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      in Environment

      Even as temperatures rise, this hydrogel material keeps absorbing moisture

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      The vast majority of absorbent materials will lose their ability to retain water as temperatures rise. This is why our skin starts to sweat and why plants dry out in the heat. Even materials that are designed to soak up moisture, such as the silica gel packs in consumer packaging, will lose their sponge-like properties as their environment heats up.

      But one material appears to uniquely resist heat’s drying effects. MIT engineers have now found that polyethylene glycol (PEG) — a hydrogel commonly used in cosmetic creams, industrial coatings, and pharmaceutical capsules — can absorb moisture from the atmosphere even as temperatures climb.

      The material doubles its water absorption as temperatures climb from 25 to 50 degrees Celsius (77 to 122 degrees Fahrenheit), the team reports.

      PEG’s resilience stems from a heat-triggering transformation. As its surroundings heat up, the hydrogel’s microstructure morphs from a crystal to a less organized “amorphous” phase, which enhances the material’s ability to capture water.

      Based on PEG’s unique properties, the team developed a model that can be used to engineer other heat-resistant, water-absorbing materials. The group envisions such materials could one day be made into devices that harvest moisture from the air for drinking water, particularly in arid desert regions. The materials could also be incorporated into heat pumps and air conditioners to more efficiently regulate temperature and humidity.

      “A huge amount of energy consumption in buildings is used for thermal regulation,” says Lenan Zhang, a research scientist in MIT’s Department of Mechanical Engineering. “This material could be a key component of passive climate-control systems.”

      Zhang and his colleagues detail their work in a study appearing today in Advanced Materials. MIT co-authors include Xinyue Liu, Bachir El Fil, Carlos Diaz-Marin, Yang Zhong, Xiangyu Li, and Evelyn Wang, along with Shaoting Lin of Michigan State University.

      Against intuition

      Evelyn Wang’s group in MIT’s Device Research Lab aims to address energy and water challenges through the design of new materials and devices that sustainably manage water and heat. The team discovered PEG’s unusual properties as they were assessing a slew of similar hydrogels for their water-harvesting abilities.

      “We were looking for a high-performance material that could capture water for different applications,” Zhang says. “Hydrogels are a perfect candidate, because they are mostly made of water and a polymer network. They can simultaneously expand as they absorb water, making them ideal for regulating humidity and water vapor.”

      The team analyzed a variety of hydrogels, including PEG, by placing each material on a scale that was set within a climate-controlled chamber. A material became heavier as it absorbed more moisture. By recording a material’s changing weight, the researchers could track its ability to absorb moisture as they tuned the chamber’s temperature and humidity.

      What they observed was typical of most materials: as the temperature increased, the hyrogels’ ability to capture moisture from the air decreased. The reason for this temperature-dependence is well-understood: With heat comes motion, and at higher temperatures, water molecules move faster and are therefore more difficult to contain in most materials.

      “Our intuition tells us that at higher temperatures, materials tend to lose their ability to capture water,” says co-author Xinyue Liu. “So, we were very surprised by PEG because it has this inverse relationship.”

      In fact, they found that PEG grew heavier and continued to absorb water as the researchers raised the chamber’s temperature from 25 to 50 degrees Celsius.

      “At first, we thought we had measured some errors, and thought this could not be possible,” Liu says. “After we double-checked everything was correct in the experiment, we realized this was really happening, and this is the only known material that shows increasing water absorbing ability with higher temperature.”

      A lucky catch

      The group zeroed in on PEG to try and identify the reason for its unusual, heat-resilient performance. They found that the material has a natural melting point at around 50 degrees Celsius, meaning that the hydrogel’s normally crystal-like microstructure completely breaks down and transforms into an amorphous phase. Zhang says that this melted, amorphous phase provides more opportunity for polymers in the material to grab hold of any fast-moving water molecules.

      “In the crystal phase, there might be only a few sites on a polymer available to attract water and bind,” Zhang says. “But in the amorphous phase, you might have many more sites available. So, the overall performance can increase with increased temperature.”

      The team then developed a theory to predict how hydrogels absorb water, and showed that the theory could also explain PEG’s unusual behavior if the researchers added a “missing term” to the theory. That missing term was the effect of phase transformation. They found that when they included this effect, the theory could predict PEG’s behavior, along with that of other temperature-limiting hydrogels.

      The discovery of PEG’s unique properties was in large part by chance. The material’s melting temperature just happens to be within the range where water is a liquid, enabling them to catch PEG’s phase transformation and its resulting super-soaking behavior. The other hydrogels happen to have melting temperatures that fall outside this range. But the researchers suspect that these materials are also capable of similar phase transformations once they hit their melting temperatures.

      “Other polymers could in theory exhibit this same behavior, if we can engineer their melting points within a selected temperature range,” says team member Shaoting Lin.

      Now that the group has worked out a theory, they plan to use it as a blueprint to design materials specifically for capturing water at higher temperatures.

      “We want to customize our design to make sure a material can absorb a relatively high amount of water, at low humidity and high temperatures,” Liu says. “Then it could be used for atmospheric water harvesting, to bring people potable water in hot, arid environments.”

      This research was supported, in part, by U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy. More

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      in Energy

      MIT Energy Conference grapples with geopolitics

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      As Russia’s war in Ukraine rages on, this year’s MIT Energy Conference spotlighted the role of geopolitics in the world’s efforts to lower greenhouse gas emissions and mitigate the worst effects of climate change.

      Each year, the student-run conference, which its organizers say is the largest of its kind, brings together leaders from around the globe to discuss humanity’s most pressing energy and sustainability challenges.

      The event always involves perspectives from the investment, business, research, and startup communities. But this year, as more than 600 attendees gathered on April 11 and 12 for a whirlwind of keynote talks, fireside chats, and panel discussions, common themes also included the influence of Russia’s war, rising tensions between the U.S. and China, and international collaboration.

      As participants grappled with the evolving geopolitical landscape, some speakers encouraged moving past isolationist tendencies.

      “Some people push for self-sufficiency, others emphasize that we should not rely on trading partners that don’t share our values — I think both arguments are misguided,” said Juan Carlos Jobet, Chile’s former ministry of energy and mining. “No country has all that’s needed to create an energy system that’s affordable, clean, and secure. … A third of the world’s energy output is generated in nondemocratic countries. Can we really make our energy systems affordable and secure and curb climate change while excluding those countries from our collective effort? If we enter an area of protectionism and disintegration, we will all be worse off.”

      Another theme was optimism, such as that expressed by Volodymyr Kudrytskyi, CEO of Ukraine’s national power company, who spoke to the conference live from Kyiv. Kudrytskyi outlined Russia’s attacks on Ukraine’s power grids, which included more than 1,000 heavy missiles, making it the largest-ever campaign against a country’s power grid.

      Still, Kudrytskyi said he was confident he’d be able to attend the conference in person next year. As it happened, Kudrytskyi’s presentation marked the day Ukraine resumed its energy exports to other countries.

      “The good news is, after all of that, our system survived and continues operations,” he said.

      Energy security and the green transition

      Richard Duke, the U.S. Department of State’s deputy special envoy for climate, opened the conference with a keynote centered on the U.S.’ role in the global shift toward cleaner energy. Duke was among those advocating for a more integrated and diversified global energy system, noting that no country can address climate change on its own.

      “We need to do all of these things in parallel, in concert with other governments, and through the architecture of the Paris Climate agreement that wraps it together in ambitious net greenhouse gas abatement targets,” Duke said.

      Following his talk, Ditte Juul Jørgensen, the European Commission’s director general for energy, discussed the shift in the EU’s energy policies spurred by the Russian invasion of Ukraine.

      She admitted the EU had grown too dependent on Russian natural gas, but said the invasion forced European states to revise their energy strategy while keeping their long-term objective of net neutrality by 2050.

      “We see energy security and the green transition as interlinked. There is no energy security without the energy transition toward climate neutrality, and there’s no energy transition without energy security,” Jorgensen said.

      Jørgensen also outlined steps the EU has taken to improve its energy security over the last year, including rolling out additional renewable energy projects and replacing Russian fuel with fuel from the U.S., which has now become the continent’s main supplier of energy.

      “The fight against climate change is our shared ambition, it’s our shared responsibility, and I think we’ve shown over these last few years that we can turn that ambition into action and bring results,” she said.

      A challenge and an opportunity

      Optimism also shone through in the way speakers framed the green energy transition as a business opportunity. In keeping with the idea, the conference included a showcase of more than 30 startups focused on clean energy and sustainability.

      “We’re all battling a huge problem that needs a collective effort,” said Malav Sukhadia of Sol Clarity, a conference exhibitor that uses electricity to clean solar panels as a way to replace water cleaning. “This is one of the best energy conferences in the world. We felt if you’re in climate tech, you have to be here.”

      Technological development was a pillar of the conference, and a big topic in those discussions was green hydrogen, a clean fuel source that could replace natural gas in a number of applications and be produced using renewable energy. In one panel discussion on the technology, Sunita Satyapal of the Department of Energy noted the agency has been funding hydrogen development since the 1970s. Other panel members also stressed the maturity of the technology.

      “A lot of the technology needed to advance the ecosystem exists now,” said Laura Parkan, vice president of hydrogen energy at Air Liquide Americas. “The challenge is to get things to a large enough scale so that the costs come down to make it more affordable and really advance the hydrogen ecosystem.”

      Still, panel members acknowledged more technological development is needed to leverage the full potential of hydrogen, such as better mechanisms for storage and transportation.

      Other advanced technologies mentioned in panel discussions included advanced geothermal energy and small modular nuclear reactors that could be built and deployed more quickly than conventional reactors.

      “Exploring these different technologies may actually get us to the net zero — or even a zero carbon future — that we’re hoping for in electricity generation,” said Emma Wong of the OECD Nuclear Energy Agency, noting there are more than 80 advanced reactor designs that have been explored around the world. “There are various challenges and enabling conditions to be addressed, but places like China and Russia are already building these things, so there’s not a technological barrier.”

      “Glass half full”

      Despite the tall tasks that lie ahead, some speakers took a moment to celebrate accomplishments thus far.

      “It’s incredible to think about the progress we’ve made in the last 10 years,” said Neil Brown of the KKR investment firm, whose company is working to build a large offshore wind project. “Solar and wind and electric vehicles have gone from impossibly expensive and hard to imagine penetrating the market to being very close to, if not already at, cost parity. We’ve really come an awful long way.”

      Other speakers mixed their positivity with a confession of envy for the opportunity ahead of the young people in the audience, many of them students from MIT.

      “I have a mix of excitement from the speakers we’ve heard so far and a little bit of envy as well for the open road the young students and professionals here have in front of them,” said Jobert. “Coming back to this place has made me reconnect with the sense of opportunity and responsibility that I felt as a student.”

      Jobert offered lessons learned from his country’s struggles with an energy crisis, populist policies, and severe droughts. His talk finished with questions that struck at the heart of the conference.

      “The evidence is clear: The Earth will change. How much is still to be decided,” Jobert said. “The energy sector has been a central part of the problem. We now must work to become an essential pierce of the solution. Where should we focus our efforts? What can we learn from each other?” More

    • 188 Shares159 Views

      in Environment

      MIT PhD students honored for their work to solve critical issues in water and food

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      In 2017, the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) initiated the J-WAFS Fellowship Program for outstanding MIT PhD students working to solve humankind’s water-related challenges. Since then, J-WAFS has awarded 18 fellowships to students who have gone on to create innovations like a pump that can maximize energy efficiency even with changing flow rates, and a low-cost water filter made out of sapwood xylem that has seen real-world use in rural India. Last year, J-WAFS expanded eligibility to students with food-related research. The 2022 fellows included students working on micronutrient deficiency and plastic waste from traditional food packaging materials. 

      Today, J-WAFS has announced the award of the 2023-24 fellowships to Gokul Sampath and Jie Yun. A doctoral student in the Department of Urban Studies and planning, Sampath has been awarded the Rasikbhai L. Meswani Fellowship for Water Solutions, which is supported through a generous gift from Elina and Nikhil Meswani and family. Yun, who is in the Department of Civil and Environmental Engineering, received a J-WAFS Fellowship for Water and Food Solutions, which is funded by the J-WAFS Research Affiliate Program. Currently, Xylem, Inc. and GoAigua are J-WAFS’ Research Affiliate companies. A review committee comprised of MIT faculty and staff selected Sampath and Yun from a competitive field of outstanding graduate students working in water and food who were nominated by their faculty advisors. Sampath and Yun will receive one academic semester of funding, along with opportunities for networking and mentoring to advance their research.

      “Both Yun and Sampath have demonstrated excellence in their research,” says J-WAFS executive director Renee J. Robins. “They also stood out in their communication skills and their passion to work on issues of agricultural sustainability and resilience and access to safe water. We are so pleased to have them join our inspiring group of J-WAFS fellows,” she adds.

      Using behavioral health strategies to address the arsenic crisis in India and Bangladesh

      Gokul Sampath’s research centers on ways to improve access to safe drinking water in developing countries. A PhD candidate in the International Development Group in the Department of Urban Studies and Planning, his current work examines the issue of arsenic in drinking water sources in India and Bangladesh. In Eastern India, millions of shallow tube wells provide rural households a personal water source that is convenient, free, and mostly safe from cholera. Unfortunately, it is now known that one-in-four of these wells is contaminated with naturally occurring arsenic at levels dangerous to human health. As a result, approximately 40 million people across the region are at elevated risk of cancer, stroke, and heart disease from arsenic consumed through drinking water and cooked food. 

      Since the discovery of arsenic in wells in the late 1980s, governments and nongovernmental organizations have sought to address the problem in rural villages by providing safe community water sources. Yet despite access to safe alternatives, many households still consume water from their contaminated home wells. Sampath’s research seeks to understand the constraints and trade-offs that account for why many villagers don’t collect water from arsenic-safe government wells in the village, even when they know their own wells at home could be contaminated.

      Before coming to MIT, Sampath received a master’s degree in Middle East, South Asian, and African studies from Columbia University, as well as a bachelor’s degree in microbiology and history from the University of California at Davis. He has long worked on water management in India, beginning in 2015 as a Fulbright scholar studying households’ water source choices in arsenic-affected areas of the state of West Bengal. He also served as a senior research associate with the Abdul Latif Jameel Poverty Action Lab, where he conducted randomized evaluations of market incentives for groundwater conservation in Gujarat, India. Sampath’s advisor, Bishwapriya Sanyal, the Ford International Professor of Urban Development and Planning at MIT, says Sampath has shown “remarkable hard work and dedication.” In addition to his classes and research, Sampath taught the department’s undergraduate Introduction to International Development course, for which he received standout evaluations from students.

      This summer, Sampath will travel to India to conduct field work in four arsenic-affected villages in West Bengal to understand how social influence shapes villagers’ choices between arsenic-safe and unsafe water sources. Through longitudinal surveys, he hopes to connect data on the social ties between families in villages and the daily water source choices they make. Exclusionary practices in Indian village communities, especially the segregation of water sources on the basis of caste and religion, has long been suspected to be a barrier to equitable drinking water access in Indian villages. Yet despite this, planners seeking to expand safe water access in diverse Indian villages have rarely considered the way social divisions within communities might be working against their efforts. Sampath hopes to test whether the injunctive norms enabled by caste ties constrain villagers’ ability to choose the safest water source among those shared within the village. When he returns to MIT in the fall, he plans to dive into analyzing his survey data and start work on a publication.

      Understanding plant responses to stress to improve crop drought resistance and yield

      Plants, including crops, play a fundamental role in Earth’s ecosystems through their effects on climate, air quality, and water availability. At the same time, plants grown for agriculture put a burden on the environment as they require energy, irrigation, and chemical inputs. Understanding plant/environment interactions is becoming more and more important as intensifying drought is straining agricultural systems. Jie Yun, a PhD student in the Department of Civil and Environmental Engineering, is studying plant response to drought stress in the hopes of improving agricultural sustainability and yield under climate change.  Yun’s research focuses on genotype-by-environment interaction (GxE.) This relates to the observation that plant varieties respond to environmental changes differently. The effects of GxE in crop breeding can be exploited because differing environmental responses among varieties enables breeders to select for plants that demonstrate high stress-tolerant genotypes under particular growing conditions. Yun bases her studies on Brachypodium, a model grass species related to wheat, oat, barley, rye, and perennial forage grasses. By experimenting with this species, findings can be directly applied to cereal and forage crop improvement. For the first part of her thesis, Yun collaborated with Professor Caroline Uhler’s group in the Department of Electrical Engineering and Computer Science and the Institute for Data, Systems, and Society. Uhler’s computational tools helped Yun to evaluate gene regulatory networks and how they relate to plant resilience and environmental adaptation. This work will help identify the types of genes and pathways that drive differences in drought stress response among plant varieties.  David Des Marais, the Cecil and Ida Green Career Development Professor in the Department of Civil and Environmental Engineering, is Yun’s advisor. He notes, “throughout Jie’s time [at MIT] I have been struck by her intellectual curiosity, verging on fearlessness.” When she’s not mentoring undergraduate students in Des Marais’ lab, Yun is working on the second part of her project: how carbon allocation in plants and growth is affected by soil drying. One result of this work will be to understand which populations of plants harbor the necessary genetic diversity to adapt or acclimate to climate change. Another likely impact is identifying targets for the genetic improvement of crop species to increase crop yields with less water supply. Growing up in China, Yun witnessed environmental issues springing from the development of the steel industry, which caused contamination of rivers in her hometown. On one visit to her aunt’s house in rural China, she learned that water pollution was widespread after noticing wastewater was piped outside of the house into nearby farmland without being treated. These experiences led Yun to study water supply and sewage engineering for her undergraduate degree at Shenyang Jianzhu University. She then went on to complete a master’s program in civil and environmental engineering at Carnegie Mellon University. It was there that Yun discovered a passion for plant-environment interactions; during an independent study on perfluorooctanoic sulfonate, she realized the amazing ability of plants to adapt to environmental changes, toxins, and stresses. Her goal is to continue researching plant and environment interactions and to translate the latest scientific findings into applications that can improve food security. More

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      in Energy

      MIT engineers devise technology to prevent fouling in photobioreactors for CO2 capture

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      Algae grown in transparent tanks or tubes supplied with carbon dioxide can convert the greenhouse gas into other compounds, such as food supplements or fuels. But the process leads to a buildup of algae on the surfaces that clouds them and reduces efficiency, requiring laborious cleanout procedures every couple of weeks.

      MIT researchers have come up with a simple and inexpensive technology that could substantially limit this fouling, potentially allowing for a much more efficient and economical way of converting the unwanted greenhouse gas into useful products.

      The key is to coat the transparent containers with a material that can hold an electrostatic charge, and then applying a very small voltage to that layer. The system has worked well in lab-scale tests, and with further development might be applied to commercial production within a few years.

      The findings are being reported in the journal Advanced Functional Materials, in a paper by recent MIT graduate Victor Leon PhD ’23, professor of mechanical engineering Kripa Varanasi, former postdoc Baptiste Blanc, and undergraduate student Sophia Sonnert.

      No matter how successful efforts to reduce or eliminate carbon emissions may be, there will still be excess greenhouse gases that will remain in the atmosphere for centuries to come, continuing to affect global climate, Varanasi points out. “There’s already a lot of carbon dioxide there, so we have to look at negative emissions technologies as well,” he says, referring to ways of removing the greenhouse gas from the air or oceans, or from their sources before they get released into the air in the first place.

      When people think of biological approaches to carbon dioxide reduction, the first thought is usually of planting or protecting trees, which are indeed a crucial “sink” for atmospheric carbon. But there are others. “Marine algae account for about 50 percent of global carbon dioxide absorbed today on Earth,” Varanasi says. These algae grow anywhere from 10 to 50 times more quickly than land-based plants, and they can be grown in ponds or tanks that take up only a tenth of the land footprint of terrestrial plants.

      What’s more, the algae themselves can then be a useful product. “These algae are rich in proteins, vitamins and other nutrients,” Varanasi says, noting they could produce far more nutritional output per unit of land used than some traditional agricultural crops.

      If attached to the flue gas output of a coal or gas power plant, algae could not only thrive on the carbon dioxide as a nutrient source, but some of the microalgae species could also consume the associated nitrogen and sulfur oxides present in these emissions. “For every two or three kilograms of CO2, a kilogram of algae could be produced, and these could be used as biofuels, or for Omega-3, or food,” Varanasi says.

      Omega-3 fatty acids are a widely used food supplement, as they are an essential part of cell membranes and other tissues but cannot be made by the body and must be obtained from food. “Omega 3 is particularly attractive because it’s also a much higher-value product,” Varanasi says.

      Most algae grown commercially are cultivated in shallow ponds, while others are grown in transparent tubes called photobioreactors. The tubes can produce seven to 10 times greater yields than ponds for a given amount of land, but they face a major problem: The algae tend to build up on the transparent surfaces, requiring frequent shutdowns of the whole production system for cleaning, which can take as long as the productive part of the cycle, thus cutting overall output in half and adding to operational costs.

      The fouling also limits the design of the system. The tubes can’t be too small because the fouling would begin to block the flow of water through the bioreactor and require higher pumping rates.

      Varanasi and his team decided to try to use a natural characteristic of the algae cells to defend against fouling. Because the cells naturally carry a small negative electric charge on their membrane surface, the team figured that electrostatic repulsion could be used to push them away.

      The idea was to create a negative charge on the vessel walls, such that the electric field forces the algae cells away from the walls. To create such an electric field requires a high-performance dielectric material, which is an electrical insulator with a high “permittivity” that can produce a large change in surface charge with a smaller voltage.

      “What people have done before with applying voltage [to bioreactors] has been with conductive surfaces,” Leon explains, “but what we’re doing here is specifically with nonconductive surfaces.”

      He adds: “If it’s conductive, then you pass current and you’re kind of shocking the cells. What we’re trying to do is pure electrostatic repulsion, so the surface would be negative and the cell is negative so you get repulsion. Another way to describe it is like a force field, whereas before the cells were touching the surface and getting shocked.”

      The team worked with two different dielectric materials, silicon dioxide — essentially glass — and hafnia (hafnium oxide), both of which turned out to be far more efficient at minimizing fouling than conventional plastics used to make photobioreactors. The material can be applied in a coating that is vanishingly thin, just 10 to 20 nanometers (billionths of a meter) thick, so very little would be needed to coat a full photobioreactor system.

      “What we are excited about here is that we are able to show that purely from electrostatic interactions, we are able to control cell adhesion,” Varanasi says. “It’s almost like an on-off switch, to be able to do this.”

      Additionally, Leon says, “Since we’re using this electrostatic force, we don’t really expect it to be cell-specific, and we think there’s potential for applying it with other cells than just algae. In future work, we’d like to try using it with mammalian cells, bacteria, yeast, and so on.” It could also be used with other valuable types of algae, such as spirulina, that are widely used as food supplements.

      The same system could be used to either repel or attract cells by just reversing the voltage, depending on the particular application. Instead of algae, a similar setup might be used with human cells to produce artificial organs by producing a scaffold that could be charged to attract the cells into the right configuration, Varanasi suggests.

      “Our study basically solves this major problem of biofouling, which has been a bottleneck for photobioreactors,” he says. “With this technology, we can now really achieve the full potential” of such systems, although further development will be needed to scale up to practical, commercial systems.

      As for how soon this could be ready for widespread deployment, he says, “I don’t see why not in three years’ timeframe, if we get the right resources to be able to take this work forward.”

      The study was supported by energy company Eni S.p.A., through the MIT Energy Initiative. More

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      in Energy

      An interdisciplinary approach to fighting climate change through clean energy solutions

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      In early 2021, the U.S. government set an ambitious goal: to decarbonize its power grid, the system that generates and transmits electricity throughout the country, by 2035. It’s an important goal in the fight against climate change, and will require a switch from current, greenhouse-gas producing energy sources (such as coal and natural gas), to predominantly renewable ones (such as wind and solar).

      Getting the power grid to zero carbon will be a challenging undertaking, as Audun Botterud, a principal research scientist at the MIT Laboratory for Information and Decision Systems (LIDS) who has long been interested in the problem, knows well. It will require building lots of renewable energy generators and new infrastructure; designing better technology to capture, store, and carry electricity; creating the right regulatory and economic incentives; and more. Decarbonizing the grid also presents many computational challenges, which is where Botterud’s focus lies. Botterud has modeled different aspects of the grid — the mechanics of energy supply, demand, and storage, and electricity markets — where economic factors can have a huge effect on how quickly renewable solutions get adopted.

      On again, off again

      A major challenge of decarbonization is that the grid must be designed and operated to reliably meet demand. Using renewable energy sources complicates this, as wind and solar power depend on an infamously volatile system: the weather. A sunny day becomes gray and blustery, and wind turbines get a boost but solar farms go idle. This will make the grid’s energy supply variable and hard to predict. Additional resources, including batteries and backup power generators, will need to be incorporated to regulate supply. Extreme weather events, which are becoming more common with climate change, can further strain both supply and demand. Managing a renewables-driven grid will require algorithms that can minimize uncertainty in the face of constant, sometimes random fluctuations to make better predictions of supply and demand, guide how resources are added to the grid, and inform how those resources are committed and dispatched across the entire United States.

      “The problem of managing supply and demand in the grid has to happen every second throughout the year, and given how much we rely on electricity in society, we need to get this right,” Botterud says. “You cannot let the reliability drop as you increase the amount of renewables, especially because I think that will lead to resistance towards adopting renewables.”

      That is why Botterud feels fortunate to be working on the decarbonization problem at LIDS — even though a career here is not something he had originally planned. Botterud’s first experience with MIT came during his time as a graduate student in his home country of Norway, when he spent a year as a visiting student with what is now called the MIT Energy Initiative. He might never have returned, except that while at MIT, Botterud met his future wife, Bilge Yildiz. The pair both ended up working at the Argonne National Laboratory outside of Chicago, with Botterud focusing on challenges related to power systems and electricity markets. Then Yildiz got a faculty position at MIT, where she is a professor of nuclear and materials science and engineering. Botterud moved back to the Cambridge area with her and continued to work for Argonne remotely, but he also kept an eye on local opportunities. Eventually, a position at LIDS became available, and Botterud took it, while maintaining his connections to Argonne.

      “At first glance, it may not be an obvious fit,” Botterud says. “My work is very focused on a specific application, power system challenges, and LIDS tends to be more focused on fundamental methods to use across many different application areas. However, being at LIDS, my lab [the Energy Analytics Group] has access to the most recent advances in these fundamental methods, and we can apply them to power and energy problems. Other people at LIDS are working on energy too, so there is growing momentum to address these important problems.”

      Weather, space, and time

      Much of Botterud’s research involves optimization, using mathematical programming to compare alternatives and find the best solution. Common computational challenges include dealing with large geographical areas that contain regions with different weather, different types and quantities of renewable energy available, and different infrastructure and consumer needs — such as the entire United States. Another challenge is the need for granular time resolution, sometimes even down to the sub-second level, to account for changes in energy supply and demand.

      Often, Botterud’s group will use decomposition to solve such large problems piecemeal and then stitch together solutions. However, it’s also important to consider systems as a whole. For example, in a recent paper, Botterud’s lab looked at the effect of building new transmission lines as part of national decarbonization. They modeled solutions assuming coordination at the state, regional, or national level, and found that the more regions coordinate to build transmission infrastructure and distribute electricity, the less they will need to spend to reach zero carbon.

      In other projects, Botterud uses game theory approaches to study strategic interactions in electricity markets. For example, he has designed agent-based models to analyze electricity markets. These assume each actor will make strategic decisions in their own best interest and then simulate interactions between them. Interested parties can use the models to see what would happen under different conditions and market rules, which may lead companies to make different investment decisions, or governing bodies to issue different regulations and incentives. These choices can shape how quickly the grid gets decarbonized.

      Botterud is also collaborating with researchers in MIT’s chemical engineering department who are working on improving battery storage technologies. Batteries will help manage variable renewable energy supply by capturing surplus energy during periods of high generation to release during periods of insufficient generation. Botterud’s group models the sort of charge cycles that batteries are likely to experience in the power grid, so that chemical engineers in the lab can test their batteries’ abilities in more realistic scenarios. In turn, this also leads to a more realistic representation of batteries in power system optimization models.

      These are only some of the problems that Botterud works on. He enjoys the challenge of tackling a spectrum of different projects, collaborating with everyone from engineers to architects to economists. He also believes that such collaboration leads to better solutions. The problems created by climate change are myriad and complex, and solving them will require researchers to cooperate and explore.

      “In order to have a real impact on interdisciplinary problems like energy and climate,” Botterud says, “you need to get outside of your research sweet spot and broaden your approach.” More

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      in Environment

      Greening roofs to boost climate resilience

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      When the historic cities of Europe were built hundreds of years ago, there were open green spaces all around them. But today’s city centers can be a 30-minute drive or more to the vast open greenery that earlier Europeans took for granted.

      That’s what the startup Roofscapes is trying to change. The company, founded by three students from MIT’s master of architecture program, is using timber structures to turn the ubiquitous pitched roofs of Paris into accessible green spaces.

      The spaces would provide a way to grow local food, anchor biodiversity, reduce the temperatures of buildings, improve air quality, increase water retention, and give residents a new way to escape the dense urban clusters of modern times.

      “We see this as a way to unlock the possibilities of these buildings,” says Eytan Levi MA ’21, SM ’21, who co-founded the company with Olivier Faber MA ’23 and Tim Cousin MA ’23. “These surfaces weren’t being used otherwise but could actually have a highly positive contribution to the value of the buildings, the environment, and the lives of the people.”

      For the co-founders, Roofscapes is about helping build up climate resilience for the future while improving quality of life in cities now.

      “It was always important to us to work with as little contradictions to our values as possible in terms of environmental and social impact,” Faber says. “For us, Roofscapes is a way to apply some of our academic learnings to the real world in a way that is tactical and impactful, because we’re tapping into this whole issue — pitched roof adaptation — that has been ignored by traditional architecture.”

      Three architects with a vision

      The founders, who grew up in France, met while studying architecture as undergraduates in Switzerland, but after graduating and working at design firms for a few years, they began discussing other ways they could make a difference.

      “We knew we wanted to have an impact on the built environment that was different than what a lot of architectural firms were doing. We were thinking about a startup, but mostly we came to MIT because we knew we’d have a lot of agency to grow our skills and competency in adapting the built environment to the climate and biodiversity crises,” Faber explains.

      Three months after coming to MIT, they applied to the DesignX accelerator to explore ways to make cities greener by using timber structures to build flat, green platforms on the ubiquitous pitched roofs of European cities’ older buildings.

      “In European city centers, two thirds of the roofs are pitched, and there’s no solution to make them accessible and put green surfaces on them,” Cousin says. “Meanwhile, we have all these issues with heat islands and excessive heat in urban centers, among other issues like biodiversity collapse, retention of rain water, lack of green spaces. Green roofs are one of the best ways to address all of these problems.”

      They began making small models of their imagined green roofs and talking with structural engineers around campus. The founders also gained operational knowledge from MIT’s Center for Real Estate, where Levi studied.

      In 2021, they showcased a 170-square-foot model at the Seoul Biennale of Architecture and Urbanism in South Korea. The model showed roofs made from different materials and pitched at different angles, along with versions of Roofscapes’ wooden platforms with gardens and vegetation built on top.

      When Levi graduated, he moved to Paris, where Cousin and Faber are joining him this spring. “We’re starting with Paris because all the roofs there are the same height, and you can really feel the potential when you go up there to help the city adapt,” says Cousin.

      Roofscapes’ big break came last year, when the company won a grant from the City of Paris as part of a program to improve the city’s climate resilience. The grant will go toward Roofscapes’ first project on the roof of a former town hall building in the heart of Paris. The company plans to test the project’s impact on the temperature of the buildings, humidity levels, and the biodiversity it can foster.

      “We were just three architects with a vision, and at MIT it became a company, and now in Paris we’re seeing the reality of deploying this vision,” Cousin says. “This is not something you do with three people. You need everyone in the city on the same side. We’re being advocates, and it’s exciting to be in this position.”

      A grassroots roof movement

      The founders say they hear at least once a week from a building owner or tenant who is excited to become a partner, giving them a list of more than 60 buildings to consider for their systems down the line. Still, they plan to focus on running tests on a few pilot projects in Paris before expanding more quickly using prefabricated structures.

      “It’s great to hear that constant interest,” Levi says. “It’s like we’re on the same team, because they’re potential clients, but they’re also cheering us on in our work. We know from the interest that once we have a streamlined process, we can get a lot of projects at once.”

      Even in just the three years since founding the company, the founders say they’ve seen their work take on a new sense of urgency.

      “We’ve seen a shift in people’s minds since we started three years ago,” Levi says. “Global warming is becoming increasingly graspable, and we’re seeing a greater will from building owners and inhabitants. People are very supportive of the notion that we have a heritage environment, but as the climate changes drastically, our building stock doesn’t work anymore the way it worked in the 19th century. It needs to be adapted, and that’s what we are doing.” More

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      in Environment

      3 Questions: Leveraging carbon uptake to lower concrete’s carbon footprint

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      To secure a more sustainable and resilient future, we must take a careful look at the life cycle impacts of humanity’s most-produced building material: concrete. Carbon uptake, the process by which cement-based products sequester carbon dioxide, is key to this understanding.

      Hessam AzariJafari, the MIT Concrete Sustainability Hub’s deputy director, is deeply invested in the study of this process and its acceleration, where prudent. Here, he describes how carbon uptake is a key lever to reach a carbon-neutral concrete industry.

      Q: What is carbon uptake in cement-based products and how can it influence their properties?

      A: Carbon uptake, or carbonation, is a natural process of permanently sequestering CO2 from the atmosphere by hardened cement-based products like concretes and mortars. Through this reaction, these products form different kinds of limes or calcium carbonates. This uptake occurs slowly but significantly during two phases of the life cycle of cement-based products: the use phase and the end-of-life phase.

      In general, carbon uptake increases the compressive strength of cement-based products as it can densify the paste. At the same time, carbon uptake can impact the corrosion resistance of concrete. In concrete that is reinforced with steel, the corrosion process can be initiated if the carbonation happens extensively (e.g., the whole of the concrete cover is carbonated) and intensively (e.g., a significant proportion of the hardened cement product is carbonated). [Concrete cover is the layer distance between the surface of reinforcement and the outer surface of the concrete.]

      Q: What are the factors that influence carbon uptake?

      A: The intensity of carbon uptake depends on four major factors: the climate, the types and properties of cement-based products used, the composition of binders (cement type) used, and the geometry and exposure condition of the structure.

      In regard to climate, the humidity and temperature affect the carbon uptake rate. In very low or very high humidity conditions, the carbon uptake process is slowed. High temperatures speed the process. The local atmosphere’s carbon dioxide concentration can affect the carbon uptake rate. For example, in urban areas, carbon uptake is an order of magnitude faster than in suburban areas.

      The types and properties of cement-based products have a large influence on the rate of carbon uptake. For example, mortar (consisting of water, cement, and fine aggregates) carbonates two to four times faster than concrete (consisting of water, cement, and coarse and fine aggregates) because of its more porous structure.The carbon uptake rate of dry-cast concrete masonry units is higher than wet-cast for the same reason. In structural concrete, the process is made slower as mechanical properties are improved and the density of the hardened products’ structure increases.

      Lastly, a structure’s surface area-to-volume ratio and exposure to air and water can have ramifications for its rate of carbonation. When cement-based products are covered, carbonation may be slowed or stopped. Concrete that is exposed to fresh air while being sheltered from rain can have a larger carbon uptake compared to cement-based products that are painted or carpeted. Additionally, cement-based elements with large surface areas, like thin concrete structures or mortar layers, allow uptake to progress more extensively.

      Q: What is the role of carbon uptake in the carbon neutrality of concrete, and how should architects and engineers account for it when designing for specific applications?

      A: Carbon uptake is a part of the life cycle of any cement-based products that should be accounted for in carbon footprint calculations. Our evaluation shows the U.S. pavement network can sequester 5.8 million metric tons of CO2, of which 52 percent will be sequestered when the demolished concrete is stockpiled at its end of life.

      From one concrete structure to another, the percentage of emissions sequestered may vary. For instance, concrete bridges tend to have a lower percentage versus buildings constructed with concrete masonry. In any case, carbon uptake can influence the life cycle environmental performance of concrete.

      At the MIT Concrete Sustainability Hub, we have developed a calculator to enable construction stakeholders to estimate the carbon uptake of concrete structures during their use and end-of-life phases.

      Looking toward the future, carbon uptake’s role in the carbon neutralization of cement-based products could grow in importance. While caution should be taken in regards to uptake when reinforcing steel is embedded in concrete, there are opportunities for different stakeholders to augment carbon uptake in different cement-based products.

      Architects can influence the shape of concrete elements to increase the surface area-to-volume ratio (e.g., making “waffle” patterns on slabs and walls, or having several thin towers instead of fewer large ones on an apartment complex). Concrete manufacturers can adjust the binder type and quantity while delivering concrete that meets performance requirements. Finally, industrial ecologists and life-cycle assessment practitioners need to work on the tools and add-ons to make sure the impact of carbon is well captured when assessing the potential impacts of cement-based products in buildings and infrastructure systems.

      Currently, the cement and concrete industry is working with tech companies as well as local, state, and federal governments to lower and subsidize the code of carbon capture sequestration and neutralization. Accelerating carbon uptake where reasonable could be an additional lever to neutralize the carbon emissions of the concrete value chain.

      Carbon uptake is one more piece of the puzzle that makes concrete a sustainable choice for building in many applications. The sustainability and resilience of the future built environment lean on the use of concrete. There is still much work to be done to truly build sustainably, and understanding carbon uptake is an important place to begin. More

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      in Environment

      Fieldwork class examines signs of climate change in Hawaii

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      When Joy Domingo-Kameenui spent two weeks in her native Hawaii as part of MIT class 1.091 (Traveling Research Environmental eXperiences), she was surprised to learn about the number of invasive and endangered species. “I knew about Hawaiian ecology from middle and high school but wasn’t fully aware to the extent of how invasive species and diseases have resulted in many of Hawaii’s endemic species becoming threatened,” says Domingo-Kameenui.  

      Domingo-Kameenui was part of a group of MIT students who conducted field research on the Big Island of Hawaii in the Traveling Research Environmental eXperiences (TREX) class offered by the Department of Civil and Environmental Engineering. The class provides undergraduates an opportunity to gain hands-on environmental fieldwork experience using Hawaii’s geology, chemistry, and biology to address two main topics of climate change concern: sulfur dioxide (SO2) emissions and forest health.

      “Hawaii is this great system for studying the effects of climate change,” says David Des Marais, the Cecil and Ida Green Career Development Professor of Civil and Environmental Engineering and lead instructor of TREX. “Historically, Hawaii has had occasional mild droughts that are related to El Niño, but the droughts are getting stronger and more frequent. And we know these types of extreme weather events are going to happen worldwide.”

      Climate change impacts on forests

      The frequency and intensity of extreme events are also becoming more of a problem for forests and plant life. Forests have a certain distribution of vegetation and as you get higher in elevation, the trees gradually turn into shrubs, and then rock. Trees don’t grow above the timberline, where the temperature and precipitation changes dramatically at the high elevations. “But unlike the Sierra Nevada or the Rockies, where the trees gradually change as you go up the mountains, in Hawaii, they gradually change, and then they just stop,” says Des Marais.

      “Why this is an interesting model for climate change,” explains Des Marais, “is that line where trees stop [growing] is going to move, and it’s going to become more unstable as the trade winds are affected by global patterns of air circulation, which are changing because of climate change.”

      The research question that Des Marais asks students to explore — How is the Hawaiian forest going to be affected by climate change? — uses Hawaii as a model for broader patterns in climate change for forests.

      To dive deeper into this question, students trekked up the mountain taking ground-level measurements of canopy cover with a camera app on their cellphones, estimating how much tree coverage blankets the sky when looking up, and observing how the canopy cover thins until they see no tree coverage at all as they go further up the mountain. Drones also flew above the forest to measure chlorophyll and how much plant matter remains. And then satellite data products from NASA and the European Space Agency were used to measure the distribution of chlorophyll, climate, and precipitation data from space.

      They also worked directly with community stakeholders at three locations around the island to access the forests and use technology to assess the ecology and biodiversity challenges. One of those stakeholders was the Kamehameha Schools Natural and Cultural Ecosystems Division, whose mission is to preserve the land and manage it in a sustainable way. Students worked with their plant biologists to help address and think about what management decisions will support the future health of their forests.

      “Across the island, rising temperatures and abnormal precipitation patterns are the main drivers of drought, which really has significant impacts on biodiversity, and overall human health,” says Ava Gillikin, a senior in civil and environmental engineering.

      Gillikin adds that “a good proportion of the island’s water system relies on rainwater catchment, exposing vulnerabilities to fluctuations in rain patterns that impact many people’s lives.”

      Deadly threats to native plants

      The other threats to Hawaii’s forests are invasive species causing ecological harm, from the prevalence of non-indigenous mosquitoes leading to increases in avian malaria and native bird death that threaten the native ecosystem, to a plant called strawberry guava.

      Strawberry guava is taking over Hawaii’s native ōhiʻa trees, which Domingo-Kameenui says is also contributing to Hawaii’s water production. “The plants absorb water quickly so there’s less water runoff for groundwater systems.”

      A fungal pathogen is also infecting native ōhiʻa trees. The disease, called rapid ʻohiʻa death (ROD), kills the tree within a few days to weeks. The pathogen was identified by researchers on the island in 2014 from the fungal genus, Ceratocystis. The fungal pathogen was likely carried into the forests by humans on their shoes, or contaminated tools, gear, and vehicles traveling from one location to another. The fungal disease is also transmitted by beetles that bore into trees and create a fine powder-like dust. This dust from an infected tree is then mixed with the fungal spores and can easily spread to other trees by wind, or contaminated soil.

      For Gillikin, seeing the effects of ROD in the field highlighted the impact improper care and preparation can have on native forests. “The ‘ohi’a tree is one of the most prominent native trees, and ROD can kill the trees very rapidly by putting a strain on its vascular system and preventing water from reaching all parts of the tree,” says Gillikin.

      Before entering the forests, students sprayed their shoes and gear with ethanol frequently to prevent the spread.

      Uncovering chemical and particle formation

      A second research project in TREX studied volcanic smog (vog) that plagues the air, making visibility problematic at times and causing a lot of health problems for people in Hawaii. The active Kilauea volcano releases SO2 into the atmosphere. When the SO2 mixes with other gasses emitted from the volcano and interacts with sunlight and the atmosphere, particulate matter forms.

      Students in the Kroll Group, led by Jesse Kroll, professor of civil and environmental engineering and chemical engineering, have been studying SO2 and particulate matter over the years, but not the chemistry directly in how those chemical transformations occur.

      “There’s a hypothesis that there is a functional connection between the SO2 and particular matter, but that’s never been directly demonstrated,” says Des Marais.

      Testing that hypothesis, the students were able to measure two different sizes of particulate matter formed from the SO2 and develop a model to show how much vog is generated downstream of the volcano.

      They spent five days at two sites from sunrise to late morning measuring particulate matter formation as the sun comes up and starts creating new particles. Using a combination of data sources for meteorology, such as UV index, wind speed, and humidity, the students built a model that demonstrates all the pieces of an equation that can calculate when new particles are formed.

      “You can build what you think that equation is based on first-principle understanding of the chemical composition, but what they did was measured it in real time with measurements of the chemical reagents,” says Des Marias.

      The students measured what was going to catalyze the chemical reaction of particulate matter — for instance, things like sunlight and ozone — and then calculated numbers to the outputs.

      “What they found, and what seems to be happening, is that the chemical reagents are accumulating overnight,” says Des Marais. “Then as soon as the sun rises in the morning all the transformation happens in the atmosphere. A lot of the reagents are used up and the wind blows everything away, leaving the other side of the island with polluted air,” adds Des Marais.

      “I found the vog particle formation fieldwork a surprising research learning,” adds Domingo-Kameenui who did some atmospheric chemistry research in the Kroll Group. “I just thought particle formation happened in the air, but we found wind direction and wind speed at a certain time of the day was extremely important to particle formation. It’s not just chemistry you need to look at, but meteorology and sunlight,” she adds.

      Both Domingo-Kameenui and Gillikin found the fieldwork class an important and memorable experience with new insight that they will carry with them beyond MIT.  

      How Gillikin approaches fieldwork or any type of community engagement in another culture is what she will remember most. “When entering another country or culture, you are getting the privilege to be on their land, to learn about their history and experiences, and to connect with so many brilliant people,” says Gillikin. “Everyone we met in Hawaii had so much passion for their work, and approaching those environments with respect and openness to learn is what I experienced firsthand and will take with me throughout my career.” More