GT/ Breakthrough in separating plastic waste

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Paradigm

32 min readJan 14, 2022

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Energy & green technology biweekly vol.15, 30th December — 14th January

TL;DR

Researchers have now developed a new camera technology that can see the difference between 12 different types of plastics. We can now separate plastics according to their chemical composition. This is absolutely ground-breaking and it will increase the rate of recycling of plastics immensely. The technology has already been tested at pilot scale and it will be implemented at an industrial scale in spring 2022.
Researchers have uncovered a way to improve the efficiency of a type of grid-scale storage crucial for a global transition toward renewable energy.
Path-setting findings demonstrate for the first time a novel regime for confining heat in stellarators. The demonstration could advance the twisty design as a blueprint for future fusion power plants.
A new study reveals why some attempts to convert carbon dioxide into fuel have failed, and offers possible solutions.
Carbon capture and storage (CCS) is one of the new technologies that scientists hope will play an important role in tackling the climate crisis. It involves the capture of CO2 from emissions from industrial processes, or from the burning of fossil fuels in power generation, which is then stored underground in geological formations. CCS will also be key if we want to produce ‘clean-burning’ hydrogen from hydrocarbon systems.
Microbiologists show that methanogenic archaea do not always need to form methane to survive. It is possible to bypass methanogenesis with the seemingly simpler and more environmentally friendly acetogenic energy metabolism. These new findings provide evidence that methanogens are not nearly as metabolically limited as previously thought, and suggest that methanogenesis may have evolved from the acetyl-CoA pathway — an important step towards fully understanding the ecology, biotechnology, and evolution of archaea.
The world faces an increasing amount of carbon dioxide in the atmosphere and a shortage of carbon in the soil. However, bioenergy sorghum can provide meaningful relief from both problems, according to a new study.
Predator species may buffer the negative impacts of climate change by mitigating against the loss of biodiversity, according to new research. The team of scientists behind the discovery say their findings underline the importance of conserving biodiversity, and top predators in particular, and highlight the potential for species extinctions to worsen the effects of climate change on ecosystems.
Fine particle pollution affects most of the world’s population, causing respiratory and cardiovascular diseases as well as premature deaths, all at a cost to society. A multidisciplinary research team has now drawn up various scenarios that would reduce the mortality caused by fine particles by two thirds over the entire conurbation, and has shown that the benefits obtained would exceed the costs of the policies implemented.
Egg white is one of the most important protein ingredients for the food industry. The first assessment of the environmental impact of egg white protein — ovalbumin — production shows that the ovalbumin produced by precision fermentation reduced land use requirements by almost 90 per cent and greenhouse gases by 31–55 per cent compared to the production of its chicken-based counterpart.
And more!

Green Technology Market

Green technology is an applicable combination of advanced tools and solutions to conserve natural resources and environment, minimize or mitigate negative impacts from human activities on the environment, and ensure sustainability development. Green technology is also referred to as clean technology or environmental technology which includes technologies, such as IoT, AI, analytics, blockchain, digital twin, security, and cloud, which collect, integrate, and analyze data from various real-time data sources, such as sensors, cameras, and Global Positioning System (GPS).

Green technology, also known as sustainable technology, protects the environment by using various forms of sustainable energy. Some of the best examples of green technologies include solar panels, LED lighting, wind energy, electric vehicles, vertical farming, and composting.

The global Green Technology and Sustainability market size to grow from USD 11.2 billion in 2020 to USD 36.6 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 26.6% during the forecast period. The growing consumer and industrial interest for the use of clean energy resources to conserve environment and increasing use of Radio Frequency Identification sensors across industries are driving the adoption of green technology and sustainability solutions and services in the market.

The blockchain segment is estimated to grow at the highest CAGR: Energy-intensive cryptocurrency mining has caused a spike in carbon emission, and hence blockchain is capable of driving innovation in the field of green technology.

Latest News

Latest Research

Plastic classification via in-line hyperspectral camera analysis and unsupervised machine learning

by Martin L. Henriksen, Celine B. Karlsen, Pernille Klarskov, Mogens Hinge in Vibrational Spectroscopy

In contrast to common perceptions, plastic is in no way near one material. Rather, it is a combination of many materials (polymers) with different chemical compounds and additives such as pigments or fibres, depending on its use. It is very difficult to tell the difference between different types of plastics, and this is what makes it difficult to separate and recycle them.

In collaboration with Vestforbrænding, Dansk Affaldsminimering Aps, and PLASTIX, researchers from the Department of Biological and Chemical Engineering at Aarhus University have now developed a new camera technology that can see the difference between 12 different types of plastics (PE, PP, PET, PS, PVC, PVDF, POM, PEEK, ABS, PMMA, PC, and PA12). Together, these constitute the vast majority of household plastic types.

Left, four disks (left to right: PEEK, POM N, POM N, and POM B) presented at 1204 nm and POM N (marked with the area of averaging). Right, hyperspectral spectrum of POM N from scans averaged over 1, 10, 25, and 200 pixels, respectively.

The technology makes it possible to separate plastics based on a purer chemical composition than is possible today, and this opens up for completely new opportunities to recycle plastics. The technology has been tested at pilot scale and is planned to be implemented at PLASTIX and Dansk Affaldsminimering Aps in spring 2022.

“With this technology, we can now see the difference between all types of consumer plastics and several high-performance plastics. We can even see the difference between plastics that consist of the same chemical building blocks, but which are structured slightly differently. We use a hyperspectral camera in the infrared area, and machine learning to analyse and categorise the type of plastic directly on the conveyor belt. The plastic can then be separated into different types. It’s a breakthrough that will have a huge impact on all plastics separation,” says Associate Professor Mogens Hinge, who is heading the project at Aarhus University.

Average spectra measured 10 ABS samples (Norm.), 5 ABS samples surface treated with a wood rasp (Rasp), and 5 ABS samples surface treated with screwdriver indentations (Screw.).

Plastics are currently separated using near-infrared technology (NIR) or via density tests (floats/sinks in water). These methods can separate certain plastic fractions (for example PE, PP, and PET), but not with the same accuracy as the new technology, and therefore not with the chemical purity in the composition, and this is vital to be able to increase the recycling rate of waste plastic.

“The technology we’ve developed in collaboration with the university is nothing short of a breakthrough for our ability to recycle plastics. We look forward to installing the technology in our processing hall and starting in earnest on the long journey towards 100% utilisation of waste plastic,” says Hans Axel Kristensen, CEO of PLASTIX.

Plastic must be at least 96% pure by polymer type to be recycled in conventional industry. This means that the plastic has to be separated to an almost pure product in terms of chemical composition.

Score plot of the first and second principal component (PC1 and PC2, respectively) from the principal component analysis made on the Savitzky-Golay filtered HC spectra. Calculated cluster centers (black circle), the unknown samples (X), symbols are the known material type, and a color is assigned to the predicted material type.

Using the new technology, we are now a big step along the way, says Associate Professor Mogens Hinge, who stresses that the technology is continuously being developed and that data indicates it may be possible to differentiate even further between polymer types and additives before long.

The hyper-spectral camera technology has been developed in cross-disciplinary collaboration, including BSc and MSc engineering students and researchers at the Department of Biological and Chemical Engineering at Aarhus University, as well as experts from the participating companies.

Rapid microbial methanogenesis during CO2 storage in hydrocarbon reservoirs

by R. L. Tyne, P. H. Barry, M. Lawson, D. J. Byrne, O. Warr, H. Xie, D. J. Hillegonds, M. Formolo, Z. M. Summers, B. Skinner, J. M. Eiler, C. J. Ballentine in Nature

Atmospheric carbon dioxide (CO2) levels have increased significantly over the last 50 years, resulting in higher global temperatures and abrupt changes to Earth’s climate. Carbon capture and storage (CCS) is one of the new technologies that scientists hope will play an important role in tackling the climate crisis. It involves the capture of CO2 from emissions from industrial processes, or from the burning of fossil fuels in power generation, which is then stored underground in geological formations. CCS will also be key if we want to produce “clean-burning” hydrogen from hydrocarbon systems.

The UK government recently selected four sites to develop multi-billion-pound CCS projects as part of its scheme to cut 20–30m tonnes of CO2 per year by 2030 from heavy industry. Other countries have made similar carbon reduction commitments.

**Map of study area showing locations of the Olla and Nebo-Hemphill oil fields as well as the Black Lake Oil Field, from which the injected CO2 was sourced.**

Depleted hydrocarbon reservoirs have a smaller (10%) storage potential compared to deep saline aquifers but are seen as a critical early opportunity in developing geological CO2 storage technologies. Fortuitously, CO2 has historically been injected into numerous depleted hydrocarbon reservoirs as a means of enhanced oil recovery (CO2-EOR). This provides a unique chance to evaluate the (bio)geochemical behaviour of injected carbon over engineering timescales.

‘CCS will be a key tool in our battle to avert climate change. Understanding how CCS works in practice, in addition tocomputer modelling and lab-based experiments, is essential to provide confidence in safe and secure CO2 geologicalsequestration.’ Said Dr. Rebecca Tyne, Dept Earth Science, The University of Oxford

In a paper, Dr. Rebecca Tyne and Prof. Chris Ballentine from Oxford University, lead a team of international collaborators to investigate the behaviour of CO2 within a CO2-EOR flooded oil field in Louisiana, USA. They compared (bio)geochemical composition of the CO2-EOR flooded field with that of an adjacent field, which was never subjected to CO2-EOR. Data suggest that up to 74% of CO2 left behind by CO2-EOR was dissolved in the groundwater. Unexpectedly, it also revealed, that microbial methanogenesis converted as much as 13–19% of the injected CO2 to methane, which is a stronger greenhouse gas than CO2.

**The δ13C of CO2 in the Olla (CO2 injected field) samples.**

This study is the first to integrate state of the art isotopic tracers (noble gas, clumped and stable isotope data) with microbiological data to investigate the fate of the injected CO2.

‘Methane is less soluble, less compressible and less reactive than CO2, so, if produced, the reduces the amount of CO2 we can safely inject into these sites. However, now this process has been identified, we can take it into account in future CCS site selection.’ Said Prof. Chris Ballentine, Dept. Earth Sciences, The University of Oxford.

**Schematic of the processes occurring within the Olla Oil Field and resulting changes in the isotopic composition within the field.**

Additionally, the authors suggest that this process is occurring at other CO2-rich natural gas fields and CO2-EOR oil fields. Temperature is a critical consideration, and many CCS geological targets will be too deep and hot for microbesto operate. However, if CO2 leaks from deeper hot systems into similar shallower colder geological structures, where microbes are present, this process could occur. This research is critical for identifying future CCS targets, establishing safe baseline conditions and long-term monitoring programs, which are essential for low-risk, long-term carbon storage.

Thermochemical heat recuperation for compressed air energy storage

by Fuqiong Lei, David Korba, Wei Huang, Kelvin Randhir, Like Li, Nick AuYeung in Energy Conversion and Management

Research by the Oregon State University College of Engineering has uncovered a way to improve the efficiency of a type of grid-scale storage crucial for a global transition toward renewable energy.

Moving toward net-zero carbon emissions means dealing with the intermittent, unpredictable nature of green power sources such as wind and solar and also overcoming supply and demand mismatches, said OSU’s Nick AuYeung, who led the study along with Ph.D. student Fuqiong Lei. Those challenges, AuYeung notes, necessitate energy storage through means beyond pumped hydro plants, which feature a turbine between two water reservoirs of different elevations, and huge lithium-ion batteries.

The computer modeling study spearheaded by AuYeung, associate professor of chemical engineering, and Lei found that one of those additional energy storage technologies, compressed air, could be improved via chemical reactions. The reversible reactions can absorb energy in the form of heat and subsequently conserve energy that would otherwise be lost.

A schematic of a CAES system incorporating thermochemical energy storage.

As their names suggest, the liquid and compressed air techniques harness energy that can be accessed when needed by allowing stored air — either pressurized or cooled to a liquid form — to expand and pass through electricity-generating turbines. However, both CAES, as compressed air energy storage is typically expressed, and LAES (liquid air) score somewhat poorly in a category known as round-trip efficiency, AuYeung explains. With either, only about half the energy put in can be pulled out — think of it as making a bank deposit of $1,000 but, due to various charges, only about $500 is available for withdrawal.

“An advantage of CAES is that it allows energy to be stored at large scales, which is a hurdle for electrochemical battery technologies,” he said. “But a major challenge for traditional CAES is reaching high round-trip efficiency.”

In a conventional CAES process, electricity is used to compress air, and the compressed air is stored below ground in a cavern or in a pressure vessel, AuYeung said. When the air is compressed, its temperature rises, but that heat is typically regarded as waste and thus goes unrecovered and unused.

“To discharge the air to produce power, it’s usually heated with natural gas to increase the turbine feed’s enthalpy, the total system energy,” he said. “Factoring in heat lost during storage, the result is that the overall round-trip efficiency — the ratio of turbine output work to work consumed through compression — is only between 40% and 50%.”

AuYeung and collaborators at OSU, Mississippi State University and Michigan State University came up with a storage scheme to improve that efficiency — thermochemically recovering lost heat — and developed a mathematical model for its design and operation. An advantage of thermochemical energy storage, or TCES, over other methods is a higher energy density made possible by capturing heat in the form of chemical bonds, he said.

Using their model, the researchers analyzed the performance of TCES incorporated into thermal energy storage via “packed beds” — vessels filled with some kind of solid packing medium, where energy reaches the solid by means of a heat transfer fluid such as air. The filler material is typically alumina, ceramic or crushed rock. Packed beds are classified as “sensible” storage because energy is harnessed by virtue of the filler material changing temperature.

“We looked at TCES with packed beds filled with rocks and barium oxides,” AuYeung said. “Our results showed a similar round-trip efficiency between beds with TCES and beds without because of the relatively low heat capacity and heat of reaction for the barium oxides. We got to 60% round-trip efficiency for both systems with a 20-hour storage time after charge. Other means of thermal storage cannot store the heat for long periods of time since they cool down.”

Importantly, he noted, with TCES material placed atop the packed beds, there was a more stable turbine air inlet temperature — higher for longer — which is a key to optimal power generation and thus desirable to utilities. In addition, AuYeung said the model shows that with future advanced materials, round-trip efficiency and storage time could improve as well.

“To better illustrate the potential of the concept, we came up with a hypothetical material with the same heat capacity as rocks but a thermochemical storage capacity three times that of barium oxides, and we looked at that hypothetical material in our model,” he said. “Results showed that a potential round-trip efficiency improvement of more than 5% can be obtained, as well as longer storage durations. Also, 45% less filler volume would be needed to achieve storage capacity similar to rock-filled beds.”

AuYeung said the barium chemistry the initial model was based on was the most obvious that came to mind for the researchers’ but has a downside because its heat capacity is fairly low.

“There are non-oxygen chemistries such as hydrates and carbonates that have the hypothetical properties — high heat capacity, high heat of reaction — we looked at, but right now we haven’t identified one for a redox material that operates on oxygen swing,” he said. “A next step perhaps for us, or for others with more materials expertise, would be to try to discover new materials.”

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

by F. Nespoli, S. Masuzaki, K. Tanaka, N. Ashikawa, M. Shoji, E. P. Gilson, R. Lunsford, T. Oishi, K. Ida, M. Yoshinuma, Y. Takemura, T. Kinoshita, G. Motojima, N. Kenmochi, G. Kawamura, C. Suzuki, A. Nagy, A. Bortolon, N. A. Pablant, A. Mollen, N. Tamura, D. A. Gates, T. Morisaki in Nature Physics

Scientists have found that adding a common household cleaning agent — the mineral boron contained in such cleaners as Borax — can vastly improve the ability of some fusion energy devices to contain the heat required to produce fusion reactions on Earth the way the sun and stars do.

Physicists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) working with Japanese researchers, made the observation on the Large Helical Device (LHD) in Japan, a twisty magnetic facility that the Japanese call a “heliotron.” The results demonstrated for the first time a novel regime for confining heat in facilities known as stellarators, similar to the heliotron. The findings could advance the twisty design as a blueprint for future fusion power plants.

**Real-time wall conditioning and profile modification.**

Researchers produced the higher confinement regime by injecting tiny grains of boron powder into the LHD plasma that fuels fusion reactions. The injection through a PPPL-installed dropper sharply reduced turbulent swirls and eddies and raised the confined heat that produces the reactions.

“We could see this effect very clearly,” said PPPL physicist Federico Nespoli, lead author of a paper. “The more power we put into the plasma the bigger the increase in heat and confinement, which would be ideal in real reactor conditions.”
Said David Gates, a principal research physicist at PPPL who heads the Advanced Projects Department that oversaw the work: “I am very excited about these excellent results that Federico has written up in this important paper about our collaborations with the team on the Large Helical Device. When we launched this project — the LHD Impurity Powder Dropper — in 2018 we had hopes that there might be an effect on energy confinement. The observations are even better than we expected with turbulence suppression across a large fraction of the plasma radius. I am very grateful to our Japanese colleagues for giving us the opportunity for our team to participate in these experiments.”

The findings also delighted Japanese researchers. “We are very pleased and excited to get these results,” said Masaki Osakabe, executive director of the LHD project and science adviser for nuclear fusion research for MEXT, the Japanese ministry responsible for nuclear power. “We are also honored to be collaborators with PPPL,” Osakabe said. “The findings revealed with this collaboration will provide a nice tool to control the high-performance plasma in a fusion reactor.”

Stellarators, first constructed in the 1950s under PPPL founder Lyman Spitzer, are a promising concept that have long trailed symmetrical magnetic facilities called tokamaks as the leading device for producing fusion energy. A history of relatively poor heat confinement has played a role in holding back stellarators, which can operate in a steady state with little risk of the plasma disruptions that tokamaks face.

Fusion combines light elements in the form of plasma — the hot, charged state of matter composed of free electrons and atomic nuclei, or ions, that makes up 99 percent of the visible universe — to release massive amounts of energy. Tokamaks and stellarators are the principal magnetic designs for scientists seeking to harvest safe, clean and virtually limitless fusion power to generate fusion energy for humanity.

**Emergence of higher-frequency modes.**

Although boron has long been used to condition walls and improve confinement in tokamaks, scientists have not previously seen, “a widespread turbulence reduction and temperature increase like the one reported in this article,” according to the paper. Moreover, absent from the observations were damaging bursts of heat and particles, called edge localized modes (ELMs), that can occur in tokamaks and stellarators during high-confinement, or H-mode, fusion experiments.

The remarkable heat and confinement improvement in LHD plasma may have resulted from the reduction of what is called the ion temperature gradient (ITG) instability, the paper said, which produces turbulence that causes plasma to leak from confinement. The reduction of turbulence contrasts with a type of heat loss called “neoclassical transport,” the other main cause of particles escaping from stellarator confinement.

A new round of LHD experiments is now underway that will test whether the improvement in heat and confinement continues for an increased range of mass injection rates, plasma density, and heating power. Nespoli and colleagues would also like to see if carbon powder can work as well as boron. “Boron creates coating on the wall that is good for confinement and carbon will not do that,” he said. “We want to see if all powder is good or if it’s boron that makes conditions better.”

Additional goals include assessing the ability of boron to improve plasma performance during steady-state LHD operation, which is capable of extremely long plasma discharges of up to one hour. Such experiments could produce fresh evidence of the value of the stellarator design going forward.

Predators mitigate the destabilising effects of heatwaves on multitrophic stream communities

by Samuel R. P.‐J. Ross, Jorge García Molinos, Atsushi Okuda, Jackson Johnstone, Keisuke Atsumi, Ryo Futamura, Maureen A. Williams, Yuichi Matsuoka, Jiro Uchida, Shoji Kumikawa, Hiroshi Sugiyama, Osamu Kishida, Ian Donohue in Global Change Biology

Predator species may buffer the negative impacts of climate change by mitigating against the loss of biodiversity, according to new research led by scientists in Trinity College Dublin and Hokkaido University.

The team of scientists behind the discovery say their findings underline the importance of conserving biodiversity, and top predators in particular, and highlight the potential for species extinctions to worsen the effects of climate change on ecosystems. The scientists assembled communities of freshwater organisms in experimental streams at the Tomakomai Experimental Forest in Northern Japan. The stream communities were exposed to realistic heatwaves, and some included a dominant predator (a sculpin fish), while others did not.

Water temperatures during heatwaves in our experimental mesocosms.

They found that heatwaves destabilised algal (plant) communities in the streams such that the differences normally found among them disappeared and they resembled each other much more closely — equating to a loss of biodiversity — but this only happened when the predator was absent from the community.

Algal communities are important in streams because they form the energy base for all other organisms, so loss of algal biodiversity can propagate to impact the entire ecosystem. Additionally, the scientists discovered that important heatwave effects — such as shifts in total algal biomass — only emerged after the heatwave had passed, underlining that even catastrophic impacts may not be immediately obvious.

Dr Samuel Ross, who led the experiment in Japan as part of his PhD research in Trinity College Dublin’s Department of Zoology, said:

“We found that predator extinctions can interact with heatwaves to further undermine the stability of ecosystems. This highlights how the climate and biodiversity crises are completely intertwined, really just two sides of the same coin.” “Taken together, our results show how the ecological consequences of heatwaves can amplify over time as their impacts propagate through ecological communities. However, predator species help to buffer such impacts, acting as allies in the fight against climate change.”

Predator extinctions increase macroinvertebrate taxon richness.

Dr Jorge García Molinos, Associate Professor in the Arctic Research Center at Hokkaido University, added:

“Amidst the accelerating global extinction crisis, climate change will expose most ecosystems to more frequent, intense and extreme climatic events, such as the heatwaves we examined in our study. Certainly, the disappointing outcome of the recent COP-26 discussions has ensured that this scenario is now unlikely to be avoided. Our work shows how intact ecological communities can play a critical role in mitigating against the effects of climate change, and underscores how conserving biodiversity is key to ensuring a sustainable future for humanity.”

Deconstructing Methanosarcina acetivorans into an acetogenic archaeon

by Christian Schöne, Anja Poehlein, Nico Jehmlich, Norman Adlung, Rolf Daniel, Martin von Bergen, Silvan Scheller, Michael Rother in Proceedings of the National Academy of Sciences

Archaea are small single-celled microorganisms (microbes) that form one of the three domains of cellular life, along with bacteria and eukaryotes. They do not possess a nucleus and therefore belong to the prokaryotes like bacteria. Methanogenic archaea form methane as the end product of their energy metabolism (catabolism), an important intermediate product in the global carbon cycle, which is many times more climate-affecting than carbon dioxide. Methanogens are found primarily in bogland, rice fields, manure, and in the digestive tract of ruminants.

Until now, it was considered scientifically established that methanogens have no alternative means for energy conservation and therefore must produce methane. The reductive acetyl-coenzyme A (acetyl-CoA) pathway, which has several steps in common with methanogenesis and is responsible for the synthesis of cellular components (anabolism) in methanogens, could represent such an alternative. Indeed, it is the only metabolic process that can be involved in both catabolism and anabolism.

Energy metabolism of M. acetivorans relevant for this study.

Prof. Michael Rother, microbiologist at Technische Universität Dresden, and his team, together with colleagues from Göttingen, Leipzig and Helsinki, have now investigated a peculiar phenomenon in the methanogenic archaeon Methanosarcina acetivorans: During growth on carbon monoxide (CO), M. acetivorans forms little methane, and cellular carbon flux is significantly diverted from the methanogenic pathway toward acetyl-CoA. Acetate produced from the acetyl-CoA pathway directly allows synthesis of adenosine triphosphate (ATP) through substrate level phosphorylation.

Rother and his team now wanted to know whether the organism’s metabolism can be completely “forced” into acetogenesis, i.e., whether the methanogenic traitis indeed essential. The team was successful and ended up selecting a mutant that grew without significant methane formation, i.e., that had turned into an acetogen. Genetic, genomic and proteomic analyses of the selected strain revealed that although crucial components of the respiratory chain were now absent, the enzyme that produces its substrate (a heterodisulfide) was still essential for survival.

The terminal respiratory oxidoreductase is not essential in M. acetivorans.

“This apparent contradiction can only be explained by a previously unknown anabolic — and essential role of the heterodisulfide, which we now need to figure out,” says Prof. Rother, adding, “It is quite something to overturn such an old paradigm, namely that all methanogens are obligate methanogenic. In fact, they are probably not nearly as limited in energy metabolism as previously thought. Moreover, the possibility of converting methanogenic metabolism into the seemingly simpler acetogenic metabolism suggests that methanogenesis may have evolved from an ancient version of the acetyl-CoA pathway.”

If the flexibility of energy metabolism observed in M. acetivorans is more widespread than previously thought, it could lead to approaches to reduce human-made methane emissions without having to completely inhibit these important organisms.

Transient Effects Caused by Gas Depletion during Carbon Dioxide Electroreduction

by Álvaro Moreno Soto, Jack R. Lake, Kripa K. Varanasi in Langmuir

If researchers could find a way to chemically convert carbon dioxide into fuels or other products, they might make a major dent in greenhouse gas emissions. But many such processes that have seemed promising in the lab haven’t performed as expected in scaled-up formats that would be suitable for use with a power plant or other emissions sources.

Now, researchers at MIT have identified, quantified, and modeled a major reason for poor performance in such conversion systems. The culprit turns out to be a local depletion of the carbon dioxide gas right next to the electrodes being used to catalyze the conversion. The problem can be alleviated, the team found, by simply pulsing the current off and on at specific intervals, allowing time for the gas to build back up to the needed levels next to the electrode. The findings, which could spur progress on developing a variety of materials and designs for electrochemical carbon dioxide conversion systems, were published in a paper by MIT postdoc Álvaro Moreno Soto, graduate student Jack Lake, and professor of mechanical engineering Kripa Varanasi.

“Carbon dioxide mitigation is, I think, one of the important challenges of our time,” Varanasi says. While much of the research in the area has focused on carbon capture and sequestration, in which the gas is pumped into some kind of deep underground reservoir or converted to an inert solid such as limestone, another promising avenue has been converting the gas into other carbon compounds such as methane or ethanol, to be used as fuel, or ethylene, which serves as a precursor to useful polymers.

SEM images of the state of the Cu electrode (a) prior to and (b) after the cleaning process, and (c) after experiments. The magnification for the three images is 100 times and the scale bar represents 100 mm.

There are several ways to do such conversions, including electrochemical, thermocatalytic, photothermal, or photochemical processes. “Each of these has problems or challenges,” Varanasi says. The thermal processes require very high temperature, and they don’t produce very high-value chemical products, which is a challenge with the light-activated processes as well, he says. “Efficiency is always at play, always an issue.”

The team has focused on the electrochemical approaches, with a goal of getting “higher-C products” — compounds that contain more carbon atoms and tend to be higher-value fuels because of their energy per weight or volume. In these reactions, the biggest challenge has been curbing competing reactions that can take place at the same time, especially the splitting of water molecules into oxygen and hydrogen.

The reactions take place as a stream of liquid electrolyte with the carbon dioxide dissolved in it passes over a metal catalytic surface that is electrically charged. But as the carbon dioxide gets converted, it leaves behind a region in the electrolyte stream where it has essentially been used up, and so the reaction within this depleted zone turns toward water splitting instead. This unwanted reaction uses up energy and greatly reduces the overall efficiency of the conversion process, the researchers found.

“There’s a number of groups working on this, and a number of catalysts that are out there,” Varanasi says. “In all of these, I think the hydrogen co-evolution becomes a bottleneck.”

One way of counteracting this depletion, they found, can be achieved by a pulsed system — a cycle of simply turning off the voltage, stopping the reaction and giving the carbon dioxide time to spread back into the depleted zone and reach usable levels again, and then resuming the reaction.

Often, the researchers say, groups have found promising catalyst materials but haven’t run their lab tests long enough to observe these depletion effects, and thus have been frustrated in trying to scale up their systems. Furthermore, the concentration of carbon dioxide next to the catalyst dictates the products that are made. Hence, depletion can also change the mix of products that are produced and can make the process unreliable.

“If you want to be able to make a system that works at industrial scale, you need to be able to run things over a long period of time,” Varanasi says, “and you need to not have these kinds of effects that reduce the efficiency or reliability of the process.”

The team studied three different catalyst materials, including copper, and “we really focused on making sure that we understood and can quantify the depletion effects,” Lake says. In the process they were able to develop a simple and reliable way of monitoring the efficiency of the conversion process as it happens, by measuring the changing pH levels, a measure of acidity, in the system’s electrolyte.

SEM images of the surface state of the Au electrode (a) prior to (b) and after the cleaning process, and (c) after experiments.

In their tests, they used more sophisticated analytical tools to characterize reaction products, including gas chromatography for analysis of the gaseous products, and nuclear magnetic resonance characterization for the system’s liquid products. But their analysis showed that the simple pH measurement of the electrolyte next to the electrode during operation could provide a sufficient measure of the efficiency of the reaction as it progressed. This ability to easily monitor the reaction in real-time could ultimately lead to a system optimized by machine-learning methods, controlling the production rate of the desired compounds through continuous feedback, Moreno Soto says. Now that the process is understood and quantified, other approaches to mitigating the carbon dioxide depletion might be developed, the researchers say, and could easily be tested using their methods.

This work shows, Lake says, that “no matter what your catalyst material is” in such an electrocatalytic system, “you’ll be affected by this problem.” And now, by using the model they developed, it’s possible to determine exactly what kind of time window needs to be evaluated to get an accurate sense of the material’s overall efficiency and what kind of system operations could maximize its effectiveness.

Ovalbumin production using Trichoderma reesei culture and low-carbon energy could mitigate the environmental impacts of chicken-egg-derived ovalbumin

by Natasha Järviö, Tuure Parviainen, Netta-Leena Maljanen, Yumi Kobayashi, Lauri Kujanpää, Dilek Ercili-Cura, Christopher P. Landowski, Toni Ryynänen, Emilia Nordlund, Hanna L. Tuomisto in Nature Food

The research by the Future Sustainable Food Systems research group at the University of Helsinki together with VTT Technical Research Centre of Finland shows that fungus-produced ovalbumin could have the potential to mitigate part of the environmental burden associated with chicken egg white powder. This is especially true when using low carbon energy sources in the production.

Chicken egg white powder is a commonly used ingredient in the food industry due to the high-quality protein it contains. The yearly consumption of egg proteins in 2020 was around 1.6 million tons and the market is expected to expand further in the coming years.

The growing demand is raising questions about both sustainability and ethics. Parts of the egg white powder production chain, such as rearing chickens for egg production, generate large amounts of greenhouse gas emissions and contribute to water scarcity, biodiversity loss, and deforestation. Additionally, intensive chicken farming has resulted in outbreaks of zoonotic diseases by serving as an important reservoir for human pathogens.

Egg white protein produced by precision fermentation has excellent foaming properties. (Image: VTT Technical Research Centre of Finland)

Searching for sustainable alternatives to animal-based proteins has been of growing interest within the food industry. Cellular agriculture, also called precision fermentation when used for recombinant ingredient production, offers a biotechnology-based solution to decouple the production of animal proteins from animal farming by using a microbial production system to produce the specific proteins instead.

“For example, more than half of the egg white powder protein content is ovalbumin. VTT has succeeded in producing ovalbumin with the help of the filamentous ascomycete fungus Trichoderma reesei. The gene carrying the blueprints for ovalbumin is inserted by modern biotechnological tools into the fungus which then produces and secretes the same protein that chickens produce. The ovalbumin protein is then separated from the cells, concentrated and dried to create a final functional product,” says Dr Emilia Nordlund from VTT Technical Research Centre of Finland.

Cell-cultured products generally need more electricity than typical agricultural products, and therefore the type of energy source used affects the level of environmental impact. However, the amount of agricultural inputs needed for ovalbumin production by microbes — such as glucose — is generally substantially lower per kilogramme of protein powder.

“According to our research, this means that the fungus-produced ovalbumin reduced land use requirements by almost 90 per cent and greenhouse gases by 31–55 per cent compared to the production of its chicken-based counterpart. In the future, when production is based on low carbon energy, precision fermentation has the potential to reduce the impact even by up to 72 per cent,” says Doctoral Researcher Natasha Järviö from the University of Helsinki.

For the impact of water use on the environment, the results were less conclusive, showing a high degree of dependency on the assumed location of the ovalbumin production site. In general, the study shows the potential of the precision fermentation technology to increase the sustainability of protein production, which can be further increased by the use of low-carbon energy sources.

Bioenergy sorghum’s deep roots: A key to sustainable biomass production on annual cropland

by Austin Lamb, Brock Weers, Brian McKinley, William Rooney, Cristine Morgan, Amy Marshall‐Colon, John Mullet in GCB Bioenergy

The world faces an increasing amount of carbon dioxide in the atmosphere and a shortage of carbon in the soil. However, bioenergy sorghum can provide meaningful relief from both problems, according to a new study by Texas A&M AgriLife Research scientists.

According to the research, bioenergy sorghum hybrids capture and sequester significant amounts of atmospheric carbon dioxide in soil. The crop can improve soil fertility and potentially earn carbon credits to offset greenhouse gas emissions. In addition, the study shows that bioenergy sorghum’s unusually deep root system can reach sources of water and nutrients untapped by other annual crops. These results suggest the crop can help manage fertilizer runoff from other annuals in a crop rotation.

The senior investigator for the work is John Mullet, Ph.D., professor and Perry L. Adkisson Chair in Agricultural Biology in the Department of Biochemistry and Biophysics. A key collaborator is Bill Rooney, Ph.D., professor and Borlaug-Monsanto Chair for Plant Breeding and International Crop Improvement, Department of Soil and Crop Sciences. Both are in the Texas A&M College of Agriculture and Life Sciences, Bryan-College Station.

Accumulation of bioenergy sorghum biomass and nodal root numbers during the 2017 growing season. (a) Accumulation of dry biomass in roots, stems, leaf blades/sheath, and total biomass of TX08001 per plant 32–155 days after plant emergence (DAE) in the field. (b) Nodal root number (solid gray bars) and root dry weight (g) per plant (cross-hatched bars) from 32 to 155 DAE.

Mullet is an expert in bioenergy crops’ genomics, genetics and gene regulatory networks. Rooney spearheaded the development of bioenergy sorghum hybrids over the past 20 years. For the past 15 years, Rooney and Mullet have collaborated to develop bioenergy sorghum. In fact, Mullet and Rooney have been working to improve bioenergy sorghum varieties to produce an ideal annual bioenergy crop. The hybrid used in the recent study creates high yields of biomass for fuel, power and bioproduct generation. The crop also has excellent drought resilience, good nitrogen-use efficiency and a deep root system.

“There is an assumption that the most sustainable bioenergy crops are perennial because they require fewer inputs and can sequester more biomass than annuals,” Rooney said. “Those statements are true, but U.S. agriculture always requires annual cropping varieties and options as well.”

The study shows that an acre planted with a bioenergy sorghum hybrid accumulates about 3.1 tons of dry root biomass over the crop’s 155-day growing season. Bioenergy sorghum roots also grew to over 6.5 feet deep over their growing season. These new metrics make it easier to predict how much atmospheric carbon dioxide might be captured inside roots. The numbers can also shed light on how many carbon credits a planted field might earn.

“Frankly, the numbers are quite favorable,” Rooney said.

The numbers are also important for understanding the crop’s potential to improve soil fertility and water-holding capacity by replenishing soil organic carbon. However, previous research has shown that in the U.S., soil organic carbon levels have fallen by 50% over the past 100 years in land planted with annual crops.

This drop in soil carbon levels could be due to cropping practices, microbial activity and changing land use, Rooney said. These complex factors mean that predicting how long it might take to replenish lost carbon requires sophisticated modeling. The restoration process is likely to take many decades.

“For modeling, they need to have a realistic number to start with,” Rooney said. “We haven’t historically had enough info to do that, but this study provides a benchmark for scientists and policymakers.”

Bioenergy sorghum root anatomy. Roots were collected by probe truck to a soil depth of 120 cm from field-grown plants ~100 days after planting in 2020. (a–c) Bioenergy sorghum nodal root cross-sections showing cortical cells ©, metaxylem (Mx), phloem (Ph), and parenchyma (Pr) cells (scale bars = 50 µm). (b) Formation of aerenchyma (Aer) in cortical cell layers. © Nodal roots showing degradation of cell layers external to the endodermis (En). (d) Representative assortment of lateral roots at the same magnification as nodal roots (scale bar, 250 µm). (e) Lateral root with partial conversion of cortical cells to aerenchyma (scale bar = 50 µm). (f) Lateral roots with a central metaxylem (Mx) and protoxylem (Px) lacking cell layers outside of the endodermis.

In this study, Rooney and his team managed the field trials and helped with phenotyping. Mullet and his team characterized the root system and the genes expressed within. Over multiple years, the study considered in-depth how one bioenergy sorghum hybrid interacts with two soil types, Rooney said. He stresses the need to conduct further research.

“In this study, we didn’t sample the genetic diversity of bioenergy sorghum at all, except for one standard type,” Rooney said. “And looking at multiple environments and expanding the range of we are evaluating is essential.”

Modeling studies estimate that millions of acres of abandoned and marginal cropland in the U.S. are available for planting. Many of those acres are in the Gulf Coast region. The region is ideal for bioenergy sorghum production because of ample rainfall, long growing seasons and low competition with grain crops, Mullet said. Furthermore, the crop has improved over the years in terms of productivity, resilience and composition, thanks to Mullet’s and Rooney’s efforts.

“Recently, I’ve decided the most important thing we can do is continue research on bioenergy sorghum optimization, but also to help design and build biorefineries that will process materials from the crop in a way that’s optimal,” Mullet said.

Carbon captured in biofuels and bioproducts at biorefineries, and by bioenergy sorghum roots could generate carbon credits, potentially benefiting producers and industry. Yet despite the Gulf Coast’s excellent potential for biofuels production, there are no bioenergy research centers and very few biorefineries in the region, Mullet said. Therefore, Mullet is now working to attract industry and government funding to help build the next generation of biorefineries designed to use bioenergy sorghum biomass for the production of biofuels, bioproducts and biopower.

“The project has expanded to not just producing biofuels and bioproducts, but also directly capturing carbon and sequestering it,” he said.

Designing local air pollution policies focusing on mobility and heating to avoid a targeted number of pollution-related deaths: Forward and backward approaches combining air pollution modeling, health impact assessment and cost-benefit analysis

by Hélène Bouscasse, Stephan Gabet, Glen Kerneis, Ariane Provent, Camille Rieux, Nabil Ben Salem, Harry Dupont, Florence Troude, Sandrine Mathy, Rémy Slama in Environment International

Reducing fine particle mortality in a conurbation by two-thirds could be achieved at a cost that is much lower than the value of the societal and economic benefits obtained, according to a study by a multidisciplinary team from CNRS, INSERM, INRAE, Grenoble Alpes University (UGA) and Atmo Auvergne-Rhône-Alpes. The study identifies specific public policies that could achieve health objectives set by local decision makers, as well as their expected co-benefits.

Every year in France, fine particle pollution (particles with a diameter of less than 2.5 micrometres) leads to the premature death of around 40,000 people. The associated cost is estimated at €100 billion per year. Despite this, public policies to combat air pollution are generally implemented without first assessing their future health and economic impacts.

The MobilAir project attempts to address this problem by identifying specific policies that would meet the health objectives set by decision-makers in the Grenoble conurbation, namely, a 67% reduction in the mortality rate associated with fine particles from 2016 to 2030. A cost-benefit analysis of various options was carried out by a collaboration involving the Grenoble Applied Economics Lab (CNRS / INRAE / UGA), the Institute for Advanced Biosciences (INSERM / CNRS / UGA), the Centre for Economics and Sociology applied to Agriculture and Rural Areas (AgroSup Dijon / INRAE) and Atmo Auvergne-Rhône-Alpes.

The team targeted the two local sectors that emit the most fine particles: wood heating and transport. They show that the health objectives can be met by combining two measures: replacing all inefficient wood heaters by modern pellet stoves, and reducing personal motor vehicle traffic within the conurbation by 36%. Specifically, these policies would need to be accompanied by financial assistance to households, the development of infrastructure (public transport and/or cycle paths, etc.) and carefully targeted public awareness programmes.

Overview of the study, showing the reverse approach from an air pollution-related health improvement objective to the identification of the corresponding urban policies as well as the cost-benefice analysis of the designed urban policy scenarios.

Successful implementation of such policies would result in a series of additional health benefits going beyond the health gains directly related to fine particles, since this would promote physical activity, and reduce urban noise pollution and greenhouse gas emissions. Scenarios involving the most widespread development of active modes of transport (walking and cycling) would lead to a net benefit of €8.7 billion over the period 2016–2045, i.e. an annual benefit of €629 per capita in the conurbation.

This is the first study in France to demonstrate that the societal benefits associated with measures to improve air quality would outweigh the cost of such measures. It thus provides decision-makers with scientifically validated approaches to significantly improving health throughout the conurbation.