It seems to me that a natural, dignified, and economic burial would consist of burying a body (possibly pasteurized by a high temperature soak but otherwise unprocessed) in protected forest areas, with a new tree planted over each gravesite. Longlived trees should be selected and each might be marked with a plaque with a suitable inscription honoring the person buried there. The plaque should be chosen to endure for 50 or 60 years, which would probably serve to identify the site for as long as anyone would desire to visit it.
The body would, obviously, provide nourishment for the tree so that each tree would represent the person in an emotionally beneficial manner while serving a useful purpose in carbon sequestration, air filtering, and terrain stabilization. A fee could be charged which would help fund an annuity sufficient to maintain the forest.
I see no reason to think that a tree would be a less fitting and satisfying memorial for a person than the currently fashionable block of stone. It would symbolize a form of continuing life while the stone is some poor inert monument already millions of years old.