It also means that it could potentially lead to polluting the soil and water, plus it could also be mistakenly eaten by animals. However the Department of Defense has an idea in which they are looking to create a bullet that could eventually turn into plants (via Gizmodo UK). “Proving grounds and battle grounds have no clear way of finding and eliminating these training projectiles, cartridge cases and sabot petals, especially those that are buried several feet in the ground. Some of these rounds might have the potential corrode and pollute the soil and nearby water.”
How this works is that in addition to packing gunpowder, these bullets will also be biodegradable and also contain a specially engineered seed that will grow into a plant. This plant should be able to remove the contaminants in the soil left behind by the bullet, as well as be safe for consumption by animals. It is an interesting proposal and idea, but what exactly will come of it remains to be seen.