Cremation urns made from metal and stone are best for burying ashes, because these materials are strong enough to resist collapsing under the weight and pressure of soil. Urns made of wood may still be buried if the urn is enclosed in an urn vault designed for burial, but metal and stone urns are preferable because wooden urns may degrade over time from moisture. Biodegradable urns are also ideal for burial, because they are designed to break down in soil and water in an eco-friendly manner. You should decide if you prefer to bury an urn that will last for decades or centuries, or an urn that will break down and leave no environmental impact.