Our oceans are filling with fragments of plastic. The Great Pacific Garbage Patch comprises three massive, floating marine debris “islands” within a circular ocean current, or gyre. The gyre’s rotational pattern draws in plastic waste from across the North Pacific and concentrates the debris in the center of the ring of currents, where it remains trapped. Large plastic items caught in the gyre are eventually weathered from exposure to sunlight, and they fragment into microplastics, fragments of plastic commonly defined as smaller than 0.20 in (5 mm). The small size and suspension of these particles over a widely dispersed area and up to 100 ft (30 m) or deeper in the water column means there isn’t actually an island, so aircraft or satellite imagery can’t detect the patch. However, scientists who have sampled the water estimate that in 2018, the patch covered 620,000 square miles (1,600,000 square kilometers). And tons of plastic continue to accumulate in the patch.

Marine debris accumulation locations in the North Pacific Ocean (NOAA, Wikipedia)

There are similar garbage patches in other oceans. Between North America and Africa is the Atlantic garbage patch, and there is a South Atlantic garbage patch, a South Pacific garbage patch, and an Indian Ocean garbage patch. Plus, the Mediterranean Sea is one of the world’s greatest plastic accumulation areas, with reported concentrations of microplastics that are comparable to those found in the ocean gyres.

People have filled these waters with small fragments of toothbrushes, cell phones, water and soda bottles, fishing gear, packaging material, pens, plastic pellets called nurdles, and many other plastic bits. The garbage patches are stark reminders of the tremendous amount of plastic pollution that is being produced globally – and the major environmental pollutant that plastic has become. Many of the plastic items will last for hundreds and even thousands of years before degrading. The expanding quantity of plastic in the world’s oceans is raising concerns about alterations to the marine carbon cycle, toxic chemicals that leach into the water, hazards to marine creatures who ingest the toxins and that collect in the food chain (and can ultimately reach humans; researchers have found common plastic polymers in human blood) and to all creatures from zooplankton, fish, birds, sea turtles to whales, who mistake plastic debris for food or become tangled in plastic debris – often with fatal results.

The unaltered stomach contents of a dead albatross chick include plastic marine debris fed the chick by its parents, photographed on Midway Atoll National Wildlife Refuge (Wikipedia)

Greener Options

Conventional petrochemical packaging, including the widely used polystyrene (“Styrofoam”, packing peanuts, bubble wrap, and many types of containers) breaks down into microplastics and is a major source of pollution. Fortunately, scientists and engineers are developing novel alternatives for many tasks currently filled by these petrochemicals. Typically, these incorporate plant and animal materials, since over millennia, nature has developed highly efficient ways for organisms to break down organics. Two alternative packaging materials that especially intrigue me are the mycelium of fungus like mushrooms and spider silk.

Mycelium – the tiny binding fibers (essentially “roots”) of fungus grow rapidly. A packaging material from mushroom mycelium was first popularized by the company Ecovative Design, founded in 2007. Conveniently, mycelium branches as it grows, forming self-assembling bonds, and will fill all the space available. Agricultural waste products, including oat hulls, cotton burrs, corn stalks and husks, provide the food and structure for the mycelium used for packaging. The fungus is added to this organic material and within a few days grows to fill empty spaces in molds that can be virtually any shape and size–essentially, bespoke packaging. Then, the new material is heat treated to kill any spores and stop the growth process. The packaging that is created is light, strong, and fire-resistant. The material is shelf-stable in dry indoor conditions, but when broken up and added to compost, microbes and moisture break it down fully in about 45 days. Mycelium gives us an amazing material, created at a fraction of the energy and chemical inputs required for materials it can replace. Plus, helpful nutrients are added back into the environment.

Mycelium of the most common type of cultivated mushroom (Agaricus bisporus) (Wikipedia)

Biodegradable wine shipping container made by Ecovative Design using mycelium (Wikipedia)

European companies are at the forefront of greener product development, and the giant home décor company IKEA, based in Sweden, has made a commitment to phase out plastic from consumer packaging by 2028. Among the alternatives that they will use is mycelium packaging, produced by Ecovative Design.

Spider silks are protein-based fibers with an extraordinary combination of strength and extensibility. Over millions of years, spiders have developed at least seven different silk types to build the orb webs that withstand the capture and struggles of their much larger prey. The silk is superior to most man-made-fibers, and strength, or stress needed to break the fiber, exceeds that of an equivalent amount of steel.

Illustration of the differences between toughness, stiffness and strength. Spider dragline silk has a tensile strength of roughly 1.3 GPa. The tensile strength listed for steel might be slightly higher – e.g. 1.65 GPa, but spider silk is a much less dense material, so that a given weight of spider silk is five times as strong as the same weight of steel. (Wikipedia)

People have been using spider silk for several thousands of years for fishing, wound coverage, and other tasks. However, they cannot farm spiders successfully. The reason? Spiders are cannibalistic, so group living isn’t an option. Recently, however, through biotechnological magic (recombinant protein production), spider silk can be produced on a large scale using the DNA sequence “donated” by the spider and produced in a “host” bacterium, typically Escherichia coli. Production of the desired specific silk type can occur in about 3 to 4 days.

Researchers are finding many applications for spider silk. Most interesting to me is that they could replace some common plastics, including plastic bags. Another angle is to replace the microplastics that currently protect and gradually release active ingredients in products such as herbicides and other agricultural sprays. (Current practices of spraying plastic capsules all over food crops could use an update, IMO!) Like mycelium items, the spider silk degrades into natural compost.

Given their strength and toughness, designers and engineers can use spider silks in many construction materials and in textile items, such as parachutes. The lightweight, breathable, and UV resistant characteristics make them ideal for a variety of types of clothing. There are also many medical uses as artificial materials for prostheses and skin. The work on large-scale production of artificial spider silk is gaining momentum.

Awash in Plastic

Commercial manufacturing of plastics derived from fossil fuels dates from about 1950 but has skyrocketed in the past few decades. In a global analysis of all plastics ever made and their fate as of 2015, published in the journal Science Advances, of the 8.3 billion metric tons produced, about 6.3 billion metric tons are now plastic waste. Of this waste, about 9 percent has been recycled, and 12% incinerated, but the vast majority is languishing in our landscapes. None of the commonly used plastics are biodegradable, so rather than decomposing, they are accumulating.

The plastic waste generated by Amazon, the western world’s largest online retailer, has been analyzed by the international organization called Oceana. A report released in December 2022 states that Amazon generated about 709 million pounds of plastic packaging worldwide in 2021, up 18% from the online sales surge that produced about 599 million pounds in 2020. (Amazon has not outlined a plan nor committed to a company-wide reduction in plastic use, although it is reducing the use of plastic in some markets.) Most of the bubble wrap, air pillows, and padded envelopes Amazon uses are of plastic film that will not be –and in many regions cannot be — recycled. The result? A significant portion of this plastic waste ends up in the oceans.

Finding substitute materials for plastics and producing these on a large-scale will be a step in controlling plastic pollution. More importantly, curbing the global appetite for plastic will require rethinking consumer use (especially of single-use plastics), product design, recycling, uses for recycled plastic material, and other strategies. Fortunately, all these options are gaining traction. Trading some convenience (and chemical company profits) for a cleaner and healthier environment is possible in the years ahead.

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Eisoldt, L., Smith, A. and Scheibel, T., 2011. Decoding the secrets of spider silk. Materials Today14 (3), pp.80-86. https://www.sciencedirect.com/science/article/pii/S1369702111700578?via%3Dihub
Geyer, R., Jambeck, J.R. and Law, K.L., 2017. Production, use, and fate of all plastics ever made. Science advances3(7), p.e1700782.  https://www.science.org/doi/pdf/10.1126/sciadv.1700782
Gu, Y., Yu, L., Mou, J., Wu, D., Zhou, P. and Xu, M., 2020. Mechanical properties and application analysis of spider silk bionic material. e-Polymers20(1), pp.443-457. https://www.degruyter.com/document/doi/10.1515/epoly-2020-0049/html?lang=en
Leslie, Heather A.; van Velzena, Martin J.M.; Brandsmaa, Sicco H.; Vethaakab, A. Dick; Garcia-Vallejoc, Juan J.; Lamoree, Maria H., 2022, “Discovery and quantification of plastic particle pollution in human blood”Environment International1 (3): 1
Mojumdar, A., Behera, H.T. and Ray, L., 2021. Mushroom mycelia-based material: An environmental friendly alternative to synthetic packaging. Microbial Polymers: Applications and Ecological Perspectives, pp.131-141.
Oceana, 2022, The Cost of Amazon’s Plastic Denial on World’s Oceans, December. https://oceana.org/reports/the-cost-of-amazons-plastic-denial/
Simon-Sánchez, L., Grelaud, M., Franci, M. and Ziveri, P., 2022. Are research methods shaping our understanding of microplastic pollution? A literature review on the seawater and sediment bodies of the Mediterranean Sea. Environmental Pollution292, p.118275.
Photo of spider web with fog droplets, 2009, by Brocken Inaglory. https://commons.wikimedia.org/wiki/File:Spider_web_with_fog_droplets_2.jpg
Figure showing the ocean currents and locations of the largest plastic Pacific Garbage Patches, 2010, by NOAA.  https://commons.wikimedia.org/wiki/File:Pacific-garbage-patch-map_2010_noaamdp.jpg
Photo of mycelium (Agaricus bisporus), 2011, by Rob Hille.   https://commons.wikimedia.org/wiki/File:Mycelium_RH_(8).jpg
Photo of a bio-degradable wine shipping container made by Ecovative Design using a novel biomaterial grown from agricultural waste using mycelium. 2011, by Mycobond. https://commons.wikimedia.org/wiki/File:Biodegradable_wine_shipping_container.jpg
Illustration of the differences between toughness, stiffness, and strength. Spider dragline silk has a tensile strength of roughly 1.3 GPa. The tensile strength listed for steel might be slightly higher – e.g. 1.65 GPa, but spider silk is a much less dense material, so that a given weight of spider silk is five times as strong as the same weight of steel, 2011, by Vincentsarego.            https://en.wikipedia.org/wiki/Spider_silk#/media/File:Wikipedia_Kevlar_Silk_Comparison.jpg