In 1957, the Soviet Union launched Sputnik. Several months later, the U.S. sent Explorer I into space. With two small objects, the space race began. 

As of March 2025, more than 11,000 satellites are orbiting Earth. According to some estimates, there could be as many as 60,000 by 2030. 

“In the Space Age, space activity was overtly geopolitical, and that’s never really gone away,” said Mariel Borowitz, associate professor in the Sam Nunn School of International Affairs and director of the recently launched Center for Space Policy and International Relations. “But the major shift now is the rapid rise of commercial activity and the number of actors in space.”

Space traffic is global by nature — satellites cross over myriad countries while orbiting. Thanks to the Outer Space Treaty, every country has the right to access space. More actors in space, though, mean more trash and more potential collisions. 

Borowitz and her colleagues in the Nunn School analyze and help develop policies on protecting space so it remains safe and usable in the future. In other words, they’re doing everything they can to make sure things don’t blow up. 

Taking Out the (Space) Trash

Thomas González Roberts, a postdoctoral fellow in the Nunn School, has a research portfolio that unites his background in astrodynamics with space governance. One area he specializes in is space debris and its impact on the sustainability of space operations. 

"We define space debris as objects in Earth orbit that are no longer actively being controlled," Roberts said. "A satellite that has run out of fuel, for example, becomes a piece of floating garbage.” 

The issue, he notes, isn't just the large pieces of debris but also the many tiny fragments that go undetected. 

"We can track objects the size of a softball, but anything smaller is more challenging to spot with current technology," he explained. "These small pieces can still destroy satellites because of their velocity, like a bullet can harm a human."

As such, debris presents not only a physical hazard but also a complex issue for satellite operators trying to navigate these invisible threats. Roberts also highlights the rising number of satellites in popular orbital regimes. Low Earth orbit (LEO) is the closest orbital regime to Earth. Beginning at the upper reaches of the Earth’s atmosphere, it hosts communication and observational satellites and is by far the most congested region of all. 

"There are only a few spots in the near-Earth space environment where satellite operators want to be, effectively making these regions limited natural resources,” he said. “Without proper coordination, these valuable spaces will be overcrowded, making it harder to avoid collisions and creating more debris."

To address these issues, Roberts advocates for better international coordination and the development of more effective space policies. "How operators choose to control their satellites is a form of space policy," he noted. "We need transparent, collaborative policies that encourage more responsible space operations. When a satellite mission is completed, operators should clean up after themselves, ensuring the long-term viability of these orbital regions."

Space Situational Awareness

Space situational awareness (SSA) involves tracking objects in space, predicting their movements, and identifying potential collisions. If a potential collision is detected, the next step is determining whether to issue a warning. Currently, the U.S. military operates the most globally advanced SSA system, providing collision warnings free of charge to spacecraft operators worldwide. However, there is an ongoing effort to shift this mission to a civil agency, the Office of Space Commerce (OSC), because so much of space activity is now international and commercial.

In 2022, Borowitz testified before Congress on transitioning from a military to a civilian SSA system. A few months later, she was invited to join the OSC on a detail to help implement this transition. Currently, she spends half her time there as head of International SSA Engagement. Her work bridges the gap between research and government operations, ensuring that advances in academia inform policy and operations.

Borowitz and Brian Gunter, a professor in the Daniel Guggenheim School of Aerospace Engineering, launched a joint project tackling the complex issue of space traffic coordination, supported by a grant from NASA.

Their detailed simulation model — the Georgia Tech Virtual Environment for Space Traffic Analysis (VESTA) — incorporates real satellite data from military space situational awareness systems to test out possible space traffic coordination rules. 

“One question we’re trying to answer is whether, when we see the possibility of a collision in space, we should have right-of-way rules,” Borowitz said. “We have them on the ground for cars, and we have them in the air and at sea. In space, we have no real concept of right of way.”  

Through this approach, Borowitz and Gunter can test different traffic rules and collision scenarios over months and even years. Their model also assesses the impact of these rules on different countries and companies, and what might happen if some actors choose not to follow them.

“The results of these simulations are crucial for shaping international agreements; they provide concrete data on the potential costs and benefits of unilateral versus multilateral approaches to space governance,” Borowitz said. “This kind of research not only brings technical astrodynamics into policy discussions but also offers valuable insights for negotiating space traffic coordination at a global scale.”

By combining cutting-edge research with real-world policy work, Borowitz, Roberts, and their colleagues are helping ensure that space remains usable for everyone. With their work, the path to a safer space environment is becoming clearer.

Funding: The VESTA project is supported in part through NASA and in part through the Partnership for an Advanced Computing Environment (PACE) at the Georgia Institute of Technology.

For centuries, innovations in structural materials have prioritized strength and durability — often at a steep environmental price. Today, the construction industry accounts for approximately 10% of global greenhouse gas emissions, with cement, steel, and concrete responsible for more than two-thirds of that total. As the world presses for a sustainable future, scientists are racing to reinvent the very foundations of our built environment.

Paradigm Shift in Construction

Now, researchers at Georgia Tech have developed a novel class of modular, reconfigurable, and sustainable building blocks — a new construction paradigm as well-suited for terrestrial homes as it is for extraterrestrial habitats. Their study, published in Matter, demonstrates that these innovative units, dubbed eco-voxels, can reduce carbon footprints by up to 40% compared to traditional construction materials. These units also maintain the structural performance needed for applications ranging from load-bearing walls to aircraft wings.

“We created sustainable structures using these eco-friendly building blocks, combining our knowledge of structural mechanics and mechanical design with industry-relevant manufacturing practices and environmental assessments,” said Christos Athanasiou, assistant professor at the Daniel Guggenheim School of Aerospace Engineering.

Housing Affordability Solutions

Their work offers a potential solution to the growing housing affordability crisis. As climate-driven disasters such as hurricanes, wildfires, and floods increase, homes are damaged at higher rates, and insurance costs are skyrocketing. This crisis is fueled by rising land prices and restrictive development regulations. Meanwhile, the growing demand for housing places an increasing strain on global resources and the environment. The modularity and circularity of the developed approach can effectively address these issues. 

The New Building Blocks

Eco-voxels — short for eco-friendly voxels, the 3D equivalent of pixels — are made from polytrimethylene terephthalate (PTT). PTT is a partially bio-based polymer derived from corn sugar and reinforced with recycled carbon fibers from aerospace waste (scrap material lost during the manufacturing of aerospace components). Eco-voxels can be easily assembled into large, load-bearing structures and then disassembled and reconfigured, all without generating waste. Consequently, they offer a highly adaptable, sustainable approach to construction.

The team tested eco-voxels and found they can handle the pressure that buildings usually face. They also used computer simulations to show that changing the shape of eco-voxels makes them suitable for many different building needs.

The researchers compared the eco-voxel approach to other emerging construction methods like 3D-printed concrete and cross-laminated timber (CLT), finding that eco-voxels offer significant environmental advantages. While traditional and alternative materials are often heavy and carbon-intensive, the eco-voxel wall had the lowest carbon footprint: 30% lower than concrete and 20% lower than CLT.

These results highlight eco-voxels as a promising low-carbon, high-performance solution for sustainable and affordable construction, opening new possibilities for faster, more sustainable building solutions. In addition to residential uses, emergency shelters built with eco-voxels could be used for disaster-relief scenarios, where quick assembly, modularity, and minimal environmental impact are crucial.

From sun damage and pollution to cuts and infections, our skin protects us from a lot. But it isn’t impenetrable.

“We tend to think of our skin as being this impermeable barrier that’s just enclosing our body,” said Matthew Flavin, assistant professor in the School of Electrical and Computer Engineering. “Our skin is constantly in flux with the gases that are in our environment and our atmosphere.”

Led by the Georgia Institute of Technology, Northwestern University, and the Korea Institute of Science and Technology (KIST), researchers have developed a novel wearable device that can monitor the flux of vapors through the skin, offering new insights into skin health and wound healing. This technology, detailed in a recent Nature publication, represents a significant advancement in the field of wearable bioelectronics.

“You could think of this being used where a Band-Aid is being used,” said Flavin, one of the lead authors of the study. The compact, wireless device is the first wearable technology able to continuously and precisely measure water vapor, volatile organic compounds, and carbon dioxide fluxes in the skin in real time. Because increases in these factors are associated with infection and delayed healing, Flavin notes that this kind of wireless monitoring “could give clinicians a new tool to understand the properties of the skin.”

The Measurement Barrier

Our skin is our first line of defense against environmental hazards. Measuring how effectively it protects us from harmful pollutants or infections has been a significant challenge, especially over extended periods.

“The vapors coming from your skin are in very, very low concentration,” explained Flavin. “If we just put a sensor next to your skin, it would be almost impossible to control that measurement.”

The new device features a small chamber that condenses and measures vapors from the skin using specialized sensors hovering above the skin. A low-energy, bi-stable mechanism periodically refreshes the air in the chamber, allowing for continuous measurements communicated to a smartphone or tablet through Bluetooth.

“There are other devices that can measure certain parts of what we're talking about here,” said Flavin, “but they are not feasible for a wearable device, can't do this continuously, and are not able to get all the information that our device can get.”

Scratching the Surface

By tracking the skin's water vapor flux, also known as transepidermal water loss, the device can assess skin barrier function and wound healing. This capability is particularly valuable for tracking the healing process in diabetic patients, who often have sensory issues that complicate wound monitoring. “What you see in diabetes is that even after the wound looks like it's healed, there's still a persistent impairment of that barrier,” said Flavin. This new non-invasive device tracks those properties. 

“There are many areas where people don't have great access to healthcare, and there aren’t doctors monitoring wound healing processes,” Flavin added. “Something that can be used to monitor that remotely could make care more accessible to people with these conditions.”

The device’s wearable nature also makes it ideal for studying the long-term effects of exposure to environmental hazards like wildfires or chemical fumes on skin function and overall health.

Though the applications in health are numerous, the research team is continuing to explore different ways to use the device. “This measurement modality is very new and we're still learning what we can do with it,” saidJaeho Shin, a senior researcher at KIST and a co-leader of the study. “It's a new way of measuring what's inside the body.” 

“This is a great example of the kind of technology that can emerge from research at the interface between engineering science and medical practice,” said John Rogers, a materials science professor at Northwestern and another co-leader of the study. “The capabilities provided by this device will not only improve patient care, but they will also lead to improved understanding of the skin, the skin microbiome, the processes of wound healing, and many others.”

As a new faculty member and a member of Georgia Tech’s Neuro Next Initiative, a burgeoning interdisciplinary research hub for neuroscience, neurotechnology, and society, Flavin attributes the success of this research to its interdisciplinary nature.

“A broad challenge we have in these fields of research is that they integrate a lot of different areas. One of the reasons I came to Georgia Tech is because it's a place where you have access to all those different areas of expertise.”

DOI: https://doi.org/10.1038/s41586-025-08825-2

Funding: Querrey-Simpson Institute for Bioelectronics and the Center for Advanced Regenerative Engineering (CARE), Northwestern University; National Research Foundation of Korea; National Institutes of Health (NIH), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Biomedical Imaging and Bioengineering.

Two faculty members represented Georgia Tech as new fellows to the world’s leading organization dedicated to applied mathematics, computational science, and data science.

The Society for Industrial and Applied Mathematics (SIAM) selected Elizabeth Cherry and Katya Scheinberg as Class of 2025 fellows. The two Georgia Tech faculty join an illustrious class of 23 other researchers from around the globe in this year’s class. 

SIAM selected Cherry to recognize her contributions to mathematical and computational modeling and extensive service to the SIAM community. She studies the electrical behavior of cardiac cells and tissue.

Cherry’s computer models and simulations improve understanding of cardiac dynamics in normal and diseased states. Using these tools, she designs advanced strategies for preventing and treating arrhythmias.

“SIAM has played a huge role in my professional development—the first conference I attended as a graduate student was a SIAM conference, and I’ve attended at least one SIAM conference almost every year since then,” Cherry said. 

“Given this long history, it means a lot to me for SIAM to acknowledge my contributions in this way.”

Scheinberg, from Georgia Tech’s College of Engineering, was selected for her foundational contributions to derivative-free optimization and optimization applications in data science and her dedicated service to the optimization community.

[Related: Coca-Cola Foundation Chair Katya Scheinberg selected for 2025 Class of SIAM Fellows]

Cherry is the fifth faculty member from the School of Computational Science and Engineering (CSE) to be selected as a SIAM Fellow.

Cherry’s announcement as a SIAM Fellow comes weeks after serving in a leadership role at a SIAM conference. She co-chaired the organizing committee of the SIAM Conference on Computational Science and Engineering (CSE25).

In 2023, SIAM members reelected Cherry to a second term as a council member-at-large. She began her three-year term in January 2024.

"SIAM Fellows are selected for deep mathematical contributions. Receiving Fellow status is a high honor for any applied mathematician," said Regents’ Professor Srinivas Aluru, senior associate dean of the College of Computing and Class of 2020 SIAM Fellow. 

"Not only are Elizabeth's contributions technically outstanding, but her work also provides deep insights into the functioning of the heart and its abnormalities."

Cherry’s leadership and service extends outside of SIAM, influencing students and faculty across Georgia Tech. 

In December, the College of Computing appointed Cherry as associate dean for graduate education. Before this appointment, she served as associate chair for academic affairs of the School of CSE. 

With her new role as associate dean, Cherry continues serving as director of CSE programs at Georgia Tech. 

In March 2024, Cherry was among five Georgia Tech faculty members selected for the ACC Academic Leaders Network (ACC ALN) Fellows program. The ALN program fosters cross-institutional networking and collaboration between ACC schools, increasing each institution’s academic leadership capacity.

Cherry was part of a team of Georgia Tech and Emory University researchers who won a Georgia Clinical and Translational Science Alliance award in 2023. The group earned the Team Science Award of Distinction for Early Stage Research Teams award for work that captures high-resolution visualizations of spiral waves that create heart arrhythmias.

SIAM will recognize Cherry, Scheinberg, and Class of 2025 fellows during a reception at the SIAM/CAIMS Annual Meetings this July in Montréal.

“It is such an honor to be recognized as a SIAM Fellow,” Cherry said. “I’m thrilled to join my CSE colleagues who have also received this recognition.”

In a groundbreaking study published in Nature, researchers from Georgia Tech and Emory University have developed a new model that could enable precise, life-saving medication delivery for blood clot patients. The novel technique uses a 3D microchip

Wilbur Lam, professor at Georgia Tech and Emory University, and a clinician at Children’s Healthcare of Atlanta, led the study. He worked closely with Yongzhi Qiu, an assistant professor in the Department of Pediatrics at Emory University School of Medicine. 

The significance of the thromboinflammation-on-a-chip model, is that it mimics clots in a human-like way, allowing them to last for months and resolve naturally. This model helps track blood clots and more effectively test treatments for conditions including sickle cell anemia, strokes, and heart attacks. 

Read the full story from Emory University

In a significant move to bolster Georgia's workforce, Georgia Tech has partnered with Georgia Quick Start to advance manufacturing training and skill development. This collaboration, formalized by the signing of a Memorandum of Understanding on April 8, aims to elevate the quality and efficiency of manufacturing workforce training across the state.

“At Georgia Tech, innovation isn’t just about discovery — it’s about solving real-world challenges,” said Executive Vice President for Research Tim Lieuwen. “Georgia Quick Start ensures that cutting-edge research in advanced manufacturing translates into practical training solutions. Together, we are equipping Georgia’s workforce with the skills needed to drive economic growth and industry advancement.”

As manufacturing technologies and artificial intelligence continue to evolve, U.S. manufacturers increasingly require skilled workers experienced in advanced manufacturing. For decades, Georgia Quick Start, administered by the Technical College System of Georgia, has been addressing this need and has been recognized as the country’s top workforce training program for 15 years. 

Now, researchers at Georgia Tech will collaborate with Georgia Quick Start to enhance these efforts by developing Extended Reality (XR) training programs, providing a scalable and experiential solution to meet the growing demand for training. 

“We have been so successful for so many years because we stay focused on relevance, flexibility, and responsiveness,” said Scott McMurray, deputy commissioner for Georgia Quick Start. “This partnership is an example of how Quick Start is able to develop and deliver effective training even for companies working on the leading edge of advanced manufacturing technologies.”

Extended Reality, Scaled Training

XR technologies use a combination of virtual and augmented reality to create immersive, interactive experiences. By simulating real-world manufacturing environments and processes, XR has the potential to allow trainees to practice and refine their skills in a controlled, risk-free setting through standardized training experiences. This not only enhances the learning experience but also ensures consistency in training quality across a large workforce.

“Virtual reality scales training by gamifying complex tasks and removing the need for costly or hazardous physical equipment. Augmented reality scales on-the-job training by providing adaptive, context-aware guidance exactly when and where it’s needed, reducing the need for expert supervision,” said manufacturing XR researcher Mohsen Moghaddam, Gary C. Butler Family associate professor in the H. Milton Stewart School of Industrial and Systems Engineering and the George W. Woodruff School of Mechanical Engineering. “Together, they make training more consistent, up-to-date, accessible, and safe, especially for workers who may hesitate to ask for assistance from peers or supervisors out of fear of judgment.”

The collaboration will leverage Moghaddam’s research and the AR/VR training space within the expanded Advanced Manufacturing Pilot Facility, providing a state-of-the-art environment for developing and deploying XR training technologies. Researchers from the Georgia Tech Manufacturing Institute (GTMI) and Georgia AIM (Artificial Intelligence in Manufacturing) will also play pivotal roles in the development of these training programs.

“Partnerships like these highlight the power of the integrated University of Georgia and Technical College System of Georgia’s workforce development ecosystem,” said Thomas Kurfess, Regents’ Professor and GTMI executive director. “Our country not only needs the creation of new jobs but also the skilled workforce to fill them. At Georgia Tech and GTMI, we are serving as an enabler of innovation in that workforce development.”

Georgia Tech School of Electrical and Computer Engineering (ECE) Professor Christopher Rozell was inducted into the American Institute for Medical and Biological Engineering (AIMBE) College of Fellows at the AIMBE Annual Event on March 31 in Arlington, Va.

College membership honors those, “who have made outstanding contributions to engineering and medicine research, practice, or education,” and “to the pioneering of new and developing fields of technology, making major advancements in traditional fields of medical and biological engineering or developing/implementing innovative approaches to bioengineering education.”

The distinction is among the highest professional distinctions given to medical and biological engineers, comprised of the top two percent of engineers in these fields.

He was nominated and inducted for outstanding contributions to computational neuroengineering, psychiatric neuromodulation, and international leadership in accessible biomedical education.

Rozell's research interests are in computational neuroengineering, an intersection of neuroscience, data science, neurotechnology and computational modeling that advances the understanding of brain function and the design of effective interventions.

His research has a particular focus on advancing our understanding and novel brain stimulation therapies for psychiatric disorders such as treatment resistant depression.

Recently, he was part of a team that identified a unique pattern in brain activity that reflects the recovery process in patients with treatment-resistant depression. This pattern, known as a biomarker, represented a significant advance in treatment for the most severe and untreatable forms of depression.

His work also includes research that takes a creative approach to advancing the understanding of the societal impacts of emerging technologies such as neurotechnology and AI.

Rozell especially takes pride in being a first-generation scholar who is committed to accessibility in scientific communities. In pursuit of this goal, he co-founded and serves on the Board of Directors of Neuromatch, Inc., a global nonprofit increasing access to scientific knowledge.

His scholarly efforts have resulted in many published works in top publications, such as Nature, and a number of awards, including the NSF CAREER Award.

Before joining the ECE faculty in 2008 as an assistant professor, Rozell received a B.S.E. degree in computer engineering and a B.F.A. degree in music in 2000 from the University of Michigan. He then received M.S. and Ph.D. degrees in electrical engineering in 2002 and 2007 from Rice University and was a postdoctoral scholar at the Redwood Center for Theoretical Neuroscience at the University of California, Berkeley.

For the second consecutive year, Georgia Tech’s graduate engineering program is No. 4 on the Best Graduate Schools rankings released by U.S. News & World Report. The College of Engineering remains second among all public programs. 

The updated list, out April 8, also placed each of the College’s individual disciplines ninth or higher. It’s the 14th straight year with every program in the top 10.

See the full rankings on the College of Engineering website.

Micro-brain sensors placed between hair strands overcome traditional brain sensor limitations.

Georgia Tech researchers have developed an almost imperceptible microstructure brain sensor to be inserted into the minuscule spaces between hair follicles and slightly under the skin. The sensor offers high-fidelity signals and makes the continuous use of brain-computer interfaces (BCI) in everyday life possible.

BCIs create a direct communication pathway between the brain's electrical activity and external devices such as electroencephalography devices, computers, robotic limbs, and other brain monitoring devices. Brain signals are commonly captured non-invasively with electrodes mounted on the surface of the human scalp using conductive electrode gel for optimum impedance and data quality. More invasive signal capture methods such as brain implants are possible, but this research seeks to create sensors that are both easily placed and reliably manufactured. 

Hong Yeo, the Harris Saunders Jr. Professor in the George W. Woodruff School of Mechanical Engineering, combined the latest microneedle technology with his deep expertise in wearable sensor technology that may allow stable brain signal detection over long periods and easy insertion of a new painless, wearable microneedle BCI wireless sensor that fits between hair follicles. The skin placement and extremely small size of this new wireless brain interface could offer a variety of benefits over traditional gel or dry electrodes.

“I started this research because my main goal is to develop new sensor technology to support healthcare and I had previous experience with brain-computer interfaces and flexible scalp electronics,” said Yeo, who is also a faculty member in Georgia Tech’s Institute for People and Technology. “I knew we needed better BCI sensor technology and discovered that if we can slightly penetrate the skin and avoid hair by miniaturizing the sensor, we can dramatically increase the signal quality by getting closer to the source of the signals and reduce unwanted noise.”

Today’s BCI systems consist of bulky electronics and rigid sensors that prevent the interfaces from being useful while the user is in motion during regular activities. Yeo and colleagues constructed a micro-scale sensor for neural signal capture that can be easily worn during daily activities, unlocking new potential for BCI devices. His technology uses conductive polymer microneedles to capture electrical signals and conveys those signals along flexible polyimide/copper wires — all of which are packaged in a space of less than 1  millimeter.

A study of six people using the device to control an augmented reality (AR) video call found that high-fidelity neural signal capture persisted for up to 12 hours with very low electrical resistance at the contact between skin and sensor. Participants could stand, walk, and run for most of the daytime hours while the brain-computer interface successfully recorded and classified neural signals indicating which visual stimulus the user focused on with 96.4% accuracy. During the testing, participants could look up phone contacts and initiate and accept AR video calls hands-free as this new micro-sized brain sensor was picking up visual stimuli — all the while giving the user complete freedom of movement.  

According to Yeo, the results suggest that this wearable BCI system may allow for practical and continuous interface activity, potentially leading to everyday use of machine-human integrative technology.

“I firmly believe in the power of collaboration, as many of today’s challenges are too complex for any one individual to solve,” said Yeo. “Therefore, I would like to express my gratitude to all the researchers in my group and the amazing collaborators who made this work possible. I will continue collaborating with the team to enhance BCI technology for rehabilitation and prosthetics.”

Note: Hodam Kim (postdoctoral research fellow), Ju Hyeon Kim (visiting Ph.D. student from Inha University – South Korea), and Yoon Jae Lee (Ph.D. student) also played a major role in developing this technology.

Funding: National Science Foundation NRT (Research Traineeship program in the Sustainable Development of Smart Medical Devices), WISH Center (Institute for Matter and Systems), and partial research support from several South Korean programs and grants.

PNAS article publication (April 7, 2025, Vol. 122, No. 15): https://www.pnas.org/doi/10.1073/pnas.2419304122

When the International Maritime Organization enacted a mandatory cap on the sulfur content of marine fuels in 2020, with an eye toward reducing harmful environmental and health impacts, it left shipping companies with three main options.

They could burn low-sulfur fossil fuels, like marine gas oil, or install cleaning systems to remove sulfur from the exhaust gas produced by burning heavy fuel oil. Biofuels with lower sulfur content offer another alternative, though their limited availability makes them less feasible.

While installing exhaust gas cleaning systems, known as scrubbers, is the most feasible and cost-effective option, there has been a great deal of uncertainty among firms, policymakers, and scientists as to how “green” these scrubbers are.

Through a novel lifecycle assessment, researchers from Georgia Tech, MIT, and elsewhere have now found that burning heavy fuel oil with scrubbers in the open ocean can match or surpass using low-sulfur fuels, when a wide variety of environmental factors is considered.

The scientists combined data on the production and operation of scrubbers and fuels with emissions measurements taken onboard an oceangoing cargo ship.

They found that, when the entire supply chain is considered, burning heavy fuel oil with scrubbers was the least harmful option in terms of nearly all 10 environmental impact factors they studied, such as greenhouse gas emissions, terrestrial acidification, and ozone formation.

“In our collaboration with Oldendorff Carriers to broadly explore reducing the environmental impact of shipping, this study of scrubbers turned out to be an unexpectedly deep and important transitional issue,” said Neil Gershenfeld, an MIT professor, director of the Center for Bits and Atoms (CBA), and senior author of the study.

“Claims about environmental hazards and policies to mitigate them should be backed by science. You need to see the data, be objective, and design studies that take into account the full picture to be able to compare different options from an apples-to-apples perspective,” added lead author Patricia Stathatou, an assistant professor at Georgia Tech, who began this study as a postdoc in the CBA.

Stathatou is joined on the paper by Michael Triantafyllou and others at Naias Laboratories, the National Technical University of Athens in Greece, and the maritime shipping firm Oldendorff Carriers. The research appeared recently in Environmental Science and Technology.

Slashing sulfur emissions

Heavy fuel oil, traditionally burned by bulk carriers that make up about 30 percent of the global maritime fleet, usually has a sulfur content around 2 to 3 percent. This is far higher than the International Maritime Organization’s 2020 cap of 0.5 percent in most areas of the ocean and 0.1 percent in areas near population centers or environmentally sensitive regions.

Sulfur oxide emissions contribute to air pollution and acid rain, and can damage the human respiratory system.

In 2018, fewer than 1,000 vessels employed scrubbers. After the cap went into place, higher prices of low-sulfur fossil fuels and limited availability of alternative fuels led many firms to install scrubbers so they could keep burning heavy fuel oil.

Today, more than 5,800 vessels utilize scrubbers, the majority of which are wet, open-loop scrubbers.

“Scrubbers are a very mature technology. They have traditionally been used for decades in land-based applications like power plants to remove pollutants,” Stathatou explained.

A wet, open-loop marine scrubber is a huge, metal, vertical tank installed in a ship’s exhaust stack, above the engines. Inside, seawater drawn from the ocean is sprayed through a series of nozzles downward to wash the hot exhaust gases as they exit the engines.

The seawater interacts with sulfur dioxide in the exhaust, converting it to sulfates — water-soluble, environmentally benign compounds that naturally occur in seawater. The washwater is released back into the ocean, while the cleaned exhaust escapes to the atmosphere with little to no sulfur dioxide emissions.

But the acidic washwater can contain other combustion byproducts like heavy metals, so scientists wondered if scrubbers were comparable, from a holistic environmental point of view, to burning low-sulfur fuels.

Several studies explored toxicity of washwater and fuel system pollution, but none painted a full picture.

The researchers set out to fill that scientific gap.

A “well-to-wake” analysis

The team conducted a lifecycle assessment using a global environmental database on production and transport of fossil fuels, such as heavy fuel oil, marine gas oil, and very-low sulfur fuel oil. Considering the entire lifecycle of each fuel is key, since producing low-sulfur fuel requires extra processing steps in the refinery, causing additional emissions of greenhouse gases and particulate matter.

“If we just look at everything that happens before the fuel is bunkered onboard the vessel, heavy fuel oil is significantly more low-impact, environmentally, than low-sulfur fuels,” Stathatou said.

The researchers also collaborated with a scrubber manufacturer to obtain detailed information on all materials, production processes, and transportation steps involved in marine scrubber fabrication and installation.

“If you consider that the scrubber has a lifetime of about 20 years, the environmental impacts of producing the scrubber over its lifetime are negligible compared to producing heavy fuel oil,” she noted.

For the final piece, Stathatou spent a week onboard a bulk carrier vessel in China to measure emissions and gather seawater and washwater samples. The ship burned heavy fuel oil with a scrubber and low-sulfur fuels under similar ocean conditions and engine settings.

Collecting these onboard data was the most challenging part of the study.

“All the safety gear, combined with the heat and the noise from the engines on a moving ship, was very overwhelming,” she said.

Their results showed that scrubbers reduce sulfur dioxide emissions by 97 percent, putting heavy fuel oil on par with low-sulfur fuels according to that measure. The researchers saw similar trends for emissions of other pollutants like carbon monoxide and nitrous oxide.

In addition, they tested washwater samples for more than 60 chemical parameters, including nitrogen, phosphorus, polycyclic aromatic hydrocarbons, and 23 metals.

The concentrations of chemicals regulated by the IMO were far below the organization’s requirements. For unregulated chemicals, the researchers compared the concentrations to the strictest limits for industrial effluents from the U.S. Environmental Protection Agency and European Union.

Most chemical concentrations were at least an order of magnitude below these requirements.

In addition, since washwater is diluted thousands of times as it is dispersed by a moving vessel, the concentrations of such chemicals would be even lower in the open ocean.

These findings suggest that the use of scrubbers with heavy fuel oil can be considered as equal to or more environmentally friendly than low-sulfur fuels across many of the impact categories the researchers studied.

“This study demonstrates the scientific complexity of the waste stream of scrubbers. Having finally conducted a multiyear, comprehensive, and peer-reviewed study, commonly held fears and assumptions are now put to rest,” said Scott Bergeron, managing director at Oldendorff Carriers and co-author of the study.

“This first-of-its-kind study on a well-to-wake basis provides very valuable input to ongoing discussion at the IMO,” said Thomas Klenum, executive vice president of innovation and regulatory affairs at the Liberian Registry, emphasizing the need “for regulatory decisions to be made based on scientific studies providing factual data and conclusions.”

Ultimately, this study shows the importance of incorporating lifecycle assessments into future environmental impact reduction policies, Stathatou said.

“There is all this discussion about switching to alternative fuels in the future, but how green are these fuels? We must do our due diligence to compare them equally with existing solutions to see the costs and benefits,” she concluded.

In addition to Georgia Tech and MIT, Mario Tsezos' team from Naias Labs in Greece contributed significantly to the research. This study was supported in part by Oldendorff Carriers. 

- Written by Adam Zewe, MIT News Office