Biodegradable Plastic Bags

The plastic shopping bag has become an epitome for environmental destruction. So how did an inanimate object come to be personalised as an environmental scourge?  And is a biodegradable alternative a viable option?

According to the Environment Protection and Heritage Council, Australians use six billion plastic shopping bags annually most of which end up in landfill. In 2002, it was estimated that fifty to eighty million bags ended up as environmental litter in parks, streets and waterways. Although many of these bags can be recycled, only three to eighteen percent are.

Half a million plastic bags are recovered each year on Clean-up Australia Day. Once in the waterways, animals often eat them, mistaking them for jellyfish, with death as the usual consequence. When the animal decays, the plastic bag again becomes part of the litter cycle because it hasn’t decomposed. Terrestrial animals can also be injured or killed if they become entangled in plastic bags.

Many countries including Australia, have taken steps to address the environmental issues created by plastic bag usage. At first we were encouraged, and still are, to reuse and then recycle each plastic bag, with many supermarkets involved in recycling programs. Products made from recycled plastic bags include new plastic bags, garden stakes, sleepers, furniture, and flower pots.

The current trend is for the rejection plastic shopping bags by replacing them with reusable bags. Clean-up Australia offers alternatives to using plastic bags for various purposes and encourages business, schools, councils and community groups to join their ‘Say NO to Plastic Bags’ campaign.
A third option is to use biodegradable plastic bags, which it seems many shops are now providing for their customers. But we must question whether and in what ways these bags are better than their petrochemical cousins.

Biodegradable plastics are relatively new to the plastics industry and are potentially an environmentally-sustainable, cost-effective alternative to petrochemical derived plastics. Two features for bioplastics are that they are produced from renewable resources and can be broken down relatively quickly while leaving no toxic residue.

Standard plastic shopping bags, like most plastics, are petrochemical-based which use oil and gas derivatives. Not only does their production rely on finite resources but the plastic industry is a significant contributor to greenhouse gases. Petrochemical plastics can take twenty to a thousand years to break down, leaving an oily residue that can be detrimental to soil and water.

Bioplastics are produced from a wide-range of renewable materials, for example plant material containing starch, cellulose, fibre and lignin. Renewable animal materials, such as milk proteins, collagen, gelatine, albumins, fish proteins and chitin can also be used. There are many types of bioplastics and several degradation processes, depending on the composition of each bioplastic.

According to the Australian Bioplastics Association (ABA), some benefits of using bioplastics include their ability to break down into to carbon dioxide and water, without leaving harmful residues. After the completion of the degrading process, they can then used for compost and biofuels which can be used in the growing and production processes of future bioplastics, completing the recycling loop.

Another key contribution for the environment is that bioplastic resins and finished products produce less greenhouse gases than similar petrochemical plastics. Bioplastics also create excellent opportunities for the agricultural industry due the wide-range of agricultural products that can be used, which utilise a variety of climates.

However, there are a number of issues with bioplastics that need addressing. The ABA is working with governments, consumer groups and stakeholders in this area. Their aim is to set up labelling and standards for the bioplastic industry that will be consistent with international testing methods and practices, and to promote bioplastics as a positive alternative for waste disposal.

The bioplastics industry has developed plastics that are claimed to be degradable, biodegradable or compostable but currently not all bioplastics meet the Australian draft standards for bioplastics [DR05402]. And even if they do, their use is not yet wide-spread enough for the implementation of effective measures to ensure decomposition and so they still mostly end up as landfill.

The microorganisms necessary for decomposition can’t survive in the oxygen-deprived, moisture-deprived landfill environment. Even if decomposition occurs, greenhouse contributing methane is produced due lack of oxygen. Disposing of bioplastics in landfill is counterproductive to their recycling process. To utilise the full potential of bioplastics, the life cycle must be completed through reuse, such as composting or energy conversion.

Compostable plastics can be managed under commercial systems that process organic kitchen waste but most councils in Australia don’t offer separate collections for organic kitchen waste. It is generally not economically viable for governments, councils or recycling industries to deal with bioplastics, although this may change as usage increases. Separation of organic waste from non-organic waste is not cost-effective either and there is the risk of contamination from toxic waste.

Organic waste makes about fifty percent of landfill in Australia, so recycling organic waste, including bioplastics, would not only solve some landfill problems but could potentially lead to new industries. The Hastings Council in NSW has a kerbside collection in place for organics. Currently the organic material is made into compost but there are future plans to convert non-putrescibles into fuel pellets.
Australia has a reasonably well-developed recycling system for many types of petrochemical based plastics such as PET, although 753,000 tonnes of plastic still ends up as landfill each year. While most councils have collection systems to recover recyclable plastics, it seems that many Australians cannot be bothered to sort their waste.

Likewise, the use of bioplastics does change the propensity of intentional littering by uncaring individuals. Bioplastic litter, aside from being unsightly, can still harm marine and terrestrial life because there is no guarantee that the degradation process will occur in unmanaged circumstances.

While bioplastics use renewable materials, consideration should to be given to the social value of the intended purpose of the bioplastic against the environmental issues of land use. As the bioplastic industry develops, increased land clearing and water usage may become a problem, along with fertilisers and pesticides used in the growing process.

The environmental consultancy company, Nolan-ITU Pty Ltd, has listed other potential negative impacts of bioplastics relating to additives and modifiers. Chemicals used in the production of some bioplastics, such as methylene-diisocyanate (MDI) and ethylene glycol, are recognised toxic substances. Prodegradants are not derived from renewable sources, may disperse catalytic metals into the environment, contribute to greenhouse gases or may disintegrate rather than biodegrade.  
 
Bioplastics have the potential to address many of the environmental issues caused their petrochemical counter-parts. Once the problems with bioplastics have been resolved, they can potentially become part of a sustainable future when used in a responsible way.

However, the biodegradable plastic shopping bag doesn’t fit the criteria for responsible use. The plastic shopping bag, whether made from bioplastics or petrochemicals, is largely a single-use and unnecessary item. It embodies the wastefulness of our society and even biodegradability cannot address this.

Biodegradable plastic bags may be useful for when reusable bags have been forgotten or for the leaky or wet grocery items, but should not be considered an acceptable replacement for other plastic bags. Reusable bags provide the best environmental alternative to petrochemical plastic shopping bags.

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