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Publications archive - Waste and recycling

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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Biodegradable Plastics - Developments and Environmental Impacts

Nolan-ITU Pty Ltd
Prepared in association with ExcelPlas Australia
October, 2002

Emerging Application Areas in Australia

Until recently, the high cost associated with biodegradable plastics meant that they had limited penetration into the Australian markets of conventional commodity polymers. With the advent of new more affordable biodegradable plastics and prodegradant additives, it is predicted that by 2005 many biodegradable plastics will be cost competitive with conventional plastics, both in Europe and North America, over a broad range of applications (Kitch, 2001, p.74). Therefore, biodegradable plastics are potentially poised to expand their entry into the Australian market.

In general, biodegradable plastics are most suited to applications where the biodegradable plastic alternative has been shown through life cycle assessment (LCA) or other methods to achieve the following:

With the development of various biodegradable plastics with differing structures, properties and degradation behaviours, a range of potentially suitable application areas are emerging. For example, starch-based polymers may be suitable in agricultural and horticultural applications where no in-organic residues can result, and polymers with prodegradant additives, which maintain their structural integrity until they undergo composting, may be suitable for food waste bags.

Biodegradable plastics are well placed to substitute conventional plastics in low-weight, miscellaneous packaging applications that are not currently mechanically recycled. For example, certain streams of packaging such as take-away food containers, thermoformed biscuit trays and plastic food wrap are not collected and sorted for mechanical recycling at present and therefore may lend themselves well to substitution by biodegradable plastics that can be bioassimilated in compost. Furthermore, their high level of food residues enables such products to be compostable.

Some of these emerging application areas in Australia are outlined below.

5.1 Coated Paper

Coated (or laminated) paper products represent a significant market for biodegradable plastics. The present paper products for hamburger wrappers and disposal cups are extrusion-coated with low-density polyethylene film that is resistant to biodegradation. It also retards the biodegradation of the paper substrate since it acts as an impervious barrier.

5.2 Agricultural Mulch Film

Agricultural mulch films are utilised in some agricultural applications, such as tomato cropping, as a mulch soil cover to inhibit weed growth and retain soil moisture. These films could be potentially made from biodegradable plastics to eliminate the need for mechanical removal, as the mulch films could be ploughed into the soil. These films could also prevent the loss of topsoil humus that can be removed along with the waste film, and also enrich the soil with additional carbon.

A range of the biodegradable plastics available may be suitable for this application - such as TPS, AAC and controlled degradation masterbatches. Degradable starch-filled conventional polyethylene films may be unacceptable due to residuals that can build up in the soil over time (Kitch, 2001).

5.3 Shopping Bags

Plastic bags and other packaging films have a high profile in the Australian waste stream, as these materials are currently not widely accepted in the kerbside recycling system. Biodegradable plastics present a potential alternative to these materials in some applications.

5.4 Food Waste Film and Bags

Film, wrap and bags for food scraps, food residuals and food products destined for composting in commercial composting facilities, is a potential application area for biodegradable plastics. Conventional plastics are a significant contaminant in organics processing and they reduce the marketability of the compost produced (Goldstein & Block, 2000). These applications depend on the disposal environment being a commercial composting operation which provides the necessary conditions for the polymers to degrade.

An application for biodegradable plastics is for plastic films used in fresh food wrapping and plastic wrap used in catering industries. The reason that a biodegradable film could be advantageous in these areas is that a significant amount of food waste from catering companies and shopping centres can potentially be diverted to commercial composting facilities.

If composting of municipal solid waste and food waste becomes more prevalent, this may dramatically increase demand for biodegradable plastics in the form of compost bags and food scrap bags. For example, numerous towns in Northern Italy have been using biodegradable bags for transporting food residuals since 1998 (Kitch, 2001) and a major European producer of biodegradable plastics, Novomont, receives the majority of its revenue from compostable food bags and has a 10,000 tpa production plant servicing this market. Such bags would take 8-10 weeks to fully degrade in a commercial composting operation.

5.5 Consumer Packaging Materials

One of the major potential application areas for biodegradable plastics is consumer packaging. A wide range of plastic consumer packaging materials are not currently mechanically recycled, and may therefore be suited to the use of biodegradable plastics; however, life cycle assessment studies are needed to determine the impacts of biodegradable and conventional polymers for these uses. The various uses and likely disposal environments of different packaging products would require the use of different biodegradable plastics with appropriate mechanical and degradation properties.

Another strategic fit for biodegradable plastics is the beverage six-pack rings market. In the USA almost all plastic six-pack rings have been made of photodegradable LDPE plastic since the early 1990's. At least 16 US states-including Massachusetts, New York and Rhode Island - have passed laws requiring six-pack holders be biodegradable (these are marked by a small diamond between the rings). Pepsi for example, has a policy to purchase only photodegradable plastic sixpack rings. It should be noted that photodegradable plastics are not a complete solution in themselves as they require 6-8 weeks of sunlight to degrade and will not degrade if buried.

Other related applications include bread bags, bait bags, disposable food preparation gloves, drinking straws, and loose fill packaging.

5.6 Landfill Cover Film

The use of biodegradable plastic films as degradable daily landfill covers could considerably extend landfill life. Landfills require a daily cover, currently usually soil, to discourage flies and other disease carriers, control odour, minimise windblown litter and discourage scavenging birds and other animals. Using soil for the daily cover typically results in a 25% loss of available landfill space.

5.7 Other Applications

Other potential applications for the range of biodegradable plastics include: