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Plastic Bags To Fuel: It’s For Real

If your Facebook feed is anything like mine, you may have seen a few posts by various environmental groups kicking up a big stink about the amount of plastic that’s floating around in our oceans – and justifiably so. You might have seen a few pictures of the notorious Great Pacific Garbage Patch (floating around in the North Pacific somewhere between Japan and the USA). A lot of it is in the form of polyethelene, which is not biodegradable – the only thing that breaks it down is sunlight, which is why we deal with it by burying it in landfills underground where the sun can’t get at it. There are literally mountains and islands of it out there.

At the same time, folk are looking around at the existing crude oil supplies and realising that they aint gonna last forever.  This, as well as the pollution issue, is one of the spurs driving the push towards hybrid vehicles, electric vehicles and biofuels.

Plastic is, however, another petroleum-based product.  In other words, once upon a time, the lid of your coffee cup, your chip packet and your polar fleece top came from the same stuff that you put in your car to get to work this morning.  What if this process could be reversed?  What if you could un-refine the plastic and turn it back into oil that could then be refined the other way and used to keep our cars (and trucks and trains and ships and aeroplanes) running?

Well, they can do it.  A few teams around the world have come up with ways to take all that waste plastic and convert it into something that can be used as a fuel feedstock – for diesel.  I’m not a chemical engineer, so don’t ask me why most of the fun new technologies for producing greener fuel end up producing diesel rather than petrol (with the exception of ethanol, which plays nicely with petrol, as we’ve known for years here in Australia). Although one Aussie company called Foyson  Resources (aren’t you proud?) has come up with a way to get petrol out of plastic.

The technology for converting plastic back into some form of oil has been around for at least 10 years, with companies in Japan, China, India, the Philippines and the US all having a go at it.

The process they use is called pyrolysis.  Those of you with a smattering of Greek may recognise the “pyro” bit, which indicates that heat is involved.  Literally, the process means “separating by heat”.  It’s been described as a sped-up version of how oil fields and fossil fuels came to be in the first place.  Basically, the long polymer strings made up of lots of carbon, oxygen and carbon atoms  get split apart into shorter bits about 18 carbon molecules long.

OK, let’s ditch the chemistry and describe it simply.

1: Appropriate plastics are fed into the machine, usually after being shredded or chipped. Suitable plastics usually include polyethylene, polypropylene and a few others – but not PET (Recycling #1), which is easier to recycle.

  1. The shredded plastic is heated slowly and turns to a gaseous form. The exact temperature at which this happens can be anywhere from 250°C through to 400°C, depending on the pyrolysis plant in question.
  2. The gas is cooled to a liquid: crude oil. Bingo!
  3. Other gases keep going and have to go somewhere. With some pyrolysis plant designs, the gas is captured and used to heat the pyrolysis chamber. However, some of the gases can be a bit nasty, which is why the kibosh was put on a Canberra plastic-to-fuel plant last year.
  4. Leftover solids come in the form of “carbon black”. This can be used as a construction material or just like old-fashioned coal, which it’s practically identical to.

It seems to be early days still for the plastic-to-oil process in Australia, with the Foy Group (the ones who have got the grant to start a plant in Hume, Canberra) facing a few hurdles thanks to the possible emissions. However, given (a) the amount of plastic waste we all churn out and (b) the need to find good supplies of the crude for our petrol and diesel, I’m sure these hurdles can be cleared.  I’m picking plastic-to-petrol as The Next Big Thing for greener motoring – and it won’t require any changes to our existing vehicle fleet.

If you’re really, really keen, it is apparently possible to do the plastic pyrolysis thing at home and make your own diesel. This probably comes with a heavy cost in the form of the energy input needed to heat a home-built plant, with the result that all the oil you produce will then be used to run the generator or powerplant used to heat the pyrolysis plant used to produce the oil and round it goes. At least it gets rid of plastic bags…

I personally would not try this at home and prefer to either cut down on the plastic bags I use or send them to the recycling depot.  However, if you are keen and want to try, this page tells you how.   No guarantees and do it at your own risk!

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