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    Study: Burning heavy fuel oil with scrubbers is the best available option for bulk maritime shipping

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    When the International Maritime Organization enacted a mandatory cap on the sulfur content of marine fuels in 2020, with an eye toward reducing harmful environmental and health impacts, it left shipping companies with three main options.They could burn low-sulfur fossil fuels, like marine gas oil, or install cleaning systems to remove sulfur from the exhaust gas produced by burning heavy fuel oil. Biofuels with lower sulfur content offer another alternative, though their limited availability makes them a less feasible option.While installing exhaust gas cleaning systems, known as scrubbers, is the most feasible and cost-effective option, there has been a great deal of uncertainty among firms, policymakers, and scientists as to how “green” these scrubbers are.Through a novel lifecycle assessment, researchers from MIT, Georgia Tech, and elsewhere have now found that burning heavy fuel oil with scrubbers in the open ocean can match or surpass using low-sulfur fuels, when a wide variety of environmental factors is considered.The scientists combined data on the production and operation of scrubbers and fuels with emissions measurements taken onboard an oceangoing cargo ship.They found that, when the entire supply chain is considered, burning heavy fuel oil with scrubbers was the least harmful option in terms of nearly all 10 environmental impact factors they studied, such as greenhouse gas emissions, terrestrial acidification, and ozone formation.“In our collaboration with Oldendorff Carriers to broadly explore reducing the environmental impact of shipping, this study of scrubbers turned out to be an unexpectedly deep and important transitional issue,” says Neil Gershenfeld, an MIT professor, director of the Center for Bits and Atoms (CBA), and senior author of the study.“Claims about environmental hazards and policies to mitigate them should be backed by science. You need to see the data, be objective, and design studies that take into account the full picture to be able to compare different options from an apples-to-apples perspective,” adds lead author Patricia Stathatou, an assistant professor at Georgia Tech, who began this study as a postdoc in the CBA.Stathatou is joined on the paper by Michael Triantafyllou, the Henry L. and Grace Doherty and others at the National Technical University of Athens in Greece and the maritime shipping firm Oldendorff Carriers. The research appears today in Environmental Science and Technology.Slashing sulfur emissionsHeavy fuel oil, traditionally burned by bulk carriers that make up about 30 percent of the global maritime fleet, usually has a sulfur content around 2 to 3 percent. This is far higher than the International Maritime Organization’s 2020 cap of 0.5 percent in most areas of the ocean and 0.1 percent in areas near population centers or environmentally sensitive regions.Sulfur oxide emissions contribute to air pollution and acid rain, and can damage the human respiratory system.In 2018, fewer than 1,000 vessels employed scrubbers. After the cap went into place, higher prices of low-sulfur fossil fuels and limited availability of alternative fuels led many firms to install scrubbers so they could keep burning heavy fuel oil.Today, more than 5,800 vessels utilize scrubbers, the majority of which are wet, open-loop scrubbers.“Scrubbers are a very mature technology. They have traditionally been used for decades in land-based applications like power plants to remove pollutants,” Stathatou says.A wet, open-loop marine scrubber is a huge, metal, vertical tank installed in a ship’s exhaust stack, above the engines. Inside, seawater drawn from the ocean is sprayed through a series of nozzles downward to wash the hot exhaust gases as they exit the engines.The seawater interacts with sulfur dioxide in the exhaust, converting it to sulfates — water-soluble, environmentally benign compounds that naturally occur in seawater. The washwater is released back into the ocean, while the cleaned exhaust escapes to the atmosphere with little to no sulfur dioxide emissions.But the acidic washwater can contain other combustion byproducts like heavy metals, so scientists wondered if scrubbers were comparable, from a holistic environmental point of view, to burning low-sulfur fuels.Several studies explored toxicity of washwater and fuel system pollution, but none painted a full picture.The researchers set out to fill that scientific gap.A “well-to-wake” analysisThe team conducted a lifecycle assessment using a global environmental database on production and transport of fossil fuels, such as heavy fuel oil, marine gas oil, and very-low sulfur fuel oil. Considering the entire lifecycle of each fuel is key, since producing low-sulfur fuel requires extra processing steps in the refinery, causing additional emissions of greenhouse gases and particulate matter.“If we just look at everything that happens before the fuel is bunkered onboard the vessel, heavy fuel oil is significantly more low-impact, environmentally, than low-sulfur fuels,” she says.The researchers also collaborated with a scrubber manufacturer to obtain detailed information on all materials, production processes, and transportation steps involved in marine scrubber fabrication and installation.“If you consider that the scrubber has a lifetime of about 20 years, the environmental impacts of producing the scrubber over its lifetime are negligible compared to producing heavy fuel oil,” she adds.For the final piece, Stathatou spent a week onboard a bulk carrier vessel in China to measure emissions and gather seawater and washwater samples. The ship burned heavy fuel oil with a scrubber and low-sulfur fuels under similar ocean conditions and engine settings.Collecting these onboard data was the most challenging part of the study.“All the safety gear, combined with the heat and the noise from the engines on a moving ship, was very overwhelming,” she says.Their results showed that scrubbers reduce sulfur dioxide emissions by 97 percent, putting heavy fuel oil on par with low-sulfur fuels according to that measure. The researchers saw similar trends for emissions of other pollutants like carbon monoxide and nitrous oxide.In addition, they tested washwater samples for more than 60 chemical parameters, including nitrogen, phosphorus, polycyclic aromatic hydrocarbons, and 23 metals.The concentrations of chemicals regulated by the IMO were far below the organization’s requirements. For unregulated chemicals, the researchers compared the concentrations to the strictest limits for industrial effluents from the U.S. Environmental Protection Agency and European Union.Most chemical concentrations were at least an order of magnitude below these requirements.In addition, since washwater is diluted thousands of times as it is dispersed by a moving vessel, the concentrations of such chemicals would be even lower in the open ocean.These findings suggest that the use of scrubbers with heavy fuel oil can be considered as equal to or more environmentally friendly than low-sulfur fuels across many of the impact categories the researchers studied.“This study demonstrates the scientific complexity of the waste stream of scrubbers. Having finally conducted a multiyear, comprehensive, and peer-reviewed study, commonly held fears and assumptions are now put to rest,” says Scott Bergeron, managing director at Oldendorff Carriers and co-author of the study.“This first-of-its-kind study on a well-to-wake basis provides very valuable input to ongoing discussion at the IMO,” adds Thomas Klenum, executive vice president of innovation and regulatory affairs at the Liberian Registry, emphasizing the need “for regulatory decisions to be made based on scientific studies providing factual data and conclusions.”Ultimately, this study shows the importance of incorporating lifecycle assessments into future environmental impact reduction policies, Stathatou says.“There is all this discussion about switching to alternative fuels in the future, but how green are these fuels? We must do our due diligence to compare them equally with existing solutions to see the costs and benefits,” she adds.This study was supported, in part, by Oldendorff Carriers. More

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      Surprise discovery could lead to improved catalysts for industrial reactions

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      The process of catalysis — in which a material speeds up a chemical reaction — is crucial to the production of many of the chemicals used in our everyday lives. But even though these catalytic processes are widespread, researchers often lack a clear understanding of exactly how they work.A new analysis by researchers at MIT has shown that an important industrial synthesis process, the production of vinyl acetate, requires a catalyst to take two different forms, which cycle back and forth from one to the other as the chemical process unfolds.Previously, it had been thought that only one of the two forms was needed. The new findings are published today in the journal Science, in a paper by MIT graduate students Deiaa Harraz and Kunal Lodaya, Bryan Tang PhD ’23, and MIT professor of chemistry and chemical engineering Yogesh Surendranath.There are two broad classes of catalysts: homogeneous catalysts, which consist of dissolved molecules, and heterogeneous catalysts, which are solid materials whose surface provides the site for the chemical reaction. “For the longest time,” Surendranath says, “there’s been a general view that you either have catalysis happening on these surfaces, or you have them happening on these soluble molecules.” But the new research shows that in the case of vinyl acetate — an important material that goes into many polymer products such as the rubber in the soles of your shoes — there is an interplay between both classes of catalysis.“What we discovered,” Surendranath explains, “is that you actually have these solid metal materials converting into molecules, and then converting back into materials, in a cyclic dance.”He adds: “This work calls into question this paradigm where there’s either one flavor of catalysis or another. Really, there could be an interplay between both of them in certain cases, and that could be really advantageous for having a process that’s selective and efficient.”The synthesis of vinyl acetate has been a large-scale industrial reaction since the 1960s, and it has been well-researched and refined over the years to improve efficiency. This has happened largely through a trial-and-error approach, without a precise understanding of the underlying mechanisms, the researchers say.While chemists are often more familiar with homogeneous catalysis mechanisms, and chemical engineers are often more familiar with surface catalysis mechanisms, fewer researchers study both. This is perhaps part of the reason that the full complexity of this reaction was not previously captured. But Harraz says he and his colleagues are working at the interface between disciplines. “We’ve been able to appreciate both sides of this reaction and find that both types of catalysis are critical,” he says.The reaction that produces vinyl acetate requires something to activate the oxygen molecules that are one of the constituents of the reaction, and something else to activate the other ingredients, acetic acid and ethylene. The researchers found that the form of the catalyst that worked best for one part of the process was not the best for the other. It turns out that the molecular form of the catalyst does the key chemistry with the ethylene and the acetic acid, while it’s the surface that ends up doing the activation of the oxygen.They found that the underlying process involved in interconverting the two forms of the catalyst is actually corrosion, similar to the process of rusting. “It turns out that in rusting, you actually go through a soluble molecular species somewhere in the sequence,” Surendranath says.The team borrowed techniques traditionally used in corrosion research to study the process. They used electrochemical tools to study the reaction, even though the overall reaction does not require a supply of electricity. By making potential measurements, the researchers determined that the corrosion of the palladium catalyst material to soluble palladium ions is driven by an electrochemical reaction with the oxygen, converting it to water. Corrosion is “one of the oldest topics in electrochemistry,” says Lodaya, “but applying the science of corrosion to understand catalysis is much newer, and was essential to our findings.”By correlating measurements of catalyst corrosion with other measurements of the chemical reaction taking place, the researchers proposed that it was the corrosion rate that was limiting the overall reaction. “That’s the choke point that’s controlling the rate of the overall process,” Surendranath says.The interplay between the two types of catalysis works efficiently and selectively “because it actually uses the synergy of a material surface doing what it’s good at and a molecule doing what it’s good at,” Surendranath says. The finding suggests that, when designing new catalysts, rather than focusing on either solid materials or soluble molecules alone, researchers should think about how the interplay of both may open up new approaches.“Now, with an improved understanding of what makes this catalyst so effective, you can try to design specific materials or specific interfaces that promote the desired chemistry,” Harraz says. Since this process has been worked on for so long, these findings may not necessarily lead to improvements in this specific process of making vinyl acetate, but it does provide a better understanding of why the materials work as they do, and could lead to improvements in other catalytic processes.Understanding that “catalysts can transit between molecule and material and back, and the role that electrochemistry plays in those transformations, is a concept that we are really excited to expand on,” Lodaya says.Harraz adds: “With this new understanding that both types of catalysis could play a role, what other catalytic processes are out there that actually involve both? Maybe those have a lot of room for improvement that could benefit from this understanding.”This work is “illuminating, something that will be worth teaching at the undergraduate level,” says Christophe Coperet, a professor of inorganic chemistry at ETH Zurich, who was not associated with the research. “The work highlights new ways of thinking. … [It] is notable in the sense that it not only reconciles homogeneous and heterogeneous catalysis, but it describes these complex processes as half reactions, where electron transfers can cycle between distinct entities.”The research was supported, in part, by the National Science Foundation as a Phase I Center for Chemical Innovation; the Center for Interfacial Ionics; and the Gordon and Betty Moore Foundation. More

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      Collaboration between MIT and GE Vernova aims to develop and scale sustainable energy systems

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      MIT and GE Vernova today announced the creation of the MIT-GE Vernova Energy and Climate Alliance to help develop and scale sustainable energy systems across the globe.The alliance launches a five-year collaboration between MIT and GE Vernova, a global energy company that spun off from General Electric’s energy business in 2024. The endeavor will encompass research, education, and career opportunities for students, faculty, and staff across MIT’s five schools and the MIT Schwarzman College of Computing. It will focus on three main themes: decarbonization, electrification, and renewables acceleration.“This alliance will provide MIT students and researchers with a tremendous opportunity to work on energy solutions that could have real-world impact,” says Anantha Chandrakasan, MIT’s chief innovation and strategy officer and dean of the School of Engineering. “GE Vernova brings domain knowledge and expertise deploying these at scale. When our researchers develop new innovative technologies, GE Vernova is strongly positioned to bring them to global markets.”Through the alliance, GE Vernova is sponsoring research projects at MIT and providing philanthropic support for MIT research fellowships. The company will also engage with MIT’s community through participation in corporate membership programs and professional education.“It’s a privilege to combine forces with MIT’s world-class faculty and students as we work together to realize an optimistic, innovation-driven approach to solving the world’s most pressing challenges,” says Scott Strazik, GE Vernova CEO. “Through this alliance, we are proud to be able to help drive new technologies while at the same time inspire future leaders to play a meaningful role in deploying technology to improve the planet at companies like GE Vernova.”“This alliance embodies the spirit of the MIT Climate Project — combining cutting-edge research, a shared drive to tackle today’s toughest energy challenges, and a deep sense of optimism about what we can achieve together,” says Sally Kornbluth, president of MIT. “With the combined strengths of MIT and GE Vernova, we have a unique opportunity to make transformative progress in the flagship areas of electrification, decarbonization, and renewables acceleration.”The alliance, comprising a $50 million commitment, will operate within MIT’s Office of Innovation and Strategy. It will fund approximately 12 annual research projects relating to the three themes, as well as three master’s student projects in MIT’s Technology and Policy Program. The research projects will address challenges like developing and storing clean energy, as well as the creation of robust system architectures that help sustainable energy sources like solar, wind, advanced nuclear reactors, green hydrogen, and more compete with carbon-emitting sources.The projects will be selected by a joint steering committee composed of representatives from MIT and GE Vernova, following an annual Institute-wide call for proposals.The collaboration will also create approximately eight endowed GE Vernova research fellowships for MIT students, to be selected by faculty and beginning in the fall. There will also be 10 student internships that will span GE Vernova’s global operations, and GE Vernova will also sponsor programming through MIT’s New Engineering Education Transformation (NEET), which equips students with career-oriented experiential opportunities. Additionally, the alliance will create professional education programming for GE Vernova employees.“The internships and fellowships will be designed to bring students into our ecosystem,” says GE Vernova Chief Corporate Affairs Officer Roger Martella. “Students will walk our factory floor, come to our labs, be a part of our management teams, and see how we operate as business leaders. They’ll get a sense for how what they’re learning in the classroom is being applied in the real world.”Philanthropic support from GE Vernova will also support projects in MIT’s Human Insight Collaborative (MITHIC), which launched last fall to elevate human-centered research and teaching. The projects will allow faculty to explore how areas like energy and cybersecurity influence human behavior and experiences.In connection with the alliance, GE Vernova is expected to join several MIT consortia and membership programs, helping foster collaborations and dialogue between industry experts and researchers and educators across campus.With operations across more than 100 countries, GE Vernova designs, manufactures, and services technologies to generate, transfer, and store electricity with a mission to decarbonize the world. The company is headquartered in Kendall Square, right down the road from MIT, which its leaders say is not a coincidence.“We’re really good at taking proven technologies and commercializing them and scaling them up through our labs,” Martella says. “MIT excels at coming up with those ideas and being a sort of time machine that thinks outside the box to create the future. That’s why this such a great fit: We both have a commitment to research, innovation, and technology.”The alliance is the latest in MIT’s rapidly growing portfolio of research and innovation initiatives around sustainable energy systems, which also includes the Climate Project at MIT. Separate from, but complementary to, the MIT-GE Vernova Alliance, the Climate Project is a campus-wide effort to develop technological, behavioral, and policy solutions to some of the toughest problems impeding an effective global climate response. More

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      in Environment

      For plants, urban heat islands don’t mimic global warming

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      It’s tricky to predict precisely what the impacts of climate change will be, given the many variables involved. To predict the impacts of a warmer world on plant life, some researchers look at urban “heat islands,” where, because of the effects of urban structures, temperatures consistently run a few degrees higher than those of the surrounding rural areas. This enables side-by-side comparisons of plant responses.But a new study by researchers at MIT and Harvard University has found that, at least for forests, urban heat islands are a poor proxy for global warming, and this may have led researchers to underestimate the impacts of warming in some cases. The discrepancy, they found, has a lot to do with the limited genetic diversity of urban tree species.The findings appear in the journal PNAS, in a paper by MIT postdoc Meghan Blumstein, professor of civil and environmental engineering David Des Marais, and four others.“The appeal of these urban temperature gradients is, well, it’s already there,” says Des Marais. “We can’t look into the future, so why don’t we look across space, comparing rural and urban areas?” Because such data is easily obtainable, methods comparing the growth of plants in cities with similar plants outside them have been widely used, he says, and have been quite useful. Researchers did recognize some shortcomings to this approach, including significant differences in availability of some nutrients such as nitrogen. Still, “a lot of ecologists recognized that they weren’t perfect, but it was what we had,” he says.Most of the research by Des Marais’ group is lab-based, under conditions tightly controlled for temperature, humidity, and carbon dioxide concentration. While there are a handful of experimental sites where conditions are modified out in the field, for example using heaters around one or a few trees, “those are super small-scale,” he says. “When you’re looking at these longer-term trends that are occurring over space that’s quite a bit larger than you could reasonably manipulate, an important question is, how do you control the variables?”Temperature gradients have offered one approach to this problem, but Des Marais and his students have also been focusing on the genetics of the tree species involved, comparing those sampled in cities to the same species sampled in a natural forest nearby. And it turned out there were differences, even between trees that appeared similar.“So, lo and behold, you think you’re only letting one variable change in your model, which is the temperature difference from an urban to a rural setting,” he says, “but in fact, it looks like there was also a genotypic diversity that was not being accounted for.”The genetic differences meant that the plants being studied were not representative of those in the natural environment, and the researchers found that the difference was actually masking the impact of warming. The urban trees, they found, were less affected than their natural counterparts in terms of when the plants’ leaves grew and unfurled, or “leafed out,” in the spring.The project began during the pandemic lockdown, when Blumstein was a graduate student. She had a grant to study red oak genotypes across New England, but was unable to travel because of lockdowns. So, she concentrated on trees that were within reach in Cambridge, Massachusetts. She then collaborated with people doing research at the Harvard Forest, a research forest in rural central Massachusetts. They collected three years of data from both locations, including the temperature profiles, the leafing-out timing, and the genetic profiles of the trees. Though the study was looking at red oaks specifically, the researchers say the findings are likely to apply to trees broadly.At the time, researchers had just sequenced the oak tree genome, and that allowed Blumstein and her colleagues to look for subtle differences among the red oaks in the two locations. The differences they found showed that the urban trees were more resistant to the effects of warmer temperatures than were those in the natural environment.“Initially, we saw these results and we were sort of like, oh, this is a bad thing,” Des Marais says. “Ecologists are getting this heat island effect wrong, which is true.” Fortunately, this can be easily corrected by factoring in genomic data. “It’s not that much more work, because sequencing genomes is so cheap and so straightforward. Now, if someone wants to look at an urban-rural gradient and make these kinds of predictions, well, that’s fine. You just have to add some information about the genomes.”It’s not surprising that this genetic variation exists, he says, since growers have learned by trial and error over the decades which varieties of trees tend to thrive in the difficult urban environment, with typically poor soil, poor drainage, and pollution. “As a result, there’s just not much genetic diversity in our trees within cities.”The implications could be significant, Des Marais says. When the Intergovernmental Panel on Climate Change (IPCC) releases its regular reports on the status of the climate, “one of the tools the IPCC has to predict future responses to climate change with respect to temperature are these urban-to-rural gradients.” He hopes that these new findings will be incorporated into their next report, which is just being drafted. “If these results are generally true beyond red oaks, this suggests that the urban heat island approach to studying plant response to temperature is underpredicting how strong that response is.”The research team included Sophie Webster, Robin Hopkins, and David Basler from Harvard University and Jie Yun from MIT. The work was supported by the National Science Foundation, the Bullard Fellowship at the Harvard Forest, and MIT. More

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      in Environment

      MIT Maritime Consortium sets sail

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      Around 11 billion tons of goods, or about 1.5 tons per person worldwide, are transported by sea each year, representing about 90 percent of global trade by volume. Internationally, the merchant shipping fleet numbers around 110,000 vessels. These ships, and the ports that service them, are significant contributors to the local and global economy — and they’re significant contributors to greenhouse gas emissions.A new consortium, formalized in a signing ceremony at MIT last week, aims to address climate-harming emissions in the maritime shipping industry, while supporting efforts for environmentally friendly operation in compliance with the decarbonization goals set by the International Maritime Organization.“This is a timely collaboration with key stakeholders from the maritime industry with a very bold and interdisciplinary research agenda that will establish new technologies and evidence-based standards,” says Themis Sapsis, the William Koch Professor of Marine Technology at MIT and the director of MIT’s Center for Ocean Engineering. “It aims to bring the best from MIT in key areas for commercial shipping, such as nuclear technology for commercial settings, autonomous operation and AI methods, improved hydrodynamics and ship design, cybersecurity, and manufacturing.” Co-led by Sapsis and Fotini Christia, the Ford International Professor of the Social Sciences; director of the Institute for Data, Systems, and Society (IDSS); and director of the MIT Sociotechnical Systems Research Center, the newly-launched MIT Maritime Consortium (MC) brings together MIT collaborators from across campus, including the Center for Ocean Engineering, which is housed in the Department of Mechanical Engineering; IDSS, which is housed in the MIT Schwarzman College of Computing; the departments of Nuclear Science and Engineering and Civil and Environmental Engineering; MIT Sea Grant; and others, with a national and an international community of industry experts.The Maritime Consortium’s founding members are the American Bureau of Shipping (ABS), Capital Clean Energy Carriers Corp., and HD Korea Shipbuilding and Offshore Engineering. Innovation members are Foresight-Group, Navios Maritime Partners L.P., Singapore Maritime Institute, and Dorian LPG.“The challenges the maritime industry faces are challenges that no individual company or organization can address alone,” says Christia. “The solution involves almost every discipline from the School of Engineering, as well as AI and data-driven algorithms, and policy and regulation — it’s a true MIT problem.”Researchers will explore new designs for nuclear systems consistent with the techno-economic needs and constraints of commercial shipping, economic and environmental feasibility of alternative fuels, new data-driven algorithms and rigorous evaluation criteria for autonomous platforms in the maritime space, cyber-physical situational awareness and anomaly detection, as well as 3D printing technologies for onboard manufacturing. Collaborators will also advise on research priorities toward evidence-based standards related to MIT presidential priorities around climate, sustainability, and AI.MIT has been a leading center of ship research and design for over a century, and is widely recognized for contributions to hydrodynamics, ship structural mechanics and dynamics, propeller design, and overall ship design, and its unique educational program for U.S. Navy Officers, the Naval Construction and Engineering Program. Research today is at the forefront of ocean science and engineering, with significant efforts in fluid mechanics and hydrodynamics, acoustics, offshore mechanics, marine robotics and sensors, and ocean sensing and forecasting. The consortium’s academic home at MIT also opens the door to cross-departmental collaboration across the Institute.The MC will launch multiple research projects designed to tackle challenges from a variety of angles, all united by cutting-edge data analysis and computation techniques. Collaborators will research new designs and methods that improve efficiency and reduce greenhouse gas emissions, explore feasibility of alternative fuels, and advance data-driven decision-making, manufacturing and materials, hydrodynamic performance, and cybersecurity.“This consortium brings a powerful collection of significant companies that, together, has the potential to be a global shipping shaper in itself,” says Christopher J. Wiernicki SM ’85, chair and chief executive officer of ABS. “The strength and uniqueness of this consortium is the members, which are all world-class organizations and real difference makers. The ability to harness the members’ experience and know-how, along with MIT’s technology reach, creates real jet fuel to drive progress,” Wiernicki says. “As well as researching key barriers, bottlenecks, and knowledge gaps in the emissions challenge, the consortium looks to enable development of the novel technology and policy innovation that will be key. Long term, the consortium hopes to provide the gravity we will need to bend the curve.” More

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      in Environment

      Technology developed by MIT engineers makes pesticides stick to plant leaves

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      Reducing the amount of agricultural sprays used by farmers — including fertilizers, pesticides and herbicides — could cut down the amount of polluting runoff that ends up in the environment while at the same time reducing farmers’ costs and perhaps even enhancing their productivity. A classic win-win-win.A team of researchers at MIT and a spinoff company they launched has developed a system to do just that. Their technology adds a thin coating around droplets as they are being sprayed onto a field, greatly reducing their tendency to bounce off leaves and end up wasted on the ground. Instead, the coated droplets stick to the leaves as intended.The research is described today in the journal Soft Matter, in a paper by recent MIT alumni Vishnu Jayaprakash PhD ’22 and Sreedath Panat PhD ’23, graduate student Simon Rufer, and MIT professor of mechanical engineering Kripa Varanasi.A recent study found that if farmers didn’t use pesticides, they would lose 78 percent of fruit, 54 percent of vegetable, and 32 percent of cereal production. Despite their importance, a lack of technology that monitors and optimizes sprays has forced farmers to rely on personal experience and rules of thumb to decide how to apply these chemicals. As a result, these chemicals tend to be over-sprayed, leading to runoff and chemicals ending up in waterways or building up in the soil.Pesticides take a significant toll on global health and the environment, the researchers point out. A recent study found that 31 percent of agricultural soils around the world were at high risk from pesticide pollution. And agricultural chemicals are a major expense for farmers: In the U.S., they spend $16 billion a year just on pesticides.Making spraying more efficient is one of the best ways to make food production more sustainable and economical. Agricultural spraying essentially boils down to mixing chemicals into water and spraying water droplets onto plant leaves, which are often inherently water-repellent. “Over more than a decade of research in my lab at MIT, we have developed fundamental understandings of spraying and the interaction between droplets and plants — studying when they bounce and all the ways we have to make them stick better and enhance coverage,” Varanasi says.The team had previously found a way to reduce the amount of sprayed liquid that bounces away from the leaves it strikes, which involved using two spray nozzles instead of one and spraying mixtures with opposite electrical charges. But they found that farmers were reluctant to take on the expense and effort of converting their spraying equipment to a two-nozzle system. So, the team looked for a simpler alternative.They discovered they could achieve the same improvement in droplet retention using a single-nozzle system that can be easily adapted to existing sprayers. Instead of giving the droplets of pesticide an electric charge, they coat each droplet with a vanishingly thin layer of an oily material.In their new study, they conducted lab experiments with high-speed cameras. When they sprayed droplets with no special treatment onto a water-repelling (hydrophobic) surface similar to that of many plant leaves, the droplets initially spread out into a pancake-like disk, then rebounded back into a ball and bounced away. But when the researchers coated the surface of the droplets with a tiny amount of oil — making up less than 1 percent of the droplet’s liquid — the droplets spread out and then stayed put. The treatment improved the droplets’ “stickiness” by as much as a hundredfold.“When these droplets are hitting the surface and as they expand, they form this oil ring that essentially pins the droplet to the surface,” Rufer says. The researchers tried a wide variety of conditions, he says, explaining that they conducted hundreds of experiments, “with different impact velocities, different droplet sizes, different angles of inclination, all the things that fully characterize this phenomenon.” Though different oils varied in their effectiveness, all of them were effective. “Regardless of the impact velocity and the oils, we saw that the rebound height was significantly lower,” he says.The effect works with remarkably small amounts of oil. In their initial tests they used 1 percent oil compared to the water, then they tried a 0.1 percent, and even .01. The improvement in droplets sticking to the surface continued at a 0.1 percent, but began to break down beyond that. “Basically, this oil film acts as a way to trap that droplet on the surface, because oil is very attracted to the surface and sort of holds the water in place,” Rufer says.In the researchers’ initial tests they used soybean oil for the coating, figuring this would be a familiar material for the farmers they were working with, many of whom were growing soybeans. But it turned out that though they were producing the beans, the oil was not part of their usual supply chain for use on the farm. In further tests, the researchers found that several chemicals that farmers were already routinely using in their spraying, called surfactants and adjuvants, could be used instead, and that some of these provided the same benefits in keeping the droplets stuck on the leaves.“That way,” Varanasi says, “we’re not introducing a new chemical or changed chemistries into their field, but they’re using things they’ve known for a long time.”Varanasi and Jayaprakash formed a company called AgZen to commercialize the system. In order to prove how much their coating system improves the amount of spray that stays on the plant, they first had to develop a system to monitor spraying in real time. That system, which they call RealCoverage, has been deployed on farms ranging in size from a few dozen acres to hundreds of thousands of acres, and many different crop types, and has saved farmers 30 to 50 percent on their pesticide expenditures, just by improving the controls on the existing sprays. That system is being deployed to 920,000 acres of crops in 2025, the company says, including some in California, Texas, the Midwest, France and Italy. Adding the cloaking system using new nozzles, the researchers say, should yield at least another doubling of efficiency.“You could give back a billion dollars to U.S. growers if you just saved 6 percent of their pesticide budget,” says Jayaprakash, lead author of the research paper and CEO of AgZen. “In the lab we got 300 percent of extra product on the plant. So that means we could get orders of magnitude reductions in the amount of pesticides that farmers are spraying.”Farmers had already been using these surfactant and adjuvant chemicals as a way to enhance spraying effectiveness, but they were mixing it with a water solution. For it to have any effect, they had to use much more of these materials, risking causing burns to the plants. The new coating system reduces the amount of these materials needed, while improving their effectiveness.In field tests conducted by AgZen, “we doubled the amount of product on kale and soybeans just by changing where the adjuvant was,” from mixed in to being a coating, Jayaprakash says. It’s convenient for farmers because “all they’re doing is changing their nozzle. They’re getting all their existing chemicals to work better, and they’re getting more product on the plant.”And it’s not just for pesticides. “The really cool thing is this is useful for every chemistry that’s going on the leaf, be it an insecticide, a herbicide, a fungicide, or foliar nutrition,” Varanasi says. This year, they plan to introduce the new spray system on about 30,000 acres of cropland.Varanasi says that with projected world population growth, “the amount of food production has got to double, and we are limited in so many resources, for example we cannot double the arable land. … This means that every acre we currently farm must become more efficient and able to do more with less.” These improved spraying technologies, for both monitoring the spraying and coating the droplets, Varanasi says, “I think is fundamentally changing agriculture.”AgZen has recently raised $10 million in venture financing to support rapid commercial deployment of these technologies that can improve the control of chemical inputs into agriculture. “The knowledge we are gathering from every leaf, combined with our expertise in interfacial science and fluid mechanics, is giving us unparalleled insights into how chemicals are used and developed — and it’s clear that we can deliver value across the entire agrochemical supply chain,” Varanasi says  “Our mission is to use these technologies to deliver improved outcomes and reduced costs for the ag industry.”  More

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      in Energy

      Making solar projects cheaper and faster with portable factories

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      As the price of solar panels has plummeted in recent decades, installation costs have taken up a greater share of the technology’s overall price tag. The long installation process for solar farms is also emerging as a key bottleneck in the deployment of solar energy.Now the startup Charge Robotics is developing solar installation factories to speed up the process of building large-scale solar farms. The company’s factories are shipped to the site of utility solar projects, where equipment including tracks, mounting brackets, and panels are fed into the system and automatically assembled. A robotic vehicle autonomously puts the finished product — which amounts to a completed section of solar farm — in its final place.“We think of this as the Henry Ford moment for solar,” says CEO Banks Hunter ’15, who founded Charge Robotics with fellow MIT alumnus Max Justicz ’17. “We’re going from a very bespoke, hands on, manual installation process to something much more streamlined and set up for mass manufacturing. There are all kinds of benefits that come along with that, including consistency, quality, speed, cost, and safety.”Last year, solar energy accounted for 81 percent of new electric capacity in the U.S., and Hunter and Justicz see their factories as necessary for continued acceleration in the industry.The founders say they were met with skepticism when they first unveiled their plans. But in the beginning of last year, they deployed a prototype system that successfully built a solar farm with SOLV Energy, one of the largest solar installers in the U.S. Now, Charge has raised $22 million for its first commercial deployments later this year.From surgical robots to solar robotsWhile majoring in mechanical engineering at MIT, Hunter found plenty of excuses to build things. One such excuse was Course 2.009 (Product Engineering Processes), where he and his classmates built a smart watch for communication in remote areas.After graduation, Hunter worked for the MIT alumni-founded startups Shaper Tools and Vicarious Surgical. Vicarious Surgical is a medical robotics company that has raised more than $450 million to date. Hunter was the second employee and worked there for five years.“A lot of really hands on, project-based classes at MIT translated directly into my first roles coming out of school and set me up to be very independent and run large engineering projects,” Hunter says, “Course 2.009, in particular, was a big launch point for me. The founders of Vicarious Surgical got in touch with me through the 2.009 network.”As early as 2017, Hunter and Justicz, who majored in mechanical engineering and computer science, had discussed starting a company together. But they had to decide where to apply their broad engineering and product skillsets.“Both of us care a lot about climate change. We see climate change as the biggest problem impacting the greatest number of people on the planet,” Hunter says. “Our mentality was if we can build anything, we might as well build something that really matters.”In the process of cold calling hundreds of people in the energy industry, the founders decided solar was the future of energy production because its price was decreasing so quickly.“It’s becoming cheaper faster than any other form of energy production in human history,” Hunter says.When the founders began visiting construction sites for the large, utility-scale solar farms that make up the bulk of energy generation, it wasn’t hard to find the bottlenecks. The first site they traveled to was in the Mojave Desert in California. Hunter describes it as a massive dust bowl where thousands of workers spent months repeating tasks like moving material and assembling the same parts, over and over again.“The site had something like 2 million panels on it, and every single one was assembled and fastened the same way by hand,” Hunter says. “Max and I thought it was insane. There’s no way that can scale to transform the energy grid in a short window of time.”Hunter says he heard from each of the largest solar companies in the U.S. that their biggest limitation for scaling was labor shortages. The problem was slowing growth and killing projects.Hunter and Justicz founded Charge Robotics in 2021 to break through that bottleneck. Their first step was to order utility solar parts and assemble them by hand in their backyards.“From there, we came up with this portable assembly line that we could ship out to construction sites and then feed in the entire solar system, including the steel tracks, mounting brackets, fasteners, and the solar panels,” Hunter explains. “The assembly line robotically assembles all those pieces to produce completed solar bays, which are chunks of a solar farm.”

      Charge Robotics’ machine transports an autonomously assembled portion of solar farm to its final place in a solar farm.

      Credit: Courtesy of Charge Robotics

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      Each bay represents a 40-foot piece of the solar farm and weighs about 800 pounds. A robotic vehicle brings it to its final location in the field. Hunter says Charge’s system automates all mechanical installation except for the process of pile driving the first metal stakes into the ground.Charge’s assembly lines also have machine-vision systems that scan each part to ensure quality, and the systems work with the most common solar parts and panel sizes.From pilot to productWhen the founders started pitching their plans to investors and construction companies, people didn’t believe it was possible.“The initial feedback was basically, ‘This will never work,’” Hunter says. “But as soon as we took our first system out into the field and people saw it operating, they got much more excited and started believing it was real.”Since that first deployment, Charge’s team has been making its system faster and easier to operate. The company plans to set up its factories at project sites and run them in partnership with solar construction companies. The factories could even run alongside human workers.“With our system, people are operating robotic equipment remotely rather than putting in the screws themselves,” Hunter explains. “We can essentially deliver the assembled solar to customers. Their only responsibility is to deliver the materials and parts on big pallets that we feed into our system.”Hunter says multiple factories could be deployed at the same site and could also operate 24/7 to dramatically speed up projects.“We are hitting the limits of solar growth because these companies don’t have enough people,” Hunter says. “We can build much bigger sites much faster with the same number of people by just shipping out more of our factories. It’s a fundamentally new way of scaling solar energy.” More

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      in Environment

      Study: Climate change will reduce the number of satellites that can safely orbit in space

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      MIT aerospace engineers have found that greenhouse gas emissions are changing the environment of near-Earth space in ways that, over time, will reduce the number of satellites that can sustainably operate there.In a study appearing today in Nature Sustainability, the researchers report that carbon dioxide and other greenhouse gases can cause the upper atmosphere to shrink. An atmospheric layer of special interest is the thermosphere, where the International Space Station and most satellites orbit today. When the thermosphere contracts, the decreasing density reduces atmospheric drag — a force that pulls old satellites and other debris down to altitudes where they will encounter air molecules and burn up.Less drag therefore means extended lifetimes for space junk, which will litter sought-after regions for decades and increase the potential for collisions in orbit.The team carried out simulations of how carbon emissions affect the upper atmosphere and orbital dynamics, in order to estimate the “satellite carrying capacity” of low Earth orbit. These simulations predict that by the year 2100, the carrying capacity of the most popular regions could be reduced by 50-66 percent due to the effects of greenhouse gases.“Our behavior with greenhouse gases here on Earth over the past 100 years is having an effect on how we operate satellites over the next 100 years,” says study author Richard Linares, associate professor in MIT’s Department of Aeronautics and Astronautics (AeroAstro).“The upper atmosphere is in a fragile state as climate change disrupts the status quo,” adds lead author William Parker, a graduate student in AeroAstro. “At the same time, there’s been a massive increase in the number of satellites launched, especially for delivering broadband internet from space. If we don’t manage this activity carefully and work to reduce our emissions, space could become too crowded, leading to more collisions and debris.”The study includes co-author Matthew Brown of the University of Birmingham.Sky fallThe thermosphere naturally contracts and expands every 11 years in response to the sun’s regular activity cycle. When the sun’s activity is low, the Earth receives less radiation, and its outermost atmosphere temporarily cools and contracts before expanding again during solar maximum.In the 1990s, scientists wondered what response the thermosphere might have to greenhouse gases. Their preliminary modeling showed that, while the gases trap heat in the lower atmosphere, where we experience global warming and weather, the same gases radiate heat at much higher altitudes, effectively cooling the thermosphere. With this cooling, the researchers predicted that the thermosphere should shrink, reducing atmospheric density at high altitudes.In the last decade, scientists have been able to measure changes in drag on satellites, which has provided some evidence that the thermosphere is contracting in response to something more than the sun’s natural, 11-year cycle.“The sky is quite literally falling — just at a rate that’s on the scale of decades,” Parker says. “And we can see this by how the drag on our satellites is changing.”The MIT team wondered how that response will affect the number of satellites that can safely operate in Earth’s orbit. Today, there are over 10,000 satellites drifting through low Earth orbit, which describes the region of space up to 1,200 miles (2,000 kilometers), from Earth’s surface. These satellites deliver essential services, including internet, communications, navigation, weather forecasting, and banking. The satellite population has ballooned in recent years, requiring operators to perform regular collision-avoidance maneuvers to keep safe. Any collisions that do occur can generate debris that remains in orbit for decades or centuries, increasing the chance for follow-on collisions with satellites, both old and new.“More satellites have been launched in the last five years than in the preceding 60 years combined,” Parker says. “One of key things we’re trying to understand is whether the path we’re on today is sustainable.”Crowded shellsIn their new study, the researchers simulated different greenhouse gas emissions scenarios over the next century to investigate impacts on atmospheric density and drag. For each “shell,” or altitude range of interest, they then modeled the orbital dynamics and the risk of satellite collisions based on the number of objects within the shell. They used this approach to identify each shell’s “carrying capacity” — a term that is typically used in studies of ecology to describe the number of individuals that an ecosystem can support.“We’re taking that carrying capacity idea and translating it to this space sustainability problem, to understand how many satellites low Earth orbit can sustain,” Parker explains.The team compared several scenarios: one in which greenhouse gas concentrations remain at their level from the year 2000 and others where emissions change according to the Intergovernmental Panel on Climate Change (IPCC) Shared Socioeconomic Pathways (SSPs). They found that scenarios with continuing increases in emissions would lead to a significantly reduced carrying capacity throughout low Earth orbit.In particular, the team estimates that by the end of this century, the number of satellites safely accommodated within the altitudes of 200 and 1,000 kilometers could be reduced by 50 to 66 percent compared with a scenario in which emissions remain at year-2000 levels. If satellite capacity is exceeded, even in a local region, the researchers predict that the region will experience a “runaway instability,” or a cascade of collisions that would create so much debris that satellites could no longer safely operate there.Their predictions forecast out to the year 2100, but the team says that certain shells in the atmosphere today are already crowding up with satellites, particularly from recent “megaconstellations” such as SpaceX’s Starlink, which comprises fleets of thousands of small internet satellites.“The megaconstellation is a new trend, and we’re showing that because of climate change, we’re going to have a reduced capacity in orbit,” Linares says. “And in local regions, we’re close to approaching this capacity value today.”“We rely on the atmosphere to clean up our debris. If the atmosphere is changing, then the debris environment will change too,” Parker adds. “We show the long-term outlook on orbital debris is critically dependent on curbing our greenhouse gas emissions.”This research is supported, in part, by the U.S. National Science Foundation, the U.S. Air Force, and the U.K. Natural Environment Research Council. More

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      in Energy

      Developing materials for stellar performance in fusion power plants

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      When Zoe Fisher was in fourth grade, her art teacher asked her to draw her vision of a dream job on paper. At the time, those goals changed like the flavor of the week in an ice cream shop — “zookeeper” featured prominently for a while — but Zoe immediately knew what she wanted to put down: a mad scientist.When Fisher stumbled upon the drawing in her parents’ Chicago home recently, it felt serendipitous because, by all measures, she has realized that childhood dream. The second-year doctoral student at MIT’s Department of Nuclear Science and Engineering (NSE) is studying materials for fusion power plants at the Plasma Science and Fusion Center (PSFC) under the advisement of Michael Short, associate professor at NSE. Dennis Whyte, Hitachi America Professor of Engineering at NSE, serves as co-advisor.On track to an MIT educationGrowing up in Chicago, Fisher had heard her parents remarking on her reasoning abilities. When she was barely a preschooler she argued that she couldn’t have been found in a purple speckled egg, as her parents claimed they had done.Fisher didn’t put together just how much she had gravitated toward science until a high school physics teacher encouraged her to apply to MIT. Passionate about both the arts and sciences, she initially worried that pursuing science would be very rigid, without room for creativity. But she knows now that exploring solutions to problems requires plenty of creative thinking.It was a visit to MIT through the Weekend Immersion in Science and Engineering (WISE) that truly opened her eyes to the potential of an MIT education. “It just seemed like the undergraduate experience here is where you can be very unapologetically yourself. There’s no fronting something you don’t want to be like. There’s so much authenticity compared to most other colleges I looked at,” Fisher says. Once admitted, Campus Preview Weekend confirmed that she belonged. “We got to be silly and weird — a version of the Mafia game was a hit — and I was like, ‘These are my people,’” Fisher laughs.Pursuing fusion at NSEBefore she officially started as a first-year in 2018, Fisher enrolled in the Freshman Pre-Orientation Program (FPOP), which starts a week before orientation starts. Each FPOP zooms into one field. “I’d applied to the nuclear one simply because it sounded cool and I didn’t know anything about it,” Fisher says. She was intrigued right away. “They really got me with that ‘star in a bottle’ line,” she laughs. (The quest for commercial fusion is to create the energy equivalent of a star in a bottle). Excited by a talk by Zachary Hartwig, Robert N. Noyce Career Development Professor at NSE, Fisher asked if she could work on fusion as an undergraduate as part of an Undergraduate Research Opportunities Program (UROP) project. She started with modeling solders for power plants and was hooked. When Fisher requested more experimental work, Hartwig put her in touch with Research Scientist David Fischer at the Plasma Science and Fusion Center (PSFC). Fisher eventually moved on to explore superconductors, which eventually morphed into research for her master’s thesis.For her doctoral research, Fisher is extending her master’s work to explore defects in ceramics, specifically in alumina (aluminum oxide). Sapphire coatings are the single-crystal equivalent of alumina, an insulator being explored for use in fusion power plants. “I eventually want to figure out what types of charge defects form in ceramics during radiation damage so we can ultimately engineer radiation-resistant sapphire,” Fisher says.When you introduce a material in a fusion power plant, stray high-energy neutrons born from the plasma can collide and fundamentally reorder the lattice, which is likely to change a range of thermal, electrical, and structural properties. “Think of a scaffolding outside a building, with each one of those joints as a different atom that holds your material in place. If you go in and you pull a joint out, there’s a chance that you pulled out a joint that wasn’t structurally sound, in which case everything would be fine. But there’s also a chance that you pull a joint out and everything alters. And [such unpredictability] is a problem,” Fisher says. “We need to be able to account for exactly how these neutrons are going to alter the lattice property,” Fisher says, and it’s one of the topics her research explores.The studies, in turn, can function as a jumping-off point for irradiating superconductors. The goals are two-fold: “I want to figure out how I can make an industry-usable ceramic you can use to insulate the inside of a fusion power plant, and then also figure out if I can take this information that I’m getting with ceramics and make it superconductor-relevant,” Fisher says. “Superconductors are the electromagnets we will use to contain the plasma inside fusion power plants. However, they prove pretty difficult to study. Since they are also ceramic, you can draw a lot of parallels between alumina and yttrium barium copper oxide (YBCO), the specific superconductor we use,” she adds. Fisher is also excited about the many experiments she performs using a particle accelerator, one of which involves measuring exactly how surface thermal properties change during radiation.Sailing new pathsIt’s not just her research that Fisher loves. As an undergrad, and during her master’s, she was on the varsity sailing team. “I worked my way into sailing with literal Olympians, I did not see that coming,” she says. Fisher participates in Chicago’s Race to Mackinac and the Melges 15 Series every chance she gets. Of all the types of boats she has sailed, she prefers dinghy sailing the most. “It’s more physical, you have to throw yourself around a lot and there’s this immediate cause and effect, which I like,” Fisher says. She also teaches sailing lessons in the summer at MIT’s Sailing Pavilion — you can find her on a small motorboat, issuing orders through a speaker.Teaching has figured prominently throughout Fisher’s time at MIT. Through MISTI, Fisher has taught high school classes in Germany and a radiation and materials class in Armenia in her senior year. She was delighted by the food and culture in Armenia and by how excited people were to learn new ideas. Her love of teaching continues, as she has reached out to high schools in the Boston area. “I like talking to groups and getting them excited about fusion, or even maybe just the concept of attending graduate school,” Fisher says, adding that teaching the ropes of an experiment one-on-one is “one of the most rewarding things.”She also learned the value of resilience and quick thinking on various other MISTI trips. Despite her love of travel, Fisher has had a few harrowing experiences with tough situations and plans falling through at the last minute. It’s when she tells herself, “Well, the only thing that you’re gonna do is you’re gonna keep doing what you wanted to do.”That eyes-on-the-prize focus has stood Fisher in good stead, and continues to serve her well in her research today. More