Microbe dietary preferences influence the effectiveness of carbon sequestration in the deep ocean

The movement of carbon dioxide (CO2) from the surface of the ocean, where it is in active contact with the atmosphere, to the deep ocean, where it can be sequestered away for decades, centuries, or longer, depends on a number of seemingly small processes.

One of these key microscale processes is the dietary preferences of bacteria that feed on organic molecules called lipids, according to a journal article, "Microbial dietary preference and interactions affect the export of lipids to the deep ocean," published in Science.

"In our study, we found incredible variation in what the different microbes preferred to digest. Bacteria seem to have very distinct diet preferences for different lipid molecules. This has real implications for understanding carbon sequestration and the biological carbon pump," said journal article co-author Benjamin Van Mooy, a senior scientist in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI). "This study used state-of-the-art methods to link the molecular composition of the sinking biomass with its rates of degradation, which we were able to link to the dietary preferences of bacteria." The biological carbon pump is a process where biomass sinks from the ocean surface to the deep ocean.

About 5 to 30% of surface ocean particulate organic matter is composed of lipids, which are carbon-rich fatty acid biomolecules that microbes use for energy storage and cellular functions. As the organic matter sinks to the deep sea, diverse communities of resident microbes degrade and make use of the lipids, exerting an important control on global CO2 concentrations. Understanding this process is vital to improve our ability to forecast global carbon fluxes in changing ocean regimes. Geographic areas where more lipids reach the deep ocean undegraded could be hotspots for natural carbon sequestration.

"Bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders," the article states. "Using synthetic communities composed of isolates with distinct dietary preferences, we showed that lipid degradation is modulated by microbial interactions. A particle export model incorporating these dynamics indicates that metabolic specialization and community dynamics may influence lipid transport efficiency in the ocean's mesopelagic zone." The mesopelagic zone extends about 200-1000 meters below the ocean surface.

"I was thrilled to see how much there is to learn about the functioning of the ocean by combining two technologies- high-end chemical analysis and microscale imaging-that have historically never been used together," said co-author Roman Stocker, professor at the Institute of Environment Engineering, Department of Civil, Environmental and Geomatic Engineering, ETH Zurich, Switzerland, "I believe that work at the interface between the exciting technologies we now have available in microbial oceanography will continue to yield important insights into how microbes shape our oceans, now and into the future."

"Scientists are starting to understand that lipids in the ocean can vary significantly depending on different environments, such as the coast versus the open ocean, and the season," said Van Mooy. "With this information, researchers can start to consider whether there are places in the ocean where lipids sink and are sequestered very efficiently, while there may be other locations where lipids are barely sequestered at all or are very inefficiently sequestered."

"What excites me about this paper is that it shows bacteria are not just eating any type of lipid, but are very specialized and, like us, have specific food preferences," said article co-author Lars Behrendt, associate professor and SciLifeLab fellow at the Science for Life Laboratory, Department of Organismal Biology, Uppsala University, Sweden. "This changes how we think about how microorganisms consume food in their natural environment and how they might help each other or compete for the same resource. It also supports the idea that combinations of bacteria better break down specific compounds, including lipids, or to achieve other desired functions."

In addition to studying specific bacteria species in isolation, the researchers also looked at how dietary preference affects degradation rates by multispecies communities of bacteria, which they stated is ecologically more relevant than species in isolation. The researchers found that simple synthetic co-cultures exhibited different degradation rates and delay times when compared to monocultures. The researchers also noted that the degradation of particulate organic matter in the natural environment is even more complex than what is described in the study.

"Phytoplankton are the main reason the ocean is one of the biggest carbon sinks. These microscopic organisms play a huge role in the world's carbon cycle -- absorbing about as much carbon as all the plants on land combined," said co-author Uria Alcolombri, senior lecturer, Alexander Silberman Institute of Life Sciences, Department of Plant and Environmental Sciences, The Hebrew University of Jerusalem, Israel. "It's fascinating that we can study tiny microbial processes under the microscope while uncovering the biological factors that regulate this massive 'digestive system' of the ocean."

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'Gap' in carbon removal: Countries' plans to remove CO2 not enough

New research involving the University of East Anglia (UEA) suggests that countries' current plans to remove CO2 from the atmosphere will not be enough to comply with the 1.5 ºC warming limit set out under the Paris Agreement.

Since 2010, the United Nations environmental organisation UNEP has taken an annual measurement of the emissions gap -- the difference between countries' climate protection pledges and what is necessary to limit global heating to 1.5 ºC, or at least below 2 ºC.

The UNEP Emissions Gap Reports are clear: climate policy needs more ambition. This new study now explicitly applies this analytical concept to carbon dioxide removal (CDR) -- the removal of the most important greenhouse gas, CO2, from the atmosphere.

The study, published today in the journal Nature Climate Change, was led by the Berlin-based Mercator Research Institute on Global Commons and Climate Change (MCC) and involved an international team of scientists.

"In the Emissions Gap Reports, carbon removals are only accounted for indirectly," said lead author Dr William Lamb, of the MCC Applied Sustainability Science working group.

"After all, the usual benchmark for climate protection pledges is net emissions, ie emissions minus removals. We are now making transparent the specific ambition gap in scaling up removals.

"This planetary waste management will soon place completely new requirements on policymakers and may even become a central pillar of climate protection in the second half of the century."

Co-author Dr Naomi Vaughan, of the Tyndall Centre for Climate Change Research at UEA, added: "Carbon dioxide removal methods have a small but vital role to play in achieving net zero and limiting the impacts of climate change.

"Our analysis shows that countries need more awareness, ambition and action on scaling up CDR methods together with deep emissions reductions to achieve the aspirations of the Paris Agreement."

According to the study, if national targets are fully implemented, annual human-induced carbon removals could increase by a maximum of 0.5 gigatonnes of CO2 (500 million tonnes) by 2030, and by a maximum of 1.9 gigatonnes by 2050.

This contrasts with the 5.1 gigatonne increase required in a 'focus scenario', which the research team depicts as typical from the latest Intergovernmental Panel on Climate Change (IPCC) assessment report.

There, global heating, calculated over the entire course of this century, is limited to 1.5 ºC, and a particularly rapid expansion of renewable energies and reduction of fossil emissions is depicted as the core climate protection strategy.

But, the focus scenario still relies on scaling up carbon removals. The gap for the year 2050 is therefore at least 3.2 gigatonnes of CO2 (5.1 minus a maximum of 1.9).

An alternative focus scenario, also derived from the IPCC, assumes a significant reduction in global energy demand, due to politically initiated behaviour changes as the core element of climate protection strategy.

Here, carbon removals would increase by a more modest amount: 2.5 gigatonnes in 2050. Fully implemented national targets would be close to sufficient when compared to this scenario, with a gap in 2050 of 0.4 gigatonnes.

The research team points out the problem of sustainability limits in scaling up carbon removals; for example, the associated land area demand will come to jeopardise biodiversity and food security. Nevertheless, there is still plenty of room for designing fair and sustainable land management policies.

In addition, novel carbon removal options, such as air filter systems, or 'enhanced rock weathering', have hardly been promoted by politicians to date.

They currently only remove 0.002 gigatonnes of CO2 per year from the atmosphere, compared to 3 gigatonnes through conventional options such as afforestation, and they are unlikely to significantly increase by 2030. According to the scenarios, they must become more prevalent than conventional options by 2010.

Since only 40 countries have so far quantified their removal plans in their long-term low emissions development strategies, the study also draws on other national documents and best-guess assumptions.

"The calculation should certainly be refined," said Dr Lamb. "But our proposal using the focus scenarios further opens the discourse on how much carbon removal is necessary to meet the Paris Agreement.

"This much is clear: without a rapid reduction in emissions towards zero, across all sectors, the 1.5 ºC limit will not be met under any circumstances."

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Ice age climate analysis reduces worst-case warming expected from rising CO2

As carbon dioxide accumulates in the atmosphere, the Earth will get hotter. But exactly how much warming will result from a certain increase in CO2 is under study. The relationship between CO2 and warming, known as climate sensitivity, determines what future we should expect as CO2 levels continue to climb.

New research led by the University of Washington analyzes the most recent ice age, when a large swath of North America was covered in ice, to better understand the relationship between CO2 and global temperature. It finds that while most future warming estimates remain unchanged, the absolute worst-case scenario is unlikely.

The open-access study was published April 17 in Science Advances.

"The main contribution from our study is narrowing the estimate of climate sensitivity, improving our ability to make future warming projections," said lead author Vince Cooper, a UW doctoral student in atmospheric sciences. "By looking at how much colder Earth was in the ancient past with lower levels of greenhouse gases, we can estimate how much warmer the current climate will get with higher levels of greenhouse gases."

The new paper doesn't change the best-case warming scenario from doubling CO2 -- about 2 degrees Celsius average temperature increase worldwide -- or the most likely estimate, which is about 3 degrees Celsius. But it reduces the worst-case scenario for doubling of CO2 by a full degree, from 5 degrees Celsius to 4 degrees Celsius. (For reference, CO2 is currently at 425 ppm, or about 1.5 times preindustrial levels, and unless emissions drop is headed toward double preindustrial levels before the end of this century.)

As our planet heads toward a doubling of CO2, the authors caution that the recent decades are not a good predictor of the future under global warming. Shorter-term climate cycles and atmospheric pollution's effects are just some reasons that recent trends can't reliably predict the rest of this century.

"The spatial pattern of global warming in the most recent 40 years doesn't look like the long-term pattern we expect in the future -- the recent past is a bad analog for future global warming," said senior author Kyle Armour, a UW associate professor of atmospheric sciences and of oceanography.

Instead, the new study focused on a period 21,000 years ago, known as the Last Glacial Maximum, when Earth was on average 6 degrees Celsius cooler than today. Ice core records show that atmospheric CO2 then was less than half of today's levels, at about 190 parts per million.

"The paleoclimate record includes long periods that were on average much warmer or colder than the current climate, and we know that there were big climate forcings from ice sheets and greenhouse gases during those periods," Cooper said. "If we know roughly what the past temperature changes were and what caused them, then we know what to expect in the future."

Researchers including co-author Gregory Hakim, a UW professor of atmospheric sciences, have created new statistical modeling techniques that allow paleoclimate records to be assimilated into computer models of Earth's climate, similar to today's weather forecasting models. The result is more realistic temperature maps from previous millennia.

For the new study the authors combined prehistoric climate records -- including ocean sediments, ice cores, and preserved pollen -- with computer models of Earth's climate to simulate the weather of the Last Glacial Maximum. When much of North America was covered with ice, the ice sheet didn't just cool the planet by reflecting summer sunlight off the continents, as previous studies had considered.

By altering wind patterns and ocean currents, the ice sheet also caused the northern Pacific and Atlantic oceans to become especially cold and cloudy. Analysis in the new study shows that these cloud changes over the oceans compounded the glacier's global cooling effects by reflecting even more sunlight.

In short, the study shows that CO2 played a smaller role in setting ice age temperatures than previously estimated. The flipside is that the most dire predictions for warming from rising CO2 are less likely over coming decades.

"This paper allows us to produce more confident predictions because it really brings down the upper end of future warming, and says that the most extreme scenario is less likely," Armour said. "It doesn't really change the lower end, or the average estimate, which remain consistent with all the other lines of evidence."

Read more at Science Daily

38 trillion dollars in damages each year: World economy already committed to income reduction of 19 % due to climate change

Even if CO2 emissions were to be drastically cut down starting today, the world economy is already committed to an income reduction of 19 % until 2050 due to climate change, a new study published in Nature finds. These damages are six times larger than the mitigation costs needed to limit global warming to two degrees. Based on empirical data from more than 1,600 regions worldwide over the past 40 years, scientists at the Potsdam Institute for Climate Impact Research (PIK) assessed future impacts of changing climatic conditions on economic growth and their persistence.

"Strong income reductions are projected for the majority of regions, including North America and Europe, with South Asia and Africa being most strongly affected. These are caused by the impact of climate change on various aspects that are relevant for economic growth such as agricultural yields, labour productivity or infrastructure," says PIK scientist and first author of the study Maximilian Kotz. Overall, global annual damages are estimated to be at 38 trillion dollars, with a likely range of 19-59 trillion dollars in 2050. These damages mainly result from rising temperatures but also from changes in rainfall and temperature variability. Accounting for other weather extremes such as storms or wildfires could further raise them.

Huge economic costs also for the United States and European Union

"Our analysis shows that climate change will cause massive economic damages within the next 25 years in almost all countries around the world, also in highly-developed ones such as Germany, France and the United States," says PIK scientist Leonie Wenz who led the study. "These near-term damages are a result of our past emissions. We will need more adaptation efforts if we want to avoid at least some of them. And we have to cut down our emissions drastically and immediately -- if not, economic losses will become even bigger in the second half of the century, amounting to up to 60% on global average by 2100. This clearly shows that protecting our climate is much cheaper than not doing so, and that is without even considering non-economic impacts such as loss of life or biodiversity."

To date, global projections of economic damages caused by climate change typically focus on national impacts from average annual temperatures over long-time horizons. By including the latest empirical findings from climate impacts on economic growth in more than 1,600 subnational regions worldwide over the past 40 years and by focusing on the next 26 years, the researchers were able to project sub-national damages from temperature and rainfall changes in great detail across time and space all the while reducing the large uncertainties associated with long-term projections. The scientists combined empirical models with state-of-the-art climate simulations (CMIP-6). Importantly, they also assessed how persistently climate impacts have affected the economy in the past and took this into account as well.

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CO2 worsens wildfires by helping plants grow

By fueling the growth of plants that become kindling, carbon dioxide is driving an increase in the severity and frequency of wildfires, according to a UC Riverside study.

The worldwide surge in wildfires over the past decade is often attributed to the hotter, drier conditions of climate change. However, the study found that the effect of increasing levels of carbon dioxide (CO2) on plants may be a bigger factor.

"It's not because it's hotter that things are burning, it's because there's more fuel, in the form of plants," said UCR doctoral student in Earth and planetary sciences and study author James Gomez.

This conclusion, and a description of the eight model experiments that produced it, have been published in Communications Earth & Environment.

To convert light into food in a process called photosynthesis, plants require CO2. Burning fossil fuels for heat, electricity, and transportation is adding increasing levels of CO2 into the atmosphere. Plants use the extra CO2 to make carbohydrates that help them grow, leading to an increase in biomass that burns.

Certainly, heat waves and drought occur more frequently in today's climate than they did 50 years ago. These are conditions that cause plants to wither and die. As they dry out and die, they burn more easily. The models accounted for these effects on plants, as well as for different types of plants, and for the increase in atmospheric CO2.

"Warming and drying are still important fire factors. These are the conditions that make the extra plant mass more flammable," said UCR professor of Earth sciences Robert Allen.

The models analyzed by the research team all assumed an idealized 1% per year increase in atmospheric CO2 concentrations since 1850. The idealized increase is meant to isolate the effects of the greenhouse gas on wildfire activity.

"These experiments are mainly looking at the contribution of CO2 to changes in wildfire activity," Gomez said. "That's the only thing that's changing in these models. Other drivers of climate change and wildfire activity do not change through time," Gomez said. "This includes, for example, changes in other greenhouse gases like methane, as well as changes in land use."

Seasons are still important factors in promoting wildfires, and fires still occur more often during "fire seasons." Dry, windy conditions help spread the flames faster, increasing the size of the burned area. "However, our study shows the increase in fires during hotter seasons is driven by fuel load rather than an increase in the number of what some consider 'fire weather' days," Gomez said.

This means megafires can often happen outside of what is considered fire season. As an example, the biggest wildfire on record in Texas, with more than a million acres burned, occurred this past February.

The researchers hope that their results inspire others to conduct additional studies of the factors driving the increase in wildfires. In addition, they hope that policymakers recognize the urgent need to decrease the amount of CO2 that people release into the atmosphere.

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Climate change will see Australia's soil emit CO2 and add to global warming

New Curtin University research has shown the warming climate will turn Australia's soil into a net emitter of carbon dioxide (CO2), unless action is taken.

Soil helps to keep the planet cool by absorbing carbon, however as the climate gets warmer its ability to retain carbon decreases -- and in some instances can start to release some carbon back into the air.

A global research team -- led by Professor Raphael Viscarra Rossel from Curtin's School of Molecular and Life Sciences -- predicted the changes in the amount of carbon in Australia's soil between now and the year 2100.

To do so, the team ran simulations using three different paths for society: an eco-focused 'sustainable' scenario, a 'middle-of-the-road' scenario and another which predicted a continued reliance on 'fossil-fuelled development'.

It found Australian soil will be a net emitter and could account for 8.3 per cent of Australia's total current emissions under the 'sustainable' scenario and more than 14 per cent by 2045 under the 'middle-of-the-road' and 'fossil-fuelled' scenarios.

By 2100, soil emissions under both scenarios are predicted to account for an even higher proportion of total emissions, but the predictions are more uncertain.

While some areas with arable farmland could continue to store carbon, the study found it would not be enough to offset the amounts of carbon lost from the soil in areas which are more sensitive to warmer weather, such as coastal regions and Australia's vast rangelands.

Australian soil holds an estimated 28 gigatons of carbon, 70 per cent of which is stored in these rangelands.

"Unless farming methods are further improved so farmland soils can continue to store carbon, any gains and benefit will likely decrease by 2045 and worsen in time, if the Earth continues to warm at its current rate," Professor Viscarra Rossel said.

"This means Australia's soil could release even more carbon into the air instead of storing it, which will in turn make climate change worse.

"If emissions continue at the current rate, the Earth's temperature is expected to reach 2 degrees above pre-industrial temperatures sometime this century, which is predicted to have dire consequences and

potentially catastrophic impacts for the planet."

Professor Viscarra Rossel said more sustainable pathways and improved management and conservation of soils were essential for Australia to meet its emissions reduction goals.

"Ensuring Australia's rangeland soils can maintain their carbon stocks is imperative: capturing and storing additional carbon will require interdisciplinary science, innovation, cultural awareness and effective policies" Professor Viscarra Rossel said.

"It will be challenging, given the rangelands' drier and more variable climate, its relatively sparse vegetation and other factors such as bushfires -- however, only a slight change over such large areas will make a positive difference.

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Scientists propose new method for tracking elusive origins of CO2 emissions from streams

A team of researchers from the University of Massachusetts Amherst that specializes in accounting for the carbon dioxide release by streams, rivers and lakes recently demonstrated that the chemical process known as "carbonate buffering" can account for the majority of emissions in highly alkaline waters. Furthermore, carbonate buffering distorts the most commonly used method of tracking the origins of CO2 in streams. The research, published in Global Biogeochemical Cycles, proposes a better method for tracking the origin of riverine CO2 emissions.

Inland waters, including streams, rivers and lakes, account for roughly 5.5 gigatons of CO2 emissions annually -- about 15% of what humans emit.

But current climate models have trouble accounting for this carbon, in part because, says Matthew Winnick, assistant professor of Earth, Geographic and Climate Sciences at UMass Amherst and the paper's lead author, much of this carbon seems to be produced cryptically, through carbonate buffering.

"The process is a little weird," says Winnick. "It acts as a kind of hidden reserve pool of CO2, replenishing carbon that is lost to the atmosphere, and ultimately increasing the amount of CO2 available for off-gassing."

To show how this hidden pool operates, Winnick and his co-author, then-UMass graduate student Brian Saccardi, looked to studies that focused on the carbon content of the oceans.

"Carbonate buffering is a really well-known phenomenon in the ocean," says Winnick, "and even though oceans work differently from inland waters, we were able to borrow the geochemical equations to build a series of models that could account for a wide range of river and stream conditions."

So what is carbonate buffering? It begins with CO2 -- which is everywhere: in the air, in the soil and in water.

When CO2 dissolves in water, it can react to form carbonic acid, which, through further reactions, can then become bicarbonate and carbonate.

This reaction can also run in reverse, which means that high levels of bicarbonate and carbonate can act as reserve pools of CO2, driving emissions.

This entire balance of CO2, water and carbonate is called "carbonate buffering," and the carbonate reserves can be emitted as a greenhouse gas from stream systems.

Indeed, Winnick and Saccardi found that this hidden pool can account for more than 60% of CO2 emissions under alkaline conditions.

There's yet another trick that carbonate buffering has up its sleeve.

In the era of global warming, it is critically important to know both how much carbon is being emitted overall and where this carbon is coming from.

"While we don't think stream emissions contribute to global warming, there is a big question about whether these emissions will change as climate warms, which could amplify warming in the future. To predict changes, we need to know where the CO2 is coming from," says Winnick.

But figuring out which molecule of CO2 came from which source is not a simple task.

To track carbon, especially carbon emitted by bodies of water, scientists often use carbon isotopes, or versions of carbon with different masses, which act as a sort of forensic signature that can indicate the carbon's origin.

However, Winnick and Saccardi discovered that isotope signals in streams are highly sensitive to carbonate buffering reactions.

"The primary way we use isotopes to track sources is through their relationship with CO2 concentrations, but carbonate buffering causes these relationships to break down," says Winnick.

This breakdown can point to the wrong carbon culprit if not properly accounted for.

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Surprising methane discovery in Yukon glaciers: 'Much more widespread than we thought'

Global melting is prying the lid off methane stocks, the extent of which we do not know. A young researcher from University of Copenhagen has discovered high concentrations of the powerful greenhouse gas in meltwater from three Canadian mountain glaciers, where it was not thought to exist -- adding new unknowns to the understanding of methane emissions from Earth's glaciated regions

The helicopter's rotor blades spin as its skillful pilot performs aerial acrobatics between the steep Yukon mountain sides where PhD student Sarah Elise Sapper is leading her first field expedition deep into the heart of the mountains of northwestern Canada. From the helicopter windows, her eyes fall on the jagged edge of the Donjek glacier: meltwater swirls out from beneath the ice like a whirlpool.

Soon after landing, it becomes apparent that Sarah has stumbled upon an unusual find on the first attempt. Seconds after starting up her portable methane analyzer it is clear that the air is enriched with methane and the culprit is soon found. Collecting a sample of meltwater, she measures concentrations of methane that far exceed expectations.

"We expected to find low values in the meltwater because it is believed that glacial methane emissions require larger ice masses such as vast ice sheets. But the result was quite the opposite. We measured concentrations up to 250 times higher than those in our atmosphere," explains Sarah Elise Sapper of the University of Copenhagen's Department of Geosciences and Natural Resource Management.

The field party lifted off and continued to two more mountain glaciers, Kluane and Dusty. And after measuring the methane in the meltwater of each of those two glaciers, the preliminary finding turned out to be more than an anomaly. Here too, measurements showed high methane concentrations. Somewhere beneath the ice, there are previously unknown sources of the gas.

Demonstrates possibility of widespread methane emissions

"The finding is surprising and raises several important questions within this area of research," says Associate Professor Jesper Riis Christiansen of the Department of Geosciences and Natural Resource Management.

Christiansen, the research article's co-author, believes that the finding demonstrates the possibility of methane being present beneath many of the world's glaciers, ones that have thus far been written off.

"When we suddenly see that even mountain glaciers, which are small in comparison with an ice sheet, are able to form and emit methane, it expands our basic understanding of carbon cycling in extreme environments on the planet. The formation and release of methane under ice is more comprehensive and much more widespread than we thought," he says.

Until now, the prevailing view has been that methane in meltwater could only be found in oxygen- free environments under large masses of ice like the Greenland Ice Sheet.

The researchers assume that the production of methane is biological and happens when an organic carbon source -- e.g., deposits from prehistoric marine organisms, soils, peat or forests -- is decomposed by microorganisms in the absence of oxygen, such as we know from wetlands. As such, it is surprising that the mountain glaciers emit methane.

"The meltwater from the surface of glaciers is oxygen-rich when it travels to the bottom of the ice. So we found it quite surprising that all this oxygen is used up somewhere along the way, so that oxygen-free environments form underneath these mountain glaciers. And even more surprising that it happens to such a degree, that microbes start producing methane and we can observe these high methane concentrations in the water flowing out at the glacier edges" states Sarah Elise Sapper.

"Sarah's findings change our basic understanding and send us back to the drawing board in relation to some of the key mechanisms at play," adds Jesper Riis Christiansen.

An uncertain role for the climate of the future

According to the researchers, the findings in Canada do not immediately spur an increased concern in relation to their effect on climate change. However that conclusion may be temporary.

"Methane plays a major role in warming our planet. The challenge with methane is that it is a super-potent greenhouse gas and increasing emissions will accelerate climate warming. From a global perspective, we can measure how much is emitted into the atmosphere and, roughly speaking, where the methane comes from, using the isotopes found in the atmospheric methane. And for now, the contribution of methane from ice-covered regions on our planet, including ice sheets and glaciers, isn't increasing," explains Jesper Riis Christiansen.

However, he emphasizes that the measurements cannot distinguish between methane from glaciated regions and methane from wetlands. Therefore, the numbers could be deceiving. And, the effect of melting remains unknown.

Jesper Riis Christiansen believes that the findings demand vigilance.

"The three sites Sarah measured were randomly selected due to the availability of a research station and helicopter, yet methane was found in all three. In itself, that is a good reason to better understand the area. There's too much that we don't know, and the melting glaciers expose unknown environments that have remained hidden for thousands of years. In reality, no one knows how emissions will behave," says Jesper Riis Christiansen.

He hopes that a better understanding of methane behaviour beneath glaciers will also help researchers better understand the mechanisms at play when wetlands release methane, and thereby contribute to the development of solutions to remove methane from the atmosphere through oxidation -- e.g., through the use of certain soil types.

A subglacial black box

The actual sources and locations of subglacial methane production actually remain somewhat of a mystery, hidden beneath ice masses of all sizes. Indeed, this methane can only be measured as the meltwater emerges from beneath the ice. And because it originates from large areas below the ice masses, this makes it difficult to access exactly where the production happens.

It is known to not originate from the ice itself, as concentrations both in the ice and meltwater atop it are lower than what is measured at the glacier edge. As such, the researchers believe that the methane must derive from a source beneath the ice. And the best theory, as mentioned, is that it is formed by microbes in oxygen-free pockets and then carried out with meltwater.

But this indirect knowledge of the source leaves a great deal of uncertainty about how much methane is hidden beneath the ice.

"It's a big black box under the ice -- and you could say that the meltwater is prying the lid off it. We do not know whether methane emissions from glacial areas will increase in the future with increased melting, or whether the 'lid' has already been opened to such a degree that the methane beneath the ice is actually being washed out with the meltwater," says Sarah Elise Sapper.

Methane and CO2 are different greenhouse gases

The half-life of methane in the atmosphere is 12 years.

CO2 has a much longer half-life, at roughly 1000 years.

On the other hand, methane is about 25 times more powerful as a greenhouse gas on a 100-year basis and a far more serious threat to global climate in the shorter term.

Due to greenhouse gas-driven climate change, researchers around the world are working to develop ways to capture or store CO2.

Similarly, solutions are being devised to limit the emission of -- or increase the oxidation of -- methane. Doing so requires more knowledge about how methane is formed.

Facts: Carbon circulation of methane and CO2

Biological traces from animal and plant material in the subsoil consist of carbon.

Within these environments, microorganisms have developed an ability to convert carbon into energy in a process where methane is created as a byproduct in the absence of oxygen (e.g. in beneath ice sheets or in wetlands).

However, if the methane is released into an oxygen-rich environment, it can effectively be oxidized and converted into CO2 by microbes. Wetlands play an important role in this process.

Once, in the atmosphere, methane reacts with other chemicals (hydroxyl radicals) which keep the concentrations down.

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Advanced artificial photosynthesis catalyst uses CO2 more efficiently to create biodegradable plastics

A research team from Osaka Metropolitan University that had previously succeeded in synthesizing fumaric acid using bicarbonate and pyruvic acid, and carbon dioxide collected directly from the gas phase as one of the raw materials, has now created a new photosensitizer and developed a new artificial photosynthesis technology, effectively doubling the yield of fumaric acid production compared to the previous method. The results of this research are expected to reduce carbon dioxide emissions and provide an innovative way to produce biodegradable plastics while reusing waste resources.

Amid growing global concern over climate change and plastic pollution, researchers at Osaka Metropolitan University are making great strides in the sustainable production of fumaric acid -- a component of biodegradable plastics such as polybutylene succinate, which is commonly used for food packaging.

The researchers have managed to efficiently produce fumaric acid, which is traditionally derived from petroleum, using renewable resources, carbon dioxide, and biomass-derived compounds.

In a previous study, a research team led by Professor Yutaka Amao of the Research Center for Artificial Photosynthesis at Osaka Metropolitan University demonstrated the synthesis of fumaric acid from bicarbonate and pyruvic acid, a biomass-derived compound, using solar energy.

They also succeeded in producing fumaric acid using carbon dioxide obtained directly from the gas phase as a raw material.

However, the yield in the production of fumaric acid remained low.

In their latest research, published in Dalton Transactions, the researchers have now developed a new photosensitizer and further advanced an artificial photosynthesis technique that doubles the yield of fumaric acid compared to conventional methods.

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Newly discovered carbon monoxide-runaway gap can help identify habitable exoplanets

A carbon monoxide (CO)-runaway gap identified in the atmospheres of Earth-like planets by researchers at Tokyo Tech can help expand the search for habitable planets. This gap, identified through atmospheric modeling, is an indicator of a CO-rich atmosphere on Earth-like planets orbiting Sun-like stars. CO is an important compound for the formation of prebiotic organic compounds, which are building blocks for more complex molecules for the formation of life.

The search for habitable exoplanets involves looking for planets with similar conditions to the Earth, such as liquid water, a suitable temperature range and atmospheric conditions.

One crucial factor is the planet's position in the habitable zone, the region around a star where liquid water could potentially exist on the planet's surface.

NASA's Kepler telescope, launched in 2009, revealed that 20-50% of visible stars may host such habitable Earth-sized rocky planets.

However, the presence of liquid water alone does not guarantee a planet's habitability.

On Earth, carbon compounds such as carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) played a crucial role in shaping the climate and biogeochemistry and could have contributed to the emergence of life.

Taking this into consideration, a recent study by Associate Professor Kazumi Ozaki from Tokyo Institute of Technology, along with Associate Researcher Yasuto Watanabe from The University of Tokyo, aims to expand the search for habitable planets.

Published in the Astrophysical Journal on 10 January 2024, the researchers used atmospheric modeling to identify conditions that could result in a CO-rich atmosphere on Earth-like planets that orbit sun-like (F-, G-, and K-type) stars.

This phenomenon, known as CO runaway, is suggested by atmospheric models to have possibly occurred in early planetary atmospheres, potentially favoring the emergence of life.

"The possibility of CO runaway is critical in resolving the fundamental problem regarding the origin of life on Earth because various organic compounds suitable for the prebiotic chemistry are more likely to form in a CO-rich atmosphere than in a CO2-rich atmosphere," explains Dr. Ozaki.

The researchers modeled the CO cycle between the atmosphere and the oceans, considering the various sources of CO production, its transport mechanisms and the processes involved in its removal.

The photolysis of CO2, in which CO2 breaks down into CO when exposed to light, was considered the primary source of CO. Additional sources included photochemical reactions in the atmosphere, emissions from volcanic gases, and the hydrothermal decomposition of formaldehyde (H2CO) in the ocean.

The removal of CO from the atmosphere primarily occurred through its reaction with hydroxyl (OH) radicals formed due to the photolysis of water vapor, and to a lesser extent, by deposition to the planet's surface.

The researchers found that a CO runaway occurs when the CO production surpasses the removal by OH radicals.

This can occur due to higher CO2 levels or the presence of reducing gases from volcanoes which compete for the OH radicals.

At a temperature of 277 K, conditions for CO runaway are met when the partial pressure of CO2 exceeds 0.2 bar.

However, at higher temperatures (300 K), a CO runaway needs even higher CO2 and volcanic gas levels due to increased water vapor in the atmosphere, which is a major source of OH radicals.

Once initiated, the CO levels in the atmosphere are limited only by surface deposition, where CO is deposited onto the planet's surface.

Notably, the changes in the CO, CO2 and CH4 levels before and after the runaway effect led to a gap reflected in the phase space defined by the ratios of their partial pressures (pCO/pCO2 and pCH4/pCO2). "Our results suggest that this CO-runaway gap is a general feature of Earth-like lifeless planets orbiting Sun-like stars, providing insights into the characteristics and potential habitability of exoplanets," says Dr. Ozaki.

Read more at Science Daily

Understanding how soil traps carbon

When carbon molecules from plants enter the soil, they hit a definitive fork in the road.

Either the carbon gets trapped in the soil for days or even years, where it is effectively sequestered from immediately entering the atmosphere. Or it feeds microbes, which then respire carbon dioxide (CO2) into the ever-warming environment.

In a new study, Northwestern University researchers determined the factors that could tip plant-based organic matter in one direction or the other.

By combining laboratory experiments and molecular modeling, researchers examined interactions between organic carbon biomolecules and a type of clay minerals known for trapping organic matter in soil. They found that electrostatic charges, structural features of carbon molecules, surrounding metal nutrients in soil and competition among molecules all play major roles in soil's ability (or inability) to trap carbon.

The new findings could help researchers predict which soil chemistries are most favorable for trapping carbon -- potentially leading to soil-based solutions for slowing human-caused climate change.

The research will be published on Feb. 9 in the Proceedings of the National Academy of Sciences.

"The amount of organic carbon stored in soil is about ten times the amount of carbon in the atmosphere," said Northwestern's Ludmilla Aristilde, the study's senior author. "If this enormous reservoir is perturbed, it would have substantial ripple effects. There are many efforts to keep carbon trapped to prevent it from entering the atmosphere. If we want to do that, then we first must understand the mechanisms at play."

An expert in the dynamics of organics in environmental processes, Aristilde is an associate professor of civil and environmental engineering at Northwestern's McCormick School of Engineering. Jiaxing Wang, a Ph.D. student in Aristilde's laboratory, is the paper's first author. Rebecca Wilson, an undergraduate student at Northwestern, is the paper's second author.

Common clay

Holding 2,500 billion tons of sequestered carbon, soil is one of Earth's largest carbon sinks -- second only to the ocean. But even though soil is all around us, researchers are only just beginning to understand how it locks in carbon to sequester it from the carbon cycle.

To investigate this process, Aristilde and her team looked to smectite clay, a type of clay mineral known to sequester carbon in natural soils. Then, they examined how the clay mineral's surface bonded to ten different biomolecules -- including amino acids, sugars related cellulose and phenolic acids related to lignin -- with varying chemistry and structures.

"We decided to study this clay mineral because it's everywhere," Aristilde said. "Nearly all soils have clay minerals. Also, clays are prevalent in semi-arid and temperate climates -- regions that we know will be affected by climate change."

Opposites attract

Aristilde and her team first looked at interactions between clay minerals and individual biomolecules. Because clay minerals are negatively charged, biomolecules with positively charged components (lysine, histidine and threonine) experienced the strongest binding. But, interestingly, this binding was not solely determined by electrostatic charges. Using 3D computational modeling, the researchers found that the structure of the biomolecules also played a role.

"There are instances where two molecules are both positively charged, yet one has a better interaction with the clay than the other," Aristilde said. "It's because the structural features of the binding are also important. A molecule has to be flexible enough to adopt a structural arrangement that can position itself in a way that aligns its positively charged components with the clay. The lysine, for example, has a long arm with a positive charge that it can use to anchor itself."

A little help from friends

Following this logic, one might assume that negatively charged biomolecules were unable to bind to the clay. But Aristilde and her team discovered that surrounding, natural metal nutrients could intervene. Positively charged metals, such as magnesium and calcium, formed a bridge between the negatively charged biomolecules and clay minerals to create a bond.

"Even with a biomolecule that wouldn't normally bind to the clay, we saw a significant increase in binding when magnesium was there," Aristilde said. "So, natural metal constituents in the soil can facilitate carbon trapping. Although this is a widely reported phenomenon, we shed light on the structures and mechanisms."

Mix and mingle

When studying interactions between individual biomolecules and clay minerals, the researchers found binding was predictable and straightforward. To attain information more closely aligned with real-world environments, Aristilde and her team mixed the different biomolecules together.

"We know different types of biomolecules in the environment exists together," Aristilde said. "So, we also performed experiments with a mixture of biomolecules."

Although the researchers initially thought the biomolecules would compete with one another to interact with the clay, they instead discovered unexpected behaviors. In a surprising twist, even positively charged biomolecules with flexible structures were inhibited from binding to the clay minerals. While they easily bonded to the clay when alone, the biomolecules' urges to bond with one another appears to supersede their attractions to the clay.

"This has not been shown before," Aristilde said. "The energy of attraction between two biomolecules was actually higher than the energy of attraction of a biomolecule to the clay. That led to a decrease in adsorption. It changes the way we think about how molecules compete on the surface. They aren't just competing for binding sites on the surface. They can actually attract each other."

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Greenhouse gas repurposed

Cutting-edge University of Auckland research converted waste carbon dioxide into a potential precursor for chemicals and carbon-free fuel.

Dr Ziyun Wang's researchers in the School of Chemical Sciences, in collaboration with researchers at Chinese institutions, have demonstrated a method for turning CO2 into formic acid, reported in the journal Nature.

In benchtop experiments, a catalyst made from waste lead-acid batteries enabled a transformation which hadn't been possible using previous catalysts.

Formic acid -- the same substance produced by ants (formica is the Latin word for ant) -- is a colourless and pungent liquid with potential as a transportation fuel, for storing electrical energy and for enabling the petrochemical industry to cut CO2 emissions.

As emissions of carbon dioxide, the primary greenhouse gas, rise each year, scientists are looking into options for the capture and storage of CO2, for repurposing CO2, and for pursuing a carbon-free economy.

Wang's group is one of the world leaders in research into CO2 electrochemical reduction (CO2RR) using acidic rather than alkaline conditions.

"This innovation opens up exciting possibilities for carbon-neutral technologies," he says.

"In the future, cars and gas stations could be using repurposed carbon dioxide."

In tests, the new method efficiently converted CO2. for more than 5,000 hours, and the researchers' calculations suggest it can be cost-effectively scaled up for industry.

The experiments used a proton exchange membrane electrolyser.

Carbon dioxide flowed into an electrochemical cell and was converted into formic acid, just like charging a battery.

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Inexpensive, carbon-neutral biofuels are finally possible

When it comes to making fuel from plants, the first step has always been the hardest -- breaking down the plant matter. A new study finds that introducing a simple, renewable chemical to the pretreatment step can finally make next-generation biofuel production both cost-effective and carbon neutral.

For biofuels to compete with petroleum, biorefinery operations must be designed to better utilize lignin. Lignin is one of the main components of plant cell walls. It provides plants with greater structural integrity and resiliency from microbial attacks. However, these natural properties of lignin also make it difficult to extract and utilize from the plant matter, also known as biomass.

"Lignin utilization is the gateway to making what you want out of biomass in the most economical and environmentally friendly way possible," said UC Riverside Associate Research Professor Charles Cai. "Designing a process that can better utilize both the lignin and sugars found in biomass is one of the most exciting technical challenges in this field."

To overcome the lignin hurdle, Cai invented CELF, which stands for co-solvent enhanced lignocellulosic fractionation. It is an innovative biomass pretreatment technology.

"CELF uses tetrahydrofuran or THF to supplement water and dilute acid during biomass pretreatment. It improves overall efficiency and adds lignin extraction capabilities," Cai said. "Best of all, THF itself can be made from biomass sugars."

A landmark Energy & Environmental Science paper details the degree to which a CELF biorefinery offers economic and environmental benefits over both petroleum-based fuels and earlier biofuel production methods.

The paper is a collaboration between Cai's research team at UCR, the Center for Bioenergy Innovation managed by Oak Ridge National Laboratories, and the National Renewable Energy Laboratory, with funding provided by the U.S. Department of Energy's Office of Science. In it, the researchers consider two main variables: what kind of biomass is most ideal and what to do with the lignin once it's been extracted.

First-generation biofuel operations use food crops like corn, soy, and sugarcane as raw materials, or feedstocks. Because these feedstocks divert land and water away from food production, using themfor biofuels is not ideal.

Second-generation operations use non-edible plant biomass as feedstocks. An example of biomass feedstocks includes wood residues from milling operations, sugarcane bagasse, or corn stover, all of which are abundant low-cost byproducts of forestry and agricultural operations.

According to the Department of Energy, up to a billion tons per year of biomass could be made available for the manufacture of biofuels and bioproducts in the US alone, capable of displacing 30% of our petroleum consumption while also creating new domestic jobs.

Because a CELF biorefinery can more fully utilize plant matter than earlier second-generation methods, the researchers found that a heavier, denser feedstock like hardwood poplar is preferable over less carbon-dense corn stover for yielding greater economic and environmental benefits.

Using poplar in a CELF biorefinery, the researchers demonstrate that sustainable aviation fuel could be made at a break-even price as low as $3.15 per gallon of gasoline equivalent. The current average cost for a gallon of jet fuel in the U.S. is $5.96.

The U.S. government issues credits for biofuel production in the form of renewable identification number credits, a subsidy meant to bolster domestic biofuel production. The tier of these credits issued for second-generation biofuels, the D3 tier, is typically traded at $1 per gallon or higher. At this price per credit, the paper demonstrates that one can expect a rate of return of over 20% from the operation.

"Spending a little more for a more carbon-rich feedstock like poplar still yields more economic benefits than a cheaper feedstock like corn stover, because you can make more fuel and chemicals from it," Cai said.

The paper also illustrates how lignin utilization can positively contribute to overall biorefinery economics while keeping the carbon footprint as low as possible. In older biorefinery models, where biomass is cooked in water and acid, the lignin is mostly unusable for more than its heating value.

"The older models would elect to burn the lignin to supplement heat and energy for these biorefineries because they could mostly only leverage the sugars in the biomass -- a costly proposition that leaves a lot of value off the table," said Cai.

In addition to better lignin utilization, the CELF biorefinery model also proposes to produce renewable chemicals. These chemicals could be used as building blocks for bioplastics and food and drink flavoring compounds. These chemicals take up some of the carbon in the plant biomass that would not get released back into the atmosphere as CO2.

"Adding THF helps reduce the energy cost of pretreatment and helps isolate lignin, so you wouldn't have to burn it anymore. On top of that, we can make renewable chemicals that help us achieve a near-zero global warming potential," Cai said. "I think this moves the needle from Gen 2 biofuels to Gen 2+."

In light of the team's recent successes, the Department of Energy's Bioenergy Technology Office has awarded the researchers a $2 million grant to build a small-scale CELF pilot plant at UCR. Cai hopes that demonstrating the pilot plant will lead to larger-scale investment in the technology, as harnessing energy from fossil fuels adds to global warming and hurts the planet.

Read more at Science Daily

Unlocking the secrets of a 'Hot Saturn' and its spotted star

Led by researchers from Université de Montréal's Trottier Institute for Research on Exoplanets (iREx), a team of astronomers has harnessed the power of the revolutionary James Webb Space Webb Telescope (JWST) to study the "hot Saturn" exoplanet HAT-P-18 b.

Their findings, published last month in the journal Monthly Notices of the Royal Astronomical Society, paint a complete picture of the HAT-P-18 b's atmosphere while exploring the great challenge of distinguishing its atmospheric signals from the activity of its star.

HAT-P-18 b is located over 500 light-years away with a mass similar to Saturn's but a size closer to that the larger planet Jupiter. As a result, the exoplanet has a "puffed-up" atmosphere that is especially ideal for analysis.

Passing over a spotted star

Observations from the JWST were taken while the HAT-P-18 b was passing in front of its Sun-like star. This moment is called a transit and is crucial to detect and further characterise an exoplanet from hundreds of light-years away with surprising precision.

Astronomers don't observe light that is being emitted directly by the distant planet. Rather, they study how the central star's light is being blocked and affected by the planet orbiting it, and so must try to disentangle signals caused by the presence of the planet from those caused by the star's own properties.

Just like our Sun, stars do not have uniform surfaces. They can have dark star spots and bright regions, which can create signals that mimic a planet's atmospheric attributes. A recent study of the exoplanet TRAPPIST-1 b and its star TRAPPIST-1 led by UdeM doctoral student Olivia Lim witnessed an eruption, or flare, on the surface of the star, which affected observations.

In the case of planet HAT-P-18 b, Webb caught the exoplanet right as it was passing over a dark spot on its star, HAT-P-18. This is called a spot-crossing event, and its effect was evident in the data collected for the new study. The iREx team also reported the presence of numerous other star spots on HAT-P-18's surface which were not blocked out by the exoplanet.

To accurately determine the exoplanet's atmospheric composition, the researchers had to simultaneously model the planet's atmosphere as well as its star's peculiarities. In their study, they point out that such consideration will be crucial in treating future exoplanet observations via the Webb to fully harness their potential.

"We found that accounting for stellar contamination implies the existence of spots and clouds instead of haze and recovers a water vapour abundance of almost an order of magnitude lower," said lead author Marylou Fournier-Tondreau.

"So considering the system's host star makes a big difference," added Fournier-Tondreau, who did the work as a master's student at iREx and is now pursuing a Ph.D. at the University of Oxford.

"It's actually the first time that we clearly disentangle the signature of hazes versus starspots, thanks to Canada's NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument, which provides wider wavelength coverage extending into the visible light domain."

H2O, CO2, and clouds in a scorching atmosphere

After modelling the exoplanet and the star in the HAT-P-18 system, the iREx astronomers performed a meticulous dissection of HAT-P-18 b's atmospheric composition. By inspecting the light that filters through the exoplanet's atmosphere as it transits its host star, the researchers discerned the presence of water vapour (H2O) and carbon dioxide (CO2).

The researchers also detected the possible presence of sodium and observed strong signs of a cloud deck in HAT-P-18 b's atmosphere, which appears to be muting the signals of many of the molecules found within it. They also concluded that the star's surface was covered by many dark spots that can significantly influence the interpretation of the data.

An earlier analysis of the same JWST data led by a team at Johns Hopkins University had also revealed a clear detection of water and CO2, but also reported the detection of small particles at high-altitudes called hazes and found hints of methane (CH4). The iREx astronomers paint a different picture.

The CH4 detection was not confirmed, and the water abundance they determined was 10 times lower than previously found. They also found that the previous study's detection of hazes could instead be caused by star spots on the star's surface, highlighting the importance of considering the star in the analysis.

Could the exoplanet support life? Not likely. While molecules like water, carbon dioxide, and methane can be interpreted as biosignatures, or signs of life, in certain ratios or in combination with other molecules, HAT-P-18 b's scorching temperatures of close to 600 degrees Celsius do not bode well for the planet's habitability.

Read more at Science Daily

Building on CO2

The construction industry as a CO2 sink? Researchers at Empa's Concrete & Asphalt lab are working on this. By incorporating biochar into concrete, they are exploring the potential of CO2-neutral or even CO2-negative concrete. For optimal applicability, they process the biochar into pellets and use them to replace conventional aggregates.

To achieve the goal of a climate-neutral Switzerland by 2050, strategies and processes with a negative CO2 balance are necessary.

These so-called negative emission technologies (NET) are intended to counterbalane the remaining "hard-to-avoid" emissions in 2050 and should help ensure that we eventually achieve net zero.

As one of the main emitters, the construction sector has a particular obligation.

Around eight percent of global greenhouse gas emissions are caused by cement production.

At the same time, initial efforts are emerging to use the construction sector, with its massive consumption of resources, as a possible carbon sink.

What sounds paradoxical will succeed if we start "building with CO2" -- or rather, using carbon to produce building materials and thus removing it from the atmosphere in the long term.

For such visions to become reality, a great deal of research is needed -- such as is currently being done at Empa's Concrete & Asphalt lab.

A team led by Pietro Lura is developing a process for integrating biochar into concrete.

Difficulties due to porosity

Biochar is produced by a pyrolytic carbonization process of biomass in the absence of oxygen and consists to a high extent of pure carbon -- the carbon that the plants have extracted from the atmosphere in the form of CO2 as they grow.

While CO2 is emitted when plants are burned, it remains bound in the biochar over the long term.

The first concrete products with integrated biochar are already on the market.

However, biochar is often introduced into the concrete untreated, which can lead to difficulties.

"Biochar is very porous and therefore not only absorbs a lot of water, but also expensive admixtures used in concrete production," explains Empa researcher Mateusz Wyrzykowski.

"Moreover, it is difficult to handle and not completely harmless either." The fine coal dust is problematic for the respiratory tract and carries a certain risk of explosion.

For these reasons, the researchers propose in a paper that has just published in the Journal of Cleaner Production processing the biochar into pellets.

"Such lightweight aggregates already exist from other materials such as expanded clay or fly ash. The knowhow in handling these materials is available in industry, and this increases the chances that the concept will be put into practice," says Wyrzykowski.

Net zero at 20 percent share

To produce the pellets, the team used a concrete mixer with a rotating pan in which they mixed the biochar with water and cement and, as a result of the rotation, obtained small pellets with a diameter of between 4 and 32 millimeters.

In turn, they used these pellets to produce normal concrete of strength classes C20/25 to C30/37 -- the classes that are most widely used in civil engineering today.

"With a proportion of 20 percent by volume of carbon pellets in the concrete, we achieve net zero emissions," says Mateusz Wyrzykowski.

That is, the amount of carbon stored offsets all the emissions produced in the production of both the pellets and the concrete.

While the limit has probably not yet been reached for normal concrete (density between 2,000 and 2,600 kg/m3) with 20 percent by volume, the negative emission potential is particularly striking for lightweight concrete (density approx.

1,800 kg/m3): An admixture of 45 percent by volume of carbon pellets in the concrete leads to total negative emissions of minus 290 kg CO2/m3. By comparison, conventional concrete emits around 200 kg CO2/m3.

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First step towards synthetic CO2 fixation in living cells

Synthetic biology offers the opportunity to build biochemical pathways for the capture and conversion of carbon dioxide (CO2). Researchers at the Max-Planck-Institute for Terrestrial Microbiology have developed a synthetic biochemical cycle that directly converts CO2 into the central building block Acetyl-CoA. The researchers were able to implement each of the three cycle modules in the bacterium E.coli, which represents a major step towards realizing synthetic CO2 fixing pathways within the context of living cells.

Developing new ways for the capture and conversion of CO2 is key to tackle the climate emergency.

Synthetic biology opens avenues for designing new-to-nature CO2-fixation pathways that capture CO2 more efficiently than those developed by nature.

However, realizing those new-to-nature pathways in different in vitro and in vivo systems is still a fundamental challenge.

Now, researchers in Tobias Erb's group have designed and constructed a new synthetic CO2-fixation pathway, the so-called THETA cycle.

It contains several central metabolites as intermediates, and with the central building block, acetyl-CoA, as its output.

This characteristic makes it possible to be divided into modules and integrated into the central metabolism of E. coli.

The entire THETA cycle involves 17 biocatalysts, and was designed around the two fastest CO2-fixing enzymes known to date: crotonyl-CoA carboxylase/reductase and phosphoenolpyruvate carboxylase.

The researchers found these powerful biocatalysts in bacteria.

Although each of the carboxylases can capture CO2 more than 10 times faster than RubisCO, the CO2-fixing enzyme in chloroplasts, evolution itself has not brought these capable enzymes together in natural photosynthesis.

The THETA cycle converts two CO2 molecules into one acetyl-CoA in one cycle.

Acetyl-CoA is a central metabolite in almost all cellular metabolism and serves as the building block for a wide array of vital biomolecules, including biofuels, biomaterials, and pharmaceuticals, making it a compound of great interest in biotechnological applications.

Upon constructing the cycle in test tubes, the researchers could confirm its functionality.

Then the training began: through rational and machine learning-guided optimization over several rounds of experiments, the team was able to improve the acetyl-CoA yield by a factor of 100.

In order to test its in vivo feasibility, incorporation into the living cell should be carried out step by step.

To this end, the researchers divided the THETA cycle into three modules, each of which was successfully implemented into the bacterium E. coli. The functionality of these modules was verified through growth-coupled selection and/or isotopic labelling.

"What is special about this cycle is that it contains several intermediates that serve as central metabolites in the bacterium's metabolism. This overlap offers the opportunity to develop a modular approach for its implementation." explains Shanshan Luo, lead author of the study.

"We were able to demonstrate the functionality of the three individual modules in E. coli. However, we have not yet succeeded in closing the entire cycle so that E. coli can grow completely with CO2," she adds.

Closing the THETA cycle is still a major challenge, as all of the 17 reactions need to be synchronized with the natural metabolism of E. coli, which naturally involves hundreds to thousands of reactions.

However, demonstrating the whole cycle in vivo is not the only goal, the researcher emphasizes.

"Our cycle has the potential to become a versatile platform for producing valuable compounds directly from CO2 through extending its output molecule, acetyl-CoA." says Shanshan Luo.

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Geoscientists map changes in atmospheric CO2 over past 66 million years

Today atmospheric carbon dioxide is at its highest level in at least several million years thanks to widespread combustion of fossil fuels by humans over the past couple centuries.

But where does 419 parts per million (ppm) -- the current concentration of the greenhouse gas in the atmosphere -- fit in Earth's history?

That's a question an international community of scientists, featuring key contributions by University of Utah geologists, is sorting out by examining a plethora of markers in the geologic record that offer clues about the contents of ancient atmospheres. Their initial study was published this week in the journal Science, reconstructing CO2 concentrations going back through the Cenozoic, the era that began with the demise dinosaurs and rise of mammals 66 million years ago.

Glaciers contain air bubbles, providing scientists direct evidence of CO2 levels going back 800,000 years, according to U geology professor Gabe Bowen, one of the study's corresponding authors. But this record does not extend very deep into the geological past.

"Once you lose the ice cores, you lose direct evidence. You no longer have samples of atmospheric gas that you can analyze," Bowen said. "So you have to rely on indirect evidence, what we call proxies. And those proxies are tough to work with because they are indirect."

"Proxies" in the geologic record

These proxies include isotopes in minerals, the morphology of fossilized leaves and other lines of geological evidence that reflect atmospheric chemistry. One of the proxies stems from the foundational discoveries of U geologist Thure Cerling, himself a co-author on the new study, whose past research determined carbon isotopes in ancient soils are indicative of past CO2 levels.

But the strength of these proxies vary and most cover narrow slices of the past. The research team, called the Cenozoic CO2 Proxy Integration Project, or CenCO2PIP, and organized by Columbia University climate scientist Bärbel Hönisch, set out to evaluate, categorize and integrate available proxies to create a high-fidelity record of atmospheric CO2.

"This represents some of the most inclusive and statistically refined approaches to interpreting CO2 over the last 66 million years," said co-author Dustin Harper, a U postdoctoral researcher in Bowen's lab. "Some of the new takeaways are we're able to combine multiple proxies from different archives of sediment, whether that's in the ocean or on land, and that really hasn't been done at this scale."

The new research is a community effort involving some 90 scientists from 16 countries. Funded by dozens of grants from multiple agencies, the group hopes to eventually reconstruct the CO2 record back 540 million years to the dawn of complex life.

At the start of the Industrial Revolution -- when humans began burning to coal, then oil and gas to fuel their economies -- atmospheric CO2 was around 280 ppm. The heat-trapping gas is released into the air when these fossil fuels burn.

Looking forward, concentrations are expected to climb up to 600 to 1,000 ppm by the year 2100, depending on the rate of future emissions. It is not clear exactly how these future levels will influence the climate.

But having a reliable map of past CO2 levels could help scientists more accurately predict what future climates may look like, according to U biology professor William Anderegg, director the U's Wilkes Center for Climate & Policy.

"This is an incredibly important synthesis and has implications for future climate change as well, particularly the key processes and components of the Earth system that we need to understand to project the speed and magnitude of climate change," Anderegg said.

Today's 419 ppm is the highest CO2 in 14 million years

At times in the past when Earth was a far warmer place, levels of CO2 were much higher than now. Still, the 419 ppm recorded today represents a steep and perhaps dangerous spike and is unprecedented in recent geologic history.

"By 8 million years before present, there's maybe a 5% chance that CO2 levels were higher than today," Bowen said, "but really we have to go back 14 million years before we see levels we think were like today."

In other words, human activity has significantly altered the atmosphere within the span of a few generations. As a result, climate systems around the globe are showing alarming signs of disruption, such as powerful storms, prolonged drought, deadly heat waves and ocean acidification.

A solid understanding of atmospheric CO2 variation through geological time is also essential to deciphering and learning from various features of Earth's history. Changes in atmospheric CO2 and climate likely contributed to mass extinctions, as well as evolutionary innovations.

Read more at Science Daily

Fossil CO2 emissions at record high in 2023

Global carbon emissions from fossil fuels have risen again in 2023 -- reaching record levels, according to new research from the Global Carbon Project science team.

The annual Global Carbon Budget projects fossil carbon dioxide (CO2 emissions of 36.8 billion tonnes in 2023, up 1.1% from 2022.

Fossil CO2 emissions are falling in some regions, including Europe and the USA, but rising overall -- and the scientists say global action to cut fossil fuels is not happening fast enough to prevent dangerous climate change.

Emissions from land-use change (such as deforestation) are projected to decrease slightly but are still too high to be offset by current levels of reforestation and afforestation (new forests).

The report projects that total global CO2 emissions (fossil + land-use change) will be 40.9 billion tonnes in 2023.

This is about the same as 2022 levels, and part of a 10-year "plateau" -- far from the steep reduction in emissions that is urgently needed to meet global climate targets.

The research team included the University of Exeter, the University of East Anglia (UEA), CICERO Center for International Climate Research, Ludwig-Maximilian-University Munich and 90 other institutions around the world.

"The impacts of climate change are evident all around us, but action to reduce carbon emissions from fossil fuels remains painfully slow," said Professor Pierre Friedlingstein, of Exeter's Global Systems Institute, who led the study.

"It now looks inevitable we will overshoot the 1.5°C target of the Paris Agreement, and leaders meeting at COP28 will have to agree rapid cuts in fossil fuel emissions even to keep the 2°C target alive."

Professor Corinne Le Quéré, Royal Society Research Professor at UEA's School of Environmental Sciences said: "The latest CO2 data shows that current efforts are not profound or widespread enough to put global emissions on a downward trajectory towards Net Zero, but some trends in emissions are beginning to budge, showing climate policies can be effective.

"Global emissions at today's level are rapidly increasing the CO2 concentration in our atmosphere, causing additional climate change and increasingly serious and growing impacts."

"All countries need to decarbonise their economies faster than they are at present to avoid the worse impacts of climate change."

How long until we cross 1.5°C of global warming?

This study also estimates the remaining carbon budget before the 1.5°C target is breached consistently over multiple years, not just for a single year.

At the current emissions level, the Global Carbon Budget team estimates a 50% chance global warming will exceed 1.5°C consistently in about seven years.

This estimate is subject to large uncertainties, primarily due to the uncertainty on the additional warming coming from non-CO2 agents, especially for the 1.5°C targets which is getting close to the current warming level.

However, it's clear that the remaining carbon budget -- and therefore the time left to meet the 1.5°C target and avoid the worse impacts of climate change -- is running out fast.

Other key findings from the 2023 Global Carbon Budget include:

• Regional trends vary dramatically. Emissions in 2023 are projected to increase in India (8.2%) and China (4.0%), and decline in the EU (-7.4%), the USA (-3.0%) and the rest of the world (-0.4%).
• Global emissions from coal (1.1%), oil (1.5%) and gas (0.5%) are all projected to increase.
• Atmospheric CO2 levels are projected to average 419.3 parts per million in 2023, 51% above pre-industrial levels.
• About half of all CO2 emitted continues to be absorbed by land and ocean "sinks," with the rest remaining in the atmosphere where it causes climate change.
• Global CO2 emissions from fires in 2023 have been larger than the average (based on satellite records since 2003) due to an extreme wildfire season in Canada, where emissions were six to eight times higher than average.
• Current levels of technology-based Carbon Dioxide Removal (ie excluding nature-based means such as reforestation) amount to about 0.01 million tonnes CO2, more than a million times smaller than current fossil CO2 emissions.

The Global Carbon Budget report, produced by an international team of more than 120 scientists, provides an annual, peer-reviewed update, building on established methodologies in a fully transparent manner.

Read more at Science Daily

Commitments needed to solve aviation's impact on our climate

Concerted efforts and commitments are needed to solve the complex trade-offs involved in reducing the impact of aviation on the climate, according to new research.

Non-CO2 emissions from aircraft -- largely of nitrogen oxides, soot and water vapour -- are known to add to global warming effects alongside the aviation sector's other CO2 emissions.

Soot triggers the formation of contrails and 'contrail cirrus', which are line-shaped clouds produced by aircraft engine exhaust.

This causes an increase in high clouds that can warm the Earth's atmosphere.

In a comprehensive assessment of the potential solutions to limit the non-CO2 emissions produced by aircraft, scientists warn there is 'no silver bullet' and a committed and co-ordinated effort from a range of stakeholders is urgently required.

The research, published today (November 28) in the Royal Society for Chemistry's journal Environmental Science: Atmospheres, outlines aviation's non-CO2 effects on the atmosphere, both in terms of climate and air quality, and how these may change in the future, as well as the effects of future technologies and fuels.

The findings are the result of a two-year study by Manchester Metropolitan University, the University of Oxford, the University of Reading and Imperial College London.

David Lee, Professor in Atmospheric Science at Manchester Metropolitan, said: "What we highlight is the inherent uncertainties that remain in some of these very complex effects on climate from non-CO2 emissions.

"More importantly, reducing the impact of emissions on the climate is not straightforward as practically all routes forward with conventional liquid hydrocarbon fuels involve 'trade-offs', mostly at the expense of emitting more CO2, whether it be technological or operational efforts.

"These trade-offs and uncertainties mean that there are no simple silver bullets or low-hanging fruit to solve the problem. What is often forgotten is, that while the non-CO2 climate impacts of, for example, an individual flight are short lived, a substantial proportion of the emitted CO2 persists for a very long time, literally tens of millennia. This means it is a difficult balancing act if reducing non-CO2 emissions leads to an increase in CO2 emissions."

Professor Keith Shine, Regius Professor of Meteorology and Climate Science at the University of Reading, is an author of the new paper.

He said: "Given the many uncertainties in the size of aviation non-CO2 climate effects, it is premature to adopt any strategy that aims to decrease non-CO2 climate effects but, at the same time, risks increasing CO2 emissions. We must be mindful that aviation affects local air quality as well as climate. Sometimes measures that improve one will be to the detriment of the other."

Aviation is responsible for around 2.5% of the global CO2 emissions caused by human activity.

However, due to the amount non-CO2 emissions it produces, it is responsible for around 3.5% of change in the energy balance of the atmosphere -- known as radiative forcing -- or around 4% of the increase in global mean temperatures.

The sector is difficult to decarbonise because of its strong dependence on fossil kerosene -- jet fuel -- and the long timescales involved in developing new aircraft and replacing older fleets.

Given the aviation sector's strong growth after the COVID-19 pandemic, this contribution to climate change is set to increase, when other sectors are battling to reduce emissions.

In the latest assessment researchers argue for more work to be performed on the complex trade-offs in order to urgently search for solutions.

This difficulty has recently been recognised by the UK government which, through the Natural Environment Research Council (NERC), has announced a £10 million research programme to help inform policy decisions in this area.

Read more at Science Daily

Ancient carbon in rocks releases as much carbon dioxide as the world's volcanoes

A new study led by the University of Oxford has overturned the view that natural rock weathering acts as a CO2 sink, indicating instead that this can also act as a large CO2 source, rivalling that of volcanoes. The results, published today in the journal Nature, have important implications for modelling climate change scenarios.

Rocks contain an enormous store of carbon in the ancient remains of plants and animals that lived millions of years ago. This means that the "geological carbon cycle" acts as a thermostat that helps to regulate the Earth's temperature. For instance, during chemical weathering rocks can suck up CO2 when certain minerals are attacked by the weak acid found in rainwater. This process helps to counteract the continuous CO2 released by volcanoes around the world, and forms part of Earth's natural carbon cycle that has helped keep the surface habitable to life for a billion years or more.

However, for the first time this new study measured an additional natural process of CO2 release from rocks to the atmosphere, finding that it is as significant as the CO2 released from volcanoes around the world. Currently, this process is not included in most models of the natural carbon cycle.

The process occurs when rocks that formed on ancient seafloors (where plants and animals were buried in sediments) are pushed back up to Earth's surface, for example when mountains like the Himalayas or Andes form. This exposes the organic carbon in the rocks to oxygen in the air and water, which can react and release CO2. This means that weathering rocks could be a source of CO2, rather than the commonly assumed sink.

Up to now, measuring the release of this CO2 from weathering organic carbon in rocks has proved difficult. In the new study, the researchers used a tracer element (rhenium) which is released into water when rock organic carbon reacts with oxygen. Sampling river water to measure rhenium levels makes it possible to quantify CO2 release. However, sampling all river water in the world to get a global estimate would be a significant challenge.

To upscale over Earth's surface, the researchers did two things. First, they worked out how much organic carbon is present in rocks near the surface. Second, they worked out where these were being exposed most rapidly, by erosion in steep, mountain locations.

Dr Jesse Zondervan, the researcher who led the study at the Department of Earth Sciences, University of Oxford, said: "The challenge was then how to combine these global maps with the river data, while considering uncertainties. We fed all of our data into a supercomputer at Oxford, simulating the complex interplay of physical, chemical, and hydrological processes. By piecing together this vast planetary jigsaw, we could finally estimate the total carbon dioxide emitted as these rocks weather and exhale their ancient carbon into the air."

This could then be compared to how much CO2 could be drawn down by natural rock weathering of silicate minerals. The results identified many large areas where weathering was a CO2 source, challenging the current view about how weathering impacts the carbon cycle. Hotspots of CO2 release were concentrated in mountain ranges with high uplift rates that cause sedimentary rocks to be exposed, such as the eastern Himalayas, the Rocky Mountains, and the Andes. The global CO2 release from rock organic carbon weathering was found to be 68 megatons of carbon per year.

Professor Robert Hilton (Department of Earth Sciences, University of Oxford), who leads the ROC-CO2 research project that funded the study, said: "This is about 100 times less than present day human CO2 emissions by burning fossil fuels, but it is similar to how much CO2 is released by volcanoes around the world, meaning it is a key player in Earth's natural carbon cycle."

These fluxes could have changed during Earth's past. For instance, during periods of mountain building that bring up many rocks containing organic matter, the CO2 release may have been higher, influencing global climate in the past.

Ongoing and future work is looking into how changes in erosion due to human activities, alongside the increased warming of rocks due to anthropogenic climate changes, could increase this natural carbon leak. A question the team are now asking is if this natural CO2 release will increase over the coming century. "Currently we don't know -- our methods allow us to provide a robust global estimate, but not yet assess how it could change'' says Hilton.

Read more at Science Daily