Is is compulsory to print and then post the proposal or can it be sent by email?

Is the proposal for sales? You don't want to turn off potential customers with spam in email. Is this for real or is it a school project?

It is a real recycle project

Please tell me more.

It is a housing project in which we want to incorporate a recycle system that will ensure that the neighbourhood is kept clean and resources such as rainwater are collected and stored for later use. ~The proposal is a means for attaining funds. Does the document need to the bound or can it be sent by email?

Since it is that targeted, email should be fine. Be sure to make a good heading/subject line so the email doesn't get trashed.