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      in Environment

      A vision for U.S. science success

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      White House science advisor Arati Prabhakar expressed confidence in U.S. science and technology capacities during a talk on Wednesday about major issues the country must tackle.“Let me start with the purpose of science and technology and innovation, which is to open possibilities so that we can achieve our great aspirations,” said Prabhakar, who is the director of the Office of Science and Technology Policy (OSTP) and a co-chair of the President’s Council of Advisors on Science and Technology (PCAST). “The aspirations that we have as a country today are as great as they have ever been,” she added.Much of Prabhakar’s talk focused on three major issues in science and technology development: cancer prevention, climate change, and AI. In the process, she also emphasized the necessity for the U.S. to sustain its global leadership in research across domains of science and technology, which she called “one of America’s long-time strengths.”“Ever since the end of the Second World War, we said we’re going in on basic research, we’re going to build our universities’ capacity to do it, we have an unparalleled basic research capacity, and we should always have that,” said Prabhakar.“We have gotten better, I think, in recent years at commercializing technology from our basic research,” Prabhakar added, noting, “Capital moves when you can see profit and growth.” The Biden administration, she said, has invested in a variety of new ways for the public and private sector to work together to massively accelerate the movement of technology into the market.Wednesday’s talk drew a capacity audience of nearly 300 people in MIT’s Wong Auditorium and was hosted by the Manufacturing@MIT Working Group. The event included introductory remarks by Suzanne Berger, an Institute Professor and a longtime expert on the innovation economy, and Nergis Mavalvala, dean of the School of Science and an astrophysicist and leader in gravitational-wave detection.Introducing Mavalvala, Berger said the 2015 announcement of the discovery of gravitational waves “was the day I felt proudest and most elated to be a member of the MIT community,” and noted that U.S. government support helped make the research possible. Mavalvala, in turn, said MIT was “especially honored” to hear Prabhakar discuss leading-edge research and acknowledge the role of universities in strengthening the country’s science and technology sectors.Prabhakar has extensive experience in both government and the private sector. She has been OSTP director and co-chair of PCAST since October of 2022. She served as director of the Defense Advanced Research Projects Agency (DARPA) from 2012 to 2017 and director of the National Institute of Standards and Technology (NIST) from 1993 to 1997.She has also held executive positions at Raychem and Interval Research, and spent a decade at the investment firm U.S. Venture Partners. An engineer by training, Prabhakar earned a BS in electrical engineering from Texas Tech University in 1979, an MA in electrical engineering from Caltech in 1980, and a PhD in applied physics from Caltech in 1984.Among other remarks about medicine, Prabhakar touted the Biden administration’s “Cancer Moonshot” program, which aims to cut the cancer death rate in half over the next 25 years through multiple approaches, from better health care provision and cancer detection to limiting public exposure to carcinogens. We should be striving, Prabhakar said, for “a future in which people take good health for granted and can get on with their lives.”On AI, she heralded both the promise and concerns about technology, saying, “I think it’s time for active steps to get on a path to where it actually allows people to do more and earn more.”When it comes to climate change, Prabhakar said, “We all understand that the climate is going to change. But it’s in our hands how severe those changes get. And it’s possible that we can build a better future.” She noted the bipartisan infrastructure bill signed into law in 2021 and the Biden administration’s Inflation Reduction Act as important steps forward in this fight.“Together those are making the single biggest investment anyone anywhere on the planet has ever made in the clean energy transition,” she said. “I used to feel hopeless about our ability to do that, and it gives me tremendous hope.”After her talk, Prabhakar was joined onstage for a group discussion with the three co-presidents of the MIT Energy and Climate Club: Laurentiu Anton, a doctoral candidate in electrical engineering and computer science; Rosie Keller, an MBA candidate at the MIT Sloan School of Management; and Thomas Lee, a doctoral candidate in MIT’s Institute for Data, Systems, and Society.Asked about the seemingly sagging public confidence in science today, Prabhakar offered a few thoughts.“The first thing I would say is, don’t take it personally,” Prabhakar said, noting that any dip in public regard for science is less severe than the diminished public confidence in other institutions.Adding some levity, she observed that in polling about which occupations are regarded as being desirable for a marriage partner to have, “scientist” still ranks highly.“Scientists still do really well on that front, we’ve got that going for us,” she quipped.More seriously, Prabhakar observed, rather than “preaching” at the public, scientists should recognize that “part of the job for us is to continue to be clear about what we know are the facts, and to present them clearly but humbly, and to be clear that we’re going to continue working to learn more.” At the same time, she continued, scientists can always reinforce that “oh, by the way, facts are helpful things that can actually help you make better choices about how the future turns out. I think that would be better in my view.”Prabhakar said that her White House work had been guided, in part, by one of the overarching themes that President Biden has often reinforced.“He thinks about America as a nation that can be described in a single word, and that word is ‘possibilities,’” she said. “And that idea, that is such a big idea, it lights me up. I think of what we do in the world of science and technology and innovation as really part and parcel of creating those possibilities.”Ultimately, Prabhakar said, at all times and all points in American history, scientists and technologists must continue “to prove once more that when people come together and do this work … we do it in a way that builds opportunity and expands opportunity for everyone in our country. I think this is the great privilege we all have in the work we do, and it’s also our responsibility.” More

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      in Environment

      Advancing urban tree monitoring with AI-powered digital twins

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      The Irish philosopher George Berkely, best known for his theory of immaterialism, once famously mused, “If a tree falls in a forest and no one is around to hear it, does it make a sound?”What about AI-generated trees? They probably wouldn’t make a sound, but they will be critical nonetheless for applications such as adaptation of urban flora to climate change. To that end, the novel “Tree-D Fusion” system developed by researchers at the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL), Google, and Purdue University merges AI and tree-growth models with Google’s Auto Arborist data to create accurate 3D models of existing urban trees. The project has produced the first-ever large-scale database of 600,000 environmentally aware, simulation-ready tree models across North America.“We’re bridging decades of forestry science with modern AI capabilities,” says Sara Beery, MIT electrical engineering and computer science (EECS) assistant professor, MIT CSAIL principal investigator, and a co-author on a new paper about Tree-D Fusion. “This allows us to not just identify trees in cities, but to predict how they’ll grow and impact their surroundings over time. We’re not ignoring the past 30 years of work in understanding how to build these 3D synthetic models; instead, we’re using AI to make this existing knowledge more useful across a broader set of individual trees in cities around North America, and eventually the globe.”Tree-D Fusion builds on previous urban forest monitoring efforts that used Google Street View data, but branches it forward by generating complete 3D models from single images. While earlier attempts at tree modeling were limited to specific neighborhoods, or struggled with accuracy at scale, Tree-D Fusion can create detailed models that include typically hidden features, such as the back side of trees that aren’t visible in street-view photos.The technology’s practical applications extend far beyond mere observation. City planners could use Tree-D Fusion to one day peer into the future, anticipating where growing branches might tangle with power lines, or identifying neighborhoods where strategic tree placement could maximize cooling effects and air quality improvements. These predictive capabilities, the team says, could change urban forest management from reactive maintenance to proactive planning.A tree grows in Brooklyn (and many other places)The researchers took a hybrid approach to their method, using deep learning to create a 3D envelope of each tree’s shape, then using traditional procedural models to simulate realistic branch and leaf patterns based on the tree’s genus. This combo helped the model predict how trees would grow under different environmental conditions and climate scenarios, such as different possible local temperatures and varying access to groundwater.Now, as cities worldwide grapple with rising temperatures, this research offers a new window into the future of urban forests. In a collaboration with MIT’s Senseable City Lab, the Purdue University and Google team is embarking on a global study that re-imagines trees as living climate shields. Their digital modeling system captures the intricate dance of shade patterns throughout the seasons, revealing how strategic urban forestry could hopefully change sweltering city blocks into more naturally cooled neighborhoods.“Every time a street mapping vehicle passes through a city now, we’re not just taking snapshots — we’re watching these urban forests evolve in real-time,” says Beery. “This continuous monitoring creates a living digital forest that mirrors its physical counterpart, offering cities a powerful lens to observe how environmental stresses shape tree health and growth patterns across their urban landscape.”AI-based tree modeling has emerged as an ally in the quest for environmental justice: By mapping urban tree canopy in unprecedented detail, a sister project from the Google AI for Nature team has helped uncover disparities in green space access across different socioeconomic areas. “We’re not just studying urban forests — we’re trying to cultivate more equity,” says Beery. The team is now working closely with ecologists and tree health experts to refine these models, ensuring that as cities expand their green canopies, the benefits branch out to all residents equally.It’s a breezeWhile Tree-D fusion marks some major “growth” in the field, trees can be uniquely challenging for computer vision systems. Unlike the rigid structures of buildings or vehicles that current 3D modeling techniques handle well, trees are nature’s shape-shifters — swaying in the wind, interweaving branches with neighbors, and constantly changing their form as they grow. The Tree-D fusion models are “simulation-ready” in that they can estimate the shape of the trees in the future, depending on the environmental conditions.“What makes this work exciting is how it pushes us to rethink fundamental assumptions in computer vision,” says Beery. “While 3D scene understanding techniques like photogrammetry or NeRF [neural radiance fields] excel at capturing static objects, trees demand new approaches that can account for their dynamic nature, where even a gentle breeze can dramatically alter their structure from moment to moment.”The team’s approach of creating rough structural envelopes that approximate each tree’s form has proven remarkably effective, but certain issues remain unsolved. Perhaps the most vexing is the “entangled tree problem;” when neighboring trees grow into each other, their intertwined branches create a puzzle that no current AI system can fully unravel.The scientists see their dataset as a springboard for future innovations in computer vision, and they’re already exploring applications beyond street view imagery, looking to extend their approach to platforms like iNaturalist and wildlife camera traps.“This marks just the beginning for Tree-D Fusion,” says Jae Joong Lee, a Purdue University PhD student who developed, implemented and deployed the Tree-D-Fusion algorithm. “Together with my collaborators, I envision expanding the platform’s capabilities to a planetary scale. Our goal is to use AI-driven insights in service of natural ecosystems — supporting biodiversity, promoting global sustainability, and ultimately, benefiting the health of our entire planet.”Beery and Lee’s co-authors are Jonathan Huang, Scaled Foundations head of AI (formerly of Google); and four others from Purdue University: PhD students Jae Joong Lee and Bosheng Li, Professor and Dean’s Chair of Remote Sensing Songlin Fei, Assistant Professor Raymond Yeh, and Professor and Associate Head of Computer Science Bedrich Benes. Their work is based on efforts supported by the United States Department of Agriculture’s (USDA) Natural Resources Conservation Service and is directly supported by the USDA’s National Institute of Food and Agriculture. The researchers presented their findings at the European Conference on Computer Vision this month.  More

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      in Energy

      A nonflammable battery to power a safer, decarbonized future

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      Lithium-ion batteries are the workhorses of home electronics and are powering an electric revolution in transportation. But they are not suitable for every application.A key drawback is their flammability and toxicity, which make large-scale lithium-ion energy storage a bad fit in densely populated city centers and near metal processing or chemical manufacturing plants.Now Alsym Energy has developed a nonflammable, nontoxic alternative to lithium-ion batteries to help renewables like wind and solar bridge the gap in a broader range of sectors. The company’s electrodes use relatively stable, abundant materials, and its electrolyte is primarily water with some nontoxic add-ons.“Renewables are intermittent, so you need storage, and to really solve the decarbonization problem, we need to be able to make these batteries anywhere at low cost,” says Alsym co-founder and MIT Professor Kripa Varanasi.The company believes its batteries, which are currently being tested by potential customers around the world, hold enormous potential to decarbonize the high-emissions industrial manufacturing sector, and they see other applications ranging from mining to powering data centers, homes, and utilities.“We are enabling a decarbonization of markets that was not possible before,” Alsym co-founder and CEO Mukesh Chatter says. “No chemical or steel plant would dare put a lithium battery close to their premises because of the flammability, and industrial emissions are a much bigger problem than passenger cars. With this approach, we’re able to offer a new path.”Helping 1 billion peopleChatter started a telecommunications company with serial entrepreneurs and longtime members of the MIT community Ray Stata ’57, SM ’58 and Alec Dingee ’52 in 1997. Since the company was acquired in 1999, Chatter and his wife have started other ventures and invested in some startups, but after losing his mother to cancer in 2012, Chatter decided he wanted to maximize his impact by only working on technologies that could reach 1 billion people or more.The problem Chatter decided to focus on was electricity access.“The intent was to light up the homes of at least 1 billion people around the world who either did not have electricity, or only got it part of the time, condemning them basically to a life of poverty in the 19th century,” Chatter says. “When you don’t have access to electricity, you also don’t have the internet, cell phones, education, etc.”To solve the problem, Chatter decided to fund research into a new kind of battery. The battery had to be cheap enough to be adopted in low-resource settings, safe enough to be deployed in crowded areas, and work well enough to support two light bulbs, a fan, a refrigerator, and an internet modem.At first, Chatter was surprised how few takers he had to start the research, even from researchers at the top universities in the world.“It’s a burning problem, but the risk of failure was so high that nobody wanted to take the chance,” Chatter recalls.He finally found his partners in Varanasi, Rensselaer Polytechnic Institute Professor Nikhil Koratkar and Rensselaer researcher Rahul Mukherjee. Varanasi, who notes he’s been at MIT for 22 years, says the Institute’s culture gave him the confidence to tackle big problems.“My students, postdocs, and colleagues are inspirational to me,” he says. “The MIT ecosystem infuses us with this resolve to go after problems that look insurmountable.”Varanasi leads an interdisciplinary lab at MIT dedicated to understanding physicochemical and biological phenomena. His research has spurred the creation of materials, devices, products, and processes to tackle challenges in energy, agriculture, and other sectors, as well as startup companies to commercialize this work.“Working at the interfaces of matter has unlocked numerous new research pathways across various fields, and MIT has provided me the creative freedom to explore, discover, and learn, and apply that knowledge to solve critical challenges,” he says. “I was able to draw significantly from my learnings as we set out to develop the new battery technology.”Alsym’s founding team began by trying to design a battery from scratch based on new materials that could fit the parameters defined by Chatter. To make it nonflammable and nontoxic, the founders wanted to avoid lithium and cobalt.After evaluating many different chemistries, the founders settled on Alsym’s current approach, which was finalized in 2020.Although the full makeup of Alsym’s battery is still under wraps as the company waits to be granted patents, one of Alsym’s electrodes is made mostly of manganese oxide while the other is primarily made of a metal oxide. The electrolyte is primarily water.There are several advantages to Alsym’s new battery chemistry. Because the battery is inherently safer and more sustainable than lithium-ion, the company doesn’t need the same safety protections or cooling equipment, and it can pack its batteries close to each other without fear of fires or explosions. Varanasi also says the battery can be manufactured in any of today’s lithium-ion plants with minimal changes and at significantly lower operating cost.“We are very excited right now,” Chatter says. “We started out wanting to light up 1 billion people’s homes, and now in addition to the original goal we have a chance to impact the entire globe if we are successful at cutting back industrial emissions.”A new platform for energy storageAlthough the batteries don’t quite reach the energy density of lithium-ion batteries, Varanasi says Alsym is first among alternative chemistries at the system-level. He says 20-foot containers of Alsym’s batteries can provide 1.7 megawatt hours of electricity. The batteries can also fast-charge over four hours and can be configured to discharge over anywhere from two to 110 hours.“We’re highly configurable, and that’s important because depending on where you are, you can sometimes run on two cycles a day with solar, and in combination with wind, you could truly get 24/7 electricity,” Chatter says. “The need to do multiday or long duration storage is a small part of the market, but we support that too.”Alsym has been manufacturing prototypes at a small facility in Woburn, Massachusetts, for the last two years, and early this year it expanded its capacity and began to send samples to customers for field testing.In addition to large utilities, the company is working with municipalities, generator manufacturers, and providers of behind-the-meter power for residential and commercial buildings. The company is also in discussion with a large chemical manufacturers and metal processing plants to provide energy storage system to reduce their carbon footprint, something they say was not feasible with lithium-ion batteries, due to their flammability, or with nonlithium batteries, due to their large space requirements.Another critical area is data centers. With the growth of AI, the demand for data centers — and their energy consumption — is set to surge.“We must power the AI and digitization revolution without compromising our planet,” says Varanasi, adding that lithium batteries are unsuitable for co-location with data centers due to flammability risks. “Alsym batteries are well-positioned to offer a safer, more sustainable alternative. Intermittency is also a key issue for electrolyzers used in green hydrogen production and other markets.”Varanasi sees Alsym as a platform company, and Chatter says Alsym is already working on other battery chemistries that have higher densities and maintain performance at even more extreme temperatures.“When you use a single material in any battery, and the whole world starts to use it, you run out of that material,” Varanasi says. “What we have is a platform that has enabled us to not just to come up with just one chemistry, but at least three or four chemistries targeted at different applications so no one particular set of materials will be stressed in terms of supply.” More

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      in Energy

      Reality check on technologies to remove carbon dioxide from the air

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      In 2015, 195 nations plus the European Union signed the Paris Agreement and pledged to undertake plans designed to limit the global temperature increase to 1.5 degrees Celsius. Yet in 2023, the world exceeded that target for most, if not all of, the year — calling into question the long-term feasibility of achieving that target.To do so, the world must reduce the levels of greenhouse gases in the atmosphere, and strategies for achieving levels that will “stabilize the climate” have been both proposed and adopted. Many of those strategies combine dramatic cuts in carbon dioxide (CO2) emissions with the use of direct air capture (DAC), a technology that removes CO2 from the ambient air. As a reality check, a team of researchers in the MIT Energy Initiative (MITEI) examined those strategies, and what they found was alarming: The strategies rely on overly optimistic — indeed, unrealistic — assumptions about how much CO2 could be removed by DAC. As a result, the strategies won’t perform as predicted. Nevertheless, the MITEI team recommends that work to develop the DAC technology continue so that it’s ready to help with the energy transition — even if it’s not the silver bullet that solves the world’s decarbonization challenge.DAC: The promise and the realityIncluding DAC in plans to stabilize the climate makes sense. Much work is now under way to develop DAC systems, and the technology looks promising. While companies may never run their own DAC systems, they can already buy “carbon credits” based on DAC. Today, a multibillion-dollar market exists on which entities or individuals that face high costs or excessive disruptions to reduce their own carbon emissions can pay others to take emissions-reducing actions on their behalf. Those actions can involve undertaking new renewable energy projects or “carbon-removal” initiatives such as DAC or afforestation/reforestation (planting trees in areas that have never been forested or that were forested in the past). DAC-based credits are especially appealing for several reasons, explains Howard Herzog, a senior research engineer at MITEI. With DAC, measuring and verifying the amount of carbon removed is straightforward; the removal is immediate, unlike with planting forests, which may take decades to have an impact; and when DAC is coupled with CO2 storage in geologic formations, the CO2 is kept out of the atmosphere essentially permanently — in contrast to, for example, sequestering it in trees, which may one day burn and release the stored CO2.Will current plans that rely on DAC be effective in stabilizing the climate in the coming years? To find out, Herzog and his colleagues Jennifer Morris and Angelo Gurgel, both MITEI principal research scientists, and Sergey Paltsev, a MITEI senior research scientist — all affiliated with the MIT Center for Sustainability Science and Strategy (CS3) — took a close look at the modeling studies on which those plans are based.Their investigation identified three unavoidable engineering challenges that together lead to a fourth challenge — high costs for removing a single ton of CO2 from the atmosphere. The details of their findings are reported in a paper published in the journal One Earth on Sept. 20.Challenge 1: Scaling upWhen it comes to removing CO2 from the air, nature presents “a major, non-negotiable challenge,” notes the MITEI team: The concentration of CO2 in the air is extremely low — just 420 parts per million, or roughly 0.04 percent. In contrast, the CO2 concentration in flue gases emitted by power plants and industrial processes ranges from 3 percent to 20 percent. Companies now use various carbon capture and sequestration (CCS) technologies to capture CO2 from their flue gases, but capturing CO2 from the air is much more difficult. To explain, the researchers offer the following analogy: “The difference is akin to needing to find 10 red marbles in a jar of 25,000 marbles of which 24,990 are blue [the task representing DAC] versus needing to find about 10 red marbles in a jar of 100 marbles of which 90 are blue [the task for CCS].”Given that low concentration, removing a single metric ton (tonne) of CO2 from air requires processing about 1.8 million cubic meters of air, which is roughly equivalent to the volume of 720 Olympic-sized swimming pools. And all that air must be moved across a CO2-capturing sorbent — a feat requiring large equipment. For example, one recently proposed design for capturing 1 million tonnes of CO2 per year would require an “air contactor” equivalent in size to a structure about three stories high and three miles long.Recent modeling studies project DAC deployment on the scale of 5 to 40 gigatonnes of CO2 removed per year. (A gigatonne equals 1 billion metric tonnes.) But in their paper, the researchers conclude that the likelihood of deploying DAC at the gigatonne scale is “highly uncertain.”Challenge 2: Energy requirementGiven the low concentration of CO2 in the air and the need to move large quantities of air to capture it, it’s no surprise that even the best DAC processes proposed today would consume large amounts of energy — energy that’s generally supplied by a combination of electricity and heat. Including the energy needed to compress the captured CO2 for transportation and storage, most proposed processes require an equivalent of at least 1.2 megawatt-hours of electricity for each tonne of CO2 removed.The source of that electricity is critical. For example, using coal-based electricity to drive an all-electric DAC process would generate 1.2 tonnes of CO2 for each tonne of CO2 captured. The result would be a net increase in emissions, defeating the whole purpose of the DAC. So clearly, the energy requirement must be satisfied using either low-carbon electricity or electricity generated using fossil fuels with CCS. All-electric DAC deployed at large scale — say, 10 gigatonnes of CO2 removed annually — would require 12,000 terawatt-hours of electricity, which is more than 40 percent of total global electricity generation today.Electricity consumption is expected to grow due to increasing overall electrification of the world economy, so low-carbon electricity will be in high demand for many competing uses — for example, in power generation, transportation, industry, and building operations. Using clean electricity for DAC instead of for reducing CO2 emissions in other critical areas raises concerns about the best uses of clean electricity.Many studies assume that a DAC unit could also get energy from “waste heat” generated by some industrial process or facility nearby. In the MITEI researchers’ opinion, “that may be more wishful thinking than reality.” The heat source would need to be within a few miles of the DAC plant for transporting the heat to be economical; given its high capital cost, the DAC plant would need to run nonstop, requiring constant heat delivery; and heat at the temperature required by the DAC plant would have competing uses, for example, for heating buildings. Finally, if DAC is deployed at the gigatonne per year scale, waste heat will likely be able to provide only a small fraction of the needed energy.Challenge 3: SitingSome analysts have asserted that, because air is everywhere, DAC units can be located anywhere. But in reality, siting a DAC plant involves many complex issues. As noted above, DAC plants require significant amounts of energy, so having access to enough low-carbon energy is critical. Likewise, having nearby options for storing the removed CO2 is also critical. If storage sites or pipelines to such sites don’t exist, major new infrastructure will need to be built, and building new infrastructure of any kind is expensive and complicated, involving issues related to permitting, environmental justice, and public acceptability — issues that are, in the words of the researchers, “commonly underestimated in the real world and neglected in models.”Two more siting needs must be considered. First, meteorological conditions must be acceptable. By definition, any DAC unit will be exposed to the elements, and factors like temperature and humidity will affect process performance and process availability. And second, a DAC plant will require some dedicated land — though how much is unclear, as the optimal spacing of units is as yet unresolved. Like wind turbines, DAC units need to be properly spaced to ensure maximum performance such that one unit is not sucking in CO2-depleted air from another unit.Challenge 4: CostConsidering the first three challenges, the final challenge is clear: the cost per tonne of CO2 removed is inevitably high. Recent modeling studies assume DAC costs as low as $100 to $200 per ton of CO2 removed. But the researchers found evidence suggesting far higher costs.To start, they cite typical costs for power plants and industrial sites that now use CCS to remove CO2 from their flue gases. The cost of CCS in such applications is estimated to be in the range of $50 to $150 per ton of CO2 removed. As explained above, the far lower concentration of CO2 in the air will lead to substantially higher costs.As explained under Challenge 1, the DAC units needed to capture the required amount of air are massive. The capital cost of building them will be high, given labor, materials, permitting costs, and so on. Some estimates in the literature exceed $5,000 per tonne captured per year.Then there are the ongoing costs of energy. As noted under Challenge 2, removing 1 tonne of CO2 requires the equivalent of 1.2 megawatt-hours of electricity. If that electricity costs $0.10 per kilowatt-hour, the cost of just the electricity needed to remove 1 tonne of CO2 is $120. The researchers point out that assuming such a low price is “questionable,” given the expected increase in electricity demand, future competition for clean energy, and higher costs on a system dominated by renewable — but intermittent — energy sources.Then there’s the cost of storage, which is ignored in many DAC cost estimates.Clearly, many considerations show that prices of $100 to $200 per tonne are unrealistic, and assuming such low prices will distort assessments of strategies, leading them to underperform going forward.The bottom lineIn their paper, the MITEI team calls DAC a “very seductive concept.” Using DAC to suck CO2 out of the air and generate high-quality carbon-removal credits can offset reduction requirements for industries that have hard-to-abate emissions. By doing so, DAC would minimize disruptions to key parts of the world’s economy, including air travel, certain carbon-intensive industries, and agriculture. However, the world would need to generate billions of tonnes of CO2 credits at an affordable price. That prospect doesn’t look likely. The largest DAC plant in operation today removes just 4,000 tonnes of CO2 per year, and the price to buy the company’s carbon-removal credits on the market today is $1,500 per tonne.The researchers recognize that there is room for energy efficiency improvements in the future, but DAC units will always be subject to higher work requirements than CCS applied to power plant or industrial flue gases, and there is not a clear pathway to reducing work requirements much below the levels of current DAC technologies.Nevertheless, the researchers recommend that work to develop DAC continue “because it may be needed for meeting net-zero emissions goals, especially given the current pace of emissions.” But their paper concludes with this warning: “Given the high stakes of climate change, it is foolhardy to rely on DAC to be the hero that comes to our rescue.” More

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      in Energy

      Turning automotive engines into modular chemical plants to make green fuels

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      Reducing methane emissions is a top priority in the fight against climate change because of its propensity to trap heat in the atmosphere: Methane’s warming effects are 84 times more potent than CO2 over a 20-year timescale.And yet, as the main component of natural gas, methane is also a valuable fuel and a precursor to several important chemicals. The main barrier to using methane emissions to create carbon-negative materials is that human sources of methane gas — landfills, farms, and oil and gas wells — are relatively small and spread out across large areas, while traditional chemical processing facilities are huge and centralized. That makes it prohibitively expensive to capture, transport, and convert methane gas into anything useful. As a result, most companies burn or “flare” their methane at the site where it’s emitted, seeing it as a sunk cost and an environmental liability.The MIT spinout Emvolon is taking a new approach to processing methane by repurposing automotive engines to serve as modular, cost-effective chemical plants. The company’s systems can take methane gas and produce liquid fuels like methanol and ammonia on-site; these fuels can then be used or transported in standard truck containers.”We see this as a new way of chemical manufacturing,” Emvolon co-founder and CEO Emmanuel Kasseris SM ’07, PhD ’11 says. “We’re starting with methane because methane is an abundant emission that we can use as a resource. With methane, we can solve two problems at the same time: About 15 percent of global greenhouse gas emissions come from hard-to-abate sectors that need green fuel, like shipping, aviation, heavy heavy-duty trucks, and rail. Then another 15 percent of emissions come from distributed methane emissions like landfills and oil wells.”By using mass-produced engines and eliminating the need to invest in infrastructure like pipelines, the company says it’s making methane conversion economically attractive enough to be adopted at scale. The system can also take green hydrogen produced by intermittent renewables and turn it into ammonia, another fuel that can also be used to decarbonize fertilizers.“In the future, we’re going to need green fuels because you can’t electrify a large ship or plane — you have to use a high-energy-density, low-carbon-footprint, low-cost liquid fuel,” Kasseris says. “The energy resources to produce those green fuels are either distributed, as is the case with methane, or variable, like wind. So, you cannot have a massive plant [producing green fuels] that has its own zip code. You either have to be distributed or variable, and both of those approaches lend themselves to this modular design.”From a “crazy idea” to a companyKasseris first came to MIT to study mechanical engineering as a graduate student in 2004, when he worked in the Sloan Automotive Lab on a report on the future of transportation. For his PhD, he developed a novel technology for improving internal combustion engine fuel efficiency for a consortium of automotive and energy companies, which he then went to work for after graduation.Around 2014, he was approached by Leslie Bromberg ’73, PhD ’77, a serial inventor with more than 100 patents, who has been a principal research engineer in MIT’s Plasma Science and Fusion Center for nearly 50 years.“Leslie had this crazy idea of repurposing an internal combustion engine as a reactor,” Kasseris recalls. “I had looked at that while working in industry, and I liked it, but my company at the time thought the work needed more validation.”Bromberg had done that validation through a U.S. Department of Energy-funded project in which he used a diesel engine to “reform” methane — a high-pressure chemical reaction in which methane is combined with steam and oxygen to produce hydrogen. The work impressed Kasseris enough to bring him back to MIT as a research scientist in 2016.“We worked on that idea in addition to some other projects, and eventually it had reached the point where we decided to license the work from MIT and go full throttle,” Kasseris recalls. “It’s very easy to work with MIT’s Technology Licensing Office when you are an MIT inventor. You can get a low-cost licensing option, and you can do a lot with that, which is important for a new company. Then, once you are ready, you can finalize the license, so MIT was instrumental.”Emvolon continued working with MIT’s research community, sponsoring projects with Professor Emeritus John Heywood and participating in the MIT Venture Mentoring Service and the MIT Industrial Liaison Program.An engine-powered chemical plantAt the core of Emvolon’s system is an off-the-shelf automotive engine that runs “fuel rich” — with a higher ratio of fuel to air than what is needed for complete combustion.“That’s easy to say, but it takes a lot of [intellectual property], and that’s what was developed at MIT,” Kasseris says. “Instead of burning the methane in the gas to carbon dioxide and water, you partially burn it, or partially oxidize it, to carbon monoxide and hydrogen, which are the building blocks to synthesize a variety of chemicals.”The hydrogen and carbon monoxide are intermediate products used to synthesize different chemicals through further reactions. Those processing steps take place right next to the engine, which makes its own power. Each of Emvolon’s standalone systems fits within a 40-foot shipping container and can produce about 8 tons of methanol per day from 300,000 standard cubic feet of methane gas.The company is starting with green methanol because it’s an ideal fuel for hard-to-abate sectors such as shipping and heavy-duty transport, as well as an excellent feedstock for other high-value chemicals, such as sustainable aviation fuel. Many shipping vessels have already converted to run on green methanol in an effort to meet decarbonization goals.This summer, the company also received a grant from the Department of Energy to adapt its process to produce clean liquid fuels from power sources like solar and wind.“We’d like to expand to other chemicals like ammonia, but also other feedstocks, such as biomass and hydrogen from renewable electricity, and we already have promising results in that direction” Kasseris says. “We think we have a good solution for the energy transition and, in the later stages of the transition, for e-manufacturing.”A scalable approachEmvolon has already built a system capable of producing up to six barrels of green methanol a day in its 5,000 square-foot headquarters in Woburn, Massachusetts.“For chemical technologies, people talk about scale up risk, but with an engine, if it works in a single cylinder, we know it will work in a multicylinder engine,” Kasseris says. “It’s just engineering.”Last month, Emvolon announced an agreement with Montauk Renewables to build a commercial-scale demonstration unit next to a Texas landfill that will initially produce up to 15,000 gallons of green methanol a year and later scale up to 2.5 million gallons. That project could be expanded tenfold by scaling across Montauk’s other sites.“Our whole process was designed to be a very realistic approach to the energy transition,” Kasseris says. “Our solution is designed to produce green fuels and chemicals at prices that the markets are willing to pay today, without the need for subsidies. Using the engines as chemical plants, we can get the capital expenditure per unit output close to that of a large plant, but at a modular scale that enables us to be next to low-cost feedstock. Furthermore, our modular systems require small investments — of $1 to 10 million — that are quickly deployed, one at a time, within weeks, as opposed to massive chemical plants that require multiyear capital construction projects and cost hundreds of millions.” More

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      in Energy

      Ensuring a durable transition

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      To fend off the worst impacts of climate change, “we have to decarbonize, and do it even faster,” said William H. Green, director of the MIT Energy Initiative (MITEI) and Hoyt C. Hottel Professor, MIT Department of Chemical Engineering, at MITEI’s Annual Research Conference.“But how the heck do we actually achieve this goal when the United States is in the middle of a divisive election campaign, and globally, we’re facing all kinds of geopolitical conflicts, trade protectionism, weather disasters, increasing demand from developing countries building a middle class, and data centers in countries like the U.S.?”Researchers, government officials, and business leaders convened in Cambridge, Massachusetts, Sept. 25-26 to wrestle with this vexing question at the conference that was themed, “A durable energy transition: How to stay on track in the face of increasing demand and unpredictable obstacles.”“In this room we have a lot of power,” said Green, “if we work together, convey to all of society what we see as real pathways and policies to solve problems, and take collective action.”The critical role of consensus-building in driving the energy transition arose repeatedly in conference sessions, whether the topic involved developing and adopting new technologies, constructing and siting infrastructure, drafting and passing vital energy policies, or attracting and retaining a skilled workforce.Resolving conflictsThere is “blowback and a social cost” in transitioning away from fossil fuels, said Stephen Ansolabehere, the Frank G. Thompson Professor of Government at Harvard University, in a panel on the social barriers to decarbonization. “Companies need to engage differently and recognize the rights of communities,” he said.Nora DeDontney, director of development at Vineyard Offshore, described her company’s two years of outreach and negotiations to bring large cables from ocean-based wind turbines onshore.“Our motto is, ‘community first,’” she said. Her company works to mitigate any impacts towns might feel because of offshore wind infrastructure construction with projects, such as sewer upgrades; provides workforce training to Tribal Nations; and lays out wind turbines in a manner that provides safe and reliable areas for local fisheries.Elsa A. Olivetti, professor in the Department of Materials Science and Engineering at MIT and the lead of the Decarbonization Mission of MIT’s new Climate Project, discussed the urgent need for rapid scale-up of mineral extraction. “Estimates indicate that to electrify the vehicle fleet by 2050, about six new large copper mines need to come on line each year,” she said. To meet the demand for metals in the United States means pushing into Indigenous lands and environmentally sensitive habitats. “The timeline of permitting is not aligned with the temporal acceleration needed,” she said.Larry Susskind, the Ford Professor of Urban and Environmental Planning in the MIT Department of Urban Studies and Planning, is trying to resolve such tensions with universities playing the role of mediators. He is creating renewable energy clinics where students train to participate in emerging disputes over siting. “Talk to people before decisions are made, conduct joint fact finding, so that facilities reduce harms and share the benefits,” he said.Clean energy boom and pressureA relatively recent and unforeseen increase in demand for energy comes from data centers, which are being built by large technology companies for new offerings, such as artificial intelligence.“General energy demand was flat for 20 years — and now, boom,” said Sean James, Microsoft’s senior director of data center research. “It caught utilities flatfooted.” With the expansion of AI, the rush to provision data centers with upwards of 35 gigawatts of new (and mainly renewable) power in the near future, intensifies pressure on big companies to balance the concerns of stakeholders across multiple domains. Google is pursuing 24/7 carbon-free energy by 2030, said Devon Swezey, the company’s senior manager for global energy and climate.“We’re pursuing this by purchasing more and different types of clean energy locally, and accelerating technological innovation such as next-generation geothermal projects,” he said. Pedro Gómez Lopez, strategy and development director, Ferrovial Digital, which designs and constructs data centers, incorporates renewable energy into their projects, which contributes to decarbonization goals and benefits to locales where they are sited. “We can create a new supply of power, taking the heat generated by a data center to residences or industries in neighborhoods through District Heating initiatives,” he said.The Inflation Reduction Act and other legislation has ramped up employment opportunities in clean energy nationwide, touching every region, including those most tied to fossil fuels. “At the start of 2024 there were about 3.5 million clean energy jobs, with ‘red’ states showing the fastest growth in clean energy jobs,” said David S. Miller, managing partner at Clean Energy Ventures. “The majority (58 percent) of new jobs in energy are now in clean energy — that transition has happened. And one-in-16 new jobs nationwide were in clean energy, with clean energy jobs growing more than three times faster than job growth economy-wide”In this rapid expansion, the U.S. Department of Energy (DoE) is prioritizing economically marginalized places, according to Zoe Lipman, lead for good jobs and labor standards in the Office of Energy Jobs at the DoE. “The community benefit process is integrated into our funding,” she said. “We are creating the foundation of a virtuous circle,” encouraging benefits to flow to disadvantaged and energy communities, spurring workforce training partnerships, and promoting well-paid union jobs. “These policies incentivize proactive community and labor engagement, and deliver community benefits, both of which are key to building support for technological change.”Hydrogen opportunity and challengeWhile engagement with stakeholders helps clear the path for implementation of technology and the spread of infrastructure, there remain enormous policy, scientific, and engineering challenges to solve, said multiple conference participants. In a “fireside chat,” Prasanna V. Joshi, vice president of low-carbon-solutions technology at ExxonMobil, and Ernest J. Moniz, professor of physics and special advisor to the president at MIT, discussed efforts to replace natural gas and coal with zero-carbon hydrogen in order to reduce greenhouse gas emissions in such major industries as steel and fertilizer manufacturing.“We have gone into an era of industrial policy,” said Moniz, citing a new DoE program offering incentives to generate demand for hydrogen — more costly than conventional fossil fuels — in end-use applications. “We are going to have to transition from our current approach, which I would call carrots-and-twigs, to ultimately, carrots-and-sticks,” Moniz warned, in order to create “a self-sustaining, major, scalable, affordable hydrogen economy.”To achieve net zero emissions by 2050, ExxonMobil intends to use carbon capture and sequestration in natural gas-based hydrogen and ammonia production. Ammonia can also serve as a zero-carbon fuel. Industry is exploring burning ammonia directly in coal-fired power plants to extend the hydrogen value chain. But there are challenges. “How do you burn 100 percent ammonia?”, asked Joshi. “That’s one of the key technology breakthroughs that’s needed.” Joshi believes that collaboration with MIT’s “ecosystem of breakthrough innovation” will be essential to breaking logjams around the hydrogen and ammonia-based industries.MIT ingenuity essentialThe energy transition is placing very different demands on different regions around the world. Take India, where today per capita power consumption is one of the lowest. But Indians “are an aspirational people … and with increasing urbanization and industrial activity, the growth in power demand is expected to triple by 2050,” said Praveer Sinha, CEO and managing director of the Tata Power Co. Ltd., in his keynote speech. For that nation, which currently relies on coal, the move to clean energy means bringing another 300 gigawatts of zero-carbon capacity online in the next five years. Sinha sees this power coming from wind, solar, and hydro, supplemented by nuclear energy.“India plans to triple nuclear power generation capacity by 2032, and is focusing on advancing small modular reactors,” said Sinha. “The country also needs the rapid deployment of storage solutions to firm up the intermittent power.” The goal is to provide reliable electricity 24/7 to a population living both in large cities and in geographically remote villages, with the help of long-range transmission lines and local microgrids. “India’s energy transition will require innovative and affordable technology solutions, and there is no better place to go than MIT, where you have the best brains, startups, and technology,” he said.These assets were on full display at the conference. Among them a cluster of young businesses, including:the MIT spinout Form Energy, which has developed a 100-hour iron battery as a backstop to renewable energy sources in case of multi-day interruptions;startup Noya that aims for direct air capture of atmospheric CO2 using carbon-based materials;the firm Active Surfaces, with a lightweight material for putting solar photovoltaics in previously inaccessible places;Copernic Catalysts, with new chemistry for making ammonia and sustainable aviation fuel far more inexpensively than current processes; andSesame Sustainability, a software platform spun out of MITEI that gives industries a full financial analysis of the costs and benefits of decarbonization.The pipeline of research talent extended into the undergraduate ranks, with a conference “slam” competition showcasing students’ summer research projects in areas from carbon capture using enzymes to 3D design for the coils used in fusion energy confinement.“MIT students like me are looking to be the next generation of energy leaders, looking for careers where we can apply our engineering skills to tackle exciting climate problems and make a tangible impact,” said Trent Lee, a junior in mechanical engineering researching improvements in lithium-ion energy storage. “We are stoked by the energy transition, because it’s not just the future, but our chance to build it.” More

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      in Environment

      Dancing with currents and waves in the Maldives

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      Any child who’s spent a morning building sandcastles only to watch the afternoon tide ruin them in minutes knows the ocean always wins.Yet, coastal protection strategies have historically focused on battling the sea — attempting to hold back tides and fighting waves and currents by armoring coastlines with jetties and seawalls and taking sand from the ocean floor to “renourish” beaches. These approaches are temporary fixes, but eventually the sea retakes dredged sand, intense surf breaches seawalls, and jetties may just push erosion to a neighboring beach. The ocean wins.With climate change accelerating sea level rise and coastal erosion, the need for better solutions is urgent. Noting that eight of the world’s 10 largest cities are near a coast, a recent National Oceanic and Atmospheric Administration (NOAA) report pointed to 2023’s record-high global sea level and warned that high tide flooding is now 300 to 900 percent more frequent than it was 50 years ago, threatening homes, businesses, roads and bridges, and a range of public infrastructure, from water supplies to power plants.    Island nations face these threats more acutely than other countries and there’s a critical need for better solutions. MIT’s Self-Assembly Lab is refining an innovative one that demonstrates the value of letting nature take its course — with some human coaxing.The Maldives, an Indian Ocean archipelago of nearly 1,200 islands, has traditionally relied on land reclamation via dredging to replenish its eroding coastlines. Working with the Maldivian climate technology company Invena Private Limited, the Self-Assembly Lab is pursuing technological solutions to coastal erosion that mimic nature by harnessing ocean currents to accumulate sand. The Growing Islands project creates and deploys underwater structures that take advantage of wave energy to promote accumulation of sand in strategic locations — helping to expand islands and rebuild coastlines in sustainable ways that can eventually be scaled to coastal areas around the world. “There’s room for a new perspective on climate adaptation, one that builds with nature and leverages data for equitable decision-making,” says Invena co-founder and CEO Sarah Dole.MIT’s pioneering work was the topic of multiple presentations during the United Nations General Assembly and Climate week in New York City in late September. During the week, Self-Assembly Lab co-founder and director Skylar Tibbits and Maldives Minister of Climate Change, Environment and Energy Thoriq Ibrahim also presented findings of the Growing Islands project at MIT Solve’s Global Challenge Finals in New York.“There’s this interesting story that’s emerging around the dynamics of islands,” says Tibbits, whose U.N.-sponsored panel (“Adaptation Through Innovation: How the Private Sector Could Lead the Way”) was co-hosted by the Government of Maldives and the U.S. Agency for International Development, a Growing Islands project funder. In a recent interview, Tibbits said islands “are almost lifelike in their characteristics. They can adapt and grow and change and fluctuate.” Despite some predictions that the Maldives might be inundated by sea level rise and ravaged by erosion, “maybe these islands are actually more resilient than we thought. And maybe there’s a lot more we can learn from these natural formations of sand … maybe they are a better model for how we adapt in the future for sea level rise and erosion and climate change than our man-made cities.”Building on a series of lab experiments begun in 2017, the MIT Self-Assembly Lab and Invena have been testing the efficacy of submersible structures to expand islands and rebuild coasts in the Maldivian capital of Male since 2019. Since then, researchers have honed the experiments based on initial results that demonstrate the promise of using submersible bladders and other structures to utilize natural currents to encourage strategic accumulation of sand.The work is “boundary-pushing,” says Alex Moen, chief explorer engagement officer at the National Geographic Society, an early funder of the project.“Skylar and his team’s innovative technology reflect the type of forward-thinking, solutions-oriented approaches necessary to address the growing threat of sea level rise and erosion to island nations and coastal regions,” Moen said.Most recently, in August 2024, the team submerged a 60-by-60-meter structure in a lagoon near Male. The structure is six times the size of its predecessor installed in 2019, Tibbits says, adding that while the 2019 island-building experiment was a success, ocean currents in the Maldives change seasonally and it only allowed for accretion of sand in one season.“The idea of this was to make it omnidirectional. We wanted to make it work year-round. In any direction, any season, we should be accumulating sand in the same area,” Tibbits says. “This is our largest experiment so far, and I think it has the best chance to accumulate the most amount of sand, so we’re super excited about that.”The next experiment will focus not on building islands, but on overcoming beach erosion. This project, planned for installation later this fall, is envisioned to not only enlarge a beach but also provide recreational benefits for local residents and enhanced habitat for marine life such as fish and corals.“This will be the first large-scale installment that’s intentionally designed for marine habitats,” Tibbits says.Another key aspect of the Growing Islands project takes place in Tibbits’ lab at MIT, where researchers are improving the ability to predict and track changes in low-lying islands through satellite imagery analysis — a technique that promises to facilitate what is now a labor-intensive process involving land and sea surveys by drones and researchers on foot and at sea.“In the future, we could be monitoring and predicting coastlines around the world — every island, every coastline around the world,” Tibbits says. “Are these islands getting smaller, getting bigger? How fast are they losing ground? No one really knows unless we do it by physically surveying right now and that’s not scalable. We do think we have a solution for that coming.”Also hopefully coming soon is financial support for a Mobile Ocean Innovation Lab, a “floating hub” that would provide small island developing states with advanced technologies to foster coastal and climate resilience, conservation, and renewable energy. Eventually, Tibbits says, it would enable the team to travel “any place around the world and partner with local communities, local innovators, artists, and scientists to help co-develop and deploy some of these technologies in a better way.”Expanding the reach of climate change solutions that collaborate with, rather than oppose, natural forces depends on getting more people, organizations, and governments on board. “There are two challenges,” Tibbits says. “One of them is the legacy and history of what humans have done in the past that constrains what we think we can do in the future. For centuries, we’ve been building hard infrastructure at our coastlines, so we have a lot of knowledge about that. We have companies and practices and expertise, and we have a built-up confidence, or ego, around what’s possible. We need to change that.“The second problem,” he continues, “is the money-speed-convenience problem — or the known-versus-unknown problem. The hard infrastructure, whether that’s groins or seawalls or just dredging … these practices in some ways have a clear cost and timeline, and we are used to operating in that mindset. And nature doesn’t work that way. Things grow, change, and adapt on their on their own timeline.”Teaming up with waves and currents to preserve islands and coastlines requires a mindset shift that’s difficult, but ultimately worthwhile, Tibbits contends.“We need to dance with nature. We’re never going to win if we’re trying to resist it,” he says. “But the best-case scenario is that we can take all the positive attributes in the environment and take all the creative, positive things we can do as humans and work together to create something that’s more than the sum of its parts.” More

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      in Environment

      MIT engineers make converting CO2 into useful products more practical

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      As the world struggles to reduce greenhouse gas emissions, researchers are seeking practical, economical ways to capture carbon dioxide and convert it into useful products, such as transportation fuels, chemical feedstocks, or even building materials. But so far, such attempts have struggled to reach economic viability.New research by engineers at MIT could lead to rapid improvements in a variety of electrochemical systems that are under development to convert carbon dioxide into a valuable commodity. The team developed a new design for the electrodes used in these systems, which increases the efficiency of the conversion process.The findings are reported today in the journal Nature Communications, in a paper by MIT doctoral student Simon Rufer, professor of mechanical engineering Kripa Varanasi, and three others.“The CO2 problem is a big challenge for our times, and we are using all kinds of levers to solve and address this problem,” Varanasi says. It will be essential to find practical ways of removing the gas, he says, either from sources such as power plant emissions, or straight out of the air or the oceans. But then, once the CO2 has been removed, it has to go somewhere.A wide variety of systems have been developed for converting that captured gas into a useful chemical product, Varanasi says. “It’s not that we can’t do it — we can do it. But the question is how can we make this efficient? How can we make this cost-effective?”In the new study, the team focused on the electrochemical conversion of CO2 to ethylene, a widely used chemical that can be made into a variety of plastics as well as fuels, and which today is made from petroleum. But the approach they developed could also be applied to producing other high-value chemical products as well, including methane, methanol, carbon monoxide, and others, the researchers say.Currently, ethylene sells for about $1,000 per ton, so the goal is to be able to meet or beat that price. The electrochemical process that converts CO2 into ethylene involves a water-based solution and a catalyst material, which come into contact along with an electric current in a device called a gas diffusion electrode.There are two competing characteristics of the gas diffusion electrode materials that affect their performance: They must be good electrical conductors so that the current that drives the process doesn’t get wasted through resistance heating, but they must also be “hydrophobic,” or water repelling, so the water-based electrolyte solution doesn’t leak through and interfere with the reactions taking place at the electrode surface.Unfortunately, it’s a tradeoff. Improving the conductivity reduces the hydrophobicity, and vice versa. Varanasi and his team set out to see if they could find a way around that conflict, and after many months of trying, they did just that.The solution, devised by Rufer and Varanasi, is elegant in its simplicity. They used a plastic material, PTFE (essentially Teflon), that has been known to have good hydrophobic properties. However, PTFE’s lack of conductivity means that electrons must travel through a very thin catalyst layer, leading to significant voltage drop with distance. To overcome this limitation, the researchers wove a series of conductive copper wires through the very thin sheet of the PTFE.“This work really addressed this challenge, as we can now get both conductivity and hydrophobicity,” Varanasi says.Research on potential carbon conversion systems tends to be done on very small, lab-scale samples, typically less than 1-inch (2.5-centimeter) squares. To demonstrate the potential for scaling up, Varanasi’s team produced a sheet 10 times larger in area and demonstrated its effective performance.To get to that point, they had to do some basic tests that had apparently never been done before, running tests under identical conditions but using electrodes of different sizes to analyze the relationship between conductivity and electrode size. They found that conductivity dropped off dramatically with size, which would mean much more energy, and thus cost, would be needed to drive the reaction.“That’s exactly what we would expect, but it was something that nobody had really dedicatedly investigated before,” Rufer says. In addition, the larger sizes produced more unwanted chemical byproducts besides the intended ethylene.Real-world industrial applications would require electrodes that are perhaps 100 times larger than the lab versions, so adding the conductive wires will be necessary for making such systems practical, the researchers say. They also developed a model which captures the spatial variability in voltage and product distribution on electrodes due to ohmic losses. The model along with the experimental data they collected enabled them to calculate the optimal spacing for conductive wires to counteract the drop off in conductivity.In effect, by weaving the wire through the material, the material is divided into smaller subsections determined by the spacing of the wires. “We split it into a bunch of little subsegments, each of which is effectively a smaller electrode,” Rufer says. “And as we’ve seen, small electrodes can work really well.”Because the copper wire is so much more conductive than the PTFE material, it acts as a kind of superhighway for electrons passing through, bridging the areas where they are confined to the substrate and face greater resistance.To demonstrate that their system is robust, the researchers ran a test electrode for 75 hours continuously, with little change in performance. Overall, Rufer says, their system “is the first PTFE-based electrode which has gone beyond the lab scale on the order of 5 centimeters or smaller. It’s the first work that has progressed into a much larger scale and has done so without sacrificing efficiency.”The weaving process for incorporating the wire can be easily integrated into existing manufacturing processes, even in a large-scale roll-to-roll process, he adds.“Our approach is very powerful because it doesn’t have anything to do with the actual catalyst being used,” Rufer says. “You can sew this micrometric copper wire into any gas diffusion electrode you want, independent of catalyst morphology or chemistry. So, this approach can be used to scale anybody’s electrode.”“Given that we will need to process gigatons of CO2 annually to combat the CO2 challenge, we really need to think about solutions that can scale,” Varanasi says. “Starting with this mindset enables us to identify critical bottlenecks and develop innovative approaches that can make a meaningful impact in solving the problem. Our hierarchically conductive electrode is a result of such thinking.”The research team included MIT graduate students Michael Nitzsche and Sanjay Garimella,  as well as Jack Lake PhD ’23. The work was supported by Shell, through the MIT Energy Initiative. More