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      in Environment

      Seeking climate connections among the oceans’ smallest organisms

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      Andrew Babbin tries to pack light for work trips. Along with the travel essentials, though, he also brings a roll each of electrical tape, duct tape, lab tape, a pack of cable ties, and some bungee cords.“It’s my MacGyver kit: You never know when you have to rig something on the fly in the field or fix a broken bag,” Babbin says.The trips Babbin takes are far out to sea, on month-long cruises, where he works to sample waters off the Pacific coast and out in the open ocean. In remote locations, repair essentials often come in handy, as when Babbin had to zip-tie a wrench to a sampling device to help it sink through an icy Antarctic lake.Babbin is an oceanographer and marine biogeochemist who studies marine microbes and the ways in which they control the cycling of nitrogen between the ocean and the atmosphere. This exchange helps maintain healthy ocean ecosystems and supports the ocean’s capacity to store carbon.By combining measurements that he takes in the ocean with experiments in his MIT lab, Babbin is working to understand the connections between microbes and ocean nitrogen, which could in turn help scientists identify ways to maintain the ocean’s health and productivity. His work has taken him to many coastal and open-ocean regions around the globe.“You really become an oceanographer and an Earth scientist to see the world,” says Babbin, who recently earned tenure as the Cecil and Ida Green Career Development Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We embrace the diversity of places and cultures on this planet. To see just a small fraction of that is special.”A powerful cycleThe ocean has been a constant presence for Babbin since childhood. His family is from Monmouth County, New Jersey, where he and his twin sister grew up playing along the Jersey shore. When they were teenagers, their parents took the kids on family cruise vacations.“I always loved being on the water,” he says. “My favorite parts of any of those cruises were the days at sea, where you were just in the middle of some ocean basin with water all around you.”In school, Babbin gravitated to the sciences, and chemistry in particular. After high school, he attended Columbia University, where a visit to the school’s Earth and environmental engineering department catalyzed a realization.“For me, it was always this excitement about the water and about chemistry, and it was this pop of, ‘Oh wow, it doesn’t have to be one or the other,’” Babbin says.He chose to major in Earth and environmental engineering, with a concentration in water resources and climate risks. After graduating in 2008, Babbin returned to his home state, where he attended Princeton University and set a course for a PhD in geosciences, with a focus on chemical oceanography and environmental microbiology. His advisor, oceanographer Bess Ward, took Babbin on as a member of her research group and invited him on several month-long cruises to various parts of the eastern tropical Pacific.“I still remember that first trip,” Babbin recalls. “It was a whirlwind. Everyone else had been to sea a gazillion times and was loading the boat and strapping things down, and I had no idea of anything. And within a few hours, I was doing an experiment as the ship rocked back and forth!”Babbin learned to deploy sampling cannisters overboard, then haul them back up and analyze the seawater inside for signs of nitrogen — an essential nutrient for all living things on Earth.As it turns out, the plants and animals that depend on nitrogen to survive are unable to take it up from the atmosphere themselves. They require a sort of go-between, in the form of microbes that “fix” nitrogen, converting it from nitrogen gas to more digestible forms. In the ocean, this nitrogen fixation is done by highly specialized microbial species, which work to make nitrogen available to phytoplankton — microscopic plant-like organisms that are the foundation of the marine food chain. Phytoplankton are also a main route by which the ocean absorbs carbon dioxide from the atmosphere.Microorganisms may also use these biologically available forms of nitrogen for energy under certain conditions, returning nitrogen to the atmosphere. These microbes can also release a byproduct of nitrous oxide, which is a potent greenhouse gas that also can catalyze ozone loss in the stratosphere.Through his graduate work, at sea and in the lab, Babbin became fascinated with the cycling of nitrogen and the role that nitrogen-fixing microbes play in supporting the ocean’s ecosystems and the climate overall. A balance of nitrogen inputs and outputs sustains phytoplankton and maintains the ocean’s ability to soak up carbon dioxide.“Some of the really pressing questions in ocean biogeochemistry pertain to this cycling of nitrogen,” Babbin says. “Understanding the ways in which this one element cycles through the ocean, and how it is central to ecosystem health and the planet’s climate, has been really powerful.”In the lab and out to seaAfter completing his PhD in 2014, Babbin arrived at MIT as a postdoc in the Department of Civil and Environmental Engineering.“My first feeling when I came here was, wow, this really is a nerd’s playground,” Babbin says. “I embraced being part of a culture where we seek to understand the world better, while also doing the things we really want to do.”In 2017, he accepted a faculty position in MIT’s Department of Earth, Atmospheric and Planetary Sciences. He set up his laboratory space, painted in his favorite brilliant orange, on the top floor of the Green Building.His group uses 3D printers to fabricate microfluidic devices in which they reproduce the conditions of the ocean environment and study microbe metabolism and its effects on marine chemistry. In the field, Babbin has led research expeditions to the Galapagos Islands and parts of the eastern Pacific, where he has collected and analyzed samples of air and water for signs of nitrogen transformations and microbial activity. His new measuring station in the Galapagos is able to infer marine emissions of nitrous oxide across a large swath of the eastern tropical Pacific Ocean. His group has also sailed to southern Cuba, where the researchers studied interactions of microbes in coral reefs.Most recently, Babbin traveled to Antarctica, where he set up camp next to frozen lakes and plumbed for samples of pristine ice water that he will analyze for genetic remnants of ancient microbes. Such preserved bacterial DNA could help scientists understand how microbes evolved and influenced the Earth’s climate over billions of years.“Microbes are the terraformers,” Babbin notes. “They have been, since life evolved more than 3 billion years ago. We have to think about how they shape the natural world and how they will respond to the Anthropocene as humans monkey with the planet ourselves.”Collective actionBabbin is now charting new research directions. In addition to his work at sea and in the lab, he is venturing into engineering, with a new project to design denitrifying capsules. While nitrogen is an essential nutrient for maintaining a marine ecosystem, too much nitrogen, such as from fertilizer that runs off into lakes and streams, can generate blooms of toxic algae. Babbin is looking to design eco-friendly capsules that scrub excess anthropogenic nitrogen from local waterways. He’s also beginning the process of designing a new sensor to measure low-oxygen concentrations in the ocean. As the planet warms, the oceans are losing oxygen, creating “dead zones” where fish cannot survive. While others including Babbin have tried to map these oxygen minimum zones, or OMZs, they have done so sporadically, by dropping sensors into the ocean over limited range, depth, and times. Babbin’s sensors could potentially provide a more complete map of OMZs, as they would be deployed on wide-ranging, deep-diving, and naturally propulsive vehicles: sharks.“We want to measure oxygen. Sharks need oxygen. And if you look at where the sharks don’t go, you might have a sense of where the oxygen is not,” says Babbin, who is working with marine biologists on ways to tag sharks with oxygen sensors. “A number of these large pelagic fish move up and down the water column frequently, so you can map the depth to which they dive to, and infer something about the behavior. And my suggestion is, you might also infer something about the ocean’s chemistry.”When he reflects on what stimulates new ideas and research directions, Babbin credits working with others, in his own group and across MIT.“My best thoughts come from this collective action,” Babbin says. “Particularly because we all have different upbringings and approach things from a different perspective.”He’s bringing this collaborative spirit to his new role, as a mission director for MIT’s Climate Project. Along with Jesse Kroll, who is a professor of civil and environmental engineering and of chemical engineering, Babbin co-leads one of the project’s six missions: Restoring the Atmosphere, Protecting the Land and Oceans. Babbin and Kroll are planning a number of workshops across campus that they hope will generate new connections, and spark new ideas, particularly around ways to evaluate the effectiveness of different climate mitigation strategies and better assess the impacts of climate on society.“One area we want to promote is thinking of climate science and climate interventions as two sides of the same coin,” Babbin says. “There’s so much action that’s trying to be catalyzed. But we want it to be the best action. Because we really have one shot at doing this. Time is of the essence.” More

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      in Environment

      David McGee named head of the Department of Earth, Atmospheric and Planetary Sciences

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      David McGee, the William R. Kenan Jr. Professor of Earth and Planetary Sciences at MIT, was recently appointed head of the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS), effective Jan. 15. He assumes the role from Professor Robert van der Hilst, the Schlumberger Professor of Earth and Planetary Sciences, who led the department for 13 years.McGee specializes in applying isotope geochemistry and geochronology to reconstruct Earth’s climate history, helping to ground-truth our understanding of how the climate system responds during periods of rapid change. He has also been instrumental in the growth of the department’s community and culture, having served as EAPS associate department head since 2020.“David is an amazing researcher who brings crucial, data-based insights to aid our response to climate change,” says dean of the School of Science and the Curtis (1963) and Kathleen Marble Professor of Astrophysics Nergis Mavalvala. “He is also a committed and caring educator, providing extraordinary investment in his students’ learning experiences, and through his direction of Terrascope, one of our unique first-year learning communities focused on generating solutions to sustainability challenges.”   “I am energized by the incredible EAPS community, by Rob’s leadership over the last 13 years, and by President Kornbluth’s call for MIT to innovate effective and wise responses to climate change,” says McGee. “EAPS has a unique role in this time of reckoning with planetary boundaries — our collective path forward needs to be guided by a deep understanding of the Earth system and a clear sense of our place in the universe.”McGee’s research seeks to understand the Earth system’s response to past climate changes. Using geochemical analysis and uranium-series dating, McGee and his group investigate stalagmites, ancient lake deposits, and deep-sea sediments from field sites around the world to trace patterns of wind and precipitation, water availability in drylands, and permafrost stability through space and time. Armed with precise chronologies, he aims to shed light on drivers of historical hydroclimatic shifts and provide quantitative tests of climate model performance.Beyond research, McGee has helped shape numerous Institute initiatives focused on environment, climate, and sustainability, including serving on the MIT Climate and Sustainability Consortium Faculty Steering Committee and the faculty advisory board for the MIT Environment and Sustainability Minor.McGee also co-chaired MIT’s Climate Education Working Group, one of three working groups established under the Institute’s Fast Forward climate action plan. The group identified opportunities to strengthen climate- and sustainability-related education at the Institute, from curricular offerings to experiential learning opportunities and beyond.In April 2023, the working group hosted the MIT Symposium for Advancing Climate Education, featuring talks by McGee and others on how colleges and universities can innovate and help students develop the skills, capacities, and perspectives they’ll need to live, lead, and thrive in a world being remade by the accelerating climate crisis.“David is reimagining MIT undergraduate education to include meaningful collaborations with communities outside of MIT, teaching students that scientific discovery is important, but not always enough to make impact for society,” says van der Hilst. “He will help shape the future of the department with this vital perspective.”From the start of his career, McGee has been dedicated to sharing his love of exploration with students. He earned a master’s degree in teaching and spent seven years as a teacher in middle school and high school classrooms before earning his PhD in Earth and environmental sciences from Columbia University. He joined the MIT faculty in 2012, and in 2018 received the Excellence in Mentoring Award from MIT’s Undergraduate Advising and Academic Programming office. In 2015, he became the director of MIT’s Terrascope first-year learning community.“David’s exemplary teaching in Terrascope comes through his understanding that effective solutions must be found where science intersects with community engagement to forge ethical paths forward,” adds van der Hilst. In 2023, for his work with Terrascope, McGee received the school’s highest award, the School of Science Teaching Prize. In 2022, he was named a Margaret MacVicar Faculty Fellow, the highest teaching honor at MIT.As associate department head, McGee worked alongside van der Hilst and student leaders to promote EAPS community engagement, improve internal supports and reporting structures, and bolster opportunities for students to pursue advanced degrees and STEM careers. More

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      in Energy

      Smart carbon dioxide removal yields economic and environmental benefits

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      Last year the Earth exceeded 1.5 degrees Celsius of warming above preindustrial times, a threshold beyond which wildfires, droughts, floods, and other climate impacts are expected to escalate in frequency, intensity, and lethality. To cap global warming at 1.5 C and avert that scenario, the nearly 200 signatory nations of the Paris Agreement on climate change will need to not only dramatically lower their greenhouse gas emissions, but also take measures to remove carbon dioxide (CO2) from the atmosphere and durably store it at or below the Earth’s surface.Past analyses of the climate mitigation potential, costs, benefits, and drawbacks of different carbon dioxide removal (CDR) options have focused primarily on three strategies: bioenergy with carbon capture and storage (BECCS), in which CO2-absorbing plant matter is converted into fuels or directly burned to generate energy, with some of the plant’s carbon content captured and then stored safely and permanently; afforestation/reforestation, in which CO2-absorbing trees are planted in large numbers; and direct air carbon capture and storage (DACCS), a technology that captures and separates CO2 directly from ambient air, and injects it into geological reservoirs or incorporates it into durable products. To provide a more comprehensive and actionable analysis of CDR, a new study by researchers at the MIT Center for Sustainability Science and Strategy (CS3) first expands the option set to include biochar (charcoal produced from plant matter and stored in soil) and enhanced weathering (EW) (spreading finely ground rock particles on land to accelerate storage of CO2 in soil and water). The study then evaluates portfolios of all five options — in isolation and in combination — to assess their capability to meet the 1.5 C goal, and their potential impacts on land, energy, and policy costs.The study appears in the journal Environmental Research Letters. Aided by their global multi-region, multi-sector Economic Projection and Policy Analysis (EPPA) model, the MIT CS3 researchers produce three key findings.First, the most cost-effective, low-impact strategy that policymakers can take to achieve global net-zero emissions — an essential step in meeting the 1.5 C goal — is to diversify their CDR portfolio, rather than rely on any single option. This approach minimizes overall cropland and energy consumption, and negative impacts such as increased food insecurity and decreased energy supplies.By diversifying across multiple CDR options, the highest CDR deployment of around 31.5 gigatons of CO2 per year is achieved in 2100, while also proving the most cost-effective net-zero strategy. The study identifies BECCS and biochar as most cost-competitive in removing CO2 from the atmosphere, followed by EW, with DACCS as uncompetitive due to high capital and energy requirements. While posing logistical and other challenges, biochar and EW have the potential to improve soil quality and productivity across 45 percent of all croplands by 2100.“Diversifying CDR portfolios is the most cost-effective net-zero strategy because it avoids relying on a single CDR option, thereby reducing and redistributing negative impacts on agriculture, forestry, and other land uses, as well as on the energy sector,” says Solene Chiquier, lead author of the study who was a CS3 postdoc during its preparation.The second finding: There is no optimal CDR portfolio that will work well at global and national levels. The ideal CDR portfolio for a particular region will depend on local technological, economic, and geophysical conditions. For example, afforestation and reforestation would be of great benefit in places like Brazil, Latin America, and Africa, by not only sequestering carbon in more acreage of protected forest but also helping to preserve planetary well-being and human health.“In designing a sustainable, cost-effective CDR portfolio, it is important to account for regional availability of agricultural, energy, and carbon-storage resources,” says Sergey Paltsev, CS3 deputy director, MIT Energy Initiative senior research scientist, and supervising co-author of the study. “Our study highlights the need for enhancing knowledge about local conditions that favor some CDR options over others.”Finally, the MIT CS3 researchers show that delaying large-scale deployment of CDR portfolios could be very costly, leading to considerably higher carbon prices across the globe — a development sure to deter the climate mitigation efforts needed to achieve the 1.5 C goal. They recommend near-term implementation of policy and financial incentives to help fast-track those efforts. More

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      in Energy

      MIT Climate and Energy Ventures class spins out entrepreneurs — and successful companies

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      In 2014, a team of MIT students in course 15.366 (Climate and Energy Ventures) developed a plan to commercialize MIT research on how to move information between chips with light instead of electricity, reducing energy usage.After completing the class, which challenges students to identify early customers and pitch their business plan to investors, the team went on to win both grand prizes at the MIT Clean Energy Prize. Today the company, Ayar Labs, has raised a total of $370 million from a group including chip leaders AMD, Intel, and NVIDIA, to scale the manufacturing of its optical chip interconnects.Ayar Labs is one of many companies whose roots can be traced back to 15.366. In fact, more than 150 companies have been founded by alumni of the class since its founding in 2007.In the class, student teams select a technology or idea and determine the best path for its commercialization. The semester-long project, which is accompanied by lectures and mentoring, equips students with real-world experience in launching a business.“The goal is to educate entrepreneurs on how to start companies in the climate and energy space,” says Senior Lecturer Tod Hynes, who co-founded the course and has been teaching since 2008. “We do that through hands-on experience. We require students to engage with customers, talk to potential suppliers, partners, investors, and to practice their pitches to learn from that feedback.”The class attracts hundreds of student applications each year. As one of the catalysts for MIT spinoffs, it is also one reason a 2015 report found that MIT alumni-founded companies had generated roughly $1.9 trillion in annual revenues. If MIT were a country, that figure that would make it the 10th largest economy in the world, according to the report.“’Mens et manus’ (‘mind and hand’) is MIT’s motto, and the hands-on experience we try to provide in this class is hard to beat,” Hynes says. “When you actually go through the process of commercialization in the real world, you learn more and you’re in a better spot. That experiential learning approach really aligns with MIT’s approach.”Simulating a startupThe course was started by Bill Aulet, a professor of the practice at the MIT Sloan School of Management and the managing director of the Martin Trust Center for MIT Entrepreneurship. After serving as an advisor the first year and helping Aulet launch the class, Hynes began teaching the class with Aulet in the fall of 2008. The pair also launched the Climate and Energy Prize around the same time, which continues today and recently received over 150 applications from teams from around the world.A core feature of the class is connecting students in different academic fields. Each year, organizers aim to enroll students with backgrounds in science, engineering, business, and policy.“The class is meant to be accessible to anybody at MIT,” Hynes says, noting the course has also since opened to students from Harvard University. “We’re trying to pull across disciplines.”The class quickly grew in popularity around campus. Over the last few years, the course has had about 150 students apply for 50 spots.“I mentioned Climate and Energy Ventures in my application to MIT,” says Chris Johnson, a second-year graduate student in the Leaders for Global Operations (LGO) Program. “Coming into MIT, I was very interested in sustainability, and energy in particular, and also in startups. I had heard great things about the class, and I waited until my last semester to apply.”The course’s organizers select mostly graduate students, whom they prefer to be in the final year of their program so they can more easily continue working on the venture after the class is finished.“Whether or not students stick with the project from the class, it’s a great experience that will serve them in their careers,” says Jennifer Turliuk, the practice leader for climate and energy artificial intelligence at the Martin Trust Center for Entrepreneurship, who helped teach the class this fall.Hynes describes the course as a venture-building simulation. Before it begins, organizers select up to 30 technologies and ideas that are in the right stage for commercialization. Students can also come into the class with ideas or technologies they want to work on.After a few weeks of introductions and lectures, students form into multidisciplinary teams of about five and begin going through each of the 24 steps of building a startup described in Aulet’s book “Disciplined Entrepreneurship,” which includes things like engaging with potential early customers, quantifying a value proposition, and establishing a business model. Everything builds toward a one-hour final presentation that’s designed to simulate a pitch to investors or government officials.“It’s a lot of work, and because it’s a team-based project, your grade is highly dependent on your team,” Hynes says. “You also get graded by your team; that’s about 10 percent of your grade. We try to encourage people to be proactive and supportive teammates.”Students say the process is fast-paced but rewarding.“It’s definitely demanding,” says Sofie Netteberg, a graduate student who is also in the LGO program at MIT. “Depending on where you’re at with your technology, you can be moving very quickly. That’s the stage that I was in, which I found really engaging. We basically just had a lab technology, and it was like, ‘What do we do next?’ You also get a ton of support from the professors.”From the classroom to the worldThis fall’s final presentations took place at the headquarters of the MIT-affiliated venture firm The Engine in front of an audience of professors, investors, members of foundations supporting entrepreneurship, and more.“We got to hear feedback from people who would be the real next step for the technology if the startup gets up and running,” said Johnson, whose team was commercializing a method for storing energy in concrete. “That was really valuable. We know that these are not only people we might see in the next month or the next funding rounds, but they’re also exactly the type of people that are going to give us the questions we should be thinking about. It was clarifying.”Throughout the semester, students treated the project like a real venture they’d be working on well beyond the length of the class.“No one’s really thinking about this class for the grade; it’s about the learning,” says Netteberg, whose team was encouraged to keep working on their electrolyzer technology designed to more efficiently produce green hydrogen. “We’re not stressed about getting an A. If we want to keep working on this, we want real feedback: What do you think we did well? What do we need to keep working on?”Hynes says several investors expressed interest in supporting the businesses coming out of the class. Moving forward, he hopes students embrace the test-bed environment his team has created for them and try bold new things.“People have been very pragmatic over the years, which is good, but also potentially limiting,” Hynes says. “This is also an opportunity to do something that’s a little further out there — something that has really big potential impact if it comes together. This is the time where students get to experiment, so why not try something big?” More

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      in Energy

      Toward sustainable decarbonization of aviation in Latin America

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      According to the International Energy Agency, aviation accounts for about 2 percent of global carbon dioxide emissions, and aviation emissions are expected to double by mid-century as demand for domestic and international air travel rises. To sharply reduce emissions in alignment with the Paris Agreement’s long-term goal to keep global warming below 1.5 degrees Celsius, the International Air Transport Association (IATA) has set a goal to achieve net-zero carbon emissions by 2050. Which raises the question: Are there technologically feasible and economically viable strategies to reach that goal within the next 25 years?To begin to address that question, a team of researchers at the MIT Center for Sustainability Science and Strategy (CS3) and the MIT Laboratory for Aviation and the Environment has spent the past year analyzing aviation decarbonization options in Latin America, where air travel is expected to more than triple by 2050 and thereby double today’s aviation-related emissions in the region.Chief among those options is the development and deployment of sustainable aviation fuel. Currently produced from low- and zero-carbon sources (feedstock) including municipal waste and non-food crops, and requiring practically no alteration of aircraft systems or refueling infrastructure, sustainable aviation fuel (SAF) has the potential to perform just as well as petroleum-based jet fuel with as low as 20 percent of its carbon footprint.Focused on Brazil, Chile, Colombia, Ecuador, Mexico and Peru, the researchers assessed SAF feedstock availability, the costs of corresponding SAF pathways, and how SAF deployment would likely impact fuel use, prices, emissions, and aviation demand in each country. They also explored how efficiency improvements and market-based mechanisms could help the region to reach decarbonization targets. The team’s findings appear in a CS3 Special Report.SAF emissions, costs, and sourcesUnder an ambitious emissions mitigation scenario designed to cap global warming at 1.5 C and raise the rate of SAF use in Latin America to 65 percent by 2050, the researchers projected aviation emissions to be reduced by about 60 percent in 2050 compared to a scenario in which existing climate policies are not strengthened. To achieve net-zero emissions by 2050, other measures would be required, such as improvements in operational and air traffic efficiencies, airplane fleet renewal, alternative forms of propulsion, and carbon offsets and removals.As of 2024, jet fuel prices in Latin America are around $0.70 per liter. Based on the current availability of feedstocks, the researchers projected SAF costs within the six countries studied to range from $1.11 to $2.86 per liter. They cautioned that increased fuel prices could affect operating costs of the aviation sector and overall aviation demand unless strategies to manage price increases are implemented.Under the 1.5 C scenario, the total cumulative capital investments required to build new SAF producing plants between 2025 and 2050 were estimated at $204 billion for the six countries (ranging from $5 billion in Ecuador to $84 billion in Brazil). The researchers identified sugarcane- and corn-based ethanol-to-jet fuel, palm oil- and soybean-based hydro-processed esters and fatty acids as the most promising feedstock sources in the near term for SAF production in Latin America.“Our findings show that SAF offers a significant decarbonization pathway, which must be combined with an economy-wide emissions mitigation policy that uses market-based mechanisms to offset the remaining emissions,” says Sergey Paltsev, lead author of the report, MIT CS3 deputy director, and senior research scientist at the MIT Energy Initiative.RecommendationsThe researchers concluded the report with recommendations for national policymakers and aviation industry leaders in Latin America.They stressed that government policy and regulatory mechanisms will be needed to create sufficient conditions to attract SAF investments in the region and make SAF commercially viable as the aviation industry decarbonizes operations. Without appropriate policy frameworks, SAF requirements will affect the cost of air travel. For fuel producers, stable, long-term-oriented policies and regulations will be needed to create robust supply chains, build demand for establishing economies of scale, and develop innovative pathways for producing SAF.Finally, the research team recommended a region-wide collaboration in designing SAF policies. A unified decarbonization strategy among all countries in the region will help ensure competitiveness, economies of scale, and achievement of long-term carbon emissions-reduction goals.“Regional feedstock availability and costs make Latin America a potential major player in SAF production,” says Angelo Gurgel, a principal research scientist at MIT CS3 and co-author of the study. “SAF requirements, combined with government support mechanisms, will ensure sustainable decarbonization while enhancing the region’s connectivity and the ability of disadvantaged communities to access air transport.”Financial support for this study was provided by LATAM Airlines and Airbus. More

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      in Environment

      An abundant phytoplankton feeds a global network of marine microbes

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      One of the hardest-working organisms in the ocean is the tiny, emerald-tinged Prochlorococcus marinus. These single-celled “picoplankton,” which are smaller than a human red blood cell, can be found in staggering numbers throughout the ocean’s surface waters, making Prochlorococcus the most abundant photosynthesizing organism on the planet. (Collectively, Prochlorococcus fix as much carbon as all the crops on land.) Scientists continue to find new ways that the little green microbe is involved in the ocean’s cycling and storage of carbon.Now, MIT scientists have discovered a new ocean-regulating ability in the small but mighty microbes: cross-feeding of DNA building blocks. In a study appearing today in Science Advances, the team reports that Prochlorococcus shed these extra compounds into their surroundings, where they are then “cross-fed,” or taken up by other ocean organisms, either as nutrients, energy, or for regulating metabolism. Prochlorococcus’ rejects, then, are other microbes’ resources.What’s more, this cross-feeding occurs on a regular cycle: Prochlorococcus tend to shed their molecular baggage at night, when enterprising microbes quickly consume the cast-offs. For a microbe called SAR11, the most abundant bacteria in the ocean, the researchers found that the nighttime snack acts as a relaxant of sorts, forcing the bacteria to slow down their metabolism and effectively recharge for the next day.Through this cross-feeding interaction, Prochlorococcus could be helping many microbial communities to grow sustainably, simply by giving away what it doesn’t need. And they’re doing so in a way that could set the daily rhythms of microbes around the world.“The relationship between the two most abundant groups of microbes in ocean ecosystems has intrigued oceanographers for years,” says co-author and MIT Institute Professor Sallie “Penny” Chisholm, who played a role in the discovery of Prochlorococcus in 1986. “Now we have a glimpse of the finely tuned choreography that contributes to their growth and stability across vast regions of the oceans.”Given that Prochlorococcus and SAR11 suffuse the surface oceans, the team suspects that the exchange of molecules from one to the other could amount to one of the major cross-feeding relationships in the ocean, making it an important regulator of the ocean carbon cycle.“By looking at the details and diversity of cross-feeding processes, we can start to unearth important forces that are shaping the carbon cycle,” says the study’s lead author, Rogier Braakman, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).Other MIT co-authors include Brandon Satinsky, Tyler O’Keefe, Shane Hogle, Jamie Becker, Robert Li, Keven Dooley, and Aldo Arellano, along with Krista Longnecker, Melissa Soule, and Elizabeth Kujawinski of Woods Hole Oceanographic Institution (WHOI).Spotting castawaysCross-feeding occurs throughout the microbial world, though the process has mainly been studied in close-knit communities. In the human gut, for instance, microbes are in close proximity and can easily exchange and benefit from shared resources.By comparison, Prochlorococcus are free-floating microbes that are regularly tossed and mixed through the ocean’s surface layers. While scientists assume that the plankton are involved in some amount of cross-feeding, exactly how this occurs, and who would benefit, have historically been challenging to probe; any stuff that Prochlorococcus cast away would have vanishingly low concentrations,and be exceedingly difficult to measure.But in work published in 2023, Braakman teamed up with scientists at WHOI, who pioneered ways to measure small organic compounds in seawater. In the lab, they grew various strains of Prochlorococcus under different conditions and characterized what the microbes released. They found that among the major “exudants,” or released molecules, were purines and pyridines, which are molecular building blocks of DNA. The molecules also happen to be nitrogen-rich — a fact that puzzled the team. Prochlorococcus are mainly found in ocean regions that are low in nitrogen, so it was assumed they’d want to retain any and all nitrogen-containing compounds they can. Why, then, were they instead throwing such compounds away?Global symphonyIn their new study, the researchers took a deep dive into the details of Prochlorococcus’ cross-feeding and how it influences various types of ocean microbes.They set out to study how Prochlorococcus use purine and pyridine in the first place, before expelling the compounds into their surroundings. They compared published genomes of the microbes, looking for genes that encode purine and pyridine metabolism. Tracing the genes forward through the genomes, the team found that once the compounds are produced, they are used to make DNA and replicate the microbes’ genome. Any leftover purine and pyridine is recycled and used again, though a fraction of the stuff is ultimately released into the environment. Prochlorococcus appear to make the most of the compounds, then cast off what they can’t.The team also looked to gene expression data and found that genes involved in recycling purine and pyrimidine peak several hours after the recognized peak in genome replication that occurs at dusk. The question then was: What could be benefiting from this nightly shedding?For this, the team looked at the genomes of more than 300 heterotrophic microbes — organisms that consume organic carbon rather than making it themselves through photosynthesis. They suspected that such carbon-feeders could be likely consumers of Prochlorococcus’ organic rejects. They found most of the heterotrophs contained genes that take up either purine or pyridine, or in some cases, both, suggesting microbes have evolved along different paths in terms of how they cross-feed.The group zeroed in on one purine-preferring microbe, SAR11, as it is the most abundant heterotrophic microbe in the ocean. When they then compared the genes across different strains of SAR11, they found that various types use purines for different purposes, from simply taking them up and using them intact to breaking them down for their energy, carbon, or nitrogen. What could explain the diversity in how the microbes were using Prochlorococcus’ cast-offs?It turns out the local environment plays a big role. Braakman and his collaborators performed a metagenome analysis in which they compared the collectively sequenced genomes of all microbes in over 600 seawater samples from around the world, focusing on SAR11 bacteria. Metagenome sequences were collected alongside measurements of various environmental conditions and geographic locations in which they are found. This analysis showed that the bacteria gobble up purine for its nitrogen when the nitrogen in seawater is low, and for its carbon or energy when nitrogen is in surplus — revealing the selective pressures shaping these communities in different ocean regimes.“The work here suggests that microbes in the ocean have developed relationships that advance their growth potential in ways we don’t expect,” says co-author Kujawinski.Finally, the team carried out a simple experiment in the lab, to see if they could directly observe a mechanism by which purine acts on SAR11. They grew the bacteria in cultures, exposed them to various concentrations of purine, and unexpectedly found it causes them to slow down their normal metabolic activities and even growth. However, when the researchers put these same cells under environmentally stressful conditions, they continued growing strong and healthy cells, as if the metabolic pausing by purines helped prime them for growth, thereby avoiding the effects of the stress.“When you think about the ocean, where you see this daily pulse of purines being released by Prochlorococcus, this provides a daily inhibition signal that could be causing a pause in SAR11 metabolism, so that the next day when the sun comes out, they are primed and ready,” Braakman says. “So we think Prochlorococcus is acting as a conductor in the daily symphony of ocean metabolism, and cross-feeding is creating a global synchronization among all these microbial cells.”This work was supported, in part, by the Simons Foundation and the National Science Foundation. More

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      in Energy

      New climate chemistry model finds “non-negligible” impacts of potential hydrogen fuel leakage

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      As the world looks for ways to stop climate change, much discussion focuses on using hydrogen instead of fossil fuels, which emit climate-warming greenhouse gases (GHGs) when they’re burned. The idea is appealing. Burning hydrogen doesn’t emit GHGs to the atmosphere, and hydrogen is well-suited for a variety of uses, notably as a replacement for natural gas in industrial processes, power generation, and home heating.But while burning hydrogen won’t emit GHGs, any hydrogen that’s leaked from pipelines or storage or fueling facilities can indirectly cause climate change by affecting other compounds that are GHGs, including tropospheric ozone and methane, with methane impacts being the dominant effect. A much-cited 2022 modeling study analyzing hydrogen’s effects on chemical compounds in the atmosphere concluded that these climate impacts could be considerable. With funding from the MIT Energy Initiative’s Future Energy Systems Center, a team of MIT researchers took a more detailed look at the specific chemistry that poses the risks of using hydrogen as a fuel if it leaks.The researchers developed a model that tracks many more chemical reactions that may be affected by hydrogen and includes interactions among chemicals. Their open-access results, published Oct. 28 in Frontiers in Energy Research, showed that while the impact of leaked hydrogen on the climate wouldn’t be as large as the 2022 study predicted — and that it would be about a third of the impact of any natural gas that escapes today — leaked hydrogen will impact the climate. Leak prevention should therefore be a top priority as the hydrogen infrastructure is built, state the researchers.Hydrogen’s impact on the “detergent” that cleans our atmosphereGlobal three-dimensional climate-chemistry models using a large number of chemical reactions have also been used to evaluate hydrogen’s potential climate impacts, but results vary from one model to another, motivating the MIT study to analyze the chemistry. Most studies of the climate effects of using hydrogen consider only the GHGs that are emitted during the production of the hydrogen fuel. Different approaches may make “blue hydrogen” or “green hydrogen,” a label that relates to the GHGs emitted. Regardless of the process used to make the hydrogen, the fuel itself can threaten the climate. For widespread use, hydrogen will need to be transported, distributed, and stored — in short, there will be many opportunities for leakage. The question is, What happens to that leaked hydrogen when it reaches the atmosphere? The 2022 study predicting large climate impacts from leaked hydrogen was based on reactions between pairs of just four chemical compounds in the atmosphere. The results showed that the hydrogen would deplete a chemical species that atmospheric chemists call the “detergent of the atmosphere,” explains Candice Chen, a PhD candidate in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “It goes around zapping greenhouse gases, pollutants, all sorts of bad things in the atmosphere. So it’s cleaning our air.” Best of all, that detergent — the hydroxyl radical, abbreviated as OH — removes methane, which is an extremely potent GHG in the atmosphere. OH thus plays an important role in slowing the rate at which global temperatures rise. But any hydrogen leaked to the atmosphere would reduce the amount of OH available to clean up methane, so the concentration of methane would increase.However, chemical reactions among compounds in the atmosphere are notoriously complicated. While the 2022 study used a “four-equation model,” Chen and her colleagues — Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies and Chemistry; and Kane Stone, a research scientist in EAPS — developed a model that includes 66 chemical reactions. Analyses using their 66-equation model showed that the four-equation system didn’t capture a critical feedback involving OH — a feedback that acts to protect the methane-removal process.Here’s how that feedback works: As the hydrogen decreases the concentration of OH, the cleanup of methane slows down, so the methane concentration increases. However, that methane undergoes chemical reactions that can produce new OH radicals. “So the methane that’s being produced can make more of the OH detergent,” says Chen. “There’s a small countering effect. Indirectly, the methane helps produce the thing that’s getting rid of it.” And, says Chen, that’s a key difference between their 66-equation model and the four-equation one. “The simple model uses a constant value for the production of OH, so it misses that key OH-production feedback,” she says.To explore the importance of including that feedback effect, the MIT researchers performed the following analysis: They assumed that a single pulse of hydrogen was injected into the atmosphere and predicted the change in methane concentration over the next 100 years, first using four-equation model and then using the 66-equation model. With the four-equation system, the additional methane concentration peaked at nearly 2 parts per billion (ppb); with the 66-equation system, it peaked at just over 1 ppb.Because the four-equation analysis assumes only that the injected hydrogen destroys the OH, the methane concentration increases unchecked for the first 10 years or so. In contrast, the 66-equation analysis goes one step further: the methane concentration does increase, but as the system re-equilibrates, more OH forms and removes methane. By not accounting for that feedback, the four-equation analysis overestimates the peak increase in methane due to the hydrogen pulse by about 85 percent. Spread over time, the simple model doubles the amount of methane that forms in response to the hydrogen pulse.Chen cautions that the point of their work is not to present their result as “a solid estimate” of the impact of hydrogen. Their analysis is based on a simple “box” model that represents global average conditions and assumes that all the chemical species present are well mixed. Thus, the species can vary over time — that is, they can be formed and destroyed — but any species that are present are always perfectly mixed. As a result, a box model does not account for the impact of, say, wind on the distribution of species. “The point we’re trying to make is that you can go too simple,” says Chen. “If you’re going simpler than what we’re representing, you will get further from the right answer.” She goes on to note, “The utility of a relatively simple model like ours is that all of the knobs and levers are very clear. That means you can explore the system and see what affects a value of interest.”Leaked hydrogen versus leaked natural gas: A climate comparisonBurning natural gas produces fewer GHG emissions than does burning coal or oil; but as with hydrogen, any natural gas that’s leaked from wells, pipelines, and processing facilities can have climate impacts, negating some of the perceived benefits of using natural gas in place of other fossil fuels. After all, natural gas consists largely of methane, the highly potent GHG in the atmosphere that’s cleaned up by the OH detergent. Given its potency, even small leaks of methane can have a large climate impact.So when thinking about replacing natural gas fuel — essentially methane — with hydrogen fuel, it’s important to consider how the climate impacts of the two fuels compare if and when they’re leaked. The usual way to compare the climate impacts of two chemicals is using a measure called the global warming potential, or GWP. The GWP combines two measures: the radiative forcing of a gas — that is, its heat-trapping ability — with its lifetime in the atmosphere. Since the lifetimes of gases differ widely, to compare the climate impacts of two gases, the convention is to relate the GWP of each one to the GWP of carbon dioxide. But hydrogen and methane leakage cause increases in methane, and that methane decays according to its lifetime. Chen and her colleagues therefore realized that an unconventional procedure would work: they could compare the impacts of the two leaked gases directly. What they found was that the climate impact of hydrogen is about three times less than that of methane (on a per mass basis). So switching from natural gas to hydrogen would not only eliminate combustion emissions, but also potentially reduce the climate effects, depending on how much leaks.Key takeawaysIn summary, Chen highlights some of what she views as the key findings of the study. First on her list is the following: “We show that a really simple four-equation system is not what should be used to project out the atmospheric response to more hydrogen leakages in the future.” The researchers believe that their 66-equation model is a good compromise for the number of chemical reactions to include. It generates estimates for the GWP of methane “pretty much in line with the lower end of the numbers that most other groups are getting using much more sophisticated climate chemistry models,” says Chen. And it’s sufficiently transparent to use in exploring various options for protecting the climate. Indeed, the MIT researchers plan to use their model to examine scenarios that involve replacing other fossil fuels with hydrogen to estimate the climate benefits of making the switch in coming decades.The study also demonstrates a valuable new way to compare the greenhouse effects of two gases. As long as their effects exist on similar time scales, a direct comparison is possible — and preferable to comparing each with carbon dioxide, which is extremely long-lived in the atmosphere. In this work, the direct comparison generates a simple look at the relative climate impacts of leaked hydrogen and leaked methane — valuable information to take into account when considering switching from natural gas to hydrogen.Finally, the researchers offer practical guidance for infrastructure development and use for both hydrogen and natural gas. Their analyses determine that hydrogen fuel itself has a “non-negligible” GWP, as does natural gas, which is mostly methane. Therefore, minimizing leakage of both fuels will be necessary to achieve net-zero carbon emissions by 2050, the goal set by both the European Commission and the U.S. Department of State. Their paper concludes, “If used nearly leak-free, hydrogen is an excellent option. Otherwise, hydrogen should only be a temporary step in the energy transition, or it must be used in tandem with carbon-removal steps [elsewhere] to counter its warming effects.” More

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      in Environment

      In a unique research collaboration, students make the case for less e-waste

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      Brought together as part of the Social and Ethical Responsibilities of Computing (SERC) initiative within the MIT Schwarzman College of Computing, a community of students known as SERC Scholars is collaborating to examine the most urgent problems humans face in the digital landscape.Each semester, students from all levels from across MIT are invited to join a different topical working group led by a SERC postdoctoral associate. Each group delves into a specific issue — such as surveillance or data ownership — culminating in a final project presented at the end of the term.Typically, students complete the program with hands-on experience conducting research in a new cross-disciplinary field. However, one group of undergraduate and graduate students recently had the unique opportunity to enhance their resume by becoming published authors of a case study about the environmental and climate justice implications of the electronics hardware life cycle.Although it’s not uncommon for graduate students to co-author case studies, it’s unusual for undergraduates to earn this opportunity — and for their audience to be other undergraduates around the world.“Our team was insanely interdisciplinary,” says Anastasia Dunca, a junior studying computer science and one of the co-authors. “I joined the SERC Scholars Program because I liked the idea of being part of a cohort from across MIT working on a project that utilized all of our skillsets. It also helps [undergraduates] learn the ins and outs of computing ethics research.”Case study co-author Jasmin Liu, an MBA student in the MIT Sloan School of Management, sees the program as a platform to learn about the intersection of technology, society, and ethics: “I met team members spanning computer science, urban planning, to art/culture/technology. I was excited to work with a diverse team because I know complex problems must be approached with many different perspectives. Combining my background in humanities and business with the expertise of others allowed us to be more innovative and comprehensive.”Christopher Rabe, a former SERC postdoc who facilitated the group, says, “I let the students take the lead on identifying the topic and conducting the research.” His goal for the group was to challenge students across disciplines to develop a working definition of climate justice.From mining to e-wasteThe SERC Scholars’ case study, “From Mining to E-waste: The Environmental and Climate Justice Implications of the Electronics Hardware Life Cycle,” was published by the MIT Case Studies in Social and Ethical Responsibilities of Computing.The ongoing case studies series, which releases new issues twice a year on an open-source platform, is enabling undergraduate instructors worldwide to incorporate research-based education materials on computing ethics into their existing class syllabi.This particular case study broke down the electronics life cycle from mining to manufacturing, usage, and disposal. It offered an in-depth look at how this cycle promotes inequity in the Global South. Mining for the average of 60 minerals that power everyday devices lead to illegal deforestation, compromising air quality in the Amazon, and triggering armed conflict in Congo. Manufacturing leads to proven health risks for both formal and informal workers, some of whom are child laborers.Life cycle assessment and circular economy are proposed as mechanisms for analyzing environmental and climate justice issues in the electronics life cycle. Rather than posing solutions, the case study offers readers entry points for further discussion and for assessing their own individual responsibility as producers of e-waste.Crufting and crafting a case studyDunca joined Rabe’s working group, intrigued by the invitation to conduct a rigorous literature review examining issues like data center resource and energy use, manufacturing waste, ethical issues with AI, and climate change. Rabe quickly realized that a common thread among all participants was an interest in understanding and reducing e-waste and its impact on the environment.“I came in with the idea of us co-authoring a case study,” Rabe said. However, the writing-intensive process was initially daunting to those students who were used to conducting applied research. Once Rabe created sub-groups with discrete tasks, the steps for researching, writing, and iterating a case study became more approachable.For Ellie Bultena, an undergraduate student studying linguistics and philosophy and a contributor to the study, that meant conducting field research on the loading dock of MIT’s Stata Center, where students and faculty go “crufting” through piles of clunky printers, broken computers, and used lab equipment discarded by the Institute’s labs, departments, and individual users.Although not a formally sanctioned activity on-campus, “crufting” is the act of gleaning usable parts from these junk piles to be repurposed into new equipment or art. Bultena’s respondents, who opted to be anonymous, said that MIT could do better when it comes to the amount of e-waste generated and suggested that formal strategies could be implemented to encourage community members to repair equipment more easily or recycle more formally.Rabe, now an education program director at the MIT Environmental Solutions Initiative, is hopeful that through the Zero-Carbon Campus Initiative, which commits MIT to eliminating all direct emissions by 2050, MIT will ultimately become a model for other higher education institutions.Although the group lacked the time and resources to travel to communities in the Global South that they profiled in their case study, members leaned into exhaustive secondary research, collecting data on how some countries are irresponsibly dumping e-waste. In contrast, others have developed alternative solutions that can be duplicated elsewhere and scaled.“We source materials, manufacture them, and then throw them away,” Lelia Hampton says. A PhD candidate in electrical engineering and computer science and another co-author, Hampton jumped at the opportunity to serve in a writing role, bringing together the sub-groups research findings. “I’d never written a case study, and it was exciting. Now I want to write 10 more.”The content directly informed Hampton’s dissertation research, which “looks at applying machine learning to climate justice issues such as urban heat islands.” She said that writing a case study that is accessible to general audiences upskilled her for the non-profit organization she’s determined to start. “It’s going to provide communities with free resources and data needed to understand how they are impacted by climate change and begin to advocate against injustice,” Hampton explains.Dunca, Liu, Rabe, Bultena, and Hampton are joined on the case study by fellow authors Mrinalini Singha, a graduate student in the Art, Culture, and Technology program; Sungmoon Lim, a graduate student in urban studies and planning and EECS; Lauren Higgins, an undergraduate majoring in political science; and Madeline Schlegal, a Northeastern University co-op student.Taking the case study to classrooms around the worldAlthough PhD candidates have contributed to previous case studies in the series, this publication is the first to be co-authored with MIT undergraduates. Like any other peer-reviewed journal, before publication, the SERC Scholars’ case study was anonymously reviewed by senior scholars drawn from various fields.The series editor, David Kaiser, also served as one of SERC’s inaugural associate deans and helped shape the program. “The case studies, by design, are short, easy to read, and don’t take up lots of time,” Kaiser explained. “They are gateways for students to explore, and instructors can cover a topic that has likely already been on their mind.” This semester, Kaiser, the Germeshausen Professor of the History of Science and a professor of physics, is teaching STS.004 (Intersections: Science, Technology, and the World), an undergraduate introduction to the field of science, technology, and society. The last month of the semester has been dedicated wholly to SERC case studies, one of which is: “From Mining to E-Waste.”Hampton was visibly moved to hear that the case study is being used at MIT but also by some of the 250,000 visitors to the SERC platform, many of whom are based in the Global South and directly impacted by the issues she and her cohort researched. “Many students are focused on climate, whether through computer science, data science, or mechanical engineering. I hope that this case study educates them on environmental and climate aspects of e-waste and computing.” More