General > General Technical Chat

How to recycle plastics

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langwadt:

--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

Zero999:

--- Quote from: langwadt on August 03, 2022, 02:39:43 pm ---
--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

--- End quote ---
Not necessarily. For example hybrid cars are more efficient than those with plain old internal combustion engines.

Fossil fuel power plants burn coal or gas, which are consistent and still much cleaner than plastic, which will be mixed with other rubbish.

When rubbish is just burned, it releases a large volume of toxic gasses, as well as the CO2 and H2O. The advantage of gasification is a smaller volume of syngas can be cleaned, before it's burned in an internal combustion engine, which will have a very clean exhaust because the fuel is so clean. Another advantage of gasification is the syngas can be stored, although that requires a lot of space as it becomes unstable at high pressures.

Internal combustion engines have a greater dynamic range and can be started and stopped fairly quickly. Turbines take awhile to get up and running and have to be run at a certain speed to achieve optimum efficiency.

tooki:

--- Quote from: Miyuki on August 03, 2022, 08:30:55 am ---
--- Quote from: pcprogrammer on August 03, 2022, 07:53:41 am ---There are almost 8 billion people in the world, but nobody want's to do this kind of work.

Basically due to the fact it does not pay well, and there is a social stigma on it because people look down on the people who do these kind of jobs.

Here in France we can put all our plastics and other recyclables, except glass, into a yellow bin and wheel it to the curb every other week. No idea what they do with it once collected. Since this was setup we only need to put the brown bin, with the other no recyclable waste, out at most twice a year. The yellow bin about once every 6 weeks.

So it is good for our conscience and we feel less guilty 8)

--- End quote ---
Here is what happens to the content of yellow bins across Europe
It is not as bad as I expected. Energy usage seems to be widespread


--- End quote ---
Take that graph with a huge grain of salt: most likely, it counts as “recycling” to collect it for recycling and sending it abroad to be recycled (where it may not actually be recycled). What makes me suspect this is Germany’s positive appearance on this graph, while other sources I’ve seen (in various German-made documentaries) show that while recycling rates are high (in the sense of collection), huge amounts of plastics are not processed within Germany, but sent to Eastern Europe, which means they’re likely not actually getting recycled at all.

Switzerland is a huge outlier in this regard: aside from having very high rates of plastic collection (82%-95%, depending on who you ask), nearly all collected plastic is also recycled within Switzerland, ensuring it’s actually recycled. (For PET, none is exported at all, apparently.) Since Switzerland does export plastic abroad (to Germany, mostly), that must be the non-PET plastics.

Zero999:

--- Quote from: tooki on August 03, 2022, 05:44:03 pm ---
--- Quote from: Miyuki on August 03, 2022, 08:30:55 am ---
--- Quote from: pcprogrammer on August 03, 2022, 07:53:41 am ---There are almost 8 billion people in the world, but nobody want's to do this kind of work.

Basically due to the fact it does not pay well, and there is a social stigma on it because people look down on the people who do these kind of jobs.

Here in France we can put all our plastics and other recyclables, except glass, into a yellow bin and wheel it to the curb every other week. No idea what they do with it once collected. Since this was setup we only need to put the brown bin, with the other no recyclable waste, out at most twice a year. The yellow bin about once every 6 weeks.

So it is good for our conscience and we feel less guilty 8)

--- End quote ---
Here is what happens to the content of yellow bins across Europe
It is not as bad as I expected. Energy usage seems to be widespread


--- End quote ---
Take that graph with a huge grain of salt: most likely, it counts as “recycling” to collect it for recycling and sending it abroad to be recycled (where it may not actually be recycled). What makes me suspect this is Germany’s positive appearance on this graph, while other sources I’ve seen (in various German-made documentaries) show that while recycling rates are high (in the sense of collection), huge amounts of plastics are not processed within Germany, but sent to Eastern Europe, which means they’re likely not actually getting recycled at all.

Switzerland is a huge outlier in this regard: aside from having very high rates of plastic collection (82%-95%, depending on who you ask), nearly all collected plastic is also recycled within Switzerland, ensuring it’s actually recycled. (For PET, none is exported at all, apparently.) Since Switzerland does export plastic abroad (to Germany, mostly), that must be the non-PET plastics.

--- End quote ---
True and correlation doesn't mean causation. It might be that governments which invest in recycling, also have laws restricting landfill.

strawberry:

--- Quote from: langwadt on August 03, 2022, 12:39:27 pm ---reusing plastic cost a lot of resourcesfor an inferior end product, glass and metal are recycled because it saves resources and the end product is just as good

--- End quote ---
pumped raw oil is basically : water, dirt, oil.
oil tankers burn crude oil because it is cheapest fuel ~3000m^3.

1: 1# oil refinery - product factory - garbage collection - garbage burning plant - garbage dump site - 2# oil refinery - product factory - garbage collection - garbage burning plant - garbage dump site
2: 1# oil refinery - product factory - garbage collection - recycle factory - 2# product factory - garbage collection - recycle factory ...     - garbage collection - garbage burning plant - garbage dump site

single use product must be top quality even when consumer cant tell difference

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