The key to creating biodegradable plastics could be in a seafood platter. While the seafood industry dumps around six to eight million metric tons of crab, lobster, and shrimp shell waste into landfills and the ocean, scientists believe that these shells are reusable.
The need for reusable plastic-like products is urgent, as non-biodegradable plastics clog landfills, pollute oceans and damage human health. Only 9% of the multiple billion tons of plastic produced by human beings has been recycled. A material named chitin found in the shells of crustaceans like lobsters and crabs could be the solution to creating biodegradable plastics. Chitin, along with its derivative chitosan, has many plastic-like properties and takes months, at most, to biodegrade. Using chitin on a large scale could both slow non-biodegradable plastic production and reduce the amount of wastage of seafood shells.
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Chitin is a polymer — a molecular chain made from repeating units. It is the second-most abundant naturally-occurring organic compound after cellulose, which is extracted from woody plants. Both chitin and chitosan are antibacterial, non-toxic and already used in various pharmaceutical and food products.
Chitin’s biodegradable nature has led to many experimental creations like the chitin and cellulose food packaging, created by Georgia Institute of Technology researchers; or Cruz Foam, a San Franciso company that creates chitin packaging foam. However, Science News reported that harvesting the 15% to 40% chitin present in crustacean shells is an elaborate process, which is both expensive and an environmental burden. Carmen Drahl from Science News writes, “To get to the chitin requires removing the protein along with the minerals, largely calcium carbonate, that makes? the shells stiff. Hydrochloric acid, a strong acid, removes calcium carbonate while generating carbon dioxide emissions; sodium hydroxide, or lye, is a strong base that removes the protein. Producing a single kilogram of chitin requires 10 kilograms of shells, six kilograms of coal for heating purposes, nine kilograms of hydrochloric acid, eight kilograms of sodium hydroxide and 330 kilograms of freshwater. Washing the chitin to remove residual contaminants can use up to an additional 200 kilograms of water.”
To reduce the environmental impact of the above process, companies that intend to harvest chitin must also invest in waste-water recycling treatment and carbon dioxide capture technology, which is expensive. While chitin production company Mari Signum‘s co-founder and chemist Robin Rogers found a way to dissolve shell waste in ionic liquid to separate the chitin, this method can only produce 10 grams at a time. Another company, CuanTec, uses microbes to extract chitin and to produce chitosan from crustacean shells. However, they also manufacture only 500 grams of chitosan in one batch. The search for mass-production methods of chitin is still underway.