Science – A global plastics pollution treaty?

The success of a future global treaty on plastics waste will require a better understanding of the nature of plastic materials. For a start, the public needs to better understand the difference between the terms, ‘plastics’ and ‘polymers’. All plastics are polymers but not all polymers are called plastics. Polymer is a generic scientific term for all chain-like molecules, while plastic is a common-use term for a subset of these. Plastics is the term generally used to describe polymers that are in broad, commercial consumer use. Polymers used in high-value specific applications such as surgery are simply called polymers.

Perhaps the most pervasive commercial polymer in existence is polyethylene. “Poly” means many and “ethylene” is the molecular (mer) unit repeated in the chain structure. Flexible polyethylene exists in two forms, high density (HDPE, type 2) and low density (LDPE, type 4), which differ in density and flexibility but not in composition. HDPE is more rigid and is fully recyclable in NZ. LDPE is even more widely used in flexible packaging films and is more flexible and softer. LDPE is not always recycled in NZ because of machine separation entanglement issues. In other developed countries, including Australia, LDPE is generally recycled. In Auckland, only three types of polymer/plastic are commonly recycled: types 1 (PET), 2 (HDPE) and 5 (Polypropylene). In due course, all commercial plastics are expected to be recyclable.

The agreed global strategy for 100% recycling is called the Circular Economy network, which is monitored by the World Economic Forum (WEF) and the Ellen McArthur Foundation (USA). The WEF network includes 250 global strategic partners including Unilever, Dow, Coca Cola, Nike, Philips, Renault and H&M. The largest global source of plastic bottle pollution, the Coca Cola company, is committed to the Circular Economy. Coca Cola will make 100% of its packaging recyclable globally by 2025 and use at least 50% recycled material in its packaging by 2030, as well as collect and recycle a bottle or can for each one sold by 2030.

NZ Trade and Enterprise estimates the economic advantage from the Circular Economy to be worth US$4.5 trillion globally and NZ$8.8 billion for Auckland alone through the reduction in wasted resources, the optimisation of material lifecycles, and consumer demand. Many high-value polymers are deployed in specialised and long-term applications. For example, hospitals use polymers extensively for sutures, catheters, monitors, keyboards, gloves, surgical sheets, drip lines, syringes, paints, flooring, drapes and so on. Special medical-graded biocompatible plastics are essential for human-contact surgical items. These include polyethylene, polypropylene and poly (vinyl chloride).

Important applications of specialised polymers include their use in planes and cars. Polymers are used as light-weight materials to increase travel distance efficiency and so reduce greenhouse emissions.

The Boeing Dreamliner consists of 80% polymers and polymer-composites by volume. Modern fuel-efficient cars consist of about 60% of polymers and polymer-composites.

A survey this year reported that 90% of people polled across 28 countries support a UN global plastic pollution treaty. A total of 85% want manufacturers and retailers to be held responsible for plastic packaging. However, in seeking to achieve these laudable objectives, it will be important, firstly, that plastics/polymers, their value and their problems are better understood. Secondly, and even more importantly, worldwide consumers must accept that they are a critical part of the problem and of the Circular Economy solution.

• Ensure that all (100%) plastics waste identified as recyclable types 1,2 and 5 are placed in the recyclable bin. At last count, only about 60% of recyclable plastics are being put out.

• Choose only retailers in appliance purchases that accept packaging back for recycling.

• Urge local politicians to pursue the policy target of 100% recycling of packaging materials.