A new research report from a Swiss consulting firm says that unless the yield from recycling PET bottles is 50% or greater, disposing of the bottles in a landfill will lead to a lower carbon footprint.
“Recycling is definitely not always the lowest environmental footprint,” said Eric Johnson, the Zurich, Switzerland-based research analyst of SRI Consulting and author of the report PET’s Carbon Footprint: To Recycle or Not to Recycle. “You need to look at what happens to all the plastics collected.”

“For recycling to make sense from a carbon footprint standpoint, you need to get back at least 50% of the material you collect. For every 100 tonnes you collect, you need 50 tonnes to come back and go into resin for products,” said Johnson in a phone interview. “If you can’t do that, you need to think whether you should be doing it because if you do it badly, it doesn’t make sense from an economic and environmental standpoint.

“For countries with adequate space and with little recycling infrastructure, disposing of bottles in a landfill generates a lower carbon footprint than recycling or incineration,” he said.

Both the Association of Postconsumer Plastic Recyclers and the National Association for PET Container Resources declined to comment on the report, which was published 9 August.

Johnson said that take-back programs and PET bottles collected through deposit programs generate yields large enough that those recycling efforts produce a lower carbon footprint than landfilling, but that curbside programs do not.

The report analyzed the carbon footprint of PET bottles from production of raw materials to disposal, and secondary packaging from cradle to grave. SRIC is based California and part of SRI International.

“The problem with curbside collection for plastics is that you end up with a high amount of contamination from both mixed plastics, as well as dirt and crud, and that tends to downgrade the quality of the recyclate, and you also lose a fair amount of material when you wash and sort,” said Johnson. “Maybe as much as one-third of the material collected goes to low-grade applications or is lost during the cleaning process.

Based on evaluation of the best curbside collection programs in Europe, SRIC calculated that the yield from the collection of 100 tonnes of recycled PET is roughly 45 tonnes—meaning that disposal of the bottles would create a lower environmental footprint.

Johnson said that the problem isn’t the amount or levels of material collected at curbside, but the poor yields when it is sorted and separated. “The key to this is not in raising collection rates, but in improving yields, especially in sorting and to a lesser extent in reprocessing,” said Johnson.

Yields are not a problem when bottles are collected through take-back or deposit programs, he said. “Precise figures are a bit vague, but the yield is probably around 70%,” he said.

“However, take-back and deposit systems cost more than curbside, and they cover less material,” Johnson said. “So in a nutshell what we’re saying is that the design of the recycling system is critical. If you’re going to recycle plastics, you’re better to cherry-pick some fractions such as PET bottles, do them properly—probably not through curbside—and ignore the rest. If you can’t do it right, you’re probably better off to landfill, if you have space.”

Johnson said he understands that recycling has become more important globally as people try to conserve natural resources. But he says that whether that should be the driving reason to recycle “depends on how scarce you think those resources are.”

“All petrochemicals as a percent of oil are less than 5%,” said Johnson. “I realize that you have to start somewhere, but there are a lot more obvious places to cut energy use than to recycle PET bottles.”

His advice? “If you are going to recycle, do it right in the first place,” Johnson said. “Cherry-pick where you see that you will get a steady stream of containers, do it on a large-scale, and use separate bins for key containers.”

The other findings of the report:

* PET recyclate has a lower footprint than new virgin PET, and manufacturers making product such as straps, films and fibers from recycled PET should be able to claim that they are lower-carbon alternatives than similar products made from new PET.

* The distance that baled PET bottles are shipped does not significantly affect the carbon footprint even when they are shipped to China.

* Incineration creates the highest carbon footprint because burning used bottles in waste incinerators sends the greenhouse gas carbon dioxide directly into the atmosphere. “This footprint can be reduced somewhat by generating power and heat from the incinerator, but the net effect is still carbon positive,” said Johnson. “Most incinerators are not efficient power generators because they are designed to get rid of waste.”