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      in Energy

      Rafael Mariano Grossi speaks about nuclear power’s role at a critical moment in history

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      On Sept. 22, Rafael Mariano Grossi, director general of the International Atomic Energy Agency (IAEA), delivered the 2023 David J. Rose Lecture in Nuclear Technology at MIT. This lecture series was started nearly 40 years ago in honor of the late Professor David Rose — a nuclear engineering professor and fusion technology pioneer. In addition to his scientific contributions, Rose was invested in the ethical issues associated with new technologies. His widow, Renate Rose, who spoke briefly before Grossi’s lecture, said that her husband adamantly called for the abolishment of nuclear weapons, insisting that all science should serve the common good and that every scientist should follow his or her conscience.

      In his prefatory remarks, MIT Vice Provost Richard Lester, a former PhD student of David Rose, said that even today, he still feels the influence of his thesis advisor, many decades after they’d worked together. Lester called it a “great honor” to introduce Grossi, noting that the director general was guiding the agency through an especially demanding time. “His presence with us is a reminder that the biggest challenges we face today are truly global challenges, and that international organizations like the IAEA have a central role to play in resolving them.”

      The title of Grossi’s talk was “The IAEA at the Crossroads of History,” and he made a strong case for this being a critical juncture, or “inflection point,” for nuclear power. He started his speech, however, with somewhat of an historical footnote, discussing a letter that Rose sent in 1977 to Sigvard Eklund, IAEA’s then-director general. Rose urged the IAEA to establish a coordinated worldwide program in controlled fusion research. It took a while for the idea to gain traction, but international collaboration in fusion formally began in 1985, eight years after Rose’s proposal. “I thought I would begin with this story, because it shows that cooperation between MIT and the IAEA goes back a long way,” Grossi said.

      2023 David J. Rose Lecture in Nuclear TechnologyVideo: MIT Department of Nuclear Science and Engineering

      Overall, he painted a mostly encouraging picture for the future of nuclear power, largely based on its potential to generate electricity or thermal energy without adding greenhouse gases to the atmosphere. In the face of rapidly-unfolding climate change, Grossi said, “low-carbon nuclear power is now seen as part of [the] solution by an increasing number of people. It’s getting harder to be an environmentalist in good faith who is against nuclear.”

      Public acceptance is growing throughout the world, he added. In Sweden, where people had long protested against radioactive waste transport, a poll now shows that more than 85 percent of the people approve of the nation’s high-level waste handling and disposal facilities. Even Finland’s Green Party has embraced nuclear power, Grossi said. “I don’t think we could imagine a pro-nuclear Green Party five years ago, let alone in 1970 or ’80.”

      Fifty-seven nuclear reactors are being constructed right now in 17 countries. One of the world’s newest facilities, the Barakah nuclear power plant in the United Arab Emirates, “was built on ground rich in oil and natural gas,” he said. In China, the world’s first pebble-bed high-temperature reactor has been operating for two years, offering potential advantages in safety, efficiency, and modularity. For countries that don’t have any nuclear plants, small modular reactors of this kind “offer the chance of a more gradual and affordable way to scale up nuclear power,” Grossi noted. The IAEA is working with countries like Ghana, Kenya, and Senegal to help them develop the safety and regulatory infrastructures that would be needed to build and responsibly operate modular nuclear reactors like this.

      Grossi also discussed a number of lesser-known projects the IAEA is engaged in that have little to do with power generation. Seventy percent of the people in Africa, for example, have no access to radiotherapy to fight cancer. To this end, the IAEA is now helping to provide radiotherapy services in Tanzania and other African countries. At the IAEA’s Marine Environmental Laboratories in Monaco, researchers are using isotopic tracing techniques to study the impact of microplastic pollution on the oceans. The Covid-19 pandemic illustrated the potentially devastating effects of zoonotic diseases that can infect humans with animal-borne viruses. To counteract this threat, the IAEA has sent hundreds of reverse transcription-polymerase chain reaction (RT-PCR) machines — capable of detecting specific genetic materials in pathogens — to more than 130 countries.

      Meanwhile, new risks have emerged from the war in Ukraine, where fighting has raged for a year-and-a-half near the six nuclear reactors in Zaporizhzhia — Europe’s largest nuclear power plant. Early in the conflict, the IAEA sent a team of experts to monitor the plant and to do everything possible to prevent a nuclear accident that would bring “even more misery to people who are already suffering so much,” Grossi said. A major accident, he added, would likely stall investments in nuclear power at a time when its future prospects were starting to brighten.

      At the end of his talk, Grossi returned to the subject of fusion, which he expects to become an important energy source, perhaps in the not-too-distant future. He was encouraged by the visit he’d just had to the MIT spinoff company, Commonwealth Fusion Systems. With regard to fusion, he said, “for the first time, all the pieces of the puzzle are there: the physics, the policy drivers, and the investment.” In fact, an agreement was signed on the day of his lecture, which made MIT’s Plasma Science and Fusion Center an IAEA collaboration center — the second such center in the United States.

      “When I think of all the new forms of collaboration happening today, I imagine Professor Rose would be delighted,” Grossi said. “It really is something to hold [his] letter and know how much progress has been made since 1977 in fusion. I look forward to our collaboration going forward.” More

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      in Energy

      MIT design would harness 40 percent of the sun’s heat to produce clean hydrogen fuel

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      MIT engineers aim to produce totally green, carbon-free hydrogen fuel with a new, train-like system of reactors that is driven solely by the sun.

      In a study appearing today in Solar Energy Journal, the engineers lay out the conceptual design for a system that can efficiently produce “solar thermochemical hydrogen.” The system harnesses the sun’s heat to directly split water and generate hydrogen — a clean fuel that can power long-distance trucks, ships, and planes, while in the process emitting no greenhouse gas emissions.

      Today, hydrogen is largely produced through processes that involve natural gas and other fossil fuels, making the otherwise green fuel more of a “grey” energy source when considered from the start of its production to its end use. In contrast, solar thermochemical hydrogen, or STCH, offers a totally emissions-free alternative, as it relies entirely on renewable solar energy to drive hydrogen production. But so far, existing STCH designs have limited efficiency: Only about 7 percent of incoming sunlight is used to make hydrogen. The results so far have been low-yield and high-cost.

      In a big step toward realizing solar-made fuels, the MIT team estimates its new design could harness up to 40 percent of the sun’s heat to generate that much more hydrogen. The increase in efficiency could drive down the system’s overall cost, making STCH a potentially scalable, affordable option to help decarbonize the transportation industry.

      “We’re thinking of hydrogen as the fuel of the future, and there’s a need to generate it cheaply and at scale,” says the study’s lead author, Ahmed Ghoniem, the Ronald C. Crane Professor of Mechanical Engineering at MIT. “We’re trying to achieve the Department of Energy’s goal, which is to make green hydrogen by 2030, at $1 per kilogram. To improve the economics, we have to improve the efficiency and make sure most of the solar energy we collect is used in the production of hydrogen.”

      Ghoniem’s study co-authors are Aniket Patankar, first author and MIT postdoc; Harry Tuller, MIT professor of materials science and engineering; Xiao-Yu Wu of the University of Waterloo; and Wonjae Choi at Ewha Womans University in South Korea.

      Solar stations

      Similar to other proposed designs, the MIT system would be paired with an existing source of solar heat, such as a concentrated solar plant (CSP) — a circular array of hundreds of mirrors that collect and reflect sunlight to a central receiving tower. An STCH system then absorbs the receiver’s heat and directs it to split water and produce hydrogen. This process is very different from electrolysis, which uses electricity instead of heat to split water.

      At the heart of a conceptual STCH system is a two-step thermochemical reaction. In the first step, water in the form of steam is exposed to a metal. This causes the metal to grab oxygen from steam, leaving hydrogen behind. This metal “oxidation” is similar to the rusting of iron in the presence of water, but it occurs much faster. Once hydrogen is separated, the oxidized (or rusted) metal is reheated in a vacuum, which acts to reverse the rusting process and regenerate the metal. With the oxygen removed, the metal can be cooled and exposed to steam again to produce more hydrogen. This process can be repeated hundreds of times.

      The MIT system is designed to optimize this process. The system as a whole resembles a train of box-shaped reactors running on a circular track. In practice, this track would be set around a solar thermal source, such as a CSP tower. Each reactor in the train would house the metal that undergoes the redox, or reversible rusting, process.

      Each reactor would first pass through a hot station, where it would be exposed to the sun’s heat at temperatures of up to 1,500 degrees Celsius. This extreme heat would effectively pull oxygen out of a reactor’s metal. That metal would then be in a “reduced” state — ready to grab oxygen from steam. For this to happen, the reactor would move to a cooler station at temperatures around 1,000 C, where it would be exposed to steam to produce hydrogen.

      Rust and rails

      Other similar STCH concepts have run up against a common obstacle: what to do with the heat released by the reduced reactor as it is cooled. Without recovering and reusing this heat, the system’s efficiency is too low to be practical.

      A second challenge has to do with creating an energy-efficient vacuum where metal can de-rust. Some prototypes generate a vacuum using mechanical pumps, though the pumps are too energy-intensive and costly for large-scale hydrogen production.

      To address these challenges, the MIT design incorporates several energy-saving workarounds. To recover most of the heat that would otherwise escape from the system, reactors on opposite sides of the circular track are allowed to exchange heat through thermal radiation; hot reactors get cooled while cool reactors get heated. This keeps the heat within the system. The researchers also added a second set of reactors that would circle around the first train, moving in the opposite direction. This outer train of reactors would operate at generally cooler temperatures and would be used to evacuate oxygen from the hotter inner train, without the need for energy-consuming mechanical pumps.

      These outer reactors would carry a second type of metal that can also easily oxidize. As they circle around, the outer reactors would absorb oxygen from the inner reactors, effectively de-rusting the original metal, without having to use energy-intensive vacuum pumps. Both reactor trains would  run continuously and would enerate separate streams of pure hydrogen and oxygen.

      The researchers carried out detailed simulations of the conceptual design, and found that it would significantly boost the efficiency of solar thermochemical hydrogen production, from 7 percent, as previous designs have demonstrated, to 40 percent.

      “We have to think of every bit of energy in the system, and how to use it, to minimize the cost,” Ghoniem says. “And with this design, we found that everything can be powered by heat coming from the sun. It is able to use 40 percent of the sun’s heat to produce hydrogen.”

      “If this can be realized, it could drastically change our energy future — namely, enabling hydrogen production, 24/7,” says Christopher Muhich, an assistant professor of chemical engineering at Arizona State University, who was not involved in the research. “The ability to make hydrogen is the linchpin to producing liquid fuels from sunlight.”

      In the next year, the team will be building a prototype of the system that they plan to test in concentrated solar power facilities at laboratories of the Department of Energy, which is currently funding the project.

      “When fully implemented, this system would be housed in a little building in the middle of a solar field,” Patankar explains. “Inside the building, there could be one or more trains each having about 50 reactors. And we think this could be a modular system, where you can add reactors to a conveyor belt, to scale up hydrogen production.”

      This work was supported by the Centers for Mechanical Engineering Research and Education at MIT and SUSTech. More

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      in Energy

      Printing a new approach to fusion power plant materials

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      When Alexander O’Brien sent in his application for graduate school at MIT’s Department of Nuclear Science and Engineering, he had a germ of a research idea already brewing. So when he received a phone call from Professor Mingda Li, he shared it: The student from Arkansas wanted to explore the design of materials that could hold nuclear reactors together.

      Li listened to him patiently and then said, “I think you’d be a really good fit for Professor Ju Li,” O’Brien remembers. Ju Li, the Battelle Energy Alliance Professor in Nuclear Engineering, had wanted to explore 3D printing for nuclear reactors and O’Brien seemed like the right candidate. “At that moment I decided to go to MIT if they accepted me,” O’Brien remembers.

      And they did.

      Under the advisement of Ju Li, the fourth-year doctoral student now explores 3D printing of ceramic-metal composites, materials that can be used to construct fusion power plants.

      An early interest in the sciences

      Growing up in Springdale, Arkansas as a self-described “band nerd,” O’Brien was particularly interested in chemistry and physics. It was one thing to mix baking soda and vinegar to make a “volcano” and quite another to understand why that was happening. “I just enjoyed understanding things on a deeper level and being able to figure out how the world works,” he says.

      At the same time, it was difficult to ignore the economics of energy playing out in his own backyard. When Arkansas, a place that had hardly ever seen earthquakes, started registering them in the wake of fracking in neighboring Oklahoma, it was “like a lightbulb moment” for O’Brien. “I knew this was going to create problems down the line, I knew there’s got to be a better way to do [energy],” he says.

      With the idea of energy alternatives simmering on the back burner, O’Brien enrolled for undergraduate studies at the University of Arkansas. He participated in the school’s marching band — “you show up a week before everyone else and there’s 400 people who automatically become your friends” — and enjoyed the social environment that a large state school could offer.

      O’Brien double-majored in chemical engineering and physics and appreciated “the ability to get your hands dirty on machinery to make things work.” Deciding to begin exploring his interest in energy alternatives, O’Brien researched transition metal dichalcogenides, coatings of which could catalyze the hydrogen evolution reaction and more easily create hydrogen gas, a green energy alternative.

      It was shortly after his sophomore year, however, that O’Brien really found his way in the field of energy alternatives — in nuclear engineering. The American Chemical Society was soliciting student applications for summer study of nuclear chemistry in San Jose, California. O’Brien applied and got accepted. “After years of knowing I wanted to work in green energy but not knowing what that looked like, I very quickly fell in love with [nuclear engineering],” he says. That summer also cemented O’Brien’s decision to attend graduate school. “I came away with this idea of ‘I need to go to grad school because I need to know more about this,’” he says.

      O’Brien especially appreciated an independent project, assigned as part of the summer program: He chose to research nuclear-powered spacecraft. In digging deeper, O’Brien discovered the challenges of powering spacecraft — nuclear was the most viable alternative, but it had to work around extraneous radiation sources in space. Getting to explore national laboratories near San Jose sealed the deal. “I got to visit the National Ignition Facility, which is the big fusion center up there, and just seeing that massive facility entirely designed around this one idea of fusion was kind of mind-blowing to me,” O’Brien says.

      A fresh blueprint for fusion power plants

      O’Brien’s current research at MIT’s Department of Nuclear Science and Engineering (NSE) is equally mind-blowing.

      As the design of new fusion devices kicks into gear, it’s becoming increasingly apparent that the materials we have been using just don’t hold up to the higher temperatures and radiation levels in operating environments, O’Brien says. Additive manufacturing, another term for 3D printing, “opens up a whole new realm of possibilities for what you can do with metals, which is exactly what you’re going to need [to build the next generation of fusion power plants],” he says.

      Metals and ceramics by themselves might not do the job of withstanding high temperatures (750 degrees Celsius is the target) and stresses and radiation, but together they might get there. Although such metal matrix composites have been around for decades, they have been impractical for use in reactors because they’re “difficult to make with any kind of uniformity and really limited in size scale,” O’Brien says. That’s because when you try to place ceramic nanoparticles into a pool of molten metal, they’re going to fall out in whichever direction they want. “3D printing quickly changes that story entirely, to the point where if you want to add these nanoparticles in very specific regions, you have the capability to do that,” O’Brien says.

      O’Brien’s work, which forms the basis of his doctoral thesis and a research paper in the journal Additive Manufacturing, involves implanting metals with ceramic nanoparticles. The net result is a metal matrix composite that is an ideal candidate for fusion devices, especially for the vacuum vessel component, which must be able to withstand high temperatures, extremely corrosive molten salts, and internal helium gas from nuclear transmutation.

      O’Brien’s work focuses on nickel superalloys like Inconel 718, which are especially robust candidates because they can withstand higher operating temperatures while retaining strength. Helium embrittlement, where bubbles of helium caused by fusion neutrons lead to weakness and failure, is a problem with Inconel 718, but composites exhibit potential to overcome this challenge.

      To create the composites, first a mechanical milling process coats the ceramic onto the metal particles. The ceramic nanoparticles act as reinforcing strength agents, especially at high temperatures, and make materials last longer. The nanoparticles also absorb helium and radiation defects when uniformly dispersed, which prevent these damage agents from all getting to the grain boundaries.

      The composite then goes through a 3D printing process called powder bed fusion (non-nuclear fusion), where a laser passes over a bed of this powder melting it into desired shapes. “By coating these particles with the ceramic and then only melting very specific regions, we keep the ceramics in the areas that we want, and then you can build up and have a uniform structure,” O’Brien says.

      Printing an exciting future

      The 3D printing of nuclear materials exhibits such promise that O’Brien is looking at pursuing the prospect after his doctoral studies. “The concept of these metal matrix composites and how they can enhance material property is really interesting,” he says. Scaling it up commercially through a startup company is on his radar.

      For now, O’Brien is enjoying research and catching an occasional Broadway show with his wife. While the band nerd doesn’t pick up his saxophone much anymore, he does enjoy driving up to New Hampshire and going backpacking. “That’s my newfound hobby,” O’Brien says, “since I started grad school.” More

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      in Environment

      A reciprocal relationship with the land in Hawaiʻi

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      Aja Grande grew up on the Hawaiian island of Oʻahu, between the Kona and ʻEwa districts, nurtured by her community and the natural environment. Her family has lived in Hawaiʻi for generations; while she is not “Kanaka ʻŌiwi,” of native Hawaiian descent, she is proud to trace her family’s history to the time of the Hawaiian Kingdom in the 19th century. Grande is now a PhD candidate in MIT’s HASTS (History, Anthropology, Science, Technology and Society) program, and part of her dissertation tracks how Hawaiian culture and people’s relationship with the land has evolved throughout time.

      “The fondest memories I have are camping on the north shore every summer with my friends,” says Grande. “I loved being in ‘ke kai’ (the sea) and ‘ma uka,’ (inland, in the mountains) with my friends when I was younger. It was just pure fun exploring ‘ʻāina’ like that.” “‘Āina” in the Hawaiian language is often defined as “land,” but is understood to the people of Hawaiʻi as “that which feeds.”

      “Now that I’m older,” Grande adds, “I’m connecting the dots and realizing how much knowledge about the complex systems of ‘ahupuaʻa’ [traditional Hawaiian divisions of land that extend from the mountains to the sea], I actually gained through these experiences.”

      Grande recently completed a year of fieldwork in Hawaiʻi where she volunteered with land-based, or ‘āina-based organizations. In the movement to restore ‘āina to “momona,” or  “fertile and abundant lands,” the land and the people who serve as its stewards are of equal importance.

      “I’m looking at how people who are not Kanaka ‘Ōiwi, or native Hawaiian, by descent can participate in this kind of restoration, and what it means for both Kanaka ‘Ōiwi and non-Kanaka ‘Ōiwi to participate in it,” says Grande, who herself descends from immigrants of other island nations. “Some of my ancestors were born and raised in Hawaiʻi before the U.S. subjected Hawaiʻi as a state and territory, meaning that some of them were Hawaiian Kingdom subjects. While, I am not Kanaka ʻŌiwi by lineage, some of my ‘ohana nui (extended family), from these same ancestors, are Kanaka ʻŌiwi. I’m writing about how being Hawaiian, from a Hawaiian sovereignty standpoint, is not just about race and ethnicity. When Hawaiʻi was a sovereign nation, Hawaiian citizenship was never afforded on the basis of race alone. It was also based on your lifelong commitment to ‘āina and the people of Hawaiʻi.”

      The project is personal to Grande, who describes both the content and the process of writing it as part of her healing journey. She hopes to lay the groundwork for others who are “hoaʻāina,” or “those who actively care for ʻāina,” in Hawaiʻi, but not Kanaka ʻŌiwi to better articulate their identities and foster a deeper connection with the ʻāina and the “kaiāulu,” or “community,” they love and actively care for.

      Returning home

      Grande has spent her academic career on the East Coast, first at Brown University, where she received a degree in science, technology, and society, and now at MIT in the HASTS program. She swam competitively through her second year of college, and had earlier represented Hawaiʻi at the 2012 Oceania Games in New Caledonia. Once she stopped swimming, Grande first used her newfound time to travel the world. Tired of this transient lifestyle, she realized she was more interested in exploring her connection to land in a more rooted way.

      “Moving around, especially as a college student, it’s very hard to grow things,” says Grande. “People are a lot like plants. You really just need to let plants do their thing in place. We do really well and we thrive when we can be connected to place.”

      Grande started by founding the Ethnobotany Society at Brown to explore the relationship people have to plants. With the group she organized nature walks, collaborated with local farms, and connected it to the history she was learning in class.

      Still, the East Coast never quite felt like home to Grande. When she started planning for the fieldwork portion of her program, she envisioned spending half the year in New England and half in Hawaiʻi. But she soon realized how important it was for both her research and herself to dedicate everything to Hawai’i.

      “When I came back, it just felt so right to be back home,” says Grande. “The feeling in your naʻau — your ‘gut’ — of knowing that you have to contribute to Hawaiʻi is very powerful, and I think a lot of people here understand what that means. It’s kind of like a calling.”

      Hoaʻāina, community, family

      Once Grande made the decision to return home for her field work, she says everything fell into place.

      “I knew that I wanted to do something close to my heart. It’s a huge privilege because I was able to come home and learn more about myself and my family and how we are connected to Hawaiʻi,” she says.

      During her year of fieldwork, Grande learned how hoaʻāina cultivate spaces where the community can can work alongside one another to plant traditional food and medicinal crops, control invasive species, and more. She wasn’t just an observer, either. As much as Grande learned from an academic perspective, her personal growth has been intertwined with the entire process.

      “The most interesting part was that all the hoaʻāina I volunteered with helped me to understand my place back home,” says Grande. “They were my informants but also — this usually happens with anthropologists — people become your friends. The hoaʻāina I volunteered with treated me like family. They also got to know some of my family members, who joined me to volunteer at different sites. It’s sometimes hard to drop a hard line between what fieldwork is and what your personal life is because when you’re in the field, there’s so many events that are connected to your work. It was so fun and meaningful to write about the ʻāina and people I consider my community and family.”

      The movement doesn’t start or end with Grande’s dissertation. Pursuing this project has given her the language to articulate her own relationship with ‘āina, and she hopes it will empower others to reexamine how they exist in relation to land.

      After completing her program, Grande intends to stay in Hawaiʻi and continue philanthropy work while contributing to the movement of ʻāina momona.

      “We want the land to live and to keep a relationship with the land. That’s the emotional part. I have a ‘kuleana,’ (duty and responsibility) to everything that I learned while growing up, including the ʻāina and ‘kaiāulu,’ (community) who raised me. The more you learn, there’s so much that you want to protect about the culture and this ‘āina.” More

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      in Environment

      Ancient Amazonians intentionally created fertile “dark earth”

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      The Amazon river basin is known for its immense and lush tropical forests, so one might assume that the Amazon’s land is equally rich. In fact, the soils underlying the forested vegetation, particularly in the hilly uplands, are surprisingly infertile. Much of the Amazon’s soil is acidic and low in nutrients, making it notoriously difficult to farm.

      But over the years, archaeologists have dug up mysteriously black and fertile patches of ancient soils in hundreds of sites across the Amazon. This “dark earth” has been found in and around human settlements dating back hundreds to thousands of years. And it has been a matter of some debate as to whether the super-rich soil was purposefully created or a coincidental byproduct of these ancient cultures.

      Now, a study led by researchers at MIT, the University of Florida, and in Brazil aims to settle the debate over dark earth’s origins. The team has pieced together results from soil analyses, ethnographic observations, and interviews with modern Indigenous communities, to show that dark earth was intentionally produced by ancient Amazonians as a way to improve the soil and sustain large and complex societies.

      “If you want to have large settlements, you need a nutritional base. But the soil in the Amazon is extensively leached of nutrients, and naturally poor for growing most crops,” says Taylor Perron, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences at MIT. “We argue here that people played a role in creating dark earth, and intentionally modified the ancient environment to make it a better place for human populations.”

      And as it turns out, dark earth contains huge amounts of stored carbon. As generations worked the soil, for instance by enriching it with scraps of food, charcoal, and waste, the earth accumulated the carbon-rich detritus and kept it locked up for hundreds to thousands of years. By purposely producing dark earth, then, early Amazonians may have also unintentionally created a powerful, carbon-sequestering soil.

      “The ancient Amazonians put a lot of carbon in the soil, and a lot of that is still there today,” says co-author Samuel Goldberg, who performed the data analysis as a graduate student at MIT and is now an assistant professor at the University of Miami. “That’s exactly what we want for climate change mitigation efforts. Maybe we could adapt some of their indigenous strategies on a larger scale, to lock up carbon in soil, in ways that we now know would stay there for a long time.”

      The team’s study appears today in Science Advances. Other authors include former MIT postdoc and lead author Morgan Schmidt, anthropologist Michael Heckenberger of the University of Florida, and collaborators from multiple institutions across Brazil.

      Modern intent

      In their current study, the team synthesized observations and data that Schmidt, Heckenberger, and others had previously gathered, while working with Indigenous communities in the Amazon since the early 2000s,  with new data collected in 2018-19. The scientists focused their fieldwork in the Kuikuro Indigenous Territory in the Upper Xingu River basin in the southeastern Amazon. This region is home to modern Kuikuro villages as well as archaeological sites where the ancestors of the Kuikuro are thought to have lived. Over multiple visits to the region, Schmidt, then a graduate student at the University of Florida, was struck by the darker soil around some archaeological sites.

      “When I saw this dark earth and how fertile it was, and started digging into what was known about it, I found it was a mysterious thing — no one really knew where it came from,” he says.

      Schmidt and his colleagues began making observations of the modern Kuikuro’s practices of managing the soil. These practices include generating “middens” — piles of waste and food scraps, similar to compost heaps, that are maintained in certain locations around the center of a village. After some time, these waste piles decompose and mix with the soil to form a dark and fertile earth, that residents then use to plant crops. The researchers also observed that Kuikuro farmers spread organic waste and ash on farther fields, which also generates dark earth, where they can then grow more crops.

      “We saw activities they did to modify the soil and increase the elements, like spreading ash on the ground, or spreading charcoal around the base of the tree, which were obviously intentional actions,” Schmidt says.

      In addition to these observations, they also conducted interviews with villagers to document the Kuikuro’s beliefs and practices relating to dark earth. In some of these interviews, villagers referred to dark earth as “eegepe,” and described their daily practices in creating and cultivating the rich soil to improve its agricultural potential.

      Based on these observations and interviews with the Kuikuro, it was clear that Indigenous communities today intentionally produce dark earth, through their practices to improve the soil. But could the dark earth found in nearby archaeological sites have been made through similar intentional practices?

      A bridge in soil

      In search of a connection, Schmidt joined Perron’s group as a postdoc at MIT. Together, he, Perron, and Goldberg carried out a meticulous analysis of soils in both archaeological and modern sites in the Upper Xingu region. They discovered similarities in dark earth’s spatial structure: Deposits of dark earth were found in a radial pattern, concentrating mostly in the center of both modern and ancient settlements, and stretching, like spokes of a wheel, out to the edges. Modern and ancient dark earth was also similar in composition, and was enriched in the same elements, such as carbon, phosphorus, and other nutrients.

      “These are all the elements that are in humans, animals, and plants, and they’re the ones that reduce the aluminum toxicity in soil, which is a notorious problem in the Amazon,” Schmidt says. “All these elements make the soil better for plant growth.”

      “The key bridge between the modern and ancient times is the soil,” Goldberg adds. “Because we see this correspondence between the two time periods, we can infer that these practices that we can observe and ask people about today, were also happening in the past.”

      In other words, the team was able to show for the first time that ancient Amazonians intentionally worked the soil, likely through practices similar to today’s, in order to grow enough crops to sustain large communities.

      Going a step further, the team calculated the amount of carbon in ancient dark earth. They combined their measurements of soil samples, with maps of where dark earth has been found through several ancient settlements. Their estimates revealed that each ancient village contains several thousand tons of carbon that has been sequestered in the soil for hundreds of years as a result of Indigenous, human activities.

      As the team concludes in their paper, “modern sustainable agriculture and climate change mitigation efforts, inspired by the persistent fertility of ancient dark earth, can draw on traditional methods practiced to this day by Indigenous Amazonians.”

      This research at MIT was supported, in part, by the Abdul Latif Jameel Water and Food Systems Lab and the Department of the Air Force Artificial Intelligence Accelerator. Field research was supported by grants to the University of Florida from the National Science Foundation, the Wenner-Gren Foundation and the William Talbott Hillman Foundation, and was sponsored in Brazil by the Museu Goeldi and Museu Nacional. More

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      in Environment

      AI pilot programs look to reduce energy use and emissions on MIT campus

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      Smart thermostats have changed the way many people heat and cool their homes by using machine learning to respond to occupancy patterns and preferences, resulting in a lower energy draw. This technology — which can collect and synthesize data — generally focuses on single-dwelling use, but what if this type of artificial intelligence could dynamically manage the heating and cooling of an entire campus? That’s the idea behind a cross-departmental effort working to reduce campus energy use through AI building controls that respond in real-time to internal and external factors. 

      Understanding the challenge

      Heating and cooling can be an energy challenge for campuses like MIT, where existing building management systems (BMS) can’t respond quickly to internal factors like occupancy fluctuations or external factors such as forecast weather or the carbon intensity of the grid. This results in using more energy than needed to heat and cool spaces, often to sub-optimal levels. By engaging AI, researchers have begun to establish a framework to understand and predict optimal temperature set points (the temperature at which a thermostat has been set to maintain) at the individual room level and take into consideration a host of factors, allowing the existing systems to heat and cool more efficiently, all without manual intervention. 

      “It’s not that different from what folks are doing in houses,” explains Les Norford, a professor of architecture at MIT, whose work in energy studies, controls, and ventilation connected him with the effort. “Except we have to think about things like how long a classroom may be used in a day, weather predictions, time needed to heat and cool a room, the effect of the heat from the sun coming in the window, and how the classroom next door might impact all of this.” These factors are at the crux of the research and pilots that Norford and a team are focused on. That team includes Jeremy Gregory, executive director of the MIT Climate and Sustainability Consortium; Audun Botterud, principal research scientist for the Laboratory for Information and Decision Systems; Steve Lanou, project manager in the MIT Office of Sustainability (MITOS); Fran Selvaggio, Department of Facilities Senior Building Management Systems engineer; and Daisy Green and You Lin, both postdocs.

      The group is organized around the call to action to “explore possibilities to employ artificial intelligence to reduce on-campus energy consumption” outlined in Fast Forward: MIT’s Climate Action Plan for the Decade, but efforts extend back to 2019. “As we work to decarbonize our campus, we’re exploring all avenues,” says Vice President for Campus Services and Stewardship Joe Higgins, who originally pitched the idea to students at the 2019 MIT Energy Hack. “To me, it was a great opportunity to utilize MIT expertise and see how we can apply it to our campus and share what we learn with the building industry.” Research into the concept kicked off at the event and continued with undergraduate and graduate student researchers running differential equations and managing pilots to test the bounds of the idea. Soon, Gregory, who is also a MITOS faculty fellow, joined the project and helped identify other individuals to join the team. “My role as a faculty fellow is to find opportunities to connect the research community at MIT with challenges MIT itself is facing — so this was a perfect fit for that,” Gregory says. 

      Early pilots of the project focused on testing thermostat set points in NW23, home to the Department of Facilities and Office of Campus Planning, but Norford quickly realized that classrooms provide many more variables to test, and the pilot was expanded to Building 66, a mixed-use building that is home to classrooms, offices, and lab spaces. “We shifted our attention to study classrooms in part because of their complexity, but also the sheer scale — there are hundreds of them on campus, so [they offer] more opportunities to gather data and determine parameters of what we are testing,” says Norford. 

      Developing the technology

      The work to develop smarter building controls starts with a physics-based model using differential equations to understand how objects can heat up or cool down, store heat, and how the heat may flow across a building façade. External data like weather, carbon intensity of the power grid, and classroom schedules are also inputs, with the AI responding to these conditions to deliver an optimal thermostat set point each hour — one that provides the best trade-off between the two objectives of thermal comfort of occupants and energy use. That set point then tells the existing BMS how much to heat up or cool down a space. Real-life testing follows, surveying building occupants about their comfort. Botterud, whose research focuses on the interactions between engineering, economics, and policy in electricity markets, works to ensure that the AI algorithms can then translate this learning into energy and carbon emission savings. 

      Currently the pilots are focused on six classrooms within Building 66, with the intent to move onto lab spaces before expanding to the entire building. “The goal here is energy savings, but that’s not something we can fully assess until we complete a whole building,” explains Norford. “We have to work classroom by classroom to gather the data, but are looking at a much bigger picture.” The research team used its data-driven simulations to estimate significant energy savings while maintaining thermal comfort in the six classrooms over two days, but further work is needed to implement the controls and measure savings across an entire year. 

      With significant savings estimated across individual classrooms, the energy savings derived from an entire building could be substantial, and AI can help meet that goal, explains Botterud: “This whole concept of scalability is really at the heart of what we are doing. We’re spending a lot of time in Building 66 to figure out how it works and hoping that these algorithms can be scaled up with much less effort to other rooms and buildings so solutions we are developing can make a big impact at MIT,” he says.

      Part of that big impact involves operational staff, like Selvaggio, who are essential in connecting the research to current operations and putting them into practice across campus. “Much of the BMS team’s work is done in the pilot stage for a project like this,” he says. “We were able to get these AI systems up and running with our existing BMS within a matter of weeks, allowing the pilots to get off the ground quickly.” Selvaggio says in preparation for the completion of the pilots, the BMS team has identified an additional 50 buildings on campus where the technology can easily be installed in the future to start energy savings. The BMS team also collaborates with the building automation company, Schneider Electric, that has implemented the new control algorithms in Building 66 classrooms and is ready to expand to new pilot locations. 

      Expanding impact

      The successful completion of these programs will also open the possibility for even greater energy savings — bringing MIT closer to its decarbonization goals. “Beyond just energy savings, we can eventually turn our campus buildings into a virtual energy network, where thousands of thermostats are aggregated and coordinated to function as a unified virtual entity,” explains Higgins. These types of energy networks can accelerate power sector decarbonization by decreasing the need for carbon-intensive power plants at peak times and allowing for more efficient power grid energy use.

      As pilots continue, they fulfill another call to action in Fast Forward — for campus to be a “test bed for change.” Says Gregory: “This project is a great example of using our campus as a test bed — it brings in cutting-edge research to apply to decarbonizing our own campus. It’s a great project for its specific focus, but also for serving as a model for how to utilize the campus as a living lab.” More

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      in Energy

      Jackson Jewett wants to design buildings that use less concrete

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      After three years leading biking tours through U.S. National Parks, Jackson Jewett decided it was time for a change.

      “It was a lot of fun, but I realized I missed buildings,” says Jewett. “I really wanted to be a part of that industry, learn more about it, and reconnect with my roots in the built environment.”

      Jewett grew up in California in what he describes as a “very creative household.”

      “I remember making very elaborate Halloween costumes with my parents, making fun dioramas for school projects, and building forts in the backyard, that kind of thing,” Jewett explains.

      Both of his parents have backgrounds in design; his mother studied art in college and his father is a practicing architect. From a young age, Jewett was interested in following in his father’s footsteps. But when he arrived at the University of California at Berkeley in the midst of the 2009 housing crash, it didn’t seem like the right time. Jewett graduated with a degree in cognitive science and a minor in history of architecture. And even as he led tours through Yellowstone, the Grand Canyon, and other parks, buildings were in the back of his mind.

      It wasn’t just the built environment that Jewett was missing. He also longed for the rigor and structure of an academic environment.

      Jewett arrived at MIT in 2017, initially only planning on completing the master’s program in civil and environmental engineering. It was then that he first met Josephine Carstensen, a newly hired lecturer in the department. Jewett was interested in Carstensen’s work on “topology optimization,” which uses algorithms to design structures that can achieve their performance requirements while using only a limited amount of material. He was particularly interested in applying this approach to concrete design, and he collaborated with Carstensen to help demonstrate its viability.

      After earning his master’s, Jewett spent a year and a half as a structural engineer in New York City. But when Carstensen was hired as a professor, she reached out to Jewett about joining her lab as a PhD student. He was ready for another change.

      Now in the third year of his PhD program, Jewett’s dissertation work builds upon his master’s thesis to further refine algorithms that can design building-scale concrete structures that use less material, which would help lower carbon emissions from the construction industry. It is estimated that the concrete industry alone is responsible for 8 percent of global carbon emissions, so any efforts to reduce that number could help in the fight against climate change.

      Implementing new ideas

      Topology optimization is a small field, with the bulk of the prior work being computational without any experimental verification. The work Jewett completed for his master’s thesis was just the start of a long learning process.

      “I do feel like I’m just getting to the part where I can start implementing my own ideas without as much support as I’ve needed in the past,” says Jewett. “In the last couple of months, I’ve been working on a reinforced concrete optimization algorithm that I hope will be the cornerstone of my thesis.”

      The process of fine-tuning a generative algorithm is slow going, particularly when tackling a multifaceted problem.

      “It can take days or usually weeks to take a step toward making it work as an entire integrated system,” says Jewett. “The days when that breakthrough happens and I can see the algorithm converging on a solution that makes sense — those are really exciting moments.”

      By harnessing computational power, Jewett is searching for materially efficient components that can be used to make up structures such as bridges or buildings. These are other constraints to consider as well, particularly ensuring that the cost of manufacturing isn’t too high. Having worked in the industry before starting the PhD program, Jewett has an eye toward doing work that can be feasibly implemented.

      Inspiring others

      When Jewett first visited MIT campus, he was drawn in by the collaborative environment of the institute and the students’ drive to learn. Now, he’s a part of that process as a teaching assistant and a supervisor in the Undergraduate Research Opportunities Program.  

      Working as a teaching assistant isn’t a requirement for Jewett’s program, but it’s been one of his favorite parts of his time at MIT.

      “The MIT undergrads are so gifted and just constantly impress me,” says Jewett. “Being able to teach, especially in the context of what MIT values is a lot of fun. And I learn, too. My coding practices have gotten so much better since working with undergrads here.”

      Jewett’s experiences have inspired him to pursue a career in academia after the completion of his program, which he expects to complete in the spring of 2025. But he’s making sure to take care of himself along the way. He still finds time to plan cycling trips with his friends and has gotten into running ever since moving to Boston. So far, he’s completed two marathons.

      “It’s so inspiring to be in a place where so many good ideas are just bouncing back and forth all over campus,” says Jewett. “And on most days, I remember that and it inspires me. But it’s also the case that academics is hard, PhD programs are hard, and MIT — there’s pressure being here, and sometimes that pressure can feel like it’s working against you.”

      Jewett is grateful for the mental health resources that MIT provides students. While he says it can be imperfect, it’s been a crucial part of his journey.

      “My PhD thesis will be done in 2025, but the work won’t be done. The time horizon of when these things need to be implemented is relatively short if we want to make an impact before global temperatures have already risen too high. My PhD research will be developing a framework for how that could be done with concrete construction, but I’d like to keep thinking about other materials and construction methods even after this project is finished.” More

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      in Environment

      Harnessing hydrogen’s potential to address long-haul trucking emissions

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      The transportation of goods forms the basis of today’s globally distributed supply chains, and long-haul trucking is a central and critical link in this complex system. To meet climate goals around the world, it is necessary to develop decarbonized solutions to replace diesel powertrains, but given trucking’s indispensable and vast role, these solutions must be both economically viable and practical to implement. While hydrogen-based options, as an alternative to diesel, have the potential to become a promising decarbonization strategy, hydrogen has significant limitations when it comes to delivery and refueling.These roadblocks, combined with hydrogen’s compelling decarbonization potential, are what motivated a team of MIT researchers led by William H. Green, the Hoyt Hottel Professor in Chemical Engineering, to explore a cost-effective way to transport and store hydrogen using liquid organic hydrogen carriers (LOHCs). The team is developing a disruptive technology that allows LOHCs to not only deliver the hydrogen to the trucks, but also store the hydrogen onboard.Their findings were recently published in Energy and Fuels, a peer-reviewed journal of the American Chemical Society, in a paper titled “Perspective on Decarbonizing Long-Haul Trucks Using Onboard Dehydrogenation of Liquid Organic Hydrogen Carriers.” The MIT team is led by Green, and includes graduate students Sayandeep Biswas and Kariana Moreno Sader. Their research is supported by the MIT Climate and Sustainability Consortium (MCSC) through its Seed Awards program and MathWorks, and ties into the work within the MCSC’s Tough Transportation Modes focus area.An “onboard” approachCurrently, LOHCs, which work within existing retail fuel distribution infrastructure, are used to deliver hydrogen gas to refueling stations, where it is then compressed and delivered onto trucks equipped with hydrogen fuel cell or combustion engines.“This current approach incurs significant energy loss due to endothermic hydrogen release and compression at the retail station” says Green. “To address this, our work is exploring a more efficient application, with LOHC-powered trucks featuring onboard dehydrogenation.”To implement such a design, the team aims to modify the truck’s powertrain (the system inside a vehicle that produces the energy to propel it forward) to allow onboard hydrogen release from the LOHCs, using waste heat from the engine exhaust to power the “dehydrogenation” process. 

      Proposed process flow diagram for onboard dehydrogenation. Component sizes are not to scale and have been enlarged for illustrative purposes.

      Image courtesy of the Green Group.

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      The dehydrogenation process happens within a high-temperature reactor, which continually receives hydrogen-rich LOHCs from the fuel storage tank. Hydrogen released from the reactor is fed to the engine, after passing through a separator to remove any lingering LOHC. On its way to the engine, some of the hydrogen gets diverted to a burner to heat the reactor, which helps to augment the reactor heating provided by the engine exhaust gases.Acknowledging and addressing hydrogen’s drawbacksThe team’s paper underscores that current uses of hydrogen, including LOHC systems, to decarbonize the trucking sector have drawbacks. Regardless of technical improvements, these existing options remain prohibitively expensive due to the high cost of retail hydrogen delivery.“We present an alternative option that addresses a lot of the challenges and seems to be a viable way in which hydrogen can be used in this transportation context,” says Biswas, who was recently elected to the MIT Martin Family Society of Fellows for Sustainability for his work in this area. “Hydrogen, when used through LOHCs, has clear benefits for long-hauling, such as scalability and fast refueling time. There is also an enormous potential to improve delivery and refueling to further reduce cost, and our system is working to do that.”“Utilizing hydrogen is an option that is globally accessible, and could be extended to countries like the one where I am from,” says Moreno Sader, who is originally from Colombia. “Since it synergizes with existing infrastructure, large upfront investments are not necessary. The global applicability is huge.”Moreno Sader is a MathWorks Fellow, and, along with the rest of the team, has been using MATLAB tools to develop models and simulations for this work.Different sectors coming togetherDecarbonizing transportation modes, including long-haul trucking, requires expertise and perspectives from different industries — an approach that resonates with the MCSC’s mission.The team’s groundbreaking research into LOHC-powered trucking is among several projects supported by the MCSC within its Tough Transportation Modes focus area, led by postdoc Impact Fellow Danika MacDonell. The MCSC-supported projects were chosen to tackle a complementary set of societally important and industry-relevant challenges to decarbonizing heavy-duty transportation, which span a range of sectors and solution pathways. Other projects focus, for example, on logistics optimization for electrified trucking fleets, or air quality and climate impacts of ammonia-powered shipping.The MCSC works to support and amplify the impact of these projects by engaging the research teams with industry partners from a variety of sectors. In addition, the MCSC pursues a collective multisectoral approach to decarbonizing transportation by facilitating shared learning across the different projects through regular cross-team discussion.The research led by Green celebrates this cross-sector theme by integrating industry-leading computing tools provided by MathWorks with cutting-edge developments in chemical engineering, as well as industry-leading commercial LOHC reactor demonstrations, to build a compelling vision for cost-effective LOHC-powered trucking.The review and research conducted in the Energy and Fuels article lays the groundwork for further investigations into LOHC-powered truck design. The development of such a vehicle — with a power-dense, efficient, and robust onboard hydrogen release system — requires dedicated investigations and further optimization of core components geared specifically toward the trucking application. More