At US military training facilities, spent shell casings are scattered across proving grounds, many buried several inches below ground. What if they were biodegradable and contained seeds that would sprout into beneficial plants over time? It may sound a bit utopian, but the US Department of Defense has just released a call to arms of sorts asking for someone to come up with just that: "biodegradable composites with embedded seeds for training ammunition." The department cites several reasons for why this would prove helpful, including for environmental purposes (regular bullets rust and pollute not only soil but groundwater) and safety reasons (a farmer tilling a former live-fire range could run into trouble).
The pollutant issue may seem small when measured by the shot, but it builds up, reports Popular Mechanics. So the US Army Corps of Engineers' Cold Regions Research and Engineering Laboratory has created and tested seeds for a biodegradable composite, engineering them to sprout months after being embedded in the ground, per Live Science. The ammo involved covers everything from tank shells to carbine bullets, notes Popular Mechanics. Once biodegradable versions have been worked up, a prototype will be made and a way for them to be mass-manufactured determined. The ammo in the project is meant only for training, not combat, and the Army says animals should be able to eat the resulting plants without suffering any ill consequences. (The Navy can't afford these bullets.)