̽��ֱ�� of Cambridge - carbon dioxide

Researchers unravel the complex reaction pathways in zero-carbon fuel synthesis

Anonymous — Fri, 20 Jan 2023 11:54:46 +0000

When the eCO2EP: A chemical energy storage technology project started in 2018, the objective was to develop ways of converting carbon dioxide emitted as part of industrial processes into useful compounds, a process known as electrochemical CO2 reduction (eCO2R)

While eCO2R is not a new technique, the challenge has always been the inability to control the end products. Now, researchers from the ̽��ֱ�� of Cambridge have outlined how carbon isotopes can be used to trace intermediates during the process, which will allow scientists to create more selective catalysts, control product selectivity, and promote eCO2R as a more promising production method for chemicals and fuels in the low-carbon economy. Their results are reported in the journal Nature Catalysis.

̽��ֱ��project was led by Professor Alexei Lapkin, from Cambridge’s Centre for Advanced Research and Education in Singapore (CARES Ltd) and Professor Joel Ager, from the Berkeley Education Alliance for Research in Singapore (BEARS Ltd). Both organisations are part of the Campus for Research Excellence and Technological Enterprise (CREATE) funded by Singapore’s National Research Foundation.

In the 1950s, Berkeley’s Melvin Calvin identified the elementary steps used in nature to fix carbon dioxide in photosynthesis. Calvin and his colleagues used a radioactive form of carbon as a tracer to learn the order in which intermediates appeared in the cycle now named after him, work which won him the Nobel Prize in Chemistry in 1961.

̽��ֱ��eCO2EP team found that with a sensitive enough mass spectrometer, they could use the small differences in reaction rates associated with the two stable isotopes of carbon, carbon-12 and carbon-13, to perform similar types of analyses.

First, a mixture of products such as methanol and ethylene were generated by a prototype reactor that was built to operate under industrial conditions. To detect both major and minor products in real time as the operating conditions were changed, high-sensitivity mass spectrometry was used.

Since high-sensitivity mass spectrometry is more commonly used in biological and atmospheric sciences, co-authors Dr Mikhail Kovalev and Dr Hangjuan Ren adapted the technique to their prototype system. They developed a method to directly sample the reaction environment with high sensitivity and time response.

̽��ֱ��researchers used the difference in reaction rates of carbon-12 and carbon-13 to group a product such as ethanol and its major intermediates sharing the same pathway, to deduce key relationships in the chemical network.

̽��ֱ��researchers found that there are substantial differences in the mechanisms at work in smaller reactors versus larger reactors, a finding which will enable them to better control product selectivity.

̽��ֱ��team also discovered that the reaction used less of the heavier carbon-13 isotope than carbon-12. This difference in usage was found to be five times greater than that observed in natural photosynthesis, where carbon-13 is fixed at a slower rate than carbon-12. This is inspiring efforts in Professor Ager’s lab to better understand fundamental physics and the chemical origins of this large and unanticipated effect. An international patent application has also been filed.

“ ̽��ֱ��set-up of the project within CREATE Campus allowed Joel and I to create an environment of creativity and ambition, to enable the researchers to excel and to target the really complex and interesting problems,” said Lapkin. “ ̽��ֱ��monitoring of multiple species in such a complex reaction is, by itself, a significant breakthrough by the team, but the ability to further dig into the mechanism by exploring the isotope enrichment effect has made all the difference.”

“This work required an interdisciplinary approach drawing on expertise from both Cambridge and Berkeley,” said Ager. “CREATE campus provided an ideal environment to realise this collaborative research with a skilled and motivated team.”

̽��ֱ��eCO2EP project was funded by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.

Reference:
Hangjuan Ren et al. ‘Operando proton-transfer-reaction time-of-flight mass spectrometry of carbon dioxide reduction electrocatalysis.’ Nature Catalysis (2022). DOI: 10.1038/s41929-022-00891-3.

Adapted from a story posted on the CARES website.

Researchers have used isotopes of carbon to trace how carbon dioxide emissions could be converted into low-carbon fuels and chemicals. ̽��ֱ��result could help the chemical industry, which is the third largest subsector in terms of direct CO2 emissions, recycle its own waste using current manufacturing processes.

yorkfoto via Getty Images

Chemical plant drone view

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Big data's hidden cost

cjb250 — Mon, 16 Jan 2023 11:42:56 +0000

As the climate emergency and cost-of-living crisis focus our minds on how to reduce energy, a group of scientists have highlighted the hidden environmental cost behind some of our major breakthroughs.

New, nature-inspired concepts for turning CO2 into clean fuels

sc604 — Mon, 28 Feb 2022 16:16:16 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, have previously shown that biological catalysts, or enzymes, can produce fuels cleanly using renewable energy sources, but at low efficiency.

Their latest research has improved fuel production efficiency by 18 times in a laboratory setting, demonstrating that polluting carbon emissions can be turned into green fuels efficiently without any wasted energy. ̽��ֱ��results are reported in two related papers in Nature Chemistry and Proceedings of the National Academy of Sciences.

Most methods for converting CO2 into fuel also produce unwanted by-products such as hydrogen. Scientists can alter the chemical conditions to minimise hydrogen production, but this also reduces the performance for CO2 conversion: so cleaner fuel can be produced, but at the cost of efficiency.

̽��ֱ��Cambridge-developed proof of concept relies on enzymes isolated from bacteria to power the chemical reactions which convert CO2 into fuel, a process called electrolysis. Enzymes are more efficient than other catalysts, such as gold, but they are highly sensitive to their local chemical environment. If the local environment isn’t exactly right, the enzymes fall apart and the chemical reactions are slow.

̽��ֱ��Cambridge researchers, working with a team from the Universidade Nova de Lisboa in Portugal, have developed a method to improve the efficiency of electrolysis by fine-tuning the solution conditions to alter the local environment of the enzymes.

“Enzymes have evolved over millions of years to be extremely efficient and selective, and they’re great for fuel-production because there aren’t any unwanted by-products,” said Dr Esther Edwardes Moore from Cambridge’s Yusuf Hamied Department of Chemistry, first author of the PNAS paper. “However, enzyme sensitivity throws up a different set of challenges. Our method accounts for this sensitivity, so that the local environment is adjusted to match the enzyme’s ideal working conditions.”

̽��ֱ��researchers used computational methods to design a system to improve the electrolysis of CO2. Using the enzyme-based system, the level of fuel production increased by 18 times compared to the current benchmark solution.

To improve the local environment further, the team showed how two enzymes can work together, one producing fuel and the other controlling the environment. They found that by adding another enzyme, it sped up the reactions, both increasing efficiency and reducing unwanted by-products.

“We ended up with just the fuel we wanted, with no side-products and only marginal energy losses, producing clean fuels at maximum efficiency,” said Dr Sam Cobb, first author of the Nature Chemistry paper. “By taking our inspiration from biology, it will help us develop better synthetic catalyst systems, which is what we’ll need if we’re going to deploy CO2 electrolysis at a large scale.”

“Electrolysis has a big part to play in reducing carbon emissions,” said Professor Erwin Reisner, who led the research. “Instead of capturing and storing CO2, which is incredibly energy-intensive, we have demonstrated a new concept to capture carbon and make something useful from it in an energy-efficient way.”

̽��ֱ��researchers say that the secret to more efficient CO2 electrolysis lies in the catalysts. There have been big improvements in the development of synthetic catalysts in recent years, but they still fall short of the enzymes used in this work.

“Once you manage to make better catalysts, many of the problems with CO2 electrolysis just disappear,” said Cobb. “We’re showing the scientific community that once we can produce catalysts of the future, we’ll be able to do away with many of the compromises currently being made, since what we learn from enzymes can be transferred to synthetic catalysts.”

“Once we designed the concept, the improvement in performance was startling,” said Edwardes Moore. “I was worried we’d spend years trying to understand what was going on at the molecular level, but once we truly appreciated the influence of the local environment, it evolved really quickly.”

“In future we want to use what we have learned to tackle some challenging problems that the current state-of-the-art catalysts struggle with, such as using CO2 straight from air as these are conditions where the properties of enzymes as ideal catalysts can really shine,” said Cobb.

Erwin Reisner is a Fellow of St John’s College, Cambridge. Sam Cobb is a Research Fellow of Darwin College, Cambridge. Esther Edwardes Moore completed her PhD with Corpus Christi College, Cambridge. ̽��ֱ��research was supported in part by the European Research Council, the Leverhulme Trust, and the Engineering and Physical Sciences Research Council.

Reference:
Samuel J Cobb et al. ‘Fast CO2 hydration kinetics impair heterogeneous but improve enzymatic CO2 reduction catalysis.’ Nature Chemistry (2022). DOI: 10.1038/s41557-021-00880-2

Esther Edwardes Moore et al. ‘Understanding the Local Chemical Environment of Bioelectrocatalysis.’ Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2114097119

Researchers have developed an efficient concept to turn carbon dioxide into clean, sustainable fuels, without any unwanted by-products or waste.

Instead of capturing and storing CO2, which is incredibly energy-intensive, we have demonstrated a new concept to capture carbon and make something useful from it in an energy-efficient way

Erwin Reisner

Esther Edwardes Moore

Computer-generated image of enzyme

Yes

Wireless device makes clean fuel from sunlight, CO2 and water

sc604 — Mon, 24 Aug 2020 15:00:00 +0000

̽��ֱ��device, developed by a team from the ̽��ֱ�� of Cambridge, is a significant step toward achieving artificial photosynthesis – a process mimicking the ability of plants to convert sunlight into energy. It is based on an advanced ‘photosheet’ technology and converts sunlight, carbon dioxide and water into oxygen and formic acid – a storable fuel that can be either be used directly or be converted into hydrogen.

̽��ֱ��results, reported in the journal Nature Energy, represent a new method for the conversion of carbon dioxide into clean fuels. ̽��ֱ��wireless device could be scaled up and used on energy ‘farms’ similar to solar farms, producing clean fuel using sunlight and water.

Harvesting solar energy to convert carbon dioxide into fuel is a promising way to reduce carbon emissions and transition away from fossil fuels. However, it is challenging to produce these clean fuels without unwanted by-products.

“It’s been difficult to achieve artificial photosynthesis with a high degree of selectivity, so that you’re converting as much of the sunlight as possible into the fuel you want, rather than be left with a lot of waste,” said first author Dr Qian Wang from Cambridge’s Department of Chemistry.

“In addition, storage of gaseous fuels and separation of by-products can be complicated – we want to get to the point where we can cleanly produce a liquid fuel that can also be easily stored and transported,” said Professor Erwin Reisner, the paper’s senior author.

In 2019, researchers from Reisner’s group developed a solar reactor based on an ‘artificial leaf’ design, which also uses sunlight, carbon dioxide and water to produce a fuel, known as syngas. ̽��ֱ��new technology looks and behaves quite similarly to the artificial leaf but works in a different way and produces formic acid.

While the artificial leaf used components from solar cells, the new device doesn’t require these components and relies solely on photocatalysts embedded on a sheet to produce a so-called photocatalyst sheet. ̽��ֱ��sheets are made up of semiconductor powders, which can be prepared in large quantities easily and cost-effectively.

In addition, this new technology is more robust and produces clean fuel that is easier to store and shows potential for producing fuel products at scale. ̽��ֱ��test unit is 20 square centimetres in size, but the researchers say that it should be relatively straightforward to scale it up to several square metres. In addition, the formic acid can be accumulated in solution, and be chemically converted into different types of fuel.

“We were surprised how well it worked in terms of its selectivity – it produced almost no by-products,” said Wang. “Sometimes things don’t work as well as you expected, but this was a rare case where it actually worked better.”

̽��ֱ��carbon-dioxide converting cobalt-based catalyst is easy to make and relatively stable. While this technology will be easier to scale up than the artificial leaf, the efficiencies still need to be improved before any commercial deployment can be considered. ̽��ֱ��researchers are experimenting with a range of different catalysts to improve both stability and efficiency.

̽��ֱ��current results were obtained in collaboration with the team of Professor Kazunari Domen from the ̽��ֱ�� of Tokyo, a co-author of the study.

̽��ֱ��researchers are now working to further optimise the system and improve efficiency. Additionally, they are exploring other catalysts for using on the device to get different solar fuels.

“We hope this technology will pave the way toward sustainable and practical solar fuel production,” said Reisner.

Reference:
Qian Wang et al. ‘Molecularly engineered photocatalyst sheet for scalable solar formate production from carbon dioxide and water.’ Nature Energy (2020). DOI: 10.1038/s41560-020-0678-6

A bold response to the world’s greatest challenge
̽��ֱ�� ̽��ֱ�� of Cambridge is building on its existing research and launching an ambitious new environment and climate change initiative. Cambridge Zero is not just about developing greener technologies. It will harness the full power of the ̽��ֱ��’s research and policy expertise, developing solutions that work for our lives, our society and our biosphere.

Researchers have developed a standalone device that converts sunlight, carbon dioxide and water into a carbon-neutral fuel, without requiring any additional components or electricity.

We hope this technology will pave the way toward sustainable and practical solar fuel production

Erwin Reisner

Dr Qian Wang

Yes

Carbon dioxide ‘pulses’ are a common feature of the carbon cycle

cmm201 — Thu, 20 Aug 2020 18:00:00 +0000

Ice cores from Antarctica show that, in the span of less than two centuries, atmospheric levels of carbon dioxide jumped repeatedly at the end of the last ice age, when the Atlantic was continuously disturbed by melting ice sheets.

Whether these CO₂ jumps might occur in today’s conditions, when we are already seeing the impact of human-driven CO₂ emissions and rapidly melting polar ice sheets, has remained unknown.

̽��ֱ��study, published in the journal Science and by researchers from the Universities of Cambridge, Bern and Grenoble Alpes, reveals that rapid CO₂ jumps also occurred during a period from 450,000 to 330,000 years ago, a key time in Earth’s history covering more than a full glacial cycle.

“By looking back further in time, to previous glacial and interglacial conditions, we find the same CO₂jumps - irrespective of whether the climate was cold or warm,” said first author Dr Christoph Nehrbass-Ahles from Cambridge’s Department of Earth Sciences, who conducted the research while based at the ̽��ֱ�� of Bern.

These rapid CO₂ rises seem to be a common feature of the carbon cycle in the past. But, said Nehrbass-Ahles, human activities are releasing carbon a rate ten times faster than during CO₂ increases in the past. “What is unclear is how a future jump in carbon may interact with or exacerbate anthropogenic carbon emissions,” he said.

Central to the team’s finding was their detailed analysis of Antarctic ice from the EPICA ( ̽��ֱ��European Project for Ice Coring in Antarctica) Dome C ice core.

“Our previous understanding of rapid CO₂ changes has been hampered by a lack of detailed data over this interval – so these events were often missed,” said Nehrbass-Ahles. Thanks to a new gas extraction method and detailed sampling campaign, the team was able to identify subtle changes occurring at centennial timescales.

̽��ֱ��study marks an important step in understanding what causes such abrupt increases and possible feedbacks in the Earth’s climate system. “Scientists are uncertain as to the mechanism behind the CO₂ jumps, but think a combination of factors, including ocean circulation, changing wind patterns, and terrestrial processes, are likely responsible,” said co-author Professor David Hodell, also from the Department of Earth Sciences.

̽��ֱ��researchers combined the new ice core data with detailed information on ocean circulation from marine sediments collected off the coast of Portugal. ̽��ֱ��site, which was drilled as part of the International Ocean Discovery Program (IODP), is unique for its high accumulation of sediments and is ideally situated for monitoring the changes in ocean circulation triggered when ice sheets collapsed.

̽��ֱ��isotopic signal of the marine sediments showed the same pattern as the ice cores. “ ̽��ֱ��abrupt changes are clearly represented in both the marine and ice records, telling us that they must be connected to major changes in the surface and deep circulation of the Atlantic Ocean,” said Hodell.

According to Nehrbass-Ahles, the key is the high resolution of the ice and marine sediments records, making observations of these rapid changes in both records possible. “Understanding these centennial-scale changes is crucial because they operate at a similar pace to the anthropogenic changes altering our planet,” he said.

Reference:
C. Nehrbass-Ahles et al. ‘Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions.’ Science (2020). DOI: 10.1126/science.aay8178

Researchers have found that pulse-like releases of carbon dioxide to the atmosphere are a pervasive feature of the carbon cycle and that they are closely connected to major changes in Atlantic Ocean circulation.

Understanding these centennial-scale changes is crucial because they operate at a similar pace to the anthropogenic changes altering our planet

Christoph Nehrbass-Ahles

Thibaut Vergoz, Institut polaire français

Concordia research station in Antarctica

Yes

High flying academics

cjb250 — Mon, 10 Feb 2020 08:53:30 +0000

Cambridge ̽��ֱ�� has committed to dramatically reducing its carbon footprint. But making a meaningful difference will involve tackling the culture of international travel that runs deeply through academia.

Carbon capture: universities and industry work together to tackle emissions

sc604 — Wed, 25 Oct 2017 07:12:18 +0000

̽��ֱ��world is not going carbon-free any time soon: that much is clear. Developed and developing countries alike rely on fossil fuels for transport, industry and power, all of which release CO₂ into the atmosphere. But as sea levels rise, ‘unprecedented’ weather events become commonplace and the polar ice caps melt, how can we balance our use of fossil fuels with the imperative to combat the catastrophic effects of climate change?

“Everything suggests that we won’t be able to stop burning carbon-based fuels, particularly in rapidly developing countries like India and China,” says Professor Mike Bickle of Cambridge’s Department of Earth Sciences. “Along with increasing use of renewable energy and improved energy efficiency, one way to cope with that is to use carbon capture and storage – and there is no technical reason why it can’t be deployed right now.”

Carbon capture and storage (CCS) is a promising and practical solution to drastically reducing carbon emissions, but it has had a stilted development pathway to date. In 2015, the UK government cancelled a £1 billion competition for CCS technology six months before it was due to be awarded, citing high costs. Just one year later, a high-level advisory group appointed by ministers recommended that establishing a CCS industry in the UK now could save the government and consumers billions per year from the cost of meeting climate change targets.

CCS is the only way of mitigating the 20% of CO₂ emissions from industrial processes – such as cement manufacturing and steel making, for which there is no obvious alternative – to help meet the world’s commitments to limit warming to below 2^oC. It works by trapping the CO₂ emitted from burning fossil fuels, which is then cooled, liquefied and pumped deep underground into geological formations, saline aquifers or disused oil and gas fields. Results from lab-based tests, and from working CCS sites such as Sleipner in the North Sea, suggest that carbon can be safely stored underground in this way for 10,000 years or more.

“ ̽��ֱ��big companies understand the science of climate change, and they understand that we’ve got to invest in technologies like CCS now, before it’s too late,” says Dr Jerome Neufeld of Cambridge’s Department of Applied Mathematics and Theoretical Physics, and Department of Earth Sciences. “But it’s a tricky business running an industry where nobody is charging for carbon.”

“Everyone always wants the cheapest option, so without some form of carbon tax, it’s going to be difficult to get CCS off the ground at the scale that’s needed,” says Bickle. “But if you look at the cost of electricity produced from gas or coal with CCS added, it’s very similar to the cost of electricity from solar or wind. So if governments put a proper carbon charge in place, renewables and CCS would compete with each other on a relatively even playing field, and companies would have the economic incentive to invest in CCS.”

Bickle and Neufeld are following discussions about CCS closely because, along with collaborators from Stanford and Melbourne Universities, they have recently started a new CCS project with the support of BHP, one of the world’s largest mining and materials companies.

̽��ֱ��three-year project will develop and improve methods for the long-term storage of CO₂, and will test them at Otway in southern Australia, one of the largest CCS test sites in the world. Using a mix of theoretical modelling and small-, medium- and large-scale experiments, the researchers hope to significantly increase the types of sites where CCS is possible, including in China and developing economies.

In most current CCS schemes, CO₂ is stored in porous underground rock formations with a thick layer of non-porous rock, such as shale, on top. ̽��ֱ��top layer provides extra insurance that the relatively light CO₂ will not escape.

̽��ֱ��new research, which will support future large-scale CO₂ storage, will consider whether CO₂ could be effectively trapped without the top seal of impermeable rock, meaning that CCS could be deployed in a wider range of environments. Their research findings will be made publicly available to accelerate the broader deployment of CCS.

“We are seeing a growing acknowledgement from industry, governments and society that to meet emissions reductions targets we are going to need to accelerate the use of this technology – we simply can’t do it quickly enough without CCS across both power generation and industry,” says BHP Vice President of Sustainability and Climate Change, Dr Fiona Wild. “We know CCS technology works and is proven. Our focus at BHP is on how we can help make sure the world has access to the information required to make it work at scale in a cost effective and timely way.”

During the project, Stanford researchers will measure the rate at which porous rock can trap CO₂ using small-scale experiments on rock samples at reservoir conditions, while the Cambridge researchers will be using larger analogue models, in the order of metres or tens of metres. ̽��ֱ��Melbourne-based researchers will use large-scale numerical simulations of complex geological settings.

“One of the things this collaboration will really open up is the ability to deploy CCS almost anywhere,” says Neufeld, who is also affiliated with Cambridge’s Department of Earth Sciences and the BP Institute. “We know that CO₂ can be safely trapped in porous rock with a seal of shale on top, but the early results from Otway have shown that even without the impenetrable seal, CO₂ can be trapped just as effectively.”

When CO₂ is pumped into underground saline aquifers, it is in a ‘super-critical’ phase: not quite a liquid and not quite a gas. ̽��ֱ��super-critical CO₂ is less dense than the salt water, and so has a tendency to run uphill, but it’s been found that surface tension between the salt water and the rock is quite effective at pinning the CO₂ in place so that it can’t escape. This phenomenon, known as capillary trapping, is also observed when water is held in a sponge.

“ ̽��ֱ��results from Otway show that if you inject CO₂ into a heterogeneous reservoir, it will mix with the salt water and capillary trapping will pin it there quite effectively, so it opens up a much broader range of potential carbon storage sites,” says Bickle.

“However, we need to start deploying CCS now, and the biggest challenges we face are economics and policy. If these prevent us from doing anything until it’s too late, and we’re at a stage when we’d have to start capturing carbon directly from the atmosphere, it will be far more expensive. By not starting CCS now, we’re building false economies.”

An international collaboration between universities and industry will further develop carbon capture and storage technology – one of the best hopes for drastically reducing carbon emissions – so that it can be deployed in a wider range of sites around the world.

We need to start deploying CCS now, and the biggest challenges we face are economics and policy. If we’re at a stage when we’d have to start capturing carbon directly from the atmosphere, it will be far more expensive.

Mike Bickle

Jerome Neufeld

Modelling CCS

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Link identified between continental breakup, volcanic carbon emissions and evolution

sc604 — Thu, 20 Jul 2017 18:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used existing measurements of carbon and helium from more than 80 volcanoes around the world in order to determine its origin. Carbon and helium coming out of volcanoes can either come from deep within the Earth or be recycled near the surface, and measuring the chemical fingerprint of these elements can pinpoint their source. When the team analysed the data, they found that most of the carbon coming out of volcanoes is recycled near the surface, in contrast with earlier assumptions that the carbon came from deep in the Earth’s interior. “This is an essential piece of geological carbon cycle puzzle,” said Dr Marie Edmonds, the senior author of the study.

Over millions of years, carbon cycles back and forth between Earth’s deep interior and its surface. Carbon is removed from the surface from processes such as the formation of limestone and the burial and decay of plants and animals, which allows atmospheric oxygen to grow at the surface. Volcanoes are one way that carbon is returned to the surface, although the amount they produce is less than a hundredth of the amount of carbon emissions caused by human activity. Today, the majority of carbon from volcanoes is recycled near the surface, but it is unlikely that this was always the case.

Volcanoes form along large island or continental arcs where tectonic plates collide and one plate slides under the other, such as the Aleutian Islands between Alaska and Russia, the Andes of South America, the volcanoes throughout Italy, and the Mariana Islands in the western Pacific. These volcanoes have different chemical fingerprints: the ‘island arc’ volcanoes emit less carbon which comes from deep in the mantle, while the ‘continental arc’ volcanoes emit far more carbon which comes from closer to the surface.

Over hundreds of millions of years, the Earth has cycled between periods of continents coming together and breaking apart. During periods when continents come together, volcanic activity was dominated by island arc volcanoes; and when continents break apart, continental volcano arcs dominate. This back and forth changes the chemical fingerprint of carbon coming to Earth’s surface systematically over geological time, and can be measured through the different isotopes of carbon and helium.

Variations in the isotope ratio, or chemical fingerprint, of carbon are commonly measured in limestone. Researchers had previously thought that the only thing that could change the carbon fingerprint in limestone was the production of atmospheric oxygen. As such, the carbon isotope fingerprint in limestone was used to interpret the evolution of habitability of Earth’s surface. ̽��ֱ��results of the Cambridge team suggest that volcanoes played a larger role in the carbon cycle than had previously been understood, and that earlier assumptions need to be reconsidered.

“This makes us fundamentally re-evaluate the evolution of the carbon cycle,” said Edmonds. “Our results suggest that the limestone record must be completely reinterpreted if the volcanic carbon coming to the surface can change its carbon isotope composition.”

A great example of this is in the Cretaceous Period, 144 to 65 million years ago. During this time period there was a major increase in the carbon isotope ratio found in limestone, which has been interpreted as an increase in atmospheric oxygen concentration. This increase in atmospheric oxygen was causally linked to the proliferation of mammals in the late Cretaceous. However, the results of the Cambridge team suggest that the increase in the carbon isotope ratio in the limestones could be almost entirely due to changes in the types of volcanoes at the surface.

“ ̽��ֱ��link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated,” said co-author Dr Alexandra Turchyn, also from the Department of Earth Sciences.

̽��ֱ��research was funded by the Alfred P. Sloan Foundation, the Deep Carbon Observatory and the European Research Council.

Reference:
Emily Mason, Marie Edmonds, Alexandra V. Turchyn. ‘Remobilization of crustal carbon may dominate volcanic arc emissions.’ Science (2017). DOI: 10.1126/science.aan5049.

Inset Image: Schematic diagram to show the possible sources of carbon in a subduction zone volcanic system.

Researchers have found that the formation and breakup of supercontinents over hundreds of millions of years controls volcanic carbon emissions. ̽��ֱ��results, reported in the journal Science, could lead to a reinterpretation of how the carbon cycle has evolved over Earth’s history, and how this has impacted the evolution of Earth’s habitability.

̽��ֱ��link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated.

Alexandra Turchyn

Image courtesy of the Earth Science and Remote Sensing Unit, NASA Johnson Space Center

ISS013-E-24184 (23 May 2006) --- Eruption of Cleveland Volcano, Aleutian Islands, Alaska is featured in this image photographed by an Expedition 13 crewmember on the International Space Station.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

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