Hi Sia,
This is more or less how the master data are populated.
http://scn.sap.com/docs/DOC-58113
And answering your questions:
> What is the risk if waste code is not assigned to any material and the subsequent process may require manual entry of waste material or entry with in partners?
The waste code must be present in the disposal document, usually is inherited from waste approval. A disposal document is created with one or several entry document
> What is the process for Assignment of the transporter or disposers, which are allowed to deal with certain waste?
First, the disposer is the most relevant partner, to be able to send a waste to a disposer you must have a waste approval accepted by an authority, in this document is present the company as producer, the disposer, and the waste with a waste code.
From top to bottom, if you know which waste approval there are in your company, then you know which disposal channel are being used.
Second, the transporter, it has to be present in the disposal document, it can be enter directly in the disposal document, unless you need to check that if it is authorized to transport of the waste.
Regards.
JCD