Dave Hakkens developed a great set of open sourced DIY machines for recycling plastic. There are several machines including a 3d printing filament extruder. Every device is well documented with manuals, open sourced and uses simple and easy to find components. There is a shredder, extruder, injection molding machine and compression forming chamber.
here is the promotional video:
You can learn something about many types of plastics, which are everywhere! Like difference between thermoplastics and thermoset plastics:
3D printing filament extruder demo:
Here is a video explaining how you build it:
Here are some things you can make with recycled plastic, ranging from lamp shades to building blocs:
Project homepage where you can learn how to build each machine and about the plastics as a material:
You can find all the documentation on:
Now, recycling plastics is great idea and useful skill to have, but will it decrease the usage of plastics in general? I do not have the data, but i have strong doubts that it will not. There is a something called Jevons paradox that notes that the more efficiently we use a resource, the rate of a consumption of that resource will increase. Think about it ....
BTW: Dave is a very cool guy, do check his youtube channel: https://youtube.com/user/hakopdetak
Here is his pro-tip video on how to get organized as a DIY / Hacker / Maker guy with industrial plastic crates: