“Method of Biowaste Removal from Isolated Dwelling Compartment of Military Facility and Device for its Implementation” - the Poo Canon!
Semenov’s diagram shows how it works. A crewman  fires the tank’s main armament  while simultaneously pooing into a special shell  which can be loaded into the breach  and fired at enemy positions where it will explode and spatter soldiers with poo, thus undermining their morale.
Luckily for all of us, this Weapon of Mess Destruction never made it from the Patent Office to the battlefield. It did make me wonder, though: do tanks have toilets?
A bit of Googling revealed that there’s no room in a tank for a toilet. According to veteran tanker and author Bacil Donovan Warren, writing on Quora:
“No tank that I’m aware of has a proper toilet, per se. Soldiers still need to go, of course, so field-expedient methods are used. In the field, we usually had access to either engineer-made latrine facilities, or proper toilets depending on where we were. During Desert Storm, when we had to go we would dig a field-expedient single-use latrine, or in the worst circumstance use empty ammo cans or water bottles.”