Aurelia Butler

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    in Environment

    Making agriculture more resilient to climate change

    As Earth’s temperature rises, agricultural practices will need to adapt. Droughts will likely become more frequent, and some land may no longer be arable. On top of that is the challenge of feeding an ever-growing population without expanding the production of fertilizer and other agrochemicals, which have a large carbon footprint that is contributing to the overall warming of the planet.Researchers across MIT are taking on these agricultural challenges from a variety of angles, from engineering plants that sound an alarm when they’re under stress to making seeds more resilient to drought. These types of technologies, and more yet to be devised, will be essential to feed the world’s population as the climate changes.“After water, the first thing we need is food. In terms of priority, there is water, food, and then everything else. As we are trying to find new strategies to support a world of 10 billion people, it will require us to invent new ways of making food,” says Benedetto Marelli, an associate professor of civil and environmental engineering at MIT.Marelli is the director of one of the six missions of the recently launched Climate Project at MIT, which focus on research areas such as decarbonizing industry and building resilient cities. Marelli directs the Wild Cards mission, which aims to identify unconventional solutions that are high-risk and high-reward.Drawing on expertise from a breadth of fields, MIT is well-positioned to tackle the challenges posed by climate change, Marelli says. “Bringing together our strengths across disciplines, including engineering, processing at scale, biological engineering, and infrastructure engineering, along with humanities, science, and economics, presents a great opportunity.”Protecting seeds from droughtMarelli, who began his career as a biomedical engineer working on regenerative medicine, is now developing ways to boost crop yields by helping seeds to survive and germinate during drought conditions, or in soil that has been depleted of nutrients. To achieve that, he has devised seed coatings, based on silk and other polymers, that can envelop and nourish seeds during the critical germination process.

    A new seed-coating process could facilitate agriculture on marginal arid lands by enabling the seeds to retain any available water.

    In healthy soil, plants have access to nitrogen, phosphates, and other nutrients that they need, many of which are supplied by microbes that live in the soil. However, in soil that has suffered from drought or overfarming, these nutrients are lacking. Marelli’s idea was to coat the seeds with a polymer that can be embedded with plant-growth-promoting bacteria that “fix” nitrogen by absorbing it from the air and making it available to plants. The microbes can also make other necessary nutrients available to plants.For the first generation of the seed coatings, he embedded these microbes in coatings made of silk — a material that he had previously shown can extend the shelf life of produce, meat, and other foods. In his lab at MIT, Marelli has shown that the seed coatings can help germinating plants survive drought, ultraviolet light exposure, and high salinity.Now, working with researchers at the Mohammed VI Polytechnic University in Morocco, he is adapting the approach to crops native to Morocco, a country that has experienced six consecutive years of drought due a drop in rainfall linked to climate change.For these studies, the researchers are using a biopolymer coating derived from food waste that can be easily obtained in Morocco, instead of silk.“We’re working with local communities to extract the biopolymers, to try to have a process that works at scale so that we make materials that work in that specific environment.” Marelli says. “We may come up with an idea here at MIT within a high-resource environment, but then to work there, we need to talk with the local communities, with local stakeholders, and use their own ingenuity and try to match our solution with something that could actually be applied in the local environment.”Microbes as fertilizersWhether they are experiencing drought or not, crops grow much better when synthetic fertilizers are applied. Although it’s essential to most farms, applying fertilizer is expensive and has environmental consequences. Most of the world’s fertilizer is produced using the Haber-Bosch process, which converts nitrogen and hydrogen to ammonia at high temperatures and pressures. This energy intensive process accounts for about 1.5 percent of the world’s greenhouse gas emissions, and the transportation required to deliver it to farms around the world adds even more emissions.Ariel Furst, the Paul M. Cook Career Development Assistant Professor of Chemical Engineering at MIT, is developing a microbial alternative to the Haber-Bosch process. Some farms have experimented with applying nitrogen-fixing bacteria directly to the roots of their crops, which has shown some success. However, the microbes are too delicate to be stored long-term or shipped anywhere, so they must be produced in a bioreactor on the farm.

    MIT chemical engineers devised a metal-organic coating that protects bacterial cells from damage without impeding their growth or function.

    To overcome those challenges, Furst has developed a way to coat the microbes with a protective shell that prevents them from being destroyed by heat or other stresses. The coating also protects microbes from damage caused by freeze-drying — a process that would make them easier to transport.The coatings can vary in composition, but they all consist of two components. One is a metal such as iron, manganese, or zinc, and the other is a polyphenol — a type of plant-derived organic compound that includes tannins and other antioxidants. These two components self-assemble into a protective shell that encapsulates bacteria.

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    Mighty Microbes: The Power of Protective PolymersVideo: Chemistry Shorts

    “These microbes would be delivered with the seeds, so it would remove the need for fertilizing mid-growing. It also reduces the cost and provides more autonomy to the farmers and decreases carbon emissions associated with agriculture,” Furst says. “We think it’ll be a way to make agriculture completely regenerative, so to bring back soil health while also boosting crop yields and the nutrient density of the crops.”Furst has founded a company called Seia Bio, which is working on commercializing the coated microbes and has begun testing them on farms in Brazil. In her lab, Furst is also working on adapting the approach to coat microbes that can capture carbon dioxide from the atmosphere and turn it into limestone, which helps to raise the soil pH.“It can help change the pH of soil to stabilize it, while also being a way to effectively perform direct air capture of CO2,” she says. “Right now, farmers may truck in limestone to change the pH of soil, and so you’re creating a lot of emissions to bring something in that microbes can do on their own.”Distress sensors for plantsSeveral years ago, Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT, began to explore the idea of using plants themselves as sensors that could reveal when they’re in distress. When plants experience drought, attack by pests, or other kinds of stress, they produce hormones and other signaling molecules to defend themselves.Strano, whose lab specializes in developing tiny sensors for a variety of molecules, wondered if such sensors could be deployed inside plants to pick up those distress signals. To create their sensors, Strano’s lab takes advantage of the special properties of single-walled carbon nanotubes, which emit fluorescent light. By wrapping the tubes with different types of polymers, the sensors can be tuned to detect specific targets, giving off a fluorescent signal when the target is present.For use in plants, Strano and his colleagues created sensors that could detect signaling molecules such as salicylic acid and hydrogen peroxide. They then showed that these sensors could be inserted into the underside of plant leaves, without harming the plants. Once embedded in the mesophyll of the leaves, the sensors can pick up a variety of signals, which can be read with an infrared camera.

    Sensors that detect plant signaling molecules can reveal when crops are experiencing too much light or heat, or attack from insects or microbes.

    These sensors can reveal, in real-time, whether a plant is experiencing a variety of stresses. Until now, there hasn’t been a way to get that information fast enough for farmers to act on it.“What we’re trying to do is make tools that get information into the hands of farmers very quickly, fast enough for them to make adaptive decisions that can increase yield,” Strano says. “We’re in the middle of a revolution of really understanding the way in which plants internally communicate and communicate with other plants.”This kind of sensing could be deployed in fields, where it could help farmers respond more quickly to drought and other stresses, or in greenhouses, vertical farms, and other types of indoor farms that use technology to grow crops in a controlled environment.Much of Strano’s work in this area has been conducted with the support of the U.S. Department of Agriculture (USDA) and as part of the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) program at the Singapore-MIT Alliance for Research and Technology (SMART), and sensors have been deployed in tests in crops at a controlled environment farm in Singapore called Growy.“The same basic kinds of tools can help detect problems in open field agriculture or in controlled environment agriculture,” Strano says. “They both suffer from the same problem, which is that the farmers get information too late to prevent yield loss.”Reducing pesticide usePesticides represent another huge financial expense for farmers: Worldwide, farmers spend about $60 billion per year on pesticides. Much of this pesticide ends up accumulating in water and soil, where it can harm many species, including humans. But, without using pesticides, farmers may lose more than half of their crops.Kripa Varanasi, an MIT professor of mechanical engineering, is working on tools that can help farmers measure how much pesticide is reaching their plants, as well as technologies that can help pesticides adhere to plants more efficiently, reducing the amount that runs off into soil and water.Varanasi, whose research focuses on interactions between liquid droplets and surfaces, began to think about applying his work to agriculture more than a decade ago, after attending a conference at the USDA. There, he was inspired to begin developing ways to improve the efficiency of pesticide application by optimizing the interactions that occur at leaf surfaces.“Billions of drops of pesticide are being sprayed on every acre of crop, and only a small fraction is ultimately reaching and staying on target. This seemed to me like a problem that we could help to solve,” he says.Varanasi and his students began exploring strategies to make drops of pesticide stick to leaves better, instead of bouncing off. They found that if they added polymers with positive and negative charges, the oppositely charged droplets would form a hydrophilic (water-attracting) coating on the leaf surface, which helps the next droplets applied to stick to the leaf.

    AgZen has developed a system for farming that can monitor exactly how much of the sprayed chemicals adheres to plants, in real time, as the sprayer drives through a field.

    Later, they developed an easier-to-use technology in which a surfactant is added to the pesticide before spraying. When this mixture is sprayed through a special nozzle, it forms tiny droplets that are “cloaked” in surfactant. The surfactant helps the droplets to stick to the leaves within a few milliseconds, without bouncing off.In 2020, Varanasi and Vishnu Jayaprakash SM ’19, PhD ’22 founded a company called AgZen to commercialize their technologies and get them into the hands of farmers. They incorporated their ideas for improving pesticide adhesion into a product called EnhanceCoverage.During the testing for this product, they realized that there weren’t any good ways to measure how many of the droplets were staying on the plant. That led them to develop a product known as RealCoverage, which is based on machine vision. It can be attached to any pesticide sprayer and offer real-time feedback on what percentage of the pesticide droplets are sticking to and staying on every leaf.RealCoverage was used on 65,000 acres of farmland across the United States in 2024, from soybeans in Iowa to cotton in Georgia. Farmers who used the product were able to reduce their pesticide use by 30 to 50 percent, by using the data to optimize delivery and, in some cases, even change what chemicals were sprayed.He hopes that the EnhanceCoverage product, which is expected to become available in 2025, will help farmers further reduce their pesticide use.“Our mission here is to help farmers with savings while helping them achieve better yields. We have found a way to do all this while also reducing waste and the amount of chemicals that we put into our atmosphere and into our soils and into our water,” Varanasi says. “This is the MIT approach: to figure out what are the real issues and how to come up with solutions. Now we have a tool and I hope that it’s deployed everywhere and everyone gets the benefit from it.” More

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    in Environment

    Oceanographers record the largest predation event ever observed in the ocean

    There is power in numbers, or so the saying goes. But in the ocean, scientists are finding that fish that group together don’t necessarily survive together. In some cases, the more fish there are, the larger a target they make for predators.This is what MIT and Norwegian oceanographers observed recently when they explored a wide swath of ocean off the coast of Norway during the height of spawning season for capelin — a small Arctic fish about the size of an anchovy. Billions of capelin migrate each February from the edge of the Arctic ice sheet southward to the Norwegian coast, to lay their eggs. Norway’s coastline is also a stopover for capelin’s primary predator, the Atlantic cod. As cod migrate south, they feed on spawning capelin, though scientists have not measured this process over large scales until now.Reporting their findings today in Nature Communications Biology, the MIT team captured interactions between individual migrating cod and spawning capelin, over a huge spatial extent. Using a sonic-based wide-area imaging technique, they watched as random capelin began grouping together to form a massive shoal spanning tens of kilometers. As the capelin shoal formed a sort of ecological “hotspot,” the team observed individual cod begin to group together in response, forming a huge shoal of their own. The swarming cod overtook the capelin, quickly consuming over 10 million fish, estimated to be more than half of the gathered prey.The dramatic encounter, which took place over just a few hours, is the largest such predation event ever recorded, both in terms of the number of individuals involved and the area over which the event occurred.This one event is unlikely to weaken the capelin population as a whole; the preyed-upon shoal represents 0.1 percent of the capelin that spawn in the region. However, as climate change causes the Arctic ice sheet to retreat, capelin will have to swim farther to spawn, making the species more stressed and vulnerable to natural predation events such as the one the team observed. As capelin sustains many fish species, including cod, continuously monitoring their behavior, at a resolution approaching that of individual fish and across large scales spanning tens of thousands of square kilometers, will help efforts to maintain the species and the health of the ocean overall.“In our work we are seeing that natural catastrophic predation events can change the local predator prey balance in a matter of hours,” says Nicholas Makris, professor of mechanical and ocean engineering at MIT. “That’s not an issue for a healthy population with many spatially distributed population centers or ecological hotspots. But as the number of these hotspots deceases due to climate and anthropogenic stresses, the kind of natural ‘catastrophic’ predation event we witnessed of a keystone species could lead to dramatic consequences for that species as well as the many species dependent on them.”Makris’ co-authors on the paper are Shourav Pednekar and Ankita Jain at MIT, and Olav Rune Godø of the Institute of Marine Research in Norway.Bell soundsFor their new study, Makris and his colleagues reanalyzed data that they gathered during a cruise in February of 2014 to the Barents Sea, off the coast of Norway. During that cruise, the team deployed the Ocean Acoustic Waveguide Remote Sensing (OAWRS) system — a sonic imaging technique that employs a vertical acoustic array, attached to the bottom of a boat, to send sound waves down into the ocean and out in all directions. These waves can travel over large distances as they bounce off any obstacles or fish in their path.The same or a second boat, towing an array of acoustic receivers, continuously picks up the scattered and reflected waves, from as far as many tens of kilometers away. Scientists can then analyze the collected waveforms to create instantaneous maps of the ocean over a huge areal extent.Previously, the team reconstructed maps of individual fish and their movements, but could not distinguish between different species. In the new study, the researchers applied a new “multispectral” technique to differentiate between species based on the characteristic acoustic resonance of their swim bladders.“Fish have swim bladders that resonate like bells,” Makris explains. “Cod have large swim bladders that have a low resonance, like a Big Ben bell, whereas capelin have tiny swim bladders that resonate like the highest notes on a piano.”By reanalyzing OAWRS data to look for specific frequencies of capelin versus cod, the researchers were able to image fish groups, determine their species content, and map the movements of each species over a huge areal extent.Watching a waveThe researchers applied the multi-spectral technique to OAWRS data collected on Feb. 27, 2014, at the peak of the capelin spawning season. In the early morning hours, their new mapping showed that capelin largely kept to themselves, moving as random individuals, in loose clusters along the Norwegian coastline. As the sun rose and lit the surface waters, the capelin began to descend to darker depths, possibly seeking places along the seafloor to spawn.The team observed that as the capelin descended, they began shifting from individual to group behavior, ultimately forming a huge shoal of about 23 million fish that moved in a coordinated wave spanning over ten kilometers long.“What we’re finding is capelin have this critical density, which came out of a physical theory, which we have now observed in the wild,” Makris says. “If they are close enough to each other, they can take on the average speed and direction of other fish that they can sense around them, and can then form a massive and coherent shoal.”As they watched, the shoaling fish began to move as one, in a coherent behavior that has been observed in other species but never in capelin until now. Such coherent migration is thought to help fish save energy over large distances by essentially riding the collective motion of the group.In this instance, however, as soon as the capelin shoal formed, it attracted increasing numbers of cod, which quickly formed a shoal of their own, amounting to about 2.5 million fish, based on the team’s acoustic mapping. Over a few short hours, the cod consumed 10.5 million capelin over tens of kilometers before both shoals dissolved and the fish scattered away. Makris suspects that such massive and coordinated predation is a common occurrence in the ocean, though this is the first time that scientists have been able to document such an event.“It’s the first time seeing predator-prey interaction on a huge scale, and it’s a coherent battle of survival,” Makris says. “This is happening over a monstrous scale, and we’re watching a wave of capelin zoom in, like a wave around a sports stadium, and they kind of gather together to form a defense. It’s also happening with the predators, coming together to coherently attack.”“This is a truly fascinating study that documents complex spatial dynamics linking predators and prey, here cod and capelin, at scales previously unachievable in marine ecosystems,” says George Rose, professor of fisheries at the University of British Columbia, who studies the ecology and productivity of cod in the North Atlantic, and was not involved in this work. “Simultaneous species mapping with the OAWRS system…enables insight into fundamental ecological processes with untold potential to enhance current survey methods.”Makris hopes to deploy OAWRS in the future to monitor the large-scale dynamics among other species of fish.“It’s been shown time and again that, when a population is on the verge of collapse, you will have that one last shoal. And when that last big, dense group is gone, there’s a collapse,” Makris says. “So you’ve got to know what’s there before it’s gone, because the pressures are not in their favor.”This work was supported, in part, by the U.S. Office of Naval Research and the Institute of Marine Research in Norway.  More

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    in Security

    Aspiring to sustainable development

    In a first for both universities, MIT undergraduates are engaged in research projects at the Universidad del Valle de Guatemala (UVG), while MIT scholars are collaborating with UVG undergraduates on in-depth field studies in Guatemala.These pilot projects are part of a larger enterprise, called ASPIRE (Achieving Sustainable Partnerships for Innovation, Research, and Entrepreneurship). Funded by the U.S. Agency for International Development, this five-year, $15-million initiative brings together MIT, UVG, and the Guatemalan Exporters Association to promote sustainable solutions to local development challenges.“This research is yielding insights into our understanding of how to design with and for marginalized people, specifically Indigenous people,” says Elizabeth Hoffecker, co-principal investigator of ASPIRE at MIT and director of the MIT Local Innovation Group.The students’ work is bearing fruit in the form of publications and new products — directly advancing ASPIRE’s goals to create an innovation ecosystem in Guatemala that can be replicated elsewhere in Central and Latin America.For the students, the project offers rewards both tangible and inspirational.“My experience allowed me to find my interest in local innovation and entrepreneurship,” says Ximena Sarmiento García, a fifth-year undergraduate at UVG majoring in anthropology. Supervised by Hoffecker, Sarmiento García says, “I learned how to inform myself, investigate, and find solutions — to become a researcher.”Sandra Youssef, a rising junior in mechanical engineering at MIT, collaborated with UVG researchers and Indigenous farmers to design a mobile cart to improve the harvest yield of snow peas. “It was perfect for me,” she says. “My goal was to use creative, new technologies and science to make a dent in difficult problems.”Remote and effectiveKendra Leith, co-principal investigator of ASPIRE, and associate director for research at MIT D-Lab, shaped the MIT-based undergraduate research opportunities (UROPs) in concert with UVG colleagues. “Although MIT students aren’t currently permitted to travel to Guatemala, I wanted them to have an opportunity to apply their experience and knowledge to address real-world challenges,” says Leith. “The Covid pandemic prepared them and their counterparts at UVG for effective remote collaboration — the UROPs completed remarkably productive research projects over Zoom and met our goals for them.”MIT students participated in some of UVG’s most ambitious ASPIRE research. For instance, Sydney Baller, a rising sophomore in mechanical engineering, joined a team of Indigenous farmers and UVG mechanical engineers investigating the manufacturing process and potential markets for essential oils extracted from thyme, rosemary, and chamomile plants.“Indigenous people have thousands of years working with plant extracts and ancient remedies,” says Baller. “There is promising history there that would be important to follow up with more modern research.”Sandra Youssef used computer-aided design and manufacturing to realize a design created in a hackathon by snow pea farmers. “Our cart had to hold 495 pounds of snow peas without collapsing or overturning, navigate narrow paths on hills, and be simple and inexpensive to assemble,” she says. The snow pea producers have tested two of Youssef’s designs, built by a team at UVG led by Rony Herrarte, a faculty member in the department of mechanical engineering.From waste to filterTwo MIT undergraduates joined one of UVG’s long-standing projects: addressing pollution in Guatemala’s water. The research seeks to use chitosan molecules, extracted from shrimp shells, for bioremediation of heavy metals and other water contaminants. These shells are available in abundance, left as waste by the country’s shrimp industry.Sophomores Ariana Hodlewsky, majoring in chemical engineering, and Paolo Mangiafico, majoring in brain and cognitive sciences, signed on to work with principal investigator and chemistry department instructor Allan Vásquez (UVG) on filtration systems utilizing chitosan.“The team wants to find a cost-effective product rural communities, most at risk from polluted water, can use in homes or in town water systems,” says Mangiafico. “So we have been investigating different technologies for water filtration, and analyzing the Guatemalan and U.S. markets to understand the regulations and opportunities that might affect introduction of a chitosan-based product.”“Our research into how different communities use water and into potential consumers and pitfalls sets the scene for prototypes UVG wants to produce,” says Hodlewsky.Lourdes Figueroa, UVG ASPIRE project manager for technology transfer, found their assistance invaluable.“Paolo and Ariana brought the MIT culture and mindset to the project,” she says. “They wanted to understand not only how the technology works, but the best ways of getting the technology out of the lab to make it useful.”This was an “Aha!” moment, says Figueroa. “The MIT students made a major contribution to both the engineering and marketing sides by emphasizing that you have to think about how to guarantee the market acceptance of the technology while it is still under development.”Innovation ecosystemsUVG’s three campuses have served as incubators for problem-solving innovation and entrepreneurship, in many cases driven by students from Indigenous communities and families. In 2022, Elizabeth Hoffecker, with eight UVG anthropology majors, set out to identify the most vibrant examples of these collaborative initiatives, which ASPIRE seeks to promote and replicate.Hoffecker’s “innovation ecosystem diagnostic” revealed a cluster of activity centered on UVG’s Altiplano campus in the central highlands, which serves Mayan communities. Hoffecker and two of the anthropology students focused on four examples for a series of case studies, which they are currently preparing for submission to a peer-reviewed journal.“The caliber of their work was so good that it became clear to me that we could collaborate on a paper,” says Hoffecker. “It was my first time publishing with undergraduates.”The researchers’ cases included novel production of traditional thread, and creation of a 3D phytoplankton kit that is being used to educate community members about water pollution in Lake Atitlán, a tourist destination that drives the local economy but is increasingly being affected by toxic algae blooms. Hoffecker singles out a project by Indigenous undergraduates who developed play-based teaching tools for introducing basic mathematical concepts.“These connect to local Mayan ways of understanding and offer a novel, hands-on way to strengthen the math teaching skills of local primary school teachers in Indigenous communities,” says Hoffecker. “They created something that addresses a very immediate need in the community — lack of training.Both of Hoffecker’s undergraduate collaborators are writing theses inspired by these case studies.“My time with Elizabeth allowed me to learn how to conduct research from scratch, ask for help, find solutions, and trust myself,” says Sarmiento García. She finds the ASPIRE approach profoundly appealing. “It is not only ethical, but also deeply committed to applying results to the real lives of the people involved.”“This experience has been incredibly positive, validating my own ability to generate knowledge through research, rather than relying only on established authors to back up my arguments,” says Camila del Cid, a fifth-year anthropology student. “This was empowering, especially as a Latin American researcher, because it emphasized that my perspective and contributions are important.”Hoffecker says this pilot run with UVG undergrads produced “high-quality research that can inform evidence-based decision-making on development issues of top regional priority” — a key goal for ASPIRE. Hoffecker plans to “develop a pathway that other UVG students can follow to conduct similar research.”MIT undergraduate research will continue. “Our students’ activities have been very valuable in Guatemala, so much so that the snow pea, chitosan, and essential oils teams would like to continue working with our students this year,” says Leith.  She anticipates a new round of MIT UROPs for next summer.Youssef, for one, is eager to get to work on refining the snow pea cart. “I like the idea of working outside my comfort zone, thinking about things that seem unsolvable and coming up with a solution to fix some aspect of the problem,” she says. More

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    in Environment

    Study: Marshes provide cost-effective coastal protection

    Images of coastal houses being carried off into the sea due to eroding coastlines and powerful storm surges are becoming more commonplace as climate change brings a rising sea level coupled with more powerful storms. In the U.S. alone, coastal storms caused $165 billion in losses in 2022.Now, a study from MIT shows that protecting and enhancing salt marshes in front of protective seawalls can significantly help protect some coastlines, at a cost that makes this approach reasonable to implement.The new findings are being reported in the journal Communications Earth and Environment, in a paper by MIT graduate student Ernie I. H. Lee and professor of civil and environmental engineering Heidi Nepf. This study, Nepf says, shows that restoring coastal marshes “is not just something that would be nice to do, but it’s actually economically justifiable.” The researchers found that, among other things, the wave-attenuating effects of salt marsh mean that the seawall behind it can be built significantly lower, reducing construction cost while still providing as much protection from storms.“One of the other exciting things that the study really brings to light,” Nepf says, “is that you don’t need a huge marsh to get a good effect. It could be a relatively short marsh, just tens of meters wide, that can give you benefit.” That makes her hopeful, Nepf says, that this information might be applied in places where planners may have thought saving a smaller marsh was not worth the expense. “We show that it can make enough of a difference to be financially viable,” she says.While other studies have previously shown the benefits of natural marshes in attenuating damaging storms, Lee says that such studies “mainly focus on landscapes that have a wide marsh on the order of hundreds of meters. But we want to show that it also applies in urban settings where not as much marsh land is available, especially since in these places existing gray infrastructure (seawalls) tends to already be in place.”The study was based on computer modeling of waves propagating over different shore profiles, using the morphology of various salt marsh plants — the height and stiffness of the plants, and their spatial density — rather than an empirical drag coefficient. “It’s a physically based model of plant-wave interaction, which allowed us to look at the influence of plant species and changes in morphology across seasons,” without having to go out and calibrate the vegetation drag coefficient with field measurements for each different condition, Nepf says.The researchers based their benefit-cost analysis on a simple metric: To protect a certain length of shoreline, how much could the height of a given seawall be reduced if it were accompanied by a given amount of marsh? Other ways of assessing the value, such as including the value of real estate that might be damaged by a given amount of flooding, “vary a lot depending on how you value the assets if a flood happens,” Lee says. “We use a more concrete value to quantify the benefits of salt marshes, which is the equivalent height of seawall you would need to deliver the same protection value.”They used models of a variety of plants, reflecting differences in height and the stiffness across different seasons. They found a twofold variation in the various plants’ effectiveness in attenuating waves, but all provided a useful benefit.To demonstrate the details in a real-world example and help to validate the simulations, Nepf and Lee studied local salt marshes in Salem, Massachusetts, where projects are already underway to try to restore marshes that had been degraded. Including the specific example provided a template for others, Nepf says. In Salem, their model showed that a healthy salt marsh could offset the need for an additional seawall height of 1.7 meters (about 5.5 feet), based on satisfying a rate of wave overtopping that was set for the safety of pedestrians.However, the real-world data needed to model a marsh, including maps of salt marsh species, plant height, and shoots per bed area, are “very labor-intensive” to put together, Nepf says. Lee is now developing a method to use drone imaging and machine learning to facilitate this mapmaking. Nepf says this will enable researchers or planners to evaluate a given area of marshland and say, “How much is this marsh worth in terms of its ability to reduce flooding?”The White House Office of Information and Regulatory Affairs recently released guidance for assessing the value of ecosystem services in planning of federal projects, Nepf explains.  “But in many scenarios, it lacks specific methods for quantifying value, and this study is meeting that need,” she says.The Federal Emergency Management Agency also has a benefit-cost analysis (BCA) toolkit, Lee notes. “They have guidelines on how to quantify each of the environmental services, and one of the novelties of this paper is quantifying the cost and the protection value of marshes. This is one of the applications that policymakers can consider on how to quantify the environmental service values of marshes,” he says.The software that environmental engineers can apply to specific sites has been made available online for free on GitHub. “It’s a one-dimensional model accessible by a standard consulting firm,” Nepf says.“This paper presents a practical tool for translating the wave attenuation capabilities of marshes into economic values, which could assist decision-makers in the adaptation of marshes for nature-based coastal defense,” says Xioaxia Zhang, a professor at Shenzen University in China who was not involved in this work. “The results indicate that salt marshes are not only environmentally beneficial but also cost-effective.”The study “is a very important and crucial step to quantifying the protective value of marshes,” adds Bas Borsje, an associate professor of nature-based flood protection at the University of Twente in the Netherlands, who was not associated with this work. “The most important step missing at the moment is how to translate our findings to the decision makers. This is the first time I’m aware of that decision-makers are quantitatively informed on the protection value of salt marshes.”Lee received support for this work from the Schoettler Scholarship Fund, administered by the MIT Department of Civil and Environmental Engineering. More

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    in Environment

    How climate change will impact outdoor activities in the US

    It can be hard to connect a certain amount of average global warming with one’s everyday experience, so researchers at MIT have devised a different approach to quantifying the direct impact of climate change. Instead of focusing on global averages, they came up with the concept of “outdoor days”: the number days per year in a given location when the temperature is not too hot or cold to enjoy normal outdoor activities, such as going for a walk, playing sports, working in the garden, or dining outdoors.In a study published earlier this year, the researchers applied this method to compare the impact of global climate change on different countries around the world, showing that much of the global south would suffer major losses in the number of outdoor days, while some northern countries could see a slight increase. Now, they have applied the same approach to comparing the outcomes for different parts of the United States, dividing the country into nine climatic regions, and finding similar results: Some states, especially Florida and other parts of the Southeast, should see a significant drop in outdoor days, while some, especially in the Northwest, should see a slight increase.The researchers also looked at correlations between economic activity, such as tourism trends, and changing climate conditions, and examined how numbers of outdoor days could result in significant social and economic impacts. Florida’s economy, for example, is highly dependent on tourism and on people moving there for its pleasant climate; a major drop in days when it is comfortable to spend time outdoors could make the state less of a draw.The new findings were published this month in the journal Geophysical Research Letters, in a paper by researchers Yeon-Woo Choi and Muhammad Khalifa and professor of civil and environmental engineering Elfatih Eltahir.“This is something very new in our attempt to understand impacts of climate change impact, in addition to the changing extremes,” Choi says. It allows people to see how these global changes may impact them on a very personal level, as opposed to focusing on global temperature changes or on extreme events such as powerful hurricanes or increased wildfires. “To the best of my knowledge, nobody else takes this same approach” in quantifying the local impacts of climate change, he says. “I hope that many others will parallel our approach to better understand how climate may affect our daily lives.”The study looked at two different climate scenarios — one where maximum efforts are made to curb global emissions of greenhouse gases and one “worst case” scenario where little is done and global warming continues to accelerate. They used these two scenarios with every available global climate model, 32 in all, and the results were broadly consistent across all 32 models.The reality may lie somewhere in between the two extremes that were modeled, Eltahir suggests. “I don’t think we’re going to act as aggressively” as the low-emissions scenarios suggest, he says, “and we may not be as careless” as the high-emissions scenario. “Maybe the reality will emerge in the middle, toward the end of the century,” he says.The team looked at the difference in temperatures and other conditions over various ranges of decades. The data already showed some slight differences in outdoor days from the 1961-1990 period compared to 1991-2020. The researchers then compared these most recent 30 years with the last 30 years of this century, as projected by the models, and found much greater differences ahead for some regions. The strongest effects in the modeling were seen in the Southeastern states. “It seems like climate change is going to have a significant impact on the Southeast in terms of reducing the number of outdoor days,” Eltahir says, “with implications for the quality of life of the population, and also for the attractiveness of tourism and for people who want to retire there.”He adds that “surprisingly, one of the regions that would benefit a little bit is the Northwest.” But the gain there is modest: an increase of about 14 percent in outdoor days projected for the last three decades of this century, compared to the period from 1976 to 2005. The Southwestern U.S., by comparison, faces an average loss of 23 percent of their outdoor days.The study also digs into the relationship between climate and economic activity by looking at tourism trends from U.S. National Park Service visitation data, and how that aligned with differences in climate conditions. “Accounting for seasonal variations, we find a clear connection between the number of outdoor days and the number of tourist visits in the United States,” Choi says.For much of the country, there will be little overall change in the total number of annual outdoor days, the study found, but the seasonal pattern of those days could change significantly. While most parts of the country now see the most outdoor days in summertime, that will shift as summers get hotter, and spring and fall will become the preferred seasons for outdoor activity.In a way, Eltahir says, “what we are talking about that will happen in the future [for most of the country] is already happening in Florida.” There, he says, “the really enjoyable time of year is in the spring and fall, and summer is not the best time of year.”People’s level of comfort with temperatures varies somewhat among individuals and among regions, so the researchers designed a tool, now freely available online, that allows people to set their own definitions of the lowest and highest temperatures they consider suitable for outdoor activities, and then see what the climate models predict would be the change in the number of outdoor days for their location, using their own standards of comfort. For their study, they used a widely accepted range of 10 degrees Celsius (50 degrees Fahrenheit) to 25 C (77 F), which is the “thermoneutral zone” in which the human body does not require either metabolic heat generation or evaporative cooling to maintain its core temperature — in other words, in that range there is generally no need to either shiver or sweat.The model mainly focuses on temperature but also allows people to include humidity or precipitation in their definition of what constitutes a comfortable outdoor day. The model could be extended to incorporate other variables such as air quality, but the researchers say temperature tends to be the major determinant of comfort for most people.Using their software tool, “If you disagree with how we define an outdoor day, you could define one for yourself, and then you’ll see what the impacts of that are on your number of outdoor days and their seasonality,” Eltahir says.This work was inspired by the realization, he says, that “people’s understanding of climate change is based on the assumption that climate change is something that’s going to happen sometime in the future and going to happen to someone else. It’s not going to impact them directly. And I think that contributes to the fact that we are not doing enough.”Instead, the concept of outdoor days “brings the concept of climate change home, brings it to personal everyday activities,” he says. “I hope that people will find that useful to bridge that gap, and provide a better understanding and appreciation of the problem. And hopefully that would help lead to sound policies that are based on science, regarding climate change.”The research was based on work supported by the Community Jameel for Jameel Observatory CREWSnet and Abdul Latif Jameel Water and Food Systems Lab at MIT. More

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    in Security

    Uplifting West African communities, one cashew at a time

    Ever wonder how your favorite snack was sourced? Joshua Reed-Diawuoh thinks more people should.Reed-Diawuoh MBA ’20 is the founder and CEO of GRIA Food Company, which partners with companies that ethically source and process food in West Africa to support local food economies and help communities in the region more broadly.“It’s very difficult for these agribusinesses and producers to start sustainable businesses and build up that value chain in the area,” says Reed-Diawuoh, who started the company as a student in the MIT Sloan School of Management. “We want to support these companies that put in the work to build integrated businesses that are employing people and uplifting communities.”GRIA, which stands for “Grown in Africa,” is currently selling six types of flavored cashews sourced from Benin, Togo, and Burkina Faso. All of the cashews are certified by Fairtrade International, which means in addition to offering sustainable wages, access to financing, and decent working conditions, the companies receive a “Fairtrade Premium” on top of the selling price that allows them to invest in the long-term health of their communities.“That premium is transformational,” Reed-Diawuoh says. “The premium goes to the producer cooperatives, or the farmers working the land, and they can invest that in any way they choose. They can put it back into their business, they can start new community development projects, like building schools or improving wastewater infrastructure, whatever they want.”Cracking the nutReed-Diawuoh’s family is from Ghana, and before coming to MIT Sloan, he worked to support agriculture and food manufacturing for countries in Sub-Saharan Africa, with particular focus on uplifting small-scale farmers. That’s where he learned about difficulties with financing and infrastructure constraints that held many companies back.“I wanted to get my hands dirty and start my own business that contributed to improving agricultural development in West Africa,” Reed-Diawuoh says.He entered MIT Sloan in 2018, taking entrepreneurship classes and exploring several business ideas before deciding to ethically source produce from farmers and sell directly to consumers. He says MIT Sloan’s Sustainability Business Lab offered particularly valuable lessons for how to structure his business.In his second year, Reed-Diawuoh was selected for a fellowship at the Legatum Center, which connected him to other entrepreneurs working in emerging markets around the world.“Legatum was a pivotal milestone for me,” he says. “It provided me with some structure and space to develop this idea. It also gave me an incredible opportunity to take risks and explore different business concepts in a way I couldn’t have done if I was working in industry.”The business model Reed-Diawuoh settled on for GRIA sources product from agribusiness partners in West Africa that adhere to the strictest environmental and labor standards. Reed-Diawuoh decided to start with cashews because they have many manual processing steps — from shelling to peeling and roasting — that are often done after the cashews are shipped out of West Africa, limiting the growth of local food economies and taking wealth out of communities.Each of GRIA’s partners, from the companies harvesting cashews to the processing facilities, works directly with farmer cooperatives and small-scale farmers and is certified by Fairtrade International.“Without proper oversight and regulations, workers oftentimes get exploited, and child labor is a huge problem across the agriculture sector,” Reed-Diawuoh says. “Fairtrade certifications try and take a robust and rigorous approach to auditing all of the businesses and their supply chains, from producers to farmers to processors. They do on-site visits and they audit financial documents. We went through this over the course of a thorough three-month review.”After importing cashew kernels, GRIA flavors and packages them at a production facility in Boston. Reed-Diawuoh started by selling to small independent retailers in Greater Boston before scaling up GRIA’s online sales. He started ramping up production in the beginning of 2023.“Every time we sell our product, if people weren’t already familiar with Fairtrade or ethical sourcing, we provide information on our packaging and all of our collateral,” Reed-Diawuoh says. “We want to spread this message about the importance of ethical sourcing and the importance of building up food manufacturing in West Africa in particular, but also in rising economies throughout the world.”Making ethical sourcing mainstreamGRIA currently imports about a ton of Fairtrade cashews and kernels each quarter, and Reed-Diawuoh hopes to double that number each year for the foreseeable future.“For each pound, we pay premiums for the kernels, and that supports this ecosystem where producers get compensated fairly for their work on the land, and agribusinesses are able to build more robust and profitable business models, because they have an end market for these Fairtrade-certified products.”Reed-Diawuoh is currently trying out different packaging and flavors and is in discussions with partners to expand production capacity and move into Ghana. He’s also exploring corporate collaborations and has provided MIT with product over the past two years for conferences and other events.“We’re experimenting with different growth strategies,” Reed-Diawuoh says. “We’re very much still in startup mode, but really trying to ramp up our sales and production.”As GRIA scales, Reed-Diawuoh hopes it pushes consumers to start asking more of their favorite food brands.“It’s absolutely critical that, if we’re sourcing produce in markets like the U.S. from places like West Africa, we’re hyper-focused on doing it in an ethical manner,” Reed-Diawuoh says. “The overall goal of GRIA is to ensure we are adhering to and promoting strict sourcing standards and being rigorous and thoughtful about the way we import product.” More

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    in Environment

    Study finds mercury pollution from human activities is declining

    MIT researchers have some good environmental news: Mercury emissions from human activity have been declining over the past two decades, despite global emissions inventories that indicate otherwise.In a new study, the researchers analyzed measurements from all available monitoring stations in the Northern Hemisphere and found that atmospheric concentrations of mercury declined by about 10 percent between 2005 and 2020.They used two separate modeling methods to determine what is driving that trend. Both techniques pointed to a decline in mercury emissions from human activity as the most likely cause.Global inventories, on the other hand, have reported opposite trends. These inventories estimate atmospheric emissions using models that incorporate average emission rates of polluting activities and the scale of these activities worldwide.“Our work shows that it is very important to learn from actual, on-the-ground data to try and improve our models and these emissions estimates. This is very relevant for policy because, if we are not able to accurately estimate past mercury emissions, how are we going to predict how mercury pollution will evolve in the future?” says Ari Feinberg, a former postdoc in the Institute for Data, Systems, and Society (IDSS) and lead author of the study.The new results could help inform scientists who are embarking on a collaborative, global effort to evaluate pollution models and develop a more in-depth understanding of what drives global atmospheric concentrations of mercury.However, due to a lack of data from global monitoring stations and limitations in the scientific understanding of mercury pollution, the researchers couldn’t pinpoint a definitive reason for the mismatch between the inventories and the recorded measurements.“It seems like mercury emissions are moving in the right direction, and could continue to do so, which is heartening to see. But this was as far as we could get with mercury. We need to keep measuring and advancing the science,” adds co-author Noelle Selin, an MIT professor in the IDSS and the Department of Earth, Atmospheric and Planetary Sciences (EAPS).Feinberg and Selin, his MIT postdoctoral advisor, are joined on the paper by an international team of researchers that contributed atmospheric mercury measurement data and statistical methods to the study. The research appears this week in the Proceedings of the National Academy of Sciences.Mercury mismatchThe Minamata Convention is a global treaty that aims to cut human-caused emissions of mercury, a potent neurotoxin that enters the atmosphere from sources like coal-fired power plants and small-scale gold mining.The treaty, which was signed in 2013 and went into force in 2017, is evaluated every five years. The first meeting of its conference of parties coincided with disheartening news reports that said global inventories of mercury emissions, compiled in part from information from national inventories, had increased despite international efforts to reduce them.This was puzzling news for environmental scientists like Selin. Data from monitoring stations showed atmospheric mercury concentrations declining during the same period.Bottom-up inventories combine emission factors, such as the amount of mercury that enters the atmosphere when coal mined in a certain region is burned, with estimates of pollution-causing activities, like how much of that coal is burned in power plants.“The big question we wanted to answer was: What is actually happening to mercury in the atmosphere and what does that say about anthropogenic emissions over time?” Selin says.Modeling mercury emissions is especially tricky. First, mercury is the only metal that is in liquid form at room temperature, so it has unique properties. Moreover, mercury that has been removed from the atmosphere by sinks like the ocean or land can be re-emitted later, making it hard to identify primary emission sources.At the same time, mercury is more difficult to study in laboratory settings than many other air pollutants, especially due to its toxicity, so scientists have limited understanding of all chemical reactions mercury can undergo. There is also a much smaller network of mercury monitoring stations, compared to other polluting gases like methane and nitrous oxide.“One of the challenges of our study was to come up with statistical methods that can address those data gaps, because available measurements come from different time periods and different measurement networks,” Feinberg says.Multifaceted modelsThe researchers compiled data from 51 stations in the Northern Hemisphere. They used statistical techniques to aggregate data from nearby stations, which helped them overcome data gaps and evaluate regional trends.By combining data from 11 regions, their analysis indicated that Northern Hemisphere atmospheric mercury concentrations declined by about 10 percent between 2005 and 2020.Then the researchers used two modeling methods — biogeochemical box modeling and chemical transport modeling — to explore possible causes of that decline.  Box modeling was used to run hundreds of thousands of simulations to evaluate a wide array of emission scenarios. Chemical transport modeling is more computationally expensive but enables researchers to assess the impacts of meteorology and spatial variations on trends in selected scenarios.For instance, they tested one hypothesis that there may be an additional environmental sink that is removing more mercury from the atmosphere than previously thought. The models would indicate the feasibility of an unknown sink of that magnitude.“As we went through each hypothesis systematically, we were pretty surprised that we could really point to declines in anthropogenic emissions as being the most likely cause,” Selin says.Their work underscores the importance of long-term mercury monitoring stations, Feinberg adds. Many stations the researchers evaluated are no longer operational because of a lack of funding.While their analysis couldn’t zero in on exactly why the emissions inventories didn’t match up with actual data, they have a few hypotheses.One possibility is that global inventories are missing key information from certain countries. For instance, the researchers resolved some discrepancies when they used a more detailed regional inventory from China. But there was still a gap between observations and estimates.They also suspect the discrepancy might be the result of changes in two large sources of mercury that are particularly uncertain: emissions from small-scale gold mining and mercury-containing products.Small-scale gold mining involves using mercury to extract gold from soil and is often performed in remote parts of developing countries, making it hard to estimate. Yet small-scale gold mining contributes about 40 percent of human-made emissions.In addition, it’s difficult to determine how long it takes the pollutant to be released into the atmosphere from discarded products like thermometers or scientific equipment.“We’re not there yet where we can really pinpoint which source is responsible for this discrepancy,” Feinberg says.In the future, researchers from multiple countries, including MIT, will collaborate to study and improve the models they use to estimate and evaluate emissions. This research will be influential in helping that project move the needle on monitoring mercury, he says.This research was funded by the Swiss National Science Foundation, the U.S. National Science Foundation, and the U.S. Environmental Protection Agency. More

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    in Environment

    Bubble findings could unlock better electrode and electrolyzer designs

    Industrial electrochemical processes that use electrodes to produce fuels and chemical products are hampered by the formation of bubbles that block parts of the electrode surface, reducing the area available for the active reaction. Such blockage reduces the performance of the electrodes by anywhere from 10 to 25 percent.But new research reveals a decades-long misunderstanding about the extent of that interference. The findings show exactly how the blocking effect works and could lead to new ways of designing electrode surfaces to minimize inefficiencies in these widely used electrochemical processes.It has long been assumed that the entire area of the electrode shadowed by each bubble would be effectively inactivated. But it turns out that a much smaller area — roughly the area where the bubble actually contacts the surface — is blocked from its electrochemical activity. The new insights could lead directly to new ways of patterning the surfaces to minimize the contact area and improve overall efficiency.The findings are reported today in the journal Nanoscale, in a paper by recent MIT graduate Jack Lake PhD ’23, graduate student Simon Rufer, professor of mechanical engineering Kripa Varanasi, research scientist Ben Blaiszik, and six others at the University of Chicago and Argonne National Laboratory. The team has made available an open-source, AI-based software tool that engineers and scientists can now use to automatically recognize and quantify bubbles formed on a given surface, as a first step toward controlling the electrode material’s properties.

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    Gas-evolving electrodes, often with catalytic surfaces that promote chemical reactions, are used in a wide variety of processes, including the production of “green” hydrogen without the use of fossil fuels, carbon-capture processes that can reduce greenhouse gas emissions, aluminum production, and the chlor-alkali process that is used to make widely used chemical products.These are very widespread processes. The chlor-alkali process alone accounts for 2 percent of all U.S. electricity usage; aluminum production accounts for 3 percent of global electricity; and both carbon capture and hydrogen production are likely to grow rapidly in coming years as the world strives to meet greenhouse-gas reduction targets. So, the new findings could make a real difference, Varanasi says.“Our work demonstrates that engineering the contact and growth of bubbles on electrodes can have dramatic effects” on how bubbles form and how they leave the surface, he says. “The knowledge that the area under bubbles can be significantly active ushers in a new set of design rules for high-performance electrodes to avoid the deleterious effects of bubbles.”“The broader literature built over the last couple of decades has suggested that not only that small area of contact but the entire area under the bubble is passivated,” Rufer says. The new study reveals “a significant difference between the two models because it changes how you would develop and design an electrode to minimize these losses.”To test and demonstrate the implications of this effect, the team produced different versions of electrode surfaces with patterns of dots that nucleated and trapped bubbles at different sizes and spacings. They were able to show that surfaces with widely spaced dots promoted large bubble sizes but only tiny areas of surface contact, which helped to make clear the difference between the expected and actual effects of bubble coverage.Developing the software to detect and quantify bubble formation was necessary for the team’s analysis, Rufer explains. “We wanted to collect a lot of data and look at a lot of different electrodes and different reactions and different bubbles, and they all look slightly different,” he says. Creating a program that could deal with different materials and different lighting and reliably identify and track the bubbles was a tricky process, and machine learning was key to making it work, he says.Using that tool, he says, they were able to collect “really significant amounts of data about the bubbles on a surface, where they are, how big they are, how fast they’re growing, all these different things.” The tool is now freely available for anyone to use via the GitHub repository.By using that tool to correlate the visual measures of bubble formation and evolution with electrical measurements of the electrode’s performance, the researchers were able to disprove the accepted theory and to show that only the area of direct contact is affected. Videos further proved the point, revealing new bubbles actively evolving directly under parts of a larger bubble.The researchers developed a very general methodology that can be applied to characterize and understand the impact of bubbles on any electrode or catalyst surface. They were able to quantify the bubble passivation effects in a new performance metric they call BECSA (Bubble-induced electrochemically active surface), as opposed to ECSA (electrochemically active surface area), that is used in the field. “The BECSA metric was a concept we defined in an earlier study but did not have an effective method to estimate until this work,” says Varanasi.The knowledge that the area under bubbles can be significantly active ushers in a new set of design rules for high-performance electrodes. This means that electrode designers should seek to minimize bubble contact area rather than simply bubble coverage, which can be achieved by controlling the morphology and chemistry of the electrodes. Surfaces engineered to control bubbles can not only improve the overall efficiency of the processes and thus reduce energy use, they can also save on upfront materials costs. Many of these gas-evolving electrodes are coated with catalysts made of expensive metals like platinum or iridium, and the findings from this work can be used to engineer electrodes to reduce material wasted by reaction-blocking bubbles.Varanasi says that “the insights from this work could inspire new electrode architectures that not only reduce the usage of precious materials, but also improve the overall electrolyzer performance,” both of which would provide large-scale environmental benefits.The research team included Jim James, Nathan Pruyne, Aristana Scourtas, Marcus Schwarting, Aadit Ambalkar, Ian Foster, and Ben Blaiszik at the University of Chicago and Argonne National Laboratory. The work was supported by the U.S. Department of Energy under the ARPA-E program. More