In a very recent paper scientists talk about the discovery of a bacterium ("Ideonella sakaiensis") which can "eat" PET, one of the most common types of plastic.
I was wondering what effect this would have in our society but in any of the press articles that I've read they don't mention possible consequences of this fact. What are the consequences of this discovery? Would the levels of recycling PET decrease due to the possibility of using this bacteria to degrade PET plastics?
From what I've read the bacteria can completely degrade PET-film in 6 weeks via two enzymes that turn PET into terephthalic acid and ethylene glycol. Both substances are both environmentally benign.
This means that we may be able to use these bacteria to clean up plastics in the environment. However this may not be very easy because a PET bottle for example is different from PET film. PET bottles are made from highly crystallised PET. In this article the lead scientist is quoted:
Dr Miyamoto said that it was not as simple as unleashing armies of PET-metabolising bacteria into landfills to break down waste plastic. "Because of its crystal structure, the rate of degradation is very slow. However, after heat-treatment at 260 degrees, the crystal structure breaks down, allowing these micro-organisms to easily decompose the plastic," he said.
Even if the slow-degradation problem is solved, the question remains whether there are any unwanted effects if the bacteria are used on a large scale (e.g. release of toxic substances that are often present in plastics, or increase in CO2 emissions). Also, it isn't probable that the current strain of bacteria can be used to clean plastic in the oceans.
Personally I think it's more likely that the bacterium can be used in a new method of recycling PET. Terephthalic acid and ethylene glycol are the building blocks of PET, so in controlled conditions the bacteria may be able to convert old PET into these resources.
Scientists are probably going to search for other new bacteria with similar and perhaps even more beneficial properties. Who knows what they are going to find. So as Fred also mentioned in his answer, it's too soon to tell what the exact consequences are going the be. A lot will depend on how this will develop further. Can we find or engineer better bacteria, are there unwanted side effects, and what are the costs going to be for using the bacteria.
Given that the announcement of the PET eating bacteria has just been made there may not be enough knowledge, or knowledgeable people, to properly answer your question.
Because of this, you question could be closed as being potentially too broad given the lack of knowledge about the bacterium and the result of what it does with PET plastic.
Any development of plastic eating bacteria will be influenced by cost and what waste products, if any, are produced and how harmful they could be to the environment.
If using plastic eating bacteria is cheaper than recycling plastic then plastic recycling plants could close.
Another outcome of plastic eating bacteria is potentially an increased use of plastic instead of other packaging materials because then we would have a cheaper and possibly better way of disposing of the plastic afterwards.
Composite plastic films are becoming quite common and are hard to recycle. By using bacteria to eat the PET layer the rest could be recycled.
An interviewee for the article I read about this (probably in the guardian) suggested that the breakdown product could be a feedstock for plastic manufacturing. If so that would fit well with my suggestion above.
The question was "would the levels of recycling PET plastic decrease." This is a question with several answers, Firstly, if the plastic was broken down it wouldn't be recycled, except that the resultant chemicals could be utilized which would be a form of recycling. The other point is that plastic film in Britain is not recycled at all, which should make the use of the bacteria obligatory. I would hope that the levels of PET would rise and replace other plastics. This could be a result. We would be buying things in PET sachets rather than plastic bottles, and these could be collected along with film used for other purposes and considerably reduce waste plastic. I have one caveat here though. If these bacteria are not really naturally occurring species, the environmental impact could be catastrophic.
