Which urn material is suitable for scattering ashes in nature?

It has been challenging to let go of my baby. My heart has been wrenched for what feels like forever, but I think the time has come for me to let my angel be free. I feel that releasing him will bring me more comfort, so I have been searching for urns to scatter my boy's ashes. I wanted to return his ashes to the earth, so I thought of scattering them in a forest. I just don't know what material would be suitable for transporting cremains and biodegradable.