Recently, I was privileged to participate on a judging panel in an international printing contest. One of the categories was environmental printing. In that category, an entrant had submitted a very interesting postcard made of 100% recycled paper and containing seeds in the paper fiber, enabling the postcard to be planted.
The message was environmental, and the use of 100% recycled stock and the ability to plant the resulting postcard and return it to the earth made a strong environmental statement. But the paper was fragile, so the postcard had to be mailed in a clear envelope to protect it during the mailing process.