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      Advancing the energy transition amidst global crises

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      “The past six years have been the warmest on the planet, and our track record on climate change mitigation is drastically short of what it needs to be,” said Robert C. Armstrong, MIT Energy Initiative (MITEI) director and the Chevron Professor of Chemical Engineering, introducing MITEI’s 15th Annual Research Conference.

      At the symposium, participants from academia, industry, and finance acknowledged the deepening difficulties of decarbonizing a world rocked by geopolitical conflicts and suffering from supply chain disruptions, energy insecurity, inflation, and a persistent pandemic. In spite of this grim backdrop, the conference offered evidence of significant progress in the energy transition. Researchers provided glimpses of a low-carbon future, presenting advances in such areas as long-duration energy storage, carbon capture, and renewable technologies.

      In his keynote remarks, Ernest J. Moniz, the Cecil and Ida Green Professor of Physics and Engineering Systems Emeritus, founding director of MITEI, and former U.S. secretary of energy, highlighted “four areas that have materially changed in the last year” that could shake up, and possibly accelerate, efforts to address climate change.

      Extreme weather seems to be propelling the public and policy makers of both U.S. parties toward “convergence … at least in recognition of the challenge,” Moniz said. He perceives a growing consensus that climate goals will require — in diminishing order of certainty — firm (always-on) power to complement renewable energy sources, a fuel (such as hydrogen) flowing alongside electricity, and removal of atmospheric carbon dioxide (CO2).

      Russia’s invasion of Ukraine, with its “weaponization of natural gas” and global energy impacts, underscores the idea that climate, energy security, and geopolitics “are now more or less recognized widely as one conversation.” Moniz pointed as well to new U.S. laws on climate change and infrastructure that will amplify the role of science and technology and “address the drive to technological dominance by China.”

      The rapid transformation of energy systems will require a comprehensive industrial policy, Moniz said. Government and industry must select and rapidly develop low-carbon fuels, firm power sources (possibly including nuclear power), CO2 removal systems, and long-duration energy storage technologies. “We will need to make progress on all fronts literally in this decade to come close to our goals for climate change mitigation,” he concluded.

      Global cooperation?

      Over two days, conference participants delved into many of the issues Moniz raised. In one of the first panels, scholars pondered whether the international community could forge a coordinated climate change response. The United States’ rift with China, especially over technology trade policies, loomed large.

      “Hatred of China is a bipartisan hobby and passion, but a blanket approach isn’t right, even for the sake of national security,” said Yasheng Huang, the Epoch Foundation Professor of Global Economics and Management at the MIT Sloan School of Management. “Although the United States and China working together would have huge effects for both countries, it is politically unpalatable in the short term,” said F. Taylor Fravel, the Arthur and Ruth Sloan Professor of Political Science and director of the MIT Security Studies Program. John E. Parsons, deputy director for research at the MIT Center for Energy and Environmental Policy Research, suggested that the United States should use this moment “to get our own act together … and start doing things,” such as building nuclear power plants in a cost-effective way.

      Debating carbon removal

      Several panels took up the matter of carbon emissions and the most promising technologies for contending with them. Charles Harvey, MIT professor of civil and environmental engineering, and Howard Herzog, a senior research engineer at MITEI, set the stage early, debating whether capturing carbon was essential to reaching net-zero targets.

      “I have no trouble getting to net zero without carbon capture and storage,” said David Keith, the Gordon McKay Professor of Applied Physics at Harvard University, in a subsequent roundtable. Carbon capture seems more risky to Keith than solar geoengineering, which involves injecting sulfur into the stratosphere to offset CO2 and its heat-trapping impacts.

      There are new ways of moving carbon from where it’s a problem to where it’s safer. Kripa K. Varanasi, MIT professor of mechanical engineering, described a process for modulating the pH of ocean water to remove CO2. Timothy Krysiek, managing director for Equinor Ventures, talked about construction of a 900-kilometer pipeline transporting CO2 from northern Germany to a large-scale storage site located in Norwegian waters 3,000 meters below the seabed. “We can use these offshore Norwegian assets as a giant carbon sink for Europe,” he said.

      A startup showcase featured additional approaches to the carbon challenge. Mantel, which received MITEI Seed Fund money, is developing molten salt material to capture carbon for long-term storage or for use in generating electricity. Verdox has come up with an electrochemical process for capturing dilute CO2 from the atmosphere.

      But while much of the global warming discussion focuses on CO2, other greenhouse gases are menacing. Another panel discussed measuring and mitigating these pollutants. “Methane has 82 times more warming power than CO2 from the point of emission,” said Desirée L. Plata, MIT associate professor of civil and environmental engineering. “Cutting methane is the strongest lever we have to slow climate change in the next 25 years — really the only lever.”

      Steven Hamburg, chief scientist and senior vice president of the Environmental Defense Fund, cautioned that emission of hydrogen molecules into the atmosphere can cause increases in other greenhouse gases such as methane, ozone, and water vapor. As researchers and industry turn to hydrogen as a fuel or as a feedstock for commercial processes, “we will need to minimize leakage … or risk increasing warming,” he said.

      Supply chains, markets, and new energy ventures

      In panels on energy storage and the clean energy supply chain, there were interesting discussions of challenges ahead. High-density energy materials such as lithium, cobalt, nickel, copper, and vanadium for grid-scale energy storage, electric vehicles (EVs), and other clean energy technologies, can be difficult to source. “These often come from water-stressed regions, and we need to be super thoughtful about environmental stresses,” said Elsa Olivetti, the Esther and Harold E. Edgerton Associate Professor in Materials Science and Engineering. She also noted that in light of the explosive growth in demand for metals such as lithium, recycling EVs won’t be of much help. “The amount of material coming back from end-of-life batteries is minor,” she said, until EVs are much further along in their adoption cycle.

      Arvind Sanger, founder and managing partner of Geosphere Capital, said that the United States should be developing its own rare earths and minerals, although gaining the know-how will take time, and overcoming “NIMBYism” (not in my backyard-ism) is a challenge. Sanger emphasized that we must continue to use “denser sources of energy” to catalyze the energy transition over the next decade. In particular, Sanger noted that “for every transition technology, steel is needed,” and steel is made in furnaces that use coal and natural gas. “It’s completely woolly-headed to think we can just go to a zero-fossil fuel future in a hurry,” he said.

      The topic of power markets occupied another panel, which focused on ways to ensure the distribution of reliable and affordable zero-carbon energy. Integrating intermittent resources such as wind and solar into the grid requires a suite of retail markets and new digital tools, said Anuradha Annaswamy, director of MIT’s Active-Adaptive Control Laboratory. Tim Schittekatte, a postdoc at the MIT Sloan School of Management, proposed auctions as a way of insuring consumers against periods of high market costs.

      Another panel described the very different investment needs of new energy startups, such as longer research and development phases. Hooisweng Ow, technology principal at Eni Next LLC Ventures, which is developing drilling technology for geothermal energy, recommends joint development and partnerships to reduce risk. Michael Kearney SM ’11, PhD ’19, SM ’19 is a partner at The Engine, a venture firm built by MIT investing in path-breaking technology to solve the toughest challenges in climate and other problems. Kearney believes the emergence of new technologies and markets will bring on “a labor transition on an order of magnitude never seen before in this country,” he said. “Workforce development is not a natural zone for startups … and this will have to change.”

      Supporting the global South

      The opportunities and challenges of the energy transition look quite different in the developing world. In conversation with Robert Armstrong, Luhut Binsar Pandjaitan, the coordinating minister for maritime affairs and investment of the Republic of Indonesia, reported that his “nation is rich with solar, wind, and energy transition minerals like nickel and copper,” but cannot on its own tackle developing renewable energy or reducing carbon emissions and improving grid infrastructure. “Education is a top priority, and we are very far behind in high technologies,” he said. “We need help and support from MIT to achieve our target,” he said.

      Technologies that could springboard Indonesia and other nations of the global South toward their climate goals are emerging in MITEI-supported projects and at young companies MITEI helped spawn. Among the promising innovations unveiled at the conference are new materials and designs for cooling buildings in hot climates and reducing the environmental costs of construction, and a sponge-like substance that passively sucks moisture out of the air to lower the energy required for running air conditioners in humid climates.

      Other ideas on the move from lab to market have great potential for industrialized nations as well, such as a computational framework for maximizing the energy output of ocean-based wind farms; a process for using ammonia as a renewable fuel with no CO2 emissions; long-duration energy storage derived from the oxidation of iron; and a laser-based method for unlocking geothermal steam to drive power plants. More

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      New process could enable more efficient plastics recycling

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      The accumulation of plastic waste in the oceans, soil, and even in our bodies is one of the major pollution issues of modern times, with over 5 billion tons disposed of so far. Despite major efforts to recycle plastic products, actually making use of that motley mix of materials has remained a challenging issue.

      A key problem is that plastics come in so many different varieties, and chemical processes for breaking them down into a form that can be reused in some way tend to be very specific to each type of plastic. Sorting the hodgepodge of waste material, from soda bottles to detergent jugs to plastic toys, is impractical at large scale. Today, much of the plastic material gathered through recycling programs ends up in landfills anyway. Surely there’s a better way.

      According to new research from MIT and elsewhere, it appears there may indeed be a much better way. A chemical process using a catalyst based on cobalt has been found to be very effective at breaking down a variety of plastics, such as polyethylene (PET) and polypropylene (PP), the two most widely produced forms of plastic, into a single product, propane. Propane can then be used as a fuel for stoves, heaters, and vehicles, or as a feedstock for the production of a wide variety of products — including new plastics, thus potentially providing at least a partial closed-loop recycling system.

      The finding is described today in the open access journal  JACS Au, in a paper by MIT professor of chemical engineering Yuriy Román-Leshkov, postdoc Guido Zichitella, and seven others at MIT, the SLAC National Accelerator Laboratory, and the National Renewable Energy Laboratory.

      Recycling plastics has been a thorny problem, Román-Leshkov explains, because the long-chain molecules in plastics are held together by carbon bonds, which are “very stable and difficult to break apart.” Existing techniques for breaking these bonds tend to produce a random mix of different molecules, which would then require complex refining methods to separate out into usable specific compounds. “The problem is,” he says, “there’s no way to control where in the carbon chain you break the molecule.”

      But to the surprise of the researchers, a catalyst made of a microporous material called a zeolite that contains cobalt nanoparticles can selectively break down various plastic polymer molecules and turn more than 80 percent of them into propane.

      Although zeolites are riddled with tiny pores less than a nanometer wide (corresponding to the width of the polymer chains), a logical assumption had been that there would be little interaction at all between the zeolite and the polymers. Surprisingly, however, the opposite turned out to be the case: Not only do the polymer chains enter the pores, but the synergistic work between cobalt and the acid sites in the zeolite can break the chain at the same point. That cleavage site turned out to correspond to chopping off exactly one propane molecule without generating unwanted methane, leaving the rest of the longer hydrocarbons ready to undergo the process, again and again.

      “Once you have this one compound, propane, you lessen the burden on downstream separations,” Román-Leshkov says. “That’s the essence of why we think this is quite important. We’re not only breaking the bonds, but we’re generating mainly a single product” that can be used for many different products and processes.

      The materials needed for the process, zeolites and cobalt, “are both quite cheap” and widely available, he says, although today most cobalt comes from troubled areas in the Democratic Republic of Congo. Some new production is being developed in Canada, Cuba, and other places. The other material needed for the process is hydrogen, which today is mostly produced from fossil fuels but can easily be made other ways, including electrolysis of water using carbon-free electricity such as solar or wind power.

      The researchers tested their system on a real example of mixed recycled plastic, producing promising results. But more testing will be needed on a greater variety of mixed waste streams to determine how much fouling takes place from various contaminants in the material — such as inks, glues, and labels attached to the plastic containers, or other nonplastic materials that get mixed in with the waste — and how that affects the long-term stability of the process.

      Together with collaborators at NREL, the MIT team is also continuing to study the economics of the system, and analyzing how it can fit into today’s systems for handling plastic and mixed waste streams. “We don’t have all the answers yet,” Román-Leshkov says, but preliminary analysis looks promising.

      The research team included Amani Ebrahim and Simone Bare at the SLAC National Accelerator Laboratory; Jie Zhu, Anna Brenner, Griffin Drake and Julie Rorrer at MIT; and Greg Beckham at the National Renewable Energy Laboratory. The work was supported by the U.S. Department of Energy (DoE), the Swiss National Science Foundation, and the DoE’s Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office (AMO), and Bioenergy Technologies Office (BETO), as part of the the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium. More

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      Cracking the carbon removal challenge

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      By most measures, MIT chemical engineering spinoff Verdox has been enjoying an exceptional year. The carbon capture and removal startup, launched in 2019, announced $80 million in funding in February from a group of investors that included Bill Gates’ Breakthrough Energy Ventures. Then, in April — after recognition as one of the year’s top energy pioneers by Bloomberg New Energy Finance — the company and partner Carbfix won a $1 million XPRIZE Carbon Removal milestone award. This was the first round in the Musk Foundation’s four-year, $100 million-competition, the largest prize offered in history.

      “While our core technology has been validated by the significant improvement of performance metrics, this external recognition further verifies our vision,” says Sahag Voskian SM ’15, PhD ’19, co-founder and chief technology officer at Verdox. “It shows that the path we’ve chosen is the right one.”

      The search for viable carbon capture technologies has intensified in recent years, as scientific models show with increasing certainty that any hope of avoiding catastrophic climate change means limiting CO2 concentrations below 450 parts per million by 2100. Alternative energies will only get humankind so far, and a vast removal of CO2 will be an important tool in the race to remove the gas from the atmosphere.

      Voskian began developing the company’s cost-effective and scalable technology for carbon capture in the lab of T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering at MIT. “It feels exciting to see ideas move from the lab to potential commercial production,” says Hatton, a co-founder of the company and scientific advisor, adding that Verdox has speedily overcome the initial technical hiccups encountered by many early phase companies. “This recognition enhances the credibility of what we’re doing, and really validates our approach.”

      At the heart of this approach is technology Voskian describes as “elegant and efficient.” Most attempts to grab carbon from an exhaust flow or from air itself require a great deal of energy. Voskian and Hatton came up with a design whose electrochemistry makes carbon capture appear nearly effortless. Their invention is a kind of battery: conductive electrodes coated with a compound called polyanthraquinone, which has a natural chemical attraction to carbon dioxide under certain conditions, and no affinity for CO2 when these conditions are relaxed. When activated by a low-level electrical current, the battery charges, reacting with passing molecules of CO2 and pulling them onto its surface. Once the battery becomes saturated, the CO2 can be released with a flip of voltage as a pure gas stream.

      “We showed that our technology works in a wide range of CO2 concentrations, from the 20 percent or higher found in cement and steel industry exhaust streams, down to the very diffuse 0.04 percent in air itself,” says Hatton. Climate change science suggests that removing CO2 directly from air “is an important component of the whole mitigation strategy,” he adds.

      “This was an academic breakthrough,” says Brian Baynes PhD ’04, CEO and co-founder of Verdox. Baynes, a chemical engineering alumnus and a former associate of Hatton’s, has many startups to his name, and a history as a venture capitalist and mentor to young entrepreneurs. When he first encountered Hatton and Voskian’s research in 2018, he was “impressed that their technology showed it could reduce energy consumption for certain kinds of carbon capture by 70 percent compared to other technologies,” he says. “I was encouraged and impressed by this low-energy footprint, and recommended that they start a company.”

      Neither Hatton nor Voskian had commercialized a product before, so they asked Baynes to help them get going. “I normally decline these requests, because the costs are generally greater than the upside,” Baynes says. “But this innovation had the potential to move the needle on climate change, and I saw it as a rare opportunity.”

      The Verdox team has no illusions about the challenge ahead. “The scale of the problem is enormous,” says Voskian. “Our technology must be in a position to capture mega- and gigatons of CO2 from air and emission sources.” Indeed, the International Panel on Climate Change estimates the world must remove 10 gigatons of CO2 per year by 2050 in order to keep global temperature rise under 2 degrees Celsius.

      To scale up successfully and at a pace that could meet the world’s climate challenge, Verdox must become “a business that works in a technoeconomic sense,” as Baynes puts it. This means, for instance, ensuring its carbon capture system offers clear and competitive cost benefits when deployed. Not a problem, says Voskian: “Our technology, because it uses electric energy, can be easily integrated into the grid, working with solar and wind on a plug-and-play basis.” The Verdox team believes their carbon footprint will beat that of competitors by orders of magnitude.

      The company is pushing past a series of technical obstacles as it ramps up: enabling the carbon capture battery to run hundreds of thousands of cycles before its performance wanes, and enhancing the polyanthraquinone chemistry so that the device is even more selective for CO2.

      After hurtling past critical milestones, Verdox is now working with its first announced commercial client: Norwegian aluminum company Hydro, which aims to eliminate CO2 from the exhaust of its smelters as it transitions to zero-carbon production.

      Verdox is also developing systems that can efficiently pull CO2 out of ambient air. “We’re designing units that would look like rows and rows of big fans that bring the air into boxes containing our batteries,” he says. Such approaches might prove especially useful in locations such as airfields, where there are higher-than-normal concentrations of CO2 emissions present.

      All this captured carbon needs to go somewhere. With XPRIZE partner Carbfix, which has a decade-old, proven method for mineralizing captured CO2 and depositing it in deep underground caverns, Verdox will have a final resting place for CO2 that cannot immediately be reused for industrial applications such as new fuels or construction materials.

      With its clients and partners, the team appears well-positioned for the next round of the carbon removal XPRIZE competition, which will award up to $50 million to the group that best demonstrates a working solution at a scale of at least 1,000 tons removed per year, and can present a viable blueprint for scaling to gigatons of removal per year.

      Can Verdox meaningfully reduce the planet’s growing CO2 burden? Voskian is sure of it. “Going at our current momentum, and seeing the world embrace carbon capture, this is the right path forward,” he says. “With our partners, deploying manufacturing facilities on a global scale, we will make a dent in the problem in our lifetime.” More

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      J-WAFS awards $150K Solutions grant to Patrick Doyle and team for rapid removal of micropollutants from water

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      The Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) has awarded a 2022 J-WAFS Solutions grant to Patrick S. Doyle, the Robert T. Haslam Professor of Chemical Engineering at MIT, for his innovative system to tackle water pollution. Doyle will be working with co-Principal Investigator Rafael Gomez-Bombarelli, assistant professor in materials processing in the Department of Materials Science, as well as PhD students Devashish Gokhale and Tynan Perez. Building off of findings from a 2019 J-WAFS seed grant, Doyle and the research team will create cost-effective industry-scale processes to remove micropollutants from water. Project work will commence this month.

      The J-WAFS Solutions program provides one-year, renewable, commercialization grants to help move MIT technology from the laboratory to market. Grants of up to $150,000 are awarded to researchers with breakthrough technologies and inventions in water or food. Since its launch in 2015, J-WAFS Solutions grants have led to seven spinout companies and helped commercialize two products as open-source technologies. The grant program is supported by Community Jameel.

      A widespread problem 

      Micropollutants are contaminants that occur in low concentrations in the environment, yet continuous exposure and bioaccumulation of micropollutants make them a cause for concern. According to the U.S. Environmental Protection Agency, the plastics derivative Bisphenol A (BPA), the “forever chemicals” per-and polyfluoroalkyl substances (PFAS), and heavy metals like lead are common micropollutants known to be found in more than 85 percent of rivers, ponds, and lakes in the United States. Many of these bodies of water are sources of drinking water. Over long periods of time, exposure to micropollutants through drinking water can cause physiological damage in humans, increasing the risk of cancer, developmental disorders, and reproductive failure.

      Since micropollutants occur in low concentrations, it is difficult to detect and monitor their presence, and the chemical diversity of micropollutants makes it difficult to inexpensively remove them from water. Currently, activated carbon is the industry standard for micropollutant elimination, but this method cannot efficiently remove contaminants at parts-per-billion and parts-per-trillion concentrations. There are also strong sustainability concerns associated with activated carbon production, which is energy-intensive and releases large volumes of carbon dioxide.

      A solution with societal and economic benefits

      Doyle and his team are developing a technology that uses sustainable hydrogel microparticles to remove micropollutants from water. The polymeric hydrogel microparticles use chemically anchored structures including micelles and other chelating agents that act like a sponge by absorbing organic micropollutants and heavy metal ions. The microparticles are large enough to separate from water using simple gravitational settling. The system is sustainable because the microparticles can be recycled for continuous use. In testing, the long-lasting, reusable microparticles show quicker removal of contaminants than commercial activated carbon. The researchers plan to utilize machine learning to find optimal microparticle compositions that maximize performance on complex combinations of micropollutants in simulated and real wastewater samples.

      Economically, the technology is a new offering that has applications in numerous large markets where micropollutant elimination is vital, including municipal and industrial water treatment equipment, as well as household water purification systems. The J-WAFS Solutions grant will allow the team to build and test prototypes of the water treatment system, identify the best use cases and customers, and perform technoeconomic analyses and market research to formulate a preliminary business plan. With J-WAFS commercialization support, the project could eventually lead to a startup company.

      “Emerging micropollutants are a growing threat to drinking water supplies worldwide,” says J-WAFS Director John H. Lienhard, the Abdul Latif Jameel Professor of Water at MIT. “Cost-effective and scalable technologies for micropollutant removal are urgently needed. This project will develop and commercialize a promising new tool for water treatment, with the goal of improving water quality for millions of people.” More

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      Turning carbon dioxide into valuable products

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      Carbon dioxide (CO2) is a major contributor to climate change and a significant product of many human activities, notably industrial manufacturing. A major goal in the energy field has been to chemically convert emitted CO2 into valuable chemicals or fuels. But while CO2 is available in abundance, it has not yet been widely used to generate value-added products. Why not?

      The reason is that CO2 molecules are highly stable and therefore not prone to being chemically converted to a different form. Researchers have sought materials and device designs that could help spur that conversion, but nothing has worked well enough to yield an efficient, cost-effective system.

      Two years ago, Ariel Furst, the Raymond (1921) and Helen St. Laurent Career Development Professor of Chemical Engineering at MIT, decided to try using something different — a material that gets more attention in discussions of biology than of chemical engineering. Already, results from work in her lab suggest that her unusual approach is paying off.

      The stumbling block

      The challenge begins with the first step in the CO2 conversion process. Before being transformed into a useful product, CO2 must be chemically converted into carbon monoxide (CO). That conversion can be encouraged using electrochemistry, a process in which input voltage provides the extra energy needed to make the stable CO2 molecules react. The problem is that achieving the CO2-to-CO conversion requires large energy inputs — and even then, CO makes up only a small fraction of the products that are formed.

      To explore opportunities for improving this process, Furst and her research group focused on the electrocatalyst, a material that enhances the rate of a chemical reaction without being consumed in the process. The catalyst is key to successful operation. Inside an electrochemical device, the catalyst is often suspended in an aqueous (water-based) solution. When an electric potential (essentially a voltage) is applied to a submerged electrode, dissolved CO2 will — helped by the catalyst — be converted to CO.

      But there’s one stumbling block: The catalyst and the CO2 must meet on the surface of the electrode for the reaction to occur. In some studies, the catalyst is dispersed in the solution, but that approach requires more catalyst and isn’t very efficient, according to Furst. “You have to both wait for the diffusion of CO2 to the catalyst and for the catalyst to reach the electrode before the reaction can occur,” she explains. As a result, researchers worldwide have been exploring different methods of “immobilizing” the catalyst on the electrode.

      Connecting the catalyst and the electrode

      Before Furst could delve into that challenge, she needed to decide which of the two types of CO2 conversion catalysts to work with: the traditional solid-state catalyst or a catalyst made up of small molecules. In examining the literature, she concluded that small-molecule catalysts held the most promise. While their conversion efficiency tends to be lower than that of solid-state versions, molecular catalysts offer one important advantage: They can be tuned to emphasize reactions and products of interest.

      Two approaches are commonly used to immobilize small-molecule catalysts on an electrode. One involves linking the catalyst to the electrode by strong covalent bonds — a type of bond in which atoms share electrons; the result is a strong, essentially permanent connection. The other sets up a non-covalent attachment between the catalyst and the electrode; unlike a covalent bond, this connection can easily be broken.

      Neither approach is ideal. In the former case, the catalyst and electrode are firmly attached, ensuring efficient reactions; but when the activity of the catalyst degrades over time (which it will), the electrode can no longer be accessed. In the latter case, a degraded catalyst can be removed; but the exact placement of the small molecules of the catalyst on the electrode can’t be controlled, leading to an inconsistent, often decreasing, catalytic efficiency — and simply increasing the amount of catalyst on the electrode surface without concern for where the molecules are placed doesn’t solve the problem.

      What was needed was a way to position the small-molecule catalyst firmly and accurately on the electrode and then release it when it degrades. For that task, Furst turned to what she and her team regard as a kind of “programmable molecular Velcro”: deoxyribonucleic acid, or DNA.

      Adding DNA to the mix

      Mention DNA to most people, and they think of biological functions in living things. But the members of Furst’s lab view DNA as more than just genetic code. “DNA has these really cool physical properties as a biomaterial that people don’t often think about,” she says. “DNA can be used as a molecular Velcro that can stick things together with very high precision.”

      Furst knew that DNA sequences had previously been used to immobilize molecules on surfaces for other purposes. So she devised a plan to use DNA to direct the immobilization of catalysts for CO2 conversion.

      Her approach depends on a well-understood behavior of DNA called hybridization. The familiar DNA structure is a double helix that forms when two complementary strands connect. When the sequence of bases (the four building blocks of DNA) in the individual strands match up, hydrogen bonds form between complementary bases, firmly linking the strands together.

      Using that behavior for catalyst immobilization involves two steps. First, the researchers attach a single strand of DNA to the electrode. Then they attach a complementary strand to the catalyst that is floating in the aqueous solution. When the latter strand gets near the former, the two strands hybridize; they become linked by multiple hydrogen bonds between properly paired bases. As a result, the catalyst is firmly affixed to the electrode by means of two interlocked, self-assembled DNA strands, one connected to the electrode and the other to the catalyst.

      Better still, the two strands can be detached from one another. “The connection is stable, but if we heat it up, we can remove the secondary strand that has the catalyst on it,” says Furst. “So we can de-hybridize it. That allows us to recycle our electrode surfaces — without having to disassemble the device or do any harsh chemical steps.”

      Experimental investigation

      To explore that idea, Furst and her team — postdocs Gang Fan and Thomas Gill, former graduate student Nathan Corbin PhD ’21, and former postdoc Amruta Karbelkar — performed a series of experiments using three small-molecule catalysts based on porphyrins, a group of compounds that are biologically important for processes ranging from enzyme activity to oxygen transport. Two of the catalysts involve a synthetic porphyrin plus a metal center of either cobalt or iron. The third catalyst is hemin, a natural porphyrin compound used to treat porphyria, a set of disorders that can affect the nervous system. “So even the small-molecule catalysts we chose are kind of inspired by nature,” comments Furst.

      In their experiments, the researchers first needed to modify single strands of DNA and deposit them on one of the electrodes submerged in the solution inside their electrochemical cell. Though this sounds straightforward, it did require some new chemistry. Led by Karbelkar and third-year undergraduate researcher Rachel Ahlmark, the team developed a fast, easy way to attach DNA to electrodes. For this work, the researchers’ focus was on attaching DNA, but the “tethering” chemistry they developed can also be used to attach enzymes (protein catalysts), and Furst believes it will be highly useful as a general strategy for modifying carbon electrodes.

      Once the single strands of DNA were deposited on the electrode, the researchers synthesized complementary strands and attached to them one of the three catalysts. When the DNA strands with the catalyst were added to the solution in the electrochemical cell, they readily hybridized with the DNA strands on the electrode. After half-an-hour, the researchers applied a voltage to the electrode to chemically convert CO2 dissolved in the solution and used a gas chromatograph to analyze the makeup of the gases produced by the conversion.

      The team found that when the DNA-linked catalysts were freely dispersed in the solution, they were highly soluble — even when they included small-molecule catalysts that don’t dissolve in water on their own. Indeed, while porphyrin-based catalysts in solution often stick together, once the DNA strands were attached, that counterproductive behavior was no longer evident.

      The DNA-linked catalysts in solution were also more stable than their unmodified counterparts. They didn’t degrade at voltages that caused the unmodified catalysts to degrade. “So just attaching that single strand of DNA to the catalyst in solution makes those catalysts more stable,” says Furst. “We don’t even have to put them on the electrode surface to see improved stability.” When converting CO2 in this way, a stable catalyst will give a steady current over time. Experimental results showed that adding the DNA prevented the catalyst from degrading at voltages of interest for practical devices. Moreover, with all three catalysts in solution, the DNA modification significantly increased the production of CO per minute.

      Allowing the DNA-linked catalyst to hybridize with the DNA connected to the electrode brought further improvements, even compared to the same DNA-linked catalyst in solution. For example, as a result of the DNA-directed assembly, the catalyst ended up firmly attached to the electrode, and the catalyst stability was further enhanced. Despite being highly soluble in aqueous solutions, the DNA-linked catalyst molecules remained hybridized at the surface of the electrode, even under harsh experimental conditions.

      Immobilizing the DNA-linked catalyst on the electrode also significantly increased the rate of CO production. In a series of experiments, the researchers monitored the CO production rate with each of their catalysts in solution without attached DNA strands — the conventional setup — and then with them immobilized by DNA on the electrode. With all three catalysts, the amount of CO generated per minute was far higher when the DNA-linked catalyst was immobilized on the electrode.

      In addition, immobilizing the DNA-linked catalyst on the electrode greatly increased the “selectivity” in terms of the products. One persistent challenge in using CO2 to generate CO in aqueous solutions is that there is an inevitable competition between the formation of CO and the formation of hydrogen. That tendency was eased by adding DNA to the catalyst in solution — and even more so when the catalyst was immobilized on the electrode using DNA. For both the cobalt-porphyrin catalyst and the hemin-based catalyst, the formation of CO relative to hydrogen was significantly higher with the DNA-linked catalyst on the electrode than in solution. With the iron-porphyrin catalyst they were about the same. “With the iron, it doesn’t matter whether it’s in solution or on the electrode,” Furst explains. “Both of them have selectivity for CO, so that’s good, too.”

      Progress and plans

      Furst and her team have now demonstrated that their DNA-based approach combines the advantages of the traditional solid-state catalysts and the newer small-molecule ones. In their experiments, they achieved the highly efficient chemical conversion of CO2 to CO and also were able to control the mix of products formed. And they believe that their technique should prove scalable: DNA is inexpensive and widely available, and the amount of catalyst required is several orders of magnitude lower when it’s immobilized using DNA.

      Based on her work thus far, Furst hypothesizes that the structure and spacing of the small molecules on the electrode may directly impact both catalytic efficiency and product selectivity. Using DNA to control the precise positioning of her small-molecule catalysts, she plans to evaluate those impacts and then extrapolate design parameters that can be applied to other classes of energy-conversion catalysts. Ultimately, she hopes to develop a predictive algorithm that researchers can use as they design electrocatalytic systems for a wide variety of applications.

      This research was supported by a grant from the MIT Energy Initiative Seed Fund.

      This article appears in the Spring 2022 issue of Energy Futures, the magazine of the MIT Energy Initiative. More

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      in Energy

      Making hydropower plants more sustainable

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      Growing up on a farm in Texas, there was always something for siblings Gia Schneider ’99 and Abe Schneider ’02, SM ’03 to do. But every Saturday at 2 p.m., no matter what, the family would go down to a local creek to fish, build rock dams and rope swings, and enjoy nature.

      Eventually the family began going to a remote river in Colorado each summer. The river forked in two; one side was managed by ranchers who destroyed natural features like beaver dams, while the other side remained untouched. The family noticed the fishing was better on the preserved side, which led Abe to try measuring the health of the two river ecosystems. In high school, he co-authored a study showing there were more beneficial insects in the bed of the river with the beaver dams.

      The experience taught both siblings a lesson that has stuck. Today they are the co-founders of Natel Energy, a company attempting to mimic natural river ecosystems with hydropower systems that are more sustainable than conventional hydro plants.

      “The big takeaway for us, and what we’ve been doing all this time, is thinking of ways that infrastructure can help increase the health of our environment — and beaver dams are a good example of infrastructure that wouldn’t otherwise be there that supports other populations of animals,” Abe says. “It’s a motivator for the idea that hydropower can help improve the environment rather than destroy the environment.”

      Through new, fish-safe turbines and other features designed to mimic natural river conditions, the founders say their plants can bridge the gap between power-plant efficiency and environmental sustainability. By retrofitting existing hydropower plants and developing new projects, the founders believe they can supercharge a hydropower industry that is by far the largest source of renewable electricity in the world but has not grown in energy generation as much as wind and solar in recent years.

      “Hydropower plants are built today with only power output in mind, as opposed to the idea that if we want to unlock growth, we have to solve for both efficiency and river sustainability,” Gia says.

      A life’s mission

      The origins of Natel came not from a single event but from a lifetime of events. Abe and Gia’s father was an inventor and renewable energy enthusiast who designed and built the log cabin they grew up in. With no television, the kids’ preferred entertainment was reading books or being outside. The water in their house was pumped by power generated using a mechanical windmill on the north side of the house.

      “We grew up hanging clothes on a line, and it wasn’t because we were too poor to own a dryer, but because everything about our existence and our use of energy was driven by the idea that we needed to make conscious decisions about sustainability,” Abe says.

      One of the things that fascinated both siblings was hydropower. In high school, Abe recalls bugging his friend who was good at math to help him with designs for new hydro turbines.

      Both siblings admit coming to MIT was a major culture shock, but they loved the atmosphere of problem solving and entrepreneurship that permeated the campus. Gia came to MIT in 1995 and majored in chemical engineering while Abe followed three years later and majored in mechanical engineering for both his bachelor’s and master’s degrees.

      All the while, they never lost sight of hydropower. In the 1998 MIT $100K Entrepreneurship Competitions (which was the $50K at the time), they pitched an idea for hydropower plants based on a linear turbine design. They were named finalists in the competition, but still wanted more industry experience before starting a company. After graduation, Abe worked as a mechanical engineer and did some consulting work with the operators of small hydropower plants while Gia worked at the energy desks of a few large finance companies.

      In 2009, the siblings, along with their late father, Daniel, received a small business grant of $200,000 and formally launched Natel Energy.

      Between 2009 and 2019, the founders worked on a linear turbine design that Abe describes as turbines on a conveyor belt. They patented and deployed the system on a few sites, but the problem of ensuring safe fish passage remained.

      Then the founders were doing some modeling that suggested they could achieve high power plant efficiency using an extremely rounded edge on a turbine blade — as opposed to the sharp blades typically used for hydropower turbines. The insight made them realize if they didn’t need sharp blades, perhaps they didn’t need a complex new turbine.

      “It’s so counterintuitive, but we said maybe we can achieve the same results with a propeller turbine, which is the most common kind,” Abe says. “It started out as a joke — or a challenge — and I did some modeling and rapidly realized, ‘Holy cow, this actually could work!’ Instead of having a powertrain with a decade’s worth of complexity, you have a powertrain that has one moving part, and almost no change in loading, in a form factor that the whole industry is used to.”

      The turbine Natel developed features thick blades that allow more than 99 percent of fish to pass through safely, according to third-party tests. Natel’s turbines also allow for the passage of important river sediment and can be coupled with structures that mimic natural features of rivers like log jams, beaver dams, and rock arches.

      “We want the most efficient machine possible, but we also want the most fish-safe machine possible, and that intersection has led to our unique intellectual property,” Gia says.

      Supercharging hydropower

      Natel has already installed two versions of its latest turbine, what it calls the Restoration Hydro Turbine, at existing plants in Maine and Oregon. The company hopes that by the end of this year, two more will be deployed, including one in Europe, a key market for Natel because of its stronger environmental regulations for hydropower plants.

      Since their installation, the founders say the first two turbines have converted more than 90 percent of the energy available in the water into energy at the turbine, a comparable efficiency to conventional turbines.

      Looking forward, Natel believes its systems have a significant role to play in boosting the hydropower industry, which is facing increasing scrutiny and environmental regulation that could otherwise close down many existing plants. For example, the founders say that hydropower plants the company could potentially retrofit across the U.S. and Europe have a total capacity of about 30 gigawatts, enough to power millions of homes.

      Natel also has ambitions to build entirely new plants on the many nonpowered dams around the U.S. and Europe. (Currently only 3 percent of the United States’ 80,000 dams are powered.) The founders estimate their systems could generate about 48 gigawatts of new electricity across the U.S. and Europe — the equivalent of more than 100 million solar panels.

      “We’re looking at numbers that are pretty meaningful,” Gia says. “We could substantially add to the existing installed base while also modernizing the existing base to continue to be productive while meeting modern environmental requirements.”

      Overall, the founders see hydropower as a key technology in our transition to sustainable energy, a sentiment echoed by recent MIT research.

      “Hydro today supplies the bulk of electricity reliability services in a lot of these areas — things like voltage regulation, frequency regulation, storage,” Gia says. “That’s key to understand: As we transition to a zero-carbon grid, we need a reliable grid, and hydro has a very important role in supporting that. Particularly as we think about making this transition as quickly as we can, we’re going to need every bit of zero-emission resources we can get.” More

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      in Environment

      Four researchers with MIT ties earn Schmidt Science Fellowships

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      Four researchers with MIT ties — Juncal Arbelaiz, Xiangkun (Elvis) Cao, Sandya Subramanian, and Heather Zlotnick ’17 — have been honored with competitive Schmidt Science Fellowships.

      Created in 2017, the fellows program aims to bring together the world’s brightest minds “to solve society’s toughest challenges.”

      The four MIT-affiliated researchers are among 29 Schmidt Science Fellows from around the world who will receive postdoctoral support for either one or two years with an annual stipend of $100,000, along with individualized mentoring and participation in the program’s Global Meeting Series. The fellows will also have opportunities to engage with thought-leaders from science, business, policy, and society. According to the award announcement, the fellows are expected to pursue research that shifts from the focus of their PhDs, to help expand and enhance their futures as scientific leaders.

      Juncal Arbelaiz is a PhD candidate in applied mathematics at MIT, who is completing her doctorate this summer. Her doctoral research at MIT is advised by Ali Jadbabaie, the JR East Professor of Engineering and head of the Department of Civil and Environmental Engineering; Anette Hosoi, the Neil and Jane Pappalardo Professor of Mechanical Engineering and associate dean of the School of Engineering; and Bassam Bamieh, professor of mechanical engineering and associate director of the Center for Control, Dynamical Systems, and Computation at the University of California at Santa Barbara. Arbelaiz’s research revolves around the design of optimal decentralized intelligence for spatially-distributed dynamical systems.

      “I cannot think of a better way to start my independent scientific career. I feel very excited and grateful for this opportunity,” says Arbelaiz. With her fellowship, she will enlist systems biology to explore how the nervous system encodes and processes sensory information to address future safety-critical artificial intelligence applications. “The Schmidt Science Fellowship will provide me with a unique opportunity to work at the intersection of biological and machine intelligence for two years and will be a steppingstone towards my longer-term objective of becoming a researcher in bio-inspired machine intelligence,” she says.

      Xiangkun (Elvis) Cao is currently a postdoc in the lab of T. Alan Hatton, the Ralph Landau Professor in Chemical Engineering, and an Impact Fellow at the MIT Climate and Sustainability Consortium. Cao received his PhD in mechanical engineering from Cornell University in 2021, during which he focused on microscopic precision in the simultaneous delivery of light and fluids by optofluidics, with advances relevant to health and sustainability applications. As a Schmidt Science Fellow, he plans to be co-advised by Hatton on carbon capture, and Ted Sargent, professor of chemistry at Northwestern University, on carbon utilization. Cao is passionate about integrated carbon capture and utilization (CCU) from molecular to process levels, machine learning to inspire smart CCU, and the nexus of technology, business, and policy for CCU.

      “The Schmidt Science Fellowship provides the perfect opportunity for me to work across disciplines to study integrated carbon capture and utilization from molecular to process levels,” Cao explains. “My vision is that by integrating carbon capture and utilization, we can concurrently make scientific discoveries and unlock economic opportunities while mitigating global climate change. This way, we can turn our carbon liability into an asset.”

      Sandya Subramanian, a 2021 PhD graduate of the Harvard-MIT Program in Health Sciences and Technology (HST) in the area of medical engineering and medical physics, is currently a postdoc at Stanford Data Science. She is focused on the topics of biomedical engineering, statistics, machine learning, neuroscience, and health care. Her research is on developing new technologies and methods to study the interactions between the brain, the autonomic nervous system, and the gut. “I’m extremely honored to receive the Schmidt Science Fellowship and to join the Schmidt community of leaders and scholars,” says Subramanian. “I’ve heard so much about the fellowship and the fact that it can open doors and give people confidence to pursue challenging or unique paths.”

      According to Subramanian, the autonomic nervous system and its interactions with other body systems are poorly understood but thought to be involved in several disorders, such as functional gastrointestinal disorders, Parkinson’s disease, diabetes, migraines, and eating disorders. The goal of her research is to improve our ability to monitor and quantify these physiologic processes. “I’m really interested in understanding how we can use physiological monitoring technologies to inform clinical decision-making, especially around the autonomic nervous system, and I look forward to continuing the work that I’ve recently started at Stanford as Schmidt Science Fellow,” she says. “A huge thank you to all of the mentors, colleagues, friends, and leaders I had the pleasure of meeting and working with at HST and MIT; I couldn’t have done this without everything I learned there.”

      Hannah Zlotnick ’17 attended MIT for her undergraduate studies, majoring in biological engineering with a minor in mechanical engineering. At MIT, Zlotnick was a student-athlete on the women’s varsity soccer team, a UROP student in Alan Grodzinsky’s laboratory, and a member of Pi Beta Phi. For her PhD, Zlotnick attended the University of Pennsylvania, and worked in Robert Mauck’s laboratory within the departments of Bioengineering and Orthopaedic Surgery.

      Zlotnick’s PhD research focused on harnessing remote forces, such as magnetism or gravity, to enhance engineered cartilage and osteochondral repair both in vitro and in large animal models. Zlotnick now plans to pivot to the field of biofabrication to create tissue models of the knee joint to assess potential therapeutics for osteoarthritis. “I am humbled to be a part of the Schmidt Science Fellows community, and excited to venture into the field of biofabrication,” Zlotnick says. “Hopefully this work uncovers new therapies for patients with inflammatory joint diseases.” More

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      in Environment

      Study finds natural sources of air pollution exceed air quality guidelines in many regions

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      Alongside climate change, air pollution is one of the biggest environmental threats to human health. Tiny particles known as particulate matter or PM2.5 (named for their diameter of just 2.5 micrometers or less) are a particularly hazardous type of pollutant. These particles are produced from a variety of sources, including wildfires and the burning of fossil fuels, and can enter our bloodstream, travel deep into our lungs, and cause respiratory and cardiovascular damage. Exposure to particulate matter is responsible for millions of premature deaths globally every year.

      In response to the increasing body of evidence on the detrimental effects of PM2.5, the World Health Organization (WHO) recently updated its air quality guidelines, lowering its recommended annual PM2.5 exposure guideline by 50 percent, from 10 micrograms per meter cubed (μm3) to 5 μm3. These updated guidelines signify an aggressive attempt to promote the regulation and reduction of anthropogenic emissions in order to improve global air quality.

      A new study by researchers in the MIT Department of Civil and Environmental Engineering explores if the updated air quality guideline of 5 μm3 is realistically attainable across different regions of the world, particularly if anthropogenic emissions are aggressively reduced. 

      The first question the researchers wanted to investigate was to what degree moving to a no-fossil-fuel future would help different regions meet this new air quality guideline.

      “The answer we found is that eliminating fossil-fuel emissions would improve air quality around the world, but while this would help some regions come into compliance with the WHO guidelines, for many other regions high contributions from natural sources would impede their ability to meet that target,” says senior author Colette Heald, the Germeshausen Professor in the MIT departments of Civil and Environmental Engineering, and Earth, Atmospheric and Planetary Sciences. 

      The study by Heald, Professor Jesse Kroll, and graduate students Sidhant Pai and Therese Carter, published June 6 in the journal Environmental Science and Technology Letters, finds that over 90 percent of the global population is currently exposed to average annual concentrations that are higher than the recommended guideline. The authors go on to demonstrate that over 50 percent of the world’s population would still be exposed to PM2.5 concentrations that exceed the new air quality guidelines, even in the absence of all anthropogenic emissions.

      This is due to the large natural sources of particulate matter — dust, sea salt, and organics from vegetation — that still exist in the atmosphere when anthropogenic emissions are removed from the air. 

      “If you live in parts of India or northern Africa that are exposed to large amounts of fine dust, it can be challenging to reduce PM2.5 exposures below the new guideline,” says Sidhant Pai, co-lead author and graduate student. “This study challenges us to rethink the value of different emissions abatement controls across different regions and suggests the need for a new generation of air quality metrics that can enable targeted decision-making.”

      The researchers conducted a series of model simulations to explore the viability of achieving the updated PM2.5 guidelines worldwide under different emissions reduction scenarios, using 2019 as a representative baseline year. 

      Their model simulations used a suite of different anthropogenic sources that could be turned on and off to study the contribution of a particular source. For instance, the researchers conducted a simulation that turned off all human-based emissions in order to determine the amount of PM2.5 pollution that could be attributed to natural and fire sources. By analyzing the chemical composition of the PM2.5 aerosol in the atmosphere (e.g., dust, sulfate, and black carbon), the researchers were also able to get a more accurate understanding of the most important PM2.5 sources in a particular region. For example, elevated PM2.5 concentrations in the Amazon were shown to predominantly consist of carbon-containing aerosols from sources like deforestation fires. Conversely, nitrogen-containing aerosols were prominent in Northern Europe, with large contributions from vehicles and fertilizer usage. The two regions would thus require very different policies and methods to improve their air quality. 

      “Analyzing particulate pollution across individual chemical species allows for mitigation and adaptation decisions that are specific to the region, as opposed to a one-size-fits-all approach, which can be challenging to execute without an understanding of the underlying importance of different sources,” says Pai. 

      When the WHO air quality guidelines were last updated in 2005, they had a significant impact on environmental policies. Scientists could look at an area that was not in compliance and suggest high-level solutions to improve the region’s air quality. But as the guidelines have tightened, globally-applicable solutions to manage and improve air quality are no longer as evident. 

      “Another benefit of speciating is that some of the particles have different toxicity properties that are correlated to health outcomes,” says Therese Carter, co-lead author and graduate student. “It’s an important area of research that this work can help motivate. Being able to separate out that piece of the puzzle can provide epidemiologists with more insights on the different toxicity levels and the impact of specific particles on human health.”

      The authors view these new findings as an opportunity to expand and iterate on the current guidelines.  

      “Routine and global measurements of the chemical composition of PM2.5 would give policymakers information on what interventions would most effectively improve air quality in any given location,” says Jesse Kroll, a professor in the MIT departments of Civil and Environmental Engineering and Chemical Engineering. “But it would also provide us with new insights into how different chemical species in PM2.5 affect human health.”

      “I hope that as we learn more about the health impacts of these different particles, our work and that of the broader atmospheric chemistry community can help inform strategies to reduce the pollutants that are most harmful to human health,” adds Heald. More