Uncovering secrets of plant regeneration

Japanese researchers identify how the fate of regenerating plant cells is negatively controlled by the WOX13 gene and how this can impact shoot regeneration efficiency

Peer-Reviewed Publication

NARA INSTITUTE OF SCIENCE AND TECHNOLOGY

 

IMAGE: MUTUALLY REPRESSIVE WOX13 AND WUS PLAY KEY ROLES IN CELL FATE SPECIFICATION OF PLURIPOTENT CALLUS CELLS. SCHEMATIC ILLUSTRATION OF THE REGULATORY MECHANISMS (LEFT) AND SPATIAL EXPRESSION PATTERNS OF WOX13 AND WUS IN CALLUS CELL POPULATION (RIGHT). view more 

CREDIT: MOMOKO IKEUCHI

Ikoma, Japan – Plants have the unique ability to regenerate entirely from a somatic cell, i.e., an ordinary cell that does not typically participate in reproduction. This process involves the de novo (or new) formation of a shoot apical meristem (SAM) that gives rise to lateral organs, which are key for the plant’s reconstruction. At the cellular level, SAM formation is tightly regulated by either positive or negative regulators (genes/protein molecules) that may induce or restrict shoot regeneration, respectively. But which molecules are involved? Are there other regulatory layers that are yet to be uncovered?

To seek answers to the above questions, a research group led by Nara Institute of Science and Technology (NAIST), Japan studied the process in Arabidopsis, a plant commonly used in genetic research. Their research—which was published in Science Advances—identified and characterized a key negative regulator of shoot regeneration. They demonstrated how the WUSCHEL-RELATED HOMEOBOX 13 (WOX13) gene and its protein can promote the non-meristematic (non-dividing) function of callus cells by acting as a transcriptional (RNA-level) repressor, thereby impacting regeneration efficiency.

“The search for strategies to enhance shoot regeneration efficiency in plants has been a long one. But progress has been hindered because the related regulatory mechanisms have been unclear. Our study fills this gap by defining a new cell-fate specification pathway,” explains Momoko Ikeuchi, the principal investigator of this study.

Previous studies from her team had already established the role of WOX13 in tissue repair and organ adhesion after grafting. Hence, they first tested the potential role of this gene in the control of shoot regeneration in a wox13 Arabidopsis mutant (plant with dysfunctional WOX13) using a two-step tissue culture system. Phenotypic and imaging analysis revealed that shoot regeneration was accelerated (3 days faster) in plants lacking WOX13, and slower when WOX13 expression was induced. Moreover, in normal plants, WOX13 showed locally reduced expression levels in SAM. These findings suggest that WOX13 can negatively regulate shoot regeneration.

To validate their findings, the researchers compared the wox13 mutants and wild-type (normal) plants using RNA-sequencing at multiple time points. The absence of WOX13 did not considerably alter Arabidopsis gene expression under callus-inducing conditions. However, shoot-inducing conditions significantly enhanced the alterations induced by the wox13 mutation, leading to an upregulation of shoot meristem regulator genes. Interestingly, these genes were suppressed within 24 hours of WOX13 overexpression in mutant plants. Overall, they found that WOX13 inhibits a subset of shoot meristem regulators while directly activating cell wall modifier genes involved in cell expansion and cellular differentiation. Subsequent Quartz-Seq2-based single cell RNA sequencing (scRNA-seq) confirmed the key role of WOX13 in specifying the fate of pluripotent callus cells.

This study highlights that unlike other known negative regulators of shoot regeneration, which only prevent the shift from callus toward SAM, WOX13 inhibits SAM specification by promoting the acquisition of alternative fates. It achieves this inhibition through a mutually repressive regulatory circuit with the regulator WUS, promoting the non-meristematic cell fate by transcriptionally inhibiting WUS and other SAM regulators and inducing cell wall modifiers. In this way, WOX13 acts as a major regulator of regeneration efficiency. “Our findings show that knocking out WOX13 can promote the acquisition of shoot fate and enhance shoot regulation efficiency. This means that WOX13 knockout can serve as a tool in agriculture and horticulture and boost the tissue culture-mediated de novo shoot regeneration of crops,” concludes Ikeuchi.

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Resource

Title: WUSCHEL-RELATED HOMEOBOX 13 suppresses de novo shoot regeneration via cell fate control of pluripotent callus

Authors: Nao Ogura, Yohei Sasagawa, Tasuku Ito, Toshiaki Tameshige, Satomi Kawai, Masaki Sano, Yuki Doll, Akira Iwase, Ayako Kawamura, Takamasa Suzuki, Itoshi Nikaido, Keiko Sugimoto, Momoko Ikeuchi

Journal: Science Advances

DOI: 10.1126/sciadv.adg6983

Information about the Plant Regeneration and Morphogenesis Laboratory can be found at the following website: https://bsw3.naist.jp/eng/courses/courses117.html

 

About Nara Institute of Science and Technology (NAIST)

Established in 1991, Nara Institute of Science and Technology (NAIST) is a national university located in Kansai Science City, Japan. In 2018, NAIST underwent an organizational transformation to promote and continue interdisciplinary research in the fields of biological sciences, materials science, and information science. Known as one of the most prestigious research institutions in Japan, NAIST lays a strong emphasis on integrated research and collaborative co-creation with diverse stakeholders. NAIST envisions conducting cutting-edge research in frontier areas and training students to become tomorrow's leaders in science and technology.

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JOURNAL

Science Advances

DOI

10.1126/sciadv.adg6983 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

WUSCHEL-RELATED HOMEOBOX 13 suppresses de novo shoot regeneration via cell fate control of pluripotent callus

ARTICLE PUBLICATION DATE

7-Jul-2023

Top corn producing state to see future drop in yield, cover crop efficiency

Peer-Reviewed Publication

UNIVERSITY OF ILLINOIS COLLEGE OF AGRICULTURAL, CONSUMER AND ENVIRONMENTAL SCIENCES

 

IMAGE: IN A NEW STUDY, UNIVERSITY OF ILLINOIS RESEARCHERS FORECASTED THE EFFECTS OF ILLINOIS CLIMATE CHANGE, FINDING A DECLINE IN CORN YIELD, AN INCREASE IN NITRATE LOSSES, AND A DECREASE IN THE EFFICIENCY OF COVER CROPS TO REDUCE THOSE LOSSES. THE RESEARCHERS SAY ADDITIONAL BEST MANAGEMENT PRACTICES WILL BE NEEDED TO REDUCE NITRATE LOSSES IN THE FUTURE. view more 

CREDIT: LAUREN QUINN, UNIVERSITY OF ILLINOIS

URBANA, Ill. — Winter cover crops could cut nitrogen pollution in Illinois’ agricultural drainage water up to 30%, according to recent research from the University of Illinois Urbana-Champaign. But how will future climate change affect nitrogen loss, and will cover crops still be up to the job? A new study investigating near- and far-term climate change in Illinois suggests cover crops will still be beneficial, but not to the same degree. The report also forecasts corn and soybean yield across the state, finding corn will suffer much more than soybean, especially in southern regions. 

In their earlier study, the research team adapted a crop simulation model known as Decision Support System for Agrotechnology Transfer (DSSAT) to estimate how efficiently cereal rye could remove nitrate from tile drainage water if planted widely across Illinois. In their new study, the team used DSSAT again to forecast growth of cereal rye, as well as corn and soybean, in the near-term (2021-2040) and far-term (2041-2060) under two climate scenarios for Illinois: a best-case-scenario and a business-as-usual case. 

The team took a piecemeal approach, modeling each component of the system separately before combining them into a holistic prediction for the impact of cover crops under climate change. 

To start, they modeled climate impacts on cash crop yield and cover crop biomass. Corn yield decreased in most Illinois regions, future timeframes, and climate scenarios, with average yield coming in 11.5% below to 3.8% above present averages. Soybean yield, however, mostly increased across regions and scenarios, with yields forecasted up to 27.5% higher than present averages. Finally, the model predicted cover crop biomass would boom as a result of climate change, with increases between 25% and 103% beyond current figures.  

“Corn and soybean are two completely different kinds of crop, which is reflected in our results. The change in yield is due to multiple factors. Apart from the projected increase in temperature, the yield response is affected differently for each crop by changes in rainfall patterns and elevated CO2 levels in the future. We also found cover crops strongly benefit from warmer winter weather,” said study co-author Rabin Bhattarai, associate professor in the Department of Agricultural and Biological Engineering, a shared unit of the College of Agricultural, Consumer and Environmental Sciences (ACES) and The Grainger College of Engineering at Illinois. 

Looking at nitrogen loss under climate change, the team predicted 24% greater loss in the near-term future, rising to about 42% by 2060. 

“Warmer soil means microbes will be more active in converting nitrogen in organic matter to ammonium and then to nitrate in the soil. And if you have more nitrate in the soil, the potential for loss is higher,” Bhattarai said. “We already see high nutrient losses during warm, wet springs, even before crops are planted or fertilizer is applied. That nitrogen is escaping from the soil itself.” 

With these baselines established, the researchers began making connections. First, they looked at the impact of cover crops on cash crop yield. In their previous DSSAT study, the researchers found growing cereal rye before corn and soybean had a slightly positive effect on yield. According to Bhattarai, cover crops slowly scavenge soil nitrogen throughout the winter and return the nutrient to the crop, providing a growth boost, when terminated and incorporated into the soil. 

Under climate change, hungry swards of cover crops could deplete both soil water and nitrogen, even accounting for greater nitrogen availability predicted during warmer winters. Then, at termination, the sheer amount of cover crop biomass could overwhelm the mineralization apparatus of the soil, keeping some nitrogen locked up and unavailable for cash crops. However, although the yield benefit disappeared under future climate scenarios, the analysis did not reveal a yield penalty for growing cover crops.

“Whether you use cover crops or not, you're going to see a decline in corn yield in the future. The same applies to soybean. You may gain soybean yield whether or not cover crops are present,” Bhattarai said. “If you see any impact on the cash crop yield, it's not due to the cover crop, it's due to the changing climate.” 

Finally, the team looked at cover crop impact on nitrogen loss under climate change. Relative to current conditions in which cover crops reduce tile drainage nitrogen by about 30%, cover crops are likely to become less effective under future scenarios, with as low as 11% reduction under far-term worst-case-scenario predictions. 

“You don't get the same benefit that you get now. You will see better growth of cover crops with the warmer temperatures, but mineralization will overtake their ability to take up nitrogen; more supply than demand,” Bhattarai said. “Cover crops will help; they will still be effective at reducing loss. But the efficiency will drop.”

 He added that farmers will have to augment cover crops with additional best management practices to meet nutrient loss reduction goals in the face of a changing climate. 

The study, “Sustainability of cover cropping practice with changing climate in Illinois,” is published in the Journal of Environmental Management [DOI: 10.1016/j.jenvman.2023.117946]. Authors include Rishabh Gupta, Rabin Bhattarai, Hamze Dokoohaki, Shalamar Armstrong, Jonathan Coppess, and Prasanta Kalita. The research was supported by the Illinois Nutrient Research and Education Council (NREC) [project #017–3-360574–222]. Partial support was also provided by the USDA National Institute of Food and Agriculture.

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JOURNAL

Journal of Environmental Management

DOI

10.1016/j.jenvman.2023.117946 

Bezos Earth Fund grants $12 million to Smithsonian to support major forest carbon project

Science-based carbon storage biomass verification

Grant and Award Announcement

SMITHSONIAN TROPICAL RESEARCH INSTITUTE

 

IMAGE: THE GEO-TREES PROJECT WILL PROVIDE HIGHLY ACCURATE ESTIMATES OF THE CARBON STORED BY DIFFERENT FORESTS AROUND THE GLOBE BASED ON ON-THE-GROUND TREE MEASUREMENTS, WITH TERRESTRIAL AND AERIAL LASER SCANS (LIDAR). view more 

CREDIT: CREDIT: JORGE ALEMAN, STRI

By conserving and replanting forests, the world buys time until it brings other climate and sustainability solutions online. As a critical step toward this goal, the Smithsonian Tropical Research Institute (STRI) received a $12 million grant from the Bezos Earth Fund to support GEO-TREES. This international consortium is the first worldwide system to independently ensure the accuracy of satellite monitoring of forest biomass—a way to measure carbon stored in trees—in all forest types and conditions. The GEO-TREES alliance offers a freely accessible database that integrates on-the-ground measurements of individual trees with terrestrial and aerial laser scans (LiDAR) of forests—a highly accurate way to verify forest carbon estimates based on satellite images.

“The GEO-TREES project is as exciting as it is essential for our detailed understanding of the interplay between tropical forests and carbon capture,” said Smithsonian Secretary Lonnie Bunch. “Scientific research has been at the heart of the Smithsonian’s mission for more than 176 years, and the grant from the Bezos Earth Fund demonstrates the value of support and collaboration in the search for solutions to our planet’s shared challenges.”

“The Bezos Earth Fund is pleased to support and partner on this powerful project to use decades of long-term data to understand forest carbon,” said Cristián Samper, managing director and leader for nature solutions at the Bezos Earth Fund. “There are very few places like the Smithsonian Tropical Research Institute, where the tropical rainforest has been studied for 100 years. The longevity of tropical research at the Smithsonian, together with the expansion of a global network of forest study sites, will help address the climate crisis we face in a way not possible anywhere else.”

At the heart of the GEO-TREES system is the Smithsonian’s ForestGEO network, directed by STRI staff scientist, Stuart Davies, working closely with partners around the globe. With 40 years’ experience rooted in the tropics, ForestGEO is the most extensive, long-term, large-scale, forest-monitoring network in the world, representing researchers at 76 study sites in 29 countries. The ForestGEO project is distinguished by its emphasis on partnership, incorporating the need for data with local conservation and management goals.

Space agencies worldwide are putting satellites into orbit to image forests in real time, but for scientists to verify carbon-storage numbers from these images, they must calibrate the satellite measurements against high-quality ground-based measurements. To gather high-quality measurements, scientists are intensively studying forest biomass reference sites in mature and younger forests, leveraging several partner forest-plot networks.

Most of the grant will be spent in tropical countries—many of them middle- and low-income—not only for data collection, but to strengthen capacity for local stakeholders and early-career scientists. This effort will enable them to combine field data collection with cutting-edge technology to monitor and evaluate the carbon stored in their forests.

“Tropical forests are the most important, best-understood, carbon-capture devices in the world,” said Joshua Tewksbury, director of STRI, which will administer the funds via its ForestGEO program. “But to make large-scale carbon capture a reality, we need to engage all sectors of society. And we can only do that if we can clearly show where the carbon is—and how carbon stocks change in real time, at scales that landowners, countries and investors care about. The Smithsonian, with hundreds of partners around the world, has taken on the challenge of providing the definitive ground-based global forest database to make this work possible.”

Each tree species in the world is unique: a balsa tree’s soft wood stores much less carbon than an ebony or rosewood tree’s dense wood. The age of each forest and the species present—which vary wildly from place to place—affect how much carbon is stored. Trees absorb different amounts of carbon on sunny days compared with cloudy days, and carbon storage depends on available water and nutrients. Thus, quantifying the biomass of complex forests requires significant expertise.

“The Smithsonian recently launched Life on a Sustainable Planet, which harnesses all Smithsonian resources to focus on solutions for our changing planet,” said Ellen Stofan, Under Secretary for Science and Research at the Smithsonian Institution. “The GEO-TREES project is a major component of that effort, and this grant from the Bezos Earth Fund helps us take a significant step forward in strengthening connections between people and nature.”

STRI, headquartered in Panama City, Panama, is a unit of the Smithsonian. The institute furthers the understanding of tropical biodiversity and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Watch STRI’s video and visit the institute on its website and on Facebook, Twitter and Instagram for updates.

Tropical forests pull carbon dioxide out of the atmosphere where it causes global warming and store it as wood. But the amount of carbon stored varies depending on tree species, age, climate conditions and other factors. Verifiable estimates of carbon stored in forests are necessary to calculate carbon credits.

CREDIT

Credit: Steve Paton, STRI

Developer dollars not enough to save species

Peer-Reviewed Publication

UNIVERSITY OF QUEENSLAND

 

IMAGE: CREDIT TO COURTNEY MORGANS view more 

CREDIT: COURTNEY MORGANS

Financial payments made by land developers to offset their impacts on threatened species may fall short, according to University of Queensland-led research.

Professor Jonathan Rhodes from the School of the Environment focused on koala populations in the fast-developing South East Queensland region and a government scheme which allows developers to make financial payments to compensate for environmental consequences. 

“Just like when you make a financial contribution to offset your carbon emissions when purchasing a flight, developers can make a financial payment to the Queensland Government to offset their impacts on koala habitat,” Professor Rhodes said.

“These payments are then used to plant trees to restore koala habitat in offset sites elsewhere.

“But we found that when suitable places to restore koala habitat are difficult to find, the financial payments required under the Queensland Environmental Offset Policy are often insufficient to achieve its intended outcomes and this is a major problem.

“In the South East Queensland region, only 0.7 of 13.4 hectares of impacts on koala habitat offset through financial payments since 2018 so far have offset sites in place and this is concerning for the future of this beloved, endangered species.

“Unfortunately, land supply can make suitable offset sites hard to find and this pushes up the cost of delivering habitat restoration and securing those sites in the long-term can fail to guarantee sufficient gains in habitat to counterbalance losses.”

Professor Rhodes said funding from developer payments may be insufficient to buy enough offset sites for habitat restoration.

“South East Queensland is the most densely human-populated area in the state, growing from 2.4 million people in 2001 to 3.5 million people in 2016, with 5.3 million people expected by 2041,” Professor Rhodes said.

“It is also home to an enormous number of threatened species, including some of the most significant koala populations in Australia which have declined 50 to 80 per cent over the past two decades.

“This problem will become worse as the region expands and competition for land for development intensifies, making offset sites either impossible to find or more expensive to secure.”

The study mapped and modelled development in eight Local Government Areas (LGAs) within the South East Queensland Planning Region, applying ecological data and projecting anticipated development and offset outcomes.

While the researchers propose some solutions, they also call for consideration of immediate changes to the current offset policy.

“On one hand, financial payments by developers can provide flexibility for the State Government to deliver the most effective offsets to help threatened species such as koalas, but on the other hand, it’s essential that developers pay the true cost of those offsets,” Professor Rhodes said.

“Otherwise, offsets will fall short of compensating for habitat losses and species will continue to decline or taxpayers via the State Government will have to make up the shortfall in developer contributions.”

The research is published in People and Nature.

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JOURNAL

People and Nature

DOI

10.1002/pan3.10494 

ARTICLE TITLE

Performance of habitat offsets for species conservation in dynamic human-modified landscapes

ARTICLE PUBLICATION DATE

10-Jul-2023

Do investors incorporate financial materiality of environmental information in their risk evaluation?

Evaluating a company’s environmental performance based on financial materiality provides a better perspective for investors to understand the environmental risk involved.

Peer-Reviewed Publication

KYUSHU UNIVERSITY

 

IMAGE: FINANCIAL MATERIALITY PROVIDES BETTER LENS FOR INVESTORS TO ADEQUATELY CAPTURE THE ENVIRONMENTAL RISK view more 

CREDIT: JUN XIE, YOSHITAKA TANAKA, ALEXANDER RYOTA KEELEY, HIDEMICHI FUJII, SHUNSUKE MANAGI

Financial materiality pertains to crucial and pertinent data that a company is obligated to reveal in its financial statements. It provides companies with the insights necessary to discern elements influencing their performance and profitability, thereby enabling them to mitigate risks and captivate potential investors. There have been conflicts between shareholders and stakeholders regarding issues that are not directly related to finances, like environmental and social concerns. However, ignoring these factors like ESG (environmental, social and governance) could pose risks to both companies and investors.

Researchers at Kyushu University found that investors consider a company’s response to material environmental issues as a significant risk when deciding whether to invest in it. This highlights the importance of providing information that promotes communication between companies and investors for sustainable investment.

The more people become interested in sustainable investing, the concept of financial materiality is being closely examined. The Sustainability Accounting Standards Board (SASB) has developed standards specifically for different industries to help companies disclose sustainability information that is financially relevant.

The study analyzed data from 1,766 companies listed in the US between 2011 and 2020. By incorporating financial materiality into environmental performance assessments, this study provides new evidence of sustainability investments from the perspective of shareholders. The researchers made three important findings:

・The importance of each evaluation criterion for sustainable investment varies depending on the characteristics of each company.

・Shareholders see a lack of consideration for financial materiality in management strategies as a significant risk.

・Evaluating a company’s environmental performance based on financial materiality provides a better perspective for investors to understand the environmental risk involved. (See the reference figure)

With the growing interest in sustainable investing, there is a need to reevaluate how environmental information is reported by companies. Considering ESG factors in investment strategies provides scientific evidence for the importance of including financial materiality to achieve a sustainable and resilient economy. Using the financial materiality standards provided by SASB could be an effective way to assess and manage corporate environmental risks.

 

This research was supported by Ministry of Education, Culture, Sports, Science and Technology, Grant/Award Numbers: 20H00648, 22K20176; New Energy and Industrial Technology Development Organization, Grant/Award Number: P14026

 

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For more information about this research, see Xie, J., Tanaka, Y., Keeley, A. R., Fujii,H., & Managi, S. (2023). Do investors incorporate financial materiality? Remapping the environmental information in corporate sustainability reporting. Corporate Social Responsibility and Environmental Management, 1–29. https://doi.org/10.1002/csr.2524

 

About Kyushu University 
Kyushu University is one of Japan’s leading research-oriented institutes of higher education since its founding in 1911. Home to around 19,000 students and 8,000 faculty and staff, Kyushu U's world-class research centers cover a wide range of study areas and research fields, from the humanities and arts to engineering and medical sciences. Its multiple campuses—including one of the largest in Japan—are located around Fukuoka City, a coastal metropolis on the southwestern Japanese island of Kyushu that is frequently ranked among the world’s most livable cities and historically known as Japan’s gateway to Asia. Through its Vision 2030, Kyushu U will ‘Drive Social Change with Integrative Knowledge.’ Its synergistic application of knowledge will encompass all of academia and solve issues in society while innovating new systems for a better future.

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JOURNAL

Corporate Social Responsibility and Environmental Management

DOI

10.1002/csr.2524 

ARTICLE TITLE

Do investors incorporate financial materiality? Remapping the environmental information in corporate sustainability reporting

Climate-neutral air travel: Is it possible?

Peer-Reviewed Publication

PAUL SCHERRER INSTITUTE

 

IMAGE: CHRISTIAN BAUER, WISSENSCHAFTLER IM LABOR FÜR ENERGIESYSTEM-ANALYSE AM PSI view more 

CREDIT: PAUL SCHERRER INSTITUT/MARKUS FISCHER

Researchers at the Paul Scherrer Institute PSI and ETH Zurich have performed calculations to work out how air traffic could become climate-neutral by 2050. They conclude that simply replacing fossil aviation fuel with sustainable synthetic fuels will not be enough. Air traffic would also have to be reduced. The researchers are publishing their results today in the journal Nature Communications.

The European Union aims to be climate neutral by 2050, a target that was set by the European Parliament in 2021. Switzerland is pursuing the same goal. The aviation sector, which is responsible for 3.5 percent of global warming, is expected to contribute its fair share – especially since the greenhouse gas emissions of aircraft are two to three times higher per passenger or freight kilometre than in other transport sectors. The International Civil Aviation Organisation (ICAO) and many airlines have therefore announced their intention to reduce CO2 emissions to zero by 2050 or to become climate neutral.

In a new study, researchers at PSI and ETH Zurich have now calculated whether this can be achieved, and how. “An important question is what exactly we mean by zero carbon or climate neutrality,” says Romain Sacchi of PSI’s Laboratory for Energy Systems Analysis, one of the study’s two lead authors. If this is only referring to the CO2 emitted by aircraft actually in the air, adds his co-author Viola Becattini from ETH Zurich, this does not go nearly far enough. Because assuming that air traffic continues to grow as it has in the past, the calculations predict that the CO2 emissions of aircraft will only account for about 20 percent of their total climate impact by 2050. In order to make aviation as a whole climate neutral, it is necessary to ensure that not only flying but also the production of fuel and the entire aviation infrastructure have no further impact on the climate.

However, the study concludes that this cannot be achieved by 2050 using the climate measures that are currently being pursued in flight operations. “New engines, climate-friendly fuels and filtering CO2 out of the atmosphere in order to store it underground (carbon capture and storage, or CCS) will not get us there on their own,” says Marco Mazzotti, Professor of Process Engineering at ETH. “On top of this, we need to reduce air traffic.”

Non-CO2 effects play a major role

In their study, Sacchi and Becattini looked at various different scenarios. These showed, on the one hand, that while the climate impact of the infrastructure, i.e. manufacturing aircraft and building and operating airports, does need to be taken into account, it is comparatively small overall for the period up until 2050 and beyond. The impact of flying itself on the climate, and of the emissions from producing the fuel are far greater. That in itself was nothing new.

What had been less clear before was the importance of so-called non-CO2 effects, which occur in addition to CO2 emissions. The bulk of the greenhouse effect caused by aviation is not due to the carbon released into the atmosphere by burning aviation fuel, but to the particulate matter (soot) and nitrogen oxides that are also released and that react in the air to form methane and ozone, water vapour and the condensation trails that lead to the formation of cirrus clouds in the upper atmosphere. “Many analyses and ‘net zero’ pledges so far have ignored these factors,” says Romain Sacchi. “Or they have not been calculated correctly.”

It is customary to express emissions and effects like these in terms of CO2 equivalents when calculating the overall balance. “But the methods and values used to date have proved to be inappropriate,” says Marco Mazzotti. “We therefore adopted a more precise approach.” The methods they used take into account one major difference between the various factors: non-CO2 effects are much more short-lived than CO2, which is why they are also called “short-lived climate forcers”, or SLCFs for short. While about half of the emitted carbon dioxide is absorbed by forests and oceans, the other half remains in the air for thousands of years, dispersing and acting as a greenhouse gas. Methane, on the other hand, has a much greater impact on the climate, but decomposes within a few years; contrails and the resulting clouds dissipate within hours. “The problem is that we are producing more and more SLCFs as air traffic increases, so these are adding up instead of disappearing quickly. As a result, they exert their enormous greenhouse impact over longer periods of time,” says Viola Becattini. It’s like a bathtub with both the drain and the tap open: as long as the tap lets in more water than can escape through the drain, the bathtub will keep getting fuller – until eventually it overflows.

Climate-friendly fuel alone does not achieve the goal – but it helps

“But this analogy also demonstrates that the crucial lever is under our control: the volume of air traffic,” Romain Sacchi points out. “By flying less instead of more often, in other words closing the tap instead of opening it, we can actually cool the atmosphere and push the greenhouse effect caused by aviation towards zero.” This is not to say that we must stop flying altogether. The calculations performed in the study show that for aviation to achieve climate neutrality by 2050, air traffic will need to be reduced by 0.8 percent every year – in conjunction with underground carbon dioxide storage – if we continue to use fossil fuels. This would bring it down to about 80 percent of today’s volume by 2050. If we manage to switch to more climate-friendly fuels based on electricity from renewables, 0.4 percent per year will be sufficient.

The study also took a closer look at these new fuels. Researchers around the world are working to replace conventional petroleum-based engines. As in road transport, this could be achieved by using electric batteries, fuel cells or the direct combustion of hydrogen. However, the available energy density is only sufficient for small aircraft on short routes, or in the case of hydrogen also for medium-size planes on medium-haul flights. Yet large aircraft on long-haul flights of more than 4000 kilometres account for the majority of global air traffic and greenhouse gas emissions from aviation.

Synthetic aviation fuel has pros and cons

In addition, propulsion technologies for the aviation industry based on electricity or hydrogen are far from being ready for a widespread roll-out. So-called Sustainable Aviation Fuel (SAF) is therefore viewed as the industry’s great hope. This man-made aviation fuel could replace petroleum-based aviation fuel more or less one-to-one, without the need to redesign turbines and aircraft.

SAF can be produced from CO2 and water via a production cascade. The CO2 is extracted from the air using a process known as air capture, and hydrogen can be obtained from water by electrolysis. “If the necessary processes are carried out entirely using renewable energy, SAF is virtually climate-neutral,” says Christian Bauer from the PSI Laboratory for Energy Systems Analysis, who was involved in the study. “This makes us less dependent on fossil fuels.” Another advantage of SAF is that it produces fewer SLCFs, which would have to be offset by capturing equivalent amounts of CO2 from the air and storing them underground. This is significant because CO2 storage capacity is limited and not reserved exclusively for the aviation industry.

Air tickets three times more expensive

SAF also has certain disadvantages though, in that it takes far more energy to produce than conventional aviation fuel. This is mainly because producing hydrogen via electrolysis takes a lot of electricity. In addition, energy is lost at every step in the production process – air capture, electrolysis and synthesisation. Using large amounts of electrical power, in turn, means expending more resources such as water and land. SAF is also expensive: not just in terms of the electrical power required, but also the cost of carbon capture and electrolysis plants, which makes it four to seven times more expensive than conventional aviation fuel. In other words, the widespread use of SAF makes carbon-neutral aviation a possibility, but it also costs more resources and more money. This means that flying will have to become even more expensive than it already needs to be in order to meet the climate targets. “Anyone buying a ticket today can pay a few extra euros to make their flight supposedly carbon neutral, by investing this money in climate protection,” says Romain Sacchi. “But this is greenwashing, because many of these measures for offsetting carbon are ineffective. To fully offset the actual climate impact, tickets would have to cost about three times as much as they do today.”

“Such a hefty price hike should significantly reduce the demand for flights and bring us closer to the goal of climate neutrality,” says Viola Becattini. In addition, SAF production is expected to become cheaper and more efficient over the years as quantities increases, and this will have a positive effect on the carbon footprint. The study took such dynamics into account – including the fact that the electricity mix used to produce SAF is shifting. This distinguishes the analysis from most others.

“The bottom line is that there is no magic bullet for achieving climate neutrality in aviation by 2050,” says Sacchi. “We cannot continue as before. But if we develop the infrastructure for storing CO2 underground and producing SAF quickly and efficiently, while also reducing our demand for air travel, we could succeed."

 

Text: Jan Berndorff

 

About PSI

The Paul Scherrer Institute PSI develops, builds and operates large, complex research facilities and makes them available to the national and international research community. The institute's own key research priorities are in the fields of matter and materials, energy and environment and human health. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2200 people, thus being the largest research institute in Switzerland. The annual budget amounts to approximately CHF 420 million. PSI is part of the ETH Domain, with the other members being the two Swiss Federal Institutes of Technology, ETH Zurich and EPFL Lausanne, as well as Eawag (Swiss Federal Institute of Aquatic Science and Technology), Empa (Swiss Federal Laboratories for Materials Science and Technology) and WSL (Swiss Federal Institute for Forest, Snow and Landscape Research). Insight into the exciting research of the PSI with changing focal points is provided 3 times a year in the publication 5232 - The Magazine of the Paul Scherrer Institute.

 

 

 

Contact:

Christian Bauer

Senior Researcher at the Laboratory for Energy Systems Analysis, Technology Assessment Group

Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland

Telephone: +41 56 310 23 91, e-mail: christian.bauer@psi.ch [German, English]

 

 

Original publication:

How to make climate-neutral aviation fly

Romain Sacchi, Viola Becattini et al.

Nature Communications 06.07.2023

DOI: 10.1038/s41467-023-39749-y

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JOURNAL

Nature Communications

DOI

10.1038/s41467-023-39749-y 

METHOD OF RESEARCH

Computational simulation/modeling

ARTICLE TITLE

How to make climate-neutral aviation fly

ARTICLE PUBLICATION DATE

6-Jul-2023

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