January 2010 - The Environmental Impact of Oxo-degradable Plastics, Loughborough University
The study of Loughborough University has two main conclusions: the legth of time it takes for oxo-degradable plastics to first degrade and then biodegrade cannot be predicted accurately; Oxo-degradable plastics may have indesirable consequences on disposal facilities and on natural environment.
Oxo-degradable plastics are made of petroleum-based polymers (usually polyethylene (PE)) which contain additives (usually metal salts), that accelerate their degradation when exposed to heat and/or light. The plastics are fairly common in the market, being used in a range of applications including carrier bags, packaging and agricultural films. Oxo-degradable plastics are often marketed as being ‘degradable’, ‘bio-degradable’ or ‘oxo-biodegradable’; implying a reduced environmental impact at the point of disposal compared to plastics without the additive. This research project assessed the environmental effects of oxo-degradable plastics from their production to disposal. The main purpose of the project was to assess what happens to the polymers and metal salts after the material starts to degrade and to assess whether this has beneficial or negative effect on the environment, compared to plastics that do not contain the additive. The project reviewed evidence behind the marketing claims being made about oxo-degradable plastics, in particular, assessing the evidence that these materials degrade or biodegrade, and under what conditions and timeframe.
The study concluded that incorporating additives into petroleum-based plastics to accelerate their degradation does not improve the environmental effects of the plastic because:
• The length of time it takes for oxo-degradable plastics to first degrade and then biodegrade cannot be predicted accurately;
• The length of time it takes for oxo-degradable plastics to first degrade, then biodegrade, ultimately depends on the environmental conditions to which they are exposed. Although it is likely that oxo-degradable plastics will start to degrade between 2-5 years in the UK, it is unclear how long the material takes to biodegrade;
• Oxo-degradable plastics do not meet established composting standards, such as EN13432, though they do not claim to. Therefore, oxo-degradable plastics should not be disposed of in home or industrial composting facilities;
• As oxo-degradable plastics are not compostable (and as all types of plastics are likely to biodegrade given enough time), the term ‘biodegradable’ on oxo-degradable plastic packaging is meaningless and potentially confusing to consumers when choosing how best to dispose of the material;
• Oxo-degradable plastics may have undesirable consequences on disposal facilities and the on natural environment;
• There is a lack of evidence about the fate of oxo-degradable plastics in the natural environment. As the concentration of metal additives contained in the plastics is low, they are unlikely to significantly increase concentrations which occur naturally in the environment;
• Oxo-degradation is sometimes promoted as a strategy to reduce litter, but whether this is actually a beneficial or harmful, depends on what happens to the plastic fragments in the environment. There is concern that the plastic fragments may be ingested by insects and animals, but this has not been investigated;
• Oxo-degradable plastics are not suitable for inclusion in conventional recycling systems;
• The available evidence suggests that oxo-degradable plastics do not degrade in anaerobic conditions, such as would be found in landfill;
• Any degradation to carbon dioxide that occurs is contributing to fossil-based carbon emissions.
The best means of disposal for oxo-degradable plastics is incineration, or if incineration is not available, then landfill is the next best option. Both of these options make the ‘degradable’ property of oxo-degradable plastics irrelevant.
Loughborough University, 2009. Assessing the Environmental Impacts of Oxo-degradable Plastics Across Their Life Cycle.