Are bio-derived plastics the solution to plastic pollution?
Single-use plastics are useful but can be bad for the environment. They harm animals on land and in our oceans and can persist in our environment for hundreds of years. It’s estimated that global use of plastic products will double by 2040. Much of this waste is from plastic packaging.
But change is on its way. Australia is phasing out single-use plastic packaging and has set a national target of 70 per cent of plastic packaging recycled or composted by 2025. Many states and territories have introduced bans on single-use products such as plastic bags, straws and cutlery.
To help meet Australia’s target, CSIRO is researching different plastic types, including solutions to break down plastics.
On a mission to end plastic waste
Plastics have an important role in providing low weight strong packaging for handling and transportation. Plastics are also integral to protecting and preserving food products. But we also need to reduce its impact on the environment.
Pete Cass from CSIRO Manufacturing is part of CSIRO’s Ending Plastic Waste Mission in development to reduce 80 per cent of plastic waste entering the Australian environment by 2030. He is looking at environmentally friendly substitutes for plastic packaging.
“My research aims to improve the performance of compostable bio-derived plastics. To compete with existing single-use plastics, alternatives need to be cost-effective, robust, degrade faster and have improved oxygen and moisture barrier properties,” said Cass.
“Increased recycling of conventional plastics would be beneficial too, but we still need to improve waste management to stop plastics ending up in the environment.”
The credentials of bio-derived plastics
Biodegradable bioplastics can be sourced from chemical-based materials or renewable natural materials. On interaction with water and microbes, biodegradable bioplastics totally degrade into nothing more than water and carbon dioxide.
“Products that currently benefit from biodegradability include food and soil-contaminated plastics that are unable to be recycled or are highly likely to enter the environment,” explained Cass. “This includes coffee pods, fresh food packaging, shopping bags and picnicware. However, they are currently limited to short-term storage of foods. Storage of liquids is problematic as moisture is a trigger for their degradation.
“To be certified as ‘biodegradable or compostable’, the material and resulting products need to go through a rigorous testing process. Bioplastics are generally more expensive to manufacture and currently make up only 1 per cent of the market, but there is increasing consumer demand.”
CSIRO is researching bioplastics capable of fully degrading into carbon dioxide and water. That is, leaving no residual microplastics, toxic residues or lasting footprint. This includes developing new and improved plastics such as natural and synthetic polymers, as well as plant-derived materials. It also includes testing the resultant materials according to internationally recognised standards.
The break down on compostable plastic
Biodegradable plastics are not necessarily environmentally degradable. To meet Australian Standards, the environment needs to be defined, such as compost. The degradation must occur at an appreciable rate.
“Compostable plastics fall into two categories – industrial compostable and home compostable. The difference lies in the composting temperature and degradation time,” explained Cass.
“To be certified as industrial compostable the item needs to disintegrate within 12 weeks and biodegrade within 180 days at 60 degrees Celsius in an industrial composting facility.
“Industrial compostable packaging is typically comprised of bioderived polylactic acid (PLA). While this reduces the reliance on fossil fuels, products comprised of PLA such as cutlery and takeaway coffee cups require an industrial composting facility and will not breakdown quickly in the environment. Inappropriate disposal in oxygen deficient environments, such as landfill, will result in the formation of the pollutant methane.”
Industrial composting services are fairly limited in Australia. The cost to collect these items can also be expensive and the community need to separate the waste into a different waste stream than general recycling.
Home compostable plastics degrade at temperatures less than 30 degrees Celsius. They must disintegrate in less than six months and biodegrade within 12 months. They are typically weaker than industrial compostable plastics.
Oxo-degradation and greenwashing products
Oxo-degradation technology involves combining common plastics such as polyethylene with catalysts that use atmospheric oxygen to fragment the plastic into microplastics.
“The performance benefit of oxo-degradation is that the mechanical and barrier properties of these conventional plastics are retained. They do not require moisture for disintegration. However, several studies have found significant levels of microplastics remain in the environment and have potential to be taken up into the food chain,” explained Cass.
Greenwashing is a recently coined term about products that are supposed to be beneficial for the environment but are either misrepresented or have misleading claims. For example, non-degradable plastics combined with organic materials or bioplastics have a high likelihood of forming persistent microplastics, landfill degradable plastics will form microplastics or methane, and bioPET is non-degradable.
The government’s National Plastic Plan aims to target these classes of plastics, with companies that make false or misleading labelling and environmental claims being referred to the Australian Competition & Consumer Commission for investigation.
We can all reduce plastic waste
On average, Australians use 130 kg of plastic per person each year. Developing alternatives to single-use plastics is one solution to reducing plastic waste and pollution.
“One easy thing we can all do is to avoid single-use products. If we use takeaway coffee cups as an example, most go straight into the rubbish bin due to their plastic lining. Biodegradable coffee cups need to be industrially composted, otherwise they are going to landfill too. Where possible, it would be better to take a reusable cup if you want to have the least impact on the environment.”
Along with revolutionising plastic packaging, other solutions CSIRO is investigating to help reduce plastic waste is advanced recycling technologies and monitoring rubbish through surveys, artificial intelligence and rubbish traps.
Learn more about CSIRO’s plastic pollution solutions.