Landfill could be greener than recycling when it comes to plastic bottles

The ubiquitous PET bottle, used around the world to package drinks, may best be buried after use rather than burnt or reconverted into a second-life product. According to an independent study that I and a colleague just completed,  the footprint of recycling is lower than that of landfills only if at least half of the plastic ends up being valorised. That’s right: only if about 50% or better of the used PET actually displaces production of new PET, will recycling deliver the lowest footprint.

In recycling programs using kerbside collection, typically less than 50% of the used bottles end up displacing new PET (an abbreviation of polyethylene terephthalate). Programs using take-back obligations, separate collection or bottle-deposits, however, tend to report much higher displacement rates – some in the range of 75%.

And what about burning it all? Charging used bottles to waste incinerators converts them largely to the greenhouse-gas carbon dioxide, which then goes straight into the atmosphere. This footprint debit can be reduced somewhat by generating power and heat from the incinerator. However, waste incinerators even at their best are inefficient power generators, so the net effect is still far more ‘carbon positive’ than either recycling or landfilling.

Carbon capture on a budget

What this suggests are two important points for policy makers. One, in regions that already have a recycling infrastructure, the low-carbon aim should be to boost used PET’s displacement of new PET significantly above 50%. The key to this is not in raising kerbside collection rates, which already have achieved rates of around 80%, but in improving yields, especially in sorting and to a lesser extent in reprocessing. Even non-experts should be able to see this: collecting clean, relatively pure used-material will yield a much cleaner, purer recyclate than collecting a slop of mixed materials. The technology for cleaning and sorting plastics is none too great and unlikely to improve dramatically – so the fix must be in collection.

The second point for policy makers is this: in regions or countries without a recycling infrastructure, the lowest-carbon choice may well be to landfill bottles. Happily for them, it will tend to be the cheapest choice as well. Call it ‘carbon capture and storage’ if you will, on an economy budget. And the carbon really is stored: degradation of plastics in landfill, even under wet conditions, is very minor.

Two other points of general interest came out of our study. One is the correction of a misperceived conventional wisdom. Often it is said that the common practice of shipping baled PET bottles to China for recycling is an ecological nonsense, that it overrides the benefits of valorisation. Not true, says our study. Yes, the transport adds to the footprint, but not nearly as decisively as displacement. If the travelling bottles end up substituting what would have been new PET, then the journey was well worthwhile.

Finally, we found that PET recyclate has a lower carbon footprint than new (virgin) PET. Manufacturers making product from recycled PET – such as straps, films and fibres (say, for fleeces and similar garments) – should be able to claim that they are lower-carbon than alternatives made from new PET. Maybe governments or consumer groups could help out by awarding such products low-carbon labels.

Eric Johnson is a director of Atlantic Consulting, an independent consultancy based near Zurich, Switzerland. +41 44 772 1079, ejohnson@ecosite.co.uk  The carbon-footprint study, 'PET’s carbon footprint: to recycle or not to recycle' , is aimed at producers and users of PET as well as regulators and policy makers.

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