A NEW HOPE FOR PLASTICS

by Adelia Ritchie, Spring 2020
Photo by John F. Williams
Photo by John F, Williams

A NEW HOPE FOR PLASTICS

by Adelia Ritchie, Spring 2020

 

If you’ve ever had to clear out those pesky cobwebs from every corner of your house, you know how ubiquitous and stubbornly persistent our house spiders can be; not to mention the incredible variety of spiders in our forests, fields, gardens, and backyards. Spiders are everywhere. There’s one about six inches away from you right now. But whether we love them or hate them, they’re here to stay. And those cobwebs? They’re made of spider silk, strong filaments of protein, a type of polymer produced from the spider’s silk glands.

 

confused yet?

Polymer? Plastic? Bioplastic? Before we move on, let’s clear up a few terms that are commonly used in the plastics industry.

 

Plastic: The subject of this issue of Salish Magazine, this stuff is everywhere in our lives. Plastic is the term that describes materials made from long chains of carbon atoms. It’s a tough material, waterproof, and does not deteriorate in the garbage heap, so it stays in our environment for hundreds of years. Plastics are generally of two types—those made from fossil fuels mined from deep within the earth and those made from living things (plants, animals, fungi).

Polymers are long chains of atoms, usually carbon atoms. All plastics are polymers, but not all polymers are plastic. For example, your milk jug is a plastic polymer, but other carbon chain polymers—proteins, gasoline, WD-40, candle wax—are not plastics.

Bioplastics are plastic materials made from living (or recently dead) things, like cornstalks, sugarcane, mushrooms, and even shrimp shells and spider silk!

Most of today’s plastics are composed of polymers made from fossil fuels—oil, natural gas, and coal. Plastics made from fossil fuels are non-biodegradable and tend to pile up in landfills, streams and oceans. The hazards of fossil fuel extraction, transportation and emissions—from oil spills to groundwater pollution to climate change—compound this pollution problem.

the good news

Fortunately, creative scientists and engineers are working on a wide variety of solutions. It will be difficult indeed to convert our world to a plastic-free one, but alternatives that are biodegradable and not made from fossil fuels could be part of the answer, e.g., bioplastics.

Bioplastics are plastic-like polymers made from renewable biologicals, primarily from plant materials like corn and sugarcane. Although there are several issues surrounding the farming of crops for the plastic industry (monoculture, herbicide and pesticide use, GMO concerns), bioplastics are either compostable or otherwise biodegradable, which could greatly reduce the impacts of discarded plastic.

Graphic assembled by Adelia Ritchie

Now that the truth about fossil-fuel-based plastics has become impossible to ignore, researchers are scrambling to develop better alternatives. Some of the most exciting recent innovations focus on learning from nature: mimicking the plastic-like qualities of spider silk, shrimp shells, and even the cell walls of mushrooms.

The above image links to the article it is from: “Finns break ground with novel biomaterial” published in GoodNews from Finland.

biopolymer from spider silk?

The Aalto University and VTT Technical Research Centre of Finland are researching a potential way to solve this issue—with a little help from spiders and trees. See link in photo above.

In a paper published in September 2019 in Science Advances, scientists describe a new material created by merging cellulose fibers from wood with the silk protein found in spider webs. The result is a strong, flexible material that could do everything plastic does, only better—except, of course, clog up the planet.

Now, use your “spidey sense” to imagine how many hard-working arachnids would be needed to scale up production to rival that of plastic! One might predict the arrival of a host of arachnophiles to protest outside the university against the exploitation of their beloved spiders. However, in their research the Finnish scientists didn’t use a single thread of actual spider silk.

“We used birch tree pulp, broke it down to cellulose nanofibrils and aligned them into a stiff scaffold. At the same time, we infiltrated the cellulosic network with a soft and energy dissipating spider silk adhesive matrix,” says Pezhman Mohammadi from VTT. In simpler terms, they’re using bacteria that have been modified with synthetic spider silk DNA to “grow” molecules that are similar to natural silk, and combining these with a scaffold made from birch tree pulp. The resulting substance is a “natural” form of plastic that does not depend on fossil fuels, and is biodegradable.

“Because we know the structure of spider silk DNA, we can copy it and use this to manufacture silk protein molecules that are chemically similar to those found in spider web threads,” lead researcher Markus Linder of Aalto University explains in the release.

Honestly? The plastic industry is not threatened by spiders, in any sense. But new biomaterials like this hybrid of spider silk and tree pulp, in addition to more concerted international efforts to curtail single-use plastics, might make us look at our household cobwebs in a whole new light. 

got shrilk?

Shrimp and many insects have rigid, plastic-like exoskeletons (cuticle) made of a strong, layered polysaccharide called chitosan. Researchers at Harvard’s Wyss Institute have developed a fully degradable bioplastic by combining chitin, a waste material of the shrimp industry, with boiled silkworm pupae, once a byproduct of silk extraction, to mimic natural insect cuticle. This new material, called “shrilk,” rapidly biodegrades when composted.

Because the US Food and Drug Administration has already approved these ingredients for medical purposes, shrilk also may be useful for creating implantable foams, films and scaffolds for surgical closure, wound healing, tissue engineering, and regenerative medicine applications.

With 95% of all animal species being six-legged creatures, insects and shrimp have potential to become the basis for “natural” plastics that are strong, flexible and lightweight. Even so, while this research is promising, it is still in the early stages, expensive and not yet ready for large-scale manufacturing. But don’t let that bug you. Research on other plastic alternatives is mushrooming!

fungus amongus

The cell walls of mushrooms are lined with chitin, which makes them strong and flexible, just like it does for insects and shrimp. And fungi grow incredibly fast, they’re readily available in nature, they’re sustainable, and are thought of as the great recyclers of the natural world.

Issue #6 of Salish Magazine contained several articles about fungii.

At the Design Academy Eindhoven in the Netherlands, designers Maurizio Montalti and Wösten have found a way to take fungi’s mycelium, the underground root-like network of branching filaments, and letting it glue straw and sawdust particles together to make a variety of objects, from high-heels to furniture to lampshades. This mycellia mixture is grown in molds for several weeks, and then oven-baked to kill the fungi and prevent further growth.

Above image is from the National Geographic article it links to, September 22, 2017

In the UK, Sebastian Cox, a furniture maker, noticed two branches on his property that seemed to be stuck together. When he tried to separate them, he realized they were glued together by a fungus. After some helpful advice from the British Mycological Society and some experimentation, Cox developed a process to mix Fomes fomentarius with scrap wood chips to create “myceliated wood.” With a small chunk of this substance and a mold to grow it in, Cox eventually produced a fungus-made lamp and stool!

If you’re thinking mushroom furniture is a bizarre idea, it’s probably not that much different from items made from leather or beeswax, and if you give it time it will probably grow on you.

Adelia Ritchie grew up on a northern Virginia farm with horses, cattle, dogs, and her pet pig Porky, who ran the whole show. A long-time resident of the great Pacific Northwest, Adelia is a serial entrepreneur, scientist, educator, and artist, and currently works with educators and legislators to promote a deeper understanding of the science of climate change and its impacts on the complex ecological web of life. Adelia resides in Hansville, WA, with her garden, her dogs and a flock of very entertaining chickens.

Table of Contents, Issue #7, Spring 2020

Prêt-à-Porter Plastics

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FIND OUT MORE

Finns break ground with novel biomaterial

The Problem With Plastic: How The Story of Stuff Project thinks about our plastic – and its solutions, from The Story of Stuff Project.

25 cheap and easy replacements for plastic in your home and kitchen, Business Insider

Fungus: The Plastic of the Future, Motherboard

Biomimetic composites with enhanced toughening using silk-inspired triblock proteins and aligned nanocellulose reinforcements, in Science Advances

A new material made from spider silk and trees could replace plastic, from Mother Nature Network