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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

    • 63 Shares189 Views

      in Energy

      Making aviation fuel from biomass

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      In 2021, nearly a quarter of the world’s carbon dioxide emissions came from the transportation sector, with aviation being a significant contributor. While the growing use of electric vehicles is helping to clean up ground transportation, today’s batteries can’t compete with fossil fuel-derived liquid hydrocarbons in terms of energy delivered per pound of weight — a major concern when it comes to flying. Meanwhile, based on projected growth in travel demand, consumption of jet fuel is projected to double between now and 2050 — the year by which the international aviation industry has pledged to be carbon neutral.

      Many groups have targeted a 100 percent sustainable hydrocarbon fuel for aircraft, but without much success. Part of the challenge is that aviation fuels are so tightly regulated. “This is a subclass of fuels that has very specific requirements in terms of the chemistry and the physical properties of the fuel, because you can’t risk something going wrong in an airplane engine,” says Yuriy Román-Leshkov, the Robert T. Haslam Professor of Chemical Engineering. “If you’re flying at 30,000 feet, it’s very cold outside, and you don’t want the fuel to thicken or freeze. That’s why the formulation is very specific.”

      Aviation fuel is a combination of two large classes of chemical compounds. Some 75 to 90 percent of it is made up of “aliphatic” molecules, which consist of long chains of carbon atoms linked together. “This is similar to what we would find in diesel fuels, so it’s a classic hydrocarbon that is out there,” explains Román-Leshkov. The remaining 10 to 25 percent consists of “aromatic” molecules, each of which includes at least one ring made up of six connected carbon atoms.

      In most transportation fuels, aromatic hydrocarbons are viewed as a source of pollution, so they’re removed as much as possible. However, in aviation fuels, some aromatic molecules must remain because they set the necessary physical and combustion properties of the overall mixture. They also perform one more critical task: They ensure that seals between various components in the aircraft’s fuel system are tight. “The aromatics get absorbed by the plastic seals and make them swell,” explains Román-Leshkov. “If for some reason the fuel changes, so can the seals, and that’s very dangerous.”

      As a result, aromatics are a necessary component — but they’re also a stumbling block in the move to create sustainable aviation fuels, or SAFs. Companies know how to make the aliphatic fraction from inedible parts of plants and other renewables, but they haven’t yet developed an approved method of generating the aromatic fraction from sustainable sources. As a result, there’s a “blending wall,” explains Román-Leshkov. “Since we need that aromatic content — regardless of its source — there will always be a limit on how much of the sustainable aliphatic hydrocarbons we can use without changing the properties of the mixture.” He notes a similar blending wall with gasoline. “We have a lot of ethanol, but we can’t add more than 10 percent without changing the properties of the gasoline. In fact, current engines can’t handle even 15 percent ethanol without modification.”

      No shortage of renewable source material — or attempts to convert it

      For the past five years, understanding and solving the SAF problem has been the goal of research by Román-Leshkov and his MIT team — Michael L. Stone PhD ’21, Matthew S. Webber, and others — as well as their collaborators at Washington State University, the National Renewable Energy Laboratory (NREL), and the Pacific Northwest National Laboratory. Their work has focused on lignin, a tough material that gives plants structural support and protection against microbes and fungi. About 30 percent of the carbon in biomass is in lignin, yet when ethanol is generated from biomass, the lignin is left behind as a waste product.

      Despite valiant efforts, no one has found an economically viable, scalable way to turn lignin into useful products, including the aromatic molecules needed to make jet fuel 100 percent sustainable. Why not? As Román-Leshkov says, “It’s because of its chemical recalcitrance.” It’s difficult to make it chemically react in useful ways. As a result, every year millions of tons of waste lignin are burned as a low-grade fuel, used as fertilizer, or simply thrown away.

      Understanding the problem requires understanding what’s happening at the atomic level. A single lignin molecule — the starting point of the challenge — is a big “macromolecule” made up of a network of many aromatic rings connected by oxygen and hydrogen atoms. Put simply, the key to converting lignin into the aromatic fraction of SAF is to break that macromolecule into smaller pieces while in the process getting rid of all of the oxygen atoms.

      In general, most industrial processes begin with a chemical reaction that prevents the subsequent upgrading of lignin: As the lignin is extracted from the biomass, the aromatic molecules in it react with one another, linking together to form strong networks that won’t react further. As a result, the lignin is no longer useful for making aviation fuels.

      To avoid that outcome, Román-Leshkov and his team utilize another approach: They use a catalyst to induce a chemical reaction that wouldn’t normally occur during extraction. By reacting the biomass in the presence of a ruthenium-based catalyst, they are able to remove the lignin from the biomass and produce a black liquid called lignin oil. That product is chemically stable, meaning that the aromatic molecules in it will no longer react with one another.

      So the researchers have now successfully broken the original lignin macromolecule into fragments that contain just one or two aromatic rings each. However, while the isolated fragments don’t chemically react, they still contain oxygen atoms. Therefore, one task remains: finding a way to remove the oxygen atoms.

      In fact, says Román-Leshkov, getting from the molecules in the lignin oil to the targeted aromatic molecules required them to accomplish three things in a single step: They needed to selectively break the carbon-oxygen bonds to free the oxygen atoms; they needed to avoid incorporating noncarbon atoms into the aromatic rings (for example, atoms from the hydrogen gas that must be present for all of the chemical transformations to occur); and they needed to preserve the carbon backbone of the molecule — that is, the series of linked carbon atoms that connect the aromatic rings that remain.

      Ultimately, Román-Leshkov and his team found a special ingredient that would do the trick: a molybdenum carbide catalyst. “It’s actually a really amazing catalyst because it can perform those three actions very well,” says Román-Leshkov. “In addition to that, it’s extremely resistant to poisons. Plants can contain a lot of components like proteins, salts, and sulfur, which often poison catalysts so they don’t work anymore. But molybdenum carbide is very robust and isn’t strongly influenced by such impurities.”

      Trying it out on lignin from poplar trees

      To test their approach in the lab, the researchers first designed and built a specialized “trickle-bed” reactor, a type of chemical reactor in which both liquids and gases flow downward through a packed bed of catalyst particles. They then obtained biomass from a poplar, a type of tree known as an “energy crop” because it grows quickly and doesn’t require a lot of fertilizer.

      To begin, they reacted the poplar biomass in the presence of their ruthenium-based catalyst to extract the lignin and produce the lignin oil. They then flowed the oil through their trickle-bed reactor containing the molybdenum carbide catalyst. The mixture that formed contained some of the targeted product but also a lot of others that still contained oxygen atoms.

      Román-Leshkov notes that in a trickle-bed reactor, the time during which the lignin oil is exposed to the catalyst depends entirely on how quickly it drips down through the packed bed. To increase the exposure time, they tried passing the oil through the same catalyst twice. However, the distribution of products that formed in the second pass wasn’t as they had predicted based on the outcome of the first pass.

      With further investigation, they figured out why. The first time the lignin oil drips through the reactor, it deposits oxygen onto the catalyst. The deposition of the oxygen changes the behavior of the catalyst such that certain products appear or disappear — with the temperature being critical. “The temperature and oxygen content set the condition of the catalyst in the first pass,” says Román-Leshkov. “Then, on the second pass, the oxygen content in the flow is lower, and the catalyst can fully break the remaining carbon-oxygen bonds.” The process can thus operate continuously: Two separate reactors containing independent catalyst beds would be connected in series, with the first pretreating the lignin oil and the second removing any oxygen that remains.

      Based on a series of experiments involving lignin oil from poplar biomass, the researchers determined the operating conditions yielding the best outcome: 350 degrees Celsius in the first step and 375 C in the second step. Under those optimized conditions, the mixture that forms is dominated by the targeted aromatic products, with the remainder consisting of small amounts of other jet-fuel aliphatic molecules and some remaining oxygen-containing molecules. The catalyst remains stable while generating more than 87 percent (by weight) of aromatic molecules.

      “When we do our chemistry with the molybdenum carbide catalyst, our total carbon yields are nearly 85 percent of the theoretical carbon yield,” says Román-Leshkov. “In most lignin-conversion processes, the carbon yields are very low, on the order of 10 percent. That’s why the catalysis community got very excited about our results — because people had not seen carbon yields as high as the ones we generated with this catalyst.”

      There remains one key question: Does the mixture of components that forms have the properties required for aviation fuel? “When we work with these new substrates to make new fuels, the blend that we create is different from standard jet fuel,” says Román-Leshkov. “Unless it has the exact properties required, it will not qualify for certification as jet fuel.”

      To check their products, Román-Leshkov and his team send samples to Washington State University, where a team operates a combustion lab devoted to testing fuels. Results from initial testing of the composition and properties of the samples have been encouraging. Based on the composition and published prescreening tools and procedures, the researchers have made initial property predictions for their samples, and they looked good. For example, the freezing point, viscosity, and threshold sooting index are predicted to be lower than the values for conventional aviation aromatics. (In other words, their material should flow more easily and be less likely to freeze than conventional aromatics while also generating less soot in the atmosphere when they burn.) Overall, the predicted properties are near to or more favorable than those of conventional fuel aromatics.

      Next steps

      The researchers are continuing to study how their sample blends behave at different temperatures and, in particular, how well they perform that key task: soaking into and swelling the seals inside jet engines. “These molecules are not the typical aromatic molecules that you use in jet fuel,” says Román-Leshkov. “Preliminary tests with sample seals show that there’s no difference in how our lignin-derived aromatics swell the seals, but we need to confirm that. There’s no room for error.”

      In addition, he and his team are working with their NREL collaborators to scale up their methods. NREL has much larger reactors and other infrastructure needed to produce large quantities of the new sustainable blend. Based on the promising results thus far, the team wants to be prepared for the further testing required for the certification of jet fuels. In addition to testing samples of the fuel, the full certification procedure calls for demonstrating its behavior in an operating engine — “not while flying, but in a lab,” clarifies Román-Leshkov. In addition to requiring large samples, that demonstration is both time-consuming and expensive — which is why it’s the very last step in the strict testing required for a new sustainable aviation fuel to be approved.

      Román-Leshkov and his colleagues are now exploring the use of their approach with other types of biomass, including pine, switchgrass, and corn stover (the leaves, stalks, and cobs left after corn is harvested). But their results with poplar biomass are promising. If further testing confirms that their aromatic products can replace the aromatics now in jet fuel, “the blending wall could disappear,” says Román-Leshkov. “We’ll have a means of producing all the components in aviation fuel from renewable material, potentially leading to aircraft fuel that’s 100 percent sustainable.”

      This research was initially funded by the Center for Bioenergy Innovation, a U.S. Department of Energy (DOE) Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. More recent funding came from the DOE Bioenergy Technologies Office and from Eni S.p.A. through the MIT Energy Initiative. Michael L. Stone PhD ’21 is now a postdoc in chemical engineering at Stanford University. Matthew S. Webber is a graduate student in the Román-Leshkov group, now on leave for an internship at the National Renewable Energy Laboratory.

      This article appears in the Spring 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More

    • 88 Shares179 Views

      in Environment

      The curse of variety in transportation systems

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      Cathy Wu has always delighted in systems that run smoothly. In high school, she designed a project to optimize the best route for getting to class on time. Her research interests and career track are evidence of a propensity for organizing and optimizing, coupled with a strong sense of responsibility to contribute to society instilled by her parents at a young age.

      As an undergraduate at MIT, Wu explored domains like agriculture, energy, and education, eventually homing in on transportation. “Transportation touches each of our lives,” she says. “Every day, we experience the inefficiencies and safety issues as well as the environmental harms associated with our transportation systems. I believe we can and should do better.”

      But doing so is complicated. Consider the long-standing issue of traffic systems control. Wu explains that it is not one problem, but more accurately a family of control problems impacted by variables like time of day, weather, and vehicle type — not to mention the types of sensing and communication technologies used to measure roadway information. Every differentiating factor introduces an exponentially larger set of control problems. There are thousands of control-problem variations and hundreds, if not thousands, of studies and papers dedicated to each problem. Wu refers to the sheer number of variations as the curse of variety — and it is hindering innovation.

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      “To prove that a new control strategy can be safely deployed on our streets can take years. As time lags, we lose opportunities to improve safety and equity while mitigating environmental impacts. Accelerating this process has huge potential,” says Wu.  

      Which is why she and her group in the MIT Laboratory for Information and Decision Systems are devising machine learning-based methods to solve not just a single control problem or a single optimization problem, but families of control and optimization problems at scale. “In our case, we’re examining emerging transportation problems that people have spent decades trying to solve with classical approaches. It seems to me that we need a different approach.”

      Optimizing intersections

      Currently, Wu’s largest research endeavor is called Project Greenwave. There are many sectors that directly contribute to climate change, but transportation is responsible for the largest share of greenhouse gas emissions — 29 percent, of which 81 percent is due to land transportation. And while much of the conversation around mitigating environmental impacts related to mobility is focused on electric vehicles (EVs), electrification has its drawbacks. EV fleet turnover is time-consuming (“on the order of decades,” says Wu), and limited global access to the technology presents a significant barrier to widespread adoption.

      Wu’s research, on the other hand, addresses traffic control problems by leveraging deep reinforcement learning. Specifically, she is looking at traffic intersections — and for good reason. In the United States alone, there are more than 300,000 signalized intersections where vehicles must stop or slow down before re-accelerating. And every re-acceleration burns fossil fuels and contributes to greenhouse gas emissions.

      Highlighting the magnitude of the issue, Wu says, “We have done preliminary analysis indicating that up to 15 percent of land transportation CO2 is wasted through energy spent idling and re-accelerating at intersections.”

      To date, she and her group have modeled 30,000 different intersections across 10 major metropolitan areas in the United States. That is 30,000 different configurations, roadway topologies (e.g., grade of road or elevation), different weather conditions, and variations in travel demand and fuel mix. Each intersection and its corresponding scenarios represents a unique multi-agent control problem.

      Wu and her team are devising techniques that can solve not just one, but a whole family of problems comprised of tens of thousands of scenarios. Put simply, the idea is to coordinate the timing of vehicles so they arrive at intersections when traffic lights are green, thereby eliminating the start, stop, re-accelerate conundrum. Along the way, they are building an ecosystem of tools, datasets, and methods to enable roadway interventions and impact assessments of strategies to significantly reduce carbon-intense urban driving.

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      Their collaborator on the project is the Utah Department of Transportation, which Wu says has played an essential role, in part by sharing data and practical knowledge that she and her group otherwise would not have been able to access publicly.

      “I appreciate industry and public sector collaborations,” says Wu. “When it comes to important societal problems, one really needs grounding with practitioners. One needs to be able to hear the perspectives in the field. My interactions with practitioners expand my horizons and help ground my research. You never know when you’ll hear the perspective that is the key to the solution, or perhaps the key to understanding the problem.”

      Finding the best routes

      In a similar vein, she and her research group are tackling large coordination problems. For example, vehicle routing. “Every day, delivery trucks route more than a hundred thousand packages for the city of Boston alone,” says Wu. Accomplishing the task requires, among other things, figuring out which trucks to use, which packages to deliver, and the order in which to deliver them as efficiently as possible. If and when the trucks are electrified, they will need to be charged, adding another wrinkle to the process and further complicating route optimization.

      The vehicle routing problem, and therefore the scope of Wu’s work, extends beyond truck routing for package delivery. Ride-hailing cars may need to pick up objects as well as drop them off; and what if delivery is done by bicycle or drone? In partnership with Amazon, for example, Wu and her team addressed routing and path planning for hundreds of robots (up to 800) in their warehouses.

      Every variation requires custom heuristics that are expensive and time-consuming to develop. Again, this is really a family of problems — each one complicated, time-consuming, and currently unsolved by classical techniques — and they are all variations of a central routing problem. The curse of variety meets operations and logistics.

      By combining classical approaches with modern deep-learning methods, Wu is looking for a way to automatically identify heuristics that can effectively solve all of these vehicle routing problems. So far, her approach has proved successful.

      “We’ve contributed hybrid learning approaches that take existing solution methods for small problems and incorporate them into our learning framework to scale and accelerate that existing solver for large problems. And we’re able to do this in a way that can automatically identify heuristics for specialized variations of the vehicle routing problem.” The next step, says Wu, is applying a similar approach to multi-agent robotics problems in automated warehouses.

      Wu and her group are making big strides, in part due to their dedication to use-inspired basic research. Rather than applying known methods or science to a problem, they develop new methods, new science, to address problems. The methods she and her team employ are necessitated by societal problems with practical implications. The inspiration for the approach? None other than Louis Pasteur, who described his research style in a now-famous article titled “Pasteur’s Quadrant.” Anthrax was decimating the sheep population, and Pasteur wanted to better understand why and what could be done about it. The tools of the time could not solve the problem, so he invented a new field, microbiology, not out of curiosity but out of necessity. More

    • 113 Shares99 Views

      in Environment

      Helping the transportation sector adapt to a changing world

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      After graduating from college, Nick Caros took a job as an engineer with a construction company, helping to manage the building of a new highway bridge right near where he grew up outside of Vancouver, British Columbia.  

      “I had a lot of friends that would use that new bridge to get to work,” Caros recalls. “They’d say, ‘You saved me like 20 minutes!’ That’s when I first realized that transportation could be a huge benefit to people’s lives.”

      Now a PhD candidate in the Urban Mobility Lab and the lead researcher for the MIT Transit Research Consortium, Caros works with seven transit agencies across the country to understand how workers’ transportation needs have changed as companies have adopted remote work policies.

      “Another cool thing about working on transportation is that everybody, even if they don’t engage with it on an academic level, has an opinion or wants to talk about it,” says Caros. “As soon as I mention I’ve worked with the T, they have something they want to talk about.”

      Caros is drawn to projects with social impact beyond saving his friends a few minutes during their commutes. He sees public transportation as a crucial component in combating climate change and is passionate about identifying and lowering the psychological barriers that prevent people around the world from taking advantage of their local transit systems.

      “The more I’ve learned about public transportation, the more I’ve come to realize it will play an essential part in decarbonizing urban transportation,” says Caros. “I want to continue working on these kinds of issues, like how we can make transportation more sustainable or promoting public transportation in places where it doesn’t exist or can be improved.”

      Caros says he doesn’t have a “transportation origin story,” like some of his peers who grew up in urban centers with robust public transit systems. As a child growing up in the Vancouver suburbs, he always enjoyed the outdoors, which were as close as his backyard. He chose to study engineering as an undergraduate at the University of British Columbia, fascinated by the hydroelectric dams that supply Vancouver with most of its power. But after two projects with the construction company, the second of which took him to Maryland to work on a fossil fuel project, he decided he needed a change.

      Not quite sure what he wanted to do next, Caros sought out the shortest master’s program he could find that interested him. That ended up being an 18-month master’s program in transportation planning and engineering at New York University. Initially intending to pursue the course-based program, Caros was soon offered the chance to be a research assistant in NYU’s Behavioral Urban Informatics, Logistics, and Transport Laboratory with Professor Joseph Chow. There, he worked to model an experimental transportation system of modular self-driving cars that could link and unlink with each other while in motion.

      “It was this really futuristic stuff,” says Caros. “It turned out to be a really cool project to work on because it’s kind of rare to have a blank-slate problem to try and solve. A lot of transportation engineering problems have largely been solved. We know how to make efficient and sustainable transportation systems; it’s just finding the political support and encouraging behavioral change that remains a challenge.”

      At NYU, Caros fell in love with research and the field of transportation. Later, he was drawn to MIT by its interdisciplinary PhD program that spans both urban studies and planning and civil engineering and the opportunity to work with Professor Jinhua Zhao.

      His research focuses on identifying “third places,” locations where some people go if their job gives them the flexibility to work remotely. Previously, transportation needs revolved around office spaces, typically located in city centers. With more people working from home, the first assumption is that transportation needs would decrease. But that’s not what Caros has found.

      “One major finding from our research is that people have changed where they’re going when they go to work,” says Caros. “A lot of people are working from home, but some are also working in other places, like coffee shops or co-working spaces. And these third places are not evenly distributed in Boston.”

      Identifying the concentration of these third places and what locations would benefit from them is the core of Caros’ dissertation. He’s building an algorithm that identifies ideal locations to build more shared workplaces based on both economic and social factors. Caros seeks to answer how you can minimize travel time across the board while leaving room for the spontaneous social interactions that drive a city’s productivity. His research is sponsored by seven of the largest transit agencies in the United States, who are members of the MIT Transit Research Consortium. Rather than a single agency sponsoring a single specific project, funding is pooled to tackle projects that address general topics that can apply to multiple cities.

      These kinds of problems require a multidisciplinary approach that appeals to Caros. Even when diving into the technical details of a solution, he always keeps the bigger picture in mind. He is certain that changing people’s views of public transportation will be crucial in the fight against climate change.

      “A lot of it is not necessarily engineering, but understanding what the motivations of people are,” says Caros. “Transportation is a leading sector for carbon emissions in the U.S., and so figuring out what makes people tick and how you can get them to ride public transit more, for example, would help to reduce the overall carbon cost.”

      Following the completion of his degree, Caros will join the Organization for Economic Cooperation and Development. He already spent six months at its Paris headquarters as an intern during a leave from MIT, something his lab encourages all of its students to do. Last fall, he worked on drafting policy guidelines for new mobility services such as vehicle-share scooters, and addressing transportation equity issues in Ghana. Plus, living in Paris gave him the opportunity to practice his French. Growing up in Canada, he attended a French immersion school, and his internship offered his first opportunity to use the language outside of an academic context.

      Looking forward, Caros hopes to keep tackling projects that promote sustainable public transportation. There is an urgency in getting ahead of the curve, especially in cities experiencing rapid growth.

      “You kind of get locked in,” says Caros. “It becomes much harder to build sustainable transportation systems after the fact. But it’s really just a geometry problem. Trains and buses are a way more efficient way to move people using the same amount of space as private cars.” More

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      in Environment

      Harnessing synthetic biology to make sustainable alternatives to petroleum products

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      Reducing our reliance on fossil fuels is going to require a transformation in the way we make things. That’s because the hydrocarbons found in fuels like crude oil, natural gas, and coal are also in everyday items like plastics, clothing, and cosmetics.

      Now Visolis, founded by Deepak Dugar SM ’11, MBA ’13, PhD ’13, is combining synthetic biology with chemical catalysis to reinvent the way the world makes things — and reducing gigatons of greenhouse gas emissions in the process.

      The company — which uses a microbe to ferment biomass waste like wood chips and create a molecular building block called mevalonic acid — is more sustainably producing everything from car tires and cosmetics to aviation fuels by tweaking the chemical processes involved to make different byproducts.

      “We started with [the rubber component] isoprene as the main molecule we produce [from mevalonic acid], but we’ve expanded our platform with this unique combination of chemistry and biology that allows us to decarbonize multiple supply chains very rapidly and efficiently,” Dugar explains. “Imagine carbon-negative yoga pants. We can make that happen. Tires can be carbon-negative, personal care can lower its footprint — and we’re already selling into personal care. So in everything from personal care to apparel to industrial goods, our platform is enabling decarbonization of manufacturing.”

      “Carbon-negative” is a term Dugar uses a lot. Visolis has already partnered with some of the world’s largest consumers of isoprene, a precursor to rubber, and now Dugar wants to prove out the company’s process in other emissions-intensive industries.

      “Our process is carbon-negative because plants are taking CO2 from the air, and we take that plant matter and process it into something structural, like synthetic rubber, which is used for things like roofing, tires, and other applications,” Dugar explains. “Generally speaking, most of that material at the end of its life gets recycled, for example to tarmac or road, or, worst-case scenario, it ends up in a landfill, so the CO2 that was captured by the plant matter stays captured in the materials. That means our production can be carbon-negative depending on the emissions of the production process. That allows us to not only reduce climate change but start reversing it. That was an insight I had about 10 years ago at MIT.”

      Finding a path

      For his PhD, Dugar explored the economics of using microbes to make high-octane gas additives. He also took classes at the MIT Sloan School of Management on sustainability and entrepreneurship, including the particularly influential course 15.366 (Climate and Energy Ventures). The experience inspired him to start a company.

      “I wanted to work on something that could have the largest climate impact, and that was replacing petroleum,” Dugar says. “It was about replacing petroleum not just as a fuel but as a material as well. Everything from the clothes we wear to the furniture we sit on is often made using petroleum.”

      By analyzing recent advances in synthetic biology and making some calculations from first principles, Dugar decided that a microbial approach to cleaning up the production of rubber was viable. He participated in the MIT Clean Energy Prize and worked with others at MIT to prove out the idea. But it was still just an idea. After graduation, he took a consulting job at a large company, spending his nights and weekends renting lab space to continue trying to make his sustainable rubber a reality.

      After 18 months, by applying engineering concepts like design-for-scale to synthetic biology, Dugar was able to develop a microbe that met 80 percent of his criteria for making an intermediate molecule called mevalonic acid. From there, he developed a chemical catalysis process that converted mevalonic acid to isoprene, the main component of natural rubber. Visolis has since patented other chemical conversion processes that turn mevalonic acid to aviation fuel, polymers, and fabrics.

      Dugar left his consulting job in 2014 and was awarded a fellowship to work on Visolis full-time at the Lawrence Berkeley National Lab via Activate, an incubator empowering scientists to reinvent the world.

      From rubber to jet fuels

      Today, in addition to isoprene, Visolis is selling skin care products through the brand Ameva Bio, which produces mevalonic acid-based creams by recycling plant byproducts created in other processes. The company offers refillable bottles and even offsets emissions from the shipping of its products.

      “We are working throughout the supply chain,” Dugar says. “It made sense to clean up the isoprene part of the rubber supply chain rather than the entire supply chain. But we’re also producing molecules for skin that are better for you, so you can put something much more sustainable and healthier on your body instead of petrochemicals. We launched Ameva to demonstrate that brands can leverage synthetic biology to turn carbon-negative ingredients into high-performing products.”

      Visolis is also starting the process of gaining regulatory approval for its sustainable aviation fuel, which Dugar believes could have the biggest climate impact of any of the company’s products by cleaning up the production of fuels for commercial flight.

      “We’re working with leading companies to help them decarbonize aviation” Dugar says. “If you look at the lifecycle of fuel, the current petroleum-based approach is we dig out hydrocarbons from the ground and burn it, emitting CO2 into the air. In our process, we take plant matter, which affixes to CO2 and captures renewable energy in those bonds, and then we transfer that into aviation fuel plus things like synthetic rubber, yoga pants, and other things that continue to hold the carbon. So, our factories can still operate at net zero carbon emissions.”

      Visolis is already generating millions of dollars in revenue, and Dugar says his goal is to scale the company rapidly now that its platform molecule has been validated.

      “We have been scaling our technology by 10 times every two to three years and are now looking to increase deployment of our technology at the same pace, which is very exciting.” Dugar says. “If you extrapolate that, very quickly you get to massive impact. That’s our goal.” More

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      in Environment

      MIT climate and sustainability interns consider aviation emissions and climate change

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      Over 600 MIT students are traveling abroad with the MIT International Science and Technology Initiatives (MISTI) to intern, research, and work in organizations across 25 countries this summer. Twenty percent of the students were placed in areas related to climate and sustainability.

      Through MISTI, hundreds of MIT students travel abroad each summer to intern in companies, universities, governments, and nongovernmental organizations. Since 2018, around 20 percent of the internships and research experiences have been in areas related to climate and sustainability. MISTI has been working to increase the number of interns working on these projects by increasing the number of hosts and available grants, as well as connecting with other labs, departments, and centers across MIT to support students’ global experiences.

      For the first time this year, MISTI developed pre-departure sessions intended to help students reflect on their experiences in the wider context of sustainability and climate change. Around 90 students were invited to participate in a Canvas course and an in-person session with guest speakers. In the Canvas session, students were asked to calculate the carbon footprint of their flight to their MISTI destination and compare the results to other common daily activities. Four out of five of them expressed that the level of emissions from their flights was higher, or much higher, than they previously thought. Half of the students expressed that this was the first time they thought about their flight emissions for the summer. The students were then directed to the MIT Climate Portal website and asked to reflect on the impact of carbon dioxide emissions on the climate and the effects of climate change on economically developing countries. The Canvas exercise concluded with readings and reflections on what can be done to address the climate crisis.

      The in-person session featured David Hsu, associate professor of urban and environmental planning and co-chair of the Campus Fast Forward working group on climate education, who presented his research and work on flight emissions. He emphasized the high impact of aviation on carbon dioxide emissions and how emissions are unevenly distributed on a global scale, based on income levels and per capita bases. A small group of travelers account for most of the emissions, which is also true in academic settings where a small number of travelers have a much higher carbon footprint. Hsu also explained the School of Architecture and Planning climate action plan and how it addresses faculty and student travel. “I know it’s hard. If we at MIT want to be leaders in this area, talking about it is not enough,” he said. “We have to act. We cannot be models just by doing research; we have to be role models at all levels. Faculty, staff, and students have to change their flight habits.”

      Having completed the climate and sustainability training, Favianna Colón Irizarry, a rising second-year majoring in chemical and biological engineering, explains, “to minimize our carbon footprint, we are taught to eat consciously and use environmentally friendly products. What we are not taught is that this alone will not make a difference; we ought to sacrifice more, like flying selectively and meaningfully, to truly make an impact. MISTI’s Climate and Sustainability helped me recognize this, as well as prepare me for how I choose to proceed in my future green endeavors.”

      Also during the session, rising seniors Anushree Chaudhuri and Melissa Stok, the leads for the MIT Student Sustainability Coalition, presented their work around coordinating efforts among students and the vast landscape of groups, organizations, and entities at the Institute. They invited all interested students to join and reach out to any of the entities that could be a good fit for their interests. Chaudhuri reflected afterwards, “Sustainability is inherently interdisciplinary. Every MIT student can incorporate sustainability into their work, regardless of major, class year, or interests! I was excited to join my SSC co-lead, Melissa, in speaking with a diverse group of MISTI interns about how to explore sustainability-related academic, extracurricular, professional, and experiential opportunities at MIT and beyond. These students come from many different disciplines, so it was incredibly heartening to hear that they are all pursuing a climate-related project abroad this summer.”

      Eduardo Rivera, MISTI’s coordinator for climate and sustainability expressed that “educational experiences abroad are a fundamental part of MIT’s mission to foster global leaders to tackle the climate crisis. This summer, more than 110 students will be working around the world in solar and wind technologies, carbon capture, climate adaptation and urban planning, sustainable concrete, electric mobility, among others. We are using this opportunity to expand on the reflection part of the experiential learning cycle. The goal of these pre-departure sessions is to raise awareness and help our students reflect on the impact of their everyday activities on the climate, and to also give them resources to learn and act thoughtfully. We hope they will not only become conscious travelers, but also agents for change.”

      “This year’s climate and sustainability pre-departure training were pilot sessions, and the goal is to expand this learning experience to all MISTI students, not just those working in the fields of climate and sustainability. This will be a unique opportunity to raise awareness and expand the knowledge to over 1,000 of our students as they travel to more than 40 countries across the globe,” explains Abby MacKenzie, MIT-India coordinator who co-developed the pre-departure sessions. More

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      in Energy

      Panel addresses technologies needed for a net-zero future

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      Five speakers at a recent public panel discussion hosted by the MIT Energy Initiative (MITEI) and introduced by Deputy Director for Science and Technology Robert Stoner tackled one of the thorniest, yet most critical, questions facing the world today: How can we achieve the ambitious goals set by governments around the globe, including the United States, to reach net zero emissions of greenhouse gases by mid-century?

      While the challenges are great, the panelists agreed, there is reason for optimism that these technological challenges can be solved. More uncertain, some suggested, are the social, economic, and political hurdles to bringing about the needed innovations.

      The speakers addressed areas where new or improved technologies or systems are needed if these ambitious goals are to be achieved. Anne White, aassociate provost and associate vice president for research administration and a professor of nuclear science and engineering at MIT, moderated the panel discussion. She said that achieving the ambitious net-zero goal “has to be accomplished by filling some gaps, and going after some opportunities.” In addressing some of these needs, she said the five topics chosen for the panel discussion were “places where MIT has significant expertise, and progress is already ongoing.”

      First of these was the heating and cooling of buildings. Christoph Reinhart, a professor of architecture and director of the Building Technology Program, said that currently about 1 percent of existing buildings are being retrofitted each year for energy efficiency and conversion from fossil-fuel heating systems to efficient electric ones — but that is not nearly enough to meet the 2050 net-zero target. “It’s an enormous task,” he said. To meet the goals, he said, would require increasing the retrofitting rate to 5 percent per year, and to require all new construction to be carbon neutral as well.

      Reinhart then showed a series of examples of how such conversions could take place using existing solar and heat pump technology, and depending on the configuration, how they could provide a payback to the homeowner within 10 years or less. However, without strong policy incentives the initial cost outlay for such a system, on the order of $50,000, is likely to put conversions out of reach of many people. Still, a recent survey found that 30 percent of homeowners polled said they would accept installation at current costs. While there is government money available for incentives for others, “we have to be very clever on how we spend all this money … and make sure that everybody is basically benefiting.”

      William Green, a professor of chemical engineering, spoke about the daunting challenge of bringing aviation to net zero. “More and more people like to travel,” he said, but that travel comes with carbon emissions that affect the climate, as well as air pollution that affects human health. The economic costs associated with these emissions, he said, are estimated at $860 per ton of jet fuel used — which is very close to the cost of the fuel itself. So the price paid by the airlines, and ultimately by the passengers, “is only about half of the true cost to society, and the other half is being borne by all of us, by the fact that it’s affecting the climate and it’s causing medical problems for people.”

      Eliminating those emissions is a major challenge, he said. Virtually all jet fuel today is fossil fuel, but airlines are starting to incorporate some biomass-based fuel, derived mostly from food waste. But even these fuels are not carbon-neutral, he said. “They actually have pretty significant carbon intensity.”

      But there are possible alternatives, he said, mostly based on using hydrogen produced by clean electricity, and making fuels out of that hydrogen by reacting it, for example, with carbon dioxide. This could indeed produce a carbon-neutral fuel that existing aircraft could use, but the process is costly, requiring a great deal of hydrogen, and ways of concentrating carbon dioxide. Other viable options also exist, but all would add significant expense, at least with present technology. “It’s going to cost a lot more for the passengers on the plane,” Green said, “But the society will benefit from that.”

      Increased electrification of heating and transportation in order to avoid the use of fossil fuels will place major demands on the existing electric grid systems, which have to perform a constant delicate balancing of production with demand. Anuradha Annaswamy, a senior research scientist in MIT’s mechanical engineering department, said “the electric grid is an engineering marvel.” In the United States it consists of 300,000 miles of transmission lines capable of carrying 470,000 megawatts of power.

      But with a projected doubling of energy from renewable sources entering the grid by 2030, and with a push to electrify everything possible — from transportation to buildings to industry — the load is not only increasing, but the patterns of both energy use and production are changing. Annaswamy said that “with all these new assets and decision-makers entering the picture, the question is how you can use a more sophisticated information layer that coordinates how all these assets are either consuming or producing or storing energy, and have that information layer coexist with the physical layer to make and deliver electricity in all these ways. It’s really not a simple problem.”

      But there are ways of addressing these complexities. “Certainly, emerging technologies in power electronics and control and communication can be leveraged,” she said. But she added that “This is not just a technology problem, really, it is something that requires technologists, economists, and policymakers to all come together.”

      As for industrial processes, Bilge Yildiz, a professor of nuclear science and engineering and materials science and engineering, said that “the synthesis of industrial chemicals and materials constitutes about 33 percent of global CO2 emissions at present, and so our goal is to decarbonize this difficult sector.” About half of all these industrial emissions come from the production of just four materials: steel, cement, ammonia, and ethylene, so there is a major focus of research on ways to reduce their emissions.

      Most of the processes to make these materials have changed little for more than a century, she said, and they are mostly heat-based processes that involve burning a lot of fossil fuel. But the heat can instead be provided from renewable electricity, which can also be used to drive electrochemical reactions in some cases as a substitute for the thermal reactions. Already, there are processes for making cement and steel that produce only about half the present carbon dioxide (CO2) emissions.

      The production of ammonia, which is widely used in fertilizer and other bulk chemicals, accounts for more greenhouse gas emissions than any other industrial source. The present thermochemical process could be replaced by an electrochemical process, she said. Similarly, the production of ethylene, as a feedstock for plastics and other materials, is the second-highest emissions producer, with three tons of carbon dioxide released for every ton of ethylene produced. Again, an electrochemical alternative method exists, but needs to be improved to be cost competitive.

      As the world moves toward electrification of industrial processes to eliminate fossil fuels, the need for emissions-free sources of electricity will continue to increase. One very promising potential addition to the range of carbon-free generation sources is fusion, a field in which MIT is a leader in developing a particularly promising technology that takes advantage of the unique properties of high-temperature superconducting (HTS) materials.

      Dennis Whyte, the director of MIT’s Plasma Science and Fusion Center, pointed out that despite global efforts to reduce CO2 emissions, “we use exactly the same percentage of carbon-based products to generate energy as 10 years ago, or 20 years ago.” To make a real difference in global emissions, “we need to make really massive amounts of carbon-free energy.”

      Fusion, the process that powers the sun, is a particularly promising pathway, because the fuel, derived from water, is virtually inexhaustible. By using recently developed HTS material to generate the powerful magnetic fields needed to produce a sustained fusion reaction, the MIT-led project, which led to a spinoff company called Commonwealth Fusion Systems, was able to radically reduce the required size of a fusion reactor, Whyte explained. Using this approach, the company, in collaboration with MIT, expects to have a fusion system that produces net energy by the middle of this decade, and be ready to build a commercial plant to produce power for the grid early in the next. Meanwhile, at least 25 other private companies are also attempting to commercialize fusion technology. “I think we can take some credit for helping to spawn what is essentially now a new industry in the United States,” Whyte said.

      Fusion offers the potential, along with existing solar and wind technologies, to provide the emissions-free power the world needs, Whyte says, but that’s only half the problem, the other part being how to get that power to where it’s needed, when it’s needed. “How do we adapt these new energy sources to be as compatible as possible with everything that we have already in terms of energy delivery?”

      Part of the way to find answers to that, he suggested, is more collaborative work on these issues that cut across disciplines, as well as more of the kinds of cross-cutting conversations and interactions that took place in this panel discussion. More

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      in Environment

      MIT engineering students take on the heat of Miami

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      Think back to the last time you had to wait for a bus. How miserable were you? If you were in Boston, your experience might have included punishing wind and icy sleet — or, more recently, a punch of pollen straight to the sinuses. But in Florida’s Miami-Dade County, where the effects of climate change are both drastic and intensifying, commuters have to contend with an entirely different set of challenges: blistering temperatures and scorching humidity, making long stints waiting in the sun nearly unbearable.

      One of Miami’s most urgent transportation needs is shared by car-clogged Boston: coaxing citizens to use the municipal bus network, rather than the emissions-heavy individual vehicles currently contributing to climate change. But buses can be a tough sell in a sunny city where humidity hovers between 60 and 80 percent year-round. 

      Enter MIT’s Department of Electrical Engineering and Computer Science (EECS) and the MIT Priscilla King Gray (PKG) Public Service Center. The result of close collaboration between the two organizations, class 6.900 (Engineering For Impact) challenges EECS students to apply their engineering savvy to real-world problems beyond the MIT campus.

      This spring semester, the real-world problem was heat. 

      Miami-Dade County Department of Transportation and Public Works Chief Innovation Officer Carlos Cruz-Casas explains: “We often talk about the city we want to live in, about how the proper mix of public transportation, on-demand transit, and other mobility solutions, such as e-bikes and e-scooters, could help our community live a car-light life. However, none of this will be achievable if the riders are not comfortable when doing so.” 

      “When people think of South Florida and climate change, they often think of sea level rise,” says Juan Felipe Visser, deputy director of equity and engagement within the Office of the Mayor in Miami-Dade. “But heat really is the silent killer. So the focus of this class, on heat at bus stops, is very apt.” With little tree cover to give relief at some of the hottest stops, Miami-Dade commuters cluster in tiny patches of shade behind bus stops, sometimes giving up when the heat becomes unbearable. 

      A more conventional electrical engineering course might use temperature monitoring as an abstract example, building sample monitors in isolation and grading them as a merely academic exercise. But Professor Joel Volman, EECS faculty head of electrical engineering, and Joe Steinmeyer, senior lecturer in EECS, had something more impactful in mind.

      “Miami-Dade has a large population of people who are living in poverty, undocumented, or who are otherwise marginalized,” says Voldman. “Waiting, sometimes for a very long time, in scorching heat for the bus is just one aspect of how a city population can be underserved, but by measuring patterns in how many people are waiting for a bus, how long they wait, and in what conditions, we can begin to see where services are not keeping up with demand.”

      Only after that gap is quantified can the work of city and transportation planners begin, Cruz-Casas explains: “We needed to quantify the time riders are exposed to extreme heat and prioritize improvements, including on-time performance improvements, increasing service frequency, or looking to enhance the tree canopy near the bus stop.” 

      Quantifying that time — and the subjective experience of the wait — proved tricky, however. With over 7,500 bus stops along 101 bus routes, Miami-Dade’s transportation network presents a considerable data-collection challenge. A network of physical temperature monitors could be useful, but only if it were carefully calibrated to meet the budgetary, environmental, privacy, and implementation requirements of the city. But how do you work with city officials — not to mention all of bus-riding Miami — from over 2,000 miles away? 

      This is where the PKG Center comes in. “We are a hub and a connector and facilitator of best practices,” explains Jill Bassett, associate dean and director of the center, who worked with Voldman and Steinmeyer to find a municipal partner organization for the course. “We bring knowledge of current pedagogy around community-engaged learning, which includes: help with framing a partnership that centers community-identified concerns and is mutually beneficial; identifying and learning from a community partner; talking through ways to build in opportunities for student learners to reflect on power dynamics, reciprocity, systems thinking, long-term planning, continuity, ethics, all the types of things that come up with this kind of shared project.”

      Through a series of brainstorming conversations, Bassett helped Voldman and Steinmeyer structure a well-defined project plan, as Cruz-Casas weighed in on the county’s needed technical specifications (including affordability, privacy protection, and implementability).

      “This course brings together a lot of subject area experts,” says Voldman. “We brought in guest lecturers, including Abby Berenson from the Sloan Leadership Center, to talk about working in teams; engineers from BOSE to talk about product design, certification, and environmental resistance; the co-founder and head of engineering from MIT spinout Butlr to talk about their low-power occupancy sensor; Tony Hu from MIT IDM [Integrated Design and Management] to talk about industrial design; and Katrina LaCurts from EECS to talk about communications and networking.”

      With the support of two generous donations and a gift of software from Altium, 6.900 developed into a hands-on exercise in hardware/software product development with a tangible goal in sight: build a better bus monitor.

      The challenges involved in this undertaking became apparent as soon as the 6.900 students began designing their monitors. “The most challenging requirement to meet was that the monitor be able to count how many people were waiting — and for how long they’d been standing there — while still maintaining privacy,” says Fabian Velazquez ’23 a recent EECS graduate. The task was complicated by commuters’ natural tendency to stand where the shade goes — whether beneath a tree or awning or snaking against a nearby wall in a line — rather than directly next to the bus sign or inside the bus shelter. “Accurately measuring people count with a camera — the most straightforward choice — is already quite difficult since you have to incorporate machine learning to identify which objects in frame are people. Maintaining privacy added an extra layer of constraint … since there is no guarantee the collected data wouldn’t be vulnerable.”

      As the groups weighed various privacy-preserving options, including lidar, radar, and thermal imaging, the class realized that Wi-Fi “sniffers,” which count the number of Wi-Fi enabled signals in the immediate area, were their best option to count waiting passengers. “We were all excited and ready for this amazing, answer-to-all-our-problems radar sensor to count people,” says Velasquez. “That component was extremely complex, however, and the complexity would have ultimately made my team use a lot of time and resources to integrate with our system. We also had a short time-to-market for this system we developed. We made the trade-off of complexity for robustness.” 

      The weather also posed its own set of challenges. “Environmental conditions were big factors on the structure and design of our devices,” says Yong Yan (Crystal) Liang, a rising junior majoring in EECS. “We incorporated humidity and temperature sensors into our data to show the weather at individual stops. Additionally, we also considered how our enclosure may be affected by extreme heat or potential hurricanes.”

      The heat variable proved problematic in multiple ways. “People detection was especially difficult, for in the Miami heat, thermal cameras may not be able to distinguish human body temperature from the surrounding air temperature, and the glare of the sun off of other surfaces in the area makes most forms of imaging very buggy,” says Katherine Mohr ’23. “My team had considered using mmWave sensors to get around these constraints, but we found the processing to be too difficult, and (like the rest of the class), we decided to only move forward with Wi-Fi/BLE [Bluetooth Low Energy] sniffers.”

      The most valuable component of the new class may well have been the students’ exposure to real-world hardware/software engineering product development, where limitations on time and budget always exist, and where client requests must be carefully considered.  “Having an actual client to work with forced us to learn how to turn their wants into more specific technical specifications,” says Mohr. “We chose deliverables each week to complete by Friday, prioritizing tasks which would get us to a minimum viable product, as well as tasks that would require extra manufacturing time, like designing the printed-circuit board and enclosure.”

      Play video

      Joel Voldman, who co-designed 6.900 (Engineering For Impact) with Joe Steinmeyer and MIT’s Priscilla King Gray (PKG) Public Service Center, describes how the course allowed students help develop systems for the public good. Voldman is the winner of the 2023 Teaching with Digital Technology Award, which is co-sponsored by MIT Open Learning and the Office of the Vice Chancellor. Video: MIT Open Learning

      Crystal Liang counted her conversations with city representatives as among her most valuable 6.900 experiences. “We generated a lot of questions and were able to communicate with the community leaders of this project from Miami-Dade, who made time to answer all of them and gave us ideas from the goals they were trying to achieve,” she reports. “This project gave me a new perspective on problem-solving because it taught me to see things from the community members’ point of view.” Some of those community leaders, including Marta Viciedo, co-founder of Transit Alliance Miami, joined the class’s final session on May 16 to review the students’ proposed solutions. 

      The students’ thoughtful approach paid off when it was time to present the heat monitors to the class’s client. In a group conference call with Miami-Dade officials toward the end of the semester, the student teams shared their findings and the prototypes they’d created, along with videos of the devices at work. Juan Felipe Visser was among those in attendance. “This is a lot of work,” he told the students following their presentation. “So first of all, thank you for doing that, and for presenting to us. I love the concept. I took the bus this morning, as I do every morning, and was battered by the sun and the heat. So I personally appreciated the focus.” 

      Cruz-Casas agreed: “I am pleasantly surprised by the diverse approach the students are taking. We presented a challenge, and they have responded to it and managed to think beyond the problem at hand. I’m very optimistic about how the outcomes of this project will have a long-lasting impact for our community. At a minimum, I’m thinking that the more awareness we raise about this topic, the more opportunities we have to have the brightest minds seeking for a solution.”

      The creators of 6.900 agree, and hope that their class helps more MIT engineers to broaden their perspective on the meaning and application of their work. 

      “We are really excited about students applying their skills within a real-world, complex environment that will impact real people,” says Bassett. “We are excited that they are learning that it’s not just the design of technology that matters, but that climate; environment and built environment; and issues around socioeconomics, race, and equity, all come into play. There are layers and layers to the creation and deployment of technology in a demographically diverse multilingual community that is at the epicenter of climate change.” More