How to differentiate biodegradable plates from others?

How to differentiate biodegradable plates from others? Another aspect of the erstwhile green Indian life was the practice of using disposable plates made from leaves. In an organic spice plantation farm in Goa recently, we were served wholesome Saraswat food in beautiful, sturdy plates made of dried betel leaves stitched together. One can wash and reuse them. My husband recalls his grandmother making instant plates using the leaves of the badam tree. A guest would pop in for a meal suddenly, as would happen those days, and she would take a few dried leaves stocked in the kitchen, deftly use a few twigs to hold them together, and voila, a nice biodegradable plates from http://www.biodegradabletableware.com.cn/ProductsType/disposable-plates-biodegradable-1.htm was ready. Yet there are also some non-biodegradable plates booming with life,then how shall we differentiate biodegradable plates from others?