Tuesday, 27 May 2008

Eating the plastic – an alternative to landfill?

Let your plastic bags biodegrade with a little help from some small munchers!
I read an article the other day in which some 16 year old student from Canada has supposedly identified, cultured and isolated microorganisms that help break down the polymers used in producing polyethylene plastic bags.
It’s not a new discovery but as I understand it, one of the two microorganisms identified namely; Genus "Pseudomonas" is also capable of degrading polystyrene. Burd's research on polyethylene plastic bags however may be a first.
Daniel Burd's Science Fair project won him the top prize at the Canada-Wide Science Fair in Waterloo Ottawa – with a $10,000 prize, a $20,000 scholarship, and recognition that he has found a practical way to help the environment.
On the face of it; this does appear to be an environmentalists dream with estimates suggesting we produce 500 billion plastic bags each year worldwide, and with public demand for a greener environment, it just might be worth investigating a little further.
Essentially, Burd hypothesized that since the bags eventually do degrade, it must be possible to isolate and augment the degrading agents. Hats off to this 16 year old kid who through his own particular low-tech experiments at home - identified two types of agents responsible namely; Sphingomonas & Pseudomonas which he thinks work together in producing about 32% by weight degradation after about 6 weeks through a simple process. His theory is that one organism helps the other to reproduce.
Is it worth doing?
The obvious question to me begs; is it really worth pursuing any degradation which results in breaking down the polymers? Or more to the point; if we do find an economical method will this actually render the humble plastic bag inert and safer for the environment?
If by breaking down these polymers we are only going to succeed at “breaking” the polymer chain binding into more manageable mono, and arguably “safer” compounds; then that might not prove such a positive. Some might still argue that on a molecular scale the resulting break down of those polymers would still exist (if not entirely consumed by digestion) and can even last for over 1,000 years in landfill.
Not to mention the possibility of an abundant “Super-strain” mutant polymer eating organism - fed exclusively on polyethylene bags… rampantly eating its way through our still useful and serviceable plastics!
Good plot for a film anyone?
I personally think the estimate to be nearer 100 years for natural degradation (without biodegradable additives in the mix) given all the right conditions, with sunlight playing an important roll in that process (along with oxidation with ambient temperatures or coefficients), so I guess given the natural timescales involved then; landfill is clearly not the answer.
Plastics do “naturally” degrade given some arbitrary time frame. It just might prove that this “natural” time process does indeed involve bacteria combined – perhaps with other natural chemical processes… this seems to make sense. Different types of polymers however degrade by different natural processes over widely varying timescales, and are dependent upon the environmental catalyst employed to break down those chains.
I’m not passing the buck here but we surely must all agree; that too much plastic packaging exists at POS (Point of Sale) and is discarded as waste soon after purchase. Better to make it law for the suppliers and manufactures to accept back our packaging and force them to be accountable or invent their own solution for disposal?
Only then will we see any significant reduction in our dustbins.
  • Pseudomonas are naturally resistant to penicillin
  • All species and strains of Pseudomonas are Gram-negative bacteria
  • Pseudomonas thrive in harsh conditions - a result of their hardy cell-wall that contains porins
  • Pseudomonas have the ability to metabolize a variety of diverse nutrients.
  • Pseudomonas aeruginosa is a highly relevant opportunistic pathogen.
  • Pseudomonas found abundantly in high altitudes help form rain and snow – a common nucleator of ice crystals
  • Effective iron Chelator
  • Some members of the genus Pseudomonas are able to metabolize chemical pollutants in the environment
  • Ability to grow at low temperatures and spoil refrigerated food
  • Ability to survive and multiply in a nuclear reactor - absorbed more than 10 million rep (roentgen equivalent physical) in an eight-hour day, which is 10,000 times the dose that is fatal to man.
  • Sphingomonas are strictly aerobic bacteria
  • Sphingomonas are Gram-negative bacteria
  • Sphingomonas are subdivided into four genera: Sphingomonas, Sphingobium, Novosphingobium and Sphingopyxis commonly referred to collectively as "Sphingomonads".
  • Sphingomonads play a role in human disease, primarily by causing a range of non-life-threatening infections - easily treated by antibiotic therapy
  • Sphingomonads are utilised for biotechnological applications such as bioremediation of environmental contaminants.

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