Science – Problem plastics

For international travellers, plastic waste seems to exist everywhere – even on the most pristine and unique seascapes and landscapes. Most of the plastic materials swirling in gyres around the world’s oceans, including the Pacific Ocean, emerge from rivers in highly populated but relatively poor countries in the Asia-Pacific region. Much of this plastic waste originated in consumer-driven wealthier countries, but then the waste was “sold” to the poorer countries. The flow of plastic waste into the oceans is mainly the result of inadequate waste management in these poor countries via local streams or rivers.

Within Europe, 26 per cent of plastics are recycled and another 36 per cent are used to produce energy. This short-term thinking still leaves 38 per cent (10 million tonnes) going into landfill, despite a zero target for landfill by 2020, which is being promoted within the European Union. This problem obviously requires both a national and international response.

Firstly, adequate waste management systems are needed urgently in the poorer countries. Secondly, about two-thirds of all commercial plastics are polyethylene, polypropylene and polyethylene terepthalate (PET), all of which are recyclable. Recycling can be encouraged via financial incentives, which would also provide community income for poorer communities. Thirdly, the existing ocean gyres of plastics will need to be removed by large-scale physical collection, involving booms and nets.

Simple incineration often creates secondary problems. Polystyrene foam packaging (recycling rate only 12 per cent) needs to be used more sparingly until more extensive reuse options are developed, as it generates toxins when incinerated. The incineration of chloro-plastics (such as PVC) needs to be carefully controlled, as incineration of PVC generates dioxins and furans, which are potent carcinogens. A recent regional proposal involves the development of a major multi-plastics recycling industry in South Australia, which is expected to serve other states and might also serve New Zealand.

It is important to note that while eliminating single-use plastic bags, the world will continue to need plastics for specialist uses such as for packaging food to minimise wastage. Also – as we enter the age of electric cars, boats and planes – lightweight plastics and polymer composites make these innovative forms of transportation even more efficient. Further, surgical and healthcare devices for an aging population are frequently made of plastics.

These future uses must involve more advanced material stewardship leading to minimum environmental impacts. The Unilever Circular Economy model appears to be the world leader with its target of 100 per cent recyclable plastics by 2025. There is now a stronger expectation that the current environmental plastics crisis may be largely solved within a decade. That would provide a positive global legacy for our children and grandchildren.

Professor Ralph Cooney
r.cooney@auckland.ac.nz