IP Information & News

A natural solution to shooting’s plastic problem

Dr Clair Curran

By Dr Clair Curran

Senior Patent Attorney

1 October marked the start of the pheasant shooting season in the UK. It’s estimated that over 30 million pheasants are raised and released in the UK each year for shooting on over 2,000 hunting estates. Wales has just announced it’s banning the practice from next year, and whatever your thoughts on pheasant shooting, there’s another problem — plastic.

The plastic problem

Despite the Countryside Alliance’s Code of Good Shooting Practice stating “guns should use cartridges with degradable wads where possible and all cartridge cases and other litter should be removed after each shoot”, discarded plastic shotgun wads litter the countryside each season.

Over half of the shotgun wads used in the UK are made from non-biodegradable plastic. Biodegradable alternatives (such as paper, card or felt wads) exist, but they’re only used by a small percentage of shotgun users — and often only when the use of plastic wads is banned by the landowner.

On the whole, plastic wads are cheaper. Performance-wise, some of the biodegradable wads make relatively poor gas seals, and don’t protect the barrels from steel shot.

During firing, the wad is flies out of the barrel along with the shot. Typically it lands out of sight, or beyond reach of the shooter. Most shotgun wads are never retrieved. The abandoned debris poses a significant safety and environmental risk within both land and aquatic ecosystems.

The problem is compounded by most of the shotgun wads eventually fragmenting into microplastics that can spread even further throughout the aquatic food chain.

The anatomy of a shotgun cartridge

A shotgun cartridge is made up of five components: primer, case, propellant powder, wad and shot (see fig. 1 of US 9,528,800).

The cartridge case houses all of the components. The case is generally made from plastic or paper and is removed from the barrel once the gun has been fired. The case can be recycled — Agri-cycle recycles spent plastic shotgun cases into innovative, durable products, including outdoor furniture.

The wad separates the propellant from the shot and forms a gas-tight seal. When the propellant converts from solid to gas when ignited, it forces the wad and the shot out of the end of the cartridge, with the shot pellets travelling at approximately 1,400 feet per second.

Another weapon in the armoury against the scourge of plastic

Researchers at the Virginia Institute of Marine Science (USA) have solved the balancing act of developing a degradable wad that has sufficient durability to function as a shotgun wad, yet quickly degrades into benign components. This innovation has been patented in the US (US 9,528,800).

The solution — polyhydroxyalkanoate (PHA).

Patenting a naturally-occurring product for a new use

PHA is a true naturally occurring biopolymer.

It’s a bio-based, rather than a petroleum-based, polymer. It’s synthesised naturally by over 300 microorganisms via the fermentation of sugar and lipids. Bacteria produce PHA as a granule within the cellular structure to store energy, similar to the way humans store fat.

PHA is biodegraded quickly by microorganisms into benign, naturally occurring monomers and oligomers, both in land-based and aquatic environments. Due to its sustainability, biodegradability, and biocompatibility, PHA is used in a wide range of applications. These include single-use packaging for foods, beverages and consumer products, as well as medical applications like cardiovascular patches, sutures, bone marrow scaffolds, bone plates, and nerve guides.

Despite this, the use of PHA as a shotgun wad has been patented. This is because the use is novel and non-obvious.

US 9,528,800 describes the unexpected properties of shotgun wads made from PHA:

  • PHA has the unexpected advantage of degrading by weight at least twice as fast when continuously submerged than when it’s submerged most of the time but periodically exposed to light and air for brief periods. As PHA has a specific gravity greater than one, it has a tendency to sink and therefore be continuously submerged.
  • PHA wads are as functional as non-degradable plastic wads.
  • PHA is sufficiently durable to withstand being discharged from a shotgun, remaining intact until exiting the barrel, with fragmentation then rapidly occurring.
  • PHA does not significantly impact the shot pattern.

A plastic-free future

GreenOps Ammo (USA) is hoping to market cartridges that include PHA-based wads later this year.

For the moment, the UK doesn’t have an outright ban on the use of plastic wads. Interestingly, the 2015 GunsOnPegs and Strutt & Parker Game Shooting & Fishing Census found that, although 81.6% (1,758) of respondents preferred fibre wads, some 17.4% (374) still preferred to use plastic.

And, although 62.9% (107) of the shoots stipulated the type of wad that must be used, only one stipulated the use of fibre.

With a technical performance that can at least match that of plastic wads, combined with the clear environmental benefits, hopefully it won’t require a change in the law for the degradable wad to become the ammunition of choice.

If you have a new use for a naturally occurring product and want to find out how you might be able to protect it with IP rights, please feel free to drop me an email at cxc@udl.co.uk.

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