Marine plastic pollution is a massive environmental issue, with a plastic smog of an estimated 170 trillion particles afloat in the world's oceans. This highlights how urgently we need to develop strategies to mitigate this environmental crisis.
We know some microbes can break down certain plastics, but our new study finds no clear correlation between plastic pollution levels and the production of plastic-degrading enzymes by marine microorganisms.
To address this issue, we need to understand the varying properties and environmental impacts of different types of plastic.
Most plastics are not degradable
There are four main types of plastics: biodegradable, bio-based, fossil-based and non-biodegradable. The terms can be confusing and lead to misunderstandings about their environmental impact.
Biodegradable plastics can break down naturally through the action of living organisms such as bacteria. They are made from renewable sources such as corn starch or sugar cane and don't linger in the environment for long periods. Examples of biodegradable plastics are polycaprolactone (PCL), polylactic acid (PLA) and polyhydroxybutyrate (PHB).
Bio-based plastics are also derived from natural materials such as plants. These plastics include polyethylene terephthalate (PET), which is widely used for clothing and containers for liquids and food. However, while PET can be made from renewable sources, most of its production is derived from fossil fuels.
Fossil-based plastics are made from oil and gas. They include common types like polyethylene (PE), which is used for single-use food packaging, and polyvinyl chloride (PVC), commonly used for water pipes and wire insulation.
These plastics are generally not biodegradable. They do not decompose naturally and can persist in the environment for centuries, contributing significantly to pollution and global warming.
PE is the most manufactured plastic type in the world. It accounts for 103.9 million metric tons (mmt) per year, followed by PET (65.4 mmt) and PVC (50.5 mmt). However, globally only 9% of all plastic waste is recycled.
According to Plastics NZ, terms such as "bioplastic," "biopolymer," "bio-based" and "biodegradable" are being used interchangeably, even though they signify entirely different things.