization (WHO) recently updated its air quality guidelines, lowering its recommended annual PM2.5 exposure guideline by 50 percent, from 10 micrograms per meter cubed (μm3) to 5 μm3. These updated guidelines signify an aggressive attempt to promote the regulation and reduction of anthropogenic emissions in order to improve global air quality.

    A new study by researchers in the MIT Department of Civil and Environmental Engineering explores if the updated air quality guideline of 5 μm3 is realistically attainable across different regions of the world, particularly if anthropogenic emissions are aggressively reduced. 

    The first question the researchers wanted to investigate was to what degree moving to a no-fossil-fuel future would help different regions meet this new air quality guideline.

    “The answer we found is that eliminating fossil-fuel emissions would improve air quality around the world, but while this would help some regions come into compliance with the WHO guidelines, for many other regions high contributions from natural sources would impede their ability to meet that target,” says senior author Colette Heald, the Germeshausen Professor in the MIT departments of Civil and Environmental Engineering, and Earth, Atmospheric and Planetary Sciences. 

    The study by Heald, Professor Jesse Kroll, and graduate students Sidhant Pai and Therese Carter, published June 6 in the journal Environmental Science and Technology Letters, finds that over 90 percent of the global population is currently exposed to average annual concentrations that are higher than the recommended guideline. The authors go on to demonstrate that over 50 percent of the world’s population would still be exposed to PM2.5 concentrations that exceed the new air quality guidelines, even in the absence of all anthropogenic emissions.

    This is due to the large natural sources of particulate matter — dust, sea salt, and organics from vegetation — that still exist in the atmosphere when anthropogenic emissions are removed from the air. 

    “If you live in parts of India or northern Africa that are exposed to large amounts of fine dust, it can be challenging to reduce PM2.5 exposures below the new guideline,” says Sidhant Pai, co-lead author and graduate student. “This study challenges us to rethink the value of different emissions abatement controls across different regions and suggests the need for a new generation of air quality metrics that can enable targeted decision-making.”

    The researchers conducted a series of model simulations to explore the viability of achieving the updated PM2.5 guidelines worldwide under different emissions reduction scenarios, using 2019 as a representative baseline year. 

    Their model simulations used a suite of different anthropogenic sources that could be turned on and off to study the contribution of a particular source. For instance, the researchers conducted a simulation that turned off all human-based emissions in order to determine the amount of PM2.5 pollution that could be attributed to natural and fire sources. By analyzing the chemical composition of the PM2.5 aerosol in the atmosphere (e.g., dust, sulfate, and black carbon), the researchers were also able to get a more accurate understanding of the most important PM2.5 sources in a particular region. For example, elevated PM2.5 concentrations in the Amazon were shown to predominantly consist of carbon-containing aerosols from sources like deforestation fires. Conversely, nitrogen-containing aerosols were prominent in Northern Europe, with large contributions from vehicles and fertilizer usage. The two regions would thus require very different policies and methods to improve their air quality. 

    “Analyzing particulate pollution across individual chemical species allows for mitigation and adaptation decisions that are specific to the region, as opposed to a one-size-fits-all approach, which can be challenging to execute without an understanding of the underlying importance of different sources,” says Pai. 

    When the WHO air quality guidelines were last updated in 2005, they had a significant impact on environmental policies. Scientists could look at an area that was not in compliance and suggest high-level solutions to improve the region’s air quality. But as the guidelines have tightened, globally-applicable solutions to manage and improve air quality are no longer as evident. 

    “Another benefit of speciating is that some of the particles have different toxicity properties that are correlated to health outcomes,” says Therese Carter, co-lead author and graduate student. “It’s an important area of research that this work can help motivate. Being able to separate out that piece of the puzzle can provide epidemiologists with more insights on the different toxicity levels and the impact of specific particles on human health.”

    The authors view these new findings as an opportunity to expand and iterate on the current guidelines.  

    “Routine and global measurements of the chemical composition of PM2.5 would give policymakers information on what interventions would most effectively improve air quality in any given location,” says Jesse Kroll, a professor in the MIT departments of Civil and Environmental Engineering and Chemical Engineering. “But it would also provide us with new insights into how different chemical species in PM2.5 affect human health.”

    “I hope that as we learn more about the health impacts of these different particles, our work and that of the broader atmospheric chemistry community can help inform strategies to reduce the pollutants that are most harmful to human health,” adds Heald. More