Theoretically, almost all 3D Printed Objects can be recycled, but practically recycling them is not that straight forward.
Currently, the most commonly used materials for 3D Printers are ABS (Acrylonitrile Butadiene Styrene) and PLA (Polylactic Acid). Both of these materials are considered as #7 Plastics.
Among these two:
PLA is a biodegradable thermoplastic made from renewable resources like cornstarch or sugarcane,
ABS is a biodegradable thermoplastic made from petroleum products.