Thursday, 16 May 2013
Recycling
There are several videos showing the conversion of plastic to oil and, although this one is rather light on the finer technical detail, I think it's one of the better ones. As a particular supermarket says 'every little helps'.
The machine, produced in various sizes, for both industrial and home uses, can easily transform a kilogram of plastic waste into a liter of oil, using about 1 kW·h of electricity but without emitting CO2 in the process. The machine uses a temperature controlling electric heater instead of flames, processing anything from polyethylene or polystyrene to polypropylene (numbers 2-4).
Comment: 1 kg of plastic produces one liter of oil, which costs $1.50. This process uses only about 1 kW·h of electricity, which costs less than 20 cents!
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11 comments:
That's brilliant, Rosie.
I particularly liked the way he was allowed into schools to demonstrate to the children the actual machine working.
Can't help thinking that over here, all sorts of "Risk Analyses" would have to be carried out, and, all the kids kitted out in PPE. After all, he was dealing with electricity, hydrocarbon gases & flammable oil!
Such thermal pyrolysis on a domestic basis is highly dangerous.
The process only works on a limited range of plastics – so hands up those who can differentiate their polyethylene, from their polystyrene from their polypropylene from any of the other modern plastics – get it wrong and you could kill yourself.
In fatal household fires it is not the fire that kills but the highly toxic fumes, usually cyanide, from domestic plastics produce.
Many modern plastics when heated release toxic substances with oestrogenic activity eg ‘bisphenol A’ and ‘bisadepate’; both now linked to many cancers and to heart disease.
Such pressure cooking of plastics can also release highly toxic dioxins and furans, both notorious for the devastating effects they can have on human health.
Equally, what they don’t tell you is that this pyrolysis process, pressure cooking, releases methane, ethane, propane and butane gasses (the bubbling gasses) all of which are highly flammable and at the right concentration explosive!
Such technology is best kept at the industrial scale were all the necessary controls and safeguards can be implemented.
Domestic application of such technology is a dangerous gimmick.
JRB is right. Pyrolysis is a technique with a lot of potential. There is a company near Bristol that has a small plant that can process all sorts of materials including car tyres. These actually produce so much heat that they have to be carefully added to keep the temperatures in the right zone. The same company has provided small units for the Royal Navy. The prime goal there is to drastically reduce the volume of waste so that it can be returned to the UK rather than dumped at sea.
Certainly it seems to be one of those win-win technologies.
It is also worth noting that in a properly managed pyrolysis plant energy can be recovered, (rather than added as in the example shown).
The Bristol plant operates in a single-storey building on a 'light' industrial estate and the exhaust gases are discharged from a low-level stack as the 'obnoxious' elements mentioned by JRB are scrubbed or catalysed as needed.
But can it cook egg and bacon?
Although JRB has pointed out the dangers of this Joe, I too liked the way children were involved. We could involve our children more in practical sciences.
No hands up here JRB and I appreciate your input. I did realise plastics emit poisonous fumes though.
I'm surprised there aren't more businesses doing this Jim. Is that because it's not so profitable do you think?
Seems we'd rather send our rubbish half way around the world.
Erm... pass Demetrius. :)
SR: I'm not sure about the economics. Clearly in your original example it was worth paying to put energy into the process if the end product can be sold for more and if there are no costs against the 'residue'.
In the case of the Bristol plant a lot of effort had gone into making it a 'clean' system and that involved components that they had manufactured under non-disclosure agreements. This means that the technology isn't free for everyone to adopt and that the 'roll-out' is restricted to the number of systems that they can manage.
I understand that in the first instance they had been selling to people with high-cost waste e.g. hospitals and the Royal Navy. You will appreciate that clinical waste can't just be 'thrown in the bin' but costs hospital trusts a lot to dispose of. The idea is to have small plants on the hospital site itself. Similarly the navy has to operate 'squeaky clean' nowadays and it costs a lot to repatriate waste from deployed ships, hence the onboard plant.
I imagine that the business plan is to cream off this premium waste business to recover the development costs. As manufacturing costs are reduced and IPR protection tails off I expect the system to be used more widely and to cut into the land fill market.
Jim, I really appreciate your comprehensive information. Now I'm quite a bit wiser on the issue.
Perhaps the equipment prices will drop once the initial costs have been recouped? As JRB says though it's a process which can only been undertaken by experts.
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