How to erase a PowerBook G4 so I can recycle it?

See:

What to do before you sell, give away, or trade in your Mac

Hi,

Which exact PowerBook G4 model?

https://everymac.com/systems/apple/powerbook_g4/index-powerbook-g4.html

Do you have any system discs for the PowerBook G4 in question?

If you do not have access to a bootable system or tools disc, it would be possible to open the computer and remove the internal hard drive. The removed hard drive could either be kept, or destroyed (for example, using a hammer or drill), or connected to a USB universal bare drive adapter (one example at https://eshop.macsales.com/item/NewerTech/U3NV2SPATA/) and then erased via another Mac (or a PC).