Confusion between ’Oxo’ and ’Hydro’ In Study of Biodegradable Plastics in Landfill

In May this year, researchers at North Carolina University, USA published a report on the performance of biodegradable plastics in landfill. It concluded that some of them might be doing more harm than good. The findings were published online in "Environmental Science & Technology"

Symphony Environmental issued the following statement:

"It is really important not to confuse the two fundamentally different types of biodegradable plastic.

The NC State report is about hydro-biodegradable or "compostable"plastic, which is usually made from vegetable matter.

This type of plastic is intended for industrial composting, and that is why a rapid rate of degradation is required by ASTM D6400; EN13432; and Australian 4736. It is not designed to degrade in the open environment, and it will emit methane (a more powerful greenhouse gas than CO2) deep in landfill.

We agree with the NC State University report, but they have not distinguished between "compostable" and oxo-biodegradable plastic.

Oxo-biodegradable plastic will not cause the problem they have identified, because it has a deliberately slower rate of degradation and it is inert in landfill in the absence of oxygen.

The fundamental point about oxo-biodegradable technology is that the additive, included at low cost at manufacture, turns ordinary plastic at the end of its useful life in the presence of oxygen into a material with a different molecular structure.

At that stage it is no longer a plastic and has become a material which is inherently biodegradable in the open environment in the same way as a leaf. Approximate timescale for degradation can be set at manufacture as required. For a video of plastic film degrading, go to http://degradable.net/play-videos/4