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BIOPLASTICS EXPLAINED

What differentiates bioplastics from conventional plastics?

Bioplastics differ from conventional plastics in that they are biodegradable, biobased or both.
Biodegradable refers to a natural process during which micro-organisms that are available in the environment convert materials into natural substances such as water, carbon dioxide and biomass (artificial additives are not needed!). The process of biodegradation depends on the surrounding environmental conditions (e.g. location or temperature), on the material itself, and on the application. Biodegradability is an inherent property of certain bioplastic materials that can benefit specific applications (e.g. food / organic waste bags, food service ware, agricultural films and wraps).

Biobased means that the material or product is either in full or in part derived from biomass (plants) and biomass used to produce bioplastics may be from corn, sugarcane or cellulose for example.

Compostable

Compostable describes materials that are suitable for microbial treatment at end of life in a composting environment, whether commercial or in the home. Products or materials that pass the required standard for such microbial treatment in these environments may be verified as compostable according to the requirements of the Australian Standards AS 4736-2006 (biodegradable materials suitable for commercial composting) and Australian Standard AS 5810-2010 (biodegradable plastics suitable for home composting).

For a product or packaging to be verified compostable according to the Australian Standards it must biologically disintegrate and biodegrade in the relevant composting system to set levels within a defined period of time. The resultant compost must meet specific quality and ecotoxicity criteria.

The origin of raw materials in some bioplastics does not affect the inherent property of biodegradability, of those materials. Thus, some biodegradable materials can be made from oil based raw materials.

Why use bioplastics instead of non-bioplastics?

Bioplastics are biodegradable, biobased or both.

Biodegradable plastics, those verified as compostable, provide a disposal option of composting in a commercial composting station or the home compost heap and help facilitate the diversion of food waste from landfill to composting. Some biodegradable plastics can be used in products that will biodegrade in or on soil, for example agricultural film.

Biobased plastics, those made using renewable resource feedstocks, reduce consumption of fossil fuel resources. Renewable resources are regenerated annually with the plant matter absorbing carbon dioxide during growth.

What is driving the change?

The growth of the market for sustainable resins derived from renewable resources is driven by recognition that fossil fuel resources are finite and will one day run out. Change is required and this is recognised by business and governments around the world who are encouraging recycling, composting of organic waste and use of sustainable and renewable materials.

Certified compostable and therefore biodegradable bioplastics provide an option for organic and food waste recycling, that is not possible with plastics that are not biodegradable. A verified commercially compostable product, when sent to composting with food and other organic waste, will biodegrade in commercial composting conditions to water, carbon dioxide and a small amount of carbon humus within six months. Similarly a verified home compostable product, when placed into well set up and maintained home composting conditions will biodegrade to water, carbon dioxide and a small amount of carbon humus in six months.

Landfill is not the preferred disposal option for any organic matter, including biodegradable and compostable plastics, which will behave in landfill the same as any other organic matter. Landfill conditions vary so greatly that it is not possible to predict how long it will take the biodegradable plastic, or a tomato, to biodegrade. The same must be said for all plastics, despite some claims to the contrary.

There are Australian standards, AS4736 – 2006 and AS5810 – 2010, which specify the conditions that must be met for a plastic to be considered compostable. It is voluntary for manufacturers to verify that their products conform to them. Rowan Williams, president of the Australasian Bioplastics Association, which administers the verification scheme in Australia, says it’s easy to know if a plastic has been verified by looking at the label (see How do I know it’s biodegradable?). “Unless it is verified, then it may not actually be compostable,” he says.

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