The time it takes for a biodegradable urn to break down can vary from a few minutes to a few years depending on the material it is made of and where the urn is being placed -- such as ground burial or scattering at sea. The Oceane Sand Footprints Urn, for example, is made of gelatin and sand and will dissolve within days -- possibly hours -- when placed in water but could take 2-3 months to dissolve if placed in the ground. The very popular Journey Biodegradable Urn series is made of paper. Families appreciate that it floats briefly, then sinks as the paper absorbs the water, and finally biodegrades within a day or less.