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      in Environment

      Megawatt electrical motor designed by MIT engineers could help electrify aviation

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      Aviation’s huge carbon footprint could shrink significantly with electrification. To date, however, only small all-electric planes have gotten off the ground. Their electric motors generate hundreds of kilowatts of power. To electrify larger, heavier jets, such as commercial airliners, megawatt-scale motors are required. These would be propelled by hybrid or turbo-electric propulsion systems where an electrical machine is coupled with a gas turbine aero-engine.

      To meet this need, a team of MIT engineers is now creating a 1-megawatt motor that could be a key stepping stone toward electrifying larger aircraft. The team has designed and tested the major components of the motor, and shown through detailed computations that the coupled components can work as a whole to generate one megawatt of power, at a weight and size competitive with current small aero-engines.

      For all-electric applications, the team envisions the motor could be paired with a source of electricity such as a battery or a fuel cell. The motor could then turn the electrical energy into mechanical work to power a plane’s propellers. The electrical machine could also be paired with a traditional turbofan jet engine to run as a hybrid propulsion system, providing electric propulsion during certain phases of a flight.

      “No matter what we use as an energy carrier — batteries, hydrogen, ammonia, or sustainable aviation fuel — independent of all that, megawatt-class motors will be a key enabler for greening aviation,” says Zoltan Spakovszky, the T. Wilson Professor in Aeronautics and the Director of the Gas Turbine Laboratory (GTL) at MIT, who leads the project.

      Spakovszky and members of his team, along with industry collaborators, will present their work at a special session of the American Institute of Aeronautics and Astronautics – Electric Aircraft Technologies Symposium (EATS) at the Aviation conference in June.

      The MIT team is composed of faculty, students, and research staff from GTL and the MIT Laboratory for Electromagnetic and Electronic Systems: Henry Andersen Yuankang Chen, Zachary Cordero, David Cuadrado,  Edward Greitzer, Charlotte Gump, James Kirtley, Jr., Jeffrey Lang, David Otten, David Perreault, and Mohammad Qasim,  along with Marc Amato of Innova-Logic LLC. The project is sponsored by Mitsubishi Heavy Industries (MHI).

      Heavy stuff

      To prevent the worst impacts from human-induced climate change, scientists have determined that global emissions of carbon dioxide must reach net zero by 2050. Meeting this target for aviation, Spakovszky says, will require “step-change achievements” in the design of unconventional aircraft, smart and flexible fuel systems, advanced materials, and safe and efficient electrified propulsion. Multiple aerospace companies are focused on electrified propulsion and the design of megawatt-scale electric machines that are powerful and light enough to propel passenger aircraft.

      “There is no silver bullet to make this happen, and the devil is in the details,” Spakovszky says. “This is hard engineering, in terms of co-optimizing individual components and making them compatible with each other while maximizing overall performance. To do this means we have to push the boundaries in materials, manufacturing, thermal management, structures and rotordynamics, and power electronics”

      Broadly speaking, an electric motor uses electromagnetic force to generate motion. Electric motors, such as those that power the fan in your laptop, use electrical energy — from a battery or power supply — to generate a magnetic field, typically through copper coils. In response, a magnet, set near the coils, then spins in the direction of the generated field and can then drive a fan or propeller.

      Electric machines have been around for over 150 years, with the understanding that, the bigger the appliance or vehicle, the larger the copper coils  and the magnetic rotor, making the machine heavier. The more power the electrical machine generates, the more heat it produces, which requires additional elements to keep the components cool — all of which can take up space and add significant weight to the system, making it challenging for airplane applications.

      “Heavy stuff doesn’t go on airplanes,” Spakovszky says. “So we had to come up with a compact, lightweight, and powerful architecture.”

      Good trajectory

      As designed, the MIT electric motor and power electronics are each about the size of a checked suitcase weighing less than an adult passenger.

      The motor’s main components are: a high-speed rotor, lined with an array of magnets with varying orientation of polarity; a compact low-loss stator that fits inside the rotor and contains an intricate array of copper windings; an advanced heat exchanger that keeps the components cool while transmitting the torque of the machine; and a distributed power electronics system, made from 30 custom-built circuit boards, that precisely change the currents running through each of the stator’s copper windings, at high frequency.

      “I believe this is the first truly co-optimized integrated design,” Spakovszky says. “Which means we did a very extensive design space exploration where all considerations from thermal management, to rotor dynamics, to power electronics and electrical machine architecture were assessed in an integrated way to find out what is the best possible combination to get the required specific power at one megawatt.”

      As a whole system, the motor is designed such that the distributed circuit boards are close coupled with the electrical machine to minimize transmission loss and to allow effective air cooling through the integrated heat exchanger.

      “This is a high-speed machine, and to keep it rotating while creating torque, the magnetic fields have to be traveling very quickly, which we can do through our circuit boards switching at high frequency,” Spakovszky says.

      To mitigate risk, the team has built and tested each of the major components individually, and shown that they can operate as designed and at conditions exceeding normal operational demands. The researchers plan to assemble the first fully working electric motor, and start testing it in the fall.

      “The electrification of aircraft has been on a steady rise,” says Phillip Ansell, director of the Center for Sustainable Aviation at the University of Illinois Urbana-Champaign, who was not involved in the project. “This group’s design uses a wonderful combination of conventional and cutting-edge methods for electric machine development, allowing it to offer both robustness and efficiency to meet the practical needs of aircraft of the future.”

      Once the MIT team can demonstrate the electric motor as a whole, they say the design could power regional aircraft and could also be a companion to conventional jet engines, to enable hybrid-electric propulsion systems. The team also envision that multiple one-megawatt motors could power multiple fans distributed along the wing on future aircraft configurations. Looking ahead, the foundations of the one-megawatt electrical machine design could potentially be scaled up to multi-megawatt motors, to power larger passenger planes.

      “I think we’re on a good trajectory,” says Spakovszky, whose group and research have focused on more than just gas turbines. “We are not electrical engineers by training, but addressing the 2050 climate grand challenge is of utmost importance; working with electrical engineering faculty, staff and students for this goal can draw on MIT’s breadth of technologies so the whole is greater than the sum of the parts. So we are reinventing ourselves in new areas. And MIT gives you the opportunity to do that.” More

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      in Energy

      Will the charging networks arrive in time?

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      For many owners of electric vehicles (EVs), or for prospective EV owners, a thorny problem is where to charge them. Even as legacy automakers increasingly invest in manufacturing more all-electric cars and trucks, there is not a dense network of charging stations serving many types of vehicles, which would make EVs more convenient to use.

      “We’re going to have the ability to produce and deliver millions of EVs,” said MIT Professor Charles Fine at the final session this semester of the MIT Mobility Forum. “It’s not clear we’re going to have the ability to charge them. That’s a huge, huge mismatch.”

      Indeed, making EV charging stations as ubiquitous as gas stations could spur a major transition within the entire U.S. vehicle fleet. While the automaker Tesla has built a network of almost 2,000 charging stations across the U.S., and might make some interoperable with other makes of vehicles, independent companies trying to develop a business out of it are still trying to gain significant traction.

      “They don’t have a business model that works yet,” said Fine, the Chrysler Leaders for Global Operations Professor of Management at the MIT Sloan School of Management, speaking of startup firms. “They haven’t figured out their supply chains. They haven’t figured out the customer value proposition. They haven’t figured out their technology standards. It’s a very, very immature domain.”

      The May 12 event drew nearly 250 people as well as an online audience. The MIT Mobility Forum is a weekly set of talks and discussions during the academic year, ranging widely across the field of transportation and design. It is hosted by the MIT Mobility Initiative, which works to advance sustainable, accessible, and safe forms of transportation.

      Fine is a prominent expert in the areas of operations strategy, entrepreneurship, and supply chain management. He has been at MIT Sloan for over 30 years; from 2015 to 2022, he also served as the founding president, dean, and CEO of the Asia School of Business in Kuala Lumpur, Malaysia, a collaboration between MIT Sloan and Bank Negara Malaysia. Fine is also author of “Faster, Smarter, Greener: The Future of the Car and Urban Mobility” (MIT Press, 2017).

      In Fine’s remarks, he discussed the growth stages of startup companies, highlighting three phases where firms try to “nail it, scale it, and sail it” — that is, figure out the concept and workability of their enterprise, try to expand it, and then operate as a larger company. The charging-business startups are still somewhere within the first of these phases.

      At the same time, the established automakers have announced major investments in EVs — a collective $860 billion over the next decade, Fine noted. Among others, Ford says it will invest $50 billion in EV production by 2026; General Motors plans to spend $35 billion on EVs by 2025; and Toyota has announced it will invest $35 billion in EV manufacturing by 2030.

      With all these vehicles potentially coming to market, Fine suggested, the crux of the issue is a kind of “chicken and egg” problem between EVs and the network needed to support them.

      “If you’re a startup company in the charging business, if there aren’t many EVs out there, you’re not going to be making much money, and that doesn’t give you the capital to continue to invest and grow,” Fine said. “So, they need to wait until they have revenue before they can grow further. On the other hand, why should anybody buy an electric car if they don’t think they’re going to be able to charge it?”

      Those living in single-family homes can install chargers. But many others are not in that situation, Fine noted: “For people who don’t have fixed parking spaces and have to rely on the public network, there is this chicken-and-egg problem. They can’t buy an EV unless they know how they’re going to be able to charge it, and charging companies can’t build out their networks unless they know how they’re going to get their revenue.”

      The event featured a question-and-answer session and audience discussion, with a range of questions, and comments from some industry veterans, including Robin Chase SM ’86, the co-founder and former CEO of Zipcar. She expressed some optimism that startup charging companies will be able to get traction in the nascent market before long.

      “The right companies can learn very fast,” Chase said. “There’s no reason why they can’t correct those scaling problems in short-ish order.”

      In answer to other audience questions, Fine noted some of the challenges that will have to be addressed by independent charging firms, such as unified standards and interoperability among automakers and charging stations.

      “For a driver to have to have six different apps, or [their] car doesn’t fit in the plug here or there, or my software doesn’t talk to my credit card … connectivity, standards, technical issues need to be worked out as well,” Fine said.

      There are also varying regulatory issues, including grid policies and what consumers can be billed for, which have to be worked out on a state-by-state basis, meaning that even modest-size startups will have to have knowledgeable and productive legal departments.

      All of which makes it possible, as Fine suggested, that the large legacy automakers will start investing more heavily in the charging business in the near future. Mercedes, he noted, just announced in January that it is entering into a partnership with charging firms ChargePoint and MN8 Energy to develop about 400 charging stations across North America by 2027. By necessity, others might have to follow suit if they want to protect their massive planned investments in the EV sector.

      “I’m not in the business of telling [automakers] what to do, but I do think they have a lot at risk,” Fine said. “They’re spending billions and billions of dollars to produce these cars, and I don’t think they can afford an epic failure [if] people don’t buy them because there’s no charging infrastructure. If they’re waiting for the startups to build out rapidly, then they may be waiting longer than they hope to wait.” More

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      in Energy

      Finding “hot spots” where compounding environmental and economic risks converge

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      A computational tool developed by researchers at the MIT Joint Program on the Science and Policy of Global Change pinpoints specific counties within the United States that are particularly vulnerable to economic distress resulting from a transition from fossil fuels to low-carbon energy sources. By combining county-level data on employment in fossil fuel (oil, natural gas, and coal) industries with data on populations below the poverty level, the tool identifies locations with high risks for transition-driven economic hardship. It turns out that many of these high-risk counties are in the south-central U.S., with a heavy concentration in the lower portions of the Mississippi River.

      The computational tool, which the researchers call the System for the Triage of Risks from Environmental and Socio-economic Stressors (STRESS) platform, almost instantly displays these risk combinations on an easy-to-read visual map, revealing those counties that stand to gain the most from targeted green jobs retraining programs.  

      Drawing on data that characterize land, water, and energy systems; biodiversity; demographics; environmental equity; and transportation networks, the STRESS platform enables users to assess multiple, co-evolving, compounding hazards within a U.S. geographical region from the national to the county level. Because of its comprehensiveness and precision, this screening-level visualization tool can pinpoint risk “hot spots” that can be subsequently investigated in greater detail. Decision-makers can then plan targeted interventions to boost resilience to location-specific physical and economic risks.

      The platform and its applications are highlighted in a new study in the journal Frontiers in Climate.

      “As risks to natural and managed resources — and to the economies that depend upon them — become more complex, interdependent, and compounding amid rapid environmental and societal changes, they require more and more human and computational resources to understand and act upon,” says MIT Joint Program Deputy Director C. Adam Schlosser, the lead author of the study. “The STRESS platform provides decision-makers with an efficient way to combine and analyze data on those risks that matter most to them, identify ‘hot spots’ of compounding risk, and design interventions to minimize that risk.”

      In one demonstration of the STRESS platform’s capabilities, the study shows that national and global actions to reduce greenhouse gas emissions could simultaneously reduce risks to land, water, and air quality in the upper Mississippi River basin while increasing economic risks in the lower basin, where poverty and unemployment are already disproportionate. In another demonstration, the platform finds concerning “hot spots” where flood risk, poverty, and nonwhite populations coincide.

      The risk triage platform is based on an emerging discipline called multi-sector dynamics (MSD), which seeks to understand and model compounding risks and potential tipping points across interconnected natural and human systems. Tipping points occur when these systems can no longer sustain multiple, co-evolving stresses, such as extreme events, population growth, land degradation, drinkable water shortages, air pollution, aging infrastructure, and increased human demands. MSD researchers use observations and computer models to identify key precursory indicators of such tipping points, providing decision-makers with critical information that can be applied to mitigate risks and boost resilience in natural and managed resources. With funding from the U.S. Department of Energy, the MIT Joint Program has since 2018 been developing MSD expertise and modeling tools and using them to explore compounding risks and potential tipping points in selected regions of the United States.

      Current STRESS platform data includes more than 100 risk metrics at the county-level scale, but data collection is ongoing. MIT Joint Program researchers are continuing to develop the STRESS platform as an “open-science tool” that welcomes input from academics, researchers, industry and the general public. More

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      in Energy

      Minimizing electric vehicles’ impact on the grid

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      National and global plans to combat climate change include increasing the electrification of vehicles and the percentage of electricity generated from renewable sources. But some projections show that these trends might require costly new power plants to meet peak loads in the evening when cars are plugged in after the workday. What’s more, overproduction of power from solar farms during the daytime can waste valuable electricity-generation capacity.

      In a new study, MIT researchers have found that it’s possible to mitigate or eliminate both these problems without the need for advanced technological systems of connected devices and real-time communications, which could add to costs and energy consumption. Instead, encouraging the placing of charging stations for electric vehicles (EVs) in strategic ways, rather than letting them spring up anywhere, and setting up systems to initiate car charging at delayed times could potentially make all the difference.

      The study, published today in the journal Cell Reports Physical Science, is by Zachary Needell PhD ’22, postdoc Wei Wei, and Professor Jessika Trancik of MIT’s Institute for Data, Systems, and Society.

      In their analysis, the researchers used data collected in two sample cities: New York and Dallas. The data were gathered from, among other sources, anonymized records collected via onboard devices in vehicles, and surveys that carefully sampled populations to cover variable travel behaviors. They showed the times of day cars are used and for how long, and how much time the vehicles spend at different kinds of locations — residential, workplace, shopping, entertainment, and so on.

      The findings, Trancik says, “round out the picture on the question of where to strategically locate chargers to support EV adoption and also support the power grid.”

      Better availability of charging stations at workplaces, for example, could help to soak up peak power being produced at midday from solar power installations, which might otherwise go to waste because it is not economical to build enough battery or other storage capacity to save all of it for later in the day. Thus, workplace chargers can provide a double benefit, helping to reduce the evening peak load from EV charging and also making use of the solar electricity output.

      These effects on the electric power system are considerable, especially if the system must meet charging demands for a fully electrified personal vehicle fleet alongside the peaks in other demand for electricity, for example on the hottest days of the year. If unmitigated, the evening peaks in EV charging demand could require installing upwards of 20 percent more power-generation capacity, the researchers say.

      “Slow workplace charging can be more preferable than faster charging technologies for enabling a higher utilization of midday solar resources,” Wei says.

      Meanwhile, with delayed home charging, each EV charger could be accompanied by a simple app to estimate the time to begin its charging cycle so that it charges just before it is needed the next day. Unlike other proposals that require a centralized control of the charging cycle, such a system needs no interdevice communication of information and can be preprogrammed — and can accomplish a major shift in the demand on the grid caused by increasing EV penetration. The reason it works so well, Trancik says, is because of the natural variability in driving behaviors across individuals in a population.

      By “home charging,” the researchers aren’t only referring to charging equipment in individual garages or parking areas. They say it’s essential to make charging stations available in on-street parking locations and in apartment building parking areas as well.

      Trancik says the findings highlight the value of combining the two measures — workplace charging and delayed home charging — to reduce peak electricity demand, store solar energy, and conveniently meet drivers’ charging needs on all days. As the team showed in earlier research, home charging can be a particularly effective component of a strategic package of charging locations; workplace charging, they have found, is not a good substitute for home charging for meeting drivers’ needs on all days.

      “Given that there’s a lot of public money going into expanding charging infrastructure,” Trancik says, “how do you incentivize the location such that this is going to be efficiently and effectively integrated into the power grid without requiring a lot of additional capacity expansion?” This research offers some guidance to policymakers on where to focus rules and incentives.

      “I think one of the fascinating things about these findings is that by being strategic you can avoid a lot of physical infrastructure that you would otherwise need,” she adds. “Your electric vehicles can displace some of the need for stationary energy storage, and you can also avoid the need to expand the capacity of power plants, by thinking about the location of chargers as a tool for managing demands — where they occur and when they occur.”

      Delayed home charging could make a surprising amount of difference, the team found. “It’s basically incentivizing people to begin charging later. This can be something that is preprogrammed into your chargers. You incentivize people to delay the onset of charging by a bit, so that not everyone is charging at the same time, and that smooths out the peak.”

      Such a program would require some advance commitment on the part of participants. “You would need to have enough people committing to this program in advance to avoid the investment in physical infrastructure,” Trancik says. “So, if you have enough people signing up, then you essentially don’t have to build those extra power plants.”

      It’s not a given that all of this would line up just right, and putting in place the right mix of incentives would be crucial. “If you want electric vehicles to act as an effective storage technology for solar energy, then the [EV] market needs to grow fast enough in order to be able to do that,” Trancik says.

      To best use public funds to help make that happen, she says, “you can incentivize charging installations, which would go through ideally a competitive process — in the private sector, you would have companies bidding for different projects, but you can incentivize installing charging at workplaces, for example, to tap into both of these benefits.” Chargers people can access when they are parked near their residences are also important, Trancik adds, but for other reasons. Home charging is one of the ways to meet charging needs while avoiding inconvenient disruptions to people’s travel activities.

      The study was supported by the European Regional Development Fund Operational Program for Competitiveness and Internationalization, the Lisbon Portugal Regional Operation Program, and the Portuguese Foundation for Science and Technology. More

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      in Environment

      Study: Carbon-neutral pavements are possible by 2050, but rapid policy and industry action are needed

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      Almost 2.8 million lane-miles, or about 4.6 million lane-kilometers, of the United States are paved.

      Roads and streets form the backbone of our built environment. They take us to work or school, take goods to their destinations, and much more.

      However, a new study by MIT Concrete Sustainability Hub (CSHub) researchers shows that the annual greenhouse gas (GHG) emissions of all construction materials used in the U.S. pavement network are 11.9 to 13.3 megatons. This is equivalent to the emissions of a gasoline-powered passenger vehicle driving about 30 billion miles in a year.

      As roads are built, repaved, and expanded, new approaches and thoughtful material choices are necessary to dampen their carbon footprint. 

      The CSHub researchers found that, by 2050, mixtures for pavements can be made carbon-neutral if industry and governmental actors help to apply a range of solutions — like carbon capture — to reduce, avoid, and neutralize embodied impacts. (A neutralization solution is any compensation mechanism in the value chain of a product that permanently removes the global warming impact of the processes after avoiding and reducing the emissions.) Furthermore, nearly half of pavement-related greenhouse gas (GHG) savings can be achieved in the short term with a negative or nearly net-zero cost.

      The research team, led by Hessam AzariJafari, MIT CSHub’s deputy director, closed gaps in our understanding of the impacts of pavements decisions by developing a dynamic model quantifying the embodied impact of future pavements materials demand for the U.S. road network. 

      The team first split the U.S. road network into 10-mile (about 16 kilometer) segments, forecasting the condition and performance of each. They then developed a pavement management system model to create benchmarks helping to understand the current level of emissions and the efficacy of different decarbonization strategies. 

      This model considered factors such as annual traffic volume and surface conditions, budget constraints, regional variation in pavement treatment choices, and pavement deterioration. The researchers also used a life-cycle assessment to calculate annual state-level emissions from acquiring pavement construction materials, considering future energy supply and materials procurement.

      The team considered three scenarios for the U.S. pavement network: A business-as-usual scenario in which technology remains static, a projected improvement scenario aligned with stated industry and national goals, and an ambitious improvement scenario that intensifies or accelerates projected strategies to achieve carbon neutrality. 

      If no steps are taken to decarbonize pavement mixtures, the team projected that GHG emissions of construction materials used in the U.S. pavement network would increase by 19.5 percent by 2050. Under the projected scenario, there was an estimated 38 percent embodied impact reduction for concrete and 14 percent embodied impact reduction for asphalt by 2050.

      The keys to making the pavement network carbon neutral by 2050 lie in multiple places. Fully renewable energy sources should be used for pavement materials production, transportation, and other processes. The federal government must contribute to the development of these low-carbon energy sources and carbon capture technologies, as it would be nearly impossible to achieve carbon neutrality for pavements without them. 

      Additionally, increasing pavements’ recycled content and improving their design and production efficiency can lower GHG emissions to an extent. Still, neutralization is needed to achieve carbon neutrality.

      Making the right pavement construction and repair choices would also contribute to the carbon neutrality of the network. For instance, concrete pavements can offer GHG savings across the whole life cycle as they are stiffer and stay smoother for longer, meaning they require less maintenance and have a lesser impact on the fuel efficiency of vehicles. 

      Concrete pavements have other use-phase benefits including a cooling effect through an intrinsically high albedo, meaning they reflect more sunlight than regular pavements. Therefore, they can help combat extreme heat and positively affect the earth’s energy balance through positive radiative forcing, making albedo a potential neutralization mechanism.

      At the same time, a mix of fixes, including using concrete and asphalt in different contexts and proportions, could produce significant GHG savings for the pavement network; decision-makers must consider scenarios on a case-by-case basis to identify optimal solutions. 

      In addition, it may appear as though the GHG emissions of materials used in local roads are dwarfed by the emissions of interstate highway materials. However, the study found that the two road types have a similar impact. In fact, all road types contribute heavily to the total GHG emissions of pavement materials in general. Therefore, stakeholders at the federal, state, and local levels must be involved if our roads are to become carbon neutral. 

      The path to pavement network carbon-neutrality is, therefore, somewhat of a winding road. It demands regionally specific policies and widespread investment to help implement decarbonization solutions, just as renewable energy initiatives have been supported. Providing subsidies and covering the costs of premiums, too, are vital to avoid shifts in the market that would derail environmental savings.

      When planning for these shifts, we must recall that pavements have impacts not just in their production, but across their entire life cycle. As pavements are used, maintained, and eventually decommissioned, they have significant impacts on the surrounding environment.

      If we are to meet climate goals such as the Paris Agreement, which demands that we reach carbon-neutrality by 2050 to avoid the worst impacts of climate change, we — as well as industry and governmental stakeholders — must come together to take a hard look at the roads we use every day and work to reduce their life cycle emissions. 

      The study was published in the International Journal of Life Cycle Assessment. In addition to AzariJafari, the authors include Fengdi Guo of the MIT Department of Civil and Environmental Engineering; Jeremy Gregory, executive director of the MIT Climate and Sustainability Consortium; and Randolph Kirchain, director of the MIT CSHub. More

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      in Environment

      Sustainable supply chains put the customer first

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      When we consider the supply chain, we typically think of factories, ships, trucks, and warehouses. Yet, the customer side is equally important, especially in efforts to make our distribution networks more sustainable. Customers are an untapped resource in building sustainability, says Josué C. Velázquez Martínez, a research scientist at MIT Center for Transportation and Logistics. 

      Velázquez Martínez, who is director of MIT’s Sustainable Supply Chain Lab, investigates how customer-facing supply chains can be made more environmentally and socially sustainable. One way is a Green Button project that explores how to optimize e-commerce delivery schedules to reduce carbon emissions and persuade customers to use less carbon-intensive four- or five-day shipping options instead of one or two days. Velázquez Martínez has also launched the MIT Low Income Firms Transformation (LIFT) Lab that is researching ways to improve micro-retailer supply chains in the developing world to provide owners with the necessary tools for survival.  

      “The definition of sustainable supply chain keeps evolving because things that were sustainable 20 to 30 years ago are not as sustainable now,” says Velázquez Martínez. “Today, there are more companies that are capturing information to build strategies for environmental, economic, and social sustainability. They are investing in alternative energy and other solutions to make the supply chain more environmentally friendly and are tracking their suppliers and identifying key vulnerabilities. A big part of this is an attempt to create fairer conditions for people who work in supply chains or are dependent on them.”

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      The move toward sustainable supply chain is being driven as much by people as by companies, whether they are playing the role of selective consumer or voting citizens. The consumer aspect is often overlooked, says Velázquez Martínez. “Consumers are the ones who move the supply chain. We are looking at how companies can provide transparency to involve customers in their sustainability strategy.” 

      Proposed solutions for sustainability are not always as effective as promised. Some fashion rental schemes fall into this category, says Velázquez Martínez. “There are many new rental companies that are trying to get more use out of clothes to offset the emissions associated with production. We recently researched the environmental impact of monthly subscription models where consumers pay a fee to receive clothes for a month before returning them, as well as peer-to-peer sharing models.” 

      The researchers found that while rental services generally have a lower carbon footprint than retail sales, hidden emissions from logistics played a surprisingly large role. “First, you need to deliver the clothes and pick them up, and there are high return rates,” says Velázquez Martínez. “When you factor in dry cleaning and packaging emissions, the rental models in some cases have a worse carbon footprint than buying new clothes.” Peer-to-peer sharing could be better, he adds, but that depends on how far the consumers travel to meet-up points. 

      Typically, says Velázquez Martínez, garment types that are frequently used are not well suited to rental models. “But for specialty clothes such as wedding dresses or prom dresses, it is better to rent.” 

      Waiting a few days to save the planet 

      Even before the pandemic, online retailing gained a second wind due to low-cost same- and next-day delivery options. While e-commerce may have its drawbacks as a contributor to social isolation and reduced competition, it has proven itself to be far more eco-friendly than brick-and-mortar shopping, not to mention a lot more convenient. Yet rapid deliveries are cutting into online-shopping’s carbon-cutting advantage.

      In 2019, MIT’s Sustainable Supply Chain Lab launched a Green Bottle project to study the rapid delivery phenomenon. The project has been “testing whether consumers would be willing to delay their e-commerce deliveries to reduce the environmental impact of fast shipping,” says Velázquez Martínez. “Many companies such as Walmart and Target have followed Amazon’s 2019 strategy of moving from two-day to same-day delivery. Instead of sending a fully loaded truck to a neighborhood every few days, they now send multiple trucks to that neighborhood every day, and there are more days when trucks are targeting each neighborhood. All this increases carbon emissions and makes it hard for shippers to consolidate. ”  

      Working with Coppel, one of Mexico’s largest retailers, the Green Button project inspired a related Consolidation Ecommerce Project that built a large-scale mathematical model to provide a strategy for consolidation. The model determined what delivery time window each neighborhood demands and then calculated the best day to deliver to each neighborhood to meet the desired window while minimizing carbon emissions. 

      No matter what mixture of delivery times was used, the consolidation model helped retailers schedule deliveries more efficiently. Yet, the biggest cuts in emissions emerged when customers were willing to wait several days.

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      “When we ran a month-long simulation comparing our model for four-to-five-day delivery with Coppel’s existing model for one- or two-day delivery, we saw savings in fuel consumption of over 50 percent on certain routes” says Velázquez Martínez. “This is huge compared to other strategies for squeezing more efficiency from the last-mile supply chain, such as routing optimization, where savings are close to 5 percent. The optimal solution depends on factors such as the capacity for consolidation, the frequency of delivery, the store capacity, and the impact on inbound operations.” 

      The researchers next set out to determine if customers could be persuaded to wait longer for deliveries. Considering that the price differential is low or nonexistent, this was a considerable challenge. Yet, the same day habit is only a few years old, and some consumers have come to realize they don’t always need rapid deliveries. “Some consumers who order by rapid delivery find they are too busy to open the packages right away,” says Velázquez Martínez.  

      Trees beat kilograms of CO2

      The researchers set out to find if consumers would be willing to sacrifice a bit of convenience if they knew they were helping to reduce climate change. The Green Button project tested different public outreach strategies. For one test group, they reported the carbon impact of delivery times in kilograms of carbon dioxide (CO2). Another group received the information expressed in terms of the energy required to recycle a certain amount of garbage. A third group learned about emissions in terms of the number of trees required to trap the carbon. “Explaining the impact in terms of trees led to almost 90 percent willing to wait another day or two,” says Velázquez Martínez. “This is compared to less than 40 percent for the group that received the data in kilograms of CO2.” 

      Another surprise was that there was no difference in response based on income, gender, or age. “Most studies of green consumers suggest they are predominantly high income, female, highly educated, or younger,” says Velázquez Martínez. “However, our results show that the differences were the same between low and high income, women and men, and younger and older people. We have shown that disclosing emissions transparently and making the consumer a part of the strategy can be a new opportunity for more consumer-driven logistics sustainability.” 

      The researchers are now developing similar models for business-to-business (B2B) e-commerce. “We found that B2B supply chain emissions are often high because many shipping companies require strict delivery windows,” says Velázquez Martínez.  

      The B2B models drill down to examine the Corporate Value Chain (Scope 3) emissions of suppliers. “Although some shipping companies are now asking their suppliers to review emissions, it is a challenge to create a transparent supply chain,” says Velázquez Martínez.  “Technological innovations have made it easier, starting with RFID [radio frequency identification], and then real-time GPS mapping and blockchain. But these technologies need to be more accessible and affordable, and we need more companies willing to use them.” 

      Some companies have been hesitant to dig too deeply into their supply chain, fearing they might uncover a scandal that might risk their reputation, says Velázquez Martínez. Other organizations are forced to look at the issue when nongovernmental organizations research sustainability issues such as social injustice in sweat shops and conflict mineral mines. 

      One challenge to building a transparent supply chain is that “in many companies, the sustainability teams are separate from the rest of the company,” says Velázquez Martínez. “Even if the CEOs receive information on sustainability issues, it often doesn’t filter down because the information does not belong to the planners or managers. We are pushing companies to not only account for sustainability factors in supply chain network design but also examine daily operations that affect sustainability. This is a big topic now: How can we translate sustainability information into something that everybody can understand and use?” 

      LIFT Lab lifts micro-retailers  

      In 2016, Velázquez Martínez launched the MIT GeneSys project to gain insights into micro and small enterprises (MSEs) in developing countries. The project released a GeneSys mobile app, which was used by more than 500 students throughout Latin America to collect data on more than 800 microfirms. In 2022, he launched the LIFT Lab, which focuses more specifically on studying and improving the supply chain for MSEs.  

      Worldwide, some 90 percent of companies have fewer than 10 employees. In Latin America and the Caribbean, companies with fewer than 50 employees represent 99 percent of all companies and 47 percent of employment. 

      Although MSEs represent much of the world’s economy, they are poorly understood, notes Velázquez Martínez. “Those tiny businesses are driving a lot of the economy and serve as important customers for the large companies working in developing countries. They range from small businesses down to people trying to get some money to eat by selling cakes or tacos through their windows.”  

      The MIT LIFT Lab researchers investigated whether MSE supply chain issues could help shed light on why many Latin American countries have been limited to marginal increases in gross domestic product. “Large companies from the developed world that are operating in Latin America, such as Unilever, Walmart, and Coca-Cola, have huge growth there, in some cases higher than they have in the developed world,” says Velázquez Martínez. “Yet, the countries are not developing as fast as we would expect.” 

      The LIFT Lab data showed that while the multinationals are thriving in Latin America, the local MSEs are decreasing in productivity. The study also found the trend has worsened with Covid-19.  

      The LIFT Lab’s first big project, which is sponsored by Mexican beverage and retail company FEMSA, is studying supply chains in Mexico. The study spans 200,000 micro-retailers and 300,000 consumers. In a collaboration with Tecnológico de Monterrey, hundreds of students are helping with a field study.  

      “We are looking at supply chain management and business capabilities and identifying the challenges to adoption of technology and digitalization,” says Velázquez Martínez. “We want to find the best ways for micro-firms to work with suppliers and consumers by identifying the consumers who access this market, as well as the products and services that can best help the micro-firms drive growth.” 

      Based on the earlier research by GeneSys, Velázquez Martínez has developed some hypotheses for potential improvements for micro-retailer supply chain, starting with payment terms. “We found that the micro-firms often get the worst purchasing deals. Owners without credit cards and with limited cash often buy in smaller amounts at much higher prices than retailers like Walmart. The big suppliers are squeezing them.” 

      While large retailers usually get 60 to 120 days to pay, micro-retailers “either pay at the moment of the transaction or in advance,” says Velázquez Martínez. “In a study of 500 micro-retailers in five countries in Latin America, we found the average payment time was minus seven days payment in advance. These terms reduce cash availability and often lead to bankruptcy.” 

      LIFT Lab is working with suppliers to persuade them to offer a minimum payment time of two weeks. “We can show the suppliers that the change in terms will let them move more product and increase sales,” says Velázquez Martínez. “Meanwhile, the micro-retailers gain higher profits and become more stable, even if they may pay a bit more.” 

      LIFT Lab is also looking at ways that micro-retailers can leverage smartphones for digitalization and planning. “Some of these companies are keeping records on napkins,” says Velázquez Martínez. “By using a cellphone, they can charge orders to suppliers and communicate with consumers. We are testing different dashboards for mobile apps to help with planning and financial performance. We are also recommending services the stores can provide, such as paying electricity or water bills. The idea is to build more capabilities and knowledge and increase business competencies for the supply chain that are tailored for micro-retailers.” 

      From a financial perspective, micro-retailers are not always the most efficient way to move products. Yet they also play an important role in building social cohesion within neighborhoods. By offering more services, the corner bodega can bring people together in ways that are impossible with e-commerce and big-box stores.  

      Whether the consumers are micro-firms buying from suppliers or e-commerce customers waiting for packages, “transparency is key to building a sustainable supply chain,” says Velázquez Martínez. “To change consumer habits, consumers need to be better educated on the impacts of their behaviors. With consumer-facing logistics, ‘The last shall be first, and the first last.’” More

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      in Energy

      Q&A: Climate Grand Challenges finalists on new pathways to decarbonizing industry

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      Note: This is the third article in a four-part interview series highlighting the work of the 27 MIT Climate Grand Challenges finalist teams, which received a total of $2.7 million in startup funding to advance their projects. In April, the Institute will name a subset of the finalists as multiyear flagship projects.

      The industrial sector is the backbone of today’s global economy, yet its activities are among the most energy-intensive and the toughest to decarbonize. Efforts to reach net-zero targets and avert runaway climate change will not succeed without new solutions for replacing sources of carbon emissions with low-carbon alternatives and developing scalable nonemitting applications of hydrocarbons.

      In conversations prepared for MIT News, faculty from three of the teams with projects in the competition’s “Decarbonizing complex industries and processes” category discuss strategies for achieving impact in hard-to-abate sectors, from long-distance transportation and building construction to textile manufacturing and chemical refining. The other Climate Grand Challenges research themes include using data and science to forecast climate-related risk, building equity and fairness into climate solutions, and removing, managing, and storing greenhouse gases. The following responses have been edited for length and clarity.

      Moving toward an all-carbon material approach to building

      Faced with the prospect of building stock doubling globally by 2050, there is a great need for sustainable alternatives to conventional mineral- and metal-based construction materials. Mark Goulthorpe, associate professor in the Department of Architecture, explains the methods behind Carbon >Building, an initiative to develop energy-efficient building materials by reorienting hydrocarbons from current use as fuels to environmentally benign products, creating an entirely new genre of lightweight, all-carbon buildings that could actually drive decarbonization.

      Q: What are all-carbon buildings and how can they help mitigate climate change?

      A: Instead of burning hydrocarbons as fuel, which releases carbon dioxide and other greenhouse gases that contribute to atmospheric pollution, we seek to pioneer a process that uses carbon materially to build at macro scale. New forms of carbon — carbon nanotube, carbon foam, etc. — offer salient properties for building that might effectively displace the current material paradigm. Only hydrocarbons offer sufficient scale to beat out the billion-ton mineral and metal markets, and their perilous impact. Carbon nanotube from methane pyrolysis is of special interest, as it offers hydrogen as a byproduct.

      Q: How will society benefit from the widespread use of all-carbon buildings?

      A: We anticipate reducing costs and timelines in carbon composite buildings, while increasing quality, longevity, and performance, and diminishing environmental impact. Affordability of buildings is a growing problem in all global markets as the cost of labor and logistics in multimaterial assemblies creates a burden that is very detrimental to economic growth and results in overcrowding and urban blight.

      Alleviating these challenges would have huge societal benefits, especially for those in lower income brackets who cannot afford housing, but the biggest benefit would be in drastically reducing the environmental footprint of typical buildings, which account for nearly 40 percent of global energy consumption.

      An all-carbon building sector will not only reduce hydrocarbon extraction, but can produce higher value materials for building. We are looking to rethink the building industry by greatly streamlining global production and learning from the low-labor methods pioneered by composite manufacturing such as wind turbine blades, which are quick and cheap to produce. This technology can improve the sustainability and affordability of buildings — and holds the promise of faster, cheaper, greener, and more resilient modes of dwelling.

      Emissions reduction through innovation in the textile industry

      Collectively, the textile industry is responsible for over 4 billion metric tons of carbon dioxide equivalent per year, or 5 to 10 percent of global greenhouse gas emissions — more than aviation and maritime shipping combined. And the problem is only getting worse with the industry’s rapid growth. Under the current trajectory, consumption is projected to increase 30 percent by 2030, reaching 102 million tons. A diverse group of faculty and researchers led by Gregory Rutledge, the Lammot du Pont Professor in the Department of Chemical Engineering, and Yuly Fuentes-Medel, project manager for fiber technologies and research advisor to the MIT Innovation Initiative, is developing groundbreaking innovations to reshape how textiles are selected, sourced, designed, manufactured, and used, and to create the structural changes required for sustained reductions in emissions by this industry.

      Q: Why has the textile industry been difficult to decarbonize?

      A: The industry currently operates under a linear model that relies heavily on virgin feedstock, at roughly 97 percent, yet recycles or downcycles less than 15 percent. Furthermore, recent trends in “fast fashion” have led to massive underutilization of apparel, such that products are discarded on average after only seven to 10 uses. In an industry with high volume and low margins, replacement technologies must achieve emissions reduction at scale while maintaining performance and economic efficiency.

      There are also technical barriers to adopting circular business models, from the challenge of dealing with products comprising fiber blends and chemical additives to the low maturity of recycling technologies. The environmental impacts of textiles and apparel have been estimated using life cycle analysis, and industry-standard indexes are under development to assess sustainability throughout the life cycle of a product, but information and tools are needed to model how new solutions will alter those impacts and include the consumer as an active player to keep our planet safe. This project seeks to deliver both the new solutions and the tools to evaluate their potential for impact.

      Q: Describe the five components of your program. What is the anticipated timeline for implementing these solutions?

      A: Our plan comprises five programmatic sections, which include (1) enabling a paradigm shift to sustainable materials using nontraditional, carbon-negative polymers derived from biomass and additives that facilitate recycling; (2) rethinking manufacturing with processes to structure fibers and fabrics for performance, waste reduction, and increased material efficiency; (3) designing textiles for value by developing products that are customized, adaptable, and multifunctional, and that interact with their environment to reduce energy consumption; (4) exploring consumer behavior change through human interventions that reduce emissions by encouraging the adoption of new technologies, increased utilization of products, and circularity; and (5) establishing carbon transparency with systems-level analyses that measure the impact of these strategies and guide decision making.

      We have proposed a five-year timeline with annual targets for each project. Conservatively, we estimate our program could reduce greenhouse gas emissions in the industry by 25 percent by 2030, with further significant reductions to follow.

      Tough-to-decarbonize transportation

      Airplanes, transoceanic ships, and freight trucks are critical to transporting people and delivering goods, and the cornerstone of global commerce, manufacturing, and tourism. But these vehicles also emit 3.7 billion tons of carbon dioxide annually and, left unchecked, they could take up a quarter of the remaining carbon budget by 2050. William Green, the Hoyt C. Hottel Professor in the Department Chemical Engineering, co-leads a multidisciplinary team with Steven Barrett, professor of aeronautics and astronautics and director of the MIT Laboratory for Aviation and the Environment, that is working to identify and advance economically viable technologies and policies for decarbonizing heavy duty trucking, shipping, and aviation. The Tough to Decarbonize Transportation research program aims to design and optimize fuel chemistry and production, vehicles, operations, and policies to chart the course to net-zero emissions by midcentury.

      Q: What are the highest priority focus areas of your research program?

      A: Hydrocarbon fuels made from biomass are the least expensive option, but it seems impractical, and probably damaging to the environment, to harvest the huge amount of biomass that would be needed to meet the massive and growing energy demands from these sectors using today’s biomass-to-fuel technology. We are exploring strategies to increase the amount of useful fuel made per ton of biomass harvested, other methods to make low-climate-impact hydrocarbon fuels, such as from carbon dioxide, and ways to make fuels that do not contain carbon at all, such as with hydrogen, ammonia, and other hydrogen carriers.

      These latter zero-carbon options free us from the need for biomass or to capture gigatons of carbon dioxide, so they could be a very good long-term solution, but they would require changing the vehicles significantly, and the construction of new refueling infrastructure, with high capital costs.

      Q: What are the scientific, technological, and regulatory barriers to scaling and implementing potential solutions?

      A: Reimagining an aviation, trucking, and shipping sector that connects the world and increases equity without creating more environmental damage is challenging because these vehicles must operate disconnected from the electrical grid and have energy requirements that cannot be met by batteries alone. Some of the concepts do not even exist in prototype yet, and none of the appealing options have been implemented at anywhere near the scale required.

      In most cases, we do not know the best way to make the fuel, and for new fuels the vehicles and refueling systems all need to be developed. Also, new fuels, or large-scale use of biomass, will introduce new environmental problems that need to be carefully considered, to ensure that decarbonization solutions do not introduce big new problems.

      Perhaps most difficult are the policy, economic, and equity issues. A new long-haul transportation system will be expensive, and everyone will be affected by the increased cost of shipping freight. To have the desired climate impact, the transport system must change in almost every country. During the transition period, we will need both the existing vehicle and fuel system to keep running smoothly, even as a new low-greenhouse system is introduced. We will also examine what policies could make that work and how we can get countries around the world to agree to implement them. More

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      in Environment

      New maps show airplane contrails over the U.S. dropped steeply in 2020

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      As Covid-19’s initial wave crested around the world, travel restrictions and a drop in passengers led to a record number of grounded flights in 2020. The air travel reduction cleared the skies of not just jets but also the fluffy white contrails they produce high in the atmosphere.

      MIT engineers have mapped the contrails that were generated over the United States in 2020, and compared the results to prepandemic years. They found that on any given day in 2018, and again in 2019, contrails covered a total area equal to Massachusetts and Connecticut combined. In 2020, this contrail coverage shrank by about 20 percent, mirroring a similar drop in U.S. flights.  

      While 2020’s contrail dip may not be surprising, the findings are proof that the team’s mapping technique works. Their study marks the first time researchers have captured the fine and ephemeral details of contrails over a large continental scale.

      Now, the researchers are applying the technique to predict where in the atmosphere contrails are likely to form. The cloud-like formations are known to play a significant role in aviation-related global warming. The team is working with major airlines to forecast regions in the atmosphere where contrails may form, and to reroute planes around these regions to minimize contrail production.

      “This kind of technology can help divert planes to prevent contrails, in real time,” says Steven Barrett, professor and associate head of MIT’s Department of Aeronautics and Astronautics. “There’s an unusual opportunity to halve aviation’s climate impact by eliminating most of the contrails produced today.”

      Barrett and his colleagues have published their results today in the journal Environmental Research Letters. His co-authors at MIT include graduate student Vincent Meijer, former graduate student Luke Kulik, research scientists Sebastian Eastham, Florian Allroggen, and Raymond Speth, and LIDS Director and professor Sertac Karaman.

      Trail training

      About half of the aviation industry’s contribution to global warming comes directly from planes’ carbon dioxide emissions. The other half is thought to be a consequence of their contrails. The signature white tails are produced when a plane’s hot, humid exhaust mixes with cool humid air high in the atmosphere. Emitted in thin lines, contrails quickly spread out and can act as blankets that trap the Earth’s outgoing heat.

      While a single contrail may not have much of a warming effect, taken together contrails have a significant impact. But the estimates of this effect are uncertain and based on computer modeling as well as limited satellite data. What’s more, traditional computer vision algorithms that analyze contrail data have a hard time discerning the wispy tails from natural clouds.

      To precisely pick out and track contrails over a large scale, the MIT team looked to images taken by NASA’s GOES-16, a geostationary satellite that hovers over the same swath of the Earth, including the United States, taking continuous, high-resolution images.

      The team first obtained about 100 images taken by the satellite, and trained a set of people to interpret remote sensing data and label each image’s pixel as either part of a contrail or not. They used this labeled dataset to train a computer-vision algorithm to discern a contrail from a cloud or other image feature.

      The researchers then ran the algorithm on about 100,000 satellite images, amounting to nearly 6 trillion pixels, each pixel representing an area of about 2 square kilometers. The images covered the contiguous U.S., along with parts of Canada and Mexico, and were taken about every 15 minutes, between Jan. 1, 2018, and Dec. 31, 2020.

      The algorithm automatically classified each pixel as either a contrail or not a contrail, and generated daily maps of contrails over the United States. These maps mirrored the major flight paths of most U.S. airlines, with some notable differences. For instance, contrail “holes” appeared around major airports, which reflects the fact that planes landing and taking off around airports are generally not high enough in the atmosphere for contrails to form.

      “The algorithm knows nothing about where planes fly, and yet when processing the satellite imagery, it resulted in recognizable flight routes,” Barrett says. “That’s one piece of evidence that says this method really does capture contrails over a large scale.”

      Cloudy patterns

      Based on the algorithm’s maps, the researchers calculated the total area covered each day by contrails in the US. On an average day in 2018 and in 2019, U.S. contrails took up about 43,000 square kilometers. This coverage dropped by 20 percent in March of 2020 as the pandemic set in. From then on, contrails slowly reappeared as air travel resumed through the year.

      The team also observed daily and seasonal patterns. In general, contrails appeared to peak in the morning and decline in the afternoon. This may be a training artifact: As natural cirrus clouds are more likely to form in the afternoon, the algorithm may have trouble discerning contrails amid the clouds later in the day. But it might also be an important indication about when contrails form most. Contrails also peaked in late winter and early spring, when more of the air is naturally colder and more conducive for contrail formation.

      The team has now adapted the technique to predict where contrails are likely to form in real time. Avoiding these regions, Barrett says, could take a significant, almost immediate chunk out of aviation’s global warming contribution.  

      “Most measures to make aviation sustainable take a long time,” Barrett says. “(Contrail avoidance) could be accomplished in a few years, because it requires small changes to how aircraft are flown, with existing airplanes and observational technology. It’s a near-term way of reducing aviation’s warming by about half.”

      The team is now working towards this objective of large-scale contrail avoidance using realtime satellite observations.

      This research was supported in part by NASA and the MIT Environmental Solutions Initiative. More