Cleaning up the aging brain: Scientists restore brain's trash disposal system

Alzheimer's, Parkinson's, and other neurological disorders can be seen as "dirty brain" diseases, where the brain struggles to clear out harmful waste. Aging is a key risk factor because, as we grow older, our brain's ability to remove toxic buildup slows down. However, new research in mice demonstrates that it's possible to reverse age-related effects and restore the brain's waste-clearing process.

"This research shows that restoring cervical lymph vessel function can substantially rescue the slower removal of waste from the brain associated with age," said Douglas Kelley, PhD, a professor of Mechanical Engineering in the University of Rochester Hajim School of Engineering and Applied Sciences. "Moreover, this was accomplished with a drug already being used clinically, offering a potential treatment strategy." Kelley is one of the lead authors of the study, which appears in the journal Nature Aging, along with Maiken Nedergaard, MD, DMSc, co-director the University's Center for Translational Neuromedicine.

First described by Nedergaard and her colleagues in 2012, the glymphatic system is the brain's unique waste removal process that uses cerebrospinal fluid (CSF) to wash away excess proteins generated by energy hungry neurons and other cells in the brain during normal activity. This discovery pointed the way for potential new approaches to treat diseases commonly associated with the accumulation of protein waste in the brain, such Alzheimer's (beta amyloid and tau) and Parkinson's (alpha-synuclein). In healthy and young brains, the glymphatic system does a good job of flushing away these toxic proteins, however, as we age, this system slows, setting the stage for these diseases.

A network of tiny pumps draws waste from the brain

Once laden with protein waste, CSF in the skull needs to make its way to the lymphatic system and ultimately the kidneys, where it is processed along with the body's other waste. The new research combines advanced imaging and particle tracking techniques to describe for the first time in detail the route via the cervical lymph vessels in the neck through which half of dirty CSF exits the brain.

In addition to measuring the flow of CSF, the researchers were able observe and record the pulsing of lymph vessels in the neck that helps draw CSF out of the brain. "Unlike the cardiovascular system which has one big pump, the heart, fluid in the lymphatic system is instead transported by a network of tiny pumps," said Kelley. These microscopic pumps, called lymphangions, have valves to prevent backflow and are strung together, one after another, to form lymph vessels.

The researchers found that as the mice aged, the frequency of contractions decreased, and the valves failed. As a result, the speed of dirty CSF flowing out of the brains of older mice was 63 percent slower compared to younger animals.

Known drug restarts flow of brain cleaning fluids

The team then set out to see if they could revive the lymphangions and identified a drug called prostaglandin F2α, a hormone-like compound commonly used medically to induce labor and known to aid smooth muscle contraction. The lymphangions are lined with smooth muscle cells, and when the researchers applied the drug to the cervical lymph vessels in older mice, the frequency of contractions and the flow of dirty CSF from the brain both increased, returning to a level of efficiency found in younger mice.

"These vessels are conveniently located near the surface of the skin, we know they are important, and we now know how to accelerate function," said Kelley. "One can see how this approach, perhaps combined with other interventions, could be the basis for future therapies for these diseases."

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Waste Styrofoam can now be converted into polymers for electronics

University of Delaware and Argonne National Laboratory have come up with a chemical reaction that can convert Styrofoam into a high-value conducting polymer known as PEDOT:PSS. In a new paper published in JACS Au, the study demonstrates how upgraded plastic waste can be successfully incorporated into functional electronic devices, including silicon-based hybrid solar cells and organic electrochemical transistors.

The research group of corresponding author Laure Kayser, assistant professor in the Department of Materials Science and Engineering in UD's College of Engineering with a joint appointment in the Department of Chemistry and Biochemistry in the College of Arts and Sciences, regularly works with PEDOT:PSS, a polymer that has both electronic and ionic conductivity, and was interested in finding ways to synthesize this material from plastic waste.

After connecting with Argonne chemist David Kaphan during an event hosted by UD's research office, the research teams at UD and Argonne began evaluating the hypothesis that PEDOT:PSS could be made by sulfonating polystyrene, a synthetic plastic found in many types of disposable containers and packing materials.

Sulfonation is a common chemical reaction where a hydrogen atom is replaced by sulfonic acid; the process is used to create a variety of products such as dyes, drugs and ion exchange resins. These reactions can either be "hard" (with higher conversion efficiency but that require caustic reagents) or "soft" (a less efficient method but one that uses milder materials).

In this paper, the researchers wanted to find something in the middle: "A reagent that is efficient enough to get really high degrees of functionalization but that doesn't mess up your polymer chain," Kayser explained.

The researchers first turned to a method described in a previous study for sulfonating small molecules, one that showed promising results in terms of efficiency and yield, using 1,3-Disulfonic acid imidazolium chloride ([Dsim]Cl). But adding functional groups onto a polymer is more challenging than for a small molecule, the researchers explained, because not only are unwanted byproducts harder to separate, any small errors in the polymer chain can change its overall properties.

To address this challenge, the researchers embarked on many months of trial and error to find the optimal conditions that minimized side reactions, said Kelsey Koutsoukos, a materials science doctoral candidate and second author of this paper.

"We screened different organic solvents, different molar ratios of the sulfonating agent, and evaluated different temperatures and times to see which conditions were the best for achieving high degrees of sulfonation," he said.

The researchers were able to find reaction conditions that resulted in high polymer sulfonation, minimal defects and high efficiency, all while using a mild sulfonating agent. And because the researchers were able to use polystyrene, specifically waste Styrofoam, as a starting material, their method also represents an efficient way to convert plastic waste into PEDOT:PSS.

Once the researchers had PEDOT:PSS in hand, they were able to compare how their waste-derived polymer performed compared to commercially available PEDOT:PSS.

"In this paper, we looked at two devices -- an organic electronic transistor and a solar cell," said Chun-Yuan Lo, a chemistry doctoral candidate and the paper's first author. "The performance of both types of conductive polymers was comparable, and shows that our method is a very eco-friendly approach for converting polystyrene waste into high-value electronic materials."

Specific analyses conducted at UD included X-ray photoelectron spectroscopy (XPS) at the surface analysis facility, film thickness analysis at the UD Nanofabrication Facility, and solar cell evaluation at the Institute of Energy Conversion. Argonne's advanced spectroscopy equipment, such as carbon NMR, was used for detailed polymer characterization. Additional support was provided by materials science and engineering professor Robert Opila for solar cell analysis and by David C. Martin, the Karl W. and Renate Böer Chaired Professor of Materials Science and Engineering, for the electronic device performance analyses.

One unexpected finding related to the chemistry, the researchers added, is the ability to use stoichiometric ratios during the reaction.

"Typically, for sulfonation of polystyrene, you have to use an excess of really harsh reagents. Here, being able to use a stoichiometric ratio means that we can minimize the amount of waste being generated," Koutsoukos said.

This finding is something the Kayser group will be looking into further as a way to "fine-tune" the degree of sulfonation. So far, they've found that by varying the ratio of starting materials, they can change the degree of sulfonation on the polymer. Along with studying how this degree of sulfonation impacts the electrical properties of PEDOT:PSS, the team is interested in seeing how this fine-tuning capability can be used for other applications, such as fuel cells or water filtration devices, where the degree of sulfonation greatly impacts a material's properties.

"For the electronic devices community, the key takeaway is that you can make electronic materials from trash, and they perform just as well as what you would purchase commercially," Kayser said. "For the more traditional polymer scientists, the fact that you can very efficiently and precisely control the degree of sulfonation is going to be of interest to a lot of different communities and applications."

The researchers also see great potential for how this research can contribute to ongoing global sustainability efforts by providing a new way to convert waste products into value-added materials.

"Many scientists and researchers are working hard on upcycling and recycling efforts, either by chemical or mechanical means, and our study provides another example of how we can address this challenge," Lo said.

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Sustainable plastics from agricultural waste

In our rapidly industrialized world, the quest for sustainable materials has never been more urgent. Plastics, ubiquitous in daily life, pose significant environmental challenges, primarily due to their fossil fuel origins and problematic disposal.

Now, a study led by Jeremy Luterbacher's team at EPFL unveils a pioneering approach to producing high-performance plastics from renewable resources.

The research, published in Nature Sustainability, introduces a novel method for creating polyamides -- a class of plastics known for their strength and durability, the most famous of which are nylons -- using a sugar core derived from agricultural waste.

The new method leverages a renewable resource, and also achieves this transformation efficiently and with minimal environmental impact.

"Typical, fossil-based plastics need aromatic groups to give rigidity to their plastics -- this gives them performance properties like hardness, strength and high temperature resistance," says Luterbacher.

"Here, we get similar results but use a sugar structure, which is ubiquitous in nature and generally completely non-toxic, to provide rigidity and performance properties."

Lorenz Manker, the study's lead-author, and his colleagues developed a catalyst-free process to convert dimethyl glyoxylate xylose, a stabilized carbohydrate made directly from biomass such as wood or corn cobs, into high-quality polyamides.

The process achieves an impressive atom efficiency of 97%, meaning almost all the starting material is used in the final product, which drastically reduces waste.

The bio-based polyamides exhibit properties that can compete with their fossil counterparts, offering a promising alternative for various applications.

What's more, the materials demonstrated significant resilience through multiple cycles of mechanical recycling, maintaining their integrity and performance, which is a crucial factor for managing the lifecycle of sustainable materials.

The potential applications for these innovative polyamides are vast, ranging from automotive parts to consumer goods, all with a significantly reduced carbon footprint.

The team's techno-economic analysis and life-cycle assessment suggest these materials could be competitively priced against traditional polyamides including nylons (e.g. nylon 66), with a global warming potential reduction of up to 75%.

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Plastic-eating bacteria turn waste into useful starting materials for other products

Mountains of used plastic bottles get thrown away every day, but microbes could potentially tackle this problem. Now, researchers in ACS Central Science report that they've developed a plastic-eating E. coli that can efficiently turn polyethylene terephthalate (PET) waste into adipic acid, which is used to make nylon materials, drugs and fragrances.

Previously, a team of researchers including Stephen Wallace engineered a strain of E. coli to transform the main component in old PET bottles, terephthalic acid, into something tastier and more valuable: the vanilla flavor compound vanillin. At the same time, other researchers engineered microbes to metabolize terephthalic acid into a variety of small molecules, including short acids. So, Wallace and a new team from the University of Edinburgh wanted to expand E. coli's biosynthetic pathways to include the metabolism of terephthalic acid into adipic acid, a feedstock for many everyday products that's typically generated from fossil fuels using energy-intensive processes.

The team developed a new E. coli strain that produced enzymes that could transform terephthalic acid into compounds such as muconic acid and adipic acid. Then, to transform the muconic acid into adipic acid, they used a second type of E. coli, which produced hydrogen gas, and a palladium catalyst. In experiments, the team found that attaching the engineered microbial cells to alginate hydrogel beads improved their efficiency, and up to 79% of the terephthalic acid was converted into adipic acid. Using real-world samples of terephthalic acid from a discarded bottle and a coating taken from waste packaging labels, the engineered E. coli system efficiently produced adipic acid. In the future, the researchers say they will look for pathways to biosynthesize additional higher-value products.

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Scientists convert waste paper into battery parts for smartphones and electric vehicles

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a technique to convert waste paper, from single-use packaging and bags, and cardboard boxes, into a crucial component of lithium-ion batteries.

Through a process called carbonisation which converts paper into pure carbon, the NTU researchers turned the paper's fibres into electrodes, which can be made into rechargeable batteries that power mobile phones, medical equipment, and electric vehicles.

To carbonise the paper, the team exposed the paper to high temperatures, which reduces it to pure carbon, water vapour and oils that can be used for biofuel. As carbonisation takes place in the absence of oxygen, this emits negligible amounts of carbon dioxide, and the process is a greener alternative to disposing of kraft paper through incineration, producing large amounts of greenhouse gasses.

The carbon anodes produced by the research team also demonstrated superior durability, flexibility, and electrochemical properties. Laboratory tests showed that the anodes could be charged and discharged up to 1,200 times, which is at least twice as durable as anodes in current phone batteries. The batteries that use the NTU-made anodes could also withstand more physical stress than their counterparts, absorbing crushing energy up to five times better.

The NTU-developed method also uses less energy-intensive processes and heavy metals compared to current industrial methods of manufacturing battery anodes. As the anode is worth 10 per cent to 15 per cent of the total cost of a lithium-ion battery, this latest method, which uses a low-cost waste material, is expected to also bring down the cost of manufacturing them.

The findings were published in the scientific peer-reviewed journal Additive Manufacturing in October.

Using waste paper as the raw material to produce battery anodes would also ease our reliance on conventional sources for carbon, such as carbonaceous fillers and carbon-yielding binders, which are mined and later processed with harsh chemicals and machinery.

Paper waste, which comprises disposed paper bags cardboard, newspaper, and other paper packaging, accounted for nearly a fifth of the waste generated in Singapore in 2020.

Kraft paper bags, which make up the bulk of Singapore's paper waste, were also found to have large environmental footprints compared to their counterparts made of cotton and plastic, due to their greater contribution to global warming when incinerated and the eco-toxicity potential in producing them, a separate 2020 NTU study found.

The current innovation which presents an opportunity to upcycle waste products and reduce our dependence on fossil fuels, accelerating our transition towards a circular economy, green materials, and clean energy, reflects NTU's commitment to mitigate our impact on the environment, which is one of four humanity's grand challenges that the University seeks to address through its NTU 2025 strategic plan.

Assistant Professor Lai Changquan, from NTU's School of Mechanical & Aerospace Engineering, who led the project, said: "Paper is used in many facets in our daily lives, from gift wrapping and arts and crafts, to a myriad of industrial uses, such as heavy-duty packaging, protective wrapping, and the filling of voids in construction. However, little is done to manage it when it is disposed of, besides incineration, which generates high levels of carbon emissions due to their composition. Our method to give kraft paper another lease of life, funnelling it into the growing need for devices such as electric vehicles and smartphones, would not only help cut down on carbon emissions but would also ease the reliance on mining and heavy industrial methods."

The research team has filed for a patent with NTUitive, NTU's innovation and enterprise company. They are also working towards commercialising their invention.

The recipe for greener battery parts

To produce the carbon anodes, the NTU researchers joined and laser cut several thin sheets of kraft paper to form different lattice geometries, some resembling a spikey piñata. The paper was then heated to 1200°C in a furnace without the presence of oxygen, to convert it into carbon, forming the anodes.

The NTU team attributes the anode's superior durability, flexibility, and electrochemical properties to the arrangement of the paper fibres. They said the combination of strength and mechanical toughness shown by the NTU-made anodes would allow batteries of phones, laptops and automobiles to better withstand shocks from falls and crashes.

Current lithium battery technology relies on internal carbon electrodes that gradually crack and crumble after physical shocks from being dropped, which is one of the main reasons why battery life gets shorter with time.

The researchers say that their anodes, which are hardier than current electrodes used in batteries, would help address this problem and extend the life of batteries in a wide array of uses, from electronics to electric vehicles.

Co-author of the study Mr Lim Guo Yao, a research engineer from NTU's School of Mechanical & Aerospace Engineering, said: "Our anodes displayed a combination of strengths, such as durability, shock absorption, electrical conductivity, which are not found in current materials. These structural and functional properties demonstrate that our kraft paper-based anodes are a sustainable and scalable alternative to current carbon materials, and would find economic value in demanding, high-end, multifunctional applications, such as the nascent field of structural batteries."

Asst Prof Lai added: "Our method converts a common and ubiquitous material -- paper -- into another that is extremely durable and in high demand. We hope that our anodes will serve the world's quickly growing need for a sustainable and greener material for batteries, whose manufacturing and improper waste management have shown to have a negative impact on our environment."

Highlighting the significance of the work done by the NTU research team, Professor Juan Hinestroza from the Department of Human Centered Design of Cornell University, US, who was not involved in the research, said: "As kraft paper is produced in very large quantities and disposed likewise all over the world, I believe that the creative approach pioneered by the researchers at NTU Singapore has a great potential for impact at a global scale. Any discovery that will allow the use of waste as a raw material for high-value products like electrodes and foams is indeed a great contribution. I think that this work may open a new avenue and motivate other researchers to find pathways for the transformation of other cellulose-based substrates, such as textiles and packaging materials, which are being discarded in large quantities all over the globe."

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Scientists crack upcycling plastics to reduce greenhouse gas emissions

Scientists from the University of Illinois Urbana-Champaign, University of California, Santa Barbara, and Dow have developed a breakthrough process to transform the most widely produced plastic -- polyethylene (PE) -- into the second-most widely produced plastic, polypropylene (PP), which could reduce greenhouse gas emissions (GHG).

"The world needs more and better options for extracting the energy and molecular value from its waste plastics," said co-lead author Susannah Scott, Distinguished Professor and Mellichamp Chair of Sustainable Catalytic Processing at UC Santa Barbara. Conventional plastic recycling methods result in low-value plastic molecules and, thus, offer little incentive to recycle the mountains of plastic waste that have accumulated over the past several decades. But, Scott added, "turning polyethylene into propylene, which can then be used to make a new polymer, is how we start to build a circular economy for plastics."

"We started by conceptualizing this approach and demonstrated its promise first through theoretical modeling -- now we have proved that it can be done experimentally in a way that is scalable and potentially applicable to current industry demands," said co-lead author Damien Guironnet, a professor of chemical and biomolecular engineering at Illinois, who published the first study outlining the necessary catalytic reactions in 2020.

The new study published in the Journal of the American Chemical Society announces a series of coupled catalytic reactions that transform PE, which is #2 and #4 plastic that make up 29% of the world's plastic consumption, into the building block propylene that is the key ingredient to produce PP, also known as #5 plastic that accounts for close to 25% of the world's plastic consumption.

This study establishes a proof-of-concept for upcycling PE plastic with more than 95% selectivity into propylene. The researchers have built a reactor that creates a continuous flow of propylene that can be converted into PP easily using current technology -- making this discovery scalable and rapidly implementable.

"Our preliminary analysis suggests that if just 20% of the world's PE could be recovered and converted via this route, it could represent a potential savings of GHG emissions comparable to taking 3 million cars off the road," said Garrett Strong, a graduate student associated with the project.

The goal is to cut each very long PE molecule many times to obtain many small pieces, which are the propylene molecules. First, a catalyst removes hydrogen from the PE, creating a reactive location on the chain. Next, the chain is split in two at this location using a second catalyst, which caps the ends using ethylene. Finally, a third catalyst moves the reactive site along the PE chain so the process can be repeated. Eventually, all that is left are a large number of propylene molecules.

"Think of cutting a baguette in half, and then cutting precisely-sized pieces off the end of each half -- where the speed at which you cut controls the size of each slice," Guironnet said.

"Now that we have established the proof of concept, we can start to improve the efficiency of the process by designing catalysts that are faster and more productive, making it possible to scale up," Scott said. "Since our end-product is already compatible with current industry separation processes, better catalysts will make it possible to implement this breakthrough rapidly."

The work presented in this publication is highly complementary to a paper published in Science last week. Both groups used virgin plastics and similar chemistries. However, the Science team used a different process in an enclosed batch reactor, requiring much higher pressure -- which is energy intensive -- and the need to recycle more ethylene.

"If we are to upcycle a significant fraction of the over 100 million tons of plastic waste we generate each year, we need solutions that are highly scalable," Guironnet said. "Our team demonstrated the chemistry in a flow reactor we developed to produce propylene highly selectively and continuously. This is a key advance to address the immense volume of the problem that we are facing."

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Sponges 'sneeze' to dispose of waste

Sneezing out mucus may be one of the oldest ways for organisms to get rid of unwanted waste. A group of researchers found that sponges, one of the oldest multicellular organisms in existence, "sneeze" to unclog their internal filter systems that they use to capture nutrients from the water. Additionally, authors find that other animals who live with the sponges use their mucus as food. Their findings are publishing August 10 in the journal Current Biology.

"Our data suggest that sneezing is an adaptation that sponges evolved to keep themselves clean," says Jasper de Goeij, a marine biologist at the University of Amsterdam and the senior author of the paper.

While the field has known about this behavior for years, the authors of this paper show that these sneezes get rid of materials the sponges cannot use. "Let's be clear: sponges don't sneeze like humans do. A sponge sneeze takes about half an hour to complete. But both sponge and human sneezes exist as a waste disposal mechanism," says de Goeij.

Sponges gather food for themselves by filtering out organic matter from the water. They draw in and eject water from different openings, and sometimes the sponges will suck in particles that are too big. "These are sponges; they can't just walk to somewhere else when the water around them gets too dirty for them to handle," says de Goeij. This is when the "sneezing" mechanism comes in handy.

In videos that the authors included in the paper, you can see the water inlets slowly release mucus, and the mucus will accumulate at the surface of the sponge. Occasionally, sponge tissue will contract and push the waste-containing mucus into the surrounding water.

While the mucus may be waste to sponges, the fishes who live around them think otherwise. "We also observed fish and other animals feeding off of the sponge mucus as food," says Niklas Kornder, the first author of the study and a doctoral researcher in de Goeij's research group. "Some organic matter exists in the water surrounding the coral reef, but most of it is not concentrated enough for other animals to eat. Sponges transform this material into eatable mucus," says Kornder.

The paper recorded "sneezing" behavior in two species of sponges, the Caribbean tube sponge Aplysina archeri and another Indo-Pacific species of the genus Chelonaplysilla. "We actually think that most, if not all, sponges sneeze. I've seen mucus accumulate on different sponges while diving and in pictures taken by other scientists for other purposes," says Kornder.

"Our findings highlight opportunities to better understand material cycling in some of the most ancient Metazoans," say the authors in the paper.

There are still many aspects about sponge "sneezes" that remain open questions. "In the videos, you can see that the mucus moves along defined paths on the surface of the sponge before accumulating. I have some hypotheses, but more analysis is needed to find out what is happening," says Kornder.

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Building bricks from waste materials

Firing bricks and making mortar and cement is very costly, but organic chemists at Flinders University are working on more sustainable alternatives -- focusing on building materials made from waste products.

In another move into the circular economy, researchers from the Flinders Chalker Lab have used low-cost feedstocks to make lightweight but durable polymer building blocks which can be bonded together with an adhesive-free chemical reaction.

Their latest study tested the strength of these materials and explored ways they can be reinforced in construction.

Matthew Flinders Professor of Chemistry, Justin Chalker, says the need to develop sustainable building materials is increasingly important, with cement, iron and steel production accounting for more than 15% of global CO2 emissions each year.

"In this study, we tested a new type of brick we can make from waste cooking oil, mixed with sulfur and dicyclopentadiene (DCPD). Both sulfur and DCPD are byproducts of petroleum refining.

"The bricks bond together without mortar upon application of a trace amount of amine catalyst.

"All the starting materials are plentiful and can be classified as industrial waste.

"This research is part of a larger effort to move towards a sustainable built environment," says project leader Professor Chalker.

The Chalker Lab's new polymer research team at Flinders University's College of Science and Engineering is collaborating with Clean Earth Technologies for further development. scale-up and possible commercialisation.

The latest study, published as a cover feature in a special issue on Sustainability in the journal Macromolecular Chemistry and Physics, expanded the research to test the new bricks' mechanical properties and look at ways to reinforce them in construction, including with carbon fibre fillers.

Chalker Lab research associate Dr Maximilian Mann says as well as repurposing waste materials into value-added construction materials, the polymer bricks' sulfur-sulfur bond means they can be bound together without mortar like traditional building method.

"The bonding in this novel catalytic process is very strong, producing a sustainable construction material with its own mortar which will potentially streamline construction," Dr Mann says.

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Methane from waste should not be wasted: Exploring landfill ecosystems

Each year, humans across the globe produce billions of tons of solid waste. Roughly 70% of this refuse ends up deposited in landfills, where it slowly decays. Yet, what may seem an inert accumulation of useless debris, is in reality, a complex ecosystem, teeming with microbial activity. Vast communities of microorganisms feed on the waste, converting it into byproducts -- primarily carbon dioxide (CO2) and methane.

While most landfill methane is captured and flared away, researchers hope instead to make use of this resource, which can be converted into fuels, electricity or used for heating homes (see below).

In a new study published in the journal Applied and Environmental Microbiology, lead author Mark Reynolds, along with his Arizona State University and Industrial colleagues, explore these microbial communities flourishing in leachate, a liquid percolating through solid waste in a landfill. They find that the composition and behavior of specific microbes found in arid landfills, like those in Arizona, are distinct from similar communities in more subtropical or temperate climates. Microbial composition also differs depending on the age of the landfill deposits.

The project was carried out at the Salt River Landfill located in Scottsdale, near ASU's Tempe campus. The facility receives about 1,600 tons of municipal solid waste daily.

Solid waste: a breakdown

The study explores ecosystem-level microbial composition in leachate. Diverse environmental conditions seemingly affect the microbial niches that are compartmentalized across the landfill's 143 acres.

"I think of a landfill as like a big carbon buffet to these microorganisms," says Reynolds, a researcher in the Biodesign Swette Center for Environmental Biotechnology. "Our trash is mostly paper-heavy and it's really rich in cellulose and hemicellulose. These are readily degradable under anaerobic (oxygen-free) conditions."

The capture and use of gases produced in landfills can help reduce hazards associated with landfill emissions, and prevent methane from escaping into the atmosphere. Further, energy projects associated with the capture and processing of landfill gas can generate revenue and create jobs in the community.

By better understanding the behavior of these methane-producing microorganisms, researchers hope to improve the capture of this vital resource and possibly limit the escape of methane and CO2 -- two potent greenhouse gases and leading contributors to climate change -- into the atmosphere.

"We're diving into ecological theory to try to get to the source of what might be driving the organizational patterns of the methane-producing organisms," Reynolds says. The study's multifaceted analysis indicates that temperature and dissolved solids are the two key parameters governing their abundance and diversification. This is good news, because this data is routinely captured at landfill sites commonly on a monthly basis and can provide accurate diagnostics -- telltale indicators of broad trends in overall methane production.

From garbage to fuel

Municipal solid waste landfills accounted for over 15% of methane emissions in 2019, representing the third largest source of global methane emissions. As the study notes, emissions of methane from landfills amount to the equivalent of a billion tons of CO2, or roughly the greenhouse emissions produced by nearly 22 million cars driven for a year.

Typically, most of the methane released by microorganisms in a landfill is captured as biogas and subsequently flared off, converting it to CO2. Although this method limits the climate-damaging effects of the methane itself, it is a short-term and inadequate solution to the problem of greenhouse gas emission from landfills.

In addition to its adverse effect on the climate, the lost methane represents a missed opportunity to capture this valuable resource. The study estimates that approximately one-fifth of the nation's landfills would be suitable for such capture and processing, if economic and other hurdles can be overcome.

Currently, microorganisms degrading municipal solid waste generate landfill gas consisting of roughly 50% methane and 50% CO2. By understanding the subtle workings of these microorganisms -- particularly, methanogenic Archaea, which are the real workhorses in the methane production cycle -- researchers hope to boost methane output.

The increased methane can be harvested and used to create electricity, carbon neutral fuels or to heat homes. The latter option is particularly attractive as no further processing of the methane would be required. Alternately, modifying microbial communities could potentially be used to limit methane output, where mitigation is desired.

On the hunt for archaea

Landfills provide an ideal setting for the detailed study of Archaea, which are notoriously challenging to culture in the laboratory. Roughly 80% of archaea diversity remains largely unexplored. "Our labs are really interested in the methanogens because the same metabolism they enact in the wetlands, which make them the highest source of methane, or instead the human gastrointestinal tract, they enact in the landfills," Reynolds says.

Because the methanogens are primitive, single-celled organisms, they can equally make use of plant, or food matter, or paper products. While the study found similar methane concentrations at their arid landfill site compared to other landfills, different communities of methanogens are doing the heavy lifting. The study demonstrates that microbial behavior is also dependent on the age of the solid waste deposited. Younger waste is higher in temperature compared with older waste and degrades according to different regimes. The aridity has also been shown to greatly affect solid waste breakdown over time.

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The waste product which could help mitigate climate change

A product made from urban, agriculture and forestry waste has the added benefit of reducing the carbon footprint of modern farming, an international review involving UNSW has found.

Visiting Professor in the School of Materials Science and Engineering at UNSW Science, Stephen Joseph, says the study published in GCB Bioenergy provides strong evidence that biochar can contribute to climate change mitigation.

"Biochar can draw down carbon from the atmosphere into the soil and store it for hundreds to thousands of years," the lead author says."This study also found that biochar helps build organic carbon in soil by up to 20 per cent (average 3.8 per cent) and can reduce nitrous oxide emissions from soil by 12 to 50 per cent, which increases the climate change mitigation benefits of biochar."

The findings are supported by the Intergovernmental Panel on Climate Change's recent Special Report on Climate Change and Land, which estimated there was important climate change mitigation potential available through biochar. "The intergovernmental panel found that globally, biochar could mitigate between 300 million to 660 million tonnes of carbon dioxide per year by 2050," Prof. Joseph says. "Compare that to Australia's emissions last year -- an estimated 499 million tonnes of carbon dioxide -- and you can see that biochar can absorb a lot of emissions. We just need a will to develop and use it."

Biochar is the product of heating biomass residues such as wood chips, animal manures, sludges, compost and green waste, in an oxygen-starved environment -- a process called pyrolysis. The result is stable charcoal which can cut greenhouse emissions, while boosting soil fertility. The GCB Bioenergystudy reviewed approximately 300 papers including 33 meta-analyses that examined many of the 14,000 biochar studies that have been published over the last 20 years.

"It found average crop yields increased from 10 to 42 per cent, concentrations of heavy metals in plant tissue were reduced by 17 to 39 per cent and phosphorus availability to plants increased too," Prof. Joseph says. "Biochar helps plants resist environmental stresses, such as diseases, and helps plants tolerate toxic metals, water stress and organic compounds such as the herbicide atrazine." The study details for the first time how biochar improves the root zone of a plant. In the first three weeks, as biochar reacts with the soil it can stimulate seed germination and seedling growth. During the next six months, reactive surfaces are created on biochar particles, improving nutrient supply to plants. After three to six months, biochar starts to 'age' in the soil and forms microaggregates that protect organic matter from decomposition.

Prof. Joseph says the study found the greatest responses to biochar were in acidic and sandy soils where biochar had been applied together with fertiliser. "We found the positive effects of biochar were dose dependent and also dependent on matching the properties of the biochar to soil constraints and plant nutrient requirements," Prof. Joseph says. "Plants, particularly in low-nutrient, acidic soils common in the tropics and humid subtropics, such as the north coast of NSW and Queensland, could significantly benefit from biochar. "Sandy soils in Western Australia, Victoria and South Australia, particularly in dryland regions increasingly affected by drought under climate change, would also greatly benefit."

Prof. Joseph AM is an expert in producing engineered stable biochar from agriculture, urban and forestry residues. He has been researching the benefits of biochar in promoting healthy soils and addressing climate change since he was introduced to it by Indigenous Australians in the seventies. He says biochar has been used for production of crops and for maintaining healthy soils by Indigenous peoples in Australia, Latin America (especially in the Amazon basin) and Africa for many hundreds of years.

Biochar has also been recorded in the 17th Century as a feed supplement for animals. But while Australian researchers have studied biochar since 2005, it has been relatively slow to take off as a commercial product, with Australia producing around 5000 tonnes a year. "This is in part due to the small number of large-scale demonstration programs that have been funded, as well as farmers' and government advisors' lack of knowledge about biochar, regulatory hurdles, and lack of venture capital and young entrepreneurs to fund and build biochar businesses," Prof. Joseph says.

In comparison, the US is producing about 50,000 tonnes a year, while China is producing more than 500,000 tonnes a year. Prof. Joseph, who has received an Order of Australia for his work in renewable energy and biochar, says to enable widespread adoption of biochar, it needs to be readily integrated with farming operations and be demonstrated to be economically viable. "We've done the science, what we don't have is enough resources to educate and train people, to establish demonstrations so farmers can see the benefits of using biochar, to develop this new industry," he says.

However this is slowly changing as large corporations are purchasing carbon dioxide reduction certificates (CORC's) to offset their emissions, which is boosting the profile of biochar in Australia. Biochar has potential in a range of applications. Prof. Joseph co-authored a recent study in International Materials Reviews which detailed the less well-known uses of biochar, such as a construction material, to reduce toxins in soil, grow microorganisms, in animal feed and soil remediation. UNSW has a collaborative grant with a company and a university in Norway to develop a biochar based anti-microbial coating to kill pathogens in water and find use in air filtration systems, he says.

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Plastic-eating enzyme 'cocktail' heralds new hope for plastic waste

 

Plastic bottles and other waste

The scientists who re-engineered the plastic-eating enzyme PETase have now created an enzyme 'cocktail' which can digest plastic up to six times faster.

A second enzyme, found in the same rubbish dwelling bacterium that lives on a diet of plastic bottles, has been combined with PETase to speed up the breakdown of plastic.

PETase breaks down polyethylene terephthalate (PET) back into its building blocks, creating an opportunity to recycle plastic infinitely and reduce plastic pollution and the greenhouse gases driving climate change.

PET is the most common thermoplastic, used to make single-use drinks bottles, clothing and carpets and it takes hundreds of years to break down in the environment, but PETase can shorten this time to days.

The initial discovery set up the prospect of a revolution in plastic recycling, creating a potential low-energy solution to tackle plastic waste. The team engineered the natural PETase enzyme in the laboratory to be around 20 percent faster at breaking down PET.

Now, the same trans-Atlantic team have combined PETase and its 'partner', a second enzyme called MHETase, to generate much bigger improvements: simply mixing PETase with MHETase doubled the speed of PET breakdown, and engineering a connection between the two enzymes to create a 'super-enzyme', increased this activity by a further three times.

The study is published in the journal Proceedings of the National Academy of Sciences.

The team was co-led by the scientists who engineered PETase, Professor John McGeehan, Director of the Centre for Enzyme Innovation (CEI) at the University of Portsmouth, and Dr Gregg Beckham, Senior Research Fellow at the National Renewable Energy Laboratory (NREL) in the US.

Professor McGeehan said: "Gregg and I were chatting about how PETase attacks the surface of the plastics and MHETase chops things up further, so it seemed natural to see if we could use them together, mimicking what happens in nature.

"Our first experiments showed that they did indeed work better together, so we decided to try to physically link them, like two Pac-men joined by a piece of string.

"It took a great deal of work on both sides of the Atlantic, but it was worth the effort -- we were delighted to see that our new chimeric enzyme is up to three times faster than the naturally evolved separate enzymes, opening new avenues for further improvements."

The original PETase enzyme discovery heralded the first hope that a solution to the global plastic pollution problem might be within grasp, though PETase alone is not yet fast enough to make the process commercially viable to handle the tons of discarded PET bottles littering the planet.

Combining it with a second enzyme, and finding together they work even faster, means another leap forward has been taken towards finding a solution to plastic waste.

PETase and the new combined MHETase-PETase both work by digesting PET plastic, returning it to its original building blocks. This allows for plastics to be made and reused endlessly, reducing our reliance on fossil resources such as oil and gas.

Professor McGeehan used the Diamond Light Source, in Oxfordshire, a synchrotron that uses intense beams of X-rays 10 billion times brighter than the Sun to act as a microscope powerful enough to see individual atoms. This allowed the team to solve the 3D structure of the MHETase enzyme, giving them the molecular blueprints to begin engineering a faster enzyme system.

The new research combined structural, computational, biochemical and bioinformatics approaches to reveal molecular insights into its structure and how it functions. The study was a huge team effort involving scientists at all levels of their careers.

One of the most junior authors, Rosie Graham, a joint Portsmouth CEI-NREL PhD student said: "My favourite part of research is how the ideas start, whether it's over coffee, on a train commute or when passing in the university corridors it can really be at any moment.

"It's a really great opportunity to learn and grow as part of this UK-USA collaboration and even more so to contribute another piece of the story on using enzymes to tackle some of our most polluting plastics."

Read more at Science Daily