A new study led by researchers from MIT, Georgia Tech, and other institutions suggests that the use of marine scrubbers—devices that clean sulfur emissions from exhaust gases—may be just as environmentally friendly, if not more so, than burning low-sulfur fuels. This groundbreaking research, published in Environmental Science and Technology, challenges the common assumptions about the environmental impact of scrubbers and has important implications for the future of the maritime industry.

The 2020 mandate by the International Maritime Organization (IMO) to cap the sulfur content of marine fuels at 0.5% pushed shipping companies to consider alternatives to the traditionally used heavy fuel oil (HFO), which contains much higher levels of sulfur. The options? Companies could either burn low-sulfur fossil fuels, install exhaust gas cleaning systems (scrubbers), or switch to biofuels. While the latter has been limited by availability, scrubbers became the go-to solution for many, thanks to their cost-effectiveness and ability to enable continued use of cheaper, high-sulfur fuels.

However, a critical question remained: How “green” are scrubbers when viewed through a holistic environmental lens?

“Scrubbers Turned Out to Be an Unexpectedly Deep and Important Transitional Issue”

According to Neil Gershenfeld, MIT professor and senior author of the study, the study explored this question through a comprehensive lifecycle assessment. “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,” he explained.

The Study: A Comprehensive “Well-to-Wake” Assessment

The researchers used a “well-to-wake” approach, which examines the environmental impact of fuels and technologies from production to final use. They looked at everything from the manufacturing and transportation of fuels to their emissions when burned on ships. They also gathered data directly from a bulk carrier vessel in China that burns heavy fuel oil with a scrubber and low-sulfur fuel under similar conditions. The team analyzed emissions from the exhaust and samples of washwater discharged from the scrubbers, which is often a concern due to its potential toxicity.

Lead author Patricia Stathatou, an assistant professor at Georgia Tech, emphasized that a full lifecycle analysis is critical for understanding the true environmental impact. “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. She added that scrubbers, with a lifetime of about 20 years, have a minimal environmental footprint compared to the energy-intensive production of low-sulfur fuels.

Surprising Findings: Scrubbers Surpass Low-Sulfur Fuels in Several Areas

The results of the study were surprising. When the researchers considered the entire lifecycle, including the production of fuels and scrubbers, burning heavy fuel oil with scrubbers was found to be the least harmful option in terms of most environmental factors, such as greenhouse gas emissions, terrestrial acidification, and ozone formation.

“The claims about environmental hazards and policies to mitigate them should be backed by science,” said Stathatou. “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.”

Scrubbers: A Proven and Mature Technology

Marine scrubbers, which have been used for decades in land-based applications like power plants, are now widely deployed in the shipping industry. Scrubbers are typically large vertical tanks that use seawater to wash sulfur dioxide from the exhaust gases. The seawater reacts with the sulfur, converting it into sulfates, which are environmentally benign. The washwater is then released back into the ocean, where it is diluted by the vast expanse of seawater.

Despite concerns over the acidity and potential pollutants in the washwater, the study found that most chemical concentrations in the washwater were well below the limits set by environmental regulations, such as those from the U.S. Environmental Protection Agency and the European Union.

Scrubbers Meet International Standards

The researchers also tested the washwater for over 60 chemical parameters, including metals and hydrocarbons, and found that concentrations of harmful substances were generally well within safe levels. “Scrubbers reduce sulfur dioxide emissions by 97 percent, making them just as effective as low-sulfur fuels in terms of sulfur emissions,” said Scott Bergeron, managing director of Oldendorff Carriers, who co-authored the study.

A Call for Balanced Environmental Policies

This research has significant implications for future maritime environmental policies. As Stathatou points out, there is growing momentum toward alternative fuels, but it’s critical to assess the environmental impacts of these fuels in comparison to current technologies. “We must do our due diligence to compare them equally with existing solutions to see the costs and benefits,” she said.

The study’s findings could reshape policies governing the maritime industry, suggesting that scrubbers may offer a more sustainable path forward than previously thought. The research team hopes this will prompt a more science-driven approach to reducing shipping’s environmental footprint.

The study, which includes contributions from researchers at MIT, Georgia Tech, and Oldendorff Carriers, highlights the importance of scientific analysis in shaping policies that reduce the environmental impact of global shipping. With over 5,800 vessels now using scrubbers worldwide, the technology is clearly making an impact, but questions around its long-term environmental effects are only just beginning to be answered.

Imagine diving into the ocean’s depths, descending further than the eye can see, into a cold, almost completely dark world where every movement feels like a gamble. For some of the ocean’s most formidable predators—like tuna and swordfish—this is no mere adventure; it’s a necessity. A new study reveals that these apex hunters are making regular, long-distance plunges into the twilight zone, a mysterious and dark layer of the ocean, to fill their stomachs. And what they’re finding there could change the way we think about ocean ecosystems and the future of commercial fishing.

For decades, oceanographers knew that large fish like tuna and swordfish occasionally ventured into the depths of the ocean, but the purpose of these dives remained unclear. Were these predators hunting for food, or were they just exploring? A recent breakthrough by MIT oceanographers has answered that question—and the results are more astonishing than anyone could have imagined.

In a pioneering study published in ICES Journal of Marine Science, an MIT team led by Ciara Willis has found that these fish are relying heavily on the twilight zone, a dark, cold layer between 200 and 1,000 meters below the surface, for as much as 60% of their diet. This discovery reveals a much deeper connection to this enigmatic zone than scientists previously realized.

“We’ve known for a long time that these fish and many other predators feed on twilight zone prey,” says Willis, a postdoc at the Woods Hole Oceanographic Institution, in a press statement. “But the extent to which they rely on this deep-sea food web for their diet has been unclear.”

The Hidden Feast

The twilight zone—often overlooked in marine research—has been gaining attention for its rich ecosystem. It’s a vast, underexplored region teeming with strange creatures, from tiny lanternfish to massive squid, all adapted to live without sunlight. While the surface waters are teeming with life, they offer less concentrated food for large predators. By contrast, the twilight zone is like a dense buffet, providing predators like bigeye tuna, yellowfin tuna, and swordfish a more reliable food source.

“This is a really understudied region of the ocean, and it’s filled with all these fantastic, weird animals,” Willis says. “We call it the ‘deep ocean buffet.’”

The deep sea creatures in the twilight zone have evolved to migrate vertically—swimming to the surface to feed at night and returning to the depths by day to avoid predators. For the big predators of the open ocean, this behavior creates a prime opportunity to feast. Bigeye tuna, yellowfin tuna, and swordfish dive regularly into these depths to hunt. But until recently, scientists didn’t know just how important this food source truly was.

“We saw the bigeye tuna were far and away the most consistent in where they got their food from,” Willis explains. “The swordfish and yellowfin tuna were more variable, meaning that if large-scale fishing were to target the twilight zone, bigeye tuna might be the ones most at risk.”

The Price of Overfishing the Deep

This discovery comes at a critical time. The growing interest in commercial fishing in the twilight zone, despite its often unpalatable fish species, has raised alarms. These creatures are increasingly being harvested for fishmeal and fish oil, products commonly used in animal feed and other industries. However, as researchers point out, this could have dire consequences for tuna and swordfish populations.

“There is increasing interest in commercial fishing in the ocean’s twilight zone,” says Willis. “If we start heavily fishing that layer of the ocean, our study suggests that could have profound implications for tuna and swordfish, which are highly reliant on this region.”

The team’s findings underscore the need for careful management of the twilight zone’s resources. Given that tuna and swordfish rely on this zone for up to 60% of their food, disruptions to the ecosystem here could have cascading effects on the open ocean and the global fishing industry.

“Predatory fish like tunas have a 50% reliance on twilight zone food webs,” Willis warns. “If we start heavily fishing in that region, it could lead to uncertainty around the profitability of tuna fisheries.”

As the twilight zone becomes a target for increasing commercial interest, scientists are calling for greater caution in how we approach the deep ocean’s complex food web. What lies in the shadows of the ocean’s depths may be far more crucial to our marine ecosystems than anyone has realized.

The remote mountain regions of the world, once pristine and largely untouched by human development, are becoming increasingly perilous for wildlife. As road networks extend into these rugged terrains, endangered and vulnerable species are facing an ominous new threat—roadkill.

Species such as the African wild dog (endangered), lions and leopards (both vulnerable), elephants (endangered), and honey badgers (near threatened) are at grave risk, according to new research presented by Professor Aliza le Roux, Assistant Dean of the Faculty of Natural and Agricultural Sciences at the University of the Free State. These animals, many classified by the International Union for Conservation of Nature (IUCN) as at risk, face an increasingly perilous existence.

In her compelling presentation at the Southern African Mountain Conference (SAMC2025), she revealed the stark reality that these once-untouched ecosystems are now being invaded by expanding roads that are leading to more wildlife-vehicle collisions, many of them fatal.

“Wildlife in these regions is incredibly vulnerable, and as roads push deeper into mountainous areas, we’re seeing a dramatic rise in roadkill incidents,” said Prof Le Roux. “Among the casualties, we’re finding not just mammals, but also critically endangered birds like the hooded vulture and the steppe eagle.”

The conference, which brought together leading researchers, policymakers, and environmental experts, focused on the dire state of mountain ecosystems, communities, and biodiversity. UNESCO, in partnership with the University of the Free State’s Afromontane Research Unit, the African Mountain Research Foundation, and the Global Mountain Safeguard Research Programme, facilitated the gathering.

For the past several months, Prof Le Roux and her colleagues—Dr Katlego Mashiane, a lecturer at the UFS Department of Geography, and Dr Clara Grilo of the BIOPOLIS project in Portugal—have scoured decades’ worth of data on roadkill, analyzing published papers from 1971 to 2024. The findings were both alarming and illuminating, revealing that the majority of roadkill data available for Africa has emerged only in the 21st century.

A Growing Threat to Wildlife

In mountainous regions, amphibians were found to be the most frequent roadkill victims, while mammals, particularly those most vulnerable to extinction, were most often killed in the low-lying regions. In some high-elevation mountains, nearly 8% of mammals killed on the roads were species classified as endangered or vulnerable. Even more alarming, the roadkill rate in these regions continues to rise as human development accelerates.

“Many smaller species—those weighing less than 1 kilogram—fall victim to vehicles simply because we don’t see them. However, larger mammals, such as elephants or antelope, are often noticed only after the crash,” Prof Le Roux explained. “When these large animals are killed, it’s not just a loss for the species; it’s a loss for us too, as these collisions can cause significant damage to vehicles and pose a danger to human drivers.”

The risk is compounded by unpredictable weather and treacherous mountain roads, where sudden changes in terrain and visibility make it difficult for both drivers and wildlife to react in time. Prof Le Roux and her team noted that the ruggedness of these areas makes it harder for animals to detect oncoming vehicles, raising the likelihood of accidents.

“These regions are already dangerous for drivers, but for wildlife, the roads are a death trap,” Prof Le Roux said. “The increased number of vehicles, combined with better-paved roads, is putting more and more wildlife at risk.”

Using sophisticated tools like Google Earth Engine’s geospatial platform, the researchers analyzed data from a variety of terrains, classifying areas by elevation. High-elevation mountains, defined as regions above 2,000 meters, moderate elevations between 1,500 and 2,000 meters, and lowland areas below 1,500 meters were all found to have significant roadkill rates, particularly among mammals and birds of conservation concern.

Data Gaps and Underreporting

The study highlighted a critical issue: limited data. Despite the alarming trends, the lack of comprehensive, systematic data across much of the African continent has left major gaps in understanding the full scope of the roadkill crisis. Data was available for only 10 countries, and much of the information consisted of ‘snapshots’ rather than long-term, continuous monitoring.

“There is so much we don’t know about the true scale of this issue across Africa, particularly in the central and western regions,” Prof Le Roux lamented. “What we do know is that these collisions are happening in areas that are home to species that exist nowhere else. We cannot afford to ignore the threat to biodiversity in these mountain ecosystems.”

As the push for infrastructure development grows, the consequences for wildlife have never been clearer. The growing mortality rate among vulnerable species, many of which are already at risk of extinction, could result in devastating losses for biodiversity.

Prof Le Roux and her colleagues urge immediate action to mitigate these risks, calling for more comprehensive data collection, better road planning, and the implementation of wildlife corridors to safeguard these precious ecosystems.

“We must recognize that as we expand our roads into these high-risk areas, we’re also taking a toll on the very creatures that make these mountains so unique,” Prof Le Roux said, emphasizing the urgent need for a balanced approach to development and conservation.

As the conference came to a close, one message echoed throughout the halls: The future of Africa’s mountainous wildlife depends on the actions we take now. The clock is ticking, and the road ahead may be the final journey for some of the continent’s most endangered creatures.