Tag Archives: plastic waste

Plastic waste as a valuable soil additive

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There’s some mildly encouraging news about a way to get rid of plastic waste,

Caption: Plastic waste in a creek bed at Fairmount Park in Riverside, Calif. David Danelski/UCR. Credit: Photo by David Danelski/UCR

This January 9, 2023 news item on ScienceDaily describes research into turning plastic waste into useful products,

University of California, Riverside, scientists have moved a step closer to finding a use for the hundreds of millions of tons of plastic waste produced every year that often winds up clogging streams and rivers and polluting our oceans.

In a recent study, Kandis Leslie Abdul-Aziz, a UCR assistant professor of chemical and environmental engineering, and her colleagues detailed a method to convert plastic waste into a highly porous form of charcoal or char that has a whopping surface area of about 400 square meters per gram of mass.

Such charcoal captures carbon and could potentially be added to soil to improve soil water retention and aeration of farmlands. It could also fertilize the soil as it naturally breaks down. Abdul-Aziz, however, cautioned that more work needs to be done to substantiate the utility of such char in agriculture.

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A January 6, 2023 University of California at Riverside (UC Riverside or UCR) news release (also on EurekAlert) by David Danelski, which originated the news item, provides more detail about the work

The plastic-to-char process was developed at UC Riverside’s Marlan and Rosemary Bourns College of Engineering. It involved mixing one of two common types of plastic with corn waste — the leftover stalks, leaves, husks, and cobs — collectively known as corn stover. The mix was then cooked with highly compressed hot water, a process known as hydrothermal carbonization.

The highly porous char was produced using polystyrene, the plastic used for Styrofoam packaging, and polyethylene terephthalate, or PET, the material commonly used to make water and soda bottles, among many other products.

The study followed an earlier successful effort to use corn stover alone to make activated charcoal used to filter pollutants from drinking water. In the earlier study, charcoal made from corn stover alone activated with potassium hydroxide was able to absorb 98% of the pollutant vanillin from test water samples. 

In the follow-up study, Abdul-Aziz and her colleagues wanted to know if activated charcoal made from a combination of corn stover and plastic also could be an effective water treatment medium. If so, plastic waste could be repurposed to clean up water pollution. But the activated charcoal made from the mix absorbed only about 45% of vanillin in test water samples – making it ineffective for water cleanups, she said.  

“We theorize that there could be still some residual plastic on the surface of the materials, which is preventing the absorption of some of these (vanillin) molecules on the surface,” she said.

Still, the ability to make highly porous charcoal by combining plastic and plant biomass waste is an important discovery, as detailed in the paper, “Synergistic and Antagonistic Effects of the Co-Pyrolysis of Plastics and Corn Stover to Produce Char and Activated Carbon,” published in the journal ACS Omega. The lead author is Mark Gale, a former UCR doctoral student who is now a lecturer at Harvey Mudd College. UCR undergraduate student Peter Nguyen is a co-author and Abdul-Aziz is the corresponding author.  

“It could be a very useful biochar because it is a very high surface area material,” Abdul-Aziz said. “So, if we just stop at the char and not make it in that turn into activated carbon, I think there are a lot of useful ways that we can utilize it.” 

Plastic is essentially a solid form of petroleum that accumulates in the environment, where it pollutes, entangles, and chokes and kills fish, birds, and other animals that inadvertently ingest it. Plastics also break down into micro particles that can get into our bodies and damage cells or induce inflammatory and immune reactions.

Unfortunately, it costs more to recycle used plastic than it costs to make new plastic from petroleum. 

Abdul-Aziz’s laboratory takes a different approach to recycling. It is devoted to putting pernicious waste products such as plastic and plant biomass waste back into the economy by upcycling them into valuable commodities.

“I feel like we have more of an agnostic approach to plastic recycling when you can throw it in (with biomass) and use the char to better the soil,” she said.  “That’s what we’re thinking.”

Here’s a link to and a citation for the paper,

Synergistic and Antagonistic Effects of the Co-Pyrolysis of Plastics and Corn Stover to Produce Char and Activated Carbon by Mark Gale, Peter M. Nguyen, and Kandis Leslie Gilliard-AbdulAziz. ACS Omega 2023, 8, 1, 380–390 Publication Date:December 21, 2022 DOI: https://doi.org/10.1021/acsomega.2c04815 Copyright © 2022 The Authors. Published by American Chemical Society

This paper appears to be open access.

Nanoplastic particles are attracted to each other

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Plastic waste is of rising concern as researchers report finding it in the Arctic (April 5 2022 ScienceDaily news item), as well as, in human blood (March 25, 2022 article by Margaret Osborne for the Smithsonian Magazine).

This post is highlighting research into how a particular form of plastic degrades in the environment, from an April 27, 2022 news item on ScienceDaily,

Polyethylene, a plastic that is both cheap and easy to process, accounts for nearly one-third of the world’s plastic waste. An interdisciplinary team from the University of Bayreuth has investigated the progressive degradation of polyethylene in the environment for the first time. Although the degradation process leads to fragmentation into ever smaller particles, isolated nanoplastic particles are rarely found in the environment. The reason is that such decay products do not like to remain on their own, but rather attach rapidly to larger colloidal systems that occur naturally in the environment. The researchers have now presented their findings in the journal Science of the Total Environment.

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An April 25, 2022 Universität Bayreuth press release (also on EurekAlert but published on April 27, 2022), which originated the news item, gives more detail about the research,

Polyethylene is a plastic that occurs in various molecular structures. Low-density polyethylene (LDPE) is widely used for packaging everyday consumer goods, such as food, and is one of the most common polymers worldwide as a result of increasing demand. Until now, there have only been estimates as to how this widely used plastic degrades after it enters the environment as waste. A research team from the Collaborative Research Centre “Microplastics” at the University of Bayreuth has now systematically investigated this question for the first time. The scientists developed a novel, technically sophisticated experimental set-up for this purpose. This makes it possible to simulate two well-known and environmentally linked processes of plastic degradation independently in the laboratory: 1.) photo-oxidation, in which the long polyethylene chains gradually break down into smaller, more water-soluble molecules when exposed to light, and 2.) increasing fragmentation due to mechanical stress. On this basis, it was possible to gain detailed insights into the complex physical and chemical processes of LDPE degradation.

The final stage of LDPE degradation is of particular interest for studies addressing the potential impact of polyethylene on the environment. What the researchers discovered was that this degradation does not end with the decomposition of the packaging material released into the environment into many micro- and nanoplastic particles, which have a high degree of crystallinity. The reason is that these tiny particles have a strong tendency to aggregate: they attach rapidly to larger colloidal systems consisting of organic or inorganic molecules and are part of the material cycle in the environment. Examples of such colloidal systems include clay minerals, humic acids, polysaccharides, and biological particles from bacteria and fungi. “This process of aggregation prevents individual nanoparticles created by polyethylene degradation from being freely available in the environment and interacting with animals and plants. However, this is not an ‘all clear’ signal. Larger aggregates that participate in the material cycle in the environment and contain nanoplastics do often get ingested by living organisms. That is how nanoplastics can eventually enter the food chain,” says Teresa Menzel, one of the three lead authors of the new study and a doctoral researcher in the field of polymer materials.

To identify the degradation products formed when polyethylene decomposes, the researchers employed a method that has not been widely used in microplastics research: multi-cross-polarization in solid-state NMR spectroscopy. “This method even allows us to quantify the degradation products yielded by photooxidation,” says co-author Anika Mauel, a doctoral researcher in inorganic chemistry.

Bayreuth’s researchers have also discovered that the degradation and decomposition of polyethylene also leads to the formation of peroxides. “Peroxides have long been suspected of being cytotoxic, meaning they have a toxic effect on living cells. That is another way in which LDPE degradation poses a potential threat to natural ecosystems. These interrelationships need to be studied in more detail in the future,” adds co-author Nora Meides, a doctoral researcher in macromolecular chemistry.

The detailed analysis of the chemical and physical processes involved in the degradation of polyethylene would not have been possible without the interdisciplinary networking and coordinated use of state-of-the-art research technologies on the University of Bayreuth’s campus. In particular, these include scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), NMR spectroscopy, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC).

Here’s a link to and a citation for the paper,

Degradation of low-density polyethylene to nanoplastic particles by accelerated weathering by Teresa Menzel Nora Meides, Anika Mauel, Ulrich Mansfeld, Winfried Kretschmer, Meike Kuhn, Eva M.Herzig, Volker Altstädt, Peter Strohrieg, Jürgen Senker, Holger Ruckdäsche. Science of The Total Environment Volume 826, 20 June 2022, 154035 DOI: https://doi.org/10.1016/j.scitotenv.2022.154035

This paper is behind a paywall.

Plastic nanoparticles and brain damage in fish

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Researchers in Sweden suggest plastic nanoparticles may cause brain damage in fish according to a Sept. 25, 2017 news item on phys.org,

Calculations have shown that 10 per cent of all plastic produced around the world ultimately ends up in the oceans. As a result, a large majority of global marine debris is in fact plastic waste. Human production of plastics is a well-known environmental concern, but few studies have studied the effects of tiny plastic particles, known as nanoplastic particles.

“Our study is the first to show that nanosized plastic particles can accumulate in fish brains”, says Tommy Cedervall, a chemistry researcher at Lund University.

A Sept. 25, 2017 Lund University press release, which originated the news item, provides more detail about the research,

The Lund University researchers studied how nanoplastics may be transported through different organisms in the aquatic ecosystem, i.e. via algae and animal plankton to larger fish. Tiny plastic particles in the water are eaten by animal plankton, which in turn are eaten by fish.

According to Cedervall, the study includes several interesting results on how plastic of different sizes affects aquatic organisms. Most importantly, it provides evidence that nanoplastic particles can indeed cross the blood-brain barrier in fish and thus accumulate inside fish’s brain tissue.

In addition, the researchers involved in the present study have demonstrated the occurrence of behavioural disorders in fish that are affected by nanoplastics. They eat slower and explore their surroundings less. The researchers believe that these behavioural changes may be linked to brain damage caused by the presence of nanoplastics in the brain.

Another result of the study is that animal plankton die when exposed to nanosized plastic particles, while larger plastic particles do not affect them. Overall, these different effects of nanoplastics may have an impact on the ecosystem as a whole.

“It is important to study how plastics affect ecosystems and that nanoplastic particles likely have a more dangerous impact on aquatic ecosystems than larger pieces of plastics”, says Tommy Cedervall.

However, he does not dare to draw the conclusion that plastic nanoparticles could accumulate in other tissues in fish and thus potentially be transmitted to humans through consumption.

“No, we are not aware of any such studies and are therefore very cautious about commenting on it”, says Tommy Cedervall.

Here’s a link to and a citation for the paper,

Brain damage and behavioural disorders in fish induced by plastic nanoparticles delivered through the food chain by Karin Mattsson, Elyse V. Johnson, Anders Malmendal, Sara Linse, Lars-Anders Hansson & Tommy Cedervall. Scientific Reports 7, Article number: 11452 (2017) doi:10.1038/s41598-017-10813-0 Published online: 13 September 2017

This paper is open access.