Advantage: The materials in the pen are non-renewable, so recycling them conserves resources (crude oil and metal ores).
Alternatively you could talk about it reducing the use of landfill and using less energy to recycle the pen.
Disadvantage: Its difficult to separate the materials of the pen since its made from different polymers and alloys. Could alternatively say that separating them could be costly.
Also could suggest that not all the materials can be recycled.