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An Experiment With My Polylactic Acid Bottle.

August 2, 2017

Got a bit distracted in the most delightful way today.

So I bought a shampoo by O’Right (Taiwan innovative brand) at the Hair Expo in Sydney the other month and having just finished using it (very nice BTW) I wanted to test out if the Polylactic Acid bottle really is biodegradable – it is supposed to break down to lactic acid, Co2 and water pretty much….

Anyway, I cut the bottle up and stuck some into soil which I’d placed into an old jam jar. I did this so I can watch it degrade (or not….)

I also kept some aside to put into my new compost bin when it arrives. I want to see how that degrades in a normal compost situation. My only issue with this is whether I’ll be able to track where it is in the bin.

I kept another bit to put on my windowsill as one of the down sides with most PLA is its ability to be broken down with UV light. I want to see if it lasts longer than my pegs – Australian sun is a bugger for breaking down pegs and the Bower birds take the blue ones.

Lastly and my favourite I kept some for a chemistry experiment. I’d read a report here saying that you can break down PLA with sodium hydroxide and hydrochloric acid so I wanted to try. I did try (although I didn’t quite adhere to the rules laid out but I got the gist) and I can safely say that I made the bottle disappear (sort of). What the lab report didn’t account for is that cosmetic bottles usually contain pigments and ink which have to be filtered out. That done I’m left with a yellow solution which, when acidified with the Hydrochloric Acid becomes a clearish mixture of lactic acid and salt (including some sodium lactate I suspect). I set the final pH at around 4.6.

If you are going to try this at home do be aware that boiling up high strength lye solution is pretty dangerous as it is very highly alkaline and you have the bubbling/ boiling factor so do take precautions of your eyes and skin.  Also the Hydrochloric Acid is much stronger than the acids we typically use in a cosmetic formula so don’t go sloshing that around too.  Also be aware that the pH is very slow to reduce at the beginning but when it starts to drop it drops very quickly so it is easy to over-shoot it. If that happens just add more Sodium Hydroxide until you reach your desired pH. Basically all you’ll end up with is a more dilute solution with more salt in it.

So why bother doing this?

Well, firstly because I can (I have the chemicals on site) but mainly because it stops it going into the bin or the garden for years….

There is currently a  lack of recycling facilities for PLA here in Australia and I’m sure that’s the situation in other parts of the world too. PLA is still quite a boutique plastic, not least because it breaks down almost too quickly for most consumer goods. The O’Right company that make the product that uses this bottle give their formula a 3 year shelf life but the packaging only a 1 year shelf life.  That might not be so convenient for them over time unless their sales are pretty fast and thorough.

That aside though I thought it would be pretty damn neat if people could deal with their packaging on-site rather than pop it into a bin for collection and transportation to an off-site facility.  Practically speaking this self-disposal may end up being more energy intensive than sending it by truck to a facility off-site as the water has to be heated and the chemicals – NaOH and HCl – have to be purchased.  If you could run your facility from solar and rainwater the environmental impacts would be even less – this is one of the plans I have for my property out west – I’ve often dreamed of running my own solar powdered chemical factory, sounds like an oxymoron but I think it has legs……  Anyway what was I doing. Oh yes,  In any case I thought  that softening the plastic up with a bit of cold lye solution prior to composting might just speed up the process without adding too much energy cost to the disposal so that’s an idea too.

The bottom line is that it is possible to take a shampoo bottle that you just finished with that morning and make it disappear leaving in its place a nice acidic liquid that would be used to clean your house before ultimately flushing it down the sink with a clean conscience.  The solids filtered out of the mix would probably have to be disposed of in the garbage unless you could identify the chemicals present and ascertain whether they can also go onto your garden (titanium dioxide might be OK for that) but you are talking a few grams left over and way less space.

That’s what I call waste-to-art and I for one am looking forward to seeing more of this in the future.

Bring on the Polylactic Acid.

Amanda x


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