Naked Science Forum
Life Sciences => The Environment => Topic started by: Bill.D.Katt. on 20/05/2011 21:48:33
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Since plastics are highly broken down by UV light, in a landfill it would take plastics an eternity to break down. On the other hand, if the non-recycleable plastics were incinerated in a high-oxygen environment, the negative effect on the atmosphere would be high, but which would be worse?
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the negative effect on the atmosphere would be high
I don't think incineration in in a high oxygen environment would have a huge negative effect on the environment (not worse than burning an equivalent weight of oil), so provided the heat is captured and used to make savings on other energy uses (for example to heat greenhouses or generate electricity), I think burning is probably better. But I haven't looked in detail into the pros and cons.
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I agree that the heat would have to be harnessed, otherwise it's just wasted energy.
If there is one thing I know about our economic system, it's that if something is making a lot of money, then it's not going to stop. We can do all the things we can short of collapsing the oil industry, and in the end the multi-billion dollar product -plastic, is still going to remain. The idea of being environmentally friendly is to be economically conscious, otherwise nothing we be accomplished.
Looking at the structure of dioxin, it appears that under high temperatures and excess oxygen, the compound will further oxidize. And dioxin isn't the most toxic substance known to science.
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"composed of toxic chemicals"
Most plastics are practically non toxic.
"dioxin, the most toxic substance known to science."
Wong again.
"The only way out of the deadly and lasting danger of plastic"
How many has it killed?
How many lives have been saved by it?
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Certainly there are different types of plastics.
The majority of the plastic that you get today are basically hydrocarbons and hydrocarbon polymers. They should burn just fine.
Teflon and related substances are fluoridated hydrocarbons, and perhaps should be treated differently.
I believe that one method of recycling the plastic is to essentially replace, or add to coal in coal burning power plants.
There was a Japanese You-Tube film about converting plastic back to oil which could be used as auto fuel.
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Plastic waste is suprisngly difficult to deal with.
This in part relates to the varieties of plastic as the the only reliable way to seperate is by hand. Loads of single type plastic (such as agricultural sillage wrap, mdpe pipework from utilities etc.) are worth consdierably more than "mixed rigids" (as the leaat valuable form of recycled plastic is known). Recycling plastic is marginally economic as it is so cheap to produce in the first place.
It is untrue to say that plastic does not breakdown in landfill - as well as the biological processes there are physical and more particularly chemical factors at play. If you drill a hole into a landfill site (to extract gas) the arisings from depth are pretty uniform black sludge, with fragements of stuff but generally nothing recognisable. Any resource value in the plastic is more or less lost when landfilled (and don't get me started on the fantasy that is "landfill mining"!)
"Energy From Waste" schemes - whether incinerators or the use of refuse derived fuels in cement kilns or industrial boilers - relies in the plastic fraction for energy because burning plastic is exothermic. High temperatures and long residence times (how long the hot gases are kept to high temperature) can keep down "toxic emissions" although will tend to increase NOx production. However, energy production from incinerators is retarded by the moisture content of the waste and the production of refuse derived fuels (such as "Eco deco" process) require energy input to produce a consistent, dry product.
I would suggest that the thermal decomposition of plastic without air to produce a liquid - either as a fuel or as a presursor for plastic production - could well be the way forward! Although I have found disapointingly little about that Japanese vid.
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Hi all
I see the opportunity to burn plastic in a kiln (at very high temperatures) a good alternative to dispose them to landfill.
At those temperatures the production of toxic gases are negligible and with the help of gases filters in use today the chance for an air release are minimal. Besides that we'll be using the calorifics characteristics of the plastic to sbstitute oil, coal and even natural gas.
My two cents!
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European plastic incineration requires flaming @ 1560*f for 2 seconds so to burn dioxins...ithinx