Reducing carbon emissions from small-scale combustion systems, such as boilers and other industrial equipment, is a key step towards building a more sustainable, carbon-neutral future. Boilers are widely used across various industries for essential processes like heating, steam generation, and power production, making them significant contributors to greenhouse gas emissions.

Boilers are generally quite efficient. As a result, it is difficult to reduce CO₂ emissions simply by improving the combustion efficiency. Therefore, researchers are exploring alternative approaches to mitigating the environmental impact of CO₂ emissions from boilers. One promising strategy to this end is to capture the CO₂ emitted from these systems and convert it into a useful product, such as methane.

To implement this strategy, a specific type of membrane reactor, called the distributor-type membrane reactor (DMR), is needed that can facilitate chemical reactions as well as separate gases. While DMRs are used in certain industries, their application for converting CO₂ into methane, especially in small-scale systems like boilers, has remained relatively unexplored.

This research gap was addressed by a group of researchers from Japan and Poland, who were led by Professor Mikihiro Nomura from Shibaura Institute of Technology in Japan and Prof. Grzegorz Brus from AGH University of Science and Technology in Poland. Their findings were published online on 17 April 2024 in Volume 82 of the Journal of CO2 Utilization.

The team conducted a two-pronged approach to the problem through numerical simulations and experimental studies to optimize the reactor designs for efficient conversion of CO₂ from small boilers into methane. In their simulation, the team modeled how gases flow and react under different conditions. In turn, this enabled them to minimize the temperature variations, ensuring that energy consumption is optimized while methane production remains dependable.

The team further found that, unlike traditional methods that channel gases into a single location, a distributed feed design could spread the gases out into the reactor instead of sending them in from one place. This, in turn, results in a better distribution of CO₂ throughout the membrane, preventing any location from overheating. “This DMR design helped us reduce temperature increments by about 300 degrees compared to the traditional packed bed reactor,” explains Prof. Nomura.

Beyond the distributed feed design, the researchers also explored other factors influencing the reactors efficiency and discovered that one key variable was the CO₂ concentration in the mixture. Changing the amount of CO₂ in the mixture affected how well the reaction worked. “When the CO₂ concentration was around 15%, similar to what comes out of the boilers, the reactor was much better at producing methane. In fact, it could produce about 1.5 times more methane compared to a regular reactor that only had pure CO₂ to work with,” highlights Prof. Nomura.

Additionally, the team investigated the impact of reactor size, finding that increasing the size of the reactor facilitated the availability of hydrogen for the reaction. There was, however, a tradeoff to be considered as the benefit of higher hydrogen availability required careful temperature management to avoid overheating.

The study thus presents a promising solution to the problem of tackling a major source of greenhouse gas emissions. By utilizing a DMR, low-concentration CO₂ emissions can be successfully converted into usable methane fuel. The benefits gained thereof are not limited to methanation alone but can also be applied to other reactions, making this method a versatile tool for efficient CO₂ utilization even for households and small factories.

Researchers from Chiba University have discovered that snails living in downstream tidal areas have biological rhythms synchronized with the tidal cycles, unlike those in nontidal regions. This observation raises the question of whether circatidal rhythms develop due to differences in habitat or are caused by genetic variations between the populations.

Building on their previous findings, Associate Professor Yuma Takahashi, along with Dr. Takumi Yokomizo from Chiba University (at the time of the study, and currently a post-doc researcher at the Center for Ecological Research, Kyoto University), revealed that freshwater snails living in tidal environments gradually adjust their biological rhythms to synchronize with the tidal cycles. The study published in the journal Heredity on March 27, 2024, offers insights into the adaptability and potential divergence of biological rhythms in response to tidal environments.

“This study revealed genetic and non-genetic changes in biological rhythms while adapting to tidal environments in a freshwater snail. This result could lead to an understanding of the role of biological clocks in the adaptation to rhythmic environment, which is one of the most important issues in chronobiology,” says Dr. Takahashi. The researchers collected freshwater snails (Semisulcospira reiniana) from tidal and nontidal areas along the Kiso River in Japan, 20 km apart. Snails were divided into two groups: one exposed to a regular 24-hour light-dark cycle, while the other experienced a simulated 12-hour tidal cycle, alternating between submersion during high tide and exposure to air during low tide.

Following a 4-week entrainment period, the researchers analyzed the behavior and genetic expression patterns of the snails in darkness at a constant temperature of 23°C. Among the snails from non-tidal areas, there were no significant differences in the intensity of the circadian and circatidal rhythms between the two groups. However, snails from tidal areas that were exposed to the simulated tidal cycle showed stronger circatidal rhythms compared to the control group. Interestingly, both the tidal and non-tidal populations exposed to the simulated tide showed an increase in the number of circatidal oscillating genes and a decrease in the circadian oscillating genes (genes that fluctuate in activity in tune with the tidal and diurnal cycle, respectively). Snails that had already adapted to the tidal cycles in the rivers in their early life had a greater number of circatidal oscillating genes compared to the nontidal population.

These results imply that the expression rhythms of genes controlled by the biological clock are sensitive to environmental changes, and can be influenced by genetic changes that result from environmental adaptation. “Our study focused on the flexibility of biological clocks and found their potential to change biological rhythms according to dominant environmental cycles,” says Dr. Takahashi.

Disruptions to biological rhythms can negatively impact various physiological processes. The findings of this study may enhance our understanding of how organisms adapt to changing environmental conditions and prove valuable in the treatment of chronobiological diseases in the future.

By analyzing the dynamics of 12 back-to-back explosions that happened in 2018, researchers describe a new type of volcanic eruption mechanism. The explosions were driven by sudden pressure increases as the ground collapsed, which blasted plumes of rock fragments and hot gas into the air, much like a classic stomp-rocket toy.

Researchers from the University of Oregon, United States Geological Survey and China’s Sichuan University report their findings in a paper published May 27 in Nature Geoscience.

The particular string of explosions at the summit of Kīlauea was part of a sequence of events that included lava flows erupting from lower on the flank of the volcano. Those lava flows destroyed thousands of homes and displaced residents on the Island of Hawai’i for months.

Understanding exactly what happened in past volcanic eruptions, colloquially called “hindcasting,” allows volcanologists to make better forecasts about future eruptions and give more accurate warnings to people in an eruption’s path.

For the most part, explosive volcanic eruptions are either primarily driven by rising magma, vaporized groundwater, or some combination of the two, according to Josh Crozier, who did this research as a doctoral student at the UO. But these eruptions didn’t quite fit the mold.

“These eruptions are quite interesting in that they don’t really seem to involve either of those,” Crozier said. “The eruptive material contained very little that looked like fresh magma that was blasted out, but there’s no evidence for significant groundwater being involved, either.”

The Hawaiian Volcano Observatory, part of the U.S. Geological Survey, keeps close tabs on Kīlauea. The volcano is covered with scientific instruments, from ground sensors that measure the shaking of the earth to tools that analyze the gases released from the volcano.

“A cool thing about these eruptions is that there were a bunch of them in sequence that were remarkably similar; that’s relatively unusual,” said Leif Karlstrom, a volcanologist at the UO. “Typically, volcanic eruptions don’t happen with as much regularity.”

So the team had more data than usual to work with, and they could dig deeper into the specific dynamics of the eruptions.

Putting all that data into a variety of atmospheric and subsurface models, the scientists pieced together a new story about what happened on Kīlauea during the string of events in 2018.

Before each explosion at the summit, magma was slowly draining from an underground reservoir. (This magma was feeding lava flows 40 kilometers away, on the eastern flank of the volcano.) As the reservoir depleted, the ground above it — the crater within the caldera at the volcano’s summit — suddenly collapsed.

That quickly increased the pressure in the reservoir. And because there was a pocket of accumulated magmatic gas sitting at the top of this reservoir, the pressure increase squeezed the magmatic gas and bits of rubble through a conduit and blasted them out of a vent in Kīlauea’s crater.

The researchers compare the eruption dynamic to a stomp-rocket toy, where stepping on an air bag connected to a hose launches a projectile into the air.

“The ‘stomp’ is this whole kilometer-thick chunk of rock dropping down, pressurizing the pocket, and then forcing material directly up,” Crozier said. And the ‘rocket’ is, of course, the gas and rocks erupting from the volcano.

Caldera collapse is fairly common, Crozier notes. So while this is the first time scientists have specifically spelled out this specific stomp-rocket mechanism, it’s probably not the only time it’s occurred.

The study was able to link geophysical observations to the properties of the volcanic plume in the atmosphere.

“This link is very rare,” said Joe Dufek, a volcanologist at the UO. “It points to new ways for us to observe eruptions and to combine sensor measurements with computer simulations to better assess hazards from eruptions.”

The fact that this was a series of smaller eruptions may have made it easier to see the underlying mechanism, Dufek said. Other complex processes weren’t overshadowing the stomp-rocket component.

But that’s not to say that Kīlauea is simple. A typical textbook drawing of a volcano shows magma moving upwards through chambers at different depths. But it’s rarely that straightforward, and a volcano like Kīlauea, decked out in scientific instruments, provides an opportunity to dig into the details.

“This is an example, and there’s an increasing number of these, where the pathways of magma ascent are quite geometrically complex,” Karlstrom said. “It gives us a much more nuanced picture of what volcanic plumbing systems look like.”