I'd like to know a lot more about the energy conversion process, too. Plastics are so varied in structure that there are most likely several different methods for conversion. I know that pyrolysis is one such method, but I suspect that it also comes in several flavors.
I would really like to see the process for converting thermoset plastics into any sort of usable fuel base, or fuel. It would be totally amazing to see it done. The best idea that I have seen was to form the waste into landscaping timbers. Unfortunately the plan I saw was discovered to be a fraud. But if the waste stream is sorted to provide a stream of at least 80% thermoplastic material, then it certainly ought to be convertible into some useful material. Converting the plastic back into it's more basic constituants would definitely be a lot more complex process. The best thing would be if the conversion could be done directly with solar enegy, such as melting the regrind in a large ssolar furness, and using the excess heat to drive the extrusion process. IT might also be possible to use the material as pavement for sidewalks and roads, if a gravel filler could be added. Possibly subtitute the molten plastic for the bitumen in asphalt. OF course, it is also possible that I have overlooked something in proposing this choice.
“Plastics make up only 9.5 to 17 percent of each state's municipal solid wastes”
Ann, Plastics are very much hazardous to the nature because it cannot be decomposes easily. If there is any mechanism, to recycle these plastic wastes to energy, it’s a great gift to the nature. It can cater our energy requirements and at the same time it’s saving the nature from hazardous elements. But am not sure about the bie- product from these plastic wastes, once the energy is produced.
I certainly don't know enough to contribute anything meaningful to this discussion but I will say that both reading the original article and the replies has been very interesting and educational. Like so many other subjects in our rather complicated lives, this one has lots of complexities. The problems are not simple and neither are the solutions! At least some people and organizations are making attempts to solve them.
It is a natural reaction to assume that reusing or recycling of plastics is the most efficient method of utilizing plastics. Unfortunately we cannot forget that it requires sorting cleaning and separating of different products. Take for example scraps of composite decking. It is a mixture of wood dust and plastic. Try to separate the two and you will end up with a very expensive plastic. Recovery of plastics from recycling programs costs at least two times as much as making them from natural gas that we merrily are burning in some electric generation plants. Burn the plastics and use the gas for making new and clean plastics and everybody will be happy including tree huggers.
Ivan, I think you make a good point. The study's authors note that reuse and recycling are still the most desirable options for dealing with previously used plastics and other "waste" materials. Recycling comes right after waste reduction at the top of the EEC's waste management pyramid shown in Figure 2 (page 7). For plastics that are not reused or recycled, though, and end up in landfills, the aim of this study was to calculate their energy value and identify ways to recover their energy content.
I question whether burning discarded plastics is really the best way of using them. It seems to me that even though there are BTU's locked in the plastic wouldn't it be better to reuse it in a form closer to its state? plastics are long chain polymers and it would seemt he value there is in reusing it as plastic and not just as burning it and releasing the C into the air as CO2 and whatever else the plastic might contain then becomes a potential pollutant.
In short I am suggesting we reuse plastic as plastic and not just burn it. We spent some energy and effort into making it into plastic and surely there is a way to reuse that instead of burning it which in fact totally destroys the "plastic" aspects and make sit unusable for anything else.
Converting it back into oil would seem to require more processing and energy on top of the original effort that turned oil into plastic.
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