Biodegradable Straws Reportedly Outperform Conventional Plastic Straws

Norbert Sparrow | Apr 07, 2023

The plastic straw is one of the casualties in the war on plastics that has even some ardent plastiphobes rethinking their all-or-nothing dogma. If you’ve ever tried to use a paper straw to enjoy your Frappuccino, you know why. Other alternatives, such as reusable metal straws, also have significant drawbacks. Now, researchers in South Korea claim to have found a solution: Biodegradable straws made from lignin and citric acid that outperform paper and, more impressively, conventional plastic straws.

The scientists at the Creative Research Center for Nanocellulose Future Composites in Incheon created a casting slurry by integrating lignin, a waste byproduct from paper manufacturing, and citric acid into bio-based starch and poly(vinyl alcohol), or PVA. The slurry is cast on a glass substrate, partially dried, and rolled on a Teflon rod to fabricate the straws, explains a paper published in ACS Omega. "The straws are perfectly adhered at the edges by the strong hydrogen bonds from the crosslinker — citric acid — during drying," write Dickens O. Agumba, Duc Hoa Pham, and Jaehwan Kim in the paper. This bonding process eliminates the need for adhesives and binders.

The straws are then cured in a vacuum oven at 180°C to enhance hydrostability. The tough straws exhibit a high bending strength and were shown to be hydro stable for more than 24 hours. Moreover, they "displayed a unique balance of functionality and degradability at the end of life, making them quintessential candidates for plastic straw replacement," write the researchers.

As consumers sought alternatives to single-use plastic straws over the years, reusable metal straws started to gain some traction. However, as the researchers point out in the paper, the manufacture of metal straws entails a "high energy cost" and emits "colossal volumes of carbon oxide." They cite one recent study claiming that the fabrication of a single stainless-steel straw produces over 271% more carbon oxide emissions than its plastic counterpart. I also would add that they are simply inconvenient for use outside the home.

Straws made from biodegradable polylactic acid (PLA) have found favor in the marketplace, but they also have drawbacks, as noted by the researchers — the exorbitant cost of the raw materials, stringent degradation conditions, and poor thermal resistance.

They do not comment on straws made from canola oil–based polyhydroxyalkanoate (PHA), such as the phade straw, which can claim some commercial success. On the phade website, the company claims that PHA production results in fewer greenhouse gas emissions than PLA; is marine degradable and home compostable; and can withstand high-heat shipping.

Be that as it may, the researchers in Incheon believe they have developed a "simple, scalable, low-cost, and binder-free fabrication strategy for advanced microplastic-free straws . . . from edible starch, citric acid, and lignin, readily available and economical resources as opposed to energy-intensive cellulose-based straws."

In an article published in PlasticsToday in 2018, "Grasping at Straws: Organic Illiteracy and the Anti-Plastics Crusade," Rod Groleau writes that the tipping point in the movement to ban plastic straws was the photo of a turtle with a straw up its nose that went viral. "It got me wondering why we don't see air-breathing amphibians inhaling twigs, pencils, and crayons, which are solid and could get stuck much more easily in a nostril," he writes. "It dawned on me that Mother Nature gave us all two nostrils so that this won't happen."

Plastic straws have a storied past, as outlined in a National Geographic article from 2018, "A Brief History of How Plastic Straws Took Over the World." In a nutshell, plastic straws displaced paper straws, which were popular for several decades, in the 1960s, because they were cheap to produce, convenient, and far more durable than the alternative. As for reusable straws — long, thin tubes made from precious metals, to be precise — they date back to the Sumerians about 5,000 years ago. That practice was abandoned somewhere along the timeline of history. Plus ça change . . .

When plastic straw bans began sweeping the nation, and the world, science stepped up. In 2020, Danimer Scientific and WinCup were recognized by the Plastics Industry Association for jointly developing the first commercially sold biodegradable straws made of PHA. These are the aforementioned phade straws.

Pretty soon, if all works out for the researchers in Incheon, we may have yet one more alternative to a plastic straw that, well, doesn't suck.

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