Bay Journal

Latest weapon to reduce marine debris? Biodegradable shotgun wads

Plastic would disappear before it could enter the food web

  • By Leslie Middleton on May 31, 2016
Shotgun shells are one of the most common items collected during beach cleanups. VIMS researchers are testing shotgun wads, shown above, made from a biodegradable polymer.  (David Stanhope / VIMS)

In the struggle against litter, inventive minds have come up with a passel of products that disappear on their own if carelessly discarded in the outdoors. Biodegradable bags, bottles and plates, to name a few. Next up: ammunition, perhaps?

Researchers from the Virginia Institute of Marine Science are developing a biodegradable shotgun wad to deal with one of the more common types of plastic debris found in wetlands and waterways.

“I never expected to be dealing with shotgun shells but it does show how widespread and ubiquitous plastic is,” said environmental scientist Kirk Havens, director of VIMS Center for Coastal Resources Management.

The shotgun wad — a small plastic component of the shell used to separate the shot, or pellets, from the powder — is fired out of the barrel along with the shot. It typically lands 20-40 yards from the shooter, often out of sight or even beyond reach, in the water or a marsh.

Lt. Col. Dan Knott, avid hunter and professor of military science at University of North Carolina at Chapel Hill, picks up trash on every beach he visits with his family. “Especially in the Chesapeake — there’s so much duck and goose hunting here — we see these wads everywhere.”

An estimated 10 billion to 15 billion plastic shotgun wads are produced annually. They are one of the most common items collected during beach cleanups. They’ve also been found in the stomachs of albatross and other ocean foraging birds. The plastic pronged wads are perhaps mistaken for tasty squid.

Most shotgun wads eventually fragment into smaller and smaller pieces. In the water, those bits of “microplastic” tend to spread even farther throughout the aquatic food chain.

At VIMS, researchers are testing wads made from PHA, or polyhydroxyalkanoate, the same biodegradable and commercially available polymer they used to make escape hatches for crab pots that disarm lost or abandoned fishing gear.

Made from bacteria, PHA breaks down into its carbon and water constituents in both marine and fresh water.

The prototype PHA shotgun wad may take 1–2 months to disintegrate, said Jason McDevitt, director of technology transfer at the College of William and Mary. But McDevitt said there may also be ways to make the wad fracture as soon as it leaves the gun barrel, so that its fragments are no longer recognizable and biodegrade more quickly.

Making shotgun ammunition with biodegradable wads could add about $1 to the cost of a $25 box of shells, Havens said. Depending on the product, that could be an increase of around 5 percent to start, he said, but if the biodegradable wads catch on, the price would likely drop.

Development of a market-ready shotgun shell got a boost last July from a grant for additional testing from Virginia’s Commonwealth Research Commercialization Fund. The VIMS team is evaluating how well prototypes can match the regular wad in performance, including muzzle velocity, barrel pressure and shot patterns.

Manufacturers are showing interest, McDevitt said, as some anticipate hunting regulations could begin requiring degradable plastic wads, starting possibly on federal lands.

There could be military applications for the new product as well. Knott noted that every branch of the armed services is committed to sustainability and protecting natural resources. A biodegradable shotgun wad would truly leave no trace, he said, which would be a good thing for the military, hunters and all manner of living things in the Bay and beyond.

“It’s a remarkable product,” Knott said. “Whether the shotgun wad degrades in land or water, this could have multiple operational benefits.”

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About Leslie Middleton

Leslie Middleton writes about water quality, public access, and the special places of the Chesapeake Bay region from her home in Charlottesville, Virginia.

Read more articles by Leslie Middleton

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