Last year I made this plastic extruder to try and make growing media from recycled bottles. Even though I didn't get the desired results, it has tickled the fancy of a few niche groups. This article was published in a German trade magazine that deals with plastics.
It's all in German...they said the article may be picked up by their English counterpart later this year. I have no idea what it says...for all I know, they said I was a raving lunatic!