ILLUSTRATION BY JAMES WEINBERG
That’s why the work at MIT matters so much. Here’s a look at just a few of the scores of ways MIT’s engineers are addressing the urgent challenges of climate change and sustainability.
Air Transportation
Project: Using gas turbines in airplanes to generate electrical power for electric motors and running resulting emissions from the engines through a catalyst to remove air pollutants.
Key researcher: Steven Barrett, Professor of Aeronautics and Astronautics
Roughly 16,000 deaths annually can be attributed to the impaired air quality created by global aviation emissions of nitrogen oxides (NOx) and other emissions. MIT researchers have proposed a new airplane design to all but eliminate such emissions.
The new hybrid-electric or “turbo-electric” design borrows the concept from emissions-control systems used in ground-transportation vehicles, which employ post-combustion emissions controls. To date, such technology has not been used on planes because it interferes with the operation of jet engines. The MIT design would move the plane’s gas-powered turbines from the wings into the cargo hold, where they would drive a generator to produce electricity. The plane would then use electrically powered, wing-mounted propellers or fans to fly.
Transitioning to this new form of airplane propulsion would pose significant technical challenges but could eliminate an estimated 95% of aviation’s NOx emissions, reducing the number of associated early deaths by 92%.
“Ultimately we need to get to a zero-impact aviation sector—or as close to zero as we can get,” Barrett says. “For the air pollution part of the problem, this provides a potential path forward, and it’s one that can be combined with climate-related solutions such as sustainable aviation fuels.”
Circular Economy
Project: Illuminating the importance of identifying the grade and source of paper used in recycling to evaluate the environmental effects of substituting primary materials with recycled materials.
Key researcher: Elsa Olivetti PhD ’07, Esther and Harold E. Edgerton Associate Professor in Materials Science and Engineering
Recycling is a popular strategy for addressing the environmental burden associated with resource use. However, substituting primary materials with recycled materials can have unexpected downsides. To understand all the system-wide effects, researchers at MIT have developed analytical models that reflect the resource consumption behaviors of material producers and the resulting cascade of material flows. Through this work, they have found, for example, that the environmental benefits of paper recycling vary widely by paper source. Also, they report that certain environmentally protective policies might actually increase CO2 emissions.
This work promises to improve the environmental and economic sustainability of materials by providing data that are crucial to supporting the “circular economy,” one in which waste is minimized through reuse, refurbishment, and remanufacturing.
“We are excited that our research can help provide the context in which environmental benefit can be designed for in materials, processes, and systems,” Olivetti says.
Sustainable Energy Storage
Project: Designing a battery capable of storing renewable energy by splitting water into hydrogen and oxygen; the hydrogen becomes an energy carrier and can be stored for later use in a fuel cell.
Key researcher: Yang Shao-Horn, Professor of Mechanical Engineering
Developing cost-effective ways to store energy that would allow the use of low-cost electricity from renewables is a critical step to meeting the world’s energy needs at scale and on demand sustainably, which is key to addressing global climate change. At MIT, researchers are designing a device capable of storing renewable energy using an abundant resource: liquid water.
Using catalysts, electricity can be stored by splitting water to make hydrogen and oxygen through a series of chemical reactions; the hydrogen becomes an energy carrier that can be stored for later use. To convert the energy stored in the hydrogen back into electricity, the reactions are reversed in devices such as fuel cells.
MIT researchers are using supramolecular chemistry and machine-learning methods to design and discover new catalysts and new catalyst design rules to drive these reactions—work that should make it possible to use renewable energy such as solar or wind power to create hydrogen-based fuels. These in turn could help decarbonize transport, buildings, and industrial processes.
“One great opportunity for mitigating global climate change is to make chemicals and fuels using electricity from sunlight and wind at scale,” Shao-Horn says. “Mastering the catalysis of bond breaking/making and ion/electron transfer is critical to supporting this work by enabling highly efficient and sustainable processes and systems.”
Carbon Capture
Project: Removing carbon dioxide from the air by passing it through a stack of charged electrochemical plates, a far more efficient system than most current carbon-capture technologies.
Key researcher: T. Alan Hatton, Ralph Landau Professor of Chemical Engineering
Breakthrough technology developed at MIT holds promise for combating climate change by removing CO2 from the air. The technique, which is based on passing air through a stack of charged electrochemical plates, is more efficient than most existing carbon-capture technologies and has the significant advantage of treating gas in any concentration, from power plant emissions to open air.
What the researchers have developed is essentially a large, specialized battery that absorbs carbon dioxide from gas passing over its electrodes as it is being charged up, and then releases the gas as it is being discharged. In operation, the device would simply alternate between charging and discharging, with fresh air or feed gas being blown through the system during the charging cycle, and pure, concentrated carbon dioxide being blown out during discharging.
A key advantage of this system is that it works in ambient conditions, with no need for thermal, pressure, or chemical input. While most methods of removing carbon dioxide from a stream of gas require high concentrations, the new system can remove CO2 at virtually any level, even down to the roughly 400 parts per million currently found in the atmosphere.
“Electrochemically based separations technology provides a unique opportunity to address climate change concerns, as we can readily tailor these versatile systems to a variety of needs, with lower energy demands, by exploiting solely renewable energy sources,” Hatton says.
Carbon Sequestration
Project: Studying the physics of multiphase flow in porous media, with applications to a variety of energy-driven geophysical problems including carbon sequestration, methane hydrates, and petroleum recovery.
Key researcher: Ruben Juanes, Professor of Civil and Environmental Engineering
Studying the physics of multiphase flow in porous media, with applications to a variety of energy-driven geophysical problems including carbon sequestration, methane hydrates, and petroleum recovery.
Capturing CO2 from the atmosphere and storing it out of harm’s way is a critical component of most plans to address climate change. However, researchers do not yet fully understand geologic storage capacities or the best way to ensure sustainable injection rates. Theoretical, computational, and experimental research under way at MIT promises to provide this foundational understanding by elucidating the physics of multiphase flow in porous media.
Such flows, composed of gases, solids, and liquids in diverse mixes, affect a range of real-world applications, from oil and gas recovery and groundwater resource management to seismic activity mapping and energy-storage technology. For example, the phenomenon of wettability—a measure of a substance’s attraction to or repulsion of water—can impact the flow of injected CO2 into the subsurface.
At MIT, researchers are investigating a full range of phenomena related to multiphase flow in porous media, including the underlying mechanisms that control the trapping of CO2 in saline aquifers and the way in which methane, a potent greenhouse gas, seeps up from formations in the seafloor.
“While there’s increased interest in a range of negative emissions technologies that remove greenhouse gases (particularly CO2) from the atmosphere, making these technologies a reality relies on disposing of enormous quantities of CO2 and storing it in the subsurface,” Juanes says, noting that billions of metric tons of CO2 will need to be stored. “The goal of our work is to make that possible.”
Solar
Project: Paving the way to new, more efficient solar cells through a streamlined system for screening perovskites for use as semiconductors.
Key researcher: Tonio Buonassisi, Professor of Mechanical Engineering
The process of developing new, more efficient solar cells can be slow and painstaking. MIT researchers have developed a streamlined system for screening new formulations of perovskites, a broad class of materials that may one day replace silicon as a cheap and highly efficient material for solar cells.
While more than a thousand potentially useful perovskite formulations have been predicted theoretically, only a small fraction of the millions of possible combinations has been produced experimentally, highlighting the need for an accelerated process. The new system makes it possible to make and test a wide variety of materials in parallel, which may cut development time from 20 years to two.
Most of the improvements in throughput speed resulted from workflow ergonomics, such as tracking and timing the many steps involved: synthesizing new compounds, depositing them on a substrate to crystallize, and then observing and classifying the resulting crystal formations using multiple techniques. In initial testing, this system reduced the time needed to synthesize and characterize a set of formulations by 90%. Recently, the team has started using machine learning to guide the search for better materials.
“When the time investment of running an experiment drops by a factor of 100, researchers become more confident in taking big steps—exploring materials that are further from their comfort zone and learning faster—likely enabling bigger discoveries in the future,” Buonassisi says.
Food
Project: Developing new varieties of sustainable polymers that could provide all the food safety and preservation properties of plastics while being fully compostable.
Key researcher: Bradley D. Olsen ’03, Professor of Chemical Engineering
Food packaging is critical to the distribution of safe and sterile food; however, current packaging materials are not sustainable. Abdul Latif Jameel Water and Food Systems Lab researchers are working to develop new varieties of sustainable polymers that can be produced from biomass and also degraded at the end of use, thus creating a closed carbon cycle.
The researchers are developing models to predict permeability as a function of chemical structure, and they plan to test their new materials for permeability and biodegradability using model high-throughput assays. They will then use the information they garner to evaluate potential new candidate polymers for packaging.
The goal is to develop packaging that is both fully compostable and carries all of the food safety and preservation properties of plastics.
“I am excited about the chance we have to update our material infrastructure to simultaneously meet human needs and care for the environment,” Olsen says.
Low-Carbon Energy
Project: Building portable microreactors that can operate independently from the electric grid. These small fission reactors could power a vast array of activities across all sectors of the economy.
Key researcher: Jacopo Buongiorno PhD ’01, TEPCO Professor of Nuclear Science and Engineering
Enabled by advances in embedded intelligence and adaptive manufacturing and materials, MIT researchers are developing new portable microreactors. These small fission reactors could be transported by planes, trains, or trucks to bring secure, reliable, and affordable energy to a wide range of energy users across all sectors of the economy. This work has the potential to structurally change the very nature of energy supply and global economic competition by delivering clean, virtually unlimited electricity and heat to users anywhere on the planet at any scale—without being connected to a national grid or fuel pipeline.
The goal of this work is to provide energy locally for industrial processes such as the desalination of water or the production of food and medications. Nuclear microreactors could even be used to generate hydrogen or other synthetic fuels for use in industrial processes and transportation.
Since the microreactors could be deployed quickly in any community, their adoption could facilitate a more distributed, democratized, and secure energy-industrial system.
“Portable microreactors bring nuclear into the 21st century. Providing nuclear energy suddenly becomes a timely and affordable service, not a decade-long, multibillion-dollar construction project,” Buongiorno says.
Water
Project: Creating low-cost, low-power drip irrigation systems to impact the lives of smallholder and marginal farmers worldwide and to help protect the global supply of fresh water.
Key researcher: Amos Winter SM ’05, PhD ’11, Associate Professor of Mechanical Engineering
More than 70% of fresh water consumed around the world goes into agriculture, primarily irrigation. Employing drip irrigation, which delivers water through piping right at the base of the crops, would reduce consumption and aid regions experiencing water shortages. However, there are two key barriers to adoption: high initial cost and the need for electrical power to pump water.
MIT researchers are working to address these challenges by investigating how drip irrigation emitter design, pump design, pump controls, and irrigation scheduling might enable solar-powered, off-grid drip systems to become an affordable option. While endeavoring to minimize system costs, energy, and water use, they are also conducting stakeholder interviews in sub-Saharan Africa, North Africa, and the Middle East to better understand the irrigation needs of small farmers.
The goal of this project is to create off-grid, solar-powered drip irrigation systems that would be economically viable for the 500+ million subsistence farmers worldwide. Implementation would help protect the limited global supply of fresh water.
“I am most excited about seeing opportunities to create substantial changes in the well-established irrigation industry,” Winter says. “Through innovations in drip irrigation and automated controllers that efficiently harness renewable power sources, I am confident we can create low-cost, low-power irrigation systems that lead to increased crop production and farmers’ profits without overconsumption of water resources.”