Used (extruded) 3Doodler plastic cannot be reinserted into the pen.
ABS plastic can be recycled. It is classified under recycling number 7 and is often turned into plastic lumber and other custom-made products.
The most ardently eco-friendly 3Doodlers may want to opt for PLA, which is biodegradable (and made from corn!), as their plastic of choice.
Posted in: Plastic