Summary: the biodegradable plastic shell breaks down and the remains provide nutrients to a sapling planted right above it.
My summary is the gist of this article; as usual, read it if you wish to become informed about its concept, etc.,.
Links in the article expand the concept, to include a uTube vid on the designers website.
Apparently different "style" pods have been designed (at least looking at the outside of one), and the one in my embedded image is just one
This uTube URL (1:23 run time) illustrates the details; it more clearly illustrates that the pod is buried below ground and along with other pods
ideally creates a forest (and apparently one without tombstones in the vid). https://www.youtube.com/watch?v=fHkZZNlxLzo
JackInCT has attached this image. Click the image to enlarge it: