Daniel Salzler No. 1107 EnviroInsight.org Five Items July 23, 2021
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1. Watershed Newsletter Resumes. After five weeks of recovery from spinal surgery, the editor is back at the computer, cranking out Watershed Info No. 1107. As before, announcing activities in the watershed may be sent to the editor and, if received in time, will be published here.
2. Floating Into Summer With More Buoyant, Liquid-Proof Life Jackets, Swimsuits. Source American Chemical Society.
Summertime is here, and that often means long, lazy days at the beach, water skiing and swimming. Life jackets and swimsuits are essential gear for these activities, but if not dried thoroughly, they can develop a gross, musty smell. Now, researchers have developed a one-step method to create a buoyant cotton fabric for these applications that is also oil- and water-repellent.
Waterproof and oil-proof fabrics are in high demand for recreational water activities because of their low drag and self-cleaning properties. And while cotton is a popular fabric, it’s hydrophilic, so most liquids and dirt can easily mess it up. To improve cotton’s impermeability, previous researchers developed superamphiphobic coatings that were extremely water- and oil-repellant. But because they required multiple time-consuming steps to apply, these coatings were impractical for large-scale manufacturing. Others incorporated nanoparticles into their formulas, but there are concerns about these particles sloughing off and potentially harming the environment. Xiao Gong and Xinting Han wanted to develop a simple way to make a coating for cotton fabric so it would have superb liquid-repulsion properties and hold up in many challenging circumstances.
The researchers optimized a one-step process for a liquid-proof coating by mixing dopamine hydrochloride, 3-aminopropyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane with a piece of cotton fabric for 24 hours. The three-part solution developed into a uniform, dark brown coating on the fabric. In tests, the treated cotton was impervious to many common liquids.
The new solution also coated inner cotton fibers, making them liquid proof, too. In other tests, only strong acid and repeated washings reduced the material’s water and oil resistance, respectively. Treated fabric soiled with fine sand was easy to clean with water, whereas water only wetted the control version. Finally, the material stayed afloat with up to 35 times its weight on it because of nanoscale air pockets that formed where the coating attached to the fabric, the researchers explain.
They say their durable cotton fabric has great potential for applications where drag reduction and increased buoyancy are important, including swimsuits and life jackets.
3. Untrained Beer Drinkers Can Taste Different Barley Genotypes. When it comes to craft beer, the flavor doesn’t have to be all in the hops. As a panel of amateur beer tasters at Washington State University recently demonstrated, malted barley, the number one ingredient in beer besides water, can have a range of desirable flavors too.
Researchers recruited a panel of about 100 craft beer drinkers to taste some so-called SMaSH beers — those brewed with a single barley malt and single hop. All the beers contained the same hop variety, called Tahoma, but each had a malt from a different barley genotype, or genetic makeup. Trained tasters can distinguish these easily, but even the untrained panel could taste the difference among five different barley varieties — and definitely favored some more than others.
“We found that the untrained panelists could differentiate among the barley breeding lines in the ,” said Evan Craine, a WSU doctoral student and first author on the study in the Journal of Food Science. “They did a good job of selecting attributes that revealed distinctive profiles for each of the beers.”The panel generally preferred the four barley breeding lines developed at WSU over the control, known as Copeland, a high-quality malting barley widely grown in Washington state. The panelists were able to easily identify the flavor profiles of the beers, such as one with a “fruity and sweet aromatic” flavor and another with a “citrus” profile made with a barley called Palmer, a variety recently released by WSU for commercial use.
While the untrained panel could distinguish flavors from brewed beers, they were not as adept at tasting the differences among “hot steep” samples which are made by combining hot water and ground barley malt before filtering. This creates a sweet liquid — similar to that made by brewers before yeast is added to create alcohol.
The researchers had hoped amateur beer tasters could distinguish flavor differences in the hot steep as it would shorten the testing process for new barley varieties. Corresponding author Kevin Murphy was not ready to give up on the method.
“Hot steep malt still shows a lot of promise,” said Murphy, a WSU associate professor of crop and soil sciences. “The next step would be testing it with a trained panel to see if they can distinguish barley varieties. Ideally, we would just set it out to consumers because hot steep malting is great outreach. It gets people involved. They love tasting and talking about it.”
More variety from malt-forward beers can potentially benefit not only beer lovers but also the environment and brewers’ bottom lines, said Craine.
“In terms of sustainability, hops can be pretty resource intensive, and at least around us in Pullman, we can grow barley that’s just rain fed,” he said. “Hops can also be really expensive. Brewers are already buying the malt, so if we can find ways to increase the flavor contribution from the malt, hopefully, they can rely less on the hops and save money.”
While the hops craze is continuing, the malt-forward beers have the potential to spur the next evolution in craft brewing, said Murphy.
“Just as craft beer flavor has evolved in the last 20 years, we can expect it to continue to change over the next 20, and the new frontier will be adding different barley flavors or barley-hop combinations,” he said. “I don’t know how many people knew about IPAs 20 years ago, and they exploded. Brewers are very innovative, and I am very excited to see where this goes in the future.”
4. How Green Is Your Plastic? Economical synthesis of polyacrylates and polymethacrylates from biobased materials.
Despite the best efforts of industry to work towards sustainability, most plastics (or polymers) are still made using non-renewable fossil fuels. However, researchers have now found an economical method for producing biobased acrylate resins. The study, published in the journal Angewandte Chemie, shows how all the synthesis steps, from initial building blocks right up to polymerization, can be carried out in a single reactor (one pot), minimizing environmental impact.
Most varnishes, adhesives and paints are made from acrylate resins, which are polymers of acrylic acid esters and methacrylic acid esters. The raw materials that form these esters are acrylic or methacrylic acid, and alcohols. The alcohols give the plastics properties, such as softness or hardness, and water absorption or repulsion.
To make these polyacrylates and polymethacrylates more sustainable, Christophe Thomas and his team from the Institut de Recherche de Chimie in Paris, France, used alcohols from biobased or natural sources, rather than fossil sources. These included plant-based lauryl alcohol, menthol, tetrahydrogeraniol (a pheromone-like substance), vanillin, and ethyl lactate.
In addition to sustainability through renewable resources, the team also targeted synthesis in as few steps as possible, in other words a one-pot process. This meant they had to find catalysts that were suitable for several steps of the process, and also to finely tune all the other synthesis conditions, such as solvents, concentrations, and temperatures.
The first step in this kind of synthesis is the activation of acrylic or methacrylic acid. The researchers were able to identify catalysts from simple salts. These substances were also suitable for the next step, reacting the biobased alcohols with acrylic or methacrylic anhydride (a condensed form of the acids) to give the corresponding esters, which are the building blocks of the subsequent polymer.
“This monomer preparation step is highly efficient and allowed us to perform thepolymerization in the same reactor,” says Thomas. Thus, without purifying the intermediate products, the team was ultimately able to produce block copolymers, which are widely used in plastics production, from two or three different individual polymers produced separately.
The team’s biobased plastics had a number of beneficial properties, depending on the monomers making them up. For example, the resin produced with a lactic acid side chain (poly(ELMA)) was hard and brittle, while the one produced with the more flexible tetrahydrogeraniol side chain (poly(THGA)) was pliable at room temperature. The authors emphasize the numerous available possibilities thanks to the wide variety of biobased alcohols at their disposal.
Aside from the versatility of the team’s approach, their one-pot synthesis also helps reduce the environmental footprint. Since work-up solvents account for a large proportion of the E-factor, or environmental impact, of plastics synthesis, one-pot processes without work-up obviously greatly reduce this factor. Their most successful synthesis reduced the E-factor by three quarters, demonstrating the significance of this research.
5. Enzyme-Based Plastics Recycling Is More Energy Efficient, Better For Environment, Researchers Show. Researchers in the BOTTLE Consortium, including from the U.S. Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) and the University of Portsmouth, have identified using enzymes as a more sustainable approach for recycling polyethylene terephthalate (PET), a common plastic in single-use beverage bottles, clothing, and food packaging that are becoming increasingly relevant in addressing the environmental challenge of plastic pollution. An analysis shows enzyme-recycled PET has potential improvement over conventional, fossil-based methods of PET production across a broad spectrum of energy, carbon, and socioeconomic impacts.
The concept, if further developed and implemented at scale, could lead to new opportunities for PET recycling and create a mechanism for recycling textiles and other materials also made from PET that are traditionally not recycled today. PET ranks among the most abundantly produced synthetic polymers in the world, with 82 million metric tons produced annually; roughly 54% of PET is used in the manufacture of textiles for clothing and fibers for carpet.
“From all the plastics that were produced since the 1950s, less than 10% of it has ever been recycled,” said Avantika Singh, a chemical engineer at NREL and first author of a new paper outlining the path toward enzyme-based recycling. “Most waste plastics end up in landfills.”
The paper, “Techno-economic, life-cycle, and socioeconomic impact analysis of enzymatic recycling of poly(ethylene terephthalate),” appears in the journal Joule. Enzyme Innovation in the United Kingdom, who are also members of BOTTLE.
BOTTLE is striving to address the problem of plastic pollution with two innovative approaches, namely to: (1) develop energy-efficient, cost-effective, and scalable recycling and upcycling technologies and (2) design modern plastics to be recyclable by design.
The new research paper addresses the challenge of plastic recyclability. While images of discarded bottles floating in oceans and other waterways provide a visual reminder of the problems posed by plastic waste, the lesser-seen issue remains of what to do with the PET used to manufacture textiles for clothing and fibers for carpet.
The researchers modeled a conceptual recycling facility that would take in a fraction of the 3 million metric tons of PET consumed annually in the United States. The enzymatic recycling process breaks down PET into its two building blocks, terephthalic acid (TPA) and ethylene glycol. Compared to conventional fossil-based production routes, the research team determined the enzymatic recycling process can reduce total supply-chain energy use by 69%-83% and greenhouse gas emissions by 17%-43% per kilogram of TPA. Additionally, an economy-wide comparison of virgin TPA and recycled TPA in the United States shows that the environmental and socioeconomic effects of the two processes are not distributed equally across their supply chain. The proposed recycling process can reduce environmental impacts by up to 95%, while generating up to 45% more socioeconomic benefits, including local jobs at the material recovery facilities.
The study also predicts that enzymatic PET recycling can achieve cost parity with the production of virgin PET, thus highlighting the potential for this enzyme technology to decarbonize PET manufacturing, in addition to enabling the recycling of waste PET-rich feedstocks, such as clothing and carpets.
“That’s one of the biggest opportunities,” Singh said. “If we can capture that space — textiles, game-changer.”
This research is funded by DOE’s Advanced Manufacturing Office and the Bioenergy Technologies Office. The work was done as part of the Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by the Alliance for Sustainable Energy, LLC.
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