Bioresins, Plastic Bag Production, United Kingdom

Of the 13 billion bags provided by retail stores across the UK every year, only a small percentage are recycled or reused. In landfills, plastic carrier bags can take over 1,000 years to break down.

One of the latest campaigns against carrier bag use is by Marks and Spencer, which recently decided it would charge a £0.05 for each food carrier bag. The retailer believes this could reduce bag use by over 280 million per year.

Another alternative to this initiative is to change the material used from intractable polyethylene - which, although recyclable, is not very sustainable, being derived from hydrocarbon sources - into a compostable or biodegradable material.

This would mean that bags could be produced for around the same price as the polyethylene ones, thereby remaining free to the customer while breaking down in a landfill or composted by the end user.

COMPOSTABLE RESINS

One company that is aiming to corner the market in compostable resins across the UK is Bioresins.Eu, set up by packaging/materials entrepreneur Lutz Richter. Richter has already set up two companies in the UK - Paperfeel and A&O FilmPac - which produce polyethylene film extrusions for packaging and converting applications.

Bioresins.Eu will use the production facilities of A&O FilmPac to produce new biopolymer extrusions from granular starting materials imported from Chinese suppliers. The new resins will be cornstarch-based biodegradable and compostable resins based upon polylactic acid from non-genetically modified sources and also polyhydroxyalkanoate resins (PHA).

The cornstarch-based resins will be suitable for the same production methods such as injection moulding, extrusion and thermoforming used for more traditional polymers. PHA polymers break down within 90-120 days making them ideal for use in compostable packaging. They have already been used in dog food pouches and bird seed packaging.

PHA POLYHYDROXYALKANOATES

PHAs are polyesters first seen inside bacteria. The plastic can be grown in fermentation vessels using cornstarch as a starting material and transgenic organisms such as Arabidopsis plants, which can express the artificially induced PHA biosynthetic gene. The polymers are processed into granular form and can then be used to produce plastics for converting into packaging.

There are a range of PHAs which could be produced with a wide range of properties to suit the majority of packaging applications.

A good example is polyhydroxybutyrate (PHB), which has physical properties similar to polypropylene, even though these polymers have different chemical structures.

PHB is stiff and brittle but also has a high degree of crystallinity and a high melting point of about 180°C, but of course PHB is rapidly biodegradable, unlike polypropylene.